geotech field investigation

NYSDOT Geotechnical Page 4-1 December 10, 2013

Design Manual Rev. 1

GEOTECHNICAL DESIGN MANUAL

CHAPTER 4

GEOTECHNICAL FIELD INVESTIGATION



(Intentionally left blank)

Table of Contents



4.1 OVERVIEW .................................................................................................................... 4-5

4.2 DESIGN-BID-BUILD AND DESIGN-BUILD .............................................................. 4-5

4.3 SUBSURFACE EXPLORATION PROGRAM DEVELOPMENT ............................... 4-5

4.3.1 Terrain Reconnaissance ......................................................................................... 4-5

4.3.1.1 Developing a Terrain Reconnaissance Report ......................................... 4-6

4.3.2 Methods of Subsurface Exploration ...................................................................... 4-9

4.3.2.1 Test Pits .................................................................................................... 4-9

4.3.2.2 Test Borings ............................................................................................. 4-9

4.3.2.3 In-Situ Sampling Methods ..................................................................... 4-10

4.3.2.4 In-Situ Soil Testing Methods ................................................................. 4-10

4.3.2.4.1 Standard Penetration Test ...................................................... 4-10

4.3.2.4.2 Dynamic Cone Penetrometer ................................................. 4-11

4.3.2.4.3 Cone Penetrometer Test ........................................................ 4-11

4.3.2.4.4 Flat Plate Dilatometer Test .................................................... 4-12

4.3.2.4.5 Pressuremeter Test ................................................................ 4-12

4.3.2.4.6 Field Vane Shear Test ........................................................... 4-13

4.3.2.5 Geophysical Testing Methods................................................................ 4-15

4.3.2.5.1 Surface Wave Methods ......................................................... 4-15

4.3.2.5.2 Downhole Shear Wave Velocity Methods ............................ 4-15

4.3.2.5.3 Crosshole Shear Wave Velocity Methods ............................. 4-15

4.3.2.5.4 Seismic Refraction ................................................................ 4-16

4.3.2.5.5 Seismic Reflection ................................................................. 4-16

4.3.2.5.6 Resistivity .............................................................................. 4-16

4.3.2.6 Falling Weight Deflectometer................................................................ 4-16

4.3.2.7 Hydraulic Conductivity Testing Methods .............................................. 4-17

4.3.2.7.1 Percolation Test ..................................................................... 4-17

4.3.2.7.2 Well Pumping Tests .............................................................. 4-18

4.3.2.7.3 Seepage Tests ........................................................................ 4-18

4.3.2.7.4 Packer Permeability Tests ..................................................... 4-18

4.3.2.7.5 Other Tests ............................................................................ 4-19

4.4 PHASING OF SUBURFACE INVESTIGATIONS ..................................................... 4-19

4.5 SUBSURFACE EXPLORATION CRITERIA ............................................................. 4-20

4.5.1 Bridge Foundations ............................................................................................. 4-21

4.5.2 Retaining Walls ................................................................................................... 4-22

4.5.3 Embankments ...................................................................................................... 4-24

4.5.4 Large Cuts and Excavations ................................................................................ 4-24

4.5.5 Culverts ............................................................................................................... 4-25

4.5.6 Noise Barrier Walls ............................................................................................. 4-26

4.5.7 Overhead Signs, Traffic Signals, and Light Standards ....................................... 4-27

4.5.8 Pavement Structures ............................................................................................ 4-28

4.5.9 Infiltration Basins and Wetland Mitigations ....................................................... 4-28

4.5.10 Trenchless Pipe Installation ............................................................................... 4-29

Table of Contents

NYSDOT Geotechnical -4 December 10, 2013


4.5.11 Other Applications ............................................................................................. 4-29

4.6 SUBSURFACE EXPLORATION AND SAMPLE TYPES ......................................... 4-29

4.6.1 Identification System for Subsurface Explorations ............................................. 4-30

4.6.2 Identification System for Individual Soil and Rock Samples ............................. 4-31

4.7 FIELD EXPLORATIONS AND SAMPLING .............................................................. 4-32

4.7.1 Soil and Rock Sampling in Test Borings ............................................................ 4-32

4.7.1.1 Bulk Samples ......................................................................................... 4-32

4.7.1.2 Split-Barrel Sampling ............................................................................ 4-32

4.7.1.2.1 Progressing the Test Boring for Sampling ............................ 4-33

4.7.1.2.2 Obtaining a Sample ............................................................... 4-33

4.7.1.2.3 Packaging and Identification of Samples .............................. 4-34

4.7.1.3 Thin-Walled Tube Sampling.................................................................. 4-34

4.7.1.3.1 Progressing the Test Boring for Sampling ............................ 4-34

4.7.1.3.2 Obtaining a Sample ............................................................... 4-34

4.7.1.3.3 Packaging, Identification, and Transporting of Samples ...... 4-36

4.7.1.4 Rock Core Sampling .............................................................................. 4-36

4.7.1.4.1 Obtaining a Rock Core .......................................................... 4-36

4.7.1.4.2 Packaging and Identification of Rock Cores ......................... 4-37

4.7.2 Test Boring Logs ................................................................................................. 4-37

4.8 REFERENCES .............................................................................................................. 4-40

CHAPTER 4

Geotechnical Field Investigation



4.1 OVERVIEW

This Chapter addresses the geotechnical field investigation, including the development of the

subsurface exploration program, the methods of generating subsurface information, and the

criteria to be applied for test borings in the various conditions that will be encountered. It is

organized by activities and policies involved prior to, during, and after exploration.

4.2 DESIGN-BID-BUILD AND DESIGN-BUILD

The requirements of this Chapter shall be applied to projects designed In-House, projects

designed by Consultants, and Design-Build projects.

When the subsurface exploration program is being prepared by the Departmental Geotechnical

Engineers, previous soil borings in the vicinity of the project, nearby utilities and structures,

USDA soils maps, USGS topographic maps, aerial photographs, and wetland inventory maps as

described in NYSDOT GDM Chapter 2, will be considered in the development of the program.

The Regional Geotechnical Engineer is responsible for determining site accessibility and

potential impacts to sensitive environmental areas. In addition, the Regional Geotechnical

Engineer is responsible for coordination of all traffic control needs, and issues regarding access

permits and right-of-entry notifications to impacted property owners.

When the subsurface exploration program is being prepared by a Geotechnical Engineering

Consultant, the Consultant shall submit to the Regional Geotechnical Engineer, for review and

acceptance, a detailed subsurface exploration plan and proposal prior to the commencement of

any field operations. The program shall describe the anticipated soil or rock stratification used as

the basis of the planned explorations. The program shall outline proposed exploration methods,

and locations and termination criteria for all explorations. The subsurface exploration plan shall

conform to the requirements of this Manual and of the applicable NYSDOT specifications.

Where explorations must be conducted in sensitive environmental areas or in high hazard traffic

areas, the exploration program shall describe any special access or traffic control requirements

necessary to protect the interests of the Department during the field exploration phase. The

Consultant is responsible for all access requirements, access permits, right-of-way notifications,

and traffic control. All traffic control shall conform to the latest Department guidelines.

4.3 SUBSURFACE EXPLORATION PROGRAM DEVELOPMENT

In the development of a subsurface exploration program, the existing site conditions, available

and applicable exploration methods, and available and applicable in-situ testing methods must be

considered. This section discusses such considerations.

4.3.1 Terrain Reconnaissance

Terrain reconnaissance is the operation of reviewing available information from various sources

and reconnoitering the landscape, to view it with regard to its suitability for engineering

purposes, describing the extent and characteristics of the areas encountered, and making an

engineering interpretation of the findings.

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Terrain reconnaissance and appraisal operations are performed for the following purposes:

1. To serve as a basis for the appraisal of terrain conditions by correlating the characteristics

of the various soil areas with the past construction experiences and performances of

existing highways on similar areas.

2. To indicate to the highway planning and location Engineers the relative merits and

potential design and construction problems for the mapped areas of different terrain

conditions along the general route, so that, if feasible, the optimum areas be occupied and

the adverse areas avoided.

3. To serve as a guide in establishing the optimum grade line relative to topography and

subsurface conditions.

4. To serve as a general guide for the efficient planning of the necessary subsurface

exploration, testing and analysis program for the line finally selected. This reduces the

surveys in the "good" areas to an efficient minimum, and permits effective concentrations

in the problem areas.

5. To indicate the general earthwork construction material situation, and to indicate the

probable locations of borrow and granular materials so that those areas may be explored

and sampled for specification and cost purposes.

Refer to NYSDOT GDM Chapter 2 for related discussion.

