1INTRODUCTION TO STATIC ANALYSIS Reference Manual Chapter 9Lesson 2 Learning OutcomesYou will be able to: List 3 reasons why a static analysis is performed. Discuss what makes a good static analysis method. Calculate effective overburden pressure versus depth.CHAPTER 9 - STATIC ANALYSIS Single pile design issues Group design issues Special design considerations Additional design and construction considerationsSTATIC ANALYSIS METHODS Calculate pile length for loads Determine number of piles Determine most cost effective pile type Calculate foundation settlement Calculate performance under uplift and lateral loadsStatic analysis methods and computer solutions are used to:STATIC ANALYSIS METHODSStatic analysis methods and computer solutions are an integral part of the design process.Static analysis methods are necessary to determine the most cost effective pile type.- calculate capacity - determine pile length- determine number of pilesBid QuantityFor a given pile type: STATIC ANALYSIS METHODSDesigner should fully know the basis for, limitations of, and applicability of a chosen method.Foundation designer must know design loads and performance requirements.Many static analysis methods are available.- methods in manual are relatively simple- methods provide reasonableagreement with full scale tests - other more sophisticated methods could be used2BASICS OF STATIC ANALYSISStatic capacity is the sum of the soil/rock resistances along the pile shaft and at the pile toe.Static analyses are performed to determine ultimate pile capacity and the pile group response to applied loads.The ultimate capacity of a pile and pile group is the smaller of the soil rock medium to support the pile loads or the structural capacity of the piles.BASICS OF STATIC ANALYSISStatic analysis calculations of deformation response to lateral loads and pile group settlement are compared to the performance criteria established for the structure.Static analyses are performed using geotechnical evaluation of soil properties from laboratory test, standard penetration test results, or in-situ test data.On many projects, multiple static analyses are required.ULTIMATE CAPACITYQu = (Design Load x FS) + otherOther could be the resistance provided by scourable soilOther could be the resistance provided by Liquefiable soilOther is soil resistance at the time of driving not present later during the design life of the pileTWO STATIC ANALYSIS ARE OFTEN REQUIREDSecond analysis with scourable soilin place and with pile length from firstanalysis, this will give us our ultimatestatic resistance at time of drivingLiquefaction ?First analysis with scourable soilremoved, this will give us requiredpile length for the given ultimate capacity.TWO STATIC ANALYSIS REQUIREDCOHESIONLESS SOILSbs3 5b3 5.5b 3 5.5bb = pile diameters = settlement3COHESIVE SOILSH=heavehigh pore water pressure zoneb3bHLOAD TRANSFERThe ultimate pile capacity is typically expressed as the sum of the shaft and toe resistances:Qu= Rs+ RtThis may also be expressed in terms of unit resistances:Qu= fs As+ qt AtThe above equations assume that the ultimate shaft and toe resistances are simultaneously developed.LOADTRANSFERRtAxialLoad vs DepthRtRsQuRsSoil Resistance vs DepthRs = 0UniformTriangularRs RtRtEFFECTIVE OVERBURDEN PRESSUREThe effective overburden pressure at a given depth is the vertical stress at that depth due to the weight of the overlying soils.A plot of the effective overburden pressure versus depth is called a podiagram and is used in many static analysis methods.EFFECTIVE OVERBURDEN PRESSUREThe total overburden pressure at a given depth is obtained from summing the product of the total unit weight times the layer thickness versus depth.pt= (depth)The pore water pressure is summed versus depth by multplying the unit weight of water times the water heightu = w(depth)EFFECTIVE OVERBURDEN PRESSUREThe