prof. samuel g. paikowsky - faculty server...

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Prof. Samuel G. Paikowsky

Lecture 2 - SUBSURFACE EXPLORATION AND SOIL PARAMETERS

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Geotechnical Engineering Research LaboratoryUniversity of Massachusetts Lowell

USA

14.528 Drilled Deep FoundationsSpring 2014

Prof. Samuel G. Paikowsky

Lecture 2 – Part II – Subsurface Explorations and Design Parameters

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Geotechnical Engineering Research LaboratoryUniversity of Massachusetts Lowell

USA

14.528 Drilled Deep FoundationsSpring 2014

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14.528 Drilled Deep Foundations – Samuel Paikowsky 3 of 235

Soil Origin and Deposition (Basic Review)

N.E. Geology (Basic Review)

Subsurface Exploration

In-Situ Testing

Design Parameters

Lecture Subjects


OBJECTIVES OF SUBSURFACE EXPLORATION

Three General Objectives for Subsurface Exploration:

1. Define Soil and Rock Stratigraphy and Structure within Proposed Construction Zone of Influence.

2. Obtain Groundwater Data.- Level at Time of Testing.- Seasonal Fluctuations.

3. Determine Engineering Properties of Subsurface Materials for Use in Foundation Design.

- Collect samples for laboratory testing.- Determine insitu engineering properties.

Photograph courtesy of www.cmeco.com

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Subsurface Exploration

Subsurface Exploration Plan:Function of

- Type and Critical Nature of Structure- Foundation Loads- Topographical Information- Site Geology (Soil and Rock Formations)- Location of Bedrock

• 1.5 m core to confirm• >3 m core required for foundations

on rock- Engineer’s Experience- Project Requirements

Consequences of Poor Subsurface Explorations

(photographs courtesy of NHI 13231)

USACE EM1110-1-1804“There are no hard and fast rules stating the number and depth of samples for a particular geotechnical investigation.”ASTM D420-98(2003) Standard Guide to Site Characterization for

Engineering, Design, and Construction Purposes

PLANNING


Are Soil Explorations as Costly as the Repair?(Photographs courtesy of http://www.dot.state.co.us/geotech/geotechphotos.cfm)

YOU WILL NEED 1 BORING TO 100 ft TO DETERMINESEISMIC SITE CLASSIFICATION FOR IBC 2006

Subsurface ExplorationPLANNING

IBC (2009) Section 1803.3.1 (8th Edition of MSBC)The scope of the soil investigation including the number and types of borings orsoundings, the equipment used to drill and sample, the in-situ testing equipment andthe laboratory testing program shall be determined by a registered designprofessional.

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The Massachusetts State Building Code(7th Edition)

780 CMR 1802.0 FOUNDATION AND SOILS INVESTIGATIONS

1802.5 Borings, Sampling and Testing. The scope of the subsurface

exploration, including the number and types of borings, soundings or test pits, the equipment used to drill and sample, the in-situ testing equipment and the laboratory testing program, shall be determined by a registered

design professional.Photograph courtesy of TTU Center for

Multidisciplinary Research in Transportation(www.depts.ttu.edu/techmrtweb)

Subsurface ExplorationPLANNING


Subsurface Explorations

Although the foundations are usually hidden from sight when the structure is complete, their performance has a profound effect on the overall performance of the structure.

Karl Terzaghi (1951) (1883-1963) has said: “On account of the fact that there is no glory attached to the foundations, and that the sources of success or failure are hidden deep in the ground, building foundations have always been treated as step-children, and their acts of revenge for the lack of attention can be very embarrassing”.

Pisa Tower (From "Soil Mechanics" by Lamb & Whitman (1969), Chapter 14, p. 201)

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Pisa Tower( "Soil Mechanics"

by Lamb & Whitman (1969), Chapter 14,

p. 201)


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Background

Investigation of the underground conditions at a site isprerequisite to the economical design of the substructureelements. The cost of site exploration ranges between 0.5 to1% of the total construction cost and it’s elimination comparedto the risk of subsequent damage and safety is false economy.The required knowledge depends on the structure type, whichcan be divided into 3 categories:

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I) Main function is interaction with the surrounding ground

Tunnel (liner)Main interest:

Load - deformation relations of the loaded interfacesSoil - Structure interaction

Sheet pile

Gravity

Retaining WallsFoundations

Shallow

Deep

Not to Scale



I) Structures constructed from earth: highway fills and approach embankments, earth and rockfill dams, backfill behind walls

Approach Embankment Dam

Main interest:Properties of the construction material to determine the action of the earth structure itself and soil-structure interaction.

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Background (cont’d.)

III) Structures of natural earth and rocks, e.g., natural slopes

Main interest:Knowledge of the properties of the natural materials in the natural state.



Type of Subsurface Information Required for Design1. Dimensions

Areal extend, depth and thickness of each identifiable soilstratum within a depth, which depends on the structures sizeand nature as well as type of predominant soil.

2. RockDepth to top of rock and character of the rock

3. GroundwaterLocation, fluctuation, possible artesian pressures and the flowregime

4. Engineering PropertiesIn situ properties of the soil and/or rock such as permeability,compressibility, and shear strength

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Obtaining Subsurface InformationTwo broad categories for exploration methods: Direct Method and Indirect Method

Indirect Methods: Geologic mapping Aerial photography Topographic map interpretation Existing data - geological reports, maps, etc. Hydrological information by US Corps. of Eng. - soils surveys, etc. Highway Dept. Manuals Records of flow, etc. Websites: Google Maps and satellite options, Google Earth ‘Typical’ conditions, e.g. the reference E.G. Johnson, “Geotechnical

Characteristics of the Boston Area”, Civil Engineering Practice, Journal of BSCE section ASCE, vol. 4, no. 1, Spring 1989, pp. 53-64.



Obtaining Subsurface Information (cont’d.)Two broad categories for exploration methods: Direct Method and Indirect Method

Direct Methods: Field reconnaissance including examination of exposed materials in

natural and man-made exposures Sounding and probing and in-situ monitoring during and after

construction Borings, test pits, trenches, shafts obtaining representative disturbed

and/or undisturbed samples of in-situ material Simple field tests - SPT and CPT for correlations with engineering

properties Field tests - vane shear test, seepage and water pressure, plate bearing

test, pile load test. Measuring directly the engineering properties of the in-situ materials.

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Subsurface ExplorationsMass Building Code Section 1802.0 Foundation Investigations (p.23 of Review & Codes Class Notes, Volume 1)

1802.1 Where required: Boring, tests, drill holes, coreborings or any combination shall be required for all structures exceptthe following, unless specifically required by the building official:

1. One and two family dwellings and their accessory buildings;2. Structures less than 35,000 cubic feet in gross volume; and3. Structures used for agricultural purposes.

The borings, test, pits or other soil investigations shall be adequate innumber and depth and so located to accurately define the nature ofany subsurface material necessary for the support of the structure.When it is proposed to support the structure directly on bedrock, thecode official shall require core borings to be made into the rock, orshall require other satisfactory evidence to prove that the structureshall be adequately founded on bedrock.



Mass Building Code Section 1802.0 Foundation Investigations (p.23 of Review & Codes Class Notes, Volume 1)

1802.2 Soil samples and boring reports: Samples of thestrata penetrated in test borings or test pits, representing the naturaldisposition and conditions at the site, shall be available forexamination by the code official. Wash or bucket samples shall not beaccepted. Duplicate copies of the results obtained from all boringsand of all test results or other pertinent soil data, shall be filed withthe code official

Note: Previous code specifically used the language of “borings plotted to a true relative elevation and to scale”.

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GENERAL SUBSURFACE INVESTIGATION METHODS

METHOD Abbrv. ASTM SAMPLING MAX. DEPTH (ft)

Hand Auger Borings HABD1452-07a

D4700-91(06)Yes Typ. 6 - 8

20 (w/difficulty)

Test/Excavation Pits TP None YesLimits of

equipment(Typ. 20 ft)

Soil Test Borings STB

D420-98(03)

D1452-07a

D4700-91(06)

Yes~ 300 ft

(dependent of

various factors)

Green – Near Surface : Red – Near and Deep

D420-98(2003) Standard Guide to Site Characterization for Engineering, Design, and Construction Purposes



HAND AUGER BORINGS (HAB)

Two Man OperationPhotograph courtesy of

http://cees.ou.edu/ugrad/reu/

Typical HAB Cross-SectionFigure courtesy of

WPC Engineering Inc.

• Requires Manual Labor.

• Typical Depths up to 6 to 8 ft.

• Standard Diameter: 3¼ in

(Other Diameters Available).

• Allows for soil samples (disturbed) to be collected for classification and laboratory testing (if desired).


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TEST/EXCAVATION PITS (TP)

• Requires Appropriate Construction Equipment (e.g. backhoe).

• Typical Depths up to 20 ft(limited by equipment).

• Pit size determined by needs.

• Allows for soil samples (disturbed) to be collected for classification and laboratory testing (if desired).

• Allows for greater examination of insitu soils by geotechnical engineers and engineering technicians.

Photographs courtesy of www.ees1.lanl.gov, photos.orr.noaa.gov, & www.kerrville.org



Failing Truck Mounted Rig CME750 All-Terrain Rig

SOIL TEST BORING (STB) RIGS

Photographs courtesy of FHWA NHI Course 132031 Subsurface Investigations


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MoDOT Track Mounted Rig

Water Boring from Barge for Bridge Crossing

Wireline Rig for Kaolin MinesMacon, GA


SOIL TEST BORING (STB) RIGSSubsurface Explorations


Near Shore Water Boring Using a Jack-up Barge

Photograph courtesy of www.Fugroconsultants.com

SOIL TEST BORING (STB) RIGSSubsurface Explorations

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Planning the Exploration Program

A. General

1. Methods are applicable for any structure or development. The difference is in the scope and detail.

2. Our focus is on exploration for buildings and structures where the cost per unit area is high = compact site. (In this class we refer mostly to shallow foundations).

3. Our aim is to obtain maximum amount of information at minimum cost. General rule of thumb, cost of exploration is .5 to 1.0% of total construction cost.

o Lower for large project, homogeneous subsurfaceo Higher for smaller project, highly varied subsurface



Planning the Exploration Program

A. General (cont’d.)

* It is justifiable to spend additional money on explorations and related testing as long as the savings in the construction cost on the basis of the obtained information are significantly greater, i.e., in some cases, no amount of detailed information may change the type, cost, or performance of the foundation.

High

Subsurface complexity

Low

large Project size small

highest

lowest

Relative cost of subsurface exploration as a function of project size and subsurface complexity

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Planning the Exploration Program (cont’d.)

