780 cmr 18.00 foundations and retaining walls · foundations and retaining walls 8/22/08 (effective...

8/22/08 (Effective 9/1/08) 780 CMR - Seventh Edition 429

780 CMR 18.00FOUNDATIONS AND RETAINING WALLS

780 CMR 1801.0 GENERAL

1801.1 Scope. The provisions of 780 CMR 18.00shall govern the design and construction offoundations and retaining walls.

1801.2 Design. Foundations shall be designed toprovide adequate load bearing capacity whilelimiting settlement, heave and lateral movement totolerable levels. Allowable bearing pressures,allowable stresses and design formulas provided in780 CMR 18.00 shall be used with the allowablestress design load combinations specified in780 CMR 1605.3. The quality and design ofstructural materials shall conform to therequirements specified in 780 CMR 16.00, 19.00,21.00, 22.00 and 23.00. Excavations and fills shallalso comply with 780 CMR 33.00.

1801.3 Foundation Types Not Covered by CodeProvisions. Types of foundations not specificallycovered by the provisions of 780 CMR, and groundmodification treatments to improve soils withinadequate load bearing capacity or settlementcharacteristics, may be permitted subject to approvalby the building official. A report shall be submittedto the building official that identifies the foundationas a type not covered by existing code provisions,and contains sufficient data and analyses tosubstantiate the adequacy of the proposed found-ation. The report shall be prepared by a registereddesign professional who is knowledgeable in thedesign of the proposed type of foundation or groundmodification. The building official may require thatan independent peer review be performed to evaluatethe adequacy of the proposed design.

1801.4 Qualifications of Registered DesignProfessional. Where the services of a registereddesign professional are required by the provisions of780 CMR 18.00, the registered design professionalshall be knowledgeable in the field of geotechnicalengineering and shall be qualified by appropriatetraining and experience to provide the specificservices required by the code provisions.

780 CMR 1802.0 FOUNDATION AND

SOILS INVESTIGATIONS

1802.1 General. Foundation and soilsinvestigations shall be conducted in conformancewith 780 CMR 1802.2 through 1802.6. The scope ofthe investigation shall be determined by a registereddesign professional. The registered design profes-sional shall oversee the performance of theinvestigation and prepare a report containing theresults of the investigation.

1802.2 Where Required. Foundation and soilinvestigations shall be required for all newstructures, and for alterations of existing structuresthat result in increased foundation loads or decreasedload resistance, except as noted below. Where thereis sufficient local experience that indicatessatisfactory performance of similar structures in thevicinity of the proposed structure, the followingtypes of structures do not require a foundation andsoils investigation, unless specifically required bythe building official:

1. one- and two-family dwellings and theiraccessory buildings;2. unoccupied structures that do not pose asignificant risk to public safety in the event offailure; or3. structures used for agricultural purposes.

1802.3 Soil and Rock Classification. Classifica-tion of soil materials shall be done in accordancewith ASTM D 2487. Refer to commentary in780 CMR 120.R for guidelines regardingdetermination of soil and rock Material Classes andConsistency in Place for use with Table 1804.3 andrelated provisions.

1802.4 Investigation. The investigation shallconsist of subsurface explorations and engineeringstudies. The borings, test pits or other subsurfaceexplorations shall be adequate in number and depthand so located to accurately define the nature of thesubsurface materials necessary for the support of thestructure. When it is proposed to support thestructure directly on bedrock, the building officialshall require core borings to be made into the rock;or shall require adequate information from othersources to define the nature and quality of thebedrock. The results of previous subsurface explora-tions may be utilized where deemed to be adequateby the registered design professional. Engineeringstudies shall be made as necessary to identifysuitable bearing strata and evaluate soil strength,compressibility, bearing capacity, settlement,liquefaction potential, lateral earth pressures, slopestability and impacts of groundwater.

1802.4.1 Groundwater Table. The investigationshall determine the location of the groundwaterlevel relative to the proposed structures andevaluate the potential groundwater impacts. Theevaluation shall consider both the impacts ofgroundwater on the structures and the potentialimpacts of the structures on the local groundwaterlevels.

780 CMR: STATE BOARD OF BUILDING REGULATIONS AND STANDARDS

THE MASSACHUSETTS STATE BUILDING CODE

430 780 CMR - Seventh Edition 8/22/08 (Effective 9/1/08)

1802.4.2 Pile and Pier Foundations. Where pieror pile foundations are used, the investigationshall include the following:

1. Recommended pier or pile types,dimensions and installed capacities.2. Recommended center-to-center spacing ofpiles or piers.3. Driving criteria.4. Installation procedures.5. Field inspection and reporting proced-ures(to include procedures for verification of theinstalled bearing capacity where required).6. Pier or pile load test requirements.7. Durability of pier or pile materials.8. Designation of bearing stratum or strata.9. Reductions for group action, wherenecessary.10. Evaluation of conditions that mightpromote deterioration of pile or pier founda-tions, in order to satisfy the requirements of780 CMR 1808.2.17.

1802.4.3 Rock Foundations. Where sub-surfaceexplorations at the project site indicate variationsor doubtful characteristics in the structure of therock upon which foundations are to beconstructed, a sufficient number of borings shallbe made to a depth of not less than ten feet belowthe level of the foundations to provide assuranceof the soundness of the foundation stratum and itsbearing capacity.

1802.4.4 Liquefaction Potential. Where thefoundation investigation indicates subsoils ofMaterial Classes 8 or 9, as defined in Table1804.3, the investigation shall include anevaluation of the potential for earthquake-inducedliquefaction in accordance with 780 CMR 1804.6.

1802.5 Borings, Sampling and Testing. The scopeof the subsurface exploration, including the numberand types of borings, soundings or test pits, theequipment used to drill and sample, the in-situtesting equipment and the laboratory testingprogram, shall be determined by a registered designprofessional. The boring and sampling procedureand apparatus shall be in accordance with generallyaccepted engineering practice. The registered designprofessional shall have a qualified representative onthe site during the subsurface exploration and shallperform suitable checks to verify the adequacy ofinformation obtained from others.

1802.6 Reports. The design bearing strata andload-bearing capacity shall be shown on theconstruction document. The written report of theinvestigation shall include, but need not be limitedto, the following information:

1. A plot showing the locations of the subsurfaceexplorations.2. Logs or other suitable records of thesubsurface explorations.

3. An interpretative description of the subsurfaceprofile.4. Elevation and/or depth of the water table, ifencountered, and an evaluation of groundwaterimpacts in accordance with 780 CMR 1802.4.1.5. Results of in-situ testing and/or laboratorytesting, if performed.6. Recommendations for foundation type anddesign criteria.7. Evaluation of earthquake liquefactionpotential8. Expected total and differential settlement.9. Pile and pier foundation information inaccordance with 780 CMR 1802.4.210. Compacted fill material properties andtesting in accordance with 780 CMR 1803.5.11. Lateral earth pressures on foundation wallsand retaining walls.

780 CMR 1803.0 EXCAVATION,

GRADING AND FILL

1803.1 Excavations near Footings or Founda-tions. Excavations for any purpose shall not removevertical or lateral support from any footing orfoundation without first underpinning or protectingthe footing or foundation against settlement or lateraltranslation.

1803.2 Placement of Fill Adjacent to Structures.Fill placed adjacent to structures shall be a suitablematerial placed and compacted in a manner that doesnot damage the foundation or the waterproofing ordamp-proofing material.

1803.3 Site Grading. The ground immediatelyadjacent to the foundation shall be sloped away fromthe building at a slope of not less than one unitvertical in 20 units horizontal (5% slope) for aminimum distance of ten feet (3048 mm) measuredperpendicular to the face of the wall or an alternatemethod of diverting water away from the foundationshall be used. The procedure used to establish thefinal ground level adjacent to the foundation shallaccount for potential settlement of the backfill.

1803.4 Compacted Structural Fill Material.Where footings or structures will bear on compactedfill material, the compacted fill shall comply with theprovisions of the report prepared by a registereddesign professional in accordance with 780 CMR1802.6. The report shall contain the following:

1. Specifications for the preparation of the siteprior to placement of compacted fill material.2. Specifications for material to be used ascompacted fill.3. Lateral and vertical limits of the compactedfill.4. Type and size of compaction equipment andcompaction procedures.5. Maximum allowable thickness of each lift ofcompacted fill material.


FOUNDATIONS AND RETAINING WALLS


6. Test method to be used to determine themaximum dry density and optimum moisturecontent of the material to be used as compactedfill.7. Field test methods for determining the in-placedry density of the compacted fill.8. Minimum acceptable in-place dry densityexpressed as a percentage of the maximum drydensity determined in accordance with Item 6, andthe number and frequency of field tests required todetermine compliance with this criterion.9. Alternative compaction control criteria formaterials than cannot be effectively tested by themethods described in 780 CMR 1803.4, Items 6.,7., and 8.

Exception: Compacted fill material less than12 inches (305 mm) in total thickness does notrequire a soils investigation report, provided ithas been compacted to a minimum of 95%Modified Proctor in accordance with ASTM D1557. The compaction shall be verified by aqualified inspector approved by the buildingofficial.

1803.5 Field Control. The building official willrequire that a registered design professional or hisrepresentative be on the project at all times while fillis being placed and compacted. The representativeshall make an accurate record of the types ofmaterials used, including grain-size curves, thicknessof lifts, densities, percent compaction, type ofcompacting equipment and number of coverages, theuse of water and other pertinent data.

1803.6 Controlled Low-strength Material(CLSM). Controlled low strength material (CLSM)is defined as a flowable cementitious fill materialmeeting the requirements of ACI 229R-94 that isplaced without compaction. Where footings orstructures will bear on CLSM, the CLSM shallcomply with the provisions of a report prepared by aregistered design professional, which shall containthe following:

1. Specifications for the preparation of the siteprior to placement of the CLSM.2. Specifications for the CLSM.3. Laboratory or field test method(s) to be usedto determine the compressive strength or bearingcapacity of the CLSM.4. Test methods for determining the acceptanceof the CLSM in the field.5. Number and frequency of field tests requiredto determine compliance with 780 CMR 1803.6,Item 4.

780 CMR 1804.0 ALLOWABLE

LOAD-BEARING VALUES

1804.1 Satisfactory Foundation Materials.Foundations for structures shall be supported onnatural strata of rock, gravel, sand, inorganic silt,

inorganic clay, or combination of these materialsprovided that they do not overlie an appreciableamount of peat, organic silt, soft clay or otherobjectionable materials. Compacted fills and CLSMmay be used for support of foundations, whendesigned and monitored by a registered designprofessional. Other conditions of unsatisfactorybearing materials which are improved in accordancewith the recommendations of, and monitored by, aregistered design professional, may be accepted bythe building official.

1804.2 Protection of Bearing Strata. The bearingstrata shall be adequately protected againstdisturbance. If the bearing materials are disturbedfrom any cause, for example, by the inward orupward flow of water, by freezing or by constructionactivities, the extent of the disturbance shall beevaluated by a registered design professional andappropriate remedial measures shall be taken.

1804.3 Presumptive Load Bearing Values. Themaximum allowable pressure on the bearing stratasupporting spread footings, mats and piers shall notexceed the values specified in Table 1804.3 or themaximum allowable pressure shall be determined byload tests conducted in the field or as otherwiseprovided herein. Presumptive load-bearing valuesshall apply to all materials with similar physicalcharacteristics. Where the bearing strata are under-lain by weaker materials, the vertical pressure on theunderlying materials shall be checked in accordancewith 780 CMR 1804.7. Higher allowable bearingpressures may used if substantiated by the results ofinvestigations, analyses or testing prepared by aregistered design professional and approved by thebuilding official.

1804.3.1 Net Bearing Pressure. For the purposesof 780 CMR 1804.3, the applied bearing pressureshall be the net bearing pressure computed usingthe allowable stress design load combinationsspecified in 780 CMR 1605.3, including theweight of the foundation and of any immediatelyoverlying material, minus the pressure applied bythe column of soil, including the water in itsvoids, that extends from the lowest immediatelyadjacent surface of the soil to the bottom of thefooting, pier or mat.

1804.3.2 Classification of Bearing Materials.The terms used in 780 CMR 1804 shall beinterpreted in accordance with generally acceptedengineering nomenclature. Refer to commentaryin 780 CMR 120.R for guidelines regarding soiland rock classification and description.

1804.3.3 Compacted Fill. Materials fromClasses 6 through 8, Table 1804.3, or densegraded crushed stone, which contain no plasticfines, shall have a maximum allowable bearingpressure of up to five tons per square foot whencompacted to 95% or greater of the maximum drydensity as determined by ASTM D1557 listed in.




For compacted fills which do not meet the abovecriteria or materials which cannot be tested asa b o v e ,

a registered design professional shall be engagedto provide recommendations for compaction andmaximum allowable design bearing pressures.

TABLE 1804.3 ALLOWABLE BEARING PRESSURES FOR FOUNDATION MATERIALS

MaterialClass

Description Notes Consistency in Place1

Allowable NetBearing Pressure

(tons/ft )2

1aMassive bedrock:Granite, diorite gabbro, basalt, gneiss

3 Hard, sound rock, minor jointing100

1b Quartzite, well cemented conglomerate 3 Hard, sound rock moderate jointing 60

2 Foliated bedrock: slate, schist 3 Medium hard rock, minor jointing 40

3Sedimentary bedrock: cementation shale,siltstone, sandstone, limestone, dolomite,conglomerate

3, 4 Soft rock, moderate jointing 20

4Weakly cemented sedimentary bedrock:compaction shale or other similar rock insound condition

3 Very soft rock 10

5Weathered bedrock: any of the aboveexcept shale.

3, 5Very soft rock, weathered and/ormajor jointing and fracturing

8

6Slightly cemented sand and/or gravel,glacial till (basal or lodgment), hardpan

7,8 Very dense 10

7Gravel, widely graded sand and gravel;and granular ablation till

6, 7, 8

Very denseDenseMedium denseLooseVery loose

8642Note 11

8Sands and non-plastic silty sands withlittle or no gravel (except for Class 9materials)

6, 7, 8,9

DenseMedium denseLooseVery loose

431Note 11

9Fine sand, silty fine sand, and non-plasticinorganic silt

6, 7, 9

DenseMedium denseLooseVery loose

321Note 11

10Inorganic sandy or silty clay, clayeysand, clayey silt, clay, or varved clay;low to high plasticity

5, 6, 10

HardStiffMediumSoft

421Note 11

11Organic soils: peat, organic silt, organicclay

11 Note 11

Notes for Table 1804.3:1. Refer to commentary in 780 CMR 120.R regarding typical index test values that may be helpful as

guides for evaluation of consistency in place.2. Refer to 780 CMR 1804.3.1 for the definition of net bearing pressure.3. The allowable bearing pressures may be increased by an amount equal to 10% for each foot of depth

below the surface of sound rock; however, the increase shall not exceed two times the value given inthe table.

4. For limestone and dolomite, the bearing pressures given are acceptable only if an exploration programperformed under the direction of a registered design professional demonstrates that there are no cavitieswithin the zone of influence of the foundations. If cavities exist, a special study of the foundationconditions is required.

5. Weathered shale and/or weathered compaction shale shall be included in Material Class 10. Otherhighly weathered rocks and/or residual soils shall be treated as soil under the appropriate description inMaterial Classes 6 to 10. Where the transition between residual soil and bedrock is gradual, a registereddesign professional shall make a judgment as to the appropriate bearing pressure.




6. Settlement analyses in accordance with 780 CMR 1804.8 should be performed if the ability of a givenstructure to tolerate settlements is in question, particularly for, but not limited to, soft or very soft claysand silts and loose granular materials.

7. Allowable bearing pressures may be increased by an amount equal to 5% for each foot of depth of thebearing area below the minimum required in 780 CMR 1805.2; however, the bearing pressure shall notexceed two times the value given in the table. For foundation bearing areas having a least lateraldimension smaller than three feet, the allowable bearing pressure shall be a of the tabulated value timesthe least dimension in feet.

8. Refer to 780 CMR 1804.3.3 when these materials are used as compacted fills.9. These materials are subject to the provisions in 780 CMR 1804.6 (Liquefaction).10. Alternatively, the allowable bearing pressure may be taken as 1.5 times the peak unconfined

compressive strength of undisturbed samples for square and round footings or 1.25 times that strengthfor footings with length to width ratio of four or greater. For intermediate cases, interpolation may beused.

11. A registered design professional shall be engaged to provide recommendations for these special cases.Direct bearing on organic soils is not permitted. Organic soils are allowed under foundations for thosecases defined in 780 CMR 1804.4.2 (Preloaded materials).

1804.4 Lightweight Structures. One-storystructures without masonry walls and not exceeding800 square feet in area may be founded on a layer ofsatisfactory bearing material not less than three feet(1 m) thick, which is underlain by highlycompressible material, provided that the stressesinduced in the unsatisfactory material by the live anddead loads of the structure, and the weight of anynew fill within or adjacent to the building area, willnot exceed 250 pounds per square foot (12 Kpa).

1804.4.1 Bearing Capacity for LightweightStructures. Lightweight structures and accesso-ry structures, such as garages and sheds, may befounded on normally unacceptable bearing strata,provided such material is determined by aregistered design professional as being satisfactoryfor the intended use.

1804.4.2 Preloaded Materials. The buildingofficial may allow the use of certain otherwiseunsatisfactory natural soils and uncompacted fillsfor support of one-story structures after thesematerials have been preloaded to effective stressesnot less than 150% of the effective stresses whichwill be induced by the live and dead loads of thestructure and any additional fill materials. Thepreloading shall be conducted under the directionof a registered design professional who shallsubmit a report documenting that adequateconsolidation of the material was achieved priorto removal of the preload.