4.3.1.1 Developing a Terrain Reconnaissance Report

A Terrain Reconnaissance Report describes the anticipated soils to be encountered along a length

of proposed roadway. Most of the soil data and information is derived from the National

Cooperative Soil Survey, accessed through the USDA National Resources Conservation Service.

Information from this source considers the near-surface (within 8 feet) soils. Any preliminary or

record logs are also included in the analysis.

Subject areas are delineated into Areas of Interest (AOI’s). The AOI’s are depicted in maps and

Engineering Properties, Water Features, Particle Size & Coarse Fragments, and Physical Soil

Properties are presented for the soil types mapped in each AOI. Descriptions of the mapped types

are typically presented at the end of the report.

Typically, for the initial geotechnical field investigation, an examination of the site for the

development of the Terrain Reconnaissance Report is essential. The site examination is a visual

assessment of the territory. When viewing the landscape in the field, a logical comparison may

be made with the soil map of that location. In many of the new soil maps, geologic origin is

neglected in favor of a slope percentage. For example:

• A Palmyra soil located on an esker may be mapped Palmyra 15-20% slope. However, an

outwash terrace face may also be mapped Palmyra 15-20% slope.

• A soil mapped as Alluvial land in the uplands, which may actually be an inwash soil over

glacial till and not a flood plain soil.

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Figure 4-1 Generalized Terrain Map Example

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Figure 4-2 Generalized Terrain Map Legend Example

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4.3.2 Methods of Subsurface Exploration

Assuming access and utility clearances have been obtained and a survey base line has been

established in the field, field explorations are begun. Many methods of field exploration exist;

some of the more common are described below. These methods are often augmented by in-situ

testing. The testing described in this Chapter provides the Departmental Geotechnical Engineer

with soil and rock parameters determined in-situ. This is important, especially on those projects

involving soft clays, loose sands, and/or sands below the water table, due to the difficulty of

obtaining representative samples suitable for laboratory testing. For each test included, a brief

description of the equipment, the test method, and the use of the data is presented.

4.3.2.1 Test Pits

Test Pits are the simplest methods of inspecting subsurface soils. Test pits consist of excavations

performed by hand, backhoe, or dozer. Hand excavations are often performed with shovels or

posthole diggers. Test pits offer the advantages of speed and ready access for sampling.

However, test pits are severely hampered by limitations of depth and by the fact that

advancement through soft or loose soils or below the water table can be extremely difficult. Test

pits are used to examine large volumes of near surface soils and can be used to obtain bulk

samples for additional testing.

4.3.2.2 Test Borings

The term “Test Boring” applies to a bored hole method of subsurface investigation that involves

the in-situ sampling and/or testing of soil, rock, and water. The test boring may be progressed as

an open hole that utilizes soil or rock boring methods to allow sampling or testing at various

depths, or it may be progressed continuously by sampling or testing equipment. If open holes are

utilized, the sampling and/or testing is usually performed below the depth which has been

disturbed by the hole progression. Various methods of soil and rock boring methods for open

holes are discussed below:

• Hand Augers – Hand auger borings are advanced using hand held equipment, typically

in areas where access for standard drilling equipment is restricted. Hand auger borings

are limited in depth by the presence of ground water or collapsible soils that cause caving

in the borehole.

• Hollow-Flight Augers – Hollow-flight augers consist of a continuous flight auger

surrounding a hollow drill stem, which is advanced by rotation. Split spoon and

undisturbed samples are obtained through the hollow drill stem, which acts like a casing

to hold the hole open, so removal of the auger is not necessary for sampling. Refer to

ASTM D6151 - Standard Practice for Using Hollow-Stem Augers for Geotechnical

Exploration and Soil Sampling (AASHTO T306 - Standard Method of Test for

Progressing Auger Borings for Geotechnical Explorations).

• Wash Rotary Method – In a Wash Rotary Boring, a downward pressure is applied

during rapid rotation of hollow drill rods to which a cutting bit is attached. The drill bit

cuts the material and drilling fluid washes the cuttings from the borehole. In most cases

this is the fastest method of advancing a borehole and can be used in any type of soil,

although soils containing considerable amounts of large gravel or boulders could be

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problematic. Drilling mud or casing can be used to keep the borehole open. Split spoon

and undisturbed samples are obtained through the drilling fluid, which holds the borehole

open.

• Rock Boring/Coring - Rock boring through boulders or rock is accomplished by

advancing a core barrel through the rock by the application of downward pressure during

rotation. Circulating water removes ground-up material from the hole while also cooling

the bit. Rock coring involves careful sampling of rock in which the rate of advance is

controlled so as to obtain the maximum possible core recovery. Refer to ASTM D2113 –

Standard Practice for Rock Core Drilling and Sampling of Rock for Site Investigation.

4.3.2.3 In-Situ Sampling Methods

In-situ sampling methods are used to obtain a portion of the subsurface material for analysis. In-

situ methods include soil sampling by SPT, rock core sampling, and undisturbed sampling. These

methods are described in Section 4.3.2.4.1 Standard Penetration Test, Section 4.7.1.4 Rock Core

Sampling, and Section 4.7.1.3 Thin-Walled Tube Sampling respectively.

4.3.2.4 In-Situ Soil Testing Methods

In-situ soil testing methods are used to obtain general strength, friction, and pore water

information for soils in their existing state. The methods result in disturbance and displacement

of the soil. In many cases the information obtained can be correlated to other design parameters.

Various testing methods are described below and the suitability of the methods to various soil

types is presented in Table 4-1.

4.3.2.4.1 Standard Penetration Test

The Standard Penetration Test (SPT) is the most widely used field test, having the advantages of

simplicity, a wide variety of correlations for its data, and the fact that a sample is obtainable with

each test. As discussed previously, a standard split-barrel sampler attached to a drill rod is

advanced into the soil by impacts from a 140-pound (625 N) automatic or safety hammer

dropping from a height of 30 inches (750 mm). The sampler is advanced a total of 18 inches (450

mm), and the number of blows required to advance the sampler for each of three 6-inch (150

mm) increments is recorded. The sum of the number of blows for the second and third

increments is called the Standard Penetration Value, or more commonly, N-value, which is

reported in blows per foot (300 mm). Tests shall be performed in accordance with ASTM D1586

- Standard Test Method for Penetration Test and Split-Barrel Sampling of Soils (AASHTO T206

- Standard Method of Test for Penetration Test and Split-Barrel Sampling of Soils).

The number of blows for each 6-inch increment (150 mm) is recorded on the Soil Test Boring

Logs, along with the type of hammer used and any notes regarding the driving effort (e.g., the

sampler was advanced under the weight of the rods or hammer without blows, if the sampler was

plugged, refusal before completing 6-inch increment, etc.). Refer to NYSDOT GDM Chapter 8

for related discussion.

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4.3.2.4.2 Dynamic Cone Penetrometer

The Dynamic Cone Penetrometer is a dynamic method of measuring a soil’s in-situ resistance to

penetration. In the test, a 17.6 lb (8 kg) weight is repeatedly dropped from a height of 22.6 in

(575 mm), driving a cylindrical rod with a cone-shaped point into the ground. The penetration

per blow is measured and test data can be correlated to bearing capacity, in-situ density, and

other parameters. The equipment used for the test is man portable and is commonly performed in

conjunction with hand auger borings. The standard for Dynamic Cone Penetrometer testing is the

procedure presented by Sowers and Hedges (1966). The penetrometer resistance values can be

correlated to Nmeas by performing an SPT adjacent to the penetrometer test.

4.3.2.4.3 Cone Penetrometer Test

The Cone Penetrometer Test (CPT) is a quasi-static penetration test in which a cylindrical rod

with a conical point is advanced through the soil at a constant rate. The cone penetrometer

measures the resistance to penetration at the tip of the penetrometer, the end-bearing component

of resistance. The equipment used is generally truck or trailer mounted. A series of tests

performed at varying depths at one location is commonly called a sounding.

The penetrometer can be used in sands or clays, but not in rock or other extremely dense soils.

Since soil samples are not generally obtained with penetrometer soundings, they should be

augmented by SPT borings or other borings with soil samples taken, and the CPT correlated to

the in-situ soils.

Several types of penetrometer are in use, including mechanical (Dutch) cone, mechanical

friction-cone, electric cone, electric friction-cone, and electro-piezocone. Regarding the various

types:

• Friction-cone penetrometers are equipped with a friction sleeve, which provides the

added capability of measuring the side friction component of resistance.

• Mechanical penetrometers have telescoping tips allowing measurements to be taken

incrementally, generally at intervals of 8 inches (200 mm) or less.

• Electronic penetrometers use electronic force transducers to obtain continuous

measurements with depth.

• Electro-piezocones are also capable of measuring pore water pressures during

penetration.