B. Steps in Planning a Subsurface Exploration Program

1. Assemble all available information on the structure: dimensions, column spacing, type of structure, use of building, basement requirement, special architectural considerations (e.g., sensitive facade) and loads

Approximation of 10 KN/m2/floor 1 ton/ m2/floorColumn spacing 10 stories = 10 ton/m2

e.g.: spacing = 6x6m, Max column load = 36m2x(10 ton/ m2) = 360 tons

2. Assemble all available information on the site utilizing indirect methods, field reconnaissance, and available data from nearby structures, etc.





3. Preliminary site investigation (usually the only investigation on standard jobs)

From Stage 1: Loads concentrationFrom Stage 2: Possible subsurface conditionFrom 1+2 Possible foundation scheme

Establish: (i) if the possible foundation requires test pits and/or borings. (ii) the number and depth of the test pits and/or borings

4. Depth and Number of Explorationso Should always include the influence zone of the foundationo One boring, usually the first, should get more data like

extending it all the way to the bedrock (also in middle)

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Subsurface ExplorationsPlanning the Exploration Program (cont’d.)

B. Steps in Planning a Subsurface Exploration Program4. Depth and Number of Explorations

Depth of Borings

Rules of Thumbo D (3 to 4) M

M - smallest foundationdimension

o D (1.5 to 2) smaller dimensionof building

o D not less than 6m(for very. smallbuilding) to 15m

D1 = depth at which = 0.1 qcontact

Dep

th

′

v′

v′

qcontact

∆0.05





The smaller of D1 and D2 is used to approximate the minimum required depth of the boring (unless bedrock is encountered).

See Table on page 76 (text): Number of stories and width of building for boring depth.

Office Buildings and Hospitals (See equations 2.1, 2.2, 2.3, & 2.4)

Db = (10 to 20)S0.7 where Db (ft.) and S is No. of stories

10 for light steel or narrow concrete building and 20 for heavy steel or wide concrete building.

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example: S = 1, Db = 10 - 20S = 3, Db = 22 - 43S = 10, Db = 50-100

Spacing - Table 2.4, pg. 77 (text)

Multi-story 30-100ftOne-story 60-200ftHighways 800-1600ftSubdivisions 800-1600ftDams and Dikes 130-260ft

Lower values relate to complex subsurface and high values relate to homogeneous subsurface.




o The minimum is the number of borings that can be made in one drilling day, but try not less than 5 boreholes in the following configuration:

Uniform soil less borings and more physical properties

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5. Obtained Information: Stratification of soil (type and geometry), groundwater table (establish wells and piezometers for monitoring), rock or competent strata, sample recovery, field tests (usually SPT and/or vane tests)

Small sites - you should be present to alter requirements based on initial findings, undisturbed samples are not usually obtained.

6. Detailed or Additional site investigation Locating additional borings based on missing information or

design requirements Determine the need for additional sampling, especially

undisturbed samples Consider construction procedures


StructureFHWA

(NHI-01-031)

USACE(Table 2-4 EM1110-1-1804)

NAVFAC(DM7.01)

Min. # Spacing Min. # Spacing Min. # Spacing

Rigid Frame Structure 1 per 230m² 50 ft spacing

Low-Load Warehouse 4 @ Corners

Isolated Rigid Ftg < 2500ft² 2 @ O.C.

Isolated Rigid Ftg < 10,00ft² 3 around Per.

Houses – Subdivisions 1 per 8000m² 200 to 400 ft

Houses – Individual Lots 1 per lot

Bridge Piers1 (< 30m wide)

2 (> 30m wide)1

Retaining Walls 1 ≤ 60 m

Roads – 2 Lane ≤ 60 m 1 per 150 m @ CL

Roads – Multi Lane 1 per 75 m @ CL

Cuts and Embankments 1 ≤ 60 m

Culverts 1 60 to 120 m

Levees 6 to 12 m high 230 m100 to 200 ft

Levees 12 to 18 m high 150 m

Subsurface Test Layout General Guidelines


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SUBSURFACE TEST LAYOUT GUIDELINESSCDOT Geotechnical Design Manual (2010)

Foundation Type Min. Geotechnical Site Investigation Reference

Bridge Pile Foundation Minimum one testing location per bent1 Table 4-1

Bridge Single Foundation – Drilled Shaft Minimum one testing locations per foundation location Table 4-1

Bridge Multiple Foundation – Drilled Shaft2 Minimum two testing locations per bent location Table 4-1

Bridge Shallow Foundation – Founded on Soil Minimum three testing locations per bent location Table 4-1

Bridge Shallow Foundation – Founded on Rock Minimum two testing locations per bent location Table 4-1

Retaining Wall (within 150 of bridge abutment) Minimum one testing location at least every 75 ft Section 4.3.2

Retaining Wall (within 150 of bridge abutment) Minimum one testing location at least every 75 ft Section 4.3.2

Embankments Minimum one testing location at least every 500 ft Section 4.3.3

Cut Excavations Minimum one test locations every 300 ft along cut area Section 4.3.4

CulvertsMinimum one testing locations @ each end of culvert and at every 100 ft of new crossline culvert2

Section 4.3.5

Sound Barrier Walls Dependant on shallow or deep foundation used2 Section 4.3.6

Misc. Structures (Light poles, overhead signs) Minimum of one test location per foundation location Section 4.3.7

NOTES:1. Spacing between testing locations may be increased, but shall be approved prior to field operations and shall include justification.

Spacing may not exceed 100 ft.2. See SCDOT Geotechnical Manual for additional details.



Structure FHWA(NHI-01-031)

USACE(Table 2-4 EM111-1-1804)

Spread Footings

Lf ≤ 2B, Min. Depth = 2B Min. Depth = 1½B

(4.5m for houses or to unweathered rock)

Lf ≥ 5B, Min. Depth = 4B

2B < Lf < 5B, Extrapolate

Deep Foundations (Soil)Min. Depth = 6m below

anticipated foundation tip elevation

Min. Depth = 1½B of imaginary footing @ 2/3

expected pile depthDeep Foundations (Rock)

Min. Depth = 3m, 3D, or 2Bgroup

below foundation tip

Roadways Min. 2mMin. 3m below finished grade

(0.75m into rock)

Embankments/Culverts Min. 2x Embankment Height Height of Levee

Cuts Min. 5m below cut elevation

SUBSURFACE TEST DEPTH GUIDELINES

NOTE: B = Footing Width


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SUBSURFACE TEST DEPTH GUIDELINESSCDOT Geotechnical Design Manual (2010)

Foundation Type Minimum Depth Reference

Deep FoundationBorings shall extend below the anticipated pile or drilled shaft tip elevation a minimum of 20 ft or a minimum of 4 times the minimum pile group dimension, whichever is deeper.

Section 4.3.1

Bridge Shallow FoundationL ≤ 2B, Minimum test depth = 2BL ≥ 5B, Minimum test depth = 4B2B ≤ L ≤ 5B, Minimum test depth = 3B

Table 4-2

Retaining WallsAt least 2X wall height beneath the anticipated bearing elevation or to auger refusal, whichever is shallower.

Section 4.3.2

EmbankmentsAt least 2X embankment height beneath the anticipated bearing elevation (i.e. to a depth sufficient to characterize settlement and stability issues) or to auger refusal, whichever is shallower.

Section 4.3.3

Cut ExcavationsAt least 25 feet below the anticipated bottom depth of the cut or to auger refusal, whichever is shallower.

Section 4.3.4

CulvertsAt least 2X the embankment height beneath the anticipated bearing elevation or in accordance with the bridge spread footing criteria, whichever is deeper (or auger refusal)

Section 4.3.5

Sound Barrier Walls Dependant on shallow or deep foundation used1 Section 4.3.6

Misc. Structures (Light poles, overhead signs)

Same depth criteria as specified for the bridge test locations for the same type of foundation.

Section 4.3.7

NOTES: 1. See SCDOT Geotechnical Manual for additional details.


TEST LOCATION PLAN (EXAMPLE)

Test Location Plan Example(Courtesy of Dr. Edward Hajduk and WPC Inc.)

Scale

Shows test locations relative to site

Symbol key differentiates between test types

Project Information

Other Useful Data:- North Arrow- Topographic Information


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EXAMPLE FOR SITE INVESTIGATION PLAN


Courtesy of G.Y.A., Ltd.


EXAMPLE FOR SITE INVESTIGATION PLAN (cont’d.)



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EXAMPLE FOR SITE INVESTIGATION PLAN (cont’d.)




Soil BoringsDefinition

A hole drilled in the ground (horizontal, vertically or inclined) for the primary purpose of obtaining samples of the overburden or rock materials present, in order to determine the stratigraphy and/or engineering properties of those materials. The hole may also be used for determination of engineering properties as permeability, shear strength, compressibility, etc.

Hollow stem auger used by a truck mounted rig

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Soil BoringsEquipment Used for Drilling Borings

Most common - continuous flight auger: mostly hollow (can be solid) stem augers, (see Figures 2.12-2.14 text pp. 79-80)

The hollow stem auger consists of:

1) seamless steel tube with a spiral flight to which are attached a finger type cutter head at the lower end and an adapter cap at the top, (see Figures 2.11 and 2.13) ID 2.5 to 6 inches (SPT O.D = 2 inches)

2) a center drill stem composed of drill rods which are attached with a drag bit at the lower end and an adapter at the top

Soil Borings Equipment Used for Drilling Borings


continuous flight auger

SPT outer Diam. = 2Sampling Tubes < 4

5ft typ.

InsideDiameter2½ – 6

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Soil BoringsEquipment Used for Drilling Borings

The adapters at the top of the drill stem and auger flight are designed to permit advancement of the auger with the plug in place.

As the hole is advanced, additional lengths of hollow stem flight and center stem are added as required, each length is usually 5ft. (3 to 6 ft. are possible)

The flight acts as a screw conveyer to bring soil to the surface for up to 100m

Method applicable in all soils. Difficulties occur in saturated sands under deep hydrostatic pressure where quick conditions at the bottom may destroy the boring.


Soil Borings

Continuous hollow flight augers, added in 5 ftincrements.

Hollow stem augers allow soil sampling without removal.

Act as temporary casing to stabilize borehole.

Center stem and plug are inserted down the hollow center during boring advance.

HSA range from about 6 to 12 inch O.D. with 3 to 8 inch I.D.

HSA generally limited to depths < 100 ft.

HSA should not be used in loose silts and sands below the GWT.

Truck-Mounted Rig with

Hollow-Stem Augers

SOIL TEST BORINGS (STB) Hollow Stem Augers (HSA)

Text & Photographs courtesy of FHWA NHI Course 132031 Subsurface Investigations

HSA outer and inner assemblywith stepwise

center bit

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Soil Borings

Continuous flight augers, added in 5-ft increments.

Limited to non-caving soils and depths < 30 ft.

Solid flight augers are removed prior to soil sampling, thus labor-intensive.

Auger diameters from 4 in to 8 in.

Front end has finger or fish-tail bit to loosen soil.

Spoil collects around top of borehole.