1804.5 Dynamic Loading. For load combinationsthat include short duration dynamic loading, theallowable load bearing value of foundations may beincreased based on consideration of both theduration of the loading and the dynamic properties ofthe soil if substantiated by the results ofinvestigations, analyses or testing prepared by aregistered design professional and approved by thebuilding official.

1804.6 Liquefaction.

1. The potential for liquefaction induced by the

design earthquake in saturated clean to siltymedium to fine sands (Soil Classes 8 and 9 inTable 1804.3) shall be evaluated on the basis ofFigures 1804.6(a) through (c) for cases wherelateral sliding cannot occur. Figure 1804.6(a)shall be used if the Standard Penetration Testblowcounts, N (blows per foot), were determinedusing the standard 140-pound donut drop weight,or if the type of hammer is not known. Figures1804.6(b) and (c) shall be used only for caseswhere the specific type of hammer (safety hammeror automatic hammer) is known to have beenused. Figures 1804.6(b) and (c) reflect the greaterenergy efficiency with these two specific types ofhammers. Hammer type shall be as described inASTM Standard Method D6066. N-values to beused in these figures are uncorrected field values.2. Figures 1804.6(a) through (c) are intended tobe used as a screening tool for Site Classes Athrough D, and are based on a rock spectral rock

D1acceleration, S = 0.077, a soil amplificationfactor, Fv = 2.4 for Site Class D and a factor ofsafety of 1.1.3. If the standard penetration resistances, N, inall strata of medium to fine sand lie above theapplicable curve in Figure 1804.6(a) through (c),the sands at the site shall be considered notsusceptible to liquefaction. Liquefaction below adepth of 60 ft (18m) from final grade need not beconsidered for level ground. For pressure-injectedfootings, the ten-foot (3m) thickness of soilimmediately below the bottom of the driven shaftshall be considered not susceptible to liquefaction.4. Compacted granular fills shall be considerednot susceptible to liquefaction provided they aresystematically compacted to at least 93% of themaximum dry density determined in accordancewith ASTM Standard Method D1557, or to arelative density of at least 60% in the case ofgranular soils having less than 10% by weightmaterial passing the No. 200 U.S. sieve.5. Soils identified in 780 CMR 1804.6.1 that donot meet the criteria in 780 CMR 1804.6.3 and




1804.6.4 shall be considered susceptible toliquefaction. Appropriate studies, analyses anddesigns shall be made by a registered designprofessional to determine that the structural loadscan be safely supported. Such studies, analyses anddesigns might include the following:

a. Investigations to establish that the soils atthe site are not subject to liquefaction duringthe design earthquake, orb. Design of foundations that will not faileither by loss of bearing capacity or excessivesettlement or lateral deflection if liquefactionoccurs, orc. Replacement or densification of the poten-

tially liquefiable soils such that liquefactionwill not occur.

6. For sites underlain by saturated sands wherelateral sliding (slope instability) may occur,studies by the registered design professional shallbe made to establish the safety against slidingduring the design earthquake.7. For sites underlain by saturated silty sands andinorganic non-plastic silts, with standardpenetration resistances, N, lying below (to the leftof) the appropriate curve in Figure 1804.6(a)through (c), studies shall be made by theregistered design professional to determine thesusceptibility to liquefaction of these soils.

FIGURE 1804.6(A) LIQUEFACTION SUSCEPTIBILITY - DONUT HAMMER BLOW COUNTS




FIGURE 1804.6(B) LIQUEFACTION SUSCEPTIBILITY - SAFETY HAMMERBLOW COUNTS




FIGURE 1804.6(C) LIQUEFACTION SUSCEPTIBILITY - AUTOMATICHAMMER BLOW COUNTS

1804.7 Vertical Pressure. The computed verticalpressure at any level beneath a foundation shall notexceed the allowable bearing pressure for thematerial at that level. Computation of the verticalpressure in the bearing materials at any depth belowa foundation shall be made on the assumption thatthe load is spread uniformly at an angle of 30degrees with the vertical, or another suitable method.Interaction of adjacent foundations shall beconsidered in computation of the vertical pressure.

1804.8 Settlement Analysis. Whenever a structureis to be supported by medium or soft clay (materialsof Class 10) or other materials which may be subjectto settlement or consolidation, the settlements of thestructure and of neighboring structures due toconsolidation shall be given careful consideration,particularly if the subsurface material or the loadingis subject to significant variation. The effects of fillloads within the building area or fill and other loadsadjacent to the building shall be included in thesettlement analysis.

1804.9 Lateral Loads on Foundations. Wherefoundations are required to resist lateral loads, theallowable values of sliding friction, adhesion andpassive pressure for design shall be determined by a

registered design professional.

780 CMR 1805.0 FOOTINGS AND

MAT FOUNDATIONS

1805.1 General. Footings and mat foundationsshall be designed and constructed in accordance with780 CMR 1805.1 through 1805.12. Footings andmat foundations shall be supported on undisturbednatural soil, compacted fill, CLSM or bedrock inaccordance with 780 CMR 1804.0. Compacted fillmaterial shall be placed in accordance with780 CMR 1803.4 and CLSM shall be placed inaccordance with 780 CMR 1803.6.

1805.2 Minimum Depth. The bottom surface ofany foundation bearing on material other than soundbedrock shall be at least 18 inches (460 mm) belowthe adjacent ground surface or the top surface of afloor slab bearing directly on the soil immediatelyadjacent to the foundation.

1805.3 Slope of Bearing Surface. Where the slopeof the bearing surface exceeds one vertical in tenhorizontal, the bottom surface of the foundation shallbe stepped to prevent lateral sliding along thebearing surface, unless sufficient resistance againstsliding is provided by other means.




1805.4 Frost Protection. All foundations forbuildings and structures shall extend to a minimumof four feet (1.2m) below finished grade, unless:

1. Frost protection is provided in accordancewith ASCE-32;2. The foundation bears on sound bedrock; or3. The bearing materials below the foundation, toa depth of four feet below finished grade, are notsusceptible to frost heave.

Where the foundation grade is established at adepth of less than four feet below finished grade,appropriate supporting data prepared by a registereddesign professional shall be submitted to thebuilding official to substantiate the designfoundation grade.

Exception. Frost protection is not required forfree-standing buildings meeting all of thefollowing requirements:

1. Classified in Importance Category I (seeTable 1604.5);2. Area of 400 square feet (37 m2) or less; and3. Eave height of ten feet (3.1 m) or less.

1805.5 Isolated Footings. Footings on granular soilof Classes 7, 8 and 9 of Table 1804.3 and compactedfill shall be so located that the line drawn betweenthe lower edges of adjoining footings shall not havea steeper slope than 30 degrees (0.52 rad) with thehorizontal unless the material supporting the higherfooting is braced or retained or otherwise laterallysupported in an approved manner or a greater slopehas been established by a registered designprofessional.

1805.6 Foundations on or Adjacent to Slopes.Where buildings and structures are located on oradjacent to slopes the following impacts shall beaddressed in the design. Foundations located on aslope, or near the top edge of a slope, shall havesufficient embedment depth below the slope surfaceand/or setback from the edge of the slope to preventslope stability failure or detrimental settlement dueto the presence of the slope. Buildings andstructures located near the bottom of a slope shall besetback a sufficient distance from the slope toprovide protection from slope drainage, erosion,slope failure and falling debris.

1805.7 Design. Foundations shall be designed so asnot to exceed the allowable bearing pressuredetermined in accordance with 780 CMR 1804.3.The minimum width of the foundations shall not beless than 12 inches (305 mm). Footings shall bedesigned and constructed in accordance with780 CMR 1805.8 through 1805.12.

1805.7.1 Vibratory Loads. Where machineryoperations or other vibrations are transmittedthrough the foundation, consideration shall begiven in the foundation design to preventdetrimental disturbance of the soil.

1805.7.2 Eccentric Loads. Where foundationsare subject to eccentric loadings, the maximumpressure on the basis of straight-line distributionshall not exceed the allowable bearing pressure.

1805.8 Concrete Footings. The design, materialsand construction of concrete footings shall complywith 780 CMR 1805.8.1 through 1805.8.6 and theprovisions of 780 CMR 19.

1805.8.1 Concrete Strength. Concrete infootings shall have a specified compressive

cstrength (f’ ) of not less than 2,500 psi (17.2 MPa)at 28 days.

1805.8.2 Plain Concrete Footings. The edgethickness of plain concrete footings supportingwalls of other than light-frame construction shallnot be less than eight inches (203 mm) whereplaced on soil.

Exception. For plain concrete footingssupporting Group R-3 occupancies andbuildings less than two stories in height oflight- frame construction, the edge thickness ispermitted to be six inches (152 mm), providedthat the footing does not extend beyond adistance greater than the thickness of thefooting on either side of the supported wall.

1805.8.3 Placement of Concrete. Concretefootings shall not be placed through water unlessa tremie or other method approved by the buildingofficial is used. Where placed under or in thepresence of water, the concrete shall be depositedby approved means to ensure minimumsegregation of the mix and negligible turbulenceof the water.

1805.8.4 Protection of Concrete. Concretefootings shall be protected from freezing duringdepositing and for a period of not less than 5 daysthereafter. Water shall not be allowed to flowthrough the deposited concrete.1805.8.5 Forming of Concrete. Concretefootings are permitted to be cast against the earthwhere, in the opinion of the building official, soilconditions do not require forming. Where form-ing is required, forming shall be in accordancewith Chapter 6 of ACI 318.

1805.9 Masonry-unit Footings. The design,materials and construction of masonry-unit footingsshall comply with 780 CMR 1805.9.1 and 1805.9.2,and the provisions of 780 CMR 21.00.

1805.9.1 Dimensions. Masonry-unit footingsshall be laid in Type M or S mortar complyingwith 780 CMR 2103.7 and the depth shall not beless than twice the projection beyond the wall,pier or column. The width shall not be less thaneight inches (203 mm) wider than the wallsupported thereon.

1805.9.2 Offsets. The maximum offset of eachcourse in brick foundation walls stepped up from




the footings shall be 1½ inches (38 mm) where laidin single courses, and three inches (76 mm) wherelaid in double courses.

1805.10 Steel Grillage Footings. Grillage footingsof structural steel shapes shall be separated withapproved steel spacers and shall be entirely encasedin concrete with at least six inches (152 mm) on thebottom and at least four inches (102 mm) at all otherpoints. The spaces between the shapes shall becompletely filled with concrete or cement grout.

1805.11 Timber Footings. Timber footings arepermitted for buildings of Type V construction andas otherwise approved by the building official. Suchfootings shall be treated in accordance with AWPAC2 or C3. Treated timbers are not required whereplaced entirely below permanent water level, orwhere used as capping for wood piles that projectabove the water level over submerged or marshlands. The compressive stresses perpendicular tograin in untreated timber footings supported uponpiles shall not exceed 70% of the allowable stressesfor the species and grade of timber as specified in theAFPA NDS.

1805.12 Wood Foundations. Wood foundationsystems shall be designed and installed inaccordance with AFPA Technical Report No. 7.Lumber and plywood shall be treated in accordancewith AWPA C22 and shall be identified inaccordance with 780 CMR 2303.1.8.1.

1805.13 Seismic Requirements. See 780 CMR1910.0 for additional requirements for footings andfoundations of structures assigned to Seismic DesignCategories C and D. For structures assigned toSeismic Design Categories D, provisions of ACI318, Sections 21.8.1 to 21.8.3, shall apply when notin conflict with the provisions of 780 CMR 1805.0.Concrete shall have a specified compressive strengthof not less than 3,000 psi (20.68 MPa) at 28 days.

Exception. Group R or Group U Occupancies oflight-frame construction and two stories or less inheight are permitted to use concrete with aspecified compressive strength of not less than2,500 psi (17.2 MPa) at 28 days.

1805.14 Footing Seismic Ties. Where a structure isassigned to Seismic Design Category D inaccordance with 780 CMR 1616, individual spreadfootings founded on soil defined in 780 CMR1615.1.1 as Site Class E or F shall be interconnectedby ties. Ties shall be capable of carrying, in tensionor compression, a force equal to the product of the

DSlarger footing load times the seismic coefficient Sdivided by ten unless it is demonstrated thatequivalent restraint is provided by reinforcedconcrete beams within slabs on grade or reinforcedconcrete slabs on grade, by the lateral confinementprovided by competent soil or rock surrounding thefooting or by other approved means.

780 CMR 1806.0 FOUNDATION WALLS

AND RETAINING WALLS

1806.1 Definitions. The following definitions shallapply for the purposes of 780 CMR 1806.

FOUNDATION WALL. A wall extendingpartially or fully below grade, that supports verticalloads from walls, piers, columns or other structuralelements of a building or other structure, and mayalso support unbalanced lateral loads from soil,water or other materials adjacent to the wall.

RETAINING WALL. A wall or other retainingstructure or system designed to provide lateralsupport of soil, water or other materials, that doesnot provide vertical support for structural elementsof a building and has any portion of its exposed faceinclined steeper than one horizontal to one vertical.This definition shall include concrete walls, crib andbin walls, reinforced or mechanically stabilized earthsystems, anchored walls, soil nail walls, multi-tieredsystems, boulder walls, or other retaining structures.

Exception. The definition of Retaining Walldoes not include slope facings, armor or riprapplaced for the sole purpose of protection againstsurface erosion.

1806.2 Design Earth Pressures. The design earthpressures for foundation walls and retaining wallsshall be determined by a registered design profes-sional based on the data and recommendationsprovided in the foundation and soils investigationreport prepared in accordance with 780 CMR 1802.The design earth pressures shall account for thefollowing factors:

1. The nature of the native soil and backfillmaterial2. Drainage provisions and potential hydrostaticpressures3. The rigidity of the wall and its supports4. Pressures due to compaction of backfillmaterial5. Pressures due to surcharge loadings6. Seismic earth pressures

1806.3 Foundation Wall Design. Concrete andmasonry foundation walls shall be designed inaccordance with 780 CMR 1806.0 and 780 CMR19.00 or 21.00. Foundation walls for single levelbasements that are within the parameters of Tables1806.3(1) through 1806.3(4) may be designed andconstructed in accordance with 780 CMR 1806.3.1through 1806.3.5, if they meet the following criteria:

1. The wall is laterally supported at the top andbottom2. There is no net hydrostatic pressure on thewall3. There are no surcharge loadings4. The backfill adjacent to the wall is notsubjected to heavy compaction loads




1806.3.1 Foundation Wall Thickness. Theminimum thickness of concrete and masonryfoundation walls shall comply with 780 CMR1806.3.1.1 through 1806.3.1.3.

1806.3.1.1 Thickness Based on WallsSupported. The thickness of foundation wallsshall not be less than the thickness of the wallsupported, except that foundation walls of atleast eight-inch (203 mm) nominal width arepermitted to support brick-veneered frame

walls and ten-inch-wide (254 mm) cavity wallsprovided the requirements of 780 CMR1806.3.1.2 are met. Corbeling of masonry shallbe in accordance with 780 CMR 2104.2.Where an eight-inch (203 mm) wall iscorbeled, the top corbel shall be a full course ofheaders at least six inches (152 mm) in length,extending not higher than the bottom of thefloor framing.

TABLE 1806.3(1) PLAIN MASONRY AND PLAIN CONCRETE FOUNDATION WALLSa, b, c

PLAIN MASONRY

WALL

HEIGHT

(feet)

HEIGHT OF

UNBALANCED

BACKFILL (feet)

MINIMUM NOMINAL WALL THICKNESS (inches)

Soil classes and lateral soil load (psf per foot below natural grade)a

GW, GP, SW and SP

soils 30

GM, GC, SM, SM-SC and ML

soils 45

SC, MH, ML-CL and

Inorganic CL soils 60

7

4 (or less)

5

6

7

8

8

10

12

8

10

12

10 (solid )c

8

10

10 (solid )c

10 (solid )c

8

4 (or less)

5

6

7

8

8

8

10

12

10 (solid )c

8

10

12

12 (solid )c

12 (solid )c

8

12

12 (solid )c

Note d

Note d

9

4 (or less)

5

6

7

8

9

8

8

12

12 (solid )c

12 (solid )c

Note d

8

10

12

12 (solid )c

Note d

Note d

8

12

12 (solid )c

Note d

Note d

Note d

PLAIN CONCRETE

WALL

HEIGHT

(feet)

HEIGHT OF

UNBALANCED

BACKFILL

(feet)

MINIMUM NOMINAL WALL THICKNESS (inches)


GW, GP, SW and SP

soils 30


soils 45

SC, MH, ML-CL and


7

4 (or less)

5

6

7

7½

7½

7½

7½

7½

7½

7½

8

7½

7½

8

10

8

4 (or less)

5

6

7

8

7½

7½

7½

7½

10

7½

7½

7½

10

10

7½

7½

10

10

12

9

4 (or less)

5

6

7

8

9

7½

7½

7½

7½

10

10

7½

7½

7½

10

10

12

7½

7½

10

10

12

Note e

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot per foot = 0.157 kPa/m.a. For design lateral soil loads, see 780 CMR 1610. Soil classes are in accordance with the Unified Soil Classification

System and design lateral soil loads are for moist soil conditions without hydrostatic pressure.b. Provisions for table 1806.3(1) are based on construction requirements specified in 780 CMR 1805.5.2.c. Solid grouted hollow units or solid masonry units.d. A design in compliance with 780 CMR 21.00 or reinforcement in accordance with Table 1805.5(2) is required.

e. A design in compliance with 780 CMR 19.00 is required.




