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SOIL MECHANICS Page 2-1 | Hubbell Power Systems, Inc. | All Rights Reserved | All Inc. 2-1 | | Page Systems, © 2014 Hubbell Power Copyright SOIL MECHANICS REVIEW OFSOILMECHANICS,BEHAVIOR,REVIEW &GEOTECHNICAL SITEINVESTIGATIONS K L.I. PI LL PL...... Plastic Limit PL...... Plastic t u s g n e SL g s c S g s S...... Degree ofSaturation S...... Degree V M g w φ SITE INVESTIGATIONS SOIL MECHANICS INTRODUCTION u ...... t . . t . ‘ s t d . f ...... n ...... ‘ ...... Page 2-2 | Hubbell Power Systems, Inc. | All Rights Reserved | CopyrightHubbell Power ©2014 Systems,Page | 2-2| Inc. |All Reserved Rights ...... Submerged Unit Weight (Submerged Density) ...... SYMBOLS USEDIN THIS SECTION Sa T orque MultiplierforHelical Piles/Anchors turated Unit Weight (Saturated Density) W et (Total) Unit Weight (Wet Density) SECTION 2 SECTION CONTENTS D ry Unit ry Weight Density) (Dry Undr ained ShearStrength Pore WaterPressure Moistur Shrinkage Limit Plasticity Index Plasticity Liquidity Index Liquidity Shear S Effective Stress S Friction Angle oil Sensitivity Liquid Limit Total Stress Void Ratio e Content Cohesion

Porosity Volume trength Mass

2-7 2-7 2-7 2-7 2-7 2-11 2-11 2-11 2-6 2-6 2-6 2-8 2-6 2-11 2-12 2-6 2-6 2-8 2-6 2-5 2-6 2-11 2-6 2-12

2-13 2-4 2-4 SOIL MECHANICS Civil ® 2-6 2-19 2-22 2-22 2-17 2-17 2-18 2-19 2-20 2-15 2-15 2-13 2-16 2-16 2-16 2-18 2-18

Shelby Tube Shelby w Stem Auger w Stem Field Vane Test Vane Field Vane Test Shear Vane Dilatometer Test Dilatometer Ground Water Table Water Ground Cone Test Cone Penetration ontinuous Flight Auger Flight ontinuous Overconsolidation Ratio Overconsolidation C Standard Test Standard Penetration Rock Quality Desigination Piezocone Test Piezocone Penetration Unconfined Compression Test UnconfinedCompression onfined Compressive Strength Compressive onfined DISCLAIMER Unified Soil Classification System Classification Unified Soil Unc Page 2-3 | Hubbell Power Systems, Inc. | All Rights Reserved | All Inc. 2-3 | | Page Systems, © 2014 Hubbell Power Copyright Field Blowcount Value from Standard Penetration Test Penetration Standard from Value Blowcount Field ...... T ...... T ...... SplitSpoon ...... MT u CFA CFA VST UC OCR N D FV RQD USCS HSA...... Hollo GW SPT SS ST CPT CPTU q Construction foundation support products. The information in this manual is provided as a guide to assist you with your design and in writing your own specifications. design and in writing your own specifications. as a guide to assist you with your information in this manual is provided The widely from location to location and from point to point on a site. vary including soil and structure conditions, Installation conditions, any to prior conducted be should authorities and codes building local and state consulting and analysis engineering Independent regulations and requirements. rules, installation to ascertain and verify compliance to relevant implementation, revision, or liable to you and/or your customers for the adoption, shall not be responsible for, Inc., Systems, Hubbell Power every confidence in its network of installing contractors and great pride and has takes Inc., Hubbell, use or misuse of this information. dealers. contractors in the installation of CHANCE the work of its dealers/installing warrant does NOT Inc., Systems, Hubbell Power SOIL MECHANICS distribution powerlines,signs,lightstandardsandcommercialbuildingssubjecttowindearthquakeload. moisture content,degreeofsaturation,density, andstresshistory. non-homogeneous, porous,earthenmaterialwhose engineeringbehaviorisinfluencedbychangesincomposition, disintegration ofrock,plustheair, water, organicmatter, andothersubstancesthatmaybeincluded.Soilistypically a Soil isdefinedassedimentsorotheraccumulationof mineralparticlesproducedbythephysicalorchemical DEFINITION ofSOIL design. of factoringagivensoil’s engineeringpropertiesfordesign.Thiscanleadtooverlyconservative foundation of varyingstrengthareaveraged,theresultcanbe misleading andmeaningless.Equallyisthepractice engineering propertiestoindividualsoillayersinorder forthedatatobemeaningful.Iffromseverallayers Deeper layerswillhavevaryingsuitabilitydependingontheirpropertiesandlocation.Itisimportant torelate from eachother. Topsoil isseldomusedforconstruction.Figure2-1shows atypicalgeneralizedsoilprofile. distinguished byacontrastincoloranddegreeofweathering.Thephysicalpropertieseachlayerusually differ plant andanimalresiduesmixedwithagivenmineral-basedsoil.Soillayersbelowthetopsoilcanusually be depths, andeachstratummayhavevariousthicknesses.Theupperlayeroftheprofileistypicallyrich inorganic The soilprofileisanaturalsuccessionofzonesorstratabelowthegroundsurface.Itmayextendto various profile. profound changesinthecharacterofsoiloverpassagetime.Theseprocessesbringabout thesoil rainfall, freeze/thawcycles,drought,erosion,leaching,andothernaturalprocessesresultingradual but about bytheclimateandotherfactorsprevalentatlocationofrockorsoilmaterial.Vegetation, Rock orsoilmaterial,derivedbygeologicprocesses,aresubjecttophysicalandchemicalchangesbrought THE SOILPROFILE and useofCHANCE background or review of soil mechanics so the engineer can develop a useful “working hypothesis” for the design gaps betweenworkinghypothesisandfact.TheintentofthissectiontheDesignManualistoprovide abasic Advance planningandcarefulobservationbytheengineerduringconstructionprocesscanhelp fillthe theory ofstructuresinotherbranchescivilengineering.” Nevertheless, fromapracticalpointofview, theworkinghypothesisfurnishedbysoilmechanicsisasuseful orientation oftheboundariesbetweenindividualstrataisalwaysincompleteandoftenutterlyinadequate. with aworkinghypothesis,becauseourknowledgeoftheaveragephysicalpropertiessubsoiland Terzaghi statedinhisbookTheoreticalSoilMechanics(1943):“..thetheoriesofsoilmechanicsprovideusonly SOIL MECHANICS use intheoveralldesignapproach.CHANCE investigation, itisnecessarytodefinethestructuralloadrequirementsandrequiredFactorofSafety(FS)for subsurface conditionofthefoundationsoilsatsiteaproposedproject.Inadditiontogeotechnical The useofmanufacturedsteelfoundationproductsgenerallyrequiresapriorgeotechnicalinvestigationthe INTRODUCTION • CHANCE structures andslabs. and slopestabilization;CHANCE • ATLAS RESISTANCE foundation products: Helical Tiebacks andaSOILSCREW ® HelicalPilesfornewconstructionandrepairofresidentialcommercialbuildings;CHANCE Page 2-4 | Hubbell Power Systems, Inc. | All Rights Reserved | CopyrightHubbell Power ©2014 Systems,Page | 2-4| Inc. |All Reserved Rights ® HelicalPilesandATLAS RESISTANCE ® piersforunderpinningandrepairofresidentialcommercialbuildings,retaining ® RetentionSystemusedinexcavationshoringsystems,retainingwalls ® HelicalAnchorsareutilizedforcommunicationtowers,transmission& ® CivilConstructionmanufacturesorsuppliestwomainlinesofsteel ® Piers. ®