SOIL TEST BORINGS (STB) Solid Flight Augers

Solid Auger and Drill Bit




SOIL TEST BORINGS (STB) Solid Flight Augers

Soil Borings

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Soil Borings

Rotary wash techniques are best for borings extending below GWT.

Rotary wash can achieve great depths > 300+ ft.

Drilling bits: Drag bits for clays Roller bits for sand

In rotary wash method, borehole is stabilized using either temporary steel casing or drilling fluid.

Fluids include water, bentonite or polymer slurry, foam, or Revert that are re-circulated in tub or reservoir at surface.

SOIL TEST BORINGS (STB) Rotary Wash Borings

Truck Rig conducting rotary wash boring



SOIL TEST BORINGS (STB)Rotary Wash Borings

Schematic(Hvorslev 1948)


Soil Borings

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Soil Borings

Bucket auger drills are used for obtaining large disturbed or undisturbed samples.

Diameters range from 0.6 m (2 ft) to 1.2 m (4 ft).

Increment of 0.3 m to 0.6 m depths (1 to 2 feet).

Good for gravelly soils and cobbles.

Same rigs used for constructing Drilled Shafts.

Setup of rig for Bucket Auger Boring(ASTM D4700)

SOIL TEST BORINGS (STB) Bucket Auger Borings

Text and Figure courtesy of FHWA NHI Course 132031 Subsurface Investigations


Soil Sampling Disturbed Sampling (Most Common)

Bulk samples (from auger cuttings or TP excavations).

Bucket samples (borrow pits). Drive samples (e.g. split-spoon). Laboratory Tests: Grain size, Atterberg Limits,

Specific Gravity, Organic Content, Hydraulic Conductivity (coarse grained), Shear Strength (coarse grained).

Most of the disturbed soil samples are obtained through the SPT. Limited use can be made by data obtained through “cutting open” a clayey sample and testing it with pocket penetrometer and torque vane.

Undisturbed Sampling (ASTM D1587) Push Tubes (e.g. Shelby, Piston, Laval) Rotary & Push (e.g. Denison, Pitcher) Block Samples Laboratory Tests: Consolidation, Hydraulic

Conductivity (cohesive), Shear Strength (cohesive) Text & Photographs courtesy of FHWA NHI Course 132031 Subsurface Investigations

Split Spoon Sampler

Thin Wall Samplers

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after Fang et al. (1991) and EM 1110-1-1905.NOTE: 1 MPa = 10.44 tsf

Soil Density/Consistency Nqt

(MPa)t

(pcf)′(°)

SANDS

V. Loose 0-4 0-2 90-105 <30

Loose 5-10 2-5 95-110 30-35

Medium Dense 11-30 5-15 105-120 35-38

Dense 31-50 15-25 115-130 38-41

Very Dense >50 >25 125-140 41-44

COHESIVE SOILS

Very Soft 0-2 0-0.5 90-100

NA

Firm 2-8 0.5-1.5 90-110

Stiff 9-15 1.5-3 105-125

Very Stiff 15-30 3-6 115-135

Hard >30 >6 120-140

Soil Engineering Property Correlationsfrom Insitu Testing

Soil Sampling


Soil Engineering Properties DeterminationMaximum Allowable Shear Strengths (SCDOT, 2010)

Soil Sampling

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Soil Engineering Properties DeterminationMaximum Allowable Shear Strengths (SCDOT, 2010)

Soil Sampling


Coefficient of Variation (V) for Geotechnical Properties and Insitu Tests (after Duncan, 2000)

Measured or Interpreted Parameter

V

(%)

Unit Weight () 3 to 7

Effective Friction Angle (') 2 to 13

Undrained Shear Strength (Su) 13 to 40

Undrained Shear Ratio (Su/'vo) 5 to 15

SPT N Value 15 to 45

Electric CPT Tip Resistance (qt) 5 to 15

Also see Chapter 8 – Applying Judgement in Selecting Soil and Rock Properties for Design (FHWA IF-02-034).

Coefficient of Variation: A measure of dispersion of a probability distribution.

after Table 52. FHWA IF-02-034

Soil Sampling

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Soil Borings – Determination of Soil Stratigraphy

Figure 9-1. FHWA NHI Course 132031 Subsurface Investigations

Soil Sampling


Soil Sampling

Very common test worldwide

1902 - Colonel Gow of Raymond Pile Co.

Split-barrel sample driven in borehole.

Conducted on 2½ to 5 ft depth intervals.

ASTM D1586 guidelines

Drop Hammer (140 lbs falling 30 inches)

Three increments of 6 inches each; Sum last two increments = “SPT N value" (blows/ft)

Correlations available with all types of soil engineering properties.

Disturbed Soil Samples Collected

STANDARD PENETRATION TEST (SPT) (ASTM D1586-08a)

Text courtesy of FHWA NHI Course 132031 Subsurface Investigations

Marking of 6 inch Increments for SPT Test Photograph courtesy of physics.uwstout.edu

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Soil SamplingSPT - Standard Penetration Test

General Most economic and popular means to obtain subsurface

information in the USA

“Split Spoon Sampler” ASTM D-1586-84 (text p. 81, Fig. 2.15). Thick wall sampler O.D = 2 inch, I.D. = 1 3/8 inch (See ASTM D 1586-84, attached – p. 59 of the notes)

Using a 140lb. hammer falling 30” to drive a split-barrel sampler 18 inch into the soil.

Count the number of blows required to drive the sampler 6” (3 times)

The test result, N SPT = number of blows required for the sampler to penetrate the last 12” (from 6 to 18 inch penetration)



General6 6 6

Example Blows/6 20 33 17 1.5

Stop test & mark boring log by “refusal” if: 50 blows required for any 6 Obtain 100 blows from the beginning In 10 successive blows, there is no evidence of movement Usually measure distance and number, e.g. 40b/2 meaning

40 blows measured along 2 inches.

When the sampler penetrates under its own weight (and rods) mark WOR = weight of rods

Boring

4ob/2”

0

5

10

15

50

10

WOR

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14.528 Drilled Deep Foundations – Samuel Paikowsky 67 of 235Figures courtesy of J. David Rogers, Ph.D., P.E., University of Missouri-Rolla & FHWA NHI Course 132031


Typical Setup

Split Spoon Dimensions (after ASTM D1586)

Soil Sampling



Figure courtesy of FHWA NHI Course 132031 Subsurface Investigations

Soil Sampling

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TEST RESULTS (i.e. BORING LOG)


Shows the following:

Soil Profile (determined from sampling and boring information) with respect to depth and/or elevation.

Groundwater Table (GWT).

SPT N Values.

Laboratory Test Results (if available).

Boring Log courtesy of Dr. Edward Hajduk and WPC Engineering Inc.

ASTM D5434-09 Standard Guide for Field Logging of Subsurface Explorations of Soil and Rock

Soil Sampling


TEST RESULTS(i.e. BORING LOG)


Class Project Boring Log (pg1/3)

Soil Sampling

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Soil Sampling





Soil Sampling

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Factors Affecting the SPT

a. Overburden pressureb. Energy approaching the bottomc. Driving shoe conditiond. Hitting on a stonee. Quick conditions in the hole bottom by too rapid withdrawal of

auger or bit plug or from the SPT (liquefaction).f. Differential water level between GWL and the water inside the

hollow auger.g. “Method” of hammer fall Energy production from automatic

trip or rope on pulley

Note: Factors c to g should be dealt by adequate procedures and inspection.

“scientific factors”


STANDARD PENETRATION TEST (SPT)Factors Affecting SPT (after Kulhawy & Mayne, 1990 & Table 8.

FHWA IF-02-034 )

Cause EffectsInfluence

on N Value

Inadequate Cleaning of BoreholeSPT not made in insitu soil, soil

trapped, recovery reducedIncreases

Failure to Maintain Adequate Head in Borehole Bottom of borehole may become quick Decreases

Careless Measure of Drop Hammer Energy varies Increases

Hammer Weight Inaccurate Hammer Energy varies Inc. or Dec.

Hammer Strikes Drill Rod Collar Eccentrically Hammer Energy reduced Increases

Lack of Hammer Free (ungreased sleeves, stiff rope, more than 2 turns on cathead, incomplete release of drop, etc.)

Hammer Energy reduced Increases

Sampler Driven Above Bottom of Casing Sampler driven in disturbed soil Inc. Greatly

Careless Blow Count Recording Inaccurate Results Inc. or Dec.

Use of Non-Standard Sampler Correlations with Std. Sampler Invalid Inc. or Dec.

Coarse Gravel or Cobbles in soil Sampler becomes clogged or impeded Increases

Use of Bent Drill Rods Inhibited transfer of energy to sampler Increases

Soil Sampling

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38


CORRECTIONS TO SPT N VALUE

Nmeasured = Raw SPT Value from Field Test (ASTM D1586-08a)

N60 = Corrected N values corresponding to 60% Energy Efficiency(i.e. The Energy Ratio (ER) = 60% (ASTM D4633-10)

Note: 30% < ER < 100% with average ER = 60% in the U.S.

Factor Term Equipment Variable Correction

Energy Ratio CE = ER/60

Donut Hammer

Safety Hammer

Automatic Hammer

0.5 to 1.0

0.7 to 1.2

0.8 to 1.5

Borehole Diameter CB

65 – 155 mm

150 mm

200 mm

1.00

1.05

1.15

Sampling Method CS

Standard Sampler

Non-Standard Sampler

1.0

1.1 to 1.3

Rod Length CR

3 – 4 m

4 – 6 m

6 – 10 m

> 10 m

0.75

0.85

0.95

1.00

N60 = CECBCSCRNmeasured

For Guidance Only. Actual ER values should be measured per ASTM D4633

SPT CorrectionsFrom Table 9

FHWA IF-02-034

Soil Sampling



Adjusting the SPT results for Standard Readings

1. Energy

Ein = Ep = mgh

Ein = 63.5Kg 9.807m/sec2 0.762m = 474.5kN.m (Joul)=140lb.2.5ft = 350lb.ft

Er = efficiency = x 100% = 30% to 80%

(input)

mh

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1. Energy (cont’d.)

Bowles suggests to use 70%Very common in other references, the standard SPT efficiency is considered to be 60% and, hence, N60 is often used for correlations.

E1 x N1 = E2 N2 N2 = N1

e.g. hammer efficiency E1 = 55% N1 = 25

N70 = x 25 N70 = 20 (19.6)

or

N60 = x 25 N60 = 23 (22.9)


Data from Robertson, et al. (1983), Courtesy of FHWA NHI Course 132031 Subsurface Investigations

CORRECTIONS TO SPT N VALUEEXAMPLE OF DATA FROM SAME SITE

4

6

8

10

12

14

16

0 10 20 30 40 50

Measured N-values

Dep

th (

met

ers)

Donut

Safety

Sequence

ER = 34 (energy ratio)

45

40

41

41

39

47

56

55

60

56

63

63

63

64

69

4

6

8

10

12

14

16

0 10 20 30 40 50

Corrected N60

De

pth

(m

ete

rs)

Donut

Safety

Trend

Soil Sampling

1/31/2014

40


Soil Sampling SPT - Standard Penetration Test


2. Overburden PressureSee text pp. 85-86 and attached paper: “Overburden Correction Factors for SPT in Sand” by Liao & Whitman (ASCE, J. Of Geotechnical Engineering, Sept. 1985, class notes pp. 68-72).