TABLE 1806.3(2) 8-INCH CONCRETE AND MASONRY FOUNDATION WALLSWITH REINFORCING WHERE d $ 5 INCHESa, b, c

WALL

HEIGHT

(feet)

HEIGHT OF

UNBALANCED

BACKFILL (feet)

VERTICAL REINFORCEMENT


GW, GP, SW and SP

soils 30


soils 45

SC, MH, ML-CL and


7

4 (or less)

5

6

7

#4 at 48" o.c.

#4 at 48" o.c.

#4 at 48" o.c.

#4 at 40" o.c.

#4 at 48" o.c.

#4 at 48" o.c.

#5 at 48" o.c.

#5 at 40" o.c.

#4 at 48" o.c.

#4 at 40" o.c.

#5 at 40" o.c.

#6 at 48" o.c.

8

4 (or less)

5

6

7

8

#4 at 48" o.c.

#4 at 48" o.c.

#4 at 48" o.c.

#5 at 48" o.c.

#5 at 40" o.c.

#4 at 48" o.c.

#4 at 48" o.c.

#5 at 48" o.c.

#6 at 48" o.c.

#6 at 40" o.c.

#4 at 48" o.c.

#4 at 40" o.c.

#5 at 40" o.c.

#6 at 40" o.c.

#7 at 40" o.c.

9

4 (or less)

5

6

7

8

9

#4 at 48" o.c.

#4 at 48" o.c.

#4 at 48" o.c.

#5 at 48" o.c.

#5 at 40" o.c.

#6 at 40" o.c.

#4 at 48" o.c.

#4 at 48" o.c.

#5 at 48" o.c.

#6 at 48" o.c.

#7 at 48" o.c.

#8 at 48" o.c.

#4 at 48" o.c.

#5 at 48" o.c.

#6 at 48" o.c.

#7 at 48" o.c.

#8 at 48" o.c.

#8 at 32" o.c.


System and design lateral soil loads are for moist soil conditions without hydrostatic pressure.b. Provisions for table1806.3(2) are based on construction requirements specified in 780 CMR 1805.5.2.c. For alternative reinforcement, see 780 CMR 1805.5.3.

TABLE 1806.3(3) 10-INCH CONCRETE AND MASONRY FOUNDATION WALLS WITH REINFORCING WHERE d $ 6.75 INCHESa, b, c

WALL

HEIGHT

(feet)

HEIGHT OF

UNBALANCED

BACKFILL (feet)



GW, GP, SW and SP

soils 30


soils 45

SC, MH, ML-CL and


7

4 (or less)

5

6

7

#4 at 56" o.c

#4 at 56" o.c.

#4 at 56" o.c.

#4 at 56" o.c.

#4 at 56" o.c.

#4 at 56" o.c.

#4 at 48" o.c.

#5 at 56" o.c.

#4 at 56" o.c.

#4 at 56" o.c.

#4 at 40" o.c.

#5 at 40" o.c.

8

4 (or less)

5

6

7

8

#4 at 56" o.c.

#4 at 56" o.c.

#4 at 56" o.c.

#4 at 48" o.c.

#5 at 56" o.c.

#4 at 56" o.c.

#4 at 56" o.c.

#4 at 48" o.c.

#4 at 32" o.c.

#5 at 40" o.c.

#4 at 56" o.c.

#4 at 48" o.c.

#5 at 56" o.c.

#6 at 56" o.c.

#7 at 56" o.c.

9

4 (or less)

5

6

7

8

9

#4 at 56" o.c.

#4 at 56" o.c.

#4 at 56" o.c

#4 at 40" o.c.

#4 at 32" o.c.

#5 at 40" o.c.

#4 at 56" o.c.

#4 at 56" o.c.

#4 at 40" o.c.

#5 at 48" o.c

#6 at 48" o.c.

#6 at 40" o.c.

#4 at 56" o.c.

#4 at 48" o.c.

#4 at 32" o.c.

#6 at 48" o.c.

#4 at 16" o.c.

#7 at 40" o.c.






TABLE 1806.3(4) 12-INCH CONCRETE AND MASONRY FOUNDATION WALLSWITH REINFORCING WHERE d $ 8.75 INCHESa, b, c

WALL

HEIGHT

(feet)

HEIGHT OF

UNBALANCED

BACKFILL (feet)



GW, GP, SW and SP

soils 30


soils 45

SC, MH, ML-CL and


7

4 (or less)

5

6

7

#4 at 72" o.c.

#4 at 72" o.c.

#4 at 72" o.c.

#4 at 72" o.c.

#4 at 72" o.c.

#4 at 72" o.c

#4 at 64" o.c

#4 at 48" o.c.

#4 at 72" o.c.

#4 at 72" o.c.

#4 at 48" o.c.

#5 at 56" o.c.

8

4 (or less)

5

6

7

8

#4 at 72" o.c.

#4 at 72" o.c.

#4 at 72" o.c.

#4 at 64" o.c.

#4 at 48" o.c.

#4 at 72" o.c.

#4 at 72" o.c.

#4 at 56" o.c.

#5 at 64" o.c

#4 at 32" o.c.

#4 at 72" o.c.

#4 at 72" o.c.

#5 at 72" o.c.

#4 at 32" o.c.

#5 at 40" o.c.

9

4 (or less)

5

6

7

8

9

#4 at 72" o.c.

#4 at 72" o.c.

#4 at 72" o.c

#4 at 56" o.c.

#4 at 64" o.c.

#5 at 56" o.c.

#4 at 72" o.c

#4 at 72" o.c.

#4 at 56" o.c.

#4 at 40" o.c.

#6 at 64" o.c.

#7 at 72" o.c.

#4 at 72" o.c.

#4 at 64" o.c.

#5 at 64" o.c.

#6 at 64" o.c.

#6 at 48" o.c.

#6 at 40" o.c.



1806.3.1.2 Thickness Based on Soil Loads,Unbalanced Backfill Height and WallHeight. The thickness of foundation wallsshall comply with the requirements of Table1806.3(1) for plain masonry and plain concretewalls or Table 1806.3(2), 1806.3(3) or1806.3(4) for reinforced concrete and masonrywalls. When using the tables, masonry shall belaid in running bond and the mortar shall beType M or S.

Unbalanced backfill height is the differencein height of the exterior and interior finishground levels. Where an interior concrete slabis provided, the unbalanced backfill heightshall be measured from the exterior finishground level to the top of the interior concreteslab.

1806.3.1.3 Rubble Stone. Foundation walls ofrough or random rubble stone shall not be lessthan 16 inches (406 mm) thick. Rubble stoneshall not be used for foundations for structuresin Seismic Design Category C and D.

1806.3.2 Foundation Wall Materials.Foundation walls constructed in accordance withTables 1806.3(1), 1806.3(2), 1806.3(3) or1806.3(4) shall comply with the following:

1. Vertical reinforcement shall have aminimum yield strength of 60,000 psi (414MPa).2. The specified location of thereinforcement shall equal or exceed theeffective depth distance, d, noted in Tables1806.3(2), 1806.3(3) and 1806.3(4) andshall be measured from the face of the soilside of the wall to the center of vertical

reinforcement. The reinforcement shall beplaced within the tolerances specified inACI 530.1/ASCE 6/TMS 402, Article 3.4B7 of the specified location.3. Concrete shall have a specified compres-sive strength of not less than 2,500 psi (17.2MPa) at 28 days.4. Grout shall have a specified compressivestrength of not less than 2,000 psi (13.8MPa) at 28 days.5. Hollow masonry units shall comply withASTM C 90 and shall be installed with TypeM or S mortar.

1806.3.3 Alternative Foundation WallReinforcement. In lieu of the reinforcementprovisions in Table 1806.3(2), 1806.3(3) or1806.3(4), alternative reinforcing bar sizes andspacings having an equivalent cross-sectional areaof reinforcement per linear foot (mm) of wall arepermitted to be used, provided the spacing ofreinforcement does not exceed 72 inches (1829mm) and reinforcing bar sizes do not exceedNo. 11.

1806.3.4 Hollow Masonry Walls. At least 4inches (102 mm) of solid masonry shall beprovided at girder supports at the top of hollowmasonry unit foundation walls.

1806.3.5 Seismic Requirements. Tables1806.3(1) through 1806.3(4) shall be subject tothe following limitations in 780 CMR 1806.3.5.1and 1806.3.5.2 based on the seismic designcategory assigned to the structure as defined in780 CMR 1616.0.




1806.3.5.1 Seismic Requirements forConcrete Foundation Walls. Concretefoundation walls designed using Tables1806.3(1) through 1806.3(4) shall be subject tothe following limitations:

1. Seismic Design Categories A and B. Nolimitations, except provide not less than twoNo. 5 bars around window and dooropenings. Such bars shall extend at least 24inches (610 mm) beyond the corners of theopenings.2. Seismic Design Category C. Tablesshall not be used except as allowed for plainconcrete members in 780 CMR 1910.4.3. Seismic Design Category D. Tablesshall not be used except as allowed for plainconcrete members in ACI 318, Section22.10.

1806.3.5.2 Seismic Requirements forMasonry Foundation Walls. Masonryfoundation walls designed using Tables1806.3(1) through 1806.3(4) shall be subject tothe following limitations:

1. Seismic Design Categories A and B. Noadditional seismic requirements.2. Seismic Design Category C. A designusing Tables 1806.3(1) through 1806.3(4)subject to the seismic requirements of780 CMR 2106.4.3. Seismic Design Category D. A designusing Tables 1806.3(2) through 1806.3(4)subject to the seismic requirements of780 CMR 2106.5.

1806.4 Retaining Wall Design. Retaining wallsshall be designed to resist the static and seismicpressures of the retained materials, water pressures,and dead and live load surcharges to which suchwalls are subjected, and to ensure stability againstexcessive movements, overturning, sliding,excessive foundation pressure and water uplift. Thestructural design of retaining walls shall conform tothe requirements of 780 CMR 16, 19, 21, 22 and 23.Retaining walls that support an unbalanced height ofretained material greater than six feet (1.83 m), andany retaining system or slope that could impactpublic safety or the stability of an adjacent structure,shall be designed by a registered design professional.

1806.4.1 Overturning and Sliding Stability.Retaining walls shall be designed for a minimumsafety factor of 1.5 against overturning and lateralsliding for static loading conditions.

1806.4.2 Overall Stability. The overall, globalstability of a retaining wall, considering potentialfailure surfaces extending through the materialslocated below, in front of and behind the wall,shall be evaluated.

1806.4.3 Discrete Elements. For retaining wallsconstructed of discrete elements, such as

unmortared masonry, rock, boulders or stackedmodular units, the elements shall be bonded orfastened together to prevent dislodgment understatic and seismic loading conditions wheredislodgment of the elements could pose a risk topublic safety.

1806.4.4 Coping. All masonry retaining walls,other than reinforced concrete walls, shall beprotected with an approved coping.

1806.4.5 Guards. Where retaining walls withdifferences in grade level on either side of the wallin excess of four feet (1.2 m) are located closerthan two feet (0.6 m) to a walk, path, parking lotor driveway on the high side, such retaining wallsshall be provided with guards or other approvedprotective measures.

1806.5 Wall Drainage. Foundation walls andretaining walls shall be designed to support ahydrostatic head of water pressure equal to the fullheight of the wall, unless a drainage system isinstalled in accordance with 780 CMR 1807.4.2 and1807.4.3. Where a drainage system is provided toreduce or eliminate the design hydrostatic pressureon the wall, it shall be designed with sufficientpermeability and discharge capacity to permanentlyprevent hydrostatic pressure on the wall, and shall beprovided with appropriate filters and other designfeatures to prevent blockage due to siltation,clogging or freezing.

1806.6 Seismic Design. Foundation walls andretaining walls shall be designed to resist seismiclateral pressures in accordance with 780 CMR16.00.

780 CMR 1807.0 DAMPPROOFING,

WATERPROOFING AND GROUNDWATER

CONTROL

1807.1 Where required. Walls or portions thereofthat retain earth and enclose interior spaces andfloors below grade shall be waterproofed ordampproofed in accordance with 780 CMR 1807.0,with the exception of those spaces containing groupsother than residential and institutional where suchomission is not detrimental to the building oroccupancy.

Ventilation for crawl spaces shall comply with780 CMR 1202.4.

1807.1.1 Story Above Grade. Where a basementis considered a story above grade and the finishedground level adjacent to the basement wall isbelow the basement floor elevation for 25% ormore of the perimeter, the floor and walls shall bedampproofed in accordance with 780 CMR1807.2 and a foundation drain shall be installed inaccordance with 780 CMR 1807.4.2. Thefoundation drain shall be installed around theportion of the perimeter where the basement flooris below ground level. The provisions of




780 CMR 1802.4.1, 1807.3 and 1807.4.1 shall notapply in this case.

1807.1.2 Underfloor Space. The finished groundlevel of an underfloor space such as a crawl spaceshall not be located below the bottom of thefootings. Where there is evidence that the groundwater table rises to within 6 inches (152 mm) ofthe ground level at the outside building perimeteror where there is evidence that the surface waterdoes not readily drain from the building site, theground level of the underfloor space shall be ashigh as the outside finished ground level, unlessan approved drainage system is provided. Theprovisions of 780 CMR 1802.4.1, 1807.2, 1807.3and 1807.4 shall not apply in this case.

1807.1.2.1 Flood Hazard Areas. For buildingsand structures in flood hazard areas as establishedin 780 CMR 1612.3, the finished ground level ofan underfloor space such as a crawl space shall beequal to or higher than the outside finished groundlevel.

1807.1.3 Ground-water Control. Where theground-water table is lowered and maintained atan elevation not less than six inches (152 mm)below the bottom of the lowest floor, the floor andwalls shall be dampproofed in accordance with780 CMR 1807.2. The design of the system tolower the ground-water table shall be based onaccepted principles of engineering that shallconsider, but not necessarily be limited to,permeability of the soil, rate at which water entersthe drainage system, rated capacity of pumps,head against which pumps are to pump; and therated capacity of the disposal area of the system.The design shall also take into account anyadverse impacts on utilities, structures or otherfacilities in the vicinity which would result fromthe lowering of groundwater levels.

1807.2 Dampproofing Required. Wherehydrostatic pressure will not occur as determined by780 CMR 1802.4.1, floors and walls for other thanwood foundation systems shall be dampproofed inaccordance with 780 CMR 1807.2. Wood founda-tion systems shall be constructed in accordance withAFPA TR7.

1807.2.1 Floors. Dampproofing materials forfloors shall be installed between the floor and thebase course required by 780 CMR 1807.4.1,except where a separate floor is provided above aconcrete slab. Where installed beneath the slab,dampproofing shall consist of not less than 6-mil(0.006 inch; 0.152 mm) polyethylene with jointslapped not less than six inches (152 mm), or otherapproved methods or materials. Where permittedto be installed on top of the slab, dampproofingshall consist of mopped-on bitumen, not less thanfour-mil (0.004 inch; 0.102 mm) polyethylene, orother approved methods or materials. Joints in themembrane shall be lapped and sealed in accord-

ance with the manufacturer’s installationinstructions.

1807.2.2 Walls. Dampproofing materials forwalls shall be installed on the exterior surface ofthe wall, and shall extend from the top of thefooting to above ground level. Dampproofingshall consist of a bituminous material, threepounds per square yard (16 N/m ) of acrylic2

modified cement, c-inch (3.2 mm) coat ofsurface-bonding mortar complying with ASTM C887, any of the materials permitted forwaterproofing by 780 CMR 1807.3.2, or otherapproved methods or materials.

1807.2.2.1 Surface Preparation of Walls.Prior to application of dampproofing materialson concrete walls, holes and recesses resultingfrom the removal of form ties shall be sealedwith a bituminous material or other approvedmethods or materials. Unit masonry walls shallbe parged on the exterior surface below groundlevel with not less than d inch (9.5 mm) ofportland cement mortar. The parging shall becoved at the footing.

Exception. Parging of unit masonry wallsis not required where a material is approvedfor direct application to the masonry.

1807.3 Waterproofing Required. Where theground-water investigation required by 780 CMR1802.4.1 indicates that a hydrostatic pressurecondition exists, and the design does not include aground-water control system as described in780 CMR 1807.1.3, walls and floors shall bewaterproofed in accordance with 780 CMR 1807.3.

1807.3.1 Floors. Floors required to bewaterproofed shall be of concrete, designed andconstructed to withstand the hydrostatic pressuresto which the floors will be subjected.Waterproofing shall be accomplished by placinga membrane of rubberized asphalt, butyl rubber,or not less than six-mil (0.006 inch; 0.152 mm)polyvinyl chloride with joints lapped not less thansix inches (152 mm) or other approved materialsunder the slab. Joints in the membrane shall belapped and sealed in accordance with themanufacturer’s installation instructions.

1807.3.2 Walls. Walls required to bewaterproofed shall be of concrete or masonry andshall be designed and constructed to withstand thehydrostatic pressures and other lateral loads towhich the walls will be subjected. Waterproofingshall be applied from the bottom of the wall to notless than 12 inches (305 mm) above the maximumelevation of the ground water table. Theremainder of the wall shall be dampproofed inaccordance with 780 CMR 1807.2.2. Water-proofing shall consist of two-ply hot-moppedfelts, not less than six-mil (0.006 inch; 0.152 mm)polyvinyl chloride, 40-mil (0.040 inch; 1.02 mm)polymer-modified asphalt, six-mil (0.006 inch;




0.152 mm) polyethylene or other approved methodsor materials capable of bridging nonstructural cracks.Joints in the membrane shall be lapped and sealed inaccordance with the manufacturer’s installationinstructions.

1807.3.2.1 Surface Preparation of Walls.Prior to the application of waterproofingmaterials on concrete or masonry walls, thewalls shall be prepared in accordance with780 CMR 1807.2.2.1.

