1.1 grlweap - gray
-
Upload
cfpbolivia -
Category
Engineering
-
view
283 -
download
2
Transcript of 1.1 grlweap - gray
GRLWEAP - Santa Cruz, 20151
Congreso Internacional de Fundaciones Profundas de Bolivia
Santa Cruz, Bolivia, 12 al 15 de Mayo de 2015
Day 1: Software DemonstrationsFrank Rausche, Ph.D., P.E., D.GE - Pile Dynamics, Inc.
Applications of Stress Wave Theory to Deep Foundations with an Emphasis on
“The Wave Equation”(GRLWEAP)
GRLWEAP - Santa Cruz, 20152
CONTENTCONTENT
• Introduction– Dynamic Formula
– Static Formula
• The One‐Dimensional Wave Equation and Wave Demonstrations
• Wave Equation Models
• Bearing Graph and Driveability
• Example
• Conclusions
GRLWEAP - Santa Cruz, 20154
WAVE EQUATION OBJECTIVESWAVE EQUATION OBJECTIVES
Smith’s Basic Interest:
– Allow for realistic stress calculations– Replace Unreliable Energy Formulas– Use improved models
• elastic pile• elasto‐plastic static resistance• viscous dynamic (damping) resistance • detailed driving system representation
GRLWEAP - Santa Cruz, 20155
Wave Demonstrations
– Slinky
– Pendulum
– Buddies
– Shear Waves
– Compressive Waves
GRLWEAP - Santa Cruz, 20156
Animation courtesy of Dr. Dan Russell, Kettering Univ.
http://paws.kettering.edu/~drussell/demos.html
WAVES
Example of a Baseball Wave
GRLWEAP - Santa Cruz, 20157
Animation courtesy of Dr. Dan Russell, Kettering Univ.
Example of a Shear Wave
GRLWEAP - Santa Cruz, 20158
Animation courtesy of Dr. Dan Russell, Kettering Univ.
Example of a Compressive Wave
GRLWEAP - Santa Cruz, 20159
The 1-D Wave Equation
ρ(δ2u/ δt2) = E (δ2u/ δx2)E … elastic modulus
ρ … mass density
with c2 = E/ ρ ... Wave Speed
Solution: u = f(x‐ct) + g(x+ct)
x … length coordinate
t ... time
u … displacement
f
gx
GRLWEAP - Santa Cruz, 201510
x
Timet
The compression wave,induced by the
hammer at the pile top, moves downward a
distance c t during the time interval t.
Waves in a PileWaves in a Pile
GRLWEAP - Santa Cruz, 201511
x
Timet t + t
C t
The compression wave, induced by the hammer at the pile top, moves
downward a distance c t during the time
interval t.
Waves in a PileWaves in a Pile
GRLWEAP - Santa Cruz, 201512
The compression wave, arrives at the pile toe where it
is reflected(on a free pile in tension).
t Time t + t Waves in a Pile
GRLWEAP - Santa Cruz, 201513
2012 13 Wave Mechanics for Pile Testers
x
u
ρ(δ2u/ δt2) = E (δ2u/ δx2)
E … elastic modulus
ρ … mass density
with c2 = E/ ρ … Wave Speed
x … length coordinate t ... time
u … displacement
THE Wave Equation
Solution: u = f(x-ct) + g(x+ct)
GRLWEAP - Santa Cruz, 201514
2012 14 Wave Mechanics for Pile Testers
f
g
x
f
g
x
C t
C t
Timet + t
Timet
The Solution to the Wave Equationu = f(x-ct) + g(x+ct)
GRLWEAP - Santa Cruz, 201515
Force, F – Time to + t
Point A
Point A, like all other points along the pile, is at rest at time to (when
contact between ram and pile top occurs)
Compressed distance, L
Time to
u
The first instant after impact
GRLWEAP - Santa Cruz, 201516
∆u is the displacement of a point of pile during time ∆t
F
∆L
Wave travels distance ∆L = c ∆t during time ∆t
Particle Velocity, v = ∆u/ ∆t but ∆u = ε ∆L and therefore v = ε ∆L / ∆t and with wave speed c = ∆L / ∆t:
∆u
Force Velocity ProportionalityForce Velocity Proportionality
v = ε c
GRLWEAP - Santa Cruz, 201517
This is the strain, stress, force-velocity proportionality
Z = EA/c is the pile impedance (kN/m/s)
This is the strain, stress, force-velocity proportionality
Z = EA/c is the pile impedance (kN/m/s)
Fd = vd (EA/c)Fd = vd (EA/c)
d = vd(E/c)d = vd(E/c)εd = vd / cεd = vd / c
Strain-Stress-Force ProportionalityWave travels in one direction only
Strain-Stress-Force ProportionalityWave travels in one direction only
GRLWEAP - Santa Cruz, 201518
Express Your ImpedanceExpress Your Impedance
Z = EA/c kN/(m/s)
with c = (E/ρ)1/2 Z = A (E ρ)1/2
with E = c2 ρ Z = A c ρ
with Mp= L A ρ Z = Mp c/ L (Mp ... pile mass)
The Pile Impedance is a force which changes the pile velocity suddenly by 1 m/s.