effective overburden pressure at a given depth is the total pressure minus the pore water pressure.po= pt- u4EFFECTIVE OVERBURDEN PRESSURE158.1(614 lb/ft2) (2683 lb/ft2)275.7 187.5EFFECTIVE OVERBURDEN PRESSURE185.1302.7(2456 lb/ft2) (1406 lb/ft2)67.5126.3(2736 lb/ft2)176.4STUDENT EXERCISE #1Figure 9.7 on page 12 shows the effect of water table location on effective stresses.Low water table results in higher effective stresses, higher shear strength, and therefore higher driving resistances SoilProfileDepth(m)Layer Thicknesst (m)Unit Weight of Soil Layer(kN/m3)OverburdenPressurefrom Layer,t ()(kPa)TotalOverburdenPressure at Depthpt= t ()(kPa)Unit Weightof Waterw(kN/m3)Pore WaterPressurefrom Layert w(kPa)Total PoreWaterPressure at Depthu=G t (w)(kPa)EffectiveOverburdenPressurepo=pt-u(kPa)0 0 15.0 0 0 - - - 0 0 05 5 15.0 75 75 - - - 0 0 7510 5 15.0 75 150 9.8 49 49 10120 10 17.5 175 325 9.8 98 147 17835 15 20.0 300 625 9.8 147 294 331STUDENT EXERCISE #15DESIGN SOIL STRENGTH PARAMETERSMost of the static analysis methods in cohesionless soils use the soil friction angle determined from laboratory tests or SPT N values.In coarse granular deposits, the soil friction angle should be chosen conservatively.What does this mean ??DESIGN SOIL STRENGTH PARAMETERSIn soft, rounded gravel deposits, use a maximum soil friction angle, , of 32 for shaft resistance calculations.In hard, angular gravel deposits, use a maximum friction angle of 36 for shaft resistance calculations.DESIGN SOIL STRENGTH PARAMETERSIn cohesive soils, accurate assessments of the soil shear strength and consolidation properties are needed for static analysis.The sensitivity of cohesive soils should be known during the design stage so that informed assessments of pile driveability and soil setup conservatively can be made.DESIGN SOIL STRENGTH PARAMETERSFor a cost effective design with any static analysis method, the foundation designer must consider time dependent soil strength changes.6FACTOR OF SAFETY SELECTIONHistorically, the range in factor of safety has depended upon the reliability of a particular static analysis method with consideration of : Level of confidence in the input parameters Variabilityof soil and rock Method of static analysis Effects of, and consistency of proposed pile installationmethod Level of construction monitoringFACTORS OF SAFETYConstruction Control Method Factor of SafetyStatic load test with wave equation analysis 2.00Dynamic testing with wave equation analysis 2.25Indicator piles with wave equation analysis 2.50Wave equation analysis 2.75Gates dynamic formula 3.50The factor of safety used in a static analysis should be based on the construction control method specified.9-14EXAMPLE SOIL PROFILEUltimate Capacity:Qu= Rs1+ Rs2+ Rs3+RtDesign Load:Qa= (Rs3+ Rt) / FSSoil Resistance to Driving:SRD = Rs1+ Rs2+ Rs3+RtEXAMPLE SOIL PROFILESRD = Rs1+ Rs2/ 2 + Rs3+Rt(with clay soil strength change)(with no soil strength changes)Lesson 2 Learning OutcomesYou will be able to: List 3 reasons why a static analysis is performed. Discuss what makes a good static analysis method. Calculate effective overburden pressure versus depth.Static Analysis- Single PilesMethods for estimating static resistance of soils7Lesson 7 Learning OutcomesYou will be able to: Identify the FHWA recommended static analysis methods in cohesionless and cohesive soils. Calculate, by hand, the axial compression capacity of a single pile in cohesionless, cohesive, and layered soils.Lesson 7 Learning OutcomesYou will be able to: Determine when the axial compression capacity is controlled by the structural pile capacity. Discuss the DRIVEN software for axial compression capacity calculations.STATICCAPACITY OFPILESIN COHESIONLESSSOILSPushing ForceResistanceNormal Force, NFriction Force, FF = N = coefficient of friction between material 1 and material 2FNTan () = F/NF = N TAN ()phi = angle such that TAN ()is coefficient of friction between material 1 and material 212Soil on Soil, we use Soil on Pile, we use Cohesionless Soils, Drained StrengthMETHODS OF STATIC ANALYSISFOR PILES IN COHESIONLESS SOILSMethod Approach DesignParametersAdvantages Disadvantages RemarksMeyerhof Method Empirical Results of SPT tests.Widespread use of SPT test and input data availability. Simple method to use.Non reproducibilityof N values.Not as reliable as the other methods presented in this chapter.Due to non reproducibilityof N values and simplifying assumptions, use should be limited to preliminary estimating purposes.Brown MethodEmpirical Results of SPT tests based of N60values.Widespread use of SPT test and input data availability. Simple method to use.N60values not always available.Simple method based on correlations with 71 static load test results.Details provided in Section 9.7.1.1b.Nordlund Method.Semi-empiricalCharts provided by Nordlund.Estimate of soil friction angle is needed.Allowsfor increased shaft resistance of tapered piles and includeseffects of pile-soilfriction coefficient for different pile materials.No limitingvalue on unit shaft resistance is recommended by Nordlund.Soil friction angle often estimated from SPT data.Good approach to design that is widelyused. Method is based on field observations.Details provided in Section 9.7.1.1c.FHWA9-19Part Theory Part ExperienceExperience N8METHODS OF STATIC ANALYSISFOR PILES IN COHESIONLESS SOILSMethod Approach DesignParametersAdvantages Disadvantages RemarksEffective Stress Method.Semi-empiricalSoil classification and estimated friction angle for and Ntselection. value considers pile-soilfriction coefficient for different pile materials.Soil resistance related to effective overburden pressure.Results effected by range in values and in particular by range in Ntchosen. Good approach for design.Details provided in Section 9.7.1.3.Methods based on Cone Penetration Test (CPT) data.Empirical Results of CPT tests.Testing analogy between CPT and pile.Reliable correlations and reproducible test data.Limitations on pushingcone into dense strata.Good approach for design.Details provided in Section 9.7.1.7.9-19Nordlund Data BasePile TypesPile SizesPile LoadsTimber, H-piles, Closed-end Pipe, Monotube, Raymond Step-TaperPile widths of 250 500 mm(10 - 20 in)Ultimate pile capacities of 350 -2700 kN (40 -300 tons)Nordlund Method tends to overpredict capacity of piles greater than 600 mm (24 in)9-25Nordlund Method1. The friction angle of the soil.9-252. The friction angle of the sliding surface.3. The taper of the pile.4. The effective unit weight of the soil.5. The pile length.6. The minimum pile perimeter.7. The volume of soil displaced.Considers:9-27For a pile of uniform cross section (=0) andembedded length D, driven in soil layers ofthe same effective unit weight and frictionangle, the Nordlund equation becomes:Nordlund MethodRS RTQu = (KCFpd(sin)CdD) + (tNqAtpt)Nordlund Shaft ResistanceK= coefficient of lateral earth pressureCF= correction factor for Kwhen pd= effective overburden pressure at center of layer = friction angle between pile and soilCd= pile perimeterD= embedded pile lengthFigures 9.11 - 9.14Figure 9.15Figure 9.109Nordlund Toe ResistanceT= dimensionless factorNq= bearing capacity factorAT= pile toe areapT= effective overburden pressure at pile toe 150 kPaqL= limiting unit toe resistanceFigure 9.16aFigure 9.16bFigure 9.17RT= qLATRT= TNqpTAT Lesser ofNordlund MethodRu=RS+ RT Qa=RU/ FSand FS based on construction control method as in 9-14Nordlund Method ProcedureSteps 1 through 6 are for computing shaft resistance and steps 7 through 9 are for computing the pile toe resistanceSTEP 1Delineate the soil profile into layers and determine the angle for each layera. Construct podiagram using procedure described in Section 9.4.b. Correct SPT field N values for