CN - adjusting factor which is the ratio of SPT at a given effective vertical stress v to a standard stress level vref = 1 tsf = 1kg/cm2

Say 18 kN/m3 and no water, t = v 100 kN/m2

D = 5.5m 15ft.

CN = v in tsf or kg/cm2 (1 tsf = 0.976 kg/cm2)




2. Overburden Pressure (cont’d.)

Or in a general format:

CN = (Pa/'vo)n

Pa = Atmospheric Pressure (1 atm = 14.7 psi = 2116 psf = 1.06 tsf)'vo = Insitu Vertical Effective Stressn = 1 (clays) and 0.5 to 0.6 (sands)

For stresses of v < 1 tsf the relations proposed by Skempton (1986) can be used (text equations 2.12 & 2.13).

CN = v in tsf or kg/cm2

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3. Other Corrections are available including hammer type, rod length, sampler (with or without a liner), borehole diameter correction and others. On the whole, the accuracy and necessity of these corrections are questionable and their importance is secondary to the above two controlling factors and a standard procedure

4. The standard blow count to be used for correlations is:Ncorr = N60 x CN

N60 = Nx

X = the energy during test and CN to be used for granular materials

Note: Ncorr is also represented by (N1)60, N1 or N


CARE & PRESERVATION OF SOIL SAMPLES

Mark and Log samples upon retrieval (ID, type, number, depth, recovery, soil, moisture).

Place jar samples in wood or cardboard box.

Should be protected from extreme conditions (heat, freezing, drying).

Sealed to minimize moisture loss

Packed and protected against excessive vibrations and shock.

Text and Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations

Soil Sampling

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42



Correlations between SPT and Soil ParametersThe SPT has been used in correlations for unit weight, relative density, angle of internal friction and undrained shear strength. All are empirical correlations with limited accuracy

1. SPT in Clay SPT is not recommended for clays Based on Mayne and Kemper (1988)

0.193.

′

Table 2.6 (p. 84)

NOTE: N in clay does not require corrections to a standard effective stress (i.e. don’t use CN)

Su

qu



Correlations between SPT and Soil Parameters

2. SPT in Sand Table 2.8 (p. 87) of the text, simplified relations

Equations 2.19 to 2.25 for a correlation between relative density and effective overburden stress

Equations 2.26, 2.27 and 2.28 for a correlation between standard penetration number and friction angle

Table 2.8 Relation between the Corrected (N1)60 Values andthe Relative Density in Sands

Standardpenetrationnumber, (N1)60

Approximaterelative density,Dr′,(%)

0 – 5 0 – 55 – 10 5 – 3010 – 30 30 – 6030 – 50 60 – 95

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Some Additional Correlations

Relative Density

Bowles (1996) DR = / 32 0.288 ′ ′ in kPa

for O.C.R. sand DR = / 32 0.288 ′ Cocr)

COCR = (1 + 2Ko OCR)/(1 + 2Ko NC)

Giuliani & Giuliani Nicoll (1982)

DR = / (4.188 + 0.639 0.606)

v in t/m2 = 10 kPa and N is uncorrected




Some Additional Correlations (cont’d.)

Friction AngleTeng (1962) = (25o to 30o) + 0.15 DR

DR in %

Paikowsky (1982) = 30.8 + 0.1 DR for Israeli dune sands

Empirical values for , Dr, and unit weight of granular soils based on the SPT at about 6m depth and normally consolidated [approximately, = 28 + 15Dr (2)] (Bowles, 1996)

NOTE: Use Ncorr SPT values in the table

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NOTE: Use Ncorr SPT values in the table

Description Very loose Loose Medium Dense Very dense

Relative density Dr 0 0.15 0.35 0.65 0.85

SPT N70: finemediumcoarse

1-22-33-6

3-64-75-9

7-158-2010-25

16-3021-4026-45

?> 40> 45

: finemediumcoarse

26-2827-2828-30

28-3030-3230-34

30-3432-3633-40

33-3836-4240-50

< 50

wet, kN/m3 11-16* 14-18 17-20 17-22 20-23

*Excavated soil or material dumped from a truck has a unit weight of 11 to 14 kN/m3 and must be quite dense to weigh much over 21 kN/m3. No existing soil has a Dr = 0.00 nor a value of 1.00. Common ranges are from 0.63 to 0.7.


Soil Sampling Paikowsky et al. NCHRP 12-66

0 10 20 30 40 50 60N70', (blow/ ft)

60

70

80

90

100

110

120

130

140

150

160

we

t, (p

cf)

0 10 20 30 40 50 60

60

70

80

90

100

110

120

130

140

150

160

(pcf)=

0.88N'+99 (pcf)=

1.03N'+109

(pcf)=0.72N'+89

Unit Weight vs. SPT for Sand

Loose

Medium Dense

Figure 3.1 -NRelationship for Sand (General Condition) Based on Bowles (1996).

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Correlations of to NHatanaka, M. & Uchida, A. (1996) Empirical correlation between penetration resistance and internal friction angle of sandy soils

20 20 (Eq. 2.28)

Peck, Hansen and Thornblum (1974) (Wolff, 1989 version) = 27.1 + 0.3 N60 – 0.00054(N60)2 (Eq. 2.26)

(Kulhawy and Mayne 1990 version) = 54 – 27.6034 .

Japan Road Association (JRA) (1990 & 1996) "Specifications for highway bridges, Part IV“

15 15 N > 5 and 45



N1 = 2 6 8 10 15 20 25 30 35 40 45 50fHNU = 26.3 31.0 32.7 34.1 37.3 40.0 42.4 44.5 46.5 48.3 50.0 51.6fPHT = 27.7 28.9 29.5 30.0 31.5 32.9 34.3 35.6 36.9 38.2 39.5 40.8fK&M = 27.2 28.6 29.3 30.0 31.6 33.1 34.5 35.9 37.1 38.2 39.3 40.3fJRA = -- 36.6 37.1 37.6 38.7 39.5 40.2 40.8 41.4 41.9 42.4 --

0 10 20 30 40 50 60 70Corrected SPT count, (N1)60

20

25

30

35

40

45

50

Soil

fri

ctio

n an

gle,

f (

deg)

PHT 1974 (Wolff, 1989)

PHT (Kulhawy & Mayne, 1990)

Hatanaka & Uchida (1996)

SHB, Japan (JRA, 1996)

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Soil Sampling Paikowsky et al. NCHRP Report 651

Table 30 Summary of equation correlating internal friction angle (f) to corrected (N1)60 SPT-N value

Reference Correlation Equation Equation No.Peck, Hanson and Thornburn

as mentioned in Kulhawy and Mayne (1990)(PHT (Kulhawy & Mayne, 1990) )

(100)

Hatanaka and Uchida (1996) (101)

Peck, Hanson and Thornburn (1974) as mentioned by Wolff (1989)

(PHT 1974 (Wolff, 1989))(102)

Mayne et al. (2001) based on data from Hatanaka and Uchida (1996)

(103)

Specifications for Highway Bridges (SHB)

Japan, JRA (1996)(104)

1 6054 27.6034 exp 0.014f N

1 60

1 60

20 20

for 3.5 30

f N

N

2

1 160 6027.1 0.3 0.00054f N N

1 6015.4 20f N

1 60

1 60

15 15

for 5 and 45

f

f

N

N

pa is the atmospheric pressure and v is effective overburden pressure in the same units. For English units, pa = 1 and v is expressed in tsf at the depth N60 is observed.(N1)60 is the corrected SPT-N value corrected using the correction given by Liao and Whitman (1986):

(105) 1 6060 '

a

v

pN N


Soil Sampling

0 10 20 30 40 50 60 70Corrected SPT count, (N1)60

25

30

35

40

45

Soi

l fri

ctio

n an

gle,

f (

deg)

PHT 1974 (Wolff, 1989)

PHT (Kulhawy & Mayne, 1990)

Hatanaka & Uchida (1996)

Hatanaka & Uchida(Mayne et al, 2001)

SHB, Japan (JRA, 1996)

Figure 56. Comparison of various correlations between granular soil friction angle and corrected SPT blow counts (using the overburden

correction proposed by Liao and Whitman (1986)).

Paikowsky et al. NCHRP Report 651

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47

Soil Sampling

Gurbuz Thesis

0 5 10 15 20 25 30 35Nuncorrected (blow/ft)

70

80

90

100

110

120

130

140

150

160

, p

cf

0 5 10 15 20 25 30 35

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

, k

N/m

3

Legend Key Soil Type Correlations Limit Reference Comment

Lean Clay 10602.1 N 140 pcf

Lean Clay 99)(33.9 NLN 140 pcf

Fat Clay 9535.1 N 140 pcf

Fat Clay 87)(65.11 NLN 140 pcf

Terzaghi and Peck (1967), Bardet (1997)

Sandy or Silty Clay

10056.1 N 147 pcf

Silty Clay with stones or rock

fragment 1152.1 N 151 pcf

Well-graded Gravel, Sand,

Silt & Clay mixture

12503.1 N 156 pcf

Valid if the soil mixture is classified as clay, otherwise use the correlation established for sand.