Of these, the only cone penetrometer type allowed is the electro-piezocones or some variation

thereof (e.g., seismic electro-piezocones).

Cone dimensions of a 60-degree tip angle and a 1.55 in2 (10 cm

2) projected end area are

standard. The outside diameter of the friction sleeve is the same as that of the base of the cone.

Penetration rates are between 10 to 20 mm/sec. The appropriate test method is described in

ASTM D5778 - Standard Test Method for Performing Electronic Friction Cone and Piezocone

Penetration Testing of Soils (electro-piezocones).

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The electro-piezocones can also be used to measure the dissipation rate of the excessive pore

water pressure. This type of test is useful for soils that are very sensitive to sampling techniques,

such as fibrous peat, muck, or soft clays. In such an application, the cone is equipped with a

pressure transducer that is capable of measuring the induced water pressure. Pore water pressures

are measured immediately and at several time intervals thereafter. Electro-piezocones can be

fitted with other instrumentation above the friction sleeve (e.g., geophone, inclinometer, nuclear

density equipment, etc.).

Cone penetrometer data is plotted showing the tip stress, the friction resistance, and the friction

ratio vs. depth. Pore pressures can also be plotted with depth and correlations of test results have

been made to other soil parameters. See NYSDOT GDM Chapter 5 for presentation of CPT data.

4.3.2.4.4 Flat Plate Dilatometer Test

A Flat Plate Dilatometer is a 3.75-inch wide and 0.55-inch thick stainless steel blade with a thin

2.4-inch diameter expandable metal membrane on one side. With the membrane flush with the

blade surface (unexpanded), the blade is either pushed or driven into the soil using a drill rig.

Rods carry pneumatic and electrical lines from the membrane to the surface. At the test elevation

(typically depth intervals of 12 inches), pressurized gas is applied to expand the membrane. Both

the pressure required to begin membrane movement and that required to expand the membrane

into the soil 0.04 inches (1.1 mm) are measured. Additionally, the pressure corresponding to the

return of the membrane to its original position upon venting may be recorded. Through

developed correlations, information can be deduced concerning material type, pore water

pressure, in-situ horizontal and vertical stresses, void ratio or relative density, modulus, shear

strength parameters, and consolidation parameters.

Compared to the pressuremeter, the flat dilatometer has the advantage of reduced soil

disturbance during penetration. Tests shall be performed in accordance with ASTM D6635 -

Standard Test Method for Performing the Flat Plate Dilatometer.

4.3.2.4.5 Pressuremeter Test

A Pressuremeter Test is performed by inserting a cylindrical probe into an open borehole to the

test depth, then inflating the probe’s flexible membrane laterally to push against the borehole’s

soil wall. The measured volume change of the membrane is plotted against the applied pressure.

Results are interpreted based on semi-empirical correlations from past tests and observation. In-

situ horizontal stresses, shear strength, bearing capacities, and settlement can be estimated using

these correlations. The pressuremeter test results can be used to obtain load transfer curves (p-y

curves) for lateral load analyses.

While tests can be done in soft clay or loose sands, the test is best used in dense sands, hard clays

and weathered rock which cannot be tested with push equipment. The pressuremeter test is very

sensitive to borehole disturbance and the data may be difficult to interpret for some soils. Tests

shall be performed in accordance with ASTM D4719 - Standard Test Method for Prebored

Pressuremeter Testing in Soils.

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4.3.2.4.6 Field Vane Shear Test

A Field Vane Shear Test consists of advancing a four-bladed vane to the test depth and applying

a measured torque at a constant rate until the soil fails in shear along a cylindrical surface. The

torque measured at failure provides the undrained shear strength of the soil. A second test run

immediately after remolding at the same depth provides the remolded strength of the soil and

thus information on soil sensitivity. Tests shall be performed in accordance with ASTM D2573 -

Standard Test Method for Field Vane Shear Test in Cohesive Soil (AASHTO T223 - Standard

Method of Test for Field Vane Shear Test in Cohesive Soil).

This method is commonly used for measuring shear strength in soft clays and organic deposits. It

should not be used in stiff and hard clays. Results can be affected by the presence of gravel,

shells, roots, or sand layers. Shear strength may be overestimated in highly plastic clays and a

correction factor should be applied.

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In-Situ Test Method

Suitable Soils (1)

Unsuitable Soils

Correlated Properties Remarks

Standard Penetration Test

(SPT)

Sand, Clay, Residual

Soil Gravel

Sand and residual soil effective peak internal friction angle, clay undrained peak shear strength, soil modulus.

SPT repeatability is highly variable. Disturbed samples. Very variable Su correlations are available for clays.

Cone Penetrometer (CPT) or Piezocone with pore pressure

measurements (CPTu)

Sand, Silt, Clay,

Residual Soil

Gravel

Sand, silt, and residual soil effective peak internal friction angle, clay and residual soil undrained peak shear strength, soil modulus.

Continuous evaluation of soil properties. CPT is very repeatable. No samples recovered.

Flat Plate Dilatometer (DMT)

Sand, Clay, Residual

Soil Gravel

Sand, silt, and residual soil effective peak internal friction angle, clay and residual soil undrained peak shear strength, overconsolidation ratio, at-rest pressure coefficient, soil modulus.

Unreliable results may occur with very dense sand, cemented sand, and gravel. No samples recovered.

Pressuremeter

Dense Sand, Hard

Clay, Weathered

Rock

Soft Clay, Loose Sands

Horizontal stresses, shear strength, bearing capacities, settlement.

Results can be used to obtain load transfer curves for lateral load analyses. Sensitive to borehole disturbance and data may be difficult to interpret for some soils.

Field Vane Shear (VST)

Clay Sand,

Residual Soil, Gravel

Clay undrained peak shear strength.

May overestimate shear strength. Very soft clays need to be corrected. Unreliable results may occur with fissured clays, varved clays, highly plastic clays, sand, residual soil, and gravel. VST repeatability may be variable with rate of rotation. No samples recovered.

(1) Residual soils frequently have a dual USCS description of SM-ML and behave as both cohesive soils and cohesionless soils because the residuum soil is close to the opening size of the U.S. No. 200 Sieve (0.075 mm).

Table 4-1 Soil Suitability of In-Situ Testing Methods (modified from Canadian Geotechnical Manual (1982) and Holts and Kovacs (1981))

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4.3.2.5 Geophysical Testing Methods

Geophysical testing methods are non-destructive testing procedures applying wave and electrical

current technologies which can provide general information on the subsurface profile, depth to

bedrock or water, location of granular borrow areas, peat deposits or subsurface anomalies, etc.,

and can provide an indication of certain material properties (e.g., shear wave velocity).

Geophysical testing methods are not limited to subsurface conditions, but can also be used to

evaluate existing structures, foundations, and pavements. Refer to FHWA-IF-04-021,

Application of Geophysical Methods to Highway Related Problems, for additional information

on the use of geophysical test methods for applications other than subsurface conditions.

4.3.2.5.1 Surface Wave Methods

Surface wave methods consist of Spectral Analysis of Surface Waves or Multi-channel Analysis

of Surface Waves. Both methods are used to measure the thickness, depth, and shear wave

velocity of a layer. While Spectral Analysis will typically have 2 geophones, Multi-channel will

have additional geophones spread over a larger area.

The shear wave velocity is more of a general velocity, rather than a discrete velocity of a layer.

Discrete shear wave velocity may be determined by crosshole or downhole methods. Typically

the surface wave profiles are limited to a depth of approximately 130 feet using man portable

equipment. Additional depth can be achieved, but heavier motorized equipment is required.

4.3.2.5.2 Downhole Shear Wave Velocity Methods

Downhole methods for determining shear wave velocity differ from surface methods in that

equipment is placed below the ground surface. In downhole methods, either geophone is lowered

into the casing placed in the ground or a seismic cone penetrometer (SCPT) is pushed into the

ground, with a geophone typically mounted above the friction sleeve on the cone. With either

method, a shear wave is induced at the ground surface and the time for arrival is measured at the

geophone.

If casing is used, care must be taken during construction to assure that the casing is plumb. A

major limitation of the SCPT is refusal to advance in dense soils.

4.3.2.5.3 Crosshole Shear Wave Velocity Methods

In Crosshole Shear Wave Velocity testing, shear wave velocities are determined between a series

of vertical cased holes. A downhole hammer and geophone are lowered to the same depth in

different holes. The hammer is tripped and the time for the shear wave to travel to the geophone

is recorded. The major limitation to the crosshole method is the expense of installing the required

casings. Also, care must be taken during installation of the casings to assure that they are plumb

and that equal depths are within the same horizontal plane.