overburden pressure using Figure 4.4 from Chapter 4 and obtain corrected SPT N' values. Delineate soil profile into layers based on corrected SPT N' values. c. Determine angle for each layer from laboratory tests or in-situ data. d. In the absence of laboratory or in-situ test data, determine the average corrected SPT N' value, N', for each soil layer and estimate angle from Table 4-5 in Chapter 4.9-28Nordlund Method ProcedureSTEP 2 Determine , the friction angle between the pile and soil based on the displaced soil volume, V, and the soil friction angle, .a. Compute volume of soil displaced per unit length of pile, V.b. Enter Figure 9.10 with V and determine / ratio for pile type. c. Calculate from / ratio.9-28Relationship Between Soil Displacement, V, and /V = 0.11/ = 0.70a closed-end pipe and non-tapered Monotube pilesb timber pilesc pre-cast concrete pilesd Raymond Step-Taper pilese Raymond uniform pilesf H-pilesg tapered portion of Monotube piles0.75 0.25a closed-end pipe and non-tapered Monotube pilesb timber pilesc pre-cast concrete pilesd Raymond Step-Taper pilese Raymond uniform pilesf H-pilesg tapered portion of Monotube pilesV = 1.0/ = 0.65Relationship Between Soil Displacement, V, and /10Nordlund Method ProcedureSTEP 3 Determine the coefficient of lateral earth pressure Kfor each soil friction angle, .a. Determine Kfor each angle based on displaced volume V, and pile taper angle, , using appropriateprocedure in steps 3b, 3c, 3d, or 3e.b. If displaced volume is 0.0093, 0.093, or 0.930 m3/m and the friction angle is 25, 30, 35, or 40, use Figures 9.11 to 9.14. c. If displaced volume is given but angle is not. Linear interpolationis required to determine Kfor angle.9-28Kversus = 25Figure 9.119-33Kversus = 30Figure 9.129-34Nordlund Method ProcedureSTEP 3 Determine the coefficient of lateral earth pressure Kfor each soil friction angle, .d. If displaced volume is not given but angle is given, log linear interpolationis required to determine Kfor displaced volume V.e. If neither the displaced volume or angle are given, first use linear interpolationto determine Kfor angle and then use log linear interpolationto determine Kfor the displaced volume, V.See Table 9-4 for Kas function of angle and displaced volume V9-29Table 9-4(a) Design Table for Evaluating Kfor Piles when = 0 and V = 0.0093 to 0.0930 m3/m(0.10 to 1.00 ft3/ft)N Displaced Volume -V, m3/m, (ft3/ft)0.0093(0.10)0.0186(0.20)0.0279(0.30)0.0372(0.40)0.0465(0.50)0.0558(0.60)0.0651(0.70)0.0744(0.80)0.0837(0.90)0.0930(1.00)25 0.70 0.75 0.77 0.79 0.80 0.82 0.83 0.84 0.84 0.8526 0.73 0.78 0.82 0.84 0.86 0.87 0.88 0.89 0.90 0.9127 0.76 0.82 0.86 0.89 0.91 0.92 0.94 0.95 0.96 0.9728 0.79 0.86 0.90 0.93 0.96 0.98 0.99 1.01 1.02 1.0329 0.82 0.90 0.95 0.98 1.01 1.03 1.05 1.06 1.08 1.0930 0.85 0.94 0.99 1.03 1.06 1.08 1.10 1.12 1.14 1.1531 0.91 1.02 1.08 1.13 1.16 1.19 1.21 1.24 1.25 1.2732 0.97 1.10 1.17 1.22 1.26 1.30 1.32 1.35 1.37 1.3933 1.03 1.17 1.26 1.32 1.37 1.40 1.44 1.46 1.49 1.5134 1.09 1.25 1.35 1.42 1.47 1.51 1.55 1.58 1.61 1.6335 1.15 1.33 1.44 1.51 1.57 1.62 1.66 1.69 1.72 1.7536 1.26 1.48 1.61 1.71 1.78 1.84 1.89 1.93 1.97 2.0037 1.37 1.63 1.79 1.90 1.99 2.05 2.11 2.16 2.21 2.2538 1.48 1.79 1.97 2.09 2.19 2.27 2.34 2.40 2.45 2.5039 1.59 1.94 2.14 2.29 2.40 2.49 2.57 2.64 2.70 2.7540 1.70 2.09 2.32 2.48 2.61 2.71 2.80 2.87 2.94 3.0Nordlund Method ProcedureSTEP 4 Determine the correction factor CFto be applied to Kif .Use Figure 9.15 to determine the correction factor for each K. Enter figure with angle and / ratio to determine CF.9-2911Figure 9.15Correction Factor for Kwhen Nordlund Method ProcedureSTEP 5 Compute the average effective overburden pressure at the midpoint of each soil layer.STEP 6 Compute the shaft resistance in each soil layer.Sum the shaft from each layer to obtain the ultimate shaft resistance, RS.9-30Nordlund Method Procedurea. Enter