SOIL MECHANICS The origin of soil can be broken down to two basic down to two of soil can be broken The origin is produced Residual soil and transported. types: residual of rock (decomposition) weathering by the in-place action. Residual soils may beby chemical or physical of intense weathering such as thevery thick in areas be thin or absent in areas of rapidtropics, or they may slopes. Residual soils are usuallyerosion such as steep are related to and their properties clayey or silty, factors prevalent at the location ofclimate and other are usually preferred to supportthe soil. Residual soils tend to have better and morefoundations, as they properties. predictable engineering are derived by the or deposited soils Transported to another locationmovement of soil from one location wind,by natural means. The means are generally The character of the resulting ice, and gravity. water, transportation anddeposit often reflects the modes of Deposits by waterdeposition and the source material. plains, and beaches.include alluvial floodplains, coastal and loess. DepositsDeposits by wind include sand dunes outwash. Each ofby melting ice include glacial till and dependentthese materials has behavioral characteristics name, such ason geological origin, and the geological Transported loess, conveys much useful information. – can be of poorsoils – particularly by wind or water quality in terms of engineering properties. solid particlesA soil mass is a porous material containing voids mayinterspersed with pores or voids. These or both. Figure 2-2 shows a water, be filled with air, volumes of air, conceptual block diagram of relative water, and soil solids in a given volume of soil. Pertinent and soil solids in a given volume of water, the left whilevolumes are indicated by symbols to are indicated byweights of these material volumes Page 2-5 | Hubbell Power Systems, Inc. | All Rights Reserved | All Inc. 2-5 | | Page Systems, © 2014 Hubbell Power Copyright Figure 2-1 Generalized Soil Profile Generalized ed to define the relative amounts of soil, air, and water of soil, air, provides several terms used to define the relative amounts symbols to the right. Figure 2-2 also termed the unit weight. Density mayin a soil mass. Density is the mass of a unit volume of soil. It is more correctly be expressed either as a wet density (including both soil and water) or as a dry density (soil only). Moisture content is the ratio of the weight of water to the weight of soil solids expressed at a percent. Porosity is the ratio of the amount of air or water contained in the voids.volume of voids to the total volume of the soil mass regardless of the ratio is the ratio of the volume of voids to the volume of solids. Void or consolidation. For a particular soilThe porosity and void ratio of a soil depend upon the degree of compaction be used to judge relative stability and load- conditions, the porosity and void ratio will vary and can in different and void ratio decrease. If water fills all thecarrying capacity – i.e., stability and load capacity increase as porosity voids in a soil mass, the soil is said to be saturated, i.e., S = 100%. Its value depends it to transmit water. Permeability or hydraulic conductivity is the property of soil that allows on the size, shape, and state of packing oflargely on the size and number of the void spaces, which in turn depends as a sand soil, but the clay will have a lowerthe soil grains. A clay soil can have the same void ratio and unit weight drains slowly frompermeability because of the much smaller pores or flow channels in the soil structure. Water fine-grained soils like clays. As the pore water drains, clays creep, or consolidate slowly over time. Sands have high As a result, sands will creep, or consolidate quickly when loaded thus pore water will drain quickly. permeability, until the water drains. After drainage, the creep reduces significantly. SOIL MECHANICS colloidal-size. colloidal-size. Well-graded soilsconsistofparticlesthatfallintoabroad rangeofsizesclass,i.e.,gravel,sand,silt-size,clay-size,and of soil.Forexample,thedarklineonFigure2-3represents a“Well-Graded” soil–withparticlesinawiderange. ordinate onthearithmeticscale.Theshapeofsuchcurves showsataglancethegeneralgradingcharacteristics Such curvesaredrawnonasemi-logarithmicscale,with thepercentagesfinerthangrainsizeshownas An effective waytopresentparticlesize data istousegrain-sizedistributioncurvessuchasshowninFigure2-3. proposed bytheUnifiedSoilClassificationSystem (USCS), whichhasgainedwiderecognition. classifications havebeenproposedbydifferent agencies. Table 2-1shows the categoryofvarioussoilparticlesas For convenienceinexpressingthesizecharacteristicsofvarioussoilfractions,anumberparticle-size tend tosticktogetherduemolecularattraction. 0.001 mm(colloidalsize).Fine-grainedsoilsaresometimesreferredtoascohesivesoils.Theparticlesof from 0.074to0.002mm.ClayparticlesarelessthanItisnotuncommonforclaybe lessthan small enoughtopassthroughthe#200sieve.Typical Fine-Grainedsoilsaresiltsandclays.Siltparticlestypicallyrange The second type of soil is fine-grained soil. Fine-Grained soils consist of soils in which 50% or more of the particles are referred toasapparentcohesion. except inthepresenceofmoisture,whosesurfacetensiontendstoholdparticlestogether. Thisiscommonly Soil PhasesandIndexSoil Properties, Figure 2-2 E ective (Submerged) Unit Weight Unit WeightSaturated TotalUnit Weight Unit Dry Weight Density) (Dry Porosity Void Ratio Degree ofSaturation Mositure Content V t V v V s V Page 2-6 | Hubbell Power Systems, Inc. | All Rights Reserved | CopyrightHubbell Power ©2014 Systems,Page | 2-6| Inc. |All Reserved Rights a V w Soil PhasesandIndexProperties W Υ Υ Υ Υ n (V e V S (V Water Solids Figure 2-2 d 1 s n t (W (W

W (W Air Υ v s

s w v - V / / V /

w s s V / + V + W

/ V / / W / Υ t t v s v w s ) x100 w ) x100 Υ ) x100 w ) / W ) w V V t t % % % W s W t typically do not stick together typically donotsticktogether The particlesofcohesionlesssoils to asgranularorcohesionlesssoils. grained soilsaresometimesreferred cobbles, gravels,andsands.Coarse- Coarse-grained soilsconsistof 200 openingsperinch. sieve (0.074mm).The#200has more particlesretainedbythe#200 are definedassoilthathave50%or grained soils.Coarse-grainedsoils particle size.Thefirsttypeiscoarse- basic soiltypesthataredefinedby and performance.Therearetwo which influencesoilproperties the soilmassareimportantfactors distribution ofsizesthroughout The sizesofsoilparticlesandthe particles iscalledthesoilstructure. of arrangementtheindividual the soilskeleton,andpattern the soilmassisoftenreferredtoas characteristics. Thissolidportionof composition, andsurface-chemical widely insize,shape,mineralogical solid mineralparticlesinsoilsvary non-homogeneous material.The As statedabove,soilistypicallya SOIL TYPES BASIC

SOIL MECHANICS ) of of n n Piers. ® Peas Sugar Baseball Rock Salt, FAMILIAR FAMILIAR Marbles & Table Salt, Table ) = 10. If the w REFERENCE t Helical Piles/Anchors, or ® –P.L.)/(L.L.-P.L). Liquidity Index is –P.L.)/(L.L.-P.L). n saturated clay is approximately the same as the L.L. (L.I. = 1.0), the soil is probably near normally consolidated. This typically results in an empirical torque multiplier for helical piles/ anchors (K If the moisture content (w a very useful parameter to evaluate the state of natural fine-grained soils and only requires measurement of the natural water content, the Liquid Limit and the Plastic Limit. Atterberg limits can be used as an approximate indicator of stress history of L.I. greater of a given soil. Values than or equal to one are indicative of very soft sensitive soils. In other words, the soil structure may be converted into a viscous fluid when disturbed or remolded by pile driving, caisson drilling, or the installation of CHANCE ATLAS RESISTANCE ATLAS saturated clay is greater than the L.L. 19 - 75 mm 2 - 4.76 mm 0.42 - 2 mm 75 - 300 mm 4.76 - 19 mm 0.074 - .042 mm 3”-12” 12” Plus 300 mm Plus Volleyball 0.75”- 3” 0.074 200 No. No. 4 - 0.75” No. 10 - No. 4 No. 40 - No. 10 Passing No. 200 0.074 mm Flour No. 200 - No. 40 Page 2-7 | Hubbell Power Systems, Inc. | All Rights Reserved | All Inc. 2-7 | | Page Systems, © 2014 Hubbell Power Copyright Figure 2-3 ------Fine Fine Grain Size, mm ( Log Scale ) mm ( Log Size, Grain Size Sieve 4.76 No. 4 Coarse Coarse Medium Typical Grain Size Distribution Curves Grain Typical Gravel Sand Silt or Clay Particle Size Distribution Size Particle 0 50 100 Sand