1807.3.3 Joints and Penetrations. Joints inwalls and floors, joints between the wall and floor,and penetrations of the wall and floor shall bemade watertight utilizing approved methods andmaterials.

1807.4 Subsoil Drainage System. Where ahydrostatic pressure condition does not exist,dampproofing shall be provided and a base shall beinstalled under the floor and a drain installed aroundthe foundation perimeter. A subsoil drainage systemdesigned and constructed in accordance with780 CMR 1807.1.3 shall be deemed adequate forlowering the ground-water table.

1807.4.1 Floor Base Course. Floors ofbasements, except as provided for in 780 CMR1807.1.1, shall be placed over a floor base coursenot less than 4 inches (102 mm) in thickness thatconsists of gravel or crushed stone containing notmore than 10% of material that passes through aNo. 4 (4.75 mm) sieve.

Exception. Where a site is located in well-drained gravel or sand/gravel mixture soils, afloor base course is not required.

1807.4.2 Foundation Drain. A drain shall beplaced around the perimeter of the foundation thatconsists of gravel or crushed stone containing notmore than 10% material that passes through a No.4 (4.75 mm) sieve. The drain shall extend aminimum of 12 inches (305 mm) beyond theoutside edge of the footing. The thickness shallbe such that the bottom of the drain is not higherthan the bottom of the base under the floor, andthat the top of the drain is not less than six inches(152 mm) above the top of the footing. The top ofthe drain shall be covered with an approved filtermembrane material. Where a drain tile orperforated pipe is used, the invert of the pipe ortile shall not be higher than the floor elevation.The top of joints or the top of perforations shall beprotected with an approved filter membranematerial. The pipe or tile shall be placed on notless than two inches (51 mm) of gravel or crushedstone complying with 780 CMR 1807.4.1, andshall be covered with not less than six inches (152mm) of the same material.

1807.4.3 Drainage Discharge. The floor baseand foundation perimeter drain shall discharge bygravity or mechanical means into an approved

drainage system that complies with theInternational Plumbing Code.

Exception. Where a site is located in well-drained gravel or sand/gravel mixture soils, adedicated drainage system is not required.

1807.4.4 Erosion Protection. Where waterimpacts the ground from the edge of the roof,downspout, scupper or other rainwater collectionor diversion device, provisions shall be made toprevent soil erosion and direct the water awayfrom the foundation.

1807.5 Impacts on Groundwater Levels. Below-grade structures and their appurtenances shall bedesigned and constructed so as not to cause changesto the temporary or permanent groundwater level ifsuch changes could adversely impact nearbystructures or facilities including deterioration oftimber piles, settlement, flooding or other impacts.

780 CMR 1808.0 PIER AND PILE

FOUNDATIONS

1808.1 Definitions. The following words and termsshall, for the purposes of 780 CMR 1808.0, have themeanings shown in 780 CMR 1808.1

PIER FOUNDATIONS. Piers are defined herein ascircular or non-circular deep foundation elementsconstructed of concrete that are installed or cast-in-place in holes advanced to the bearing stratum usingnon-displacement excavation methods. Piersdevelop their load-bearing capacity through end-bearing and/or skin friction in the bearing stratum.Piers shall have a minimum lateral dimension of notless than 12 inches (305 mm). The base of the piermay be enlarged to increase the bearing area(referred to as a belled pier). Pier foundationsinclude foundation types referred to as caissons anddrilled shafts.

PILE FOUNDATIONS. Piles are deep foundationelements constructed of wood, steel or concrete,driven, jacked, cast in-place, or a combinationthereof. Piles develop their load-bearing capacitythrough end-bearing and/or skin friction in thebearing stratum. Types of pile foundations coveredby the provisions of 780 CMR include timber,precast concrete, structural steel, concrete-filled steelpipe or tube, steel-cased concrete (mandrel-drivenshell), enlarged base piles (pressure-injectedfootings), hollow-stem augered piles, small diametergrouted piles and caisson piles (concrete-filled pipewith steel core socketed into bedrock).

1808.2 Piers and Piles - General Requirements.

1808.2.1 General. Pier and pile foundations shallbe designed and installed on the basis of afoundation investigation as defined in 780 CMR1802. The design and installation shall be underthe direct supervision of a registered designprofessional knowledgeable in the field of




geotechnical engineering and pier or pile foundationswho shall verify that the piers or piles as installedsatisfy the design criteria. The investigation andreport shall conform to the provisions of 780 CMR1802.0.

1808.2.2 Special Types of Piers and Piles.Types of piers and piles not specifically coveredby the provisions of 780 CMR 1808.0 may bepermitted in accordance with 780 CMR 1801.3.

1808.2.3 Pier and Pile Caps. Pier and pile capsshall be of reinforced concrete, and shall includeall elements to which piles or piers are connected,including beams and mats. The soil immediatelybelow the cap shall not be considered as carryingany vertical load. The tops of piles or piers shallbe embedded not less than three inches (76 mm)into caps and the caps shall extend at least fourinches (102 mm) beyond the edges of piles orpiers. The tops of piles or piers shall be cut backto sound material before capping.

1808.2.4 Stability. Piers or piles shall be bracedto provide lateral stability in all directions. Threeor more piles connected by a rigid cap shall beconsidered braced, provided that the piles arelocated in radial directions from the centroid ofthe group not less than 60 degrees (1 rad) apart. Atwo-pile group in a rigid cap shall be consideredto be braced along the axis connecting the twopiles. Methods used to brace piers or piles shallbe subject to the approval of the building official.

Piles supporting walls shall be drivenalternately in lines spaced at least one foot (305mm) apart and located symmetrically under thecenter of gravity of the wall load carried, unlesseffective measures are taken to provide foreccentricity and lateral forces, or the wall piles areadequately braced to provide for lateral stability.A single row of piles without lateral bracing ispermitted for one- and two-family dwellings andlightweight construction not exceeding two storiesor 35 feet (10,668 mm) in height, provided thecenters of the piles are located within the width ofthe foundation wall.

Individual columns supported on piles shall bedesigned for eccentricity between the column andthe centroid of the supporting piles equal to aminimum of three inches (76 mm) or the actualeccentricity, whichever is greater. The designshall account for such eccentricity through one ofthe following methods:

1. By supporting the column on a minimum ofthree piles in a triangular pattern.2. By designing walls, grade beams orstructural floors to resist the bending momentinduced by the eccentricity.3. By designing the piles, column or both toresist the bending moment induced by theeccentricity and providing adequate lateralrestraint at the top of the piles to resist the

lateral thrust due to the bending moment.1808.2.5 Structural Integrity. Piers or pilesshall be installed in such a manner and sequenceas to prevent distortion or damage to piles beinginstalled or already in place to the extent that suchdistortion or damage affects the structural integrityof the piles.

When piles have been damaged in driving, orhave been driven in locations and alignment otherthan those indicated on the plans, or havecapacities less than required by the design, theaffected pile groups and pile caps shall beinvestigated, and if necessary, the pile groups orpile caps shall be redesigned or additional pilesshall be driven to replace the defective piles.

1808.2.6 Spacing. The minimum center-to-centerspacing of piles shall be not less than twice theaverage diameter of a round pile, nor less than 1¾times the diagonal dimension of a rectangular pile.When driven to or penetrating into rock, thespacing shall be not less than 24 inches (610 mm).When receiving principal support fromend-bearing on materials other than rock orthrough frictional resistance, the spacing shall benot less than 30 inches (762 mm) or as provided in780 CMR 1810.2 Enlarged Base Piles.

The minimum center-to-center spacing betweenadjacent piers designed for friction support shallbe not less than two times the shaft diameter.

1808.2.7 Splices. Splices shall be constructed soas to provide and maintain true alignment andposition of the component parts of the pier or pileduring installation and subsequent thereto andshall be of adequate strength to transmit thevertical and lateral loads and moments occurringat the location of the splice during driving andunder service loading. Splices shall develop notless than 50% of the capacity of the pier or pile inbending. In addition, splices occurring in theupper ten feet (3048 mm) of the embedded portionof the pier or pile shall be capable of resisting atallowable working stresses the moment and shearthat would result from an assumed eccentricity ofthe pier or pile load of three inches (76 mm), orthe pier or pile shall be braced in accordance with780 CMR 1808.2.4 to other piers or piles that donot have splices in the upper ten feet (3048 mm)of embedment.

1808.2.8 Allowable Pier or Pile Loads.

1808.2.8.1 General. The allowable load onpiles or piers shall not exceed the allowableload-bearing capacity in the bearing stratadetermined in accordance with 780 CMR1808.2.8.2 for piles or 780 CMR 1808.2.8.3 forpiers, or the allowable load on the pile or piercross-section computed using the allowablestresses for the particular type of pile or pier inaccordance with 780 CMR 1809.0 through1812.0. The allowable load may also be




limited by the bearing capacity of weaker strataunderlying the bearing stratum (780 CMR1808.2.8.4), group action (780 CMR1808.2.8.4), drivability (780 CMR 1808.2.16)or settlement (780 CMR 1808.2.12).

1808.2.8.2 Piles.

1808.2.8.2.1 Allowable Load-bearingCapacity. The allowable load-bearingcapacity obtained from bearing on orembedment in the pile bearing strata shall bedetermined by load tests performed inaccordance with 780 CMR 1808.2.8.2.4, orby use of applicable formulas as permittedin 780 CMR 1808.2.8.2.2. The allowableload-bearing capacity of jacked piles shallbe determined in accordance with 780 CMR1808.2.8.2.5.

The allowable pile capacity determinedfrom load tests can be applied to other pileswithin the area of substantially similarsubsurface conditions as those for the testpile, providing the performance of the testpile has been satisfactory and the remainingpiles are of the same type, shape and size asthe test pile and are installed using the samemethods and equipment and are driven intothe same bearing strata as the load-testedpile to an equal or greater penetrationresistance.

Pile load tests required by the provisionsof 780 CMR 1808.2.8.2.1 may be waived bythe building official, where justified, uponsubmittal of substantiating data prepared bya registered design professional whichinclude experience and/or performancerecords for the proposed pile installationunder similar soil and loading conditions.

1808.2.8.2.2 Pile Capacity Not Exceeding50 Tons. For piles with a design loadcapacity not exceeding 50 tons, theallowable load-bearing capacity can bedetermined using either the driving formulaor friction formula in clay as permitted in780 CMR 1808.2.8.2.2, or the formula forenlarged base piles in 780 CMR 1810.2.4.

Driving Formula.

1. Where the design load capacity of thepile does not exceed 50 tons, theallowable load may be computed bymeans of the following driving formula:

where:R = allowable pile load in pounds;E = energy per blow in foot-pounds;S = penetration of last blow or average penetra-tion of last few blows expressed in inches; andC = constant equal to 1.0 for drop hammer and

0.1 for steam or air hammer.2. When the design load capacity of apile exceeds 50 tons, the required drivingresistance shall be increased above thatrequired by the driving formula based onload tests or past experience undersimilar conditions.3. The value of S must be determinedwith the hammer operating at 100% ofthe rated number of blows per minute forwhich the hammer is designed.4. Any driving resistance developed instrata overlying the bearing material shallbe discounted.5. If the driving of the pile has beeninterrupted for more than one hour, thevalue of S shall not be determined untilthe pile is driven at least an additional 12inches (305 mm), except when itencounters refusal on or is in a materialof Classes 1 through 6.6. When any pile is driven through alayer of gravel, sand or hard clayexceeding five feet in thickness, andthrough an underlying soft stratum toreach the bearing stratum, the bearingcapacity shall not be determined inaccordance with the driving formula,unless jetting is used during the entiredriving of the pile through the layer ofgravel, sand or hard clay or unless a holeis pre-excavated through said layer foreach pile.

Friction Formula in Clay. Where thedesign load does not exceed 50 tons fordriven concrete or timber piles, wherepredrilling does not remove more than 75%of the pile cross section, the allowable loadon a pile stopped in soil of Material Class 10(Table 1804.3) of medium to hardconsistency may be based on a friction valueof 500 psf of embedded pile surface. Higherdesign loads or other friction values shall bedetermined by pile load tests in accordancewith 780 CMR 1808.2.8.2.4 or 780 CMR1808.2.8.2.6.

The embedded length shall be the lengthof the pile below the surface of the Class 10soil or below the surface of immediatelyoverlying satisfactory bearing material. Thearea of embedded pile surface shall becomputed by multiplying the embeddedlength by the perimeter of the smallest circleor polygon that can be circumscribed aroundthe average section of the embedded lengthof the pile. The method of determining theallowable load described in 780 CMR1808.2.8.2.2 shall not be used for a pile inwhich the drive pipe is withdrawn or for




piles which are driven through the clay to orinto firmer bearing materials.

In case these piles are in clusters, theallowable load on the cluster shall becomputed for the smaller of the followingtwo areas: the sum of the embedded pilesurfaces of individual piles; or the areaobtained by multiplying the perimeter of thepolygon circumscribing the cluster at thesurface of the satisfactory bearing materialby the average embedded length of the piles.

1808.2.8.2.3 Pile capacity exceeding 50tons. When the design load capacity of apile exceeds 50 tons, the required drivingresistance shall be determined based on oneor more compression load tests unlesswaiver of such test(s) is approved by thebuilding official.

1808.2.8.2.4 Compression Load Test.Compression load tests shall be performedin accordance with the following:

Required test Load. A single pile shall beload-tested to not less than twice theallowable design load. When two or morepiles are to be tested as a group, the totalload shall be not less than 1.5 times theallowable design load for the group. In nocase should the load reaching the top of thebearing stratum under maximum test loadfor a single pile or pile group be less thanthe following:

1. Case A-piles designed as end-bearingpiles: 100% of the allowable design load.2. Case B-piles designed as frictionpiles: 150% of the allowable design load.

For piles designed as combination end-bearing and friction piles, Case A applies ifthe pile is designed to support more than50% of its design in bearing; otherwise,Case B applies.

Internal Instrumentation. The test pileshall be instrumented in accordance with therequirements in paragraph 4.4.1 of ASTMD1143 to enable measurement or computa-tion of the load in the pile where it enters thebearing stratum. For piles containingconcrete, instrumentation shall be installedin the test pile to permit direct measurementof the elastic modulus of the pile. Thisrequirement is waived for the followingcases:

1. The test pile is installed within acasing that extends to within ten feetabove the bearing stratum.2. The pile to be tested has beenfunctioning satisfactorily under load fora period of one year or more.3. The pile is 30 feet long or less and noappreciable load will be supported above

the bearing stratum.Loading Procedure. Pile load tests shall beconducted in accordance with ASTMD1143, Standard Method of Testing PilesUnder Static Axial Compressive Load,except that Section 5, Loading Procedures,shall be deleted and replaced by thefollowing provisions:

1. Apply 25% of the allowable designload every 0.5 hour. Longer timeincrements may be used, but each timeincrement should be the same. In no caseshall a load be changed if the rate ofsettlement is not decreasing with time.2. At 200% of the allowable design load(or 150% for pile groups), maintain theload for a minimum of one hour and untilthe settlement (measured at the lowestpoint on the pile at which measurementsare made) over a one-hour period is notgreater than 0.01 in.3. Remove 50% of the design load every15 minutes until zero load is reached.Longer time increments may be used, buteach should be the same.4. Measure rebound at zero load for aminimum of one hour.5. For each load increment ordecrement, take readings at the top of thepile and on the internal instrumentation atone, two, four, eight and 15 minutes andat 15-minute intervals thereafter.A load greater than 200% of the

allowable design load (or 150% of theallowable design load for pile groups) maybe applied at the top of the pile, using theabove loading procedure, to ensure that therequirement for minimum load reaching thebearing stratum is fulfilled. Other optionalmethods listed in ASTM D1143 may beapproved by the building official uponsubmittal in advance of satisfactoryjustification prepared by a registered designprofessional who is qualified in this field.

Selection of Design Load. Provided thatthe design load does not exceed 100% of theload supported in the bearing stratum (or bof the load supported in the bearing stratumfor friction piles or pile groups) when themaximum test load is applied, then theallowable design load shall be the greater ofthe following:

1. Allowable design load based onsettlement during loading: 50% of theapplied test load which causes a grosssettlement at the pile cutoff grade equalto the sum of: a) the theoretical elasticcompression of the pile in inchesassuming all the load on the butt istransmitted to the tip, plus b) 0.15 inch




(3.8 mm), plus c) 1% of the pile tipdiameter or pile width in inches. If thesettlements are so small that the load-settlement curve does not intersect thefailure criterion, the allowable designload shall be 50% of the maximum testload.2. Allowable design load based on thenet settlement after rebound: 50% of theapplied test load which results in a netsettlement at the top of the pile of 0.5inch (13 mm) after rebound for aminimum of one hour at zero load.

1808.2.8.2.5 Jacked Piles. Load testing ofjacked piles shall be performed inaccordance with the following:

1. Not less than 10% of jacked pilesshall be load-tested to twice the designload (load test piles). All other jackedpiles shall be founded in the samebearing stratum as the load test piles andshall be proof-loaded to 125% of designload (production piles).2. For production piles, the 125% ofdesign load shall be maintained for atleast 30 minutes. Acceptability criteria:during final 15 minutes of load, the rateis not progressive (plot is linear ordecreasing when settlement is plottedagainst logarithm of time); and the rate ofsettlement is equal to or less than thatobserved for load test piles during thecorresponding time period under 125% ofdesign load.3. Settlement readings shall be plottedafter one, two, four, eight, and 15minutes, and at 15-minute intervalsthereafter. Load shall be maintained onproduction piles until acceptabilitycriteria are met.4. For load test piles, the load shall beapplied directly to 125% of design loadand maintained for not less than 30minutes, and until the settlement rate isnot progressive (as defined above). Loadshall then be increased to twice thedesign load and maintained constant fornot less than four hours. Settlementduring the four hour period shall not ex-ceed 0.050 inches (1.3 mm). In the eventthat settlement exceeds 0.050 inches(1.3 mm) in four hours, the pile shall bedeemed unacceptable for 50% of the finalload. The allowable load on the rejectedpile may be established by performing anadditional load test at the lesser designload. The design load shall not exceed50% of the load maintained for a fourhour period during which time settlementdid not exceed 0.050 inches (1.3 mm).