Figure 9.16(a) with angle near pile toe to determine t coefficient based on pile length to diameter ratio.b. Enter Figure 9.16(b) with angle near pile toe to determine, N'q.c. If angle is estimated from SPT data, compute the average corrected SPT N' value over the zone from the pile toe to 3 diameters below the pile toe.Use this average corrected SPT N' value to estimate angle near pile toe from Table 4-5.STEP 7 Determine the tcoefficient and the bearing capacity factor, N'q, from the angle near the pile toe.9-30Nordlund Method ProcedureSTEP 8 Compute the effective overburden pressure at the pile toe.NOTE: The limiting value of ptis 150 kPa9-30STEP 9 Compute the ultimate toe resistance, Rt.RT= qLATRT= TNqpTATUse lesser of: Figure 9-16a and 9-16bFigure 9-17 (degrees)tFigure 9.16atCoefficient versus Figure 9.16b12Figure 9.17Limiting Unit Toe Resistance (SI) Limiting Unit Toe Resistance (US)Figure 9.17Nordlund Method ProcedureSTEP 10 Compute the ultimate capacity, Qu.Qu= Rs+ Rt9-31STEP 11 Compute the allowabledesign load, Qa.Qa= Qu/ Factor of SafetySTATICCAPACITY OFPILESIN COHESIVESOILS9-42Cohesive Soils, Undrained StrengthFNc = zeroc = cohesion,stickiness,soil / soila = adhesion,stickiness,soil / pileCis independent of overburden pressuresF = Friction resistance ; N = Normal force (stress)METHODS OF STATIC ANALYSIS FOR PILES IN COHESIVE SOILSMethod Approach Method of ObtainingDesign ParametersAdvantages Disadvantages Remarks-Method(Tomlinson Method).Empirical, total stress analysis.Undrained shear strength estimate of soil is needed. Adhesion calculated from Figures 9.18 and 9.19.Simple calculation from laboratory undrained shear strength values to adhesion.Wide scatter in adhesion versus undrained shear strengths in literature.Widely used method described in Section 9.7.1.2a.Effective Stress Method.Semi-Empirical, based on effective stress at failure. and Ntvalues are selected from Table 9-6 based on drained soil strength estimates.Ranges in and Nt values for most cohesive soils are relatively small.Range in Ntvalues for hard cohesive soils such as glacial tills can be large.Good design approach theoretically better than undrained analysis. Details in Section 9.7.1.3.Methods based on Cone Penetration Test data.Empirical. Results of CPTtests.Testing analogy between CPT and pile.Reproducible test data.Cone can be difficultto advance in very hard cohesive soils such as glacial tills.Good approach for design.Details in Section 9.7.1.7.FHWA9-4313Tomlinson or -MethodUnit Shaft Resistance, fs:fs= ca= cuWhere:ca= adhesion(Figure 9.18) = empirical adhesion factor(Figure 9.19)9-42Tomlinson or -MethodShaft Resistance, Rs:Rs= fsAsWhere:As= pile surface area in layer (pile perimeter x length) H piles use box area 4 sides, pg 45Concrete, Timber, Corrugated Steel PilesSmooth Steel Pilesb = Pile DiameterD = distance from ground surface to bottomofclay layer or pile toe, whichever is lessTomlinson or -Method (SI)Figure 9.18 9-43Concrete, Timber, Corrugated Steel PilesSmooth Steel Pilesb = Pile DiameterD = distance from ground surface to bottomofclay layer or pile toe, whichever is lessTomlinson or -Method (US)Figure 9.18Tomlinson or -MethodDbSand or Sandy GravelsStiff ClayTomlinson or -Method (SI)b = Pile DiameterD = distance into stiff clay layerFigure 9.19a9-4414Tomlinson or -Method (US)b = Pile DiameterD = distance into stiff clay layerFigure 9.19b9-48Tomlinson or -MethodDbSoft ClayStiff ClayTomlinson or -Method (SI)b = Pile DiameterD = distance into stiff clay layerFigure 9.19b9-44Tomlinson or -Method (US)b = Pile DiameterD = distance into stiff clay layerFigure 9.19b9-48Tomlinson or -MethodDbStiff ClayTomlinson or -Method (SI)b = Pile DiameterD = distance into stiff clay layerFigure 9.19c9-4415Tomlinson or -Method (US)b = Pile DiameterD = distance into stiff clay layerFigure 9.19b 9-48HIGHLY OVERCONSOLIDATED CLAYSFor 1.0, = 0.5 -0.5For > 1.0, = 0.5 -0.25 In highly overconsolidated clays, the undrained shear strength may exceed the upper limits of Figures 9.18 and 9.19.In these cases, the adhesion factor should be calculated according to API procedures based on the ratio of the undrained shear strength of the soil, cu, divided by the effective overburden pressure, po.The ratio of cu/ po is .Tomlinson or -MethodUnit Toe Resistance, qt:qt= cu NcWhere:cu= undrained shear strength of the soil at pile toeNc= dimensionless bearing capacity factor(9 for deep foundations)Tomlinson or -MethodToe Resistance, Rt:Rt= qt AtThe toe resistance in cohesive soils is sometimes ignored since the movement required to mobilize the toe resistance is several times greater than the movement required to mobilize the shaft resistance. Ru=RS+ RT Qa=RU/ FSand Tomlinson or -MethodSTUDENT EXERCISE #2Use the -Method described in Section 9.7.1.2a and the Nordlund Method described in Section 9.7.1.1c to calculate the ultimate pile capacity and the allowabledesign load for a 12.75 inch O.D. closed end pipe pile driven into the soil profile described below.The trial pile length for the calculation is 63 feet below the bottom of pile cap excavation which extends 3 feet below grade.The pipe pile has a pile-soil surface area of 3.38 ft2/ft and a pile toe area of 0.89 ft2.Use Figure 9.18 to calculate the shaft resistance in the clay layer.The pile volume is 0.89 ft3/ft.The effective overburden at 56 feet, the midpoint of the pile shaft in the sand layer is 3.73 ksf, and the effective overburden pressure at the pile toe is 4.31 ksf. Remember, the soil strengths provided are unconfined compression test results (cu= qu/ 2).1646 ft20 ftSilty Clay = 127 lbs / ft3qu= 5.46 ksfSet-up Factor = 1.75Dense, Silty F-M Sand = 120 lbs / ft3 = 35Set-up Factor = 1.03 ftSoil ProfileSolution We will discuss this solution during the DRIVEN workshop (ie steps 1-9)STEP 10Qu= Rs+ Rt= 1465 + 410 = 1875 kNSTEP 1 Delineate the soil profile and determine the pile adhesion from Figure 9.18.Layer 1: qu= 260 kPa so cu= D/b =Therefore cafrom Figure 9.18 = Calculate the Shaft Resistance in the Clay Layer Using -Method130 kPa14 m / 324 mm = 43Concrete, Timber, Corrugated Steel PilesSmooth Steel Pilesb = Pile DiameterD = distance from ground surface to bottomofclay layer or pile toe, whichever is lessTomlinson or -Method (SI)Figure 9.18 9-4570STEP 1 Delineate the soil profile and determine the pile adhesion from Figure 9.18.Layer 1: qu= 260 kPa so cu= D/b =Therefore ca=Calculate the Shaft Resistance in the Clay Layer Using The -Method130 kPa14 m / 324 mm = 4370 kPaSTEP 2 Compute the unit shaft resistance, fs,for each soil layer. STEP 3 Compute the shaft resistance in the clay layer.Layer 1: Rs1= ( fs1)( As )( D1) =Calculate the Shaft Resistance in the Clay Layer Using -MethodRs1= (70 kPa)(1.02 m2/m)(13 m) = 928 kN17Calculate the Shaft Resistance in the Sand Layer Using the Nordlund MethodSTEP 1 The podiagram, soil layer determination,and the soil friction angle, N, for each soil layer were presented in theproblem introduction.STEP 2 Determine *.a. Compute volume of soil displaced per unit length of pile, V.V = 0.082 m3/m(per problem description)b. Determine */N from Figure 9.10.V = 0.082 m3/m 6*/N =or *=NRelationship Between Soil Displacement, V, and /V = 0.082/ = 0.62a closed-end pipe and non-tapered Monotube pilesb timber pilesc pre-cast concrete pilesd Raymond Step-Taper pilese Raymond uniform pilesf H-pilesg tapered portion of Monotube piles0.75 0.25Calculate the Shaft Resistance in the Sand Layer Using the Nordlund MethodSTEP 1 The podiagram, soil layer determination,and the soil friction angle, , for each soil layer were presented in theproblem introduction.STEP 2 Determine *.a. Compute volume of soil displaced per unit length of pile, V.V = 0.082 m3/m(per problem description)b. Determine */N from Figure 9.10.V = 0.082 m3/m 6*/N =or *=N= 0.62 0.62 0.62 (35 ) = 21.7STEP 3 Determine K*for each soil layer based on displaced volume, V, and pile taper angle, .Layer 2: For = 35, V = 0.082 m3/mand = 0From Figure 9.13: K= 1.15 forV = 0.0093 m3/mK= 1.75 forV = 0.093 m3/mUsing log linear interpolationK= 1.72forV = 0.082 m3/m0.62STEP 4 Determine correction factor, CF, to be appliedto Kwhen .