Organic Clay 8146.1 N 125 pcf

Organic Silt 8746.1 N 131 pcf

Terzaghi and Peck (1967),

NAVFAC Design Manual

(1986)

Figure 3.2 -NRelationship for Clay


Elastic Method1. AASHTO – LRFD Bridge Design Specifications (1998) (cont’d.)Table 1. Elastic Constants of Various Soils Modified after U.S. Department of

the Navy (1982) and Bowels (1988) (AASHTO Table 10.6.2.2.3b-1)

Soil Type

Typical Range of Values Poisson’s

Ratio, (dim)

Estimating Es from N

Young's Modulus (tsf)

Soil Type Es (tsf)

clay: soft sensitive 25-150 0.4-0.5 Silts, sandy silts, slightly cohesive mixtures 4N1

Medium stiff to stiff 150-500 (undrained) Clean fine to medium sands & slightly silty sands 7N1

Very stiff 500-1000 Coarse sands and sand with little gravel 10N1

Sandy gravel and gravels 12N1

Loss Silt 150-600 0.1-0.3 Sandy gravel and gravels 12N1

20-200 0.3-0.35Fine Sand: Estimating Es from Su

Loose 80-120 Soft sensitive clay 400Su-1,000Su

Medium dense 120-200 0.25 Medium stiff to stiff clay 1,500Su-2,400Su

Dense 200-300 Very stiff clay 3,000Su-4,000Su

Sand:Loose 100-300 0.20-0.35

Medium dense 300-500Dense 500-800 0.30-0.40

Gravel: Estimating Es from qc

Loose 300-800 0.2-0.35Medium dense 800-1,000 Sandy Soil 4qc

Dense 1,000-2,000 0.3-0.4Notes: N = Standard Penetration Test (SPT) resistance N1 = SPT corrected for depth

Su = undrained shear strength (TSF) qc = cone penetration resistance (TSF)

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48

Young’s Modulus of Sands (Es) vs. Blow Count

0 10 20 30 40 50 60

Measured or Corrected N (blows/ft or 305 mm)

0

400

800

1200

Yo

un

g's

Mo

du

lus

, E/P

a

LOOSE MEDIUM DENSE V.DENSE

Driven piles

Typical

Legend Key Relations Soil Type Reference Comment

)15(5.0/ NpE as NC Sand General Sources,

see Bowles (1996) N = N55

NpE as 70/ NC Sand Denver (1982) N = N55

)ln(150/ NpE as NC Sand USSR

(See Bowles, 1996) N should be estimated as N55, and N may not be standard blow count

)ln(220/ NpE as NC Sand USSR

(See Bowles, 1996) N = N55. N may not be the standard blow count

605/ NpE a Sands with

fines Kulhawy & Mayne

(1990)

6010/ NpE a Clean NC

Sand Kulhawy & Mayne

(1990)

6015/ NpE a Clean OC

Sand Kulhawy & Mayne

(1990)

82.022/ NpE aD

Piedmont Sandy Silts

Using Mayne & Frost (1989)

Recommended by O’Neill & Reese (1999) for use with drilled shaft elastic analysis in cohesionless IGM. ED is the modulus measured in the dilatometer test (DMT).

82.002.20/ NpE a

Piedmont Sandy Silts

Mayne & Frost (1989)

ED is replaced by Es through the relation: ED=Es/(1-2), & =0.3.

66.008.9/ NpE aPMT Sand Ohya, et al (1982)

EPMT is the modulus measured in the pressuremeter test (PMT), and is often presumed to be roughly equivalent to Young’s modulus E.

)ln(200/ NpE as Sand Current study Driven Piles

For N>60 use N=60. Recommended for driven piles

)ln(112/ 007.0 NepE Nas Sand

Current study Drilled Shafts

For N>60 use N=60. Curve best fit of all information for drilled shaft.

Recommended for Drilled Shafts

Recommended for Driven Piles

For driven pilesEs / pa = 200ln(N), N 60

For drilled shaftsEs / pa = 112e0.07ln(N), N 60

where:pa = atmospheric pressure = 0.1

MPaEs = Young’s modulus of soilsN = corrected blow count in SPT

tests for 60% energy and vertical effective stresses



Young’s Modulus of Clay (Es) vs. Undrained Shear Strength

Legend Key Relations Soil Type Reference Comment

us sE )500~100( Ip > 30 or organic

General resource, see Bowles (1996)

Lines represent upper and lower range.

us sE )1500~500( Ip < 30 or stiff General resource, see Bowles (1996)

Lines represent upper and lower range.

us KsE

32 0071.073.154.1424200 ppp IIIK General clay

General resource, see Bowles (1996)

Use 20%Ip100% and round K to nearest multiple of 10. Lines represent upper and lower range.

Clay Poulos & Davis

(1990) For driven piles. Drained condition.

Clay Poulos & Davis

(1990) For bored piles. Drained condition.

40000~15000uE Soft clay Kulhawy & Mayne

(1990)

Lines represent upper and lower range. Undrained condition.

80000~40000uE Medium clay Kulhawy & Mayne

(1990)


200000~80000uE Stiff clay Kulhawy & Mayne

(1990)


us SE 200 Clay Current study Reasonable approximation for all piles in clay

0 50 100 150 200 250Su, kPa

1.0x102

1.0x103

1.0x104

1.0x105

1.0x106

Es,

kP

a

0 50 100 150 200 250

1x102

1x103

1x104

1x105

1x106


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Young’s Modulus - SUMMARY

For driven pilesEs / pa = 200ln(N), N 60 (6.2)

For drilled shaftsEs / pa = 112e0.07ln(N), N 60 (6.3)

where:pa = atmospheric pressure = 0.1 MPaEs = Young’s modulus of soilsN = corrected blow count in SPT tests for 60% energy and vertical effective

stressesBoth equations are limited by the value of Es for N=60, i.e. for N>60 use N=60. The

equation 6.3 has the combination of exponential and logarithmic formats to overcome the overestimation of E when N<10 and the underestimation of E when N>30.

In ClayEs = 200Su (6.4)

where:Es = Young’s modulus of soilsSu = undrained shear strength

In Sand




EXAMPLE

Depth (ft.)0 _____________ Find the soil parameters of

//\\//\\\\////\\\\\//// the marked layer based on Fill the SPT resultst = 120pcf

10.5 _____________Silty Clayt = 118pcf _______ GW Level =15ft.

20.5 _____________

Fine to MediumSand Depth=25.0 ft. N=25

t = 120pcf


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EXAMPLE (cont’d.) Vertical effective stress at the depth of measurement:

v = 10.5.120 + (15.0-10.5).118 + (20.5-15.0).(118.0-62.4) + (25.0-20.5).(120.0-62.4) = 2,356 psf = 1.178 tsf = 118 kPa. = 11.8t/m2

correction factor for the overburden:Er = 95% (measured efficiency)corrected blow count to the “standard” 60 or 70% efficiency:

N70 = (95/70) x 25 = 33.9 N60 = (95/60) x 25 = 39.6

CN = .

= 0.921

(Ncorr)60 = 39.6 x 0.921 = 36.4 = 36 blows

(Ncorr)70 = 33.9 x 0.921 = 31.3 = 31 blows




EXAMPLE (cont’d.)When considering all other additional factors the corrected blow count can go up or down by one blow, in this particular case we use the final result of N = 31 blows for the correlations.

Table correlation considering sand typeUsing Bowles’ table (notes p. 90):Dense Sand, DR 70%, = 38

Establishing relative density Using the equation by Bowles:

3132 0.288 118

0.69 69%

Using Giuliani & Giuliani Nicoll:27/ 4.188 0.639 11.8 . 74%


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EXAMPLE (cont’d.)

Correlations = f(DR)Using Teng: = 35 to 40Using the correlation for Israeli dune sand = 38

Correlations = f(N60)Hatanaka and Uchida = 45Using PH&T = 35.9 (Wolff), = 36.1 (Kulhawy & Mayne)

Conclusions:1. Using interpolated values in Bowles’ table provide a reasonable

solution and allow grain size consideration.2. Check several correlations to view range of results.3. Experience showed PHT (Kulhawy & Mayne) to provide good and safe

correlation of =f(N1).



EXAMPLE INTERPRETATION –

SPT Given Data

Provided:- Soil Stratigraphy- USCS Classification- Groundwater Table(@ Time of Testing)

- SPT N Values(No Energy Measurements)

- Drilling Method (HSA)- Date Started/Ended

Soil Sampling

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52

14.528 Drilled Deep Foundations – Samuel Paikowsky 103 of 235t from Table Soil Engineering Properties Correlations (pg. 69 of notes)

EXAMPLE INTERPRETATION – SPTDetermination of Nave, t, and 'vo

Soil Sampling

0 10 20 30B-7 N (bpf)

25

20

15

10

5

0

De

pth

(ft

)

SAND - Silty SANDNave = 17

use t = 115 pcf

Sandy SILTNave = 4

use t = 110 pcf

Clayey SILT (MH)/MARLNave = 4

use t = 115 pcf

0 1000 2000'vo (psf)

25

20

15

10

5

0

De

pth

(ft

)

0

460

9201030

14801565


Calculate Nave for sand layer from 0 to 8 ft.

Simple Way:Using Soil Engineering Properties Correlations (pg. 69 of notes)

Nave = 17, therefore ' ≈ 36°

Formula Way:Use Mayne et al. (2001)

' = [15.4(N1)60]0.5 + 20° and (N1)60 = N60(Pa/'vo)0.5

Use Nave = 17, 'vo,ave = 460 psf, and Pa = 2115 psfTherefore, (N1)60 = 17(2115/460)0.5 = 36

Using equation ' = [15.4(N1)60]0.5 + 20°, ' = 44°

USE ' = 36°

EXAMPLE INTERPRETATION – SPTDetermination of Effective Friction Angle (')

0 10 20 30B-7 N (bpf)

25

20

15

10

5

0

De

pth

(ft

)


use t = 115 pcf

Sandy SILTNave = 4

use t = 110 pcf


use t = 115 pcf

Soil Sampling

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53

Soil SamplingASTM Standard

D1586-08a


D1586-08a

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D1586-08a


D1586-08a

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D1586-08a


D1586-08a

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D1586-08a


D1586-08a

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Soil Sampling ASTM StandardD1586-08a

Soil SamplingASCE Journal of

Geotechnical EngineeringVol. 112, No. 3

March 1986

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58



March 1986



March 1986

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March 1986



March 1986

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60


Soil Sampling

Split-Spoon Disturbed Sampling

Thin walled Tubes –Undisturbed Sampling (ASTM D1587)


Split Spoon Sampler

Thin Wall Samplers


Soil SamplingShelby Tubes

Using a thin walled tubes (O.D. = 2in.) which is pushed into the soil under the bottom of the borehole in order to retrieve a sample mainly for laboratory tests.The sampling can be performed by a direct connection to the drill rods or using a piston sampler.

(i) Piston closes the end of the sampler while it is lowered to the bottom of the borehole.

(ii) The sampler is pushed hydraulically(iii) The pressure is released through a hole in the piston rod(iv) The assembly is pulled upwards.

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Soil SamplingShelby Tubes

Figure 2.18 (continued), text pp.90 & 93, respectively

Soil SamplingASTM D 1587-08

Standard Practice for Thin-Walled Tube

Sampling of Soils for Geotechnical Purposes

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INSITU TESTING METHODS

METHOD Abbrv. ASTM SAMPLING MAX. DEPTH (ft)

Dynamic Cone

PenetrometerDCP D6951-03

Yes(via HAB)

6 – 8 Typ.20 (w/difficulty)

Standard Penetration Test

SPT D1586-08a Yes > 300 ft(dependent on boring method)

Cone Penetration Test CPTD3441-05

D5778-07No > 300 ft

(typically 100 – 150 ft max)

Flat Plate Dilatometer DMT D6635-01 No > 300 ft(typically 100 – 150 ft max)

Pressuremeter PMT D4719-07Yes

(via boring)> 300 ft

(dependent on boring)

Vane Shear Test VST D2573-08Yes

(via Boring)> 300 ft

(dependent on boring)

Green – Near Surface : Red – Near and Deep

Soil Sampling

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Figure courtesy of FHWA NHI Course 132031Subsurface Investigations

Soil Sampling


Soil Sampling

Vane Shear Test (VST) (ASTM D2573-08)

General

Vane shear test (ASTM D 2573-01) is a useful method to estimate the undrained shear strength of cohesive - soft soils, especially where much of the strength may be lost by disturbance during sampling.

not good in stiff clays or soft soils containing gravel, shells etc.