Well Graded Soil Graded Well Soil Graded Poorly Gravels Cobbles Boulders Percent Finer by Weight by Finer Percent PARTICLE SIZE TERM SIZE PARTICLE FRACTION SIEVE SIZE DIAMETER Fines (silts and clays) Gradation, Figure 2-3 Figure Gradation, Soil Particle Sizes, Table 2-1 Table Soil Particle Sizes, SOIL CONSISTENCY STATES and INDEX PROPERTIES SOIL CONSISTENCY STATES condition to a liquid form with successive addition of can range from a dry solid condition to a liquid form with successive The consistency of fine-grained soils solid to The consistency passes from pore space for acceptance of water. water and mixing as necessary to expand soil scientist, defined liquid as shown in Figure 2-4. In 1911, Atterberg, a Swedish semi-solid to plastic solid to viscous These limits are known as Atterberg dividing the various states of consistency. moisture contents representing limits semisolid from the plastic limit (PL) separates solid from semisolid behavior, Limits. The shrinkage limit (SL) separates liquid plastic from liquid state. Soils with water content above the and the liquid limit (LL) separates plastic behavior, limit behave as a viscous liquid. (PI). The PI is an in terms of moisture content, is defined as the plasticity index The width of the plastic state (LL-PL), in Figure 2-5, is a soil will exhibit. The Casagrande Plasticity Chart, shown important indicator of the plastic behavior soils can have. The softness of saturated fine-grained in plasticity that different a good indicator of the differences the liquidity index (L.I.) defined as L.I. = (w clay can be expressed numerically by SOIL MECHANICS Plasticity andAtterbergPlasticity LimitsFigure 2-4 Typical valuesofsoilsensitivityareshowninTable 2-2. soils includemarinedepositedinasaltwaterenvironment andsubsequentlysubjectedtoflushingbyfreshwater. are abbreviationsofcertainsoilcharacteristicsasshown inTable 2-3. shown inTable 2-4.Allsoilsareclassifiedinto15groups,eachgroupbeingdesignated bytwoletters.Theseletters utilizes resultsoflaboratorygrain-sizedataandAtterberg LimitsshowninTable 2-1.Thebasicsofthesystemare (USCS). TheUnifiedSystemincorporatesthetextural characteristicsofthesoilintoengineeringclassificationand The engineeringsoilclassificationcommonlyusedby GeotechnicalEngineersistheUnifiedSoilClassificationSystem ENGINEERING SOILCLASSIFICATION Aﬃnity for Water (Clays) Very Dry OI TT EIOI TT LSI TT LIQUIDSTATE STATE PLASTIC SEMISOLIDSTATE SOLID STATE Shrinkage Shrinkage Limit SL Page 2-8 | Hubbell Power Systems, Inc. | All Rights Reserved | CopyrightHubbell Power ©2014 Systems,Page | 2-8| Inc. |All Reserved Rights Plasticity and Atterberg Limits Increasing Moisture Content Figure 2-5 Figure 2-4 Plastic Limit PL Plasticity Index Plasticity Pl Liquid Limit LL Very Wet su as the undisturbed strength. Highly sensitive as theundisturbedstrength.Highlysensitive is, theremoldedstrengthisaboutsame through it.Somesoilsare“insensitive”,that Pier, drilledshaft,drivenpile,etc.haspassed CHANCE be countedonforshearstrengthaftera degree, buthighlysensitivesoilscannot to thatofthesoilinremoldedstateS of asaturatedsoilintheundisturbedstate the ratioofundrainedshearstrength as Sensitivity offinegrainedsoilsisdefined can betaken. swell pressuresothatpreventivemeasures potential expansionandtheor expansive clayarepredictingtheamountof problems withdesiccatedorpartlydry referred toasnegativeporepressure.The moisture evaporation.Thisissometimes equivalent internaltensionresultingfrom the w If thew viscous liquidandK (L.I. >1.0),thesoilisonvergeofbeinga and K (L.I. =0),thesoilisdryandoverconsolidated the soil. Desiccated clays are caused by an the soil.Desiccatedclaysarecausedbyan pressure requiredhasneverexistedin as overconsolidated,buttheoverburden behavior knownasdesiccation.Theybehave water tableoftenexhibitoverconsolidated Clays lyingatshallowdepthandabovethe glacial ice. geological erosion,ormeltingofoverriding the removalofoverburdenthrough today. Somecommoncausesaredesiccation, been loadedtoapressurehigherthanexists consolidated, orhaveahistoryofhaving Many naturalfine-grainedsoilsareover over consolidatedandKtwillbeabove10. (between thePLandLL),soilisprobably und /su n t typically ranges between 12 and 14. typicallyrangesbetween12and14. ofsaturatedclayisclosetotheP.L. n rem ® of a saturated clay is intermediate ofasaturatedclayisintermediate HelicalPile,ATLAS RESISTANCE . Most clays are sensitive to some . Mostclaysaresensitivetosome t will be less than 10. If willbelessthan10.If t ® =

SOIL MECHANICS

1-3 4-8 10-80 Sensitivity Organic 2nd Symbol Well Graded Well Poorly Graded Low Liquid Limit High Liquid Limit Insensitive Description Highly Sensitive Medium Sensitivity L P H O W Page 2-9 | Hubbell Power Systems, Inc. | All Rights Reserved | All Inc. 2-9 | | Page Systems, © 2014 Hubbell Power Copyright Sand Gravel Soil TYPE 1st Symbol Plastic Fines Marine Clays Plastic Clays & Silty Clays Plastic Clays & Silty Peat, Humus, Swamp Soils Non-plastic or Low Plasticity Fines Overconsolidated, Low to Medium Overconsolidated, Normally Consolidated, Medium Plastic Clays Normally Consolidated, S C G Pt M USCS Soil Group Symbol Characteristics, Table 2-3 Table Characteristics,USCS Soil Symbol Group by the USCS. ORGANIC SOILS (O & Pt) ORGANIC SOILS (O group Pt The clays. and silts organic including matter, organic of presence the by characterized are groups OH and OL construction characteristics. Peat, humus, andis highly organic soils that are very compressible and have undesirable swamp soils with a highly organic texture are typical. laboratory tests to determine the criticalClassification of a soil in the United Soil Classification System will require geologists, or engineers; but considerableproperties, but a tentative field classification is often made by drillers, skill and experience are required. Soil boring logs often include the engineering classification of soils as described FINE-GRAINED SOILS (M & C) arbitrary silty materials and micaceous or diatomaceous soils. An ML and MH groups include the predominately with low (L.L. < 50) where the liquid limit is 50. CL and CH groups comprise clays division between the two groups is clays. Low plasticity clays are classified as They are primarily inorganic and high (L.L. > 50) liquid limits, respectively. are classified as clays, or silty clays. Medium-plasticity and high plasticity clays CL and are usually lean clays, sandy CH. COARSE-GRAINED SOILS (G & S) SOILS (G COARSE-GRAINED passing fines non-plastic of 5% than less contain that soils sandy and gravely well-graded comprise groups SW and GW of non-plastic poorly graded gravels and sands containing less than 5% the #200 sieve. GP and SP groups comprise little or no include gravels or sands that contain more than 12% of fines having fines. GM and SM groups generally or low either exhibit which fines, of 12% than more with soils sandy or gravelly comprise groups SC and GC plasticity. high plasticity. Sensitivity of Soils, Table 2-2 Table Sensitivity of Soils, SOIL MECHANICS Specifics of the Unified Soil Classification System Soil (USCS), oftheUnified Specifics Table2-4 *Based onthematerialpassing3”(76mm)sieve. Highly OrganicSoils. 50% retainedon Soils- morethan Coarse Grained Soils -50%or Fine-Grained #200 sieve.* #200 sieve.* more passes Page 2-10 | Hubbell Power Systems, Inc. | All Rights Reserved | CopyrightHubbell Power ©2014 Systems,Page | 2-10| Inc. |All Reserved Rights on #4sieve. fraction retained more ofcoarse Gravels -50%or sieve. fraction passes#4 more ofcoarse Sands -50%or more Silts andClays-Liquidlimit50or than 50. Silts andClays-Liquidlimitless Major Divisions Clean Sands. Fines. Gravels with Clean Gravels Fines Sand with Symbols Group GW MSiltygravels.Gravel-sand-siltmixtures. GM MH SW OH SM ML GC CH GP OL PT SC CL SP mixtures. Littleornofines. Poorly gradedgravelsandgravel-sand mixtures. Littleornofines. Well-graded gravelsandgravel-sand mixtures. Clayey gravels.Gravel-sand-clay Clayey sands.Sand-claymixtures. Silty sands.Sand-siltmixtures. Little ornofines. Poorly gradedsandsandgravellysands. Little ornofines. Well-graded sandsandgravellysands. soils. Peat, muckandotherhighlyorganic plasticity. Organic claysofmediumtohigh clays. Inorganic claysofhighplasticity, fat silts. diatomaceous finesandsorsilts,elastic Inorganic silts,micaceousor low plasticity. Organic siltsandorganicsiltyclaysof silty clays,leanclays. plasticity, gravellyclays,sandy Inorganic claysoflowtomedium flour, siltyorclayeyfindsands. Inorganic silts,veryfinesands,rock Typical Descriptions SOIL MECHANICS Piers. The ® Equation 2-1 Helical Piles/Anchors, or ATLAS RESISTANCE Helical Piles/Anchors, or ATLAS ® Page 2-11 | Hubbell Power Systems, Inc. | All Rights Reserved | All Inc. 2-11 | | Page Systems, © 2014 Hubbell Power Copyright . The undrained shear strength is controlled by stress history, stress path, loading rate and verticaland rate loading path, stress history, stress by controlled is strength shear undrained The . u the effective stress in the soil stress the effective stress total (or applied) pore water pressure

