Frank Rausche2011, Pile Dynamics, Inc.

GRLWEAP: Fundamentals, Models, ResultsGRLWEAP: Fundamentals, Models, Results

Background – Part 1Background – Part 1

• History and Objectives• History and Objectives

• Wave Equation Pile Model• Wave Equation Pile Model• Hammer Models• Hammer Models• Wave Equation Soil Model• Wave Equation Soil Model

• Program Flow –• Bearing Graph

• Inspector’s Chart

• Program Flow –• Bearing Graph

• Inspector’s Chart

• Wave Equation Numerics• Wave Equation Numerics

• Driven Pile Design, Energy Concepts• Driven Pile Design, Energy Concepts

1800s Closed Form Solutions1850s First Energy Formula1950: Smith’s Wave Equation1960s Dynamic Testing and CAPWAP1976: WEAP, TTI1980s: GRLWEAP1986: Hammer Performance Study1996, 2006: FHWA Manual updates

Dynamic Pile Analysis Developments

WAVE EQUATION OBJECTIVESWAVE EQUATION OBJECTIVES

• Smith’s Basic Premise: – Replace Energy Formula– Use improved pile model (elastic pile) and soil model

(elasto-plastic static resistance with damping)– Allow for realistic stress calculations

• Additional GRLWEAP developments expand the basic capabilities Inspectors’ Graph analysis option Driveability analysis option Diesel hammer analysis Residual stress analysis Static geotechnical analyses Special offshore analysis options

GRLWEAP Analysis OptionsGRLWEAP Analysis Options

• Bearing Graph for capacity from observed blow count– Hammer performance fixed– One depth– Assumed capacity values (10)

• Inspectors’ Chart for required blow count– Hammer performance variable– One depth– One capacity

• Driveability Analysis for anticipated blow counts– Hammer performance fixed– Assumed depth values (100)– Several capacity values for each depth (5)

GRLWEAP ObjectivesGRLWEAP Objectives

• WHEN SHOULD WE DO THE ANALYSIS?– Before pile driving begins

– After initial pile tests have been done (refined)

• FOR WHAT PURPOSE?– Formulate driving criterion:

• Safe stresses

• Required blow count for sufficient capacity

– Adequate equipment (e.g., hammer) selection

– Pile stress determination

– Blow count calculation for required capacity

– Capacity from observed blow count

Basic design approach for driven pilesBasic design approach for driven piles

1. Obtain Design Load (Qd) from structural design

2. Decide on Safety Concept (FS)

3. Decide on Pile Type based on suitability and availability

4. Perform Static Pile Analysis, determine Ultimate Capacity (Ru) for assumed Pile Length.

5. Find Pile Length so that Ru > FS Qd

Basic design approach continuedBasic design approach continued

6. Compute Blow Count for Ru - check Driveability by GRLWEAP

7. Either perform an initial Test Program, testing piles dynamically, sometimes statically

8. Establish Installation Criterion (min. penetration, required blow count)

9. Install Production Piles to criterion

10.For all production piles, final pile length is determined at installation time

Reference:

Hannigan, P.J., G.G. Goble, G.E. Likins, and F. Rausche. Design and Construction of Driven Pile Foundations - Volumes 1 and 2. Publication Numbers FHWA-NHI-05-042 and 043. Washington, D.C.: U.S. Department of Transportation Federal Highway Administration, 2006.

Factor of SafetyFactor of Safety

Ru ≤ (FS) Qd

• Ru Ultimate Capacity

(Nominal or Characteristic Resistance)

• FS Global Factor of Safety (1.5 < F.S. < 10)

(for LRFD: FS =Combined Load/Resistance Factor)

• Qd Design Load

(Safe Load, Working Load, Sum of Unfactored

Loads)