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4.3.2.5.4 Seismic Refraction

Seismic refraction is used to determine the depth to bedrock. The basic operation of a seismic

refraction survey uses one or two 200 ft. cables, each having connections for 12 equally spaced

geophones. The cables are hooked up to a seismograph. A seismic energy source is required for

producing seismic waves. A sledge hammer is typically used for depths less than 50 feet and

either a drop weight or a black powder charge is used for depths between 50 and 100 feet. The

seismic compression waves penetrate the overburden material and refract along the bedrock

surface. After each shot, the time it takes for the compression wave to arrive at each geophone is

recorded by the seismograph.

A seismic refraction survey works well for depths less than 100 feet. It can be used for up to 4

soil or rock layers; however, each layer must have a higher shear wave velocity than the

overlying layer. The method can be used to investigate structure foundations, highway cuts,

highway drainage, and aquifer delineation, and has applications in determining shear wave

velocity and the thickness of organics.

4.3.2.5.5 Seismic Reflection

Seismic reflection uses a surface seismic wave source to create seismic waves that can penetrate

the subsurface. The waves are reflected at interfaces that have either a change in shear wave

velocity and/or a change in density (termed impedance contrasts). At impedance contrasts, a

portion of the seismic wave is reflected back to the ground surface and a portion continues into

the subsurface, where it continues to the next impedance contrast. Seismic reflection techniques

can obtain information in excess of 100 feet.

4.3.2.5.6 Resistivity

Resistivity testing is used to find the depth to bedrock, applying the premise that soil and rock

typically have different electrical resistances. Resistivity is affected by the moisture content of

the soil and the presence or lack of metals, salts, and clay particles. Resistivity surveys can be

used to model ground water flow through the subsurface, and may also be used to determine the

potential for corrosion of foundation materials. Resistivity surveys can reach depths of 160 feet,

with the depth of the survey typically 1/3 of the electrode spacing (e.g., to reach a depth of 50

feet an electrode spacing of 150 feet is required).

4.3.2.6 Falling Weight Deflectometer

The Falling-Weight Deflectometer (FWD) is a trailer-mounted device that exerts a load on the

pavement and records the response of the pavement structure to this loading. The recorded data

is analyzed to determine the competency of the existing pavement structure and to determine

parameters, such as resilient modulus, to assist in pavement design and evaluation. The FWD

testing is performed by the NYSDOT Highway Data Services Bureau. Resilient modulus, Mr, is

discussed in NYSDOT GDM Chapter 7.

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4.3.2.7 Hydraulic Conductivity Testing Methods

In general design practice, hydraulic conductivity is estimated based on grain size characteristics

of the soil strata. In more critical applications, hydraulic conductivity can be better defined

through in-situ testing. In-situ test methods utilized to determine hydraulic conductivity include

the following:

• Percolation Test

• Well pumping tests

• Seepage Tests

• Packer permeability tests

• Other - Slug tests, Piezocone tests, Flood tests

A discussion of field measurement of permeability is presented in Sabatini, et al. (2002) and

Mayne, et al. (2002), and ASTM D 4043 presents a guide for the selection of various field

methods.

4.3.2.7.1 Percolation Test

Percolation is defined as the gravity flow of groundwater through the pore spaces in rock or soil.

A percolation test is typically used as a test to determine the suitability of a soil for the

installation of a domestic sewage-disposal system, in which a hole is dug and filled with water

and the rate of water-level decline is measured. The Department utilizes percolation data to

determine infiltration rates. To provide national consistency, the NRCS Soil Surveys evaluated

percolation rates of about 900 soils to define permeability classes (Uhland and O’Neal (1951)).

As the surveys evolved, the NRCS transitioned from permeability to the term saturated hydraulic

conductivity. The NRCS recommended that the term “saturated hydraulic conductivity” be used

for data expressed as a velocity and obtained by analysis using Darcy’s Law on saturated cores”.

The percolation test involves, as described in NAVFAC Design Manual DM-7.1 Soil Mechanics,

digging a hole (generally 2 ft. square), or drilled (4 in. min.) to a depth of the proposed

absorption trench, cleaned of loose debris, filled with coarse sand or fine gravel over the bottom

2 in., and saturated for a specified time. To eliminate any smearing during the excavation, the

sidewalls should be scratched or scarified to provide open, natural soil which water may

percolate. The percolation rate measurement is obtained by filling the hole to a prescribed level

(usually 6 in.) and then measuring the drop over a set time limit (usually 30 minutes). In sandy

soils, the time limit may be only 10 minutes.

Limitations: Attempt to conduct the percolation test in clement weather. If there is heavy rain,

snow, ice or freezing rain, the test should be re-scheduled. Typically, depending on the depth, the

absorption trenches are dug with a backhoe. The scheduling to obtain the equipment and hauling

to the site should be a consideration. The depth of the absorption trench needs to be evaluated to

determine it’s safe and practical based on site constraints. Typically, a limit on the depth of an

absorption trench is 5 ft. (4 ft. test pit with a 1 ft. infiltration test hole). As with all subsurface

explorations, the locations are to be identified and cleared as per 16 NYCRR Part 753 Protection

of Underground Facilities.

CHAPTER 4




4.3.2.7.2 Well Pumping Tests

Well pumping tests can be used to provide an estimate of the overall hydraulic conductivity of a

geologic formation, and since it is in essence a full scale test, directly accounts for the layering

and directionality of the hydraulic characteristics of the formation. The data provided can be

used to determine the requirements for construction dewatering systems for excavations or the

capacity of a well. The test method presented in ASTM D4050 applies. Pump tests can be

expensive and can take a significant amount of time to complete. Care must be exercised when

conducting this type of test if potentially contaminated zones could be mobilized during

pumping, adjacent facilities such as drinking wells could be impacted, or dewatering could result

in local ground subsidence.

4.3.2.7.3 Seepage Tests

Seepage tests can be used in soils with lower hydraulic conductivities than is generally

considered suitable for pumping tests and does not require disposal of large volumes of water.

Data from seepage tests only reflect the hydraulic conditions near the borehole. Tests can be

performed intermittently as the borehole is advanced.

Three types of seepage tests are commonly used: falling head, rising head and constant water

level methods. Typically either the rising or falling level methods should be used if the hydraulic

conductivity is low enough to permit accurate determination of the water level. In the falling

head method, the borehole or piezometer is filled with water that is allowed to seep into the soil.

The rate of drop of the water surface in the casing is monitored. The rising head method consists

of bailing the water out of the borehole and observing the rate of rise until the change becomes

negligible. The constant water level method is used if soil is too permeable to allow accurate

measurement of the rising or falling water level.

In general, the rising head test is preferred because there is less chance of clogging soil pores

with suspended sediment, although there is the danger of the soil at the bottom of the borehole

becoming loosened or “quick” if too great a gradient is imposed. General guidance on these

types of tests is provided in Mayne, et al. (2002).

4.3.2.7.4 Packer Permeability Tests

Packer permeability tests can be used to measure the hydraulic conductivity of a specific soil or

rock unit. The information obtained is used primarily in seepage studies. This test is conducted

by inserting the packer units to the desired test depth, which has been determined from cores and

geophysical logs of the borehole, after the cased boring has been properly cleaned out. The

packers are expanded to seal off the zone being tested, and water is injected into the borehole

under constant pressure. Measurements of the flow rate are taken at regular time intervals. Upon

completion of testing at a particular depth, the packers can be moved to a new test depth. See

Mayne, et al. (2002) for additional information on this type of test.

CHAPTER 4




4.3.2.7.5 Other Tests

• Slug Test - Short duration test that can be performed in a borehole in which a screened

pipe has been installed. The hydraulic conductivity can be estimated by monitoring the

rate of rise or fall of the water level in the borehole as a solid object is lowered into or

removed from the pipe. ASTM D 4044 describes the appropriate test method. Slug tests

are not very reliable and may underestimate hydraulic conductivity.

• Piezecone Test - Performed in conjunction with a Cone Penetrometer Test, the test

involves advancing a cylindrical rod with a conical point through the soil to the desired

depth, followed by recording pore pressures while the cone is held stationary. Details of

the equipment and methodology used to conduct the piezocone test are provided in

Sabatini, et al. (2002). Piezocone data can be useful to estimate the hydraulic

conductivity of silts and clays, but is subject to a large amount of uncertainty, and should

be used only as a preliminary estimate of permeability.

• Flood Test - Or pilot infiltration test, are applied mainly in the design of infiltration

facilities. Given that tests are performed in test pits approximately 100 ft2 (9 m

2) in size,

they are not always feasible. Generally only used where unusual site conditions that are

poorly modeled by correlation to soil gradation characteristics are encountered, and there

is plenty of water available to conduct the test.