= = =

s ‘

effective stress. effective where: ANGLE of INTERNAL FRICTION The shear strength of coarse-grained soils, such as sands, gravels and some silts, is closely analogous to the normal stress acting on a plane in the soilfrictional resistance of solids in contact. The relationship between the and its shearing strength can be expressed by the following equation, in terms of stress: Saturated fine-grained soils, such as clays and silty clays subjected to rapid loading have a low enough permeability enough low a have loading rapid to subjected clays silty and clays as such soils, fine-grained Saturated of these soils is controlled by The behavior that excess pore water pressures cannot dissipate during shear. component and not a “frictional”undrained shear strength. The strength is composed of only a “cohesive” (c), but a better term is simply undrainedcomponent. The strength of these soils, is sometimes called “cohesion” s strength, shear s, have sufficiently high permeability that and some mixed grain soils, have sufficiently high permeability Most unsaturated coarse-grained soils water pressures or any pore water pressures can dissipate during shear. applied loads do not generate pore soils very slowly and water is allowed to drain. The shear strength of these This is also true if the load is applied may component and a “frictional” component so that the shear strength generally consists of both a “cohesive” equation as shown in Equation 2-3. be reasonably described by the Mohr-Coulomb UNDRAINED SHEAR STRENGTH DRAINED SHEAR STRENGTH SOIL STRENGTH properties of soil is its shearing strength, or its ability to resist slidingOne of the most important engineering the bearing mass. Shear strength is the property that materially influences along internal surfaces within a given design of CHANCE capacity of a foundation soil and the s ’ = s - u s u EFFECTIVE STRESS and PORE WATER PRESSURE EFFECTIVEWATER PORE STRESS and of two components, a water table is equal to the sum a mass of soil at any point below The total stress within as the total force on stress is defined pressure. Effective stress and pore water a as effective which are known the area of the cross grain to grain of the soil, divided by soil mass which is transmitted from cross section of a stress. Pore to as inter-granular It sometimes is referred both solid particles and void spaces. section, including stress section. Effective the water in the soil pores in a cross defined as the unit stress carried by water pressure is and can be expressed as: governs soil behavior basic principle is similar in many respects to an object that resists sliding when resting on a table. basic principle is similar in many respects strength shear resistance that the materials are capable of developing. Shear The shear strength is the maximum part is part is the friction between particles (physical property). The second of soil consists of two parts. The first due to a chemical bond between particles. called cohesion, or no-load shear strength SOIL MECHANICS angle ofinternalfriction(φ proposed byCoulombin1773. The equation for shear strength as a linear function of total stress is called the Coulomb equation because it was first φ proportional tothenormalstress,justsameasslidingfrictionisstress.Insoil mechanics, over oneanotheragainstthenormalstress(s COULOMB EQUATION for SHEARSTRENGTH Cohesion isassociatedwithfinegrainmaterialssuch asclaysandsomesilts. soil particles.Itisafunctionofclaymineralogy, moisturecontent,particleorientation (soilstructure),anddensity. one overtheother, eventhoughnonormalstressisapplied.Cohesionthemolecularbondingorattractionbetween Cohesion is analogous to two sheets of flypaper with their sticky sides in contact. Considerable force is required to slide is calledthecohesion. stress for a pre-consolidated plastic clay as derived from a triaxial shear test. The intersection of the line at the ordinate shear strength is retained by the soil. Figure 2-6 is an example of the relationship between shear strength and normal words, the clays remember the pre-consolidation pressure they were previously subjected to. This means considerable is nolongeralineintersectingtheordinateatzero.Theclaysexhibitmemory, orcohesiveshearstrength.Inother history of consolidation (i.e., pre-consolidated) is measured, the relationship between shear strength and normal stress out ofthepores,shearstrengthincreaseswithnormalstress.Ifclayswhichhave aprevious When saturatedclayisconsolidated,thatis,whenthevolumeofvoidsdecreasesasaresultofwaterbeingsqueezed COHESION

is designated the angle of internal friction, because it represents the sum of sliding friction plus interlocking. The is designatedtheangleofinternalfriction,becauseitrepresentssumslidingfrictionplusinterlocking. The lower conﬁning stress cohesion

shear stress maximum verticle stressmaximum verticle maximum stress higher conﬁning stress Page 2-12 | Hubbell Power Systems, Inc. | All Rights Reserved | CopyrightHubbell Power ©2014 Systems,Page | 2-12| Inc. |All Reserved Rights Mohr’s Diagram forModerately PlasticSoil Portland Cement Association (1996) ) isafunctionofdensity, roundnessorangularity, andparticlesize. shear strength Figure 2-6 ). Therefore, the force required to overcome particle interlock is ). Therefore,theforcerequiredtoovercomeparticleinterlockis internal -ø friction angle of normal stress the individual grains must be lifted the individualgrainsmustbelifted irregular gears.Forslidingtooccur, much liketheteethoftwohighly individual soilgrainscaninterlock, contact areas.Indensesoils,the characteristics, suchasmultiple soil materialmustexhibitfriction requires anormalforce(s Shear strengthattributabletofriction the interlockingofsoilparticles. between individualsoilgrainsand mass isrelatedtotheslidingfriction The internalfrictionofagivensoil where: t = s tanφ

φ the failureplane s strength failure, ortheshear t

= = =

friction angle normal stressactingon the shearingstressat ), and the ), andthe Equation 2-2

shear strength at failure shear strength at cohesion on the failure plane total stress acting friction angle pore water pressure

fective stress: = = = = =

- u) tan φ’ f tan φ Helical Piles/Anchors, Tiebacks and SOIL SCREW 2-3 and 2-4 are two of the most widely used equations in geotechnical engineering, since they approximate- they since engineering, geotechnical in equations used widely most the of two are 2-4 and 2-3 s φ’ u t c’ ®