GRLWEAP works exclusively with Ru

Static Analysis MethodsStatic Analysis Methods

Ru = Rs + Rt

Ru = fsAs + qt At

fs, As …Unit/Shaft Resistance, Area

qt, At … Unit/End Bearing, Area

Ru = Rs + Rt

Ru = fsAs + qt At

fs, As …Unit/Shaft Resistance, Area

qt, At … Unit/End Bearing, Area

Rs

Rt

Q

The α-Method For example: Total Stress method for cohesive soils

The α-Method For example: Total Stress method for cohesive soils

• Rs = fs As with fs = α cUα is an empirical adhesion factor

cU is the undrained shear strength

• Rt = 9 cU

After Tomlinson, 1979

• Rs = fs As with fs = α cUα is an empirical adhesion factor

cU is the undrained shear strength

• Rt = 9 cU

After Tomlinson, 1979

The β-Method primarily for cohesionless soils

The β-Method primarily for cohesionless soils

• Rs = fs As with fs = β po β = ko tan(δ)po is the effective overburden pressure

ko is some earth pressure coefficient

• Rt = Nt po AtNt is a bearing

capacity factor

after Fellenius, 1991

... with certain limits

• Rs = fs As with fs = β po β = ko tan(δ)po is the effective overburden pressure

ko is some earth pressure coefficient

• Rt = Nt po AtNt is a bearing

capacity factor

after Fellenius, 1991

... with certain limits

Static Analysis MethodsStatic Analysis Methods

GRLWEAP’s Static Analysis Methods

GRLWEAP’s Static Analysis Methods

Rs

Rt

Q

Icon Input Basic AnalysisST Soil Type Effective Stress, Total StressSA SPT N-value Effective StressCPT R at cone tip and sleeve SchmertmannAPI φ, Su Effective Stress, Total Stress

• GRLWEAP’s static analysis methods may be used for dynamic analysis preparation (resistance distribution, estimate of capacity for driveability).

• For design, be sure to use a method based on local experience.

Use of Static Analysis MethodsUse of Static Analysis Methods

• Should always be done for finding reasonable pile type and length

• For driven piles static analysis is only a starting point, since pile length is determined in the field (exceptions are piles driven to depth, for example, because of high soil setup)

• For LRFD when finding pile length by static analysis method use resistance factor for selected capacity verification method

Energy ConsiderationsIf we take PDA measurements….

Energy ConsiderationsIf we take PDA measurements….

…we can calculate the Transferred Energy

WR

h

ER = WR hManufacturer’s Rating

WR

Max ET = ∫F(t) v(t) dt(ENTHRU)

ηT = ENTHRU/ ER

(transfer ratio or efficiency)Measure Force, F(t)Velocity, v(t)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

PE

RC

EN

TIL

E

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

DIESEL HAMMERS ON STEEL PILESN = 732; MEDIAN = 36.8%

ENERGY TRANSFER RATIO [EMX / E-RATED]

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

FR

EQ

UE

NC

Y

0-5% 10-15% 20-25% 30-35% 40-45% 50-55% 60-65% 70-75% 80-85% 90-95%

ENERGY TRANSFER RATIO [EMX / E-RATED]

MEAN = 36.8%STANDARD DEVIATION = 9.5%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

PE

RC

EN

TIL

E

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

DIESEL HAMMERS ON CONC./TIMBER PILESN = 394; MEDIAN = 24.9%

ENERGY TRANSFER RATIO [EMX / E-RATED]

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

FR

EQ

UE

NC

Y

0-5% 10-15% 20-25% 30-35% 40-45% 50-55% 60-65% 70-75% 80-85% 90-95%

ENERGY TRANSFER RATIO [EMX / E-RATED]

MEAN = 26.1%STANDARD DEVIATION = 7.9%

For all impact hammers GRLWEAP needs impact velocity

WP

WR

hEP = WR h (potential, ideal)

EP = WR h η (η = Hammer efficiency )WR

vi

EK = ½ mR vi2 (kinetic energy)

mR = WR / gEP = EK

vi = 2g hη

Energy (Dynamic) FormulasEnergy (Dynamic) Formulas

Energy Dissipated in Soil =

Energy Provided by Hammer

Ru (s + sl) = ηWr h

sl … “lost” set (empirical or measured),

η … efficiency of hammer/driving system

Energy Dissipated in Soil =

Energy Provided by Hammer

Ru (s + sl) = ηWr h

sl … “lost” set (empirical or measured),

η … efficiency of hammer/driving system

Bearing Graphs from 2 Energy FormulasHammer D 19-42; Er = 59 kJ

Bearing Graphs from 2 Energy FormulasHammer D 19-42; Er = 59 kJ

0

500

1000

1500

2000

2500

3000

3500

4000

0 25 50 75 100 125 150 175 200

Blows/0.25 m

Ca

pa

cit

y in

kN

Gates - w/ calculated Stroke ENR - Ru = Rd x 2

Ru = ηEr /(s + sl)η = 1/3; sl = 2.5mm

Ru = 1.6 Ep ½ log(10Blows/25mm) – 120 kN

4000[900]