Reversely, if the velocity changes by 1 m/s then pile will develop a force equal to Z.
GRLWEAP - Santa Cruz, 201519
A Quick Look at Energy FormulasA Quick Look at Energy 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
Engineering News: Rallow = Wr h / 6(s + 0.1)
GRLWEAP - Santa Cruz, 201520
The Gates Formula The Gates Formula
Ru = 7 (Wrh)½ log(10Blows/25 mm) ‐ 550
Ru … Nominal Resistance (kN)
Wr… ram weight (kN)
h … actual stroke (m)
log … logarithm to base 10
GRLWEAP - Santa Cruz, 201521
The Hiley Formulausing Set-Rebound Measurements
The Hiley Formulausing Set-Rebound Measurements
Ru = ηWr h (Wr+ e2 WP)
(s + c/2) (Wr + WP)
Rebound: c
Set = s
Considers combined pile‐soil elasticity effectUsually with F.S. = 3; η = hammer efficiency.
GRLWEAP - Santa Cruz, 201522
Bearing Graphs from 2 Energy FormulasHammer D 19-42; Er = 59 kJ
Bearing Graphs from 2 Energy FormulasHammer D 19-42; Er = 59 kJ
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
GRLWEAP - Santa Cruz, 201523
Shortcomings of FormulasShortcomings of Formulas
• Rigid pile model
• Poor hammer representation
• Inherently inaccurate for both capacity and blow count predictions
• No stress results
• Unknown hammer energy
• Relies on EOD Blow Counts
GRLWEAP - Santa Cruz, 201524
Static FormulasStatic Formulas
• Based on Soil Properties
• Always done for any deep foundation type
• Backed up by Static or Dynamic Testing
GRLWEAP - Santa Cruz, 201525
Static Analysis to Calculate LTSR
Basically for All Soil Types:
Ru = Ru,shaft + Ru,toeRu = fsAs + qt At
fs, Ru,shaft, As … Shaft Resistance/Area
qt, Ru,toe, At … End Bearing/Area
GRLWEAP - Santa Cruz, 201526
The β-Method for Cohesionless Soils
• Ru,shaft = fs As
– fs = ko tan(δ) popo is the effective overburden pressure
ko is some earth pressure coefficient
– β = ko tan(δ)
• Ru,toe = Nt po AtNt is a bearing capacity factor
All with Certain Limits
GRLWEAP - Santa Cruz, 201527
The α-Method for Cohesive Soils
• Ru,shaft = fs As
– fs = α c
c is the undrained shear strength
α is a function of po• Ru,toe = 9 c At
..... with certain limits
GRLWEAP provides 4 different static analysis methods
ST – based on Soil Type; SA‐ based on SPT‐N; CPT; API
GRLWEAP - Santa Cruz, 201528
GRLWEAP: ST MethodNon-Cohesive Soils (after Bowles)
Soil Parameters in ST Analysis for Granular Soil Types
Soil Type SPT NFriction Angle
Unit Weight, γ β Nt Limit (kPa)
degrees kN/m3 Qs Qt
Very loose 2 25 - 30 13.5 0.203 12.1 24 2400
Loose 7 27 - 32 16 0.242 18.1 48 4800
Medium 20 30 - 35 18.5 0.313 33.2 72 7200
Dense 40 35 - 40 19.5 0.483 86.0 96 9600
Very Dense 50+ 38 - 43 22 0.627 147.0 192 19000
GRLWEAP - Santa Cruz, 201529
ST - INPUTST - INPUT
GRLWEAP - Santa Cruz, 201530
GRLWEAP: ST MethodCohesive Soils (after Bowles)
Soil Parameters in ST Analysis for Cohesive Soil Types
Soil Type SPT NUnconfined Compr.