= c’ + (s = c + s f f • To locate the depth of a suitable bearing stratum for end bearing support of the underpinning pier. locate the depth of a suitable bearing stratum • To shaft pier the of stability column which in zones soil liquefiable potentially or weak any of location the establish To • must be considered. zones boulders, fill, rubble as such depth required the to pier the installing to barriers any are there if determine To • pre-drilling. or cavities within the soil mass, any of which might require of chert or other similar rock, voids of life performance the to related as soils foundation the of potential corrosion the of evaluation preliminary a do To • the steel pier. CHANCE SITE INVESTIGATIONS properties, limit states, engineering classifications, and soil strength this point, various definitions, identification To used to section details some of the more common soil exploration methods properties have been discussed. This determine these various soil parameters. the key soil site investigation is to identify the subsurface stratification, and The primary purpose of a geotechnical elements. Such studies are useful for the following reasons: properties for design of the steel foundation RESISTANCE ATLAS • To locate the depth and thickness of the soil stratum suitable for seating the helical plates of the pile and to locate the depth and thickness of the soil stratum suitable for seating the • To determine the necessary soil strength parameters of that stratum. liquefiable soils in which column establish the location of weak zones, such as peat type soils, or potentially • To stability of the pile for compression loading situations may require investigation. locate the depth of the groundwater table (GWT). • To depth such as fill, boulders or zones of determine if there are any barriers to installing the piles to the required • To cemented soils, or other conditions, which might require pre-drilling. of life performance the to related as soils foundation the of potential corrosion the of evaluation preliminary a do To • the steel pile. proposed the If project. the of magnitude the on depends reach should program exploration soil a investigation which to the extent in The more include to afford cannot designer the expenditure, small a only involves program construction than a small number of exploratory borings, test pits or helical trial probe piles and a few classification tests on conditions, must be compensated for by using arepresentative soil samples. The lack of information about subsoil conditions soil similar under out carried be to is operation construction large-scale a if However, safety. of factor liberal In terms of ef In terms where: t Equations bearing capacity Equations conditions. They are the basis for strength of any soil under drained ly describe the shear in Section 5.5-6 and 5-31 presented t SOIL MECHANICS stratum (generally“N”>15); add5footdepthforeachadditionalstory. • CommercialBuilding-For asinglestorystructureatleast20feetdeepwithfinal5 to 10feetintogoodbearing next section“Test BoringandSamplingProgram”foradescriptionofStandardPenetration Test and“N”values.) • ResidentialHome-Atleast15feetdeepwithfinal 5feetintogoodbearingstratum,generally“N”>810(See the projectstructure.Somegeneralguidelinesforuse inestimatingrequiredboringdepthsaregivenbelow: The depth of each boring will vary depending on the project type, magnitude of foundation loads and area extent of Depth ofTest Boring(s) building codes. • Or, boringnumbercanbebasedontheoverallprojectarea,or minimumrequirementsperapplicable provide informationregardingthedepthtobearingstrataandpilecapacity. • Iftheprojectissmallorwhenhasarestrictedbudget,helicaltrialprobepilesinstalledatsitecan • SheetPile/EarthStabilizationforEarthCuts-One(1)boringevery200to400feetofprojectlength. tower centerfoundationfooting. • CommunicationTowers -One(1)boringforeachlocationofaclusterpilesoranchors,andoneatthe 150 linealfeetoffoundationforothercommercialbuildings,warehousesandmanufacturingbuildings. • Commercial Building - One (1) boring for every 50 to 100 lineal feet for multistory-story structures, and every 100 to • ResidentialHome-One(1)boringforevery100to150linealfeetoffoundation. borings necessarytoestablishafoundationsoilprofileisgivenbelow: made ateachsitewherehelicalpilesorresistancepiersaretobeinstalled.Therecommendedminimum number of Whether theprojectinvolvesunderpinning/repairofanexistingstructureornewconstruction,boringsshouldbe Minimum NumberofTest Boring(s) type. for determiningthenumberofboringsanddepthtowhichboringshouldbetakenbasedon project marking ofallutilitiesinthezonewhichboringswillbeconducted.Indicatedbelowarerecommended guidelines of eachboringaswelldeterminingthefrequencysoilsamplingforlaboratorytestingandrequesting the landslide conditions.Theplanningportionincludesmakingapreliminarydeterminationofthenumberanddepth rock outcropsifpresent,placementofborings,evidencesoilfill,includingrubbleanddebris geologic conditionsintheproximityofsite,and(3)asitevisittoobservetopographydrainageconditions, of thestructureandwhetherprojectisnewconstructionorrepair, (2)areviewofthegeneralsoiland Reconnaissance andPlanningincludes:(1)reviewoftheproposedprojectstructuralloadrequirementssize the site.Themoreclearlysitegeologyisunderstood,efficientlysoilexplorationcanbeperformed. The firststepinanysubsoilexplorationprogramshouldbeaninvestigationofthegeneralgeologicalcharacter INITIAL RECONNAISSANCE andPLANNING given inthefollowingsections. and procedures,alongwiththerequiredsoilparametersusedindesigningmanufacturedsteelfoundationproducts,is and Sampling Program, (3) Laboratory Testing, and (4) a Geotechnical Report. A brief description of the requirements A geotechnicalsiteinvestigationgenerallyconsistsoffourphases:(1)ReconnaissanceandPlanning,(2)Test Boring soil, andwiththemethodsforanalyzingresultsoflaboratoryfieldtests. erroneous design assumptions. The designer must be familiar with the tools and processes available for exploring the by utilizing the results in design and construction, or compared to the expense that would arise from a failure due to the costofathoroughandelaboratesubsoilinvestigationisusuallysmallcomparedtosavingsthatcanberealized Page 2-14 | Hubbell Power Systems, Inc. | All Rights Reserved | CopyrightHubbell Power ©2014 Systems,Page | 2-14| Inc. |All Reserved Rights SOIL MECHANICS

character of the soil profile. • Communication Towers - Minimum of 35 feet - Minimum Towers • Communication feet and at least 20 over 100 feet tall for towers stratum (typically mediuminto a suitable bearing for to very stiff sands and stiff dense to dense for The suitable bearingclays) for helical anchors/piles. a minimum “N” value of 12stratum should have of 10 for cohesive soils. for sands and a minimum Stabilization - Boring should• Sheet Piling/Earth that is at least as deep as thebe taken to a depth retaining wall, etc.) to bestructure (sheet pile, a suitable stratum is reached foranchored or until plates of the tiebacks (generallyseating the helical clays). medium or denser sand or stiff local codes. • Active Seismic Areas - Depth per of the site are recommended minimums. Otherof the site are recommended minimums. and thesteps depend on the size of the project TEST BORING and SAMPLING PROGRAM andIn some cases, especially for small projects beshallow conditions, test borings may portableconducted using hand augers or other the site equipment. In most cases, however, usinginvestigation will typically require drilling a truck mounted drill rig. is toThe second step of the site investigation pits thatmake exploratory boreholes or test regardingfurnish more specific information of thethe general character and thickness anindividual soil strata. This step and characterinvestigation of the general geological Page 2-15 | Hubbell Power Systems, Inc. | All Rights Reserved | All Inc. 2-15 | | Page Systems, © 2014 Hubbell Power Copyright Figure 2-7 equency of Sampling Auger Drilling Operation Method of Boring and Fr eDrilling is typically the most economical and most expedient procedure for making borings although test pits can b using truck or track mounted drill rigsan alternative for some projects. Three common types of borings obtained auger drilling and 3) hollow stem flight are 1) wash borings (mud rotary), and 2) solid-stem continuous flight (CFA) auger drilling is the most common – particularly auger (HSA) drilling. Any one of the three can be used, but CFA to hold the borehole open and a drilling borings or mud rotary drilling use casings for shallow borings. Wash fluid to bring solid cuttings to the surface. The casing is either driven with a hammer or rotated mechanically while inside the casing and are rotated manuallythe hole is being advanced. The cutting bit and drill rods are inserted its type and condition and record The cuttings allow the driller to visually classify the soil as to or mechanically. typically use water or drilling mud such as borings the data on a log sheet at the depth of the cutting bit. Wash bentonite slurry depending on the soil. In some soil profiles, drilling mud prevents caving, making full-length casing of the mixture of soil and water/ While drilling proceeds, the driller observes the color and appearance unnecessary. soil profile. At 5 ft (1.5 m) intervals, or when mud. This enables the driller to establish the vertical sequence of the a is taken.change in strata is noticed, the cutting bit is removed and a spoon sample Auger drilling typically uses a continuous solid-stem flight auger rotated mechanically while the hole is being the often includes a hollow stem, which acts as a casing to hold advanced. The continuous flight auger (CFA) are carried to the surface by the auger flights, or drilling mud is typically not used. Cuttings borehole open. Water SOIL MECHANICS Tubes (ST). Standard Penetration Test (SPT). Undisturbed samples are typically obtained with thin-walled push tubes called Shelby samples mayeitherbeobtainedfromaugersaspreviously discussedormorecommonlytheyareobtainedusingthe types ofsoilsamplesthatareoftencollected;1)disturbed samples,and2)undisturbedsamples.Ingeneral,disturbed laboratory testingforsoilclassificationand testingforsoilstrengthandstiffness. Therearetwobroad Geotechnical Site Investigations almost always include the collection of soil samples for identification and description, Sampling Soil stabilize thewallsofholemayprecludeobtaining thisinformation. of theholeandafterallowingtostandovernight orfor24hoursbeforebackfilling.Theuseofdrillingmudto and recorded, if circumstances permit, during exploratory drilling. It is customary to note the water level on completion design andconstructionofdeepfoundations–especially ingranularsoils.Carefulobservationsshouldalwaysbemade equal tothatoftheatmosphere.Informationregardinglocationgroundwatertableisveryimportant tothe The groundwatertable(GWT),orphreaticsurfaceisdefinedastheelevationatwhichthepressureinwater (HSA). loose siltsbelowthewatertable.TheseconditionsrequireeitherwashboringoruseofHollowStem Augers stiff toverystiff fine-grainedsoilsthatmaintainanopenborehole,butdonot work inverysoftclaysorsandsand must beremovedandasamplingtoolplacedinthebottomofborehole.ContinuousFlightAugerswork wellin Disturbed samplesofsoilmaybetakenfromtheaugers,butinordertoobtainundisturbedsamples, augers in 5footsections.Theboreholeisadvancedbyrotatingtheauger, whichbringssoilcuttingstothegroundsurface. Solid-stem continuousflightaugersconsistofasolidsteelcentralshaftwithauger, typicallyavailable sizes. inch. Hollow-stemaugersaredesignatedbytheinsidediameterofpipe.3-1/4inchand4-1/4common 6 stem augersaredesignatedbytheoutsidediameterofaugerflights.Commonsizes3inch,4and undisturbed soilsamplestypicallyat5ft(1.5m)intervals.Figure2-7demonstratesanaugerdrillingoperation.Solid- The augeractsasatemporarycasing.Samplersareinsertedinsidethecasingtoretrievedisturbed and rod tobeinserteddownthroughtheaugerwithoutremovingsectionseachtimeasampleris inserted. which allowvisualclassificationofthesoil.Theadvantagehollowstemaugeristopermitsampler and Drill Stem Auger Stem Hollow Page 2-16 | Hubbell Power Systems, Inc. | All Rights Reserved | CopyrightHubbell Power ©2014 Systems,Page | 2-16| Inc. |All Reserved Rights Figure 2-8 Increment Marks 6” (150mm) Drop Hammer SOIL MECHANICS Split Barrel Tube Recovered soil sample Open Shoe Helical Piles and ATLAS ATLAS and Piles Helical ® Piers. Values of soil friction Piers. Values ® esistance R tlas Split Spoon Sample The 1½ in (38 mm) inside diameter split barrel may be used 1½ in (38 mm) The end penetrating The split liner. thickness with a 16-gauge wall Metal or plastic of the drive shoe may be slightly rounded. retainers may be used to retain soil samples. Piers. The SPT values also can assist in determining the depth of ® ” and cohesion “c” can be selected through correlation with the Page 2-17 | Hubbell Power Systems, Inc. | All Rights Reserved | All Inc. 2-17 | | Page Systems, © 2014 Hubbell Power Copyright installation requirements for A spoon reaches the bottom, the number of blows of the hammer is counted tospoon reaches the bottom, the number of blows of the hammer is counted forachieve three successive penetrations of 6” (0.15 m). The number of blows the first 6” is disregarded because of the disturbance that exists at the bottom of the drill hole. The number of blows for the second and third 6” increments orare added and designated the standard penetration test (SPT), “N” value, on soilblow count. The data obtained from SPT tests are commonly recorded SPTboring logs relative to the sounding depth where the sample was taken. designvalues are widely used to correlate the shearing strength of soil for the of shallow and deep foundations – including CHANCE angle “φ SPT “N” values. Details of the equipment and standardized procedures areSPT “N” values. Details of the equipment and standardized procedures RESISTANCE CPT/CPTU Figure 2-10 A = 1.0 to 2.0 in (25 to 50 mm) B = 18.0 to 30.0 in (0.457 to 0.762 m) C = 1.375 ± 0.005 in (34.93 ± 0.13 mm) D = 1.50 + 0.05 - 0.00 in (38.1 + 1.3 = 0.0 mm) E = 0.10 ± 0.02 in (2.54 ± 0.25 mm) F = 2.00 + 0.05 - 0.00 in (50.8 + 1.3 - 0.0 mm) G = 16.0º to 23.0º Geometry of Standard Penetration Test Geometry of Standard Penetration Split-Barrel Sampler (ASTM D 1586) Figure 2-9