Ru - kN[kips]

2000[450]

0

0 5 10 15 20Blows/25mm

THE WAVE EQUATION MODELTHE WAVE EQUATION MODEL

• The Wave Equation Analysis calculates the displacement of any point of a slender elastic rod at any time.

• The calculation is based on rod

– Length

– Cross Sectional Area

– Elastic Modulus

– Mass density

GRLWEAP FundamentalsGRLWEAP Fundamentals

• For a pile driving analysis, the “rod” is Hammer+Driving System+Pile

• The rod is assumed to be elastic(?) and slender(?)

• The soil is represented by resistance forces acting at the pile soil interface

Ham

mer

D.S.

Pil

eGRLWEAP Pile ModelGRLWEAP Pile Model

To solve the wave equation numerically:• The pile is divided into N segments

– of approximate length ∆L typically: ∆L = 1 m (3.3 ft)

– with mass m = ρ A ∆L

– and stiffness k = E A / ∆L

– there are N = L / ∆L pile segments

• The analysis time is divided into intervalstypically: ∆t = 0.1 ms

∆L

GRLWEAP Time Increment, ∆tGRLWEAP Time Increment, ∆t∆t is a fraction (e.g. ½ ) of the critical time, which is ∆L/c∆t is a fraction (e.g. ½ ) of the critical time, which is ∆L/c

∆tcr

∆ L

L/c

∆t

Time

Length

GRLWEAP Hammer ModelsGRLWEAP Hammer Models

Ram: A, L for stiffness, mass

Cylinder and upper frame = assembly top mass

Drop height

External Combustion Hammer ModelingExternal Combustion Hammer Modeling

Ram guides for assembly stiffness

Hammer base = assembly bottom mass

External Combustion Hammer ModelExternal Combustion Hammer Model

• Ram modeled like rod

• Stroke is an input (Energy/Ram Weight)

• Impact Velocity Calculated from Stroke with Hammer Efficiency Reduction: vi = (2 g h η) ½

• Assembly also modeled because it may impact during pile rebound

• Note approximation in data file:

Assembly mass = Total hammer mass – Ram mass

External Combustion HammersRam Model

External Combustion HammersRam Model

Ram segments ~1m long

Ram segments ~1m long

Combined Ram-H.Cushion

Helmet mass

Combined Ram-H.Cushion

Helmet mass

External Combustion HammersCombined Ram Assembly Model

External Combustion HammersCombined Ram Assembly Model

Combined Ram-H.Cushion

Helmet mass

Combined Ram-H.Cushion

Helmet mass

Ram segments

Assembly segments

Ram segments

Assembly segments

External Combustion HammerProcedure

External Combustion HammerProcedure

• Static equilibrium analysis

• Dynamic analysis starts when ram is within 1 ms of impact.

• All ram segments then have velocity

VRAM = (2 g h η)1/2 – 0.001 gg is the gravitational acceleration

h is the equivalent hammer stroke and η is the hammer efficiency

h = Hammer potential energy/ Ram weight

External Combustion HammerProcedure

External Combustion HammerProcedure

• Dynamic analysis ends when

– Pile toe has rebounded to 80% of max dtoe

– Pile has penetrated more than 4 inches

– Pile toe has rebounded to 98% of max dtoe and energy in pile is essentially dissipated

DIESEL HAMMERSDIESEL HAMMERSClosed Ended Open Ended

Diesel hammer componentsDiesel hammer components

Piston = RamPiston = Ram

Port (closed by piston)Port (closed by piston)