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Soil Sampling

Performed at bottom of boring or by direct push placement of device

Four-sided blade pushed into clays and silts to measure following:

suv (peak) = Peak UndrainedStrength

suv (remolded) = Remolded Strength (after 10 revolutions)

Sensitivity, St = suv(peak)/suv

(remolded)

VANE SHEAR TEST (VST) (ASTM D2573-08)

Scandinavian Vanes

Pictures and text courtesy of FHWA NHI Course 132031 Subsurface Investigations


Soil Sampling

Procedure

Placing a four-bladed vane in the undisturbed soil (under the bottom of the borehole) and rotating it from the surface to determine the (peak) torsional force (through torque) required to cause a cylindrical surface to be sheared by the vane. This force is then converted to a unit shearing resistance of the cylindrical surface. The test continues to measure the strength of the remolded material by measuring the resistance to the rotation after the vane is rotated rapidly through a minimum of 10 revolutions.


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Soil Sampling


Casing(OD) D(in) Blade thick Rod(in)

AX (17/8) 1.5 1/16 1/2BX (23/8) 2.0 1/16 1/2NX (215/16) 2.5 1/8 1/2

Vane Dimensions1.5 D 4 inch1 D H 2.5 D





Soil Sampling

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67


Dutch Vane Equipment, Holland VST in Upstate NY

VANE SHEAR TEST (VST) (ASTM D2573-08)Vane Shear Devices

Pictures courtesy of FHWA NHI Course 132031 Subsurface Investigations

Soil Sampling


Soil Sampling

Analysis

Obtaining the consolidated (in-situ) undrained shear strength

Suv: u=undrained, v=vane

T=SuvAR

T - TorqueSuv - shear strengthA- area of shear applicationR - arm of force

peak

Torque

residual

20 Movement(rotation in radians)

H = 2D

T

D/2


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Soil Sampling

Analysis (cont’d.)

for the circumferential shearing area:A = DH R = D/2 AR = (D2H/2)

for the top and bottom shearing area:

A = D2/4 R = D 1/3(2) = (2/3)D

AR = (D3 /4)(2/3)⅔D x ½

⅔D x ½



Soil Sampling


Combining all shearing areas, leads to:

T = SuvAR = Suv [(D2H/2) + D3 /4 (2/3)]

For the standard case in which H = 2D and square end shear, the above equation becomes:

Suv = 6T/(7D3) = 0.2728T/D3

The general assumption is that vane test results are too high and require a correction. The reason can be the influence of the rate of shear, various frictional losses such that the measured torque is higher than the one actually performing the work and other assumptions in the above relations (e.g. stress distribution at the blade).

Suvcorrected = Suv


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Soil Sampling


see equations and figure below based on Bjerrum (1972)(equation 2.35, p. 97)

Bjerrum (1972):1.7 0.54 %

Morris & Williams (1994):1.18 . 0.57 (for PI>5)

7.01 . 0.57 (where LL is in %)

Aas et al. (1986):

see figureVariation of with cu(VST)/0



Soil Sampling

Estimation of OCR based on VST

Based on Mayne and Mitchell (1988) [see text p. 97]

pc = 7.04 (Sufield)0.83 OCR =

pc = maximum past pressure [kPa]

Sufield = uncorrected field vane value [kPa] (=Cufield)

(eq. 2.37)

= 22 (PI)-0.48


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Soil Sampling

Estimation of OCR based on VST (cont’d.)

Variation of with plasticity index

(after Mayne and Mitchell, 1988)

See other correlations for (equations 2.39, 2.40)


Soil Sampling



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0

5

10

15

20

25

30

0 10 20 30 40 50 60 70 80

Vane Strength, suv (kPa)D

epth

(m

eter

s)

Peak

Remolded

0

5

10

15

20

25

30

0 1 2 3 4 5

Sensitivity, St

Dep

th (

met

ers)

VANE SHEAR TEST (VST) (ASTM D2573-08)Results - San Francisco Bay Mud, MUNI Metro Station

VST Results courtesy of FHWA NHI Course 132031 Subsurface Investigations

Soil Sampling



VST Results courtesy of FHWA NHI Course 132031 Subsurface Investigations

Soil Sampling

Fig. 2.9 (a) Undisturbed and (b) thoroughly remolded sample of Leda clay from Ottawa, Ontario. (Photograph courtesy of the Division of Building Research National Research Council of Canada. Hand by D.C. MacMilan)

Table 11-7 Typical Values of Sensitivity

(figure and table from: Holtz, RD, and Kovacs, WD (1981) An Introduction to Geotechnical Engineering, Prentice-Hall, New Jersey)

ConditionRange of St

U.S. SwedenLow sensitive 2 – 4 < 10Med. sensitive 4 – 8 10 – 30Highly sensitive 8 – 16 > 30Quick 16 > 50Extra quick - > 100Greased lightening -

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• Electronic Steel Probes with 60° Apex Tip• Hydraulic Push at 20 mm/s• No Boring, No Samples, No Cuttings, No

Spoil• Continuous readings of stress, friction,

pressure• With Pore Pressure Measurements (CPTu)• With Shear Wave Measurements (SCPT)

CONE PENETRATION TEST (CPT) (ASTM D5778-07)

Text and Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations

Soil Sampling


CONE PENETRATION TEST (CPT) RIGS

Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations & WPC Engineering Inc.

Soil Sampling

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CONE PENETRATIONTESTING (CPT)

Factors Affecting CPT ResultsFigure 9-2. FHWA NHI Course 132031 Subsurface Investigations

qc

Vs

U2

fs

Soil Sampling


Soil SamplingCPT – Cone Penetration Test

General (ASTM D-3441-01) Deep, Quasi-Static, Cone and Friction-Cone

Penetration Tests of Soils.

The CPT is an in-situ, sounding method in which a cone (usually 60o

and 10 cm2 base area) is pushed into the ground at a rate of approximately 10 to 20 mm/sec and the resistance to penetration is measured.

Useful in soft clays and fine to medium coarse sands. It encountered difficulties in stiff/hard, cemented or highly over-consolidated soils.

Advantage - obtaining considerable information in a short time.

Disadvantage - non-recoverability of samples and the above difficulties.

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Figure 2.24 Electric Friction-cone penetrometer (after ASTM, 2001)


Soil SamplingCONE PENETRATION TEST (CPT) (ASTM D5778-07)

Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations

Shear Wave Velocity (Vs)

qc

Vs

u2

fs

Penetration Porewater Pressure (U2)

Sleeve Friction (fs)

Cone Tip Resistance (qc)

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Corrections to CPT Measurements (with U2)

Need to correct tip resistance (qc) for pore

pressure @ U2 location.

qc → qt

U2 = Ub

Pore PressureMeasurement behind Tip

Porous Element for U2

Materials: Sintered Metals, Ceramics, Plastics (disposable)Saturation of Porous Elements: Water, Glycerine, SiliconeProcedures: Vacuum for 24-hours, Pre-Saturated Elements, Prophylactic to maintain fluids

Courtesy of FHWA IF-02-034

Soil Sampling



Obtained Data cone-tip resistance qc

sleeve friction resistance fs

piezocone allows pore pressure readings, usually at the tip (u1) also possible at the base (u2) and above friction sleeve (u3).

fR = FR = Friction ratio = fs /qc x 100%

u1

u3

u2

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Soil Sampling CPT – Cone Penetration Test


Soil Sampling

0 100 200

qt [tsf]

0

4

8

12

16

20

24

28

32

36

40

44

48

52

56

60

64

68Dep

th [ft]

6.89

0 1 2

fs [tsf ]

0 2 4 6

u2 [tsf]

Uo [tsf]

0 2 4 6

Rf [%]

U2

Sleeve area [cm2]: 150

Tip area [cm2]: 10

Cone No: 3318

Te st no:

B-06Client:

Pro ject: Project in Savannah, GA

SAV2-02-000

Position:X: 1019956.90 m, Y: 759139.79 m

Ground level:10.43

Date:2/11/2002

Scale:

Page: 1

Fig :

File : sav2-02-010sc6.cpd

Very stiff fine grained (9)

C layey silt to silty clay (4)

C lays, clay to silty clay (3)


Silty sand to sandy silt (5)

Silty sand to sandy silt (5)C lays, clay to silty clay (3)



C layey silt to silty clay (4)C lays, clay to silty clay (3)


C lean sands to silty sands (6)




CONE PENETRATION TESTING (CPT) RESULTS

qc fsuo, u2 FRSoil Profile

CPT Results courtesy of Dr. Edward Hajduk and WPC Engineering Inc.

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Data Interpretation

Use of data can be applied directly in design using the similarity between the cone and a pile or with correlation to soil parameters

Soil Identification

A major drawback of the cone is the inability of obtaining actual soil sample. As such correlation based on the relationship between the friction ratio and soil type has been developed. Soil identification becomes easier with the piezocone which uses pore water pressure besides the friction ratio.



Soil classification chart for standard electric cone. Use with caution and/or together with recovered tube samples [After Robertson and Campanella(1983)], see Figure 2.31, p. 106.

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CONE PENETRATION TEST (CPT)DETERMINATION OF SOIL STRATIGRAPHY

CPT Soil Behavior Classification (Based on qt, FR or Bq)Figure 9-3. FHWA NHI Course 132031 Subsurface Investigations

Soil Sampling


CONE PENETRATION TEST (CPT)DETERMINATION OF SOIL STRATIGRAPHY

Soil Sampling

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qt (tsf) fs (tsf) Uo, U2 (tsf) FRSoil Profile

EXAMPLE INTERPRETATION – CPT Given Data

Dep

th (

ft)

Soil Sampling


qt (tsf) fs (tsf) Uo, U2 (tsf) FRSoil Profile

EXAMPLE INTERPRETATION – CPT Soil Layers

7ft

Dep

th (

ft)

17ft

GWT @ 9ft

SAND

SANDY SILT

SILTY CLAY(MARL)

Soil Sampling

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Cohesive Soils

Cone bearing resistance qc correlated to undrained shear strength Su = Cu. Using ultimate bearing strength as for foundation - pile tip in clay.

qc = qp + vo

qc = cone-tip resistanceqp = point resistancevo = total vertical pressure in the soil at tip elevation

qp = CuNc or Su Nk

in which Nc = Nk = Bearing Capacity Factor or Cone Factor in this case.qc = SuNk + vo

qc = CuNc + vo Cu = (eq. 2.51, p. 105)



Cohesive Soils (cont’d.)