4.4 PHASING OF SUBSURFACE INVESTIGATIONS

Subsurface investigations are typically conducted in two phases - preliminary and final. The

preliminary phase of subsurface investigation should be conducted early enough in the design

process to assist in the selection of foundation types and in the determination of bridge/structure

location and length. The preliminary phase should also consider scour, seismic site class, and

similar specific concerns, where appropriate. Where possible, the testing locations for the

preliminary phase should be readily accessible and within the current Department right-of-way

(ROW). The final phase of subsurface investigation supplements the preliminary, expanding on

information that was obtained, filling in gaps of information where none was obtained, and/or

adjusting to a modified project scope. The information collected during the final phase and any

additional laboratory analyses will be used to finalize foundation and earthwork

recommendations for the project.

CHAPTER 4




4.5 SUBSURFACE EXPLORATION CRITERIA

This section discusses the various applications of test borings within a subsurface exploration

program. It presents the minimum number of borings required, and the locations and anticipated

depths of the borings, for each of the applications.

The frequency and spacing of soil borings indicated in the following are the minimum

requirements. Engineering judgment should be applied to address anticipated or potential

variation in subsurface conditions and the type of facility to be designed. GPS coordinates

(latitude and longitude) and ground elevation must be established at all soil borings.

Test boring criteria is based on the use of the Standard Penetration Test (SPT) to obtain soil

samples. Unless directed otherwise, SPTs shall be conducted continuously in the upper 10 feet of

the subsurface and every 5 feet below that depth. If the Drill Crew encounters soft material

(sampler advances with little to no hammer blows) and the site/structure characteristics warrant,

undisturbed samples will be required. The term “blow(s)” used herein refers to hammer blows

recorded during an SPT.

CHAPTER 4




4.5.1 Bridge Foundations

All bridges shall have sufficient test borings taken at each proposed abutment and pier to meet

the minimum geotechnical site investigation indicated below:

Criteria for Test Boring Termination Number and Locations

of Test Borings

General

Continuous 40 ft. (12 m) of 40 blow material

or

Continuous 50 ft. (15 m) of 25 blow material

(blows resulting from Standard Penetration Test)

2 borings per substructure, located near the ends of the proposed substructure

One boring at each bridge should be driven casing

Where top of rock elevation or soil conditions are variable, additional borings may be warranted

The above criteria will apply unless Rock is encountered (see below)

Criteria begins below anticipated bottom of footing elevation, unless at a Water Crossing (see below)

Downstate Seismic Criteria: One boring at each bridge shall be drilled to a minimum 100 ft. (30 m) depth

Spread footing on Soil

Continuous sampling for top 15 ft. (4.5 m) below anticipated bottom of footing elevation

Water Crossing

Criteria begins a minimum of 25 ft. (7.5 m) below bottom of stream bed (to account for extreme scour event)

Rock

Minimum of 10 ft. (3 m) of NX rock core with at least 85% recovery

Minimum of 20 ft. (6 m) of NX rock core where rock socketed drilled shafts or micropiles might be used

Minimum of 10 ft. (3 m) of NX core below anticipated bottom of footing elevation where rock is encountered above anticipated bottom of footing

Minimum of 15 ft. (4.5 m) of NX rock core with at least 85% recovery in the last 5 ft (1.5 m) where boulders exceeding 5 ft. (1.5 m) are probable

Table 4-2 Bridge Foundations - Minimum Requirements

CHAPTER 4




4.5.2 Retaining Walls

All retaining walls shall have sufficient test borings taken along the proposed line of the wall to

meet the minimum geotechnical site investigation indicated below. Note that anchored walls

require additional borings in the anchored zone, as depicted in Figure 4-3.

Function Criteria for Test Boring Termination Number and Locations

of Test Borings

Gravity and Fill

Type walls

Same criteria as for

Bridge Foundations

Wall length less than 50

ft (15 m) Minimum of 1 boring

Wall length of 50-100 ft

(30 m)

1 boring at each end of the wall

Fle

xib

le W

all

s –

Te

mp

ora

ry o

r P

erm

an

en

t

(wall

s w

ith

em

be

dd

ed

ele

me

nts

)

General

3 times the proposed retained height below the anticipated bottom of excavation, unless Rock is encountered (see below)

Wall length greater than

100 ft, or

Rock

1 boring at each end of the wall

A boring at the point of maximum wall height

Additional borings between the ends of the wall, spaced at 50’-200’, depending on the characteristics of the site and structure, and the soil/rock conditions

Rock

Minimum of 10 ft. (3 m) of NX rock core with at least 85% recovery

Minimum of 20 ft. (6 m) of NX rock core where rock socketed soldier piles might be used

Minimum of 15 ft. (4.5 m) of NX rock core with at least 85% recovery in the last 5 ft. (1.5 m) where boulders exceeding 5 ft. (1.5 m) are probable

Anchored Walls

(additional borings in anchored zone)

2 times the proposed retained height below the anticipated bottom of excavation, unless Rock is encountered

If Rock is encountered, minimum of 10 ft. (3 m) of NX rock core with at least 85% recovery in the last 5 ft. (1.5 m)

Wall length less than 100

ft (30 m)

Minimum of 1 boring, located 1.5 times the retained height behind the proposed wall.

Wall length of 100 ft (30 m)

or more

Borings spaced at 100’-200’, located 1.5 times the retained height behind the proposed wall.

Table 4-3 Retaining Walls - Minimum Requirements

CHAPTER 4




See Walls and Slopes Requiring Additional Explorations in NYSDOT GDM Chapter 17.

For example, retaining walls which are known to require ground anchors for support require

further investigation. Figure 4-3 identifies testing locations to be performed to adequately

explore the subsurface conditions for the retaining wall and for the anchor design.

Figure 4-3 Site Explorations for Anchored Walls

CHAPTER 4




4.5.3 Embankments

All roadway embankments shall have sufficient test borings taken along the proposed line of the

embankment to meet the minimum geotechnical site investigation indicated below.


of Test Borings

General

2 times the maximum proposed fill height, unless Organic or Plastic soil is encountered, or if Rock is encountered

If Organic or Plastic (not till) soil is encountered, 10 ft. (3 m) below the Organic/Plastic deposit, or to 4 times the proposed fill height, whichever is shallower

If Rock is encountered, 5 ft. (1.5 m) of minimum AX rock core

Undisturbed sampling in soft plastic deposits

1 boring every 200’-500’ along the centerline or line of maximum fill height

1 boring every 200’-500’ at toe of existing embankment or beyond

In all areas where soft or unsuitable foundation soils may be encountered

Table 4-4 Embankments - Minimum Requirements

4.5.4 Large Cuts and Excavations

All large cuts and excavations shall have sufficient test borings taken along the proposed cut area

to meet the minimum geotechnical site investigation indicated below.


of Test Borings

General

10 ft. (3 m) below the anticipated bottom of excavation or 10 ft. (3 m) into rock, whichever is shallower

If Rock is encountered, minimum AX rock core

1 boring every 100’-300’ along proposed cut

area

Where top of rock elevation and/or soil conditions are variable, additional borings may be warranted

Test pits and probes may be utilized to obtain information between the borings

Table 4-5 Large Cuts and Excavations - Minimum Requirements

CHAPTER 4




4.5.5 Culverts

All culverts (pipe, box, floorless, etc) shall have sufficient test borings taken along the proposed

line of the culvert to meet the minimum geotechnical site investigation indicated below. Large

Culverts are culverts having an interior width greater than 5 feet, but no greater than 20 feet

(greater than 20 feet is considered a bridge). Small Culverts are culverts having an interior width

of 5 feet or less.