Combustion chamberCombustion chamber

Impact blockImpact block

Hammer Cushion; HelmetHammer Cushion; Helmet

CylinderCylinder

Compressive strokeCompressive stroke

DIESEL Hammer MODELDIESEL Hammer MODEL

• Ram, Impact Block modeled like rods• Compression, Expansion Pressures from Gas

Law• Combustion Pressure from rated energy –

measurements; different for Atomized and Liquid Fuel injection

• Ram velocity reduced by efficiency just before impact

• Ram, Impact Block modeled like rods• Compression, Expansion Pressures from Gas

Law• Combustion Pressure from rated energy –

measurements; different for Atomized and Liquid Fuel injection

• Ram velocity reduced by efficiency just before impact

Diesel Hammer Ram ModelDiesel Hammer Ram Model

Hammer Cushion

Helmet mass

Hammer Cushion

Helmet mass

Ram segments ~1m longRam segments ~1m long

Impact Block massImpact Block mass

Ram bottom/impact blockRam bottom/impact block

Diesel Hammer Combustion Pressure ModelDiesel Hammer Combustion Pressure Model

Precompression-Combustion-Expansion-Pressure

Precompression-Combustion-Expansion-Pressure

PortsPorts

• Compressive Stroke, hC

• Cylinder Area, ACH

• Final Chamber Volume, VCH

• Max. Pressure, pMAX

• Compressive Stroke, hC

• Cylinder Area, ACH

• Final Chamber Volume, VCH

• Max. Pressure, pMAX

hChC

DIESEL PRESSURE MODELLiquid Injection Hammers

DIESEL PRESSURE MODELLiquid Injection Hammers

TimeTime

Pressure

Por

t

Ope

ns

Por

t

Ope

ns

Compression:

p=patm(Vin/V)1.35

Compression:

p=patm(Vin/V)1.35

pMAX

Expansion:

p=pMAX(VCH/V)1.25

Expansion:

p=pMAX(VCH/V)1.25tD

Combustion Duration, tDCombustion Duration, tD

Combustion Delay, ∆tCombustion Delay, ∆t

∆t

Downward = upward stroke

Program Flow – Diesel HammersFixed pressure, variable stroke

Program Flow – Diesel HammersFixed pressure, variable stroke

Downward = rated stroke

Calculate pile andram motion

Find upward stroke

Output

Strokes match?

Setup hammer,pile, soil model

Next Ru?

N

N

GRLWEAP hammer efficiencies (Ek/EP)GRLWEAP hammer efficiencies (Ek/EP)

•The hammer efficiency reduces the impact velocity of the ram; it is based on experience•Hammer efficiencies cover all losses which cannot be calculated•Diesel hammer energy loss due to pre-compression or cushioning can be calculated and, therefore, is not covered by hammer efficiency

GRLWEAP diesel hammer efficienciesGRLWEAP diesel hammer efficiencies

Open end diesel hammers: 0.80uncertainty of fall height, friction, alignment

Closed end diesel hammers: 0.80uncertainty of fall height, friction, power assist, alignment

Modern Hydraulic Hammer Efficiencies

Modern Hydraulic Hammer Efficiencies

Hammers with internal monitor: 0.95uncertainty of hammer alignment

Hydraulic drop hammers: 0.80uncertainty of fall height, alignment, friction

Power assisted hydraulic hammers: 0.80uncertainty of fall height, alignment, friction, power assist

Air/Steam/Traditional Hydraulic Hammer Efficiency Recommendations

Air/Steam/Traditional Hydraulic Hammer Efficiency Recommendations

Single acting Air/Steam hammers: 0.67fall height, preadmission, friction, alignment

Double acting Air/Steam/Hydraulic: 0.50preadmission, reduced pressure, friction, alignment

Drop HammerEfficiency Recommendations

Drop HammerEfficiency Recommendations

• Drop hammers brake released: 0.50covers uncertainty of fall height and winch losses

• Drop hammers free released: 0.67covers uncertainty of fall height

VIBRATORY HAMMER MODEL

VIBRATORY HAMMER MODEL

VIBRATORY HAMMER MODELVIBRATORY HAMMER MODEL

Vibratory Force:FV = me [ω2resin ω t - a2(t)]