StrengthUnit Weight γ Qs Qt
kPa kN/m3 kPa kPa
Very soft 1 12 17.5 3.5 54
Soft 3 36 17.5 10.5 162
Medium 6 72 18.5 19 324
Stiff 12 144 20.5 38.5 648
Very stiff 24 288 20.5 63.5 1296
hard 32+ 384+ 19 – 22 77 1728
GRLWEAP - Santa Cruz, 201531
ST - INPUTST - INPUT
GRLWEAP - Santa Cruz, 201532
The Wave Equation ModelThe Wave Equation Model
• The Wave Equation Analysis calculates– The displacement of any point along a slender, elastic rod at any time durting and after impact
– From the displacements forces, stresses, velocities
• The calculation is based on rod properties: – Length
– Cross Sectional Area
– Elastic Modulus
– Mass density
GRLWEAP - Santa Cruz, 201533
The Wave Equation ModelThe Wave Equation Model
• The Wave Equation Analysis calculates– The displacement of any point along a slender, elastic rod at any time durting and after impact
– From the displacements forces, stresses, velocities
• The calculation is based on rod properties: – Length
– Cross Sectional Area
– Elastic Modulus
– Mass density
GRLWEAP - Santa Cruz, 201534
GRLWEAP FundamentalsGRLWEAP Fundamentals
• For a pile driving analysis, the “slender, elastic rod” consists of Hammer+DrivingSystem+Pile
• The soil is represented by resistance forces acting on the pile and representing the forces in the pile‐soil interface
Ham
mer
D.S.
Pile
GRLWEAP - Santa Cruz, 201535
Smith’s Numerical Solution of the Wave EquationSmith’s Numerical Solution of the Wave Equation
∆L
ρ(δ2u/ δt2) = E (δ2u/ δx2)E … elastic modulus ‐ ρ … mass densitywith c2 = E/ ρ ... Wave Speed
Closed Form Solutions to the wave equation are not practical; we therefore solve the equation numerically:
(mi/ki)(ui,j+1 ‐2ui,j + ui,j‐1)/Δt2
= (ui+1,j – 2ui,j + ui‐1,j)
This is equivalent to considering mass points and springs!
ii+1
i-1
GRLWEAP - Santa Cruz, 201536
The GRLWEAP Pile ModelThe GRLWEAP Pile Model
Each segment has a mass and spring stiffness
– of length ∆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 which allow us to solve the wave equation numerically.
∆L
GRLWEAP - Santa Cruz, 201537
The Pile ModelThe Pile Model
Relationship between the uniform pile and the
lumped mass model properties:
m k = (ρ A ∆L)(EA/∆L) = A2Eρ = Z2 [kN s/m]2
m/k = (ρ A ∆L)/(EA/∆L) = (ρ/E)∆L2 = (∆L/c)2 [s]2
Or
Z = (mk)1/2 (pile impedance) and
∆t = (m/k)1/2 (wave travel time)
Note: the smaller ∆L, the smaller ∆L and that means the higher the frequencies that can be
represented.