Criteria for Test Boring Termination Number and Location

of Test Borings

Large Culverts

Same criteria as for

bridge foundations

1 boring at each end of the culvert

Additional borings between the ends of the culvert, spaced at 100’-300’

For culvert extensions, 1 boring every 50’-100’ (minimum 1)

Small Culverts

10 ft. (3 m) below anticipated invert elevation

In soil, continuous sampling for top 10 ft. (3 m) below anticipated invert elevation

If Rock is encountered, minimum AX

rock core

1 boring every 100’-300’ along the line of the proposed culvert

For culvert extensions, 1 boring every 50’-100’ (minimum)

Table 4-6 Culverts - Minimum Requirements

CHAPTER 4




4.5.6 Noise Barrier Walls

All noise barrier walls shall have sufficient test borings taken along the proposed line of the wall

to meet the minimum geotechnical site investigation indicated below.


of Test Borings

General

40 ft. (12 m) below the anticipated top of foundation or 10 ft. (3 m) into rock, whichever is shallower, or 10 ft. (3 m) into rock (NX rock core), whichever is shallower

If Organic or Plastic (not Till) soil is encountered, 10 ft. (3 m) below the Organic/Peat deposit or 40 ft. (12 m) below the anticipated top of foundation, whichever is deeper

1 boring at each end of the noise barrier

Additional borings between the ends of the noise barrier, spaced at 100’-300’

Table 4-7 Noise Barrier Walls - Minimum Requirements

CHAPTER 4




4.5.7 Overhead Signs, Traffic Signals, and Light Standards

Overhead signs, traffic signals, and light standards are typically constructed on drilled shaft

foundations, with design sheets for overhead signs allowing for shallow footings. All overhead

signs, traffic signals, light standards, and similar structures shall have sufficient test borings

taken at each proposed foundation to meet the minimum geotechnical site investigation indicated

below.


of Test Borings

Overhead Signs

Continuous 30 ft . (9m) of 10 blow

material or 10 ft . (3 m) of rock (NX

rock core w ith at least 85% recovery),

whichever is shallower

Criteria begins below elevation of potential shallow foundation

Continuous sampling for top 10 ft. (3 m) below elevation of potential shallow foundation

1 boring at each foundation

Traffic Signals and Light Standards

30 ft. (9 m) below the anticipated top of foundation or 10 ft. (3 m) of rock (NX rock core), whichever is shallower

If Organic or Plastic (not Till) soil is encountered, 10 ft. (3 m) below the Organic/Peat deposit or 30 ft. (9 m) below the anticipated top of foundation, whichever is deeper

1 boring at each foundation

Table 4-8 Overhead Signs, Signals, and Light Standards - Minimum Requirements

CHAPTER 4




4.5.8 Pavement Structures

Subsurface investigation requirements for pavement structure design vary with location, traffic

level, and project size. At a minimum, the subsurface exploration program must determine the

composition of the pavement structure, the thickness of the subbase layer, and the character of

the subgrade/embankment material. All pavement structures shall have sufficient test borings

taken within the proposed area of pavement work to meet the minimum geotechnical site

investigation indicated below.


of Test Borings

General

Minimum 10 ft. (3 m) below top of pavement

Continuous sampling for top 5 ft. (1.5 m) or to bottom of former pavement layers, whichever is deeper.

Borings spaced at 100 ft. – 300 ft., depending on the characteristics of the proposed area of pavement work

Where conditions are diverse, additional pavement cores and borings at multiple locations may be warranted

Table 4-9 Pavement Structure - Minimum Requirements

4.5.9 Infiltration Basins and Wetland Mitigations

Subsurface investigation requirements for infiltration basins or wetland mitigations vary with

application, site conditions, and facility geometry. All infiltration basins and wetland mitigations

shall have sufficient test borings taken within the proposed area of the facility to meet the

minimum geotechnical site investigation indicated below.


of Test Borings

General

Continuous sampling for top 10 ft. (3 m) below anticipated bottom elevation or 10 ft. (3 m) into rock (minimum AX rock core), whichever is shallower

1 boring every acre within the proposed area of the facility

Additional borings in irregular shaped or separate areas that may be less than 1 acre

Additional borings, test pits, or percolation tests may be utilized to obtain information between the borings

Table 4-10 Infiltration Basins and Wetland Mitigations - Minimum Requirements

CHAPTER 4




4.5.10 Trenchless Pipe Installation

Subsurface investigation requirements for trenchless pipe installations must consider the

complexity of the installation, the size and depth of the jacking and receiving pits, the design of

dewatering system, and construction methods of the various installation techniques. All

trenchless pipe installations shall have sufficient test borings taken within the proposed area of

the pipe installation to meet the minimum geotechnical site investigation indicated below.


of Test Borings

General

15 ft (4.5 m) below anticipated pipe invert

If Rock is encountered, minimum 10 ft. (3 m) below anticipated pipe invert and minimum 5 ft. (1.5 m) of rock (minimum AX rock core)

1 boring every 50’-200’ within the proposed area of trenchless pipe installation

Where conditions are diverse, additional borings may be warranted

Jacking and

Receiving Pits

25 ft. (7.5 m) below anticipated pipe invert

If Rock is encountered, minimum 10 ft. (3 m) below anticipated pipe invert and minimum 5 ft. (1.5 m) of rock (minimum AX rock core)

1 boring at the anticipated pit

locations

Table 4-11 Trenchless Pipe Installation - Minimum Requirements

4.5.11 Other Applications

Various other applications for subsurface explorations will be encountered, including, but not

limited to, landslide mitigation, environmental contamination, groundwater monitoring,

structural integrity, etc. Every application and each site will be different. It will be the

responsibility of the geotechnical engineer to establish an exploration program that provides the

information needed for efficient design and construction. The experience of the engineer and the

requirements presented in this section can serve as guidelines in developing the program.

4.6 SUBSURFACE EXPLORATION AND SAMPLE TYPES

NYSDOT has a protocol for identifying each type of subsurface exploration (e.g., cased drill

holes, test pits, seismic points, etc.), and each individual soil sample and rock core. Presented in

this section is an outline of the procedure to be used in identifying the type of subsurface

exploration progressed, the design element for which the exploration was progressed, and the

type of sample obtained.. The type of exploration utilized is typically based on project specific

information and the site conditions.

CHAPTER 4




4.6.1 Identification System for Subsurface Explorations

Table 4-12 provides abbreviations and symbols that are to be used to identify all subsurface

explorations on all State projects:

Abbreviation Type of Exploration

DA 2½ in. (65 mm) Cased Hole

DN 4 in. (100 mm) Cased Hole

FH Hollow Flight Auger

DM Drilling Mud

PA Power Auger

AH Hand Auger

CP Cone Penetrometer

PH Probe

RP 1 in. (25 mm) Sampler (Retractable Plug)

TP Test Pit

PT Percolation Test Hole

SP Seismic Point

The abbreviation ‘PA’ is used for borings progressed with augers

having solid stem or single helix.

Table 4-12 Abbreviations for Various Types of Subsurface Explorations

If a drill hole is started by one drilling method and finished by another method, it should be

identified by the second method. Any changes of drilling method or casing size should be noted

on the driller’s field log.

The subsurface explorations in the DA, DN, FH, and DM category shall further be identified by

the abbreviations provided in Table 4-13.

CHAPTER 4




Abbreviation Design Element

B Bridge

C Cut

D Dam

F Fill

K Culvert

W Wall

X Miscellaneous

The abbreviation ‘X’ is used when none of the other

designations apply at the time the exploration is made.

Table 4-13 Abbreviations for Various Design Elements

Each exploration shall be numbered sequentially. However, if a planned exploration is not made,

a gap in consecutive numbers is permitted. If past explorations will be incorporated into the

project design, new explorations shall be numbered to avoid repeating the identifying numbers of

past explorations.

If a subsurface exploration is ended prior to reaching the required termination criteria, an

adjacent continuation exploration should be designated with a lower case letter, starting with “a”,

added to the number of the original exploration.

The name of the structure, the road crossing, the stream, river or creek shall be shown in the

space provided on the bottom of the log. For example:

• Mainline Southbound over Morris Road

• West Avenue over Penn Central

• Culvert at Roaring Brook

The following are examples of proper subsurface exploration identification:

DA-C-1 This is a 2½ in. (65 mm) diameter boring progressed for a cut.

DN-B-2 This is a 4 in. (100 mm) diameter boring progressed for a bridge.

DN-B-2a This is an adjacent continuation of boring DN-B-2.

4.6.2 Identification System for Individual Soil and Rock Samples

Each jar, tube, bag or other container shall be identified by the following:

• PIN

• Exploration Number

• Individual Sample Number

A typical sample number would be 3102.00-DA-B-1-J1. This number identifies the first jar

sample from a 2½ in. (65 mm) boring designated as DA-B-1 on project number 3102.00.

CHAPTER 4




The abbreviation “J” is used to identify samples placed in jars and “T” is used to identify tube

samples. The “J” and “T” refer to the container that the sample is in when it leaves the field. If a

tube is pressed and the soil sample is put into a jar, it would be a "J" sample.

Number all soil samples in each exploration consecutively, i.e., J1, J2, T3, J4, T5, etc. Number

all rock core runs in each exploration as a separate consecutive sequence, i.e., R1, R2, R3, etc.

Likewise number all boulder runs as a separate consecutive sequence, i.e., B1, B2, B3, etc., or

J1, J2, B1, J3, B2, J4, etc. (when boulders are embedded among soil samples).

4.7 FIELD EXPLORATIONS AND SAMPLING This section discusses items related to various methods of subsurface exploration, soil and rock

sampling, sample storage and transport, and in-situ field testing.

4.7.1 Soil and Rock Sampling in Test Borings

ASTM and AASHTO have procedures that must be followed for the collection of field samples.