FLFL

FVFV

m1m1

m2m2

• Line Force

• Bias Mass and

• Oscillator mass, m2

• Eccentric masses, me, radii, re

• Clamp

GRLWEAP Hammer data fileGRLWEAP Hammer data file

Driving System ModelingDriving System Modeling

Driving Systems Consists of1. Helmet including inserts to align hammer and pile

2. Hammer Cushion to protect hammer

3. Pile Cushion to protect concrete piles

Driving system model (Concrete

piles)

Driving system model (Concrete

piles)

Pile Cushion + Pile Top: Spring + Dashpot

Pile Cushion + Pile Top: Spring + Dashpot

Helmet + InsertsHelmet + Inserts

Hammer Cushion: Spring plus Dashpot

Hammer Cushion: Spring plus Dashpot

Non-linear springsfor cushions and slacks

Non-linear springsfor cushions and slacks

Parameters1. Stiffness, k = EA/t

2. Coefficient of Restitution, COR

3. Round-out deformation, δr , or compressive slack

4. Tension slack, δs

δrδr

k /COR2k /COR2k

δsδsCompressive Deformation

Compressive Deformation

Compressive ForceCompressive Force

Non-linear springsSprings at material interfaces

Non-linear springsSprings at material interfaces

Hammer interface springs

Cushions

Helmet/Pile

Splices with slacks

Hammer interface springs

Cushions

Helmet/Pile

Splices with slacks

∆L= L/N 1m (default)

Soil ModelSpring (static resistance)

Dashpot (dynamic resistance)

Mass density, Modulus, EX-Area, A

Mass, mi

Stiffness, ki

The Pile and Soil ModelThe Pile and Soil Model

Soil ResistanceSoil Resistance

• Soil resistance slows pile movement and causes pile rebound

• A very slowly moving pile only encounters static resistance

• A rapidly moving pile also encounters dynamic resistance

• The static resistance to driving differs from the soil resistance under static loads

Soil Model ParametersSoil Model Parameters

Segment

i

ki,Rui

Ji

RIGID SOIL

Segment

i-1

Segment

i+1

ki+1,Rui+1

Ji+1

ki-1,Rui-1

Ji-1

Pile

-So

il In

terf

ace

Smith’s Soil ModelSmith’s Soil Model

Total Soil ResistanceRtotal = Rsi +Rdi

Total Soil ResistanceRtotal = Rsi +Rdi

Segment

i

ui

vi

Fixed

Rigid plastic slider with Resistance Rui

Elastic spring with max. compression q (quake)

Fixed referenceFixed reference

ui

Rui

Rsi

ksi = Rui /qi

1

quake, qi

Static Shaft Resistance ModelParameters Rui, qi

Static Shaft Resistance ModelParameters Rui, qi

Shaft Resistance and QuakeShaft Resistance and Quake

qi

Rui

qi

Rsi

ui

-Rui

Recommended Shaft Quake:

2.5 mm; 0.1 inches

Recommended Toe Quakes, qtRecommended Toe Quakes, qt

0.1” or 2.5 mm

0.04” or 1 mm on hard rock

qt

RqtRut

u

D/120: very dense/hard soils

D/60: softer/loose soils

Displacement pilesNon-displacement piles

D

Smith’s Soil Damping Model (Shaft or Toe)Smith’s Soil Damping Model (Shaft or Toe)

PileSegment

Smith damping factor,Js [s/m or s/ft]

Rd = RsJs v

Fixed reference (soil around pile)

velocity v

Rd = RuJsv v

Smith-viscous damping factor Jsv [s/m or s/ft]

For RSA and Vibratory Ananlysis

dashpot

Recommended Smith damping factorsRecommended Smith damping factors

Shaft

Clay: 0.65 s/m or 0.20 s/ft

Sand: 0.16 s/m or 0.05 s/ft

Silts: use an intermediate value

Layered soils: use a weighted averagefor bearing graph

Toe

All soils: 0.50 s/m or 0.15 s/ft

GRLWEAP Help forDynamic Soil Resistance Parameters

GRLWEAP Help forDynamic Soil Resistance Parameters

How to Distribute the Static Soil Resistance Along Pile and at ToeHow to Distribute the Static Soil

Resistance Along Pile and at Toe

1. SimplestI. Percentage Shaft resistance

(from static soils analysis)II. Triangular or Rectangular or

Trapezoidal

Only Reasonable for a simple Bearing Graph where little is known

about soil.