1808.2.8.2.6 Tension Load Tests. Theallowable load on piles in tension shall beverified by test unless it is waived by thebuilding official. Pile load test may bewaived by the building official, wherejustified, upon submittal of substantiatingdata which includes experience and/orperformance records for pile installationsunder similar soil and loading conditionsprepared by a registered design professionalexperienced in the geotechnical aspects offoundation design.

Required Load Test. A single pile or apile group shall be load tested to not lessthan 200% of the design load for transientloads (i.e., earthquake and wind) and 250%for sustained loads.

Test Setup and Loading Procedure. Theload test setup, instrumentation and loadingprocedure shall be in accordance withASTM D3689.

Selection of Design Load. Provided theallowable design load does not exceed theallowable stresses in the pile materials, theallowable design load shall be the lower ofthe following:

1. 50% (for transient loads) or 40% (forsustained loads) of the applied test loadwhich results in a net upward movementof 0.5 inch at the top of the pile afterremoval of the maximum test load (Thegross upward movement minus therebound movement).2. 50% (for transient loads) or 40% (forsustained loads) of the applied test loadwhich results in continuous upwardmovement with no increase in load.

1808.2.8.3 Piers. The allowable bearingpressure on the bottom of the pier shall be inaccordance with 780 CMR 1804. Additionalload may be carried by using higher bearingpressures than allowed by 780 CMR 1804and/or by friction on the sides of the pierembedded in suitable bearing material based onrecommendations by a registered designprofessional and subject to the approval of thebuilding official. Such recommendations shallbe based on the results of load tests or othersuitable tests or analyses carried out todetermine side friction and/or end bearing ofpiers installed in the same bearing stratum.

1808.2.8.4 Load-bearing Capacity. Piers,individual piles and groups of piles or piersshall develop ultimate load capacities of atleast twice the design working loads in thedesignated load-bearing layers. Analysis shallshow that no soil layer underlying thedesignated load-bearing layers causes the load-bearing capacity safety factor to be less than




two.Group Action. In cohesive soils, thecompressive load capacity of a group offriction piles shall be analyzed by a generallyaccepted engineering method, and, where suchanalysis indicates, the individual allowable pileload shall be reduced accordingly.

1808.2.8.5 Bent Piers or Piles. The load-bearing capacity of piers or piles discovered tohave a sharp or sweeping bend shall bedetermined by an approved method of analysisor by load testing a representative pier or pile.

1808.2.8.6 Overloads on Piers or Piles. Themaximum compressive load on any pier or piledue to mislocation shall not exceed 110% ofthe allowable design load.

1808.2.9 Lateral Support.

1808.2.9.1 General. Any soil other than fluidsoil shall be deemed to afford sufficient lateralsupport to the pier or pile to prevent bucklingand to permit the design of the pier or pile inaccordance with accepted engineering practiceand the applicable provisions of 780 CMR.

1808.2.9.2 Unbraced Piles. Piles standingunbraced in air, water or in fluid soils shall bedesigned as columns in accordance with theprovisions of 780 CMR. Such piles driven intofirm ground can be considered fixed andlaterally supported at five feet (1524 mm)below the ground surface and in soft material atten feet (3048 mm) below the ground surfaceunless determined otherwise by a registereddesign professional.

1808.2.9.3 Allowable Lateral Load. Whererequired by the design, the lateral load capacityof a pier, a single pile or a pile group shall bedetermined by an approved method of analysisor by lateral load tests to at least twice theproposed design working load. The load testsetup instrumentation and loading procedureshall be in accordance with ASTM D3966.The design load shall be selected by theresponsible registered design professional,based upon interpretation of the load-deflectiondata from the load test. The resultingallowable load shall not be more than one-halfof that test load that produces a gross lateralmovement of one inch (25 mm) at the groundsurface.

1808.2.10 Use of Higher Allowable Pier or PileStresses. Allowable stresses greater than thosespecified for piers or for each pile type in780 CMR 1809.0 through 1812.0 are permittedwhere supporting data justifying such higherstresses is filed with the building official. Suchsubstantiating data shall include:

1. A soils investigation in accordance with780 CMR 1802, wave equation analyses of pile

driveability, analyses of load transfer duringtesting, and prediction of performance duringlong term service.2. Pier or pile load tests in accordance with780 CMR 1808.2.8.2.4, regardless of the loadsupported by the pier or pile.

1808.2.11 Piles and Piers in Subsiding Areas.Where piles and piers are installed throughsubsiding fills or other subsiding strata and derivesupport from underlying firmer materials,consideration shall be given to the downwardfrictional forces that may be imposed on the pilesor piers by the subsiding upper strata.

Where the influence of subsiding fills isconsidered as imposing loads on the pile or pier,the allowable stresses specified in 780 CMR 1809through 1812 are permitted to be increased wheresatisfactory substantiating data are submitted.

1808.2.12 Settlement Analysis. The settlementof piers, individual piles or groups of piles shallbe estimated based on approved methods ofanalysis. The predicted settlement shall neithercause harmful distortion of, or instability in, thestructure, nor cause any stresses to exceedallowable values.

1808.2.13 Pre-excavation. The use of jetting,augering or other methods of pre-excavation shallbe in accordance with the recommendations of theregistered design professional. Where used, pre-excavation shall be carried out in the same manneras used for piers or piles subject to load tests andin such a manner that will not impair the carryingcapacity of the piers or piles already in place ordamage adjacent structures. Pile tips shall bedriven below the pre-excavated depth until therequired resistance or penetration is obtained.

1808.2.14 Installation Sequence. Piles shall beinstalled in such sequence as to avoid compactingthe surrounding soil to the extent that other pilescannot be installed properly, and to preventground movements that are capable of damagingadjacent structures.

1808.2.15 Use of Vibratory Drivers. Vibratorydrivers shall only be used to install piles where thepile load capacity is verified by load tests inaccordance with 780 CMR 1808.2.8.2.4. Theinstallation of production piles shall be controlledaccording to power consumption, rate ofpenetration or other approved means that ensurepile capacities equal or exceed those of the testpiles.

1808.2.16 Pile Driveability. Pile cross sectionsshall be of sufficient size and strength towithstand handling and driving stresses withoutdamage to the pile and to provide sufficientstiffness to transmit the required driving forces.Driven piles of uniform cross section or taperedpiles shall have a minimum nominal diameter ofeight inches (200 mm) except as provided in




780 CMR 1809.1.3.3 for timber piles. Taperedshoes or points of lesser dimensions may be attachedto the pile unit.

1808.2.17 Protection of Pile and Pier Materials.Where boring records or site conditions indicatepossible deleterious action on pier or pilematerials because of soil constituents, changingwater levels or other factors, the pier or pilematerials shall be adequately protected bymaterials, methods or processes in accordancewith the recommendations of the registered designprofessional. Protective materials shall be appliedto the piles so as not to be rendered ineffective bydriving. The effectiveness of such protectivemeasures for the particular purpose shall havebeen thoroughly established by satisfactoryservice records or other evidence thatdemonstrates their effectiveness.

Steel and Steel-concrete Piles. At locationswhere steel and steel-concrete piles will be incontact with any material which is corrosive tothe steel, one of the following procedures shallbe used for protection, or any other methodwhich will satisfy the requirements of thebuilding official:

1. Remove all objectionable material.2. Effectively protect the steel surface frompile cutoff grade to a grade 15 feet (4.6 m)below the bottom of the objectionablematerial by means of:

a. cathodic protection as approved bythe building official;b. an approved encasement of not lessthan three inches (76 mm) of denseconcrete;c. an effective protective coating subjectto the approval of the building official; ord. providing an excess steel thickness of1/8 inch (3.2 mm) beyond designrequirements on all exposed steelsurfaces.

1808.2.18 Use of Existing Piers or Piles. Piles orpiers that have previously supported a partially orfully demolished structure shall not be used forsupport of new construction unless satisfactoryevidence is submitted to the building officialwhich indicates that the piles or piers have notbeen adversely impacted by the demolition, aresound, have adequate capacity to support the newdesign loads, and meet all of the requirements of780 CMR 18.00. The capacities of such piles orpiers shall be determined by analyses, load testingor redriving.

Requirements for Piles. The design load forpiles to be reused shall not exceed the greaterof the following values:

1. Actual sustained load determined tohave been previously supportedsatisfactorily by the piles, up to a maximum

of 120 tons2. The documented, as-built designcapacity of the piles, as confirmed by priorload testing3. Design capacity determined by analysesand confirmed by new load testing or byredriving per 780 CMR 1808.2.8.2.2 on oneor more piles representative of each config-uration (s) of pile and subsurface conditions.

1808.2.19 Heaved Piles. Adequate provisionshall be made to observe pile heave. Accuratereference points shall be established on each pileimmediately after installation; for cast-in-placepiles with unfilled corrugated shells, the referencepoint shall be at the bottom of the pile. If,following the installation of other piles in thevicinity, heaving of ½ inch (13 mm) or moreoccurs, the heaved piles shall be re-driven todevelop the required capacity and penetration, orthe capacity of the pile may be verified by loadtests in accordance with 780 CMR 1808.2.8.2.4.

1808.2.20 Identification. Pier or pile materialsshall be identified for conformity to the specifiedgrade with this identity maintained continuouslyfrom the point of manufacture to the point ofinstallation or shall be tested by an approvedagency to determine conformity to the specifiedgrade. The approved agency shall furnish anaffidavit of compliance to the building official.

1808.2.21 Pier or Pile Location Plan. A planshowing the location and designation of piers orpiles by an identification system shall be filedwith the building official prior to installation ofsuch piers or piles. Detailed records for piers orindividual piles shall bear an identificationcorresponding to that shown on the plan.

1808.2.22 Special Inspection. Specialinspections shall be provided for piles and piers,respectively. The owner shall engage a registereddesign professional who shall submit hisqualifications in writing to the building official.This design professional, or his representative,who must be qualified by experience and training,shall be present at all times while piles and piersare being installed to observe all work. Thedesign professional or his representative shallmake an accurate record of the following:

1. For driven piles, the material and theprincipal dimensions of each pile, weight andfall of the ram, the type, size and make ofhammer, cushion blocks, the number of blowsper minute, the energy per blow, the number ofblows per inch for the last six inches (150 mm)of driving, together with the grades at point andcutoff and any other pertinent details. For cast-in-place piles, installation equipment andmethods used, casings, pile dimensions,reinforcement, grouting volumes andprocedures used, and all other pertinent




installation data.For piers, pier installation procedures includingobservations and tests of the bearing material inplace, pier dimensions and placement of concreteand reinforcement. When direct inspection of thebearing surface is impossible, a suitable method shallbe employed, to verify the condition of the bearingmaterial and to make the measurements and tests.

A copy of these records shall be signed by theregistered design professional, and filed in the officeof the building official.

1808.3 Seismic Design of Piers or Piles.

1808.3.1 Seismic Reinforcement. Piles and piersshall have minimum longitudinal reinforcementand confining reinforcement in accordance withthe provisions for specific pile types and piers in780 CMR 1809.0 through 1812.0.

Ends of hoops, spirals and ties shall beterminated with seismic hooks, as defined inSection 21.1 of ACI 318, turned into the confinedconcrete core. The minimum transverse steel ratiofor confinement shall not be less than one-half ofthat required for columns.

Where a minimum length for reinforcement orthe extent of closely spaced confining reinforce-ment is specified at the top of the pier or pile,provisions shall be made so that those specifiedlengths or extents are maintained after pier or pilecut-off.

Where confining reinforcement is specified atthe top of the pile or pier, alternative measures forlaterally confining concrete and maintainingtoughness and ductile-like behavior at the top ofthe pile or pier will be permitted provided thedesign is such that any hinging occurs in theconfined region.

1808.3.2 Seismic Bending Design. Piles or piersfor structures assigned to Seismic DesignCategory D in accordance with 780 CMR 1616shall be designed and constructed to withstand themaximum imposed curvatures from earthquakeground motions and structure response.Curvatures shall include free-field soil strainsmodified for soil-pile-structure interactioncoupled with pier or pile deformations induced bylateral pier or pile resistance to structure seismicforces. Concrete piers or piles on Site Class E orF sites, as determined in 780 CMR 1615.1.1, shallbe designed and detailed in accordance withSections 21.4.4.1, 21.4.4.2 and 21.4.4.3 of ACI318 within seven pile diameters of the pile capand the interfaces of soft to medium stiff clay orliquefiable strata.

1808.3.3 Pile Cap Seismic Connection. Piles orpiers for structures assigned to Seismic DesignCategory C and D in accordance with 780 CMR1616 shall be connected to the pile or pier caps inaccordance with the following provisions.

1808.3.3.1 Concrete Piles and Piers. These

provisions apply to the pile types and pierscovered in 780 CMR 1809.2, 1810.0 and1812.0. The piles or piers shall be connectedto the pile or pier cap by extending thelongitudinal reinforcing into the cap for adistance equal to the development length asspecified in ACI 318. The development lengthto be provided in the cap is the fulldevelopment length for compression withoutreduction in length for excess area. Field-placed dowels anchored in the pile or pierconcrete at least twice the required capdevelopment length are acceptable.

For concrete-filled steel pipe and tube piles,longitudinal reinforcement shall be provided atthe top of the pile in accordance with 780 CMR1810.6.4.1, and the reinforcement shall beanchored into the pile cap in accordance withthe requirements of 780 CMR 1808.3.3.1.

For precast prestressed concrete piles instructures assigned to Seismic DesignCategory C, the pile cap connection can bemade by extending the exposed pile reinforcingstrand into the pile cap with an embedmentlength sufficient to develop the strength of thereinforcing strand. This is not permitted forpiles in structures assigned to Seismic DesignCategory D.

1808.3.3.2 Structural Steel Piles. Structuralsteel piles covered in 780 CMR 1809.3 shall beconnected to the pile cap with a connectiondetail designed for a minimum tensile forceequal to 10% of the pile compression designload. The pile cap connection shall be made bymeans other than concrete bond to the baresteel section.

1808.3.3.3 Seismic Design Category D. Forstructures assigned to Seismic DesignCategory D the pile or pier cap connection shallmeet the following additional requirements. For piles or piers required to resist uplift forcesor provide rotational restraint, the design of theanchorage into the pile or pier cap shallconsider the combined effect of axial forcesdue to uplift and bending moments due to fixityat the cap. The anchorage shall develop aminimum of 25% of the strength of the pile orpier in tension and shall be capable ofdeveloping the following load capacities:

1. In the case of uplift, the lesser of thenominal tensile strength of the longitudinalreinforcement in a concrete pile or pier, orthe nominal tensile strength of a steel pile,or the pile or pier uplift soil nominalstrength factored by 1.3 or the axial tensionforce resulting from the load combinationsof 780 CMR 1605.4.2. In the case of rotational restraint, thelesser of the axial and shear forces, andmoments resulting from the load




combinations of 780 CMR 1605.4 or development ofthe full axial, bending and shear nominal strength ofthe pile or pier.

1808.3.4 Seismic Foundation Ties. Pile or pierfoundations for structures assigned to SeismicDesign Category C and D in accordance with780 CMR 1616 shall be interconnected by tiescapable of carrying, in tension and compression,a force equal to the product of the larger pile cap

DSor column load times the seismic coefficient Sdivided by ten. Ties are not required where it canbe demonstrated that equivalent restraint isprovided by reinforced concrete beams withinslabs-on-grade or reinforced concrete slabs-on-grade or confinement by competent rock, hardcohesive soils, or very dense granular soils.

Exception. Piers supporting foundation walls,isolated interior posts detailed so the pier is notsubject to lateral loads, lightly loaded exteriordecks and patios, of Group R, Division 3 andGroup U, Division 1 occupancies not ex-ceeding two stories of light-frame construction,are not subject to interconnection if it can beshown the soils are of adequate stiffness,subject to the approval of the building official.

780 CMR 1809.0 DRIVEN PILE

FOUNDATIONS

1809.1 Timber Piles. Timber piles shall bedesigned in accordance with the AFPA NDS.

1809.1.1 Materials. Round timber piles shallconform to ASTM D 25. Round timber pilingshall be new longleaf, shortleaf, loblolly or slashspecies of Southern pine, oak, Douglas fir or otherwoods of similar strength and physicalcharacteristics. Sawn timber piles shall conformto DOC PS-20.

1809.1.2 Preservative Treatment. Timber pilesused to support permanent structures shall betreated in accordance with 780 CMR 1809.1.2unless it is established that the tops of theuntreated timber piles will be below the lowestground water level assumed to exist during the lifeof the structure. Preservative and minimum finalretention shall be in accordance with AWPA C3for round timber piles, and AWPA C24 for sawntimber piles. Preservative-treated timber pilesshall be subject to a quality control programadministered by an approved agency. Pile cutoffsshall be treated in accordance with AWPA M4.

1809.1.3 Allowable Load.

1809.1.3.1 Allowable Stress. The allowablestress in the timber shall not exceed 1,000 psi(6.9 MPa) in compression at the critical cross-sectional area taken at the top of the bearingstratum. Piles designed for end bearing onmaterials of Classes 1 and 2 in Table 1804.3shall be designed for a maximum stress of 500

psi (3.4 MPa) in compression on the pile cross-sectional area at the tip.