All samples must be properly obtained, protected, and transported to a laboratory facility in

accordance with these procedures in order to preserve the samples in their original sampled

condition as best as possible. Methods used for collecting samples are described below.

4.7.1.1 Bulk Samples

Bulk samples are highly disturbed samples typically obtained from auger cuttings or test pits.

The quantity of the sample depends on the soil properties to be determined, but sample sizes can

range up to 50 lb (25 kg) or more. Typical laboratory testing performed on bulk samples include

natural moisture content, grain-size distribution, moisture-density relationship, and moisture-

plasticity relationship.

4.7.1.2 Split-Barrel Sampling

The most commonly used soil sampling method is the split-barrel, or split-spoon, sampler. The

samplers are typically 18” (450 mm) or 24” (600 mm) in length, and have a 2” (50 mm) OD and

a 1.5” (38 mm) or 1.375” (35 mm) ID. The sampler is driven into soil by means of hammer

blows. This method is used in conjunction with the Standard Penetration Test. This type of

sampling is adequate for moisture content, grain-size distribution, Atterberg Limits tests, and

visual identification.

Refer to ASTM D1586 - Standard Test Method for Penetration Test and Split-Barrel Sampling

of Soils (AASHTO T206 - Standard Method of Test for Penetration Test and Split-Barrel

Sampling of Soils).

CHAPTER 4




4.7.1.2.1 Progressing the Test Boring for Sampling

The hole for the test boring is progressed by one or combinations of the following methods:

• Advancing flush-joint casing by rotary drilling or by driving with a hammer

• Utilizing hollow flight augers to create a cased opening

• Opening a stable, uncased hole using a drilling mud process

Prior to sampling, the drill hole or casing is cleaned to the sampling elevation by using

equipment that will not disturb the material to be sampled. Bottom discharge bits, including

samplers, shall not be used for this operation. "N" size drill rods are typically used in casing

having an ID of 3” or larger.

When casing is advanced by driving, the blow count per foot should be recorded. Casing refusal

is considered as 300 blows for less than 12 in. of penetration. When refusal is encountered, the

casing is cleaned and coring then begins, unless otherwise directed by the Departmental

Geotechnical Engineer.

4.7.1.2.2 Obtaining a Sample

The sampler is placed on the bottom of the cleaned out hole, then driven the length of the

sampler using a 140 lb (625 N) hammer falling freely 30” (750 mm). The number of blows

required to drive the sampler each increment of 6” (150 mm) is recorded. The sum of the number

of blows required for the second and third 6” (150 mm) increments of penetration is termed the

"standard penetration resistance" or the "N-value".

Sampler refusal is 50 hammer blows for less than 6” of penetration. If refusal is encountered

before the desired sample length is attained, the sampler is removed from the hole and core

drilling started. When less than 6” of sample is retrieved in a split barrel sampler, the sampler

may be immediately re-driven in an attempt to obtain more material. Only the first set of blows

is recorded on the boring log, but a note is included under remarks indicating that a second

sampling attempt was made. A basket or other spring type retainer may be used on any or all

sampling attempts. When sampling material below the water table, the hole is kept full of fluid

during the removal of tools to prevent flow of soil into the casing.

After driving is completed, the sampler is retrieved and the soil sample is removed, then

packaged and identified as described in the following subsection.

Standard penetration tests and collection of samples is typically done at 5-foot intervals, although

continuous sampling in the upper 10-15 feet is common. Samples should also be taken at every

change in stratum. Specific sampling requirements may be directed by the Regional

Geotechnical Engineer.

CHAPTER 4




4.7.1.2.3 Packaging and Identification of Samples

Samples are placed in tied plastic storage bags and placed in jars in such a manner so as to

maintain the sampled condition of the soil. The side of the jar is labeled to show the project

name, PIN, hole number, sample number, the depth from which the sample was taken, and any

remarks that might pertain to that sample. Jars are placed in cartons clearly labeled to identify its

contents, specifically the project name, PIN, test boring numbers, enclosed jar sample numbers,

etc.

Samples must be protected from freezing or extreme heat. Refer to ASTM D4220 - Standard

Practices for Preserving and Transporting Soil.

4.7.1.3 Thin-Walled Tube Sampling

Thin-walled tube samples are taken to obtain undisturbed samples of fine grained soils

containing silt and clay, and of some organic materials. To obtain a sample, a thin-walled metal

tube, e.g., 3” dia. x 36” long (75 mm x 900 mm), is pressed into the soil at the sample depth. The

sampler is removed from the bore hole and immediately sealed, then taken to a laboratory

facility. It is extremely important that the samples be pressed, handled, and transported with a

minimum amount of disturbance. Careless handling of samples can cause misleading test results

that could result in inadequate designs.

This process allows the sample to be as undisturbed as possible and is suitable for fine-grained or

organic soils that require strength and consolidation tests. Refer to ASTM D1587 - Standard

Practice for Thin-Walled Tube Sampling of Soils for Geotechnical Purposes (AASHTO T207 -

Standard Method of Test for Thin-Walled Tube Sampling of Soils) and ASTM D6519 - Sampling

of Soil Using the Hydraulically Operated Stationary Piston Sampler.

4.7.1.3.1 Progressing the Test Boring for Sampling

The hole shall be a minimum of 4 inches in diameter. Drilling mud may be used if permitted by

the Departmental Geotechnical Engineer. Hollow stem augers are not allowed. The hole shall be

cleaned using methods and equipment which will not disturb the soil to be sampled. Bottom

discharge bits, including samplers, will not be allowed as hole cleanout tools.

The 2-1/2 inches of soil directly above the sampling elevation shall be removed with a cleanout

jet auger without the use of water. "N" size drill rods or larger shall be used.

4.7.1.3.2 Obtaining a Sample

At the elevation to be sampled, the tube is pressed into the soil with a continuous motion a

distance of 18 inches. Care is taken to allow air and water to flow freely through the vent, thus

preventing compression of the soil sample. After pressing the tube to the required depth and

waiting a minimum of 5 minutes, the sampler is carefully rotated and removed from the hole.

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Thin-walled tube samples are taken in the strata identified by the Departmental Geotechnical

Engineer. Samples are recovered with a stationary piston type sampler or a hydraulically

operated piston sampler, modified to accept the thin-walled tubes. Samplers with piston rods

extending to the ground surface must be provided with clamps which positively lock the piston

against upward travel while lowering the sampler to the sampling depth. During the press the

piston rods are locked in a stationary position to eliminate any movements either up or down. In

addition, the sampler is provided with positive locks to secure the piston rods prior to removal of

the sampler after penetration.

During the removal of the sampler, the hole is kept full of fluid. Before the thin-walled tube is

removed from the piston, the piston rod is backed off to admit air past the flattened threads to

break the vacuum. For other approved types of equipment, the necessary vacuum breaking

measures are taken. The length of sample in the tube and also the distance pressed is measured,

recorded, and indicated on the tube label.

If a thin-walled sample can not be retained or a tube cannot be pressed, a 2-inch diameter split

barrel sampler is driven to obtain a sample.

A wax seal (consisting of a combination of 3 parts paraffin and 5 parts bees wax, or a wax of the

same consistency as this mixture) is used to keep the sample from drying. The bottom of the

sample is carefully squared off at least 1 in. back from the end of the tube and a wax seal,

approximately 1 in. thick, is poured in the bottom end of the tube. The soil at the top of the tube

is carefully squared off and a wax seal, approximately 1/2 in. thick, is poured. It is desirable to

have a thinner wax seal at the top than the bottom for ease of extruding soil sample. Any space

remaining at the top or bottom of the sample tube is filled with sawdust or paper after the wax

has hardened. The ends of the tubes are sealed with snugly fitting plastic caps which are secured

in place with friction tape. Wax is not placed on the outside of the tube. Labels shall be placed on

the tube below center and secured with strips of tape.

Figure 4-4 Undisturbed Sample Schematic

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Geotechnical Engineering Manual GEM-8 Techniques to Improve Undisturbed Sampling was

created to evaluate the effects of sampling disturbance on plastic clays. Therein, by comparing

the results of good and bad sampling procedures it was concluded that two main causes of

unsatisfactory undisturbed samples are improper cleanout and inaccurate measurements. The

information in the manual is presented to assist the Departmental Geotechnical Engineer and

drilling personnel in obtaining the highest quality undisturbed sample

4.7.1.3.3 Packaging, Identification, and Transporting of Samples

Thin-walled tubes are labeled to show the project name, PIN, Location, hole number, sample

number, depths from which the sample was taken, amount pressed, amount recovered, and any

remarks that might pertain to that sample. The samples are handled, stored, and transported using

care to prevent the samples from being subjected to freezing, drying, jarring, and any other

disturbance. The tubes properly packaged are stored and transported in an upright position at all

times.