End Bearing = Total Capacity x (100% - Percent Shaft

Resistance)

Pen

etra

tio

n

How to Distribute the Static Soil Resistance Along Pile and at toeHow to Distribute the Static Soil Resistance Along Pile and at toe

2. Still Simple:ST Analysis based on some knowledge of Soil Types

Reasonable for a simple Bearing Graph; for Driveability possible, but more accurate analysis should be

done.

End Bearing = From Soil Type, Pile Bottom Area

Pen

etra

tio

n

How to Distribute the Static Soil Resistance Along Pile and at toeHow to Distribute the Static Soil Resistance Along Pile and at toe

3. More Involved:I. SA

Input: SPT Blow Count, Friction Angle or Undrained Shear Strength

II. APIInput: Friction Angle or Undrained Shear Strength

III. CPTInput: Cone Record including tip resistance and Sleeve Friction vsdepth.

Pen

etra

tio

n

All are good for a Bearing GraphMay be OK for Driveability Analysis

Local experience may provide better values

Numerical TreatmentNumerical Treatment

• Predict displacements:

uni = uoi + voi ∆t

• Predict displacements:

uni = uoi + voi ∆t

Fi, ci

uni-1

mi

mi+1

mi-1

uni

uni+1

Ri-1

Ri

Ri+1

• Calculate spring compression:

ci = uni - uni-1

• Calculate spring compression:

ci = uni - uni-1

• Calculate spring forces:

Fi = ki ci

• Calculate spring forces:

Fi = ki ci

• Calculate resistance forces:

Ri = Rsi + Rdi

• Calculate resistance forces:

Ri = Rsi + Rdi

Force balance at a segmentForce balance at a segment

Acceleration: ai = (Fi + Wi – Ri – Fi+1) / mi

Velocity, vi, and Displacement, ui, from Integration

Acceleration: ai = (Fi + Wi – Ri – Fi+1) / mi

Velocity, vi, and Displacement, ui, from Integration

Mass mi

Force from upper spring, Fi

Force from lower spring, Fi+1

Resistance force, RiWeight, Wi

Set or Blow Count Calculation (a) Simplified: extrapolated toe displacement

Set or Blow Count Calculation (a) Simplified: extrapolated toe displacement

RR

SetSetFinal SetFinal Set

Maximum SetMaximum Set

QuakeQuake

RuRu

ExtrapolatedExtrapolated

CalculatedCalculated

(b) Blow Count Calculation by RSA(b) Blow Count Calculation by RSA

• Residual Stress Analysis is also called Multiple Blow Analysis

• Analyzes several blows consecutively with initial stresses, displacements from static state at end of previous blow

• Yields residual stresses in pile at end of blow; generally lower blow counts

• Residual Stress Analysis is also called Multiple Blow Analysis

• Analyzes several blows consecutively with initial stresses, displacements from static state at end of previous blow

• Yields residual stresses in pile at end of blow; generally lower blow counts

Blow Count Calculation(b) Residual Stress Analysis (RSA)

Blow Count Calculation(b) Residual Stress Analysis (RSA)

Set for 2 Blows

Convergence:Consecutive Blows

have same pile compression/sets

Static EquilibriumRam velocity

Dynamic analysis

Program Flow – Bearing GraphProgram Flow – Bearing Graph

Model hammer,driving system

and pile

• Pile stresses• Energy transfer• Pile velocitiesChoose first Ru

Calculate BlowCount

Distribute RuSet Soil Constants

Output

IncreaseRu?