1809.1.3.2 Maximum Load. The load ontimber piles shall not exceed the allowable loadspecified in 780 CMR 1808.2.8 nor 35 tons,whichever is smaller.

1809.1.3.3 Minimum Dimensions. Timberpiles shall be no less than six inches (152 mm)in diameter at the tip.

1809.1.4 Precautions During Driving.

1809.1.4.1 Hammer Energy. Pile hammerenergy shall be selected to prevent damage tothe pile, but in no case shall the maximumhammer energy, as rated by the manufacturer,exceed 18,000 ft.-lbs.

1809.1.4.2 End-supported Piles. Any suddendecrease in driving resistance of an end-supported timber pile shall be investigated withregard to the possibility of damage. If thesudden decrease in driving resistance cannot becorrelated to load-bearing data, the pile shall beremoved for inspection or rejected.

1809.2 Precast Concrete Piles.

1809.2.1 General. The materials, reinforcementand installation of precast concrete piles shallconform to 780 CMR 1809.2.1.1 through1809.2.1.4.

1809.2.1.1 Design and Manufacture. Pilesshall be designed and manufactured inaccordance with accepted engineering practiceto resist all stresses induced by handling,driving and service loads. When driven to orinto bearing materials of Classes 1 and 2inclusive, or through materials containingboulders, piles shall have metal tips ofapproved design.

1809.2.1.2 Minimum Dimension. Theminimum lateral dimension shall be eightinches (203 mm). Corners of square piles shallbe chamfered.

1809.2.1.3 Reinforcement. Longitudinal steelshall be arranged in a symmetrical pattern andshall be laterally tied with steel ties or wirespiral spaced not more than four inches (102mm) apart, center-to-center, for a distance oftwo feet (610 mm) from the ends of the pile;and not more than six inches (152 mm)elsewhere except that at the ends of each pile,the first five ties or spirals shall be spaced oneinch (25.4 mm) center to center. The gage ofties and spirals shall be as follows:

1. For piles having a diameter of 16 inches(406 mm) or less, wire shall not be smallerthan 0.22 inch (5.6 mm) (No. 5 gage).2. For piles having a diameter of more than16 inches (406 mm) and less than 20 inches(508 mm), wire shall not be smaller than




0.238 inch (6 mm) (No. 4 gage).3. For piles having a diameter of 20 inches(508 mm) and larger, wire shall not besmaller than ¼ inch (6.4 mm) round or0.259 inch (6.6 mm) (No. 3 gage).

1809.2.1.4 Installation. Piles shall be handledand driven so as not to cause injury or over-stressing, which affects durability or strength.

1809.2.2 Precast Nonprestressed Piles. Precastnon-prestressed concrete piles shall conform to780 CMR 1809.2.2.1 through 1809.2.2.5.

1809.2.2.1 Materials. Concrete shall have a28-day specified compressive strength (f’ ) ofc

not less than 4,000 psi (20.68 Mpa).

1809.2.2.2 Minimum Reinforcement. Theminimum amount of longi tudinalreinforcement shall be 0.8% of the concretesection and shall consist of at least four bars.

1809.2.2.2.1 Seismic Reinforcement inSeismic Design Category C. Where astructure is assigned to Seismic DesignCategory C in accordance with 780 CMR1616, the following shall apply. Longitud-inal reinforcement with a minimum steelratio of 0.01 shall be provided throughoutthe length of precast concrete piles. Withinthree pile diameters of the bottom of the pilecap, the longitudinal reinforcement shall beconfined with closed ties or spirals of aminimum d inch (9.5mm) diameter. Tiesor spirals shall be provided at a maximumspacing of eight times the diameter of thesmallest longitudinal bar, not to exceed sixinches (152 mm). Throughout theremainder of the pile, the closed ties orspirals shall have a maximum spacing of 16times the smallest longitudinal-bar diameter,not to exceed eight inches (203 mm).

1809.2.2.2.2 Seismic Reinforcement inSeismic Design Category D. Where astructure is assigned to Seismic DesignCategory D in accordance with 780 CMR1616, the requirements for Seismic DesignCategory C in 780 CMR 1809.2.2.2.1 shallapply except as modified in 780 CMR1809.2.2.2.2. Transverse confinementreinforcement consisting of closed ties orequivalent spirals shall be provided inaccordance with Sections 21.4.4.1, 21.4.4.2and 21.4.4.3 of ACI 318 within three pilediameters of the bottom of the pile cap. Forother than Site Class E or F, or liquefiablesites and where spirals are used as thetransverse reinforcement, it shall bepermitted to use a volumetric ratio of spiralreinforcement of not less than one-half thatrequired by Section 21.4.4.1(a) of ACI 318.

1809.2.2.3 Allowable Stresses. The allowablecompressive stress in the concrete shall not

exceed 33% of the 28-day specified compres-sive strength (f’ ), nor 1,600 psi (11.0 MPa),c

applied to the gross cross-sectional area of thepile. The allowable compressive stress in thereinforcing steel shall not exceed 40% of the

yyield strength of the steel (f ) or a maximum of30,000 psi (207 MPa). The allowable tensilestress in the reinforcing steel shall not exceed

y50% of the yield strength of the steel (f ) or amaximum of 24,000 psi (165 Mpa).

1809.2.2.4 Installation. A precast concretepile shall not be driven before the concrete hasattained a compressive strength of at least 75%of the 28-day specified compressive strength

c(f’ ), but not less than the strength sufficient towithstand handling and driving forces.

1809.2.2.5 Concrete Cover. Reinforcementfor piles that are not manufactured under plantconditions shall have a concrete cover of notless than two inches (51 mm).

Reinforcement for piles manufactured underplant control conditions shall have a concretecover of not less than 1¼ inches (32 mm) forNo. 5 bars and smaller, and not less than 1½inches (38 mm) for No. 6 through No. 11 barsexcept that longitudinal bars spaced less than1½ inches (38 mm) clear distance apart shall beconsidered bundled bars for which theminimum concrete cover shall be equal to thatfor the equivalent diameter of the bundled bars.

Reinforcement for piles exposed to seawater shall have a concrete cover of not lessthan three inches (76 mm).

1809.2.3 Precast Prestressed Piles. Precastprestressed concrete piles shall conform to therequirements of 780 CMR 1809.2.3.1 through1809.2.3.5.

1809.2.3.1 Materials. Prestressing steel shallconform to ASTM A 416. Concrete shall have

ca 28-day specified compressive strength (f’ ) ofnot less than 5,000 psi (34.48 Mpa).

1809.2.3.2 Design. Precast prestressed pilesshall be designed to resist stresses induced byhandling and driving as well as by loads. Theeffective prestress in the pile shall not be lessthan 400 psi (2.76 MPa) for piles up to 30 feet(9144 mm) in length, 550 psi (3.79 MPa) forpiles up to 50 feet (15 240 mm) in length, and700 psi (4.83 MPa) for piles greater than 50feet (15 240 mm) in length.

Effective prestress shall be based on anassumed loss of 30,000 psi (207 MPa) in theprestressing steel. The tensile stress in theprestressing steel shall not exceed the valuesspecified in ACI 318.

1809.2.3.2.1 Design in Seismic DesignCategory C. Where a structure is assignedto Seismic Design Category C in accordancewith 780 CMR 1616.0, the following shall




apply. The minimum volumetric ratio of spiralreinforcement shall not be less than 0.007 or theamount required by the following formula for theupper 20 feet (6096 mm) of the pile:

EQUATION 18-4

s c yhD = 0.12f’ /fwhere:

cf’ = Specified compressive strength ofconcrete psi (MPa).

yhf = Yield strength of spiral reinforcement #85,000 psi (586 MPa).

sr = Spiral reinforcement index (vol. spiral/ vol.core).

At least ½ the volumetric ratio requiredby Equation 18-4 shall be provided belowthe upper 20 feet (6096 mm) of the pile.

The pile cap connection by means ofdowels as indicated in 780 CMR 1803.3.3 ispermitted. Pile cap connection by means ofdeveloping pile reinforcing strand ispermitted provided that the pile reinforcingstrand results in a ductile connection.

1809.2.3.2.2 Design in Seismic DesignCategory D. Where a structure is assignedto Seismic Design Category D in accordancewith 780 CMR 1616.00, the requirementsfor Seismic Design Category C in 780 CMR1809.2.3.2.1 shall be met, in addition to thefollowing:

1. Requirements in ACI 318,Chapter 21, need not apply, unlessspecifically referenced.2. Where the total pile length in the soilis 35 feet (10 668 mm) or less, the lateraltransverse reinforcement in the ductileregion shall occur through the length ofthe pile. Where the pile length exceeds35 feet (10 668 mm), the ductile pileregion shall be taken as the greater of 35feet (10 668 mm) or the distance from theunderside of the pile cap to the point ofzero curvature plus three times the leastpile dimension.3. In the ductile region, the center-to-center spacing of the spirals or hoopreinforcement shall not exceed one-fifthof the least pile dimension, six times thediameter of the longitudinal strand, oreight inches (203 mm), whichever issmaller.4. Circular spiral reinforcement shall bespliced by lapping one full turn andbending the end of the spiral to a 90-degree hook or by use of a mechanical orwelded splice complying with Sect.12.14.3 of ACI 318.5. Where the transverse reinforcementconsists of circular spirals, the volumetricratio of spiral transverse reinforcement in

the ductile region shall comply with thefollowing:

EQUATION 18-5

s c yh g ch c gD = 0.25(f’ /f )(A /A - 1.0)[0.5 + 1.4P/(f’ A )]

but not less than:

EQUATION 18-6

s c yh c gD = 0.12(f’ /f )[0.5 + 1.4P/(f’ A )]

and need not exceed:

EQUATION 18-7

sD = 0.021where:

gA = Pile cross-sectional area, square inches(mm ).2

chA = Core area defined by spiral outsidediameter, square inches (mm ).2

cf’ = Specified compressive strength ofconcrete, psi (MPa).

yhf = Yield strength of spiral reinforcement #85,000 psi (586 MPa).P = Axial load on pile, pounds (kN), asdetermined from Equations 16-5 and 16-6.

sD = Volumetric ratio (vol. spiral/ vol. core).

This required amount of spiralreinforcement is permitted to be obtainedby providing an inner and outer spiral.6. When transverse reinforcementconsists of rectangular hoops and cross-ties, the total cross-sectional area oflateral transverse reinforcement in theductile region with spacings, andperpendicular to dimension, hc, shallconform to:

EQUATION 18-8

sh c c yh g ch c gA = 0.3sh (f’ /f )(A /A – 1.0)[0.5 + 1.4P/(f’ A )]

but not less than:

EQUATION 18-9

sh c c yh c gA = 0.12sh (f’ /f )[0.5 + 1.4P/(f’ A )]

where:

yhf = # 70,000 psi (483 MPa).

ch = Cross-sectional dimension of pile coremeasured center to center of hoop reinforcement,inch (mm).s = Spacing of transverse reinforcementmeasured along length of pile, inch (mm).

shA = Cross sectional area of transversereinforcement, square inches (mm )2

cf’ = Specified compressive strength ofconcrete, psi (Mpa)

The hoops and cross-ties shall beequivalent to deformed bars not less thanNo. 3 in size. Rectangular hoop endsshall terminate at a corner with seismichooks.




Outside of the length of the pilerequiring transverse confinementreinforcing, the spiral or hoop reinforcingwith a volumetric ratio not less than one-half of that required for transverse con-finement reinforcing shall be provided.

1809.2.3.3 Allowable Stresses. The maximum

callowable design compressive stress, f , inconcrete shall be determined as follows:

EQUATION 18-10

c c pc, f = 0.33 f’ – 0.27f but not greater than 1600 psi(11.0 MPa)

where:

cf’ = The 28-day specified compressivestrength of the concrete.

pcf = The effective prestress stress on the grosssection.

1809.2.3.4 Installation. A prestressed pileshall not be driven before the concrete hasattained a compressive strength of at least 75%of the 28-day specified compressive strength

c(f’ ), but not less than the strength sufficient towithstand handling and driving forces.

1809.2.3.5 Concrete Cover. Prestressing steeland pile reinforcement shall have a concretecover of not less than 1¼ inches (32 mm) forsquare piles of 12 inches (305 mm) or smallersize and 1½ inches (38 mm) for larger piles,except that for piles exposed to sea water, theminimum protective concrete cover shall not beless than 2½ inches (64 mm).

1809.3 Structural Steel Piles. Structural steel pilesshall conform to the requirements of 780 CMR1809.3.1 through 1809.3.4.

1809.3.1 Materials. Structural steel piles, steelpipe and fully welded steel piles fabricated fromplates shall conform to ASTM A 36, A 252, A283, A 572, A 588 or A 913.

1809.3.2 Allowable Stresses. The allowabledesign compressive stress shall not exceed 35% ofthe minimum specified yield strength of the steelnor 12,600 psi (86.9 Mpa).

Exception. Where justified in accordance with780 CMR 1808.2.10, the allowable axial stress

yis permitted to be increased above 0.35F , but

yshall not exceed 0.5F .

1809.3.3 Dimensions and Tip Reinforcementof H-piles. Sections of H-piles shall complywith the following:

1. The flange projections shall not exceed14 times the minimum thickness of metal ineither the flange or the web and the flangewidths shall not be less than 80% of thedepth of the section.2. The nominal depth in the direction of theweb shall not be less than eight inches (203mm).

3. Flanges and web shall have a minimumnominal thickness of d inch (9.5 mm).

1809.3.3.1 Tip reinforcement. The tips of allsteel H piles having a thickness of metal lessthan 0.5 in. (12.7 mm) which are driven to endbearing on rock of Classes 1 through 3 by animpact hammer shall be reinforced. Theinstallation of all steel H piles by impacthammer to end bearing on rock of Classes 1through 3 shall be conducted so as to terminatedriving when the pile reaches refusal on therock surface.

1809.3.4 Dimensions of Steel Pipe Piles. Steelpipe piles driven open ended shall have a nominaloutside diameter of not less than 8 inches (203mm). The pipe shall have a minimum of 0.34square inch (219 mm ) of steel in cross section to2

resist each 1,000 foot-pounds (1356 N-m) of pilehammer energy or the equivalent strength forsteels having a yield strength greater than 35,000psi (241 MPa). Where pipe wall thickness lessthan 0.188 inch (4.8 mm) is driven open-ended, asuitable cutting shoe shall be provided.

780 CMR 1810.0 CAST-IN-PLACE

CONCRETE PILE FOUNDATIONS

1810.1 General. The materials, reinforcement andinstallation of cast-in-place concrete piles shallconform to 780 CMR 1810.

1810.1.1 Material. All concrete shall have a 28-day specified compressive strength (f’c) of notless than 3,000 psi (20.7 MPa). The maximumsize of coarse aggregate for all concrete shall be ¾inch (19 mm), and the concrete shall have a slumpof four to seven inches (102 mm to 178 mm). Ifconcrete is to be pumped, the mix designincluding slump shall be adjusted to produce apumpable concrete.

1810.1.2 Reinforcement. Except for steel dowelsembedded five feet (1524 mm) or less in the pileand as provided in 780 CMR 1810.3.4, reinforce-ment where required shall be assembled and tiedtogether and shall be placed in the pile as a unitbefore the reinforced portion of the pile is filledwith concrete except in augered uncased cast-in-place piles. Tied reinforcement in augered un-cased cast-in-place piles shall be placed after pilesare concreted, while the concrete is still in asemifluid state.

1810.1.2.1 Seismic Reinforcement in SeismicDesign Category C. Where a structure isassigned to Seismic Design Category C inaccordance with 780 CMR 1616.0, thefollowing shall apply. A minimum longitudin-al reinforcement ratio of 0.0025 shall beprovided in the top a of the pile length or thelength determined by analysis, but not less thanten feet (3048 mm) below the ground. Thereinforcing shall be a minimum of four




longitudinal bars, with closed ties of a minimum ¼inch (6 mm) diameter provided at 16-longitudinal-bar-diameter maximum spacing, or with equivalentspirals. Within a distance below the bottom of thepile cap equal to three times the least pile dimension,trans-verse confinement reinforcing shall have amaximum spacing of six inches (152 mm) or eight-longitudinal-bar-diameters, whichever is less.

1810.1.2.2 Seismic Reinforcement in SeismicDesign Category D. Where a structure isassigned to Seismic Design Category D inaccordance with 780 CMR 1616, therequirements for Seismic Design Category Cgiven above shall be met, in addition to thefollowing. A minimum longitudinal reinforce-ment ratio of 0.005 shall be provided in the top½ f of the pile length, a minimum of ten ftbelow the ground, or throughout the flexurallength of the pile, whichever length is greatest.The flexural length shall be taken as the lengthof the pile to a point where the concrete sectioncracking moment strength multiplied by 0.4exceeds the required moment strength at thatpoint. The reinforcing shall be a minimum offour longitudinal bars with transverse confine-ment reinforcing provided in the pile inaccordance with Sections 21.4.4.1, 21.4.4.2,and 21.4.4.3 of ACI 318 within a distancebelow the bottom of the pile cap equal to threetimes the least pile dimension. It shall bepermitted to use a transverse spiral reinforcingratio of not less than ½ of that required inSection 21.4.4.1(a) of ACI 318 for other thanClass E, F, or liquefiable sites. Tie spacingthroughout the remainder of the concretesection shall not exceed 12-longitudinal-bar-diameters, one-half the least dimension of thesection, nor 12 inches (305 mm). Ties shall bea minimum of No. 3 bars for piles with a leastdimension up to 20 inches (508 mm), and No.4 bars for larger piles.