4.7.1.4 Rock Core Sampling

The most common method for progressing a test boring through rock is diamond core drilling.

As the core advances through the rock, a core sample of the rock can be collected in a core

barrel. There are three basic types of core barrels: single tube, double tube, and triple tube. Refer

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

Investigation (AASHTO T225 - Standard Method of Test for Diamond Core Drilling for Site

Investigation).

4.7.1.4.1 Obtaining a Rock Core

The hole is progressed through the overburden until refusal on the casing or soil sampler is

encountered. Unless directed otherwise, continuous core drilling should then be progressed in

boulders and ledge rock to depths determined by the Departmental Geotechnical Engineer.

Cores having a diameter of 1-1/6 in. to 2-1/6 in. (30 mm to 55 mm) are typically obtained using a

double tube, swivel type, core barrel capable of continuous coring lengths of 5 feet (1.5 m). If at

any time the core barrel is withdrawn by more than 1 inch (25 mm), the core barrel is removed

from the hole and the core removed from the barrel.

Rock core recoveries of less than 85% of each run are typically considered unacceptable and

coring shall continue for another 5 foot (1.5 m) run, unless in the judgment of the Departmental

Geotechnical Engineer, the necessary information has been obtained.

https://www.dot.ny.gov/divisions/engineering/technical-services/technical-services-repository/GEM-8b.pdf

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4.7.1.4.2 Packaging and Identification of Rock Cores

The rock core is placed in a wooden core box and secured to maintain it in its sampled condition.

Rock cores and the core box are labeled in accordance with the Geotechnical Engineering

Bureau drawing entitled "Instructions for Labeling Rock Cores". Where sections of the core

contain numerous small pieces, the pieces shall be bagged and placed back into their original

position within the core length. The bagged pieces shall be numbered as a “singular” piece

within the rock core.

4.7.2 Test Boring Logs All information obtained during the progression of a test boring is recorded in the field on a

Drillers Field Log (Fig 4-5). All information from the field log shall be included in a finalized

drill log (Fig 4-6). A log will be prepared for each boring. In addition to the information

identified for inclusion on the log, the following should also be noted, if encountered:

1. Groundwater - where it was encountered

2. Artesian - where it was encountered and the height of flow

3. Boulders, cobbles, and other obstructions - where they were encountered

4. Voids and/or gas pockets - where they were encountered

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Figure 4-5 Drillers Field Log

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Figure 4-6 Typical Boring Log

CHAPTER 4




4.8 REFERENCES

American Association of State and Highway Transportation Officials (AASHTO), Manual on

Subsurface Investigations, AASHTO MSI-1, January, 1988.

American Association of State and Highway Transportation Officials (AASHTO), T206,

Standard Method of Test for Penetration Test and Split-Barrel Sample of Soils, 444 North

Capitol Street N.W., Suite 249, Washington, D.C. 20001.


Standard Method of Test for Thin-Walled Tube Sampling of Soils, 444 North Capitol Street

N.W., Suite 249, Washington, D.C. 20001.


Standard Method of Test for Field Vane Shear Test in Cohesive Soil, 444 North Capitol Street

N.W., Suite 249, Washington, D.C. 20001.


Standard Method of Test for Diamond Core Drilling for Site Investigation, 444 North Capitol

Street N.W., Suite 249, Washington, D.C. 20001.


Standard Method of Test for Progressing Auger Borings for Geotechnical Explorations, 444

North Capitol Street N.W., Suite 249, Washington, D.C. 20001.

ASTM International, American Society for Testing and Materials (ASTM), D1586, Standard

Test Method for Penetration Test and Split-Barrel Sampling of Soils, 100 Barr Harbor Drive, PO

Box C700, West Conshohocken, PA 19428-2959


Practice for Thin-Walled Tube Sampling of Soils for Geotechnical Purposes, 100 Barr Harbor

Drive, PO Box C700, West Conshohocken, PA 19428-2959


Practice for Rock Core Drilling and Sampling of Rock for Site Investigation, 100 Barr Harbor

Drive, PO Box C700, West Conshohocken, PA 19428-2959


Test Method for Field Vane Shear Test in Cohesive Soil, 100 Barr Harbor Drive, PO Box C700,

West Conshohocken, PA 19428-2959


Guide for Selection of Aquifer Test Method in Determining Hydraulic Properties by Well

Techniques, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959


Test Method for (Field Procedure) for Instantaneous Change in Head (Slug) Tests for

CHAPTER 4




Determining Hydraulic Properties of Aquifers, 100 Barr Harbor Drive, PO Box C700, West

Conshohocken, PA 19428-2959


Test Method for (Field Procedure) for Withdrawal and Injection Well Tests for Determining

Hydraulic Properties of Aquifer Systems, 100 Barr Harbor Drive, PO Box C700, West



Practices for Preserving and Transporting Soil, 100 Barr Harbor Drive, PO Box C700, West



Test Method for Prebored Pressuremeter Testing in Soils, 100 Barr Harbor Drive, PO Box C700,



Test Method for Performing Electronic Friction Cone and Piezocone Penetration Testing of

Soils, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959


Practice for Using Hollow-Stem Augers for Geotechnical Exploration and Soil Sampling, 100

Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959


Test Method for Performing the Flat Plate Dilatometer, 100 Barr Harbor Drive, PO Box C700,



Test Method for Compressive Strength and Elastic Moduli of Intact Rock Core Specimens under

Varying States of Stress and Temperatures, 100 Barr Harbor Drive, PO Box C700, West


Das, M. Braja, Principles of Geotechnical Engineering, 3rd edition, PWS Publishing Company,

Boston MA, 1994.

Department of the Navy, Naval Facilities Engineering Command (NAVFAC), Soil Mechanics,

Design Manual 7.1, May, 1982.

Department of the Navy, Naval Facilities Engineering Command (NAVFAC), Foundations and

Earth Structures, Design Manual 7.2, May, 1982.

Department of the Navy, Naval Facilities Engineering Command (NAVFAC), Soil Dynamics,

Deep Stabilization, and Special Geotechnical Construction, Design Manual 7.3, April, 1983.

Geotechnical Engineering Bureau, Techniques to Improve Undisturbed Sampling, Geotechnical

Engineering Manual GEM-8, New York State Department of Transportation, Office of Technical

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Services,

https://www.dot.ny.gov/divisions/engineering/technical-services/technical-services-

repository/GEM-8b.pdf

Lunne, T., Robertson, P.K. and Powell, J.J.M., Cone Penetration Testing in Geotechnical

Practice. E & FN Spon, London, 1997.

Mayne, P. W., Christopher, B.R., and DeJong, J., 2002, Subsurface Investigations –

Geotechnical Site Characterization, Publication No. FHWA NHI-01-031, National Highway

Institute, Federal Highway Administration, Washington, DC, 300 pp.

Meyerhoff, G. G., Penetration Tests and Bearing Capacity of Cohesionless Soils, Journal of Soil

Mechanics and Foundation Division, American Society of Civil Engineers, Vol. 82, No. SM1,

Proc. Paper 866, pp. 1-19, January, 1956.

New York State Comprehensive Pavement Design Manual (CPDM), Department of

Transportation, Office of Technical Services,

https://www.dot.ny.gov/portal/page/portal/divisions/engineering/design/dqab/cpdm

Peck, R. B., Hanson, W. E. and Thornburn, T. H., 1974, Foundation Engineering, 2nd Edition,

John Wiley & Sons, New York.

Sabatini, P.J., Bachus, R.C., Mayne, P.W., Schneider, J.A., Zettler, T.E., Evaluation of Soil and

Rock Properties, Geotechnical Engineering Circular No. 5, FHWA-IF-02-034, April 2002.

Sowers, G.F., Introductory Soil Mechanics and Foundations: Geotechnical Engineering, 4th

edition, Macmillan Publishing Co., Inc., New York, NY, 1970.

Sowers, G.F. and Hedges, C.S, Dynamic Cone for Shallow In-Situ Penetration Testing, Vane

Shear and Cone Penetration Resistance Testing of In-Situ Soils, ASTM STP399, 1966

Spangler, M.G., and Handy, R.L., Soil Engineering, 4th edition, Harper & Row, Publishers, New

York, NY, 1982.

Wightman, W. E., Jalinoos, F., Sirles, P., and Hanna, K., Application of Geophysical Methods to

Highway Related Problems, Federal Highway Administration, Central Federal Lands Highway

Division, Lakewood, CO, Publication No. FHWA-IF-04-021, September 2003.



https://www.dot.ny.gov/portal/page/portal/divisions/engineering/design/dqab/cpdm

geotech field investigation

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