Increase Ru Input

N

Y

Bearing Graph: Variable Capacity, One depthSI-Units; Clay and Sand Example; D19-42; HP 12x53;

Bearing Graph: Variable Capacity, One depthSI-Units; Clay and Sand Example; D19-42; HP 12x53;

The Inspectors’ Chart: One Capacity and One Depth – Stroke Variable

The Inspectors’ Chart: One Capacity and One Depth – Stroke Variable

21-Aug-2011GRL Engineers, Inc. GRLWEAP Version 2010Demo 3-Inspector's Chart - D16-32

21-Aug-2011GRL Engineers, Inc. GRLWEAP Version 2010Demo 3-Inspector's Chart - D16-32

Com

pre

ssiv

e S

tress

(M

Pa)

0

50

100

150

200

250

Tensi

on S

tress

(M

Pa)

0

50

100

150

200

250

Blow Count (blows/.25m)

Stroke

(m

)

40 80 120 160 200 240 2801.50

1.90

2.30

2.70

3.10

3.50

DELMAG D 16-32

Capacity 1600.0 kNRam Weight 15.66 kNEfficiency 0.800Pressure 9825 (99%) kPa

Helmet Weight 8.45 kNHammer Cushion 10535 kN/mmCOR of H.C. 0.800

Skin Quake 2.500 mmToe Quake 2.500 mmSkin Damping 0.259 sec/mToe Damping 0.500 sec/m

Pile LengthPile PenetrationPile Top Area

18.28 16.76

140.64

m m cm2

Pile ModelSkin FrictionDistribution

Res. Shaft = 30 %(Proportional)

Formulas and Wave EquationD19-42; HP 12x53; Clay and Sand

Formulas and Wave EquationD19-42; HP 12x53; Clay and Sand

0

500

1000

1500

2000

2500

3000

3500

4000

0 25 50 75 100 125 150 175 200

Blows/0.25 m

Cap

acit

y in

kN

Gates ENR GRLWEAP-Clay GRLWEAP-Sand

SUMMARYSUMMARY

• GRLWEAP simulates the what happens when a hammer strikes a pile

• GRLWEAP is based on Smith’s model with important extensions such as:– Realistic hammer models (ECH, OED, CED, VIB)

– Non-linear spring models for interfaces and slacks

– Alternative soil models

– Residual stress analysis

• GRLWEAP simulates the what happens when a hammer strikes a pile

• GRLWEAP is based on Smith’s model with important extensions such as:– Realistic hammer models (ECH, OED, CED, VIB)

– Non-linear spring models for interfaces and slacks

– Alternative soil models

– Residual stress analysis

SUMMARY, continuedSUMMARY, continued

• GRLWEAP , to simplify input offers four static pile analysis methods– Soil type based (ST)

– N-value and qu based (SA)

– φ and Su based (API)

– Cone Penetrometer based (CPT)

• GRLWEAP , to simplify input offers four static pile analysis methods– Soil type based (ST)

– N-value and qu based (SA)

– φ and Su based (API)

– Cone Penetrometer based (CPT)

Summary, continuedSummary, continued

• GRLWEAP models 3 distinctly different hammer models– External Combustion Hammer models

– Diesel hammer and pressure models

– Vibratory hammer model

• GRLWEAP works with 3 components in the driving system model– Hammer Cushion

– Helmet and Inserts

– Pile Cushion

• GRLWEAP models 3 distinctly different hammer models– External Combustion Hammer models

– Diesel hammer and pressure models

– Vibratory hammer model

• GRLWEAP works with 3 components in the driving system model– Hammer Cushion

– Helmet and Inserts

– Pile Cushion

Summary, continuedSummary, continued

• Basic Analysis options are the– Bearing Graph which relates 10 bearing capacity values

and stresses to blow count and

– Inspector’s Chart which relates required blow count to a hammer’s energy level (or stroke) for one capacity value.

• Basic Analysis options are the– Bearing Graph which relates 10 bearing capacity values

and stresses to blow count and

– Inspector’s Chart which relates required blow count to a hammer’s energy level (or stroke) for one capacity value.

End of GRLWEAP FundamentalsEnd of GRLWEAP Fundamentals

Questions?Questions?