relative density or the stiffness of in-situ relative density or the stiffness The most common method of obtaining some information concerning to drive the sampling spoon a specifiedsoil consists of counting the number of blows of a drop weight required standard penetration test (SPT). Thedistance into the ground. This dynamic sounding procedure is called the through a height of 30” (0.76 m) onto anessential features include a drop hammer weighing 140 lb (63.5 kg) falling anvil at the top of the drill rods, and a split spoon (SS) sampler having an external diameter of 2” (50.8 mm) and a to the bottom of the drill hole. After thelength of 30” (0.76 m). The spoon is attached to the drill rods and lowered Standard Penetration Test and Sampling Test Standard Penetration conception of the engineering to furnish a satisfactory exploratory drill holes are inadequate The cuttings from obtain soil samples strata. To and depths of the various soils encountered, or even the thickness characteristics of the of the hole. The spoon is drill rod and lowered to the bottom a sampling spoon is attached to the from test borings, opened up and the recovery from the hole. The spoon is to obtain a sample and is then removed driven into the soil spoon and inspected and described soil is extracted from the inside the spoon) is recorded. The (soil sample length and laboratoryjar and sealed for later visual inspection of the sample is placed in a glass A portion by the driller. index properties. determination of SOIL MECHANICS to givetheconetipresistance,q the tipthatiscalledsleeve.Theforceonandsleevearemeasuredindependentlyduringpenetration diameter of1.405inch,whichgivesaprojectedendarea10cm with aconetiphavinganapexangleof60°thatispushedslowlyintotheground.Thestandardsizehas and CPTUareshowninFigure2-10. the “effective” orcorrectedconetipresistancesinceitisforporewaterpressure. AfigureofaCPT cone advances.Thisiscalledapiezocone.Thetipresistanceobtainedfrompiezoconedefined as q Some conesarealsoequippedwithaporewaterpressuresensortomeasuretheexcessas in soillayeringatasiteandtoestimateindividualproperties,suchasshearstrengthstresshistory. Figure 2-12

Nitrogen Figure 2-11 walled ShelbyTube samplesarespecifiedinASTMD1587. the equipmentandproperproceduresforobtainingthin- classification anddeterminingindexproperties.Detailsof taken fromcuttingsortestpitsandareusefulforsoil sample. Handsamplesorgrabaresometimes vertically downintothesoiltoobtainanundisturbed tube isattachedtotheendofdrillrodandpushed commonly referredtoasa“Shelbytube”.TheShelby give aslightinsideclearance.Thistypeofsampleris The lowerendsarebeveledtoacuttingedge samplers madeofsteeltubingabout1.5mmthick. satisfactory samplescanbeobtainedin50and76mm samples mustbereducedtoaminimum.Reasonably laboratory analysis,thedegreeofdisturbance split spoonisverythick.Forsoilsamplestobeusedfor reasons: 1)thesamplerisdrivenintosoil,and2) are alwaysconsidereddisturbedtosomedegreefortwo In general,soilsamplestakenfromsplitspoonsamplers Undisturbed Samples sampler isshowninFigure2-9. conducting aStandardPenetrationTest. Thesplitspoon specified inASTMD1586.Figure2-8illustratesadrillcrew The ConePenetrationTest consistsofacylindricalprobe Cone PenetrationTest (CPT)/Piezocone(CPTU) METHODS IN-SITU TESTING s . These values may then be used to evaluate changes . Thesevaluesmaythenbeusedtoevaluatechanges 2 . Most cones also have a short section behind . Mostconesalsohaveashortsectionbehind soil beinginvestigated. definitive informationaboutthetypeof and samplingareusuallyneededfor use ofconepenetrometers,borings Since nosamplesareobtainedby encountered bythepenetrometer. can becorrelatedwiththetypeofsoil resistance dividedasthetip friction ratio,definedasthe up to60mormoreinsoftsoils.The but theyhavebeenusedtodepths more thanafewmetersindensesand, Cone penetrometerscannotpenetrate t ,