Analogous to Poulus et al. (2003)Nk= 17.2 (electronic cone), Nk= 18.9 (mechanical cone)

Nk = Nc = 10 20 use Nc = 14.5 + 30%

(Nk is based on Pent. Testing. Proc. Of 2nd European Symp. On Penet. Testing /ESPOT II. Amsterdam. 1982).

Using Mayne and Kemper (1988) (see eq. 2.55, p.107)

OCR = 0.37.

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Granular Soils(text pp. 102-105)

DR = f (qc, v, A, B)

Use equation 2.44 with A = -98, B = 66

Use Figure below for DR = f (qc, v)

See alternatively Figure 2.29 for v, qc and DR

correlations based on Baldi et al., 1982, and Robertson & Campanella, 1983



Granular Soils (cont’d.)

Internal Friction Angle from CPT Kalhawy and Mayne (1990) based

on Robertson and Campanella(1985)

0

1 log38.01.0tan

cq

(eq. 2.47, see figure)

Variation of qc with ′0 and ′ in normally consolidated quartz sand (after Robertson and Campanella, 1983).

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EXAMPLE INTERPRETATION – CPTDetermination of qt,ave, t, and 'vo

Soil Sampling

0 100 200 300C-7 qt (tsf)

25

20

15

10

5

0

De

pth

(ft

)

SAND - Silty SANDqt,ave 125 tsf

use t = 115 pcf

Sandy SILTqt,ave 22 tsf

use t = 110 pcf

Silty CLAY - CLAYqt,ave 26 tsf

use t = 115 pcf

t from Table Soil Engineering Properties Correlations (pg. 69 of notes)

0 1000 2000'vo (psf)

25

20

15

10

5

0

De

pth

(ft

)

0

460

9201030

14801565


EXAMPLE INTERPRETATION – CPTDetermination of Effective Friction Angle (')

Calculate qt,ave for sand layer from 0 to 7 ft

Simple Way:Using Table Soil Engineering Properties Correlations (pg. 69 of notes)

qt,ave ≈ 125 tsf ≈ 12 MPatherefore ' ≈ 37°

Formula Way:Using Robertson and Campanella (1983) formula.

' = arctan[0.1+0.38log(qt/ 'vo)]

Use qt,ave ≈ 12 MPa (250000 psf) & 'vo,ave = 405 psf for layer.Using equation, ' = 49°

USE ' ≈ 37°

0 100 200 300C-7 qt (tsf)

25

20

15

10

5

0

De

pth

(ft

)


use t = 115 pcf


use t = 110 pcf


use t = 115 pcf

Soil Sampling

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EXAMPLE INTERPRETATION – CPTDetermination of Undrained Shear Strength (Su)

Calculate qt,ave for Sandy Silt from 7 to 17 ftCalculate qt,ave for Silty Clay from 17 to 24 ft

Formula Way:use Aas et al. (1986)

Su = (qt-vo)/Nkt

Nkt = 15 for CHS (Lecture Slides)

Sandy SILT LayerUse qt,ave ≈ 22 tsf & vo,ave = 1355 psfSu = 2850 psf

Silty CLAY LayerUse qt,ave ≈ 26 tsf & vo,ave = 2310 psfSu = 3300 psf

0 100 200 300C-7 qt (tsf)

25

20

15

10

5

0

De

pth

(ft

)


use t = 115 pcf


use t = 110 pcf


use t = 115 pcf

Soil Sampling



Correlation between SPT to qc This relation is Important as many correlations exist between N SPT and

different soil parameters and they can be utilized with the transformation from qc to N

Figure 2.30 General range of variation of qc/N60 for various types of soil (after Robertson

and Campanella, 1983)

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Soil Sampling

CPT – Cone Penetration Test

Correlation between SPT to qc (cont’d.)

Eq. 2.50

D50 (mm); qc same units as pa

26.050

60

6429.7 DN

pq

a

c


EXAMPLE INTERPRETATION – SPT & CPTComparison of Soil Engineering Properties

SPT CPT

Two Tests ~ 15 ft Apart

Methodt

(pcf)

'

()

SPT - Table Soil Engineering Properties Correlations (pg. 69 of

notes)

115 36

SPT - Formula NA 44

CPT - Table Soil Engineering Properties Correlations (pg. 69 of

notes)

115 37

CPT - Formula NA 49

Sand Layer Properties

0 100 200 300C-7 qt (tsf)

25

20

15

10

5

0

De

pth

(ft

)


use t = 115 pcf


use t = 110 pcf


use t = 115 pcf

0 10 20 30B-7 N (bpf)

25

20

15

10

5

0

De

pth

(ft

)


use t = 115 pcf

Sandy SILTNave = 4

use t = 110 pcf


use t = 115 pcf

Soil Sampling

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ROCK EXPLORATION

Geophysical Methods

Geologic Mapping (need qualified geologists)

Drilling and Coring

Exploration Test Pits UML Health and Social Sciences

BuildingLowell, MA

June 14, 2011(picture courtesy of Dr. Edward Hajduk)

Soil Sampling


ROCK EXPLORATIONDrilling and Coring

Rock Coring (see text section 2.24)

● Rock cores are necessary to establish the soundness of the rock. ● Using a coring bit at the bottom of the core barrel. Water is used for

washing the rock dust out and cooling the drilling.

● STB Refusal

– Auger refusal

– SPT refusal (> 50 blows per 1 inch penetration)

• Coring (ASTM D2113)

• Noncore Drilling

• Percussive Methods

ASTM D2113-08 Standard Practice for Rock Core Drilling and Sampling of Rock for Site Investigation

Soil Sampling

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ROCK EXPLORATIONDrilling – Rotary Wash

Tricone, Roller,Plug Bits

Roller BitsDrill Rig


Soil Sampling


ROCK EXPLORATIONCoring

● Diamond Bits. Best and hardest, producing high quality core. Fastest cutting rates. Expensive.

● Synthetic Bits. Less expensive. Generally good quality cores.

● Tungsten Carbide Bits. Least expensive. Slower coring rates.

Photograph courtesy of www.ackerdrill.com

Carbide Type Bits

Diamond, Carbide Tungsten, SawtoothDiamond

Soil Sampling

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Most rugged, least expensive.

Consists of head section, core recovery tube, reamer shell, & cutting bit.

Often used as starter when beginning core operations

ROCK EXPLORATIONCoring – Single Tube Core

Text & Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations

Soil Sampling


Soil SamplingRock Coring (cont’d.)

Double tube core barrel and core bit greater than AWT (core>1 1/8″) reduces the breakage inside the drill barrel (too large is not good either).

Using recovery ratio and RQD as measures of quality (see eqs. 2.70, 2.71 on p. 117). Using unconfined and high-pressure triaxial tests on the recovered samples (note: provides strength and deformation of the sound rock only, not the rock mass).

Recovery Ratio = Length of rock recoveredTheoretical length of rock recovered

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Soil SamplingRock Coring (cont’d.)


RQD = Rock Quality Designation = L of recovered pieces 4" sizeTheoretical length of rock cored

Figure 2.38 Rock coring: (a) single-tube core barrel; (b) double-tube core barrel


Double tube core barrel is the standard.

Outer barrel rotates with cutting bit.

Inner barrel is either fixed or swivel type (with bearings) that retains core sample.

Core diameters generally range from 21 to 85 mm (0.85 to 3.35 inch).

NX core: standard diameter = 54 mm (2.15 inches).

ASTM C42: The diameter of cores for determining f’c in load bearing structural members shall be at least 3.70 in.

ROCK EXPLORATIONCoring – Double Tube Core


Outer Barrel Assembly

Inner Barrel Assembly

Soil Sampling

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Good for obtaining core samples in fractured rock and highly weathered rocks.

Outer core barrel for initial cut and second barrel to cut finer size. Third barrel to retain cored samples.

Reduces frictional heat that may damage samples.

ROCK EXPLORATIONCoring – Triple Tube Core


Soil Sampling



• Rotary wash with water, foam, or drilling mud (bentonitic or polymeric slurries).

• Fluids reduce wear on drilling and coring bits by cooling.

• Fluids remove cuttings & rock flour.

• Re-circulate to filter fluids and to minimize impact on environment

ROCK EXPLORATIONCoring – Drilling Fluids Notes

Soil Sampling

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• Stabilizes boreholes

• Driven casing

• Drilled-in casing

• Dual wall reverse circulation method

• Use in areas with expected large losses in drilling fluid

• Inner section for sampling

• Outer casing maintains fluids for drilling

ROCK EXPLORATIONCoring – Casing

Drilled-In Dual Wall

Soil Sampling



ROCK EXPLORATIONCore Recovery

• Core Runs taken in either 5- or 10-foot sections.

• Log the amount of material recovered.

• Core Recovery is percentage retained.

• RQD (Rock Quality Designation) is a modified core recovery.

• ASTM D5079 Standard Practice for Preserving and Transporting Rock Core Samples

Soil Sampling

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ROCK EXPLORATION

Core Recovery

• Cores should be stored in either wooden boxes or corrugated cardboard box.

• Box marked with boring number, depth of core run, type core, bit type, core recovery (CR), rock type, RQD, and other notes.

• Core operations should be documented:

• Loss of fluid

• Drilling rates

• Sudden drop in rods

• Poor recovery

• Loss of core

Soil Sampling

14.528 Drilled Deep Foundations – Samuel Paikowsky 182 of 235Text & Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations

ROCK EXPLORATIONCore Recovery

• The RQD is a modified core recovery.

• Measure of the degree of fractures, joints, and discontinuities of rock mass

• RQD = sum of pieces > 100 mm (4 inches) divided by total core run.

• Generally performed on NX-size core.

Soil Sampling

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ROCK EXPLORATIONCare & Preservation

• Routine: Core boxes

• Special: Plastic sleeves

• General: Avoid exposure to shock and vibration during handling and transport.

• Non-natural fractures may result from excessive movements, temperatures, and exposure to air.

• Store for future reference

Soil Sampling


Soil Sampling

Groundwater Measurements

Observation of groundwater elevation using an observation well. Allows the monitoring of groundwater levels with time and for environmental tracking purposes. Initial readings need to be taken after groundwater stabilization is obtained, at least 24 hours after the end of drilling (in low permeability soils may require much longer time).

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Soil Sampling

(Guide to Geotechnical Instrumentation, SLOPE INDICATOR, 2004)


Piezometers


Example of Vibrating Wire Piezometers

•Manufactured by Geokon, Inc.

Soil Sampling

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Soil SamplingGroundwater Measurements

(cont’d.) Local Water Pressure can be

measured utilizing a piezometer. Such readings are necessary in low permeability soils, which exhibit variation of pressure with time, e.g.: following pile driving, surcharge application (to establish the progress of consolidation) or for artesian or separated acquifers. Piezometer can be “pushed” into the ground as a self contained unit or installed in a borehole.