Bearing Graph Workshop examplesBearing Graph Workshop examples

• Bearing Graph; CE Pipe driven by diesel hammer

• Bearing Graph and Inspector’s Chart for inclined/battered concrete pile

• Steel follower on concrete pile

• Bearing Graph; CE Pipe driven by diesel hammer

• Bearing Graph and Inspector’s Chart for inclined/battered concrete pile

• Steel follower on concrete pile

Diesel hammer bearing graphDiesel hammer bearing graph

Hammer: Find appropriate OE Diesel Find Associated Driving System

Pile: 12-3/4x3/8”; 325x10 mmClosed Ended PipeLength L = 50’ (15 m)

Soil: Sand

Desired working load 50 tonsSafety Concept: Wave Equation OnlyExpected Penetration LP = 45’ (14 m)

Hammer: Find appropriate OE Diesel Find Associated Driving System

Pile: 12-3/4x3/8”; 325x10 mmClosed Ended PipeLength L = 50’ (15 m)

Soil: Sand

Desired working load 50 tonsSafety Concept: Wave Equation OnlyExpected Penetration LP = 45’ (14 m)

LLLP

Continue: Concrete pile bearing graph and Inspector’s Chart

Continue: Concrete pile bearing graph and Inspector’s Chart

Hammer: Find appropriate ECHBoth Hammer and Driving System

Pile: PPSC - 24x24”; 610x610 mm;L = 80’ (24 m)

Soil: 10’ (3 m) Medium Clay 20’ (6 m) Stiff Silt30’ (9 m) Soft Clay30’ (9 m) Dense Sand

Water table: 15’ (4.5 m) below grade

Desired working load 150 tonsSafety Concept: Dynamic TestingExpected penetration 75’ (22.5 m)

Hammer: Find appropriate ECHBoth Hammer and Driving System

Pile: PPSC - 24x24”; 610x610 mm;L = 80’ (24 m)

Soil: 10’ (3 m) Medium Clay 20’ (6 m) Stiff Silt30’ (9 m) Soft Clay30’ (9 m) Dense Sand

Water table: 15’ (4.5 m) below grade

Desired working load 150 tonsSafety Concept: Dynamic TestingExpected penetration 75’ (22.5 m)

Steel Follower on Concrete Pile

Hammer: Up to 10 ton HydraulicHelmet/Hammer Cushion: see Tables

Follower: LF = 42.5’ - 12,800 mm18x2”-42’ - 450x50-12,650 mm pipe 18x18x6” - 500x500x150 mm plate

Pile Cushion:8” - 200 mm used plywood

Pile: PPC 20x20” LP = 50’500x500 mm LP = 15 m

Water Depth: 40’ - 12 mSoil Information: See CPT dataExpected pile penetration: LP = 43’ (13 m)Required working load: QD = 180 k (900 kN)

LC

Lp

Penetration

Water depth LF

LTLC

CPT data fileCPT data fileCPT data taken at xxx

Project: yyyyy

Depth (m) Tip Resistance (MN/m2) Sleeve Friction (MN/m2)

0.05 ‐0.08 0.0266 0.0%

0.1 5.73 0.0406 0.7%

0.15 17.37 0.0574 0.3%

0.2 13.19 0.0774 0.6%

0.25 11.73 0.1289 1.1%

0.3 9.79 0.1892 1.9%

0.35 7.06 0.2458 3.5%

0.4 4.45 0.248 5.6%

0.45 3.02 0.2052 6.8%

0.5 3.7 0.1558 4.2%

0.55 3.47 0.1801 5.2%

0.6 5.73 0.2192 3.8%

0.65 5.03 0.2397 4.8%

0.7 6.77 0.2507 3.7%

0.75 5.11 0.2658 5.2%

0.8 5.29 0.2532 4.8%

0.85 5.09 0.2424 4.8%

0.9 4.84 0.2156 4.5%

0.95 4.74 0.1811 3.8%

1 4.89 0.1596 3.3%

1.05 4.83 0.1498 3.1%

1.1 4.87 0.1324 2.7%

1.15 4.97 0.1052 2.1%

1.2 3.51 0.0971 2.8%

1.25 4.66 0.0891 1.9%

1.3 4.41 0.082 1.9%

1.35 4.36 0.0773 1.8%

1.4 4.49 0.0801 1.8%

1.45 5.37 0.0928 1.7%

Soil Types of CPTRobertson 1986

Soil Types of CPTRobertson 1986