Exception. Confinement by ties or spiralsis not required where permanent metalcasing (steel pipe, steel tube or spiral-welded steel shell) is used, provided thecasing has minimum thickness as follows:for Seismic Performance Category Cstructures, 0.058 inch (1.5 mm), and forSeismic Performance Category D structures,0.070 inch (1.8mm). The steel casing mustbe adequately protected from corrosion dueto soil, changing water levels or othersubsurface conditions indicated by the sitesoil investigation.

1810.1.3 Concrete Placement. For all casedpiles, the inside of the pipe or casing shall bethoroughly cleaned to the bottom and visuallyinspected prior to filling with concrete. Concreteshall be placed in such a manner as to ensure theexclusion of any foreign matter and to secure a

full-sized shaft. The concreting shall be subject tothe following limitations:

1. The diameter shall not vary more than 20%from the specified value.2. Concrete shall not be placed through waterexcept where tremie methods are approved.3. When depositing concrete from the top ofthe pile, the concrete flow shall be rapid andcontinuous through a funnel hopper centered atthe top of the pile.4. After filling with concrete, the top ten feet(3 m) shall be thoroughly rodded.5. No pile shall be installed within a distanceof nine feet (2.7 m) from a pile which has beenfilled with concrete for less than 12 hours,unless approved.

1810.2 Enlarged Base Piles. Enlarged base pilesshall conform to the requirements of 780 CMR1810.2.1 through 1810.2.5.

1810.2.1 Materials. The maximum size forcoarse aggregate for concrete shall be ¾ inch(19.1 mm). Concrete to be compacted shall havea zero slump.

1810.2.2 Allowable Stresses. The maximumallowable design stress on shaft concrete shall be33% of the 28-day strength, but not exceeding1,600 psi (11.0 MPa). The maximum allowabledesign stress on permanent steel casing, if at least1/10-inch (2.5 mm) thick, and on steel reinforcingshall be 40% of the minimum specified yieldstrength, but not exceeding 24,000 psi (165 Mpa).

1810.2.3 Installation. Enlarged bases formedeither by compacting concrete or driving a precastbase shall be formed in or driven into granularsoils. Piles shall be constructed in the samemanner as successful prototype test piles drivenfor the project. Pile shafts extending through peator other organic soil shall be encased in apermanent steel casing. Where a cased shaft isused, the shaft shall be adequately reinforced toresist column action or the annular space aroundthe pile shaft shall be filled sufficiently to re-establish lateral support by the soil. Theinstallation of enlarged base piles havingcompacted concrete bases shall fulfill thefollowing requirements:

1810.2.3.1 Base.

1. The enlarged base shall be formed on orin bearing materials of Classes 1 to 9inclusive. The Class 9 material (fine sand)shall have a maximum of 15% by weightfiner than the No. 200 mesh sieve and shallbe non-plastic, unless satisfactory load testresults or other substantiating data aresubmitted to, and approved by, the buildingofficial.2. The compacted concrete placement shallbe in measured batches, to establish impact




energy required per unit volume of concrete. Aminimum of one Standard Batch Volume ofconcrete, as defined in Table 1810.4, shall beinjected in the base, after expulsion of the concreteplug or boot used to close the tube during the drivingprocess.

1810.2.3.2 Shaft Installation.

1810.2.3.2.1 Uncased Compacted-concreteShaft.

1. Concrete shall be placed at zeroslump, in small batches, and shall becompacted in place in a controlledmanner as the drive-tube is withdrawn.2. Enlarged base piles formed throughsoils of Classes 10 and 11, located lessthan nine feet or within the heave rangefrom an uncased shaft, shall be pre-drilled through such soil.3. An uncased compacted-concrete shaftshall not be formed through very soft tosoft soils of Classes 10 and 11. Thebuilding official may waive thisrequirement based upon satisfactoryevidence prepared by a registered designprofessional that the soil has sufficientstrength for proper shaft construction.4. A suitable method shall be employedby the contractor and the designprofessional to verify and record that theentire length of the shaft is completelyfilled with concrete. Such means shallinclude the ability to determine theincremental volume of concrete installedin relation to the calculated shaft volume.

1810.2.3.2.2 Uncased High-slumpConcrete Shaft.

1. Concrete shall be placed at not lessthan eight-inch slump, except that slumpas low as four inches may be allowed ifadequate vibration is applied to the drive-tube during the entire withdrawalprocess. During withdrawal, the level ofconcrete within the tube shall have apositive differential head over externalsoil and water pressures at all times.2. The shaft shall be provided with full-length reinforcing steel anchored in theenlarged base. At a minimum, provide acage with four, full length, number fivereinforcing bars evenly spaced near theshaft perimeter.3. Enlarged base piles located less thannine feet (2.7 m) from a completeduncased high-slump shaft shall not beinstalled until at least 12 hours after shaftpour.

4. A suitable method shall be employedby the contractor and the designprofessional to verify and record that theentire length of the shaft is completelyfilled with concrete. Such means shallinclude the ability to determine theincremental volume of concrete installedin relation to the calculated shaft volume.

1810.2.3.2.3 Cased Shaft. The permanentmetal casing shall be fastened to theenlarged base in such a manner that the twowill not separate.

1810.2.4 Load-bearing Capacity. Load-bearingcapacity shall be verified by load tests inaccordance with 780 CMR 1808.2.8.2.4.

1. For enlarged base piles with compactedconcrete bases and loads up to 120 tons, theallowable load may be computed by thefollowing formula:

R = [(B x E)/C] V 2/3

where:R = allowable load in pounds;B = average number of blows required to injectone cubic foot of concrete, during injection of thelast batch;E = Energy per blow in foot-pounds;C = constant; andV = total volume of base concrete in cubicfeet.

The values of R, E, and C shall conform toTable 1810.2.4 unless other values aredetermined by load test, in which case the lattervalues shall control. Use of Table 1810.2.4 islimited by the provisions of 780 CMR1808.2.8.2.2.

The value of V shall include an allowance ofone Standard Batch Volume of concrete, ifconcrete is used in the tube during the drivingprocess, plus the additional volume of concreteinjected during formation of the base.2. During injection of the last batch ofconcrete in the base, the height of concretewithin the drive tube shall not be more than aof the drive-tube inside diameter.

TABLE 1810.2.4

R

(tons)

Energy, E

(foot-pounds)C

Standard Batch

Volume

(cubic feet)

over 100 140,000 18 5

51 to 100 100,000 18 5

25 to 50 60,000 30 2




1810.2.5 Concrete Cover. The minimumconcrete cover shall be 2½ inches (64 mm) foruncased shafts and one inch (25 mm) for casedshafts.

1810.2.6 Seismic Reinforcement. Where astructure is assigned to Seismic Design CategoryC or D in accordance with 780 CMR 1616.0, thecorresponding requirements of 780 CMR1810.1.2.1 and 1810.1.2.2 shall be met.

1810.2.7 Spacing. The center-to-center spacingwith uncased shafts shall be not less than 2.5times the outside diameter of the drive tube andnot less than 3.5 feet. The center-to-centerspacing with cased shafts shall be not less than 3.0times the shaft diameter.

1810.2.8 Loading on Underlying Strata.Where the bearing stratum is underlain by weakermaterial, or if the bearing stratum becomesweaker with depth, the vertical pressure on theunderlying weaker material shall not exceed theallowable bearing pressure of the weaker materialdetermined in accordance with 780 CMR 1804.3.The vertical pressure can be computed byassuming that the load is spread uniformly at anangle of 30 degrees with the vertical, starting at apolygon circumscribing the pile or pile group atthe junction of the shaft and enlarged base, but notextending beyond intersecting 30 degree planesfrom adjacent piles or pile groups.

1810.3 Augered Uncased Piles. Augered uncasedpiles shall conform to 780 CMR 1810.3.1 through1810.3.5.

1810.3.1 Allowable Stresses. The designstresses shall not exceed the following values:

1. For compression loads. The maximumallowable design stress on the cement grout orconcrete shall be 33% of the specified 28- dayunconfined compressive strength, but notexceeding 1,600 psi (11.0 MPa). Themaximum allowable design stress on the steelreinforcing shall be 40% of the minimumspecified yield strength, but not exceeding24,000 psi (165 MPa).2. For tension loads. The maximum allowabledesign tensile stress on the steel reinforcingshall be 60% of the minimum specified yieldstrength. The allowable design tensile stress onthe cement grout shall be zero.

1810.3.2 Dimensions. An augered uncased pileis defined as a structural member installedutilizing a hollow-stem auger no less than 12inches (305 mm) in outside diameter whichextends to satisfactory bearing materials todevelop support by end bearing and/or friction inthose materials. The design pile diameter shall betaken as the outside diameter of the hollow stemauger. The minimum center-to-center spacingbetween adjacent piles shall not be less than 30

inches (760 mm) or two times the pile diameter,whichever is greater. In addition, for groups offriction piles, the overall circumference of a pilegroup shall exceed the sum of the circumferencesof all of the individual piles within the group.

1810.3.3 Installation. Augered uncased pilesshall be formed by advancing a closed-endcontinuous-flight hollow-stem auger of uniformdiameter through unsuitable material and into asatisfactory bearing material followed by removalof the tip closure and pumping cement grout orconcrete through the hollow-stem while thehollow-stem auger is extracted. During advance-ment, the hollow-stem auger shall be rotatedrapidly such that the material through which theauger is being advanced is removed by the augerflights and is not displaced laterally by the auger.During withdrawal, if the hollow stem auger isrotated, it shall be rotated in a positive(advancing) direction.

1. The grout or concrete shall be pumpedunder continuous pressure and in onecontinuous operation. Grout or concrete pumppressures shall be measured and maintained atall times sufficiently high to offset hydrostaticand lateral earth pressures. The rate ofwithdrawal of the auger shall be carefullycontrolled to exclude all foreign matter andensure that the augered hole is completelyfilled with grout or concrete as the auger iswithdrawn. The actual volume of grout orconcrete pumped into each hole shall be equalto, or greater than, the theoretical volume of theaugered hole.2. If the grouting or concreting process of anypile is interrupted, or a loss of concretingpressure occurs, the pile shall be redrilled to itsoriginal depth plus six inches (152 mm) (unlessbearing on rock) and filled from the bottom.3. Augered uncased piles shall not be installedwithin six pile diameters (center-to-center) ofa pile filled with grout or concrete less than 24-hours old except where approved by theregistered design professional.

1810.3.3.1 Records. The owner shall engagea registered design professional to monitor theinstallation of augered uncased piles inaccordance with 780 CMR 1808.2.22. Thedesign professional or his representative shallmake an accurate record of the installationequipment used, pile dimensions, grout orconcrete volumes, reinforcement, interruptionsor delays in pile installation, and all otherpertinent installation data.

1810.3.3.2 Instrumentation. The continuous-flight auger rig utilized to install augereduncased piles shall be equipped with datalogging equipment that automatically monitorsand produces a real-time printout of depth,




grout or concrete pressure, grout or concrete flow,and rate of auger withdrawal. The automaticmonitoring equipment shall immediately indicate tothe equipment operator, and record on the printedrecord, any instance during the withdrawal of thehollow-stem auger where the rate of augerwithdrawal times the theoretical pile cross-sectionalarea exceeds the rate of grout or concrete placement.Printed instrumentation readout for each pile shall beprovided to the design professional's representativeupon completion of each pile.

1810.3.4 Reinforcement. Where full lengthlongitudinal steel reinforcement is placed withoutlateral ties, the reinforcement shall be placedthrough the hollow stem of the auger prior tofilling the pile with concrete. All pilereinforcement shall have a concrete cover of notless than 2.5 inches (64 mm).

Exception. Where physical constraints do notallow the placement of the longitudinalreinforcement prior to filling the pile withconcrete or where partial length longitudinalreinforcement is placed without lateral ties, thereinforcement is allowed to be placed after thepiles are completely concreted but whileconcrete is still in a semi-fluid state.

1810.3.5 Seismic Reinforcement. Where astructure is assigned to Seismic Design CategoryC or D in accordance with 780 CMR 1616.0, thecorresponding requirements of 780 CMR1810.1.2.1 and 1810.1.2.2 shall be met.

1810.4 Driven Uncased Piles. No provisions.

1810.5 Steel-cased Piles. Steel-cased piles shallcomply with the requirements of 780 CMR 1810.5.1through 1810.5.4.

1810.5.1 Materials. Pile shells or casings shallbe of steel and shall be sufficiently strong to resistcollapse and sufficiently watertight to exclude anyforeign materials during the placing of concrete.Steel shells shall have a sealed tip with a diameterof not less than eight inches (203 mm). Concreteshall satisfy the provisions of 780 CMR 1810.1.1.The shape of the pile may be cylindrical, orconical, or a combination thereof, or it may be asuccession of cylinders of equal length, with thechange in diameter of adjoining cylinders notexceeding one inch.

1810.5.2 Allowable Stresses. The allowabledesign compressive stress in the concrete shall notexceed 33% of the 28-day specified compressive

cstrength (f’ ), nor 1,600 psi (11.0 MPa). Theallowable concrete compressive stress shall be

c0.40 (f’ ) for that portion of the pile meeting thefollowing conditions.

1810.5.2.1 Shell Thickness. The thickness ofthe steel shell shall not be less than manufac-turer’s standard gage No. 14 gage (0.068 inch)

(1.75 mm) minimum.

1810.5.2.2 Shell Type. The shell shall beseamless or shall be provided with seams ofstrength equal to the basic material and be of aconfiguration that will provide confinement tothe cast-in-place concrete.

1810.5.2.3 Strength. The ratio of steel yield

ystrength (f ) to 28-day specified compressive

cstrength (f?’ ) shall not be less than six.

1810.5.2.4 Diameter. The nominal pilediameter shall not be greater than 16 inches(406 mm).

The load on cased poured concrete pilesshall be applied to the cross-sectional areacomputed on the following basis:

1. For metal-cased piles driven to and intomaterials of Classes 1 through 4, using thediameter measured one foot (0.3 m) abovethe point, except that when the rock isimmediately overlain by a bearing stratumconsisting of one or a combination ofbearing materials of Classes 5, 6, and 7,using the diameter at the surface of thebearing stratum.2. For metal-cased piles, driven throughcompressible materials including Classes 10and 11 and into a bearing stratum consistingof one or a combination of bearing materialsof Classes 5 through 9, using the diameter atthe surface of the bearing stratum.

1810.5.3 Installation. Steel shells shall bemandrel-driven their full length in contact withthe surrounding soil.

Steel shells shall be driven in such order andwith such spacing as to ensure against distortionof or damage to piles already in place. A pileshall not be driven within four and one-halfaverage pile diameters of a pile filled withconcrete less than 24 hours old unless approvedby the registered design professional. Concreteshall not be placed in steel shells within heaverange of driving. The requirements of 780 CMR1810.1.3 shall apply.

1810.5.4 Reinforcement. Reinforcement shallnot be placed within one inch (25 mm) of the steelshell. Reinforcing shall be required forunsupported pile lengths or where the pile isdesigned to resist uplift or unbalanced lateralloads.

1810.5.4.1 Seismic Reinforcement. Where astructure is assigned to Seismic DesignCategory C or D in accordance with 780 CMR1616.0, the corresponding requirements of780 CMR 1810.1.2.1 and 1810.1.2.2 shallapply.




1810.6 Concrete-filled Steel Pipe and Tube Piles.Concrete-filled steel pipe and tube piles shallconform to the requirements of 780 CMR 1810.6.1through 1810.6.5.

1810.6.1 Materials. Steel pipe and tube sectionsused for piles shall conform to ASTM A 252 or A283. Concrete shall conform to 780 CMR1810.1.1. The maximum coarse aggregate sizeshall be 0.75 inch (19.1 mm).

1810.6.2 Allowable Stresses. The allowabledesign compressive stresses shall not exceed thevalues indicated in 780 CMR 1810.6.2.1 through1810.6.2.3.

1810.6.2.1 Top Driven Piles. The allowabledesign compressive stress in the concrete shallnot exceed 25% of the 28-day compressivestrength of the concrete or 1,100 psi (7.6 MPa),whichever is smaller. The maximum allowablecompressive stress in the steel shall not exceed9,000 psi (62 Mpa).

1810.6.2.2 Mandrel Driven Piles. For pilesinstalled with mandrels which transmit drivingstresses directly to the bottom of the steel pipe,the allowable design compressive stress in theconcrete shall not exceed 33% of the 28-dayspecified compressive strength. The allowabledesign compressive stress in the steel shall notexceed 35% of the minimum specified yieldstrength of the steel.

1810.6.2.3 The maximum allowable designstress in the steel shall be limited to 50% of theminimum specified yield strength where higherstresses are substantiated in accordance with780 CMR 1808.2.10.

1810.6.3 Minimum Dimensions. Piles shall havea nominal outside diameter of not less than 8inches (203 mm) and a minimum wall thicknessin accordance with 780 CMR 1809.3.4. Formandrel-driven pipe piles, the minimum wallthickness shall be 0.1 inch (2.5 mm).

1810.6.4 Reinforcement. Reinforcement steelshall conform to 780 CMR 1810.1.2. Reinforce-ment shall not be placed within 1 inch (25 mm) ofthe steel casing.

1810.6.4.1 Seismic Reinforcement. Where astructure is assigned to Seismic DesignCategory C or D in accordance with 780 CMR1616, the following shall apply. Minimumreinforcement no less than 0.01 times the cross-sectional area of the pile concrete shall beprovided in the top of the pile with a lengthequal to two times the required cap embedmentanchorage into the pile cap, but not less thanthe tension development length of thereinforcement. The wall thickness of the steelpipe shall not be less than 0.188 inch (4.75mm).