(Guide to Geotechnical Instrumentation, SLOPE INDICATOR, 2004)


Soil Sampling

Piezometers

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Soil SamplingGeophysical Explorations

Wave Types: Three major wave types propagate through the soil upon impact or vibration;

Rayleigh Waves = surface WavesP-waves = pressure or plane waveS-waves = shear waves

Being interested in waves propagating and reflecting from various soil layers, P-waves are the fastest penetrating waves, and therefore of interest.



Wave Types:Three major wave types propagate through the soil upon impact or vibration;

Rayleigh Waves = surface WavesP-waves = pressure or plane waveS-waves = shear waves

Being interested in waves propagating and reflecting from various soil layers, P-waves are the fastest penetrating waves, and therefore of interest.

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Wave Types: (cont’d)

Directionof Travel

DirectionOf Travel

Pressure Wave Shear WavesP S


GEOPHYSICAL METHODS – MECHANICAL WAVES

Crosshole Tests (CHT)(FHWA NHI-01-031 Figurer 5-25)

Seismic Refraction (SR)(courtesy of www.enviroscan.com)

Also Available:Downhole Tests (DHT)Spectral Analysis of Surface Waves (SASW)

Soil Sampling

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Seismic Refraction survey:Section 2.26 (p. 118) describes the ability to identify the variation in the layers and the subsurface based on wave velocity and time measurements utilizing impact (point A) and geophones at the ground surface at known locations (B, C, D)



Seismic Refraction survey: (cont’d.)1. The first arrival at locations B, C, D is measured as t1, t2, t3, etc.

2. Plotting the time vs. the distance from the source enables to identify zones of different slopes reflecting the various velocities.

Slope of

Slope of

Slope of

1

1

vab

2

1

vbc

3

1

vcd

Here, v1, v2, v3,…, are the P-wave velocities in layers I, II, III, …, respectively

Figure 2.42 Seismic refraction survey

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Seismic Refraction survey: (cont’d.)3. Determine the Thickness of the top Layer:

(eq. 2.73, p.120)

The value of xc can be obtained from the plot, as shown in Figure 2.31b (p. 107).

4. Determine the Thickness of the Second Layer:

(eq. 2.74, p.120)

Here Ti2 is the time intercept of the line cd in Fig. 2.42b, (p.119) extended backwards.

cxvv

vvZ

12

121 2

1

22

23

23

13

21

23

122 22

1

vv

vv

vv

vvZTZ i


Soil Sampling Geophysical Explorations

14.431 Foundation & Soil Engineering – Samuel Paikowsky

Seismic Refraction survey: (cont’d.)Findings:

The velocities of P waves in various layers indicate the types of soil or rock that are present below the ground surface. The range of the P-wave velocity that is generally encountered in different types of soil and rock at shallow depths is given in Table 2.12

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Soil Sampling

Geophysical Explorations

Seismic Refraction survey: (cont’d.)

Applications and Limitations1. The survey enables to cover large areas in a short time at a

relatively low cost.

2. The conditions at the site need to be adequate, namely: relatively uniform, deep ground water surface, P-wave velocity v1<v2<v3…

3. In saturated soils/fractured rock the P-wave velocity often resumes that of water (1500m/s)

4. Verification with actual drilling is needed.


Ground Penetrating Radar (GPR)(photographs courtesy of http://www.geomodel.com)

GEOPHYSICAL METHODS – ELECTROMAGNETIC WAVES

Electrical Resistivity (ER) Survey Results(FHWA NHI-01-031 Figurer 5-35)

Other Methods:Magnetometer Surveys (MS)Resistivity Piezocone (RCPTu)

Electromagnetic (EM) Survey(FHWA NHI-01-031 Figurer 5-35)

Soil Sampling

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ADVANTAGES OF GEOPHYSICSNondestructive and/or non-invasive

Fast and economical testing Theoretical basis for interpretation

Applicable to soils and rocks

DISADVANTAGES OF GEOPHYSICSNo samples or direct physical penetration

Models assumed for interpretationAffected by cemented layers or inclusions.Results influenced by water, clay, & depth.

GEOPHYSICAL METHODS

GPR Results for UST(FHWA NHI-01-031 Figure 5-33)

MS Results for Oil Well Location(FHWA NHI-01-031 Figure 5-37)

Soil Sampling



Figure courtesy of FHWA NHI Course 132031Subsurface Investigations

Soil Sampling

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INSITU TEST METHOD ADVANTAGES/DISADVANTAGES

Method Advantages Disadvantages

VST

• Assessment of undrained shear strength of clays.

• Simple test and equipment.

• Measure inplace sensitivity.

• Long history of use in practice, particularly embankments, foundations, & cuts.

• Limited to soft to stiff clays & silts with suv

< 200 kPa

• Slow & time-consuming

• Raw suv needs empirical correction

• Can be affected by sand seams and lenses

Soil Sampling



DCP• Quick

• Low cost

• Limited depth range

• Limited correlations of DCP values to soil properties.

SPT

• Obtain Sample + Number

• Simple & rugged device at low cost

• Suitable in many soil types

• Can perform in weak rocks

• Available throughout the U.S. and worldwide.

• Many correlations with soil engineering properties exist

• Obtain Sample + Number

• Disturbed sample (index tests only)

• Crude number for analysis

• Not applicable in soft clays and silts

• High variability and uncertainty

• Many correlations with soil engineering properties exist

Soil SamplingINSITU TEST METHOD

ADVANTAGES/DISADVANTAGES

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CPT

• Fast and continuous profiling of strata.

• Economical and productive.

• Results not operator-dependent.

• Strong theoretical basis for interpretation.

• Particularly suited to soft soils.

• High capital investment

• Requires skilled operator for field use.

• Electronics must be calibrated & protected.

• No soil samples.

• Unsuited to gravelly soils and cobbles.

DMT

• Simple and Robust Equipment.

• Repeatable and Operator-Independent.

• Quick and Economical.

• Theoretical Derivations for elastic modulus, strength, stress history.

• Difficult to push in dense and hard materials.

• Primarily established on correlative relationships.

•Needs calibration for local geologies.

Soil SamplingINSITU TEST METHOD

ADVANTAGES/DISADVANTAGES


FLAT PLATE DILATOMETER (DMT) (ASTM D6635-01(2007))


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Calibrations: A, B (positive values)

Readings: contact pressure "A" and expansion pressure "B" with depth

Corrections for membrane stiffness in air: p0 = 1.05(A + A) - 0.05(B - B)

p1 = B -B

DMT INDICES:

• ID = material index = (p1-po)/(po-uo)

• ED = dilatometer modulus = 34.7(p1-po)

• KD = horizontal stress index

= (po-uo)/vo’

FLAT PLATE DILATOMETER (DMT) (ASTM D6635-01(2007))

• B

• A

Text courtesy of FHWA NHI Course 132031 Subsurface Investigations

Soil Sampling


Marchetti Device (ASCE JGE, March 1980; ASTM Geot. Testing J., June 1986)

FLAT PLATE DILATOMETER (DMT) (ASTM D6635-01(2007))Manual Reading System (Standard)


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FLAT PLATE DILATOMETER (DMT) (ASTM D6635-01(2007))Computerized System (Standard)


Soil Sampling


00

01,up

ppIIndexMaterial D

p0

p1

0.1 1 10 Material Index (ID)

0.6 1.8

Clay Silt Sand

FLAT PLATE DILATOMETERDETERMINATION OF SUBSURFACE DATA

Courtesy of FHWA NHI Course 132031 Subsurface Investigations

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FLAT PLATE DILATOMETERDETERMINATION OF SUBSURFACE DATA

Figure 43. FHWA IF-02-034

Soil Sampling


FLAT PLATE DILATOMETER (DMT) (ASTM D6635-01(2007))Results – Charleston, SC Project

Soil BehaviorClassification

ED with Depth

Raw Data & Calibrations

DMT Results courtesy of Dr. Edward Hajduk and WPC Engineering Inc.

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0

2

4

6

8

10

12

14

16

0 200 400 600 800

Modulus ED (atm)

0

2

4

6

8

10

12

14

16

0 500 1000 1500

Pressure (kPa)

Dep

th (

me

ters

)

PoP1

0

2

4

6

8

10

12

14

16

0 1 10

Material Index ID

Clay Silt

0

2

4

6

8

10

12

14

16

0 5 10 15

Horiz. Index KD

FLAT PLATE DILATOMETER (DMT) (ASTM D6635-01(2007))Results - Piedmont Residuum, Charlotte, NC

DMT Results courtesy of FHWA NHI Course 132031 Subsurface Investigations

Soil Sampling


SPT-CPT-DMT COMPARISON

Also see Hajduk, E.L., Meng,J., Wright, W.B., and Zur, K.J.(2006). “ DilatometerExperience in the Charleston,South Carolina Region”, 2ndInternational Conference onthe Flat Dilatometer,Washington, D.C.

From Local Project in

Charleston, SC Area (2000)

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PRESSUREMETER TEST (PMT) (ASTM D4719-07)


Soil Sampling


0

1

2

3

4

5

0 100 200 300 400 500 600

Volume Change (cc)

Pre

ssu

re (

tsf)

0

1

2

3

4

5

0 10 20 30 40 50

Creep (cc/min)

Pre

ssu

re (

tsf)

PRESSUREMETER (PMT) (ASTM D4719-07)Results – Utah DOT Project

PMT Results courtesy of FHWA NHI Course 132031 Subsurface Investigations

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NE SubsurfaceCombining NE Geology and



Agenda

Rock Core Viewing (next lecture)

New England Surficial Geology Overview

Typical Soil Types

Typical Soil Stratigraphic Sequences

Examples of Applied Subsurface Evaluation

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Rock Coring


Rock Coring

RQD = Rock Quality Designation

RQD = Σpieces >10cm x 100Total Core run

RQD Rock mass quality <25% very poor 25-50% poor 50-75% fair 75-90% good 90-100% excellent

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Direct Push – Soil Sampling


More Direct Push –Soil Sampling

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Sonic Drilling – Sample Recovery


Soil Sampling

Split Spoon Sampler

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Glacial Stratigraphy – Concord, MA


Glacial Stratigraphy – Concord, MA (2)

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Glacial Stratigraphy – Glastonbury, CT


Glacial Stratigraphy – Everett, MA

226

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center of mass

trajectoryclay lens?

• 2x longer than RDX plume • Plume shallows beyond FPR • Evidence of a hydraulically significant confining layer

Frank Perkins Rd.

Pew Rd.

current RDX extent

Glacial Stratigraphy- Cape Cod, the Mass Military Reservation


Glacial Stratigraphy-Western MA

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Glacial Stratigraphy - Maine

bedrock

Stratified Drift

till


Glacial Stratigraphy – Midwest Schematic

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Central Artery Stratigraphy

231

Boston Blue Clay

Till

Bedrock (Argillite)

Fill

Organic Silt


Boston- The Central Artery

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Boston- Central Artery Dewatering Model Results


Hydraulic Conductivity Ranges

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Engineering Characteristics of Glacial Deposits

235

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