(Figure 9.15.)Layer 2: = 35 and / =CF=Calculate the Shaft Resistance in the Sand Layer Using the Nordlund MethodFigure 9.15Correction Factor for Kwhen = 35CF= 0.78STEP 3 Determine K*for each soil layer based on displaced volume, V, and pile taper angle, .Layer 2: For = 35, V = 0.082 m3/mand = 0From Figure 9.13: K= 1.15 forV = 0.0093 m3/mK= 1.75 forV = 0.093 m3/mUsing log linear interpolationK= 1.72forV = 0.082 m3/m0.62STEP 4 Determine correction factor, CF, to be appliedto Kwhen .Layer 2: = 35 and / =CF= 0.78Calculate the Shaft Resistance in the Sand Layer Using the Nordlund Method18STEP 5 Compute effective overburden pressure at midpoint of each soil layer, pd.From problem description, pdfor layer 2 is 177 kPa.STEP 6 Compute the shaft resistance for each soil layer.Rs2=KCFpdsin CdD= (1.72) (0.78) (177 kPa) (sin 21.7) (1.02 m2/m) (6m)= 537 kNCalculate the Shaft Resistance in the Sand Layer Using the Nordlund MethodRs= Rs1+ Rs2Rs= 928 kN + 537 kNRs= 1465 kNCompute the Ultimate Shaft Resistance, RsSTEP 7 Determine tcoefficient and bearing capacity factor N'qfrom angle of 35 at pile toe and Figures 9.16(a) and 9.16(b)At pile toe depth D/b =From Figure 9.16(a)t= From Figure 9.16(b)N'q= Compute the Ultimate Toe Resistance, Rt20 / .324 = 62 (degrees)tFigure 9.16atCoefficient versus = 350.67Figure 9.16b65STEP 7 Determine tcoefficient and bearing capacity factor N'qfrom angle of 35 at pile toe and Figures 9.16(a) and 9.16(b)At pile toe depth D/b = 62From Figure 9.16(a)t= 0.67From Figure 9.16(b)N'q= 65STEP 8 Compute effective overburden pressure at pile toe.pt=Compute the Ultimate Toe Resistance, Rt150 kPa19STEP 9 Compute the ultimate toe resistance, Rt.a. Rt=tN'qAtptb. Rt=qLAt(qLdetermined from Figure 9.17)c. Use lesser value of Rtfrom Step 9a and 9b.Therefore, Rt=Compute the Ultimate Toe Resistance, Rt= (0.67)(65)(0.082 m2)(150 kPa) = 536 kNFigure 9.17Limiting Unit Toe Resistance (SI)5000STEP 9 Compute the ultimate toe resistance, Rt.a. Rt=tN'qAtptb. Rt=qLAt(qLdetermined from Figure 9.17)c. Use lesser value of Rtfrom Step 9a and 9b.Therefore, Rt=Compute the Ultimate Toe Resistance, Rt= (0.67)(65)(0.082 m2)(150 kPa) = 536 kN= (5000 kPa)(0.082 m2) = 410 kN410 kNCompute the Ultimate Pile Capacity, QuSTEP 10Qu= Rs+ Rt= 1465 + 410 = 1875 kN9-53DRIVEN COMPUTER PROGRAMCan be used to calculate the static capacity of open and closed end pipe piles, H-piles, circular or square solid concrete piles, timber piles, and Monotube piles. Analyses can be performed in SI or US units.DRIVEN uses the FHWA recommended Nordlund (cohesionless) and -methods (cohesive).Available at:www.fhwa.dot.gov/bridge/geosoft.htm9-53DRIVEN COMPUTER PROGRAMUser inputs soil profile identifying soil statigraphy, soil type (cohesionless or cohesive), soil unit weight, soil strength parameters ( or cu) and percentage strength loss during driving.Program analysis options include:Soft compressible soilsScourable soilsPile plugging209-61DRIVEN COMPUTER PROGRAMDRIVEN calculates the pile capacity at the time of driving using user input soil strength losses (Driving), the capacity after time dependent strength changes have occurred (Restrike), and the capacity after extreme events (Ultimate). % Driving Strength Loss = 1 [1 / setup factor]DRIVEN generates soil input file for GRLWEAP wave equation program.DRIVEN COMPUTER PROGRAM Student exercise #4 9-589-599-599-60219-60Go ToTabular Output9-629-62Go ToGraphicalOutput9-621482 kN9-631877 kN9-6322CreateGRLWEAP DriveabilityAnalysis File9-62 NIMPILES DRIVEN TO ROCK9-54The capacity of piles driven to rock should be based on driving observations, local experience, and load test results.RQD values from NX size rock cores can provide a qualitative assessment of rock mass quality.RQD Rock Mass Quality90 100 Excellent75 90 Good50 75 Fair25 50 Poor0 - 25 Very PoorWhat is RQD?PILES DRIVEN TO ROCK9-54Except for piles driven to soft rock, the structural capacity of the pile will be lower than the geotechnical capacity of the rock to support a toe bearing pile.