1810.6.5 Placing Concrete. The placement ofconcrete shall conform to 780 CMR 1810.1.3.

1810.7 Caisson Piles. Caisson piles shall conformto the requirements of 780 CMR 1810.7.1 through1810.7.8.

1810.7.1 Construction. Caisson piles shallconsist of a shaft section of concrete-filled pipeextending to bedrock of Classes 1 or 2 with anuncased socket drilled into the bedrock and filledwith concrete. The caisson pile shall have a full-length structural steel core or a stub core installedin the rock socket and extending into the pipeportion a distance equal to the socket depth.

1810.7.2 Materials. Pipe and steel cores shallconform to the material requirements in 780 CMR1808.3. Pipes shall have a minimum wallthickness of 0.375 inch (9.5 mm) and shall befitted with a suitable steel-driving shoe welded tothe bottom of the pipe. Concrete shall have a 28-

cday specified compressive strength (f‘ ) of not lessthan 4,000 psi (27.58 MPa). The concrete mixshall be designed and proportioned so as toproduce a cohesive workable mix with a slump offour inches (102 mm) to six inches (152 mm).

1810.7.3 Design. The depth of the rock socketshall be sufficient to develop the full load-bearingcapacity of the caisson pile with a minimum safetyfactor of two, but the depth shall not be less thanthe outside diameter of the pipe. The design ofthe rock socket is permitted to be predicated onthe sum of the allowable load-bearing pressure onthe bottom of the socket plus bond along the sidesof the socket. The socket design stress shall bedetermined by a registered design professionalbased upon foundation investigation study inaccordance with 780 CMR 1802, but in no casewill the design bond stress on the perimeter of thesocket exceed 200 psi. Load tests, in accordancewith 780 CMR 1808.2.8.2.4, may be required iffoundation investigation data are judgedinsufficient by the registered design professionalto verify the selected bond stress.

The minimum outside diameter of the caissonpile shall be 18 inches (457 mm), and the diameterof the rock socket shall be approximately equal tothe inside diameter of the pile.

1810.7.4 Structural Core. The gross cross-sectional area of the structural steel core shall notexceed 25% of the gross area of the caisson. Theminimum clearance between the structural coreand the pipe shall be two inches (51 mm). Wherecores are to be spliced, the ends shall be milled orground to provide full contact and shall be full-depth welded.

1810.7.5 Allowable Stresses. The allowabledesign compressive stresses shall not exceed the

c yfollowing: concrete, 0.33 f’ ; steel pipe, 0.35 F ;

yand structural steel core, 0.50 F .




1810.7.6 Installation. The rock socket and pileshall be thoroughly cleaned of foreign materialsbefore filling with concrete. Steel cores shall bebedded in cement grout at the base of the rocksocket. Concrete shall not be placed throughwater except where a tremie or other approvedmethod is used.

1810.7.7 Seismic Reinforcement. Caisson pilesshall meet the seismic reinforcement requirementsof 780 CMR 1810.6.4.1.

1810.7.8 Spacing. The minimum center to centerspacing shall be not less than 2.5 times the outsidediameter of the steel shell.

1810.8 Small Diameter Grouted Piles.

1810.8.1 General. 780 CMR 1810.8 coversgrouted cast-in-place piles which are less than 12inches (305 mm) in diameter and in which all ora portion of the pile is cast directly against the soilwithout permanent casing.

1810.8.2 Materials. Concrete or sand-cementgrout shall satisfy the provisions of 780 CMR1810.1.1.

1810.8.3 Allowable Stresses. The design stressesshall not exceed the following values:

1. For compression loads. The maximumallowable design stress on the cement grout orconcrete shall be 33% of the specified 28- dayunconfined compressive strength, but notexceeding 1,600 psi (11.0 MPa). Themaximum allowable design stress on the steelreinforcing, including permanent steel casing,shall be 40% of the minimum specified yieldstrength. Where the design of the pile crosssection includes compression on grout that isnot confined within a permanent steel casing orbedrock, the allowable stress on the steel shallnot exceed 24,000 psi (165 MPa).2. For tension loads. The maximumallowable design tensile stress on the steelreinforcing shall be 60% of the minimumspecified yield strength. The allowable designtensile stress on the cement grout shall be zero.

1810.8.4 Minimum Reinforcing. The steelreinforcing shall be designed to carry thefollowing minimum percentage of the designcompression load:

1. For a pile or a portion of a pile that isgrouted inside a drilled temporary casing or apermanent casing, grouted inside a hole drilledinto stable rock, or grouted with a hollow-stemauger, the reinforcing steel shall be designed tocarry not less than 40% of the designcompression load.2. For a pile or a portion of a pile that isgrouted in an uncased drill hole in materialsother than stable rock, or grouted in a driventemporary casing, the pile shall be designed to

carry the entire design compression load on thereinforcing steel.

Exception. Where a portion of the cementgrout is placed and permanently enclosedwithin permanent steel casing or reinforcingconsisting of steel pipe, that portion may beincluded at the allowable stress for thegrout.

1810.8.5 Load Test. For all design loads, theallowable load shall be determined by load tests inaccordance with 780 CMR 1808.2.8.2.4. Loadtests may be waived by the code official based onsubstantiating data and analyses prepared by aregistered design professional.

1810.8.5.1 Alternative Load Test Procedurefor Friction Piles. For piles designed asfriction piles, the friction capacity incompression may be verified by load testing intension. The tension load test shall beperformed in accordance with 780 CMR1808.2.8.2.6.

Exceptions:1. The test pile must be cased or leftungrouted down to the top of the bearingstratum in a manner which will ensure thatno friction resistance is developed abovethe bearing stratum.2. The maximum design load shall betaken as 50% of the applied test load whichresults in a movement under load of 0.5 inch(13 mm) at the pile tip. The movement atthe pile tip shall be:

(a) measured directly by a tell-tale or(b) computed by deducting the theoreti-cal elastic elongation of the pile from thedisplacement measured at the top of thepile.

1810.8.6 Installation. The pile may be formed ina hole advanced by rotary or rotary percussivedrilling methods (with or without temporarycasing), by a hollow-stem auger, or by driving atemporary casing. The pile shall be grouted witha fluid cement grout. The grout shall be pumpedthrough a tremie pipe extending to the bottom ofthe pile until grout of suitable quality returns atthe top of the pile. The following requirementsapply to specific installation methods:

1. Piles grouted with temporary casing. Forpiles grouted inside a temporary casing, thereinforcing steel shall be inserted prior towithdrawal of the casing. The casing shall bewithdrawn in a controlled manner with thegrout level maintained at the top of the pile, toensure that the grout completely fills the drillhole. During withdrawal of the casing, thegrout level inside the casing shall be monitoredto check that the flow of grout inside the casingis not obstructed.




2. Piles grouted without temporary casing.For a pile or portion of a pile grouted in anopen drill hole in soil without temporarycasing, the minimum design diameter of thedrill hole shall be verified by a suitable deviceimmediately prior to grouting. The reinforcingsteel shall be inserted prior to grouting.3. Piles grouted with hollow-stem augers. Forpiles installed with a hollow-stem auger, thegrout shall be pumped under continuouspressure, and the rate of withdrawal of theauger shall be carefully controlled to ensurethat the hole is completely filled with grout asthe auger is withdrawn. The actual volume ofgrout pumped for each 1.0 foot (305 mm) ofwithdrawal of the auger shall be recorded andmust be equal to or greater than the theoreticalvolume. The reinforcing steel shall be insertedprior to withdrawal of the auger.4. For piles designed for end bearing, asuitable means shall be employed to verify thatthe bearing surface is properly cleaned prior togrouting.5. Subsequent piles shall not be drilled ordriven near piles that have been grouted untilthe grout has had sufficient time to harden.

1810.8.7 Pile Diameter. The design pile diametershall be taken as:

1. The outside diameter of the temporarycasing; or2. The diameter of a full circumferential drillbit attached to the bottom of the temporarycasing; or3. The outside diameter of the hollow-stemauger; or4. The borehole diameter verified by suitablemeasurements made immediately prior togrouting.

1810.8.8 Corrosion Protection.

1. Where steel reinforcing is not enclosedinside a permanent casing, centralizers shall beprovided on the reinforcing to ensure aminimum grout cover of 1.0 inch (25 mm) insoil and 0.5 inch (13 mm) in rock. Grout coverrequirements may be reduced when thereinforcing steel is provided with a suitableprotective coating.2. Permanent steel casing that is used asstructural reinforcing shall be protected inaccordance with the provisions of 780 CMR1808.2.17.3. For piles subjected to sustained tensionloading in corrosive environments, thereinforcing steel shall be protected by a suitableprotective coating or encapsulation method.

1810.8.9 Buckling. For piles that extend throughmore than five feet of soft soil of Material Classes10 or 11 using a solid bar section for the steelreinforcing, the lateral support assumptions of

780 CMR 1808.2.9.1 shall not apply if any of thefollowing conditions exist:

1. Steel designed for an allowable stressgreater than 24,000 psi.2. Outside diameter of the grout less than fourtimes the diameter of the steel reinforcing bar3. Soil shear strength less than 200 psfFor these conditions, the potential for buckling

in the soft soil zone shall be investigated.

780 CMR 1811.0 COMPOSITE PILES

1811.1 General. Composite piles shall conform tothe requirements of 780 CMR 1811.2 through1811.5.

1811.2 Design. Composite piles consisting of twoor more approved pile types shall be designed tomeet the conditions of installation.

1811.3 Limitation of Load. The maximumallowable load shall be limited by the capacity of theweakest section incorporated in the pile.

1811.4 Splices. Splices between concrete and steelor wood sections shall be designed to preventseparation both before and after the concrete portionhas set, and to ensure the alignment and transmissionof the total pile load. Splices shall be designed toresist uplift caused by upheaval during driving ofadjacent piles, and shall develop the full compressivestrength and not less than 50% of the tension andbending strength of the weaker section.

1811.5 Seismic Reinforcement. Where a structureis assigned to Seismic Design Category C or D inaccordance with 780 CMR 1616.0, the followingshall apply. Where concrete and steel are used aspart of the pile assembly, the concrete reinforcementshall comply with that given in 780 CMR 1810.1.2.1and 1810.1.2.2 or the steel section shall comply with780 CMR 1810.6.4.1 or 1810.3.5.

780 CMR 1812. PIER FOUNDATIONS

1812.1 General. Isolated and multiple piers used asfoundations shall conform to the requirements of780 CMR 1812.2 through 1812.10, as well as theapplicable provisions of 780 CMR 1808.2.

1812.2 Design. Foundation piers may be designedas concrete columns with continuous lateral supportbelow the soil level. The unit compressive stress inthe concrete shall not exceed 33% of the 28-daystrength of the concrete or 1,600 psi (11.0 MPa),whichever is less. The unit compressive stress in thesteel reinforcement or the permanent steel casingshall not exceed 40% of the yield strength of thesteel or 24,000 psi (165 MPa), whichever is less.Permanent steel casing which is used as structuralreinforcement shall be protected against corrosion inaccordance with 780 CMR 1808.2.17.




1812.3 Materials. Concrete shall have a 28-day

cspecified compressive strength (f’ ) of not less than2,500 psi (17.24 MPa). Where concrete is placedthrough a funnel hopper at the top of the pier, theconcrete mix shall be designed and proportioned soas to produce a cohesive workable mix having aslump of not less than four inches (102 mm) and notmore than six inches (152 mm). Where concrete isto be pumped, the mix design including slump shallbe adjusted to produce a pumpable concrete.

1812.4 Reinforcement. Except for steel dowelsembedded five feet (1524 mm) or less in the pier,reinforcement where required shall be assembled andtied together and shall be placed in the pier hole as aunit before the reinforced portion of the pier is filledwith concrete.

Exception. Reinforcement is permitted to be wetset and the 2.5 inch (64 mm) concrete coverrequirement be reduced to 2 inches (51 mm) forGroup R, Division 3 and Group U, Division 1occupancies not exceeding two stories of light-frame construction, provided the constructionmethod can be demonstrated to the satisfaction ofthe building official.

1812.4.1 Seismic Reinforcement. Where astructure is assigned to Seismic Design CategoryC or D in accordance with 780 CMR 1616, thecorresponding requirements of 780 CMR1810.1.2.1 and 1810.1.2.2 shall be met. Theminimum longitudinal reinforcement ratio shall beapplied to the minimum design cross-sectionalarea determined in accordance with 780 CMR1812.2.

Exceptions:1. Isolated piers supporting posts of Group R,Division 3 and Group U, Division 1occupancies not exceeding two stories of light-frame construction is permitted to be reinforcedas required by rational analysis but not lessthan a minimum of one No. 4 bar, without tiesor spirals, when detailed so the pier is notsubject to lateral loads and the soil isdetermined to be of adequate stiffness.2. Isolated piers supporting posts and bracingfrom decks and patios appurtenant to Group R,Division 3 and Group U, Division 1occupancies not exceeding two stories of light-frame construction may be reinforced asrequired by rational analysis but not less thanone No. 4 bar, without ties or spirals, when thelateral load, E, to the top of the pier does notexceed 200 pounds (890 N) and the soil isdetermined to be of adequate stiffness.3. Piers supporting the concrete foundationwall of Group R, Division 3 and Group U,Division 1 occupancies not exceeding twostories of light-frame construction is permittedto be reinforced as required by rational analysisbut not less than two No. 4 bars, without ties or

spirals, when it can be shown the concrete pierwill not rupture when designed for the

mmaximum seismic load E , and the soil isdetermined to be of adequate stiffness.4. Closed ties or spirals where required by780 CMR 1810.1.2, are permitted to be limitedto the top 3 feet (914 mm) of the piers 10 feet(3048 mm) or less in depth supporting GroupR, Division 3 and Group U, Division 1occupancies of Seismic Design Category D, notexceeding two stories of light-frameconstruction.

1812.5 Concrete Placement. Concrete may bedropped into the pier from the ground surfaceprovided no more than 3.0 inches (76 mm) of waterremains in the bottom and the concrete will free-fallvertically without obstruction. The concrete shall beplaced in a rapid, continuous operation andcontrolled such that the concrete does not segregate.

1. No piers shall be installed near a concretedpier until the concrete has set sufficiently to avoiddamage to the concreted pier.2. For piers without belled bases, concrete orgrout may be placed through still water or slurry.A properly operated tremie or pumping methodshall be used. Samples of the slurry shall betested to determine the properties prior to placingconcrete in each pier. The quality, consistency,and density of the slurry shall be controlled toensure that there will be free-flow of concretefrom the tremie pipe. The concrete must beplaced such that all water, slurry and contaminatedconcrete below design cutoff level is displaced.3. For piers with belled bases, the concrete maybe placed under slurry, based upon therecommendations of a registered designprofessional and with the approval of the buildingofficial. The specific soil or rock conditions,equipment and procedures used shall be taken intoaccount.4. A suitable method shall be employed to verifythat the entire length of the shaft is completelyfilled with concrete. Such means shall include theability to determine the incremental volumes ofconcrete installed in relation to calculated shaftvolume.

1812.6 Belled Bases. Where pier foundations arebelled at the bottom, the edge thickness of the bellshall not be less than four inches (102 mm). Wherethe sides of the bell slope at an angle less than 60degrees (1 rad) from the horizontal, the effects ofvertical shear shall be considered.

1812.7 Laterally Unsupported Piers. Whereadequate lateral support is not provided, and theunsupported height to least lateral dimension doesnot exceed three, piers of plain concrete shall bedesigned and constructed as pilasters in accordancewith ACI 318. Where the unsupported height toleast lateral dimension exceeds three, piers shall be




constructed of reinforced concrete, and shallconform to the requirements for columns in ACI318.

Exception. Where adequate lateral support isfurnished by the surrounding materials as definedin 780 CMR 1808.2.9, piers are permitted to beconstructed of plain or reinforced concrete. Therequirements of ACI 318 for bearing on concreteshall apply.

1812.8 Steel Shell. Where concrete piers areentirely encased with a circular steel shell, and thearea of the shell steel is considered reinforcing steel,the steel shall be protected under the conditionsspecified in 780 CMR 1808.2.17. Horizontal jointsin the shell shall be spliced to comply with780 CMR 1808.2.7.

1812.9 Installation. Where piers are carried todepths below water level, the piers shall beconstructed by a method that will ensure accuratepreparation and inspection of the bottom, and thedepositing or construction of sound concrete. Inunstable soils, temporary casing or slurry shall beused to stabilize the excavation. When slurry is usedto stabilize the excavation, the level and quality ofthe slurry shall be monitored and controlled to

maintain stability of the shaft and the bearingsurface.

1812.10 Alignment. When the center of the crosssection of a foundation pier at any level deviatesfrom the resultant of all forces more than 2 % of itsheight, or more than 10% of its diameter, it shall bereinforced as provided in ACI 336. The restrainingeffect of the surrounding soil may be taken intoaccount.

1812.11 Minimum Spacing. The minimum center-to-center spacing between adjacent piers designedfor friction support shall be not less than 2.0 timesthe shaft diameter.

1812.12 Special Provisions. For piers with shaftdiameter less than 24 inches (610 mm), thefollowing special provisions shall apply:

1. For piers with temporary casing extending tothe bottom, the concrete may be poured from thetop in accordance with 780 CMR 1812.5.2. For all other cases, piers shall be filled fromthe bottom upward through a tremie or concretepump tube in accordance with 780 CMR1812.5(2).

780 cmr 18.00 foundations and retaining walls · foundations and retaining walls 8/22/08 (effective...

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