SOIL MECHANICS

0 . P 1 ) 2 and P 0 20 - 50 TENSILE (kg/cm STRENGTH ) 2 50 - 500 (kg/cm STRENGTH 300 - 3,500 50 - 250 800 - 2,500 - 250 150 200 - 1,700 40 - 250 1,800 - 3,000 150 - 300 COMPRESSIVE 1 - 5 5 - 20 5 - 25 0.5 - 2 1,000 - 2,500 70 - 200 10 - 30 100 - 1,000 20 - 100 0.1 - 0.5 1,000 - 2,000 70 - 200 0.5 - 1.5 500 - 2,000 50 - 200 0.1 - .05 1,500 - 3,000 100 - 300 0.1 - 1.0 1,500 - 3,000 100 - 300 0.1 - 0.2 1,000 - 3,000 150 - 300 0.1 - 0.5 2,000 - 3,500 150 - 350 0.5 - 1.5 1,000 - 2,500 70 - 250 (percent) POROSITY ) 3 2.65 (g/cm 2.6 - 2.7 2.6 - 2.7 2.9 - 3.0 2.0 - 2.4 2.2 - 2.6 2.5 - 2.6 2.8 - 2.9 2.0 - 2.6 3.0 - 3.1 2.6 - 2.7 Page 2-19 | Hubbell Power Systems, Inc. | All Rights Reserved | All Inc. 2-19 | | Page Systems, © 2014 Hubbell Power Copyright 3.0 - 3.05 BULK DENSITY ) 2 kg/cm 2 - 5 1 - 8 1 - 2 2 - 6 3 - 8 6 - 8 6 - 10 8 - 11 7 - 11 7 - 10 5 4 - 8.4 1 - 3.5 0.5 - 8 (10 AT ZERO LOAD AT YOUNG’S MODULUS YOUNG’S Coal Slate Shale are then used along with the soil effective stress at each test depth to obtain estimates of specific soil properties each test depth to obtain estimates stress at with the soil effective are then used along ROCK Basalt Gneiss Diorite Marble Syenite 1 Gabbro Granite Dolerite Dolomite Quartzite Mudstone Limestone Sandstone Microgranite Notes: 0.25 ratio is approximately listed above, Poisson’s 1) For the igneous rocks 1968) Modulus (after Farmer, in Young’s in density and increase with an increase normally increases type, the strength 2) For a certain rock Nostrand Reinhold, page 72 Engineering Handbook, Winterkom and Fong, Van Foundation from 3) Taken such as shear strength, modulus, stress history and in-situ lateral stress. The specific requirements of the test are given are test the of requirements specific The stress. lateral in-situ and history stress modulus, strength, shear as such in ASTM D6635. (FVT) Test Field Vane shear strength and Sensitivity (VST) is used to measure the undrained Shear Test (FVT) or Vane Test The Field Vane direct in-situ fine-grained soils. It is considered one of the most reliable and to very soft saturated of medium stiff determine shear strength and the only in-situ test that may be used to test methods for determining undrained the soil and rotating slowly to create a shear vane into The test consists of inserting a thin four-bladed Sensitivity. shown in Figure 2-13. rectangular with a height to diameter ratio (H/D) of 2, as failure in the soil. The vane is usually obtain the peak or undisturbed undrained shear strength. Then, the the maximum torque is measured to Initially, of is repeated to obtain the remolded undrained shear strength. The ratio vane is rotated 10 times and the test the as previously described. The specific requirements of is defined as Sensitivity, undisturbed to remolded strength test are given in ASTM D2573. and P Mechanical Properties of Various Rocks, Table 2-5 Table Rocks, Mechanical PropertiesVarious of Dilatometer Test (DMT) Test Dilatometer The Dilatometer consists Test of a flat stainless steelblade with aflexible circular, membrane mounted on one side of the blade, as shown on Figure 2-11. The blade is pushed into the ground, much like of a providing CPT or continuous CPTU, but data, instead pushing is stopped every 1 foot. Immediately membrane is after expanded into pushing the soil is using nitrogen stopped, gas and the a control flexibleconsole at the ground surface. pressureTwo readings are taken; 1) the A-Reading, which is the pressure required to just initiate movement of the membrane into the soil, and 2) the B-Reading, which is the pressure required to expand the center of the membrane 1 mm into the soil. The two Readings are corrected for the stiffness of the membrane to give two pressure readings, P SOIL MECHANICS ground condition, the ATLAS RESISTANCE s is strength shear undrained determined from: the 2 = H/D with vane a for and rotation during measured is (T) torque maximum The also usedtodeterminethetotal(wet)unitweightand thedryunitweight. dried weightissubtractedfromtheoriginalto determinethewaterweightofsample.Thesemethodsare time toallowallthemoistureevaporate.Afterbeing removedfromtheoven,soilsampleisweighedagain.The soil sampletakenfromthefieldonalaboratoryscale. Thesoilsampleisthenplacedinastandardovenforsufficient • conduct thefollowingtests: composition (See Table 2-4). In addition to this visual classification, a representative number of samples are selected to and color,quantity,odor recovery,soil and strength, percent conditions, type approximate depth, moisture inclusion sample fromthefieldboringandsamplingprogramis inspectedvisuallyandgivenavisualdescriptionastoitscollection Classification–Samplescollectedduringthedrillingoperationsshouldbevisuallyclassified.Everyrecovered Visual • Classification /Characterization Tests project upon depending scope in vary may and investigation requirements orvariabilityinsoilconditions.Someofthemoretypicallaboratorytestsaredescribedbelow: subsurface a of part typically is testing Laboratory TestingLaboratory ofRecovered Samples Soil RQD = commonly usedmeasureofrockqualityandisdefinedas: and measured to determine the rock competency (soundness or quality). The rock quality designation In (RQD) addition is to the conducting most compressive tests on the recovered rock core samples (See Table 2-5), the rock core is examined to thedepthorlengthspecified. Typical rockanchorsmaybeseated20ft.or30intotheformation. When bedrock is encountered, and rock anchors are a design consideration, a continuous rock core must be recovered Rock CoringandQualityofMeasurement torque valuescanbeusedtoinfershearstrengthbasedonthetorque-to-capacityrelationshipdiscussedinSection6. Shear strengthalsocanbeestimatedbyinstallingahelicalpile“probe”andlogginginstallationtorquevs.depth.The Helical Probe Report sothattheengineermaymakeanyadjustmentstotestresultsforequipmentused. Geotechnical a in described be used procedures test and blades) of thickness D, H, (e.g., vane the of geometry exact strength reduction that the soil may experience during installation, depending on the Sensitivity. It evaluating sitesforhelicalpiles/anchorsasitmaygivesomeinsighttotheengineerintodegreeofdisturbanceand is important that the Vanes areavailableisdifferent sizestosuitthesoilataparticularsite.TheFieldVane Test maybeespeciallyusefulin The presence of an intact bedrock surface represents the ideal ground condition for ATLAS RESISTANCE can oftenbeadvancediftheRQDis0.30orless. upper bedrock surfaces comprised of weathered bedrock material such as weathered shale Helical piles/anchorsrotatedortorquedintothegroundcannotbeinstalledhard,competentbedrock. However, or in sandstone, the helix plates The valuesofRQDrangebetween0and1.0wherean0.90orhigherisconsideredexcellentqualityrock. Lengthofcorerun u Water Content–measurestheamountofmoistureinsoil.Moisture orwatercontentismeasuredbyweighinga =(0.273T)/D Σ Lengthofintactpiecescore(>100mm) 3