(Fair to excellent quality rock).The structural capacity of the pile (Chapter 10) then governs the pile capacity.METHODS BASED ON CPT DATAElsami and FelleniusNottingham and SchmertmannLaboratoire des Ponts et Chaussees (LPC)Pages 9-65 through 9-80UPLIFTCAPACITYOF SINGLEPILES pg 9-81Increasingly important design considerationSources of uplift loads include seismic events, vessel impact, debris loading and cofferdam dewatering.The design uplift load may be taken as 1/3 the ultimate shaft resistance from a static analysis.23UPLIFTCAPACITYOF SINGLEPILES Undrained clays uplift = compression Drained sands- uplift < compressionUPLIFTCAPACITYOF SINGLEPILESThe design uplift load may be taken as 1/2 the ultimate tension load test failure load defined in Section 19.8.3 of Chapter 19.A reduction in the design uplift load may be necessary under cyclic or sustained loading conditions.Clays peak strength to a residual strengthSands particle degradation or reorientationLesson 7 Learning OutcomesYou will be able to: Identify the FHWA recommended static analysis methods in cohesionless and cohesive soils. Calculate, by hand, the axial compression capacity of a single pile in cohesionless, cohesive, and layered soils.Lesson 7 Learning OutcomesYou will be able to: Determine when the axial compression capacity is controlled by the structural pile capacity. Discussthe DRIVEN software for axial compression capacity calculations.Lesson 7 Learning OutcomesYou will be able to: Determine when the axial compression capacity is controlled by the structural pile capacity. Discussthe DRIVEN and LPILE software for axial compression and lateral capacity calculations. Locate 3 lateral pile capacity design methods.Any Questions24STATIC ANALYSIS SINGLE PILESLATERAL CAPACITY METHODSReference Manual Chapter 9.7.39-82Lateral Capacity of Single Piles Potential sources of lateral loads include vehicle acceleration & braking, wind loads, wave loading, debris loading, ice forces, vessel impact, lateral earth pressures, slope movements, and seismic events. These loads can be of the same magnitude as axial compression loads.Lateral Capacity of Single Piles Historically, prescription values were used for lateral capacity of vertical piles, or battered (inclined) piles were added. Modern design methods are readily available which allow load-deflection behavior to be rationally evaluated.Lateral Capacity of Single PilesSoil, pile, and load parameters significantly affect lateral capacity. Soil Parameters Soil type & strength Horizontal subgrade reaction Pile Parameters Pile properties Pile head condition Method of installation Group action Lateral Load Parameters Static or Dynamic EccentricityLateral Capacity of Single PilesDesign Methods Lateral load tests Analytical methods Broms method, 9-86, (long pile, short pile) Reeses COM624P method LPILE program FB-PIER9-85Figure 9.36 Soil Resistance to a Lateral Pile Load (adapted from Smith, 1989)9-8325NIMFigure 9.44LPILE Pile-Soil Model9-101NIMNIMFigure 9.45Typical p-y Curves for Ductile and Brittle Soil (after Coduto, 1994)9-102Figure 9.47Comparison of Measured and COM624P Predicted Load-DeflectionBehavior versus Depth (after Kyfor et al. 1992)9-9326Figure 9.48LPILE Main Screen9-1069-1079-1079-1099-111 9-11427Figure 9.36Graphical Presentation of LPILE Results (Reese, et al. 2000)9-92DifferentiateIntegrateANY QUESTIONS ?