Page 2-20 | Hubbell Power Systems, Inc. | All Rights Reserved | CopyrightHubbell Power ©2014 Systems,Page | 2-20| Inc. |All Reserved Rights ® Pierisinstalledtotherigidbearingsurfacerepresentedbybedrocklayer. ® Equation 2-5 Piers. In this Piers.Inthis SOIL MECHANICS Page 2-21 | Hubbell Power Systems, Inc. | All Rights Reserved | All Inc. 2-21 | | Page Systems, © 2014 Hubbell Power Copyright Sample Boring Log in Coarse-Grained Soil, Table 2-6 Sample in Coarse-Grained Log Boring Table Soil, SOIL MECHANICS is asoilboringtakeninfine-grainedclaysoil. An example boring log is shown in Table 2-6 & 2-7. Table 2-6 is a soil strength (cohesion), groundwater table location, type of drilling used, type of SPT hammer used, and sample recovery.boring taken in a coarse-grained sand soil. shear Table undrained or 2-7 strength compression unconfined limits, Atterberg content, moisture TestN-values, Penetration on asoilboringare:totaldepth,profile,descriptionofsamples,samplenumberandtype, Standard they contain basically the same type of information – most of which has been discussed in this section. Items to expect Helical Piles and ATLAS RESISTANCE unconfined compression test is used to determinethe unconfined compression strength“q “c” ofthesoil.Forcohesive(clay)soilsamples,anunconfinedcompressiontest“U “φ angle friction the directly determine to tests shear direct or triaxial in either tested are samples In someinstancesundisturbedsoilsamplesarerecoveredinthefieldusingathinwallShelbytube.These STRENGTH CHARACTERISTICS content todeterminetheLiquidityIndex. water natural the with along used be may they since important particularly are Limit Plastic the and Limit Liquid The / Characterization Classification 4318 Tests. D ASTM in followed closely are The procedures and specifications equipment, tests. these performing for procedures and apparatus developed specially (LL, using properties determined Index are expansion. PI) for and SL, potential PL, and soil the of stiffness relative the of measure a is and soil of types AtterbergLimits – • Liquid Limit (LL), Plastic Limit (PL), Shrinkage Limit (SL), and Plastic Index (PI) – applies to cohesive • ParticleSizeAnalysis–measuresthedistributionofparticlesizeswithinsoilsample. includes soilboringlogs.Soillogsprovideawealthofinformationthatisusefulinthedesign of CHANCE as seismic parameters and corrosion potential, foundation options, allowable load capacities, and an appendix which history includinggeology, subsurfaceconditions,soilprofile,groundwaterlocation,potentialdesignconstraintssuch site performed, work of scope the detailing introduction an include usually reports Geotechnical testing. laboratory The geotechnicalreportprovidesasummaryofthefindingssubsurfaceinvestigation,and results ofthe THE GEOTECHNICALREPORT for totalandeffective stresspathsatprojectspecificconfiningstresses. Triaxialtests (UU) Undrained Unconsolidated and (CU) Undrained Consolidated (CD), Drained Consolidated include, by justifying higher soil strength than using less sophisticated test methods. Some of the more complex strength tests samples. Morerefinedlaboratorytestingmaybeappropriateforlargeprojectsandoffer acostsavingpotential relatively inexpensive test to determine the soil friction angle and may also be used for undrained testing of cohesive a with noconfiningpressurewhichmaynotbeappropriatefortheproject.Forgranularsoils,DirectSheartestis commonly is test compression unconfined The “qu”. of one-half performed duetoitslowcost;howevertheresultstendbeconservativeandsimulateonlytotalstressconditions be to taken then is sample clay the of cohesion Page 2-22 | Hubbell Power Systems, Inc. | All Rights Reserved | CopyrightHubbell Power ©2014 Systems,Page | 2-22| Inc. |All Reserved Rights ® Piers. Boring logs come in variety of designs since there is no standard form, but Piers.Boringlogscomeinvarietyofdesignssincethereisnostandardform,but c ” is often conducted. The ” isoftenconducted.The u ” of the clay soil. The ” of the clay soil. The ” and the cohesion ” andthecohesion ® SOIL MECHANICS Page 2-23 | Hubbell Power Systems, Inc. | All Rights Reserved | All Inc. 2-23 | | Page Systems, © 2014 Hubbell Power Copyright Sample Boring Log in Fine-grained Soil, Table 2-7 SampleTable in Fine-grained Log Boring Soil, SOIL MECHANICS suction test,swellpotential)thatcanbeconductedbut shouldbepracticedbytheinformeddesigner. has significantvolumechangepotentialandshould be investigatedfurther. There arefairlysimpletests(Atterberg,soil A PlasticityIndex(PI)greaterthan25to30isaredflag tothegeotechnicalengineer. API≥ structure fromcontactwiththeexpansivesoil,thereby eliminatingthedestructiveeffects ofswellpressures. void form is a typical detail used in areas like Denver, Colorado, subjected toswellpressuresandjackingforces.Isolating footings,slabs,andgradebeamsfromsubgradesoilsbyusing where expansive soil is present. The void form isolates the Helical Piles are a good choice in expansive soils due to their relatively small shaft size – which results in less surface area existence and be prepared to install CHANCE undetected pocketsandhencepresentapotentialproblem.Thebestsolutionistobeawareofthepossibilitytheir on largeprojectslikeanundergroundpipelineortransmissionlinethatcoversmanymiles,thesesoilsmayoccurin the project.Thisisusuallydeterminedduringsubsurfaceinvestigationbymeansofdrillingorsounding.However, of start the before known typically are site project given a on soils collapsible and organic fills, deep of existence The Deep Fill,OrganicandCollapsibleSoils dealing withthevariabilityofsoils. inevitable problemsthatarise.ItiswisetorememberDr. Terzaghi’s emphasistohaveasecondarysolutionreadywhen All naturalmaterials,suchassoil,willexhibitconditions of variability that maymakeasinglesolution inadequate for ConditionsProblem Soil the soilandsideoffoundationcanbesufficient magnitudeto“jack”afoundationoutoftheground.CHANCE expansive soil via skin friction within the active zone. As an expansive soil swells or heaves, the adhesion force between The tensilestrengthofdeepfoundationsmustbesufficienttoresistthehighforcesappliedfoundation by is typicallydifficulttocontrol. from changing.Theoretically, ifthemoisturecontentdoesnotchange,volumeofclaysoilwillchange.This seasonal by affected is that soil expansive moisture of depth variation. the Another as method defined is used zone to active design The foundations “doming.” or on dishing” expansive “slab soil is to prevent the soil’s moisture content below the expansive soil’s active zone, or be designed to withstand the forces applied the foundation, e.g., to prevent routinely in expansive soil with no allowance for the potential expansion. Foundations should be designed clay to may penetrate far exceed the adfreeze forces generated by seasonally frozen ground, potential yet depending foundations continue on change volume to exhibit moisture soils clay be Most content, founded type. soil common mineralogy, a is clay that fact and the hence – particles soil clay finally and structure. silt, The upward forces (swell pressure) of expansive shrink-swell behavior since they can also shrink if dried out. The high having as described natural often are soils These region. in-place every earth’snearly the in over surface, all exist weathering soils Expansive of rock produces sand, then Expansive Soils loaded dynamically. ThesedepositsaretypicallyindentifiedwithLiquidityIndexgreaterthanabout1.2. Some marineclaydepositsarealsoverysensitiveandcanlosemostoftheirshearstrengthwhendisturbed andwhen Sensitive Clays less (typically than about6)andshouldbeviewedwithcaution. N-values SPT low very by identified typically are soils These loading. dynamic other or earthquake an Some depositsofsaturatedsandandsiltyarenaturallyloosemaybepronetolosestrengthorliquefyduring Loose LiquefiableSoils RESISTANCE this material into better bearing soil. It is not recommended to locate the helical bearing plates or the tip of the ATLAS ® Pierinthesesoils. Page 2-24 | Hubbell Power Systems, Inc. | All Rights Reserved | CopyrightHubbell Power ©2014 Systems,Page | 2-24| Inc. |All Reserved Rights ® Helical Piles and ATLAS RESISTANCE ® Piers deeper to penetrate through Piersdeepertopenetratethrough 25 to 30 indicates the soil 25to30indicatesthesoil ®

SOIL MECHANICS

® Page 2-25 | Hubbell Power Systems, Inc. | All Rights Reserved | All Inc. 2-25 | | Page Systems, © 2014 Hubbell Power Copyright Piers are installed. ® Bowles, Joseph E., Foundation Analysis and Design, Fourth Edition, McGraw Hill, 1988. Bowles, Joseph E., Foundation Analysis Second the of Proceedings Soil, Expansive in Piers Concrete and Helical of Investigation Field (1998), A. Thomas Chapel, 1998) Beijing, China. Soils (UNSAT International Conference on Unsaturated 1969. Second Edition, Ronald Press Co., NY, Hough, B.K., Basic Soils Engineering, 1992. Soil Primer, Portland Cement Association, PCA 1982. Row Publishers, NY, Soil Engineering, Fourth Edition, Harper and Merlin G. and R.L. Handy, Spangler, 1943. Wiley and Sons, NY, Karl., Theoretical Soil Mechanics, John Terzaghi, Karl, R.B. Peck and G. Mesri, Soil Mechanics in Engineering Practice, Third Edition, John Wiley and Terzaghi, Sons, NY, 1996. for Fulfillment Partial in Thesis Soil, Fine-Grained Sensitive a in Piles Helical of Testing Load and Installation N., C. Weech, B.C., 2002. Columbia, Vancouver, Masters Degree, University of British Helical Piles or ATLAS RESISTANCE Helical Piles or ATLAS References A subcategory of this condition is seasonal permafrost. If possible, these ice lenses should be penetrated and not reliednot and penetrated be should lenses ice these possible, If permafrost. seasonal is condition this of subcategory A on for end bearing. Seasonally Frozen Ground Frozen Seasonally growth of frost illustrated by the silt) as soils (typically, frost susceptible category is the obvious soil in this The most frost as known phenomenon expansion observed commonly a to leads This weather. freezing in lenses ice and needles heave. Frost heave is typically observed on roadbeds, under concrete slabs, and along freshly exposed cuts. Capillary problem, before CHANCE drainage will do much to control this barriers in conjunction with proper breaks and vapor