∆L
GRLWEAP - Santa Cruz, 201540
We can model 3 hammer-pile systemsWe can model 3 hammer-pile systems
GRLWEAP - Santa Cruz, 201541
Ram: A, L for stiffness, mass
Cylinder and upper frame = assembly top mass
Drop height
External Combustion Hammer Modeling
Ram guides for assembly stiffness
Hammer base = assembly bottom mass
GRLWEAP - Santa Cruz, 201542
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
GRLWEAP - Santa Cruz, 201543
External Combustion HammersRam Model
Ram segments ~1m long
Combined Ram‐H.Cushion
Helmet mass
GRLWEAP - Santa Cruz, 201544
External Combustion HammersAssembly model
External Combustion HammersAssembly model
Assembly segments, typically 2
Helmet mass
GRLWEAP - Santa Cruz, 201545
External Combustion HammersCombined Ram Assembly Model
External Combustion HammersCombined Ram Assembly Model
Combined Ram-H.Cushion
Helmet mass
Ram segments
Assembly segments
GRLWEAP - Santa Cruz, 201546
External Combustion HammerAnalysis Procedure
• 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 g
g is the gravitational acceleration
h is the equivalent hammer stroke and η is the hammer efficiency
h = Hammer potential energy/ Ram weight
GRLWEAP - Santa Cruz, 201547
• 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
External Combustion HammerAnalysis Procedure
GRLWEAP - Santa Cruz, 201548
Diesel HammersDiesel Hammers
• Very popular in the US
• Have their own fuel tank
and combustion “engine”
• Model therefore includes a
thermodynamic analysis
• Stroke is computed
GRLWEAP - Santa Cruz, 201558
GRLWEAP hammer efficienciesηh = Ek/EP
GRLWEAP hammer efficienciesηh = 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 - Santa Cruz, 201560
WR
h
ER = WR hManufacturer’s Rating
WR
Max ET = ∫F(t) v(t) dt(EMX, ENTHRU)
ηT = ENTHRU/ ER(transfer ratio or efficiency) Measure:
Force, F(t)Velocity, v(t)
Measured Transferred Energy
Measured Transferred Energy
GRLWEAP - Santa Cruz, 201562
Measured Transfer Ratios for DieselsSteel Piles Concrete Piles
GRLWEAP - Santa Cruz, 201563
For all impact hammers GRLWEAP needs impact velocity
WP
mR
hEr = Wr he = mr g he
he = Er / Wr he – equivalent stroke
he = h for single acting hammers
Epr = η Er Wr he (η = Hammer efficiency )
WRvi
Ek = Epr = ηh (½ mr vi2) (kinetic energy)
vi = 2g heηh
GRLWEAP - Santa Cruz, 201564
GRLWEAP Diesel hammer efficiencies , ηh
GRLWEAP Diesel hammer efficiencies , ηh
Open end diesel hammers: 0.80uncertainty of fall height, friction, alignment
Closed end diesel hammers: 0.80uncertainty of fall height, friction, power assist, alignment
GRLWEAP - Santa Cruz, 201565
Modern Hydraulic Hammer Efficiencies, ηh
Modern Hydraulic Hammer Efficiencies, ηh
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
GRLWEAP - Santa Cruz, 201568
Vibratory HammersVibratory Hammers
GRLWEAP - Santa Cruz, 201569
Vibratory Force:
FV = me [ω2resin ω t ‐ a2(t)]
FL
FV
m1
m2
• Line Force
• Bias Mass and
• Oscillator mass, m2
• Eccentric masses, me, radii, re
• Clamp
Vibratory Hammer ModelVibratory Hammer Model
GRLWEAP - Santa Cruz, 201571
The Driving Systems Consists of1. Helmet including inserts to
align hammer and pile
2. Optionally: Hammer Cushion to protect hammer
3. For Concrete Piles: Softwood Cushion
Driving System ModelsDriving System Models
GRLWEAP - Santa Cruz, 201572
Helmet + Inserts
Driving System ModelExample of a diesel hammer
on a concrete piles
Driving System ModelExample of a diesel hammer
on a concrete piles
Hammer Cushion: Spring plus Dashpot
Pile Top: Spring + DashpotPile Cushion
GRLWEAP - Santa Cruz, 201575
Interface Soil: Elasto‐Plastic Springs and Viscous Dashpots
Soil outside of interface: Rigid
The Soil Model After Smith
GRLWEAP - Santa Cruz, 201576
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 (SRD) differs from the soil resistance under static loads
GRLWEAP - Santa Cruz, 201577
Segment
i
Segment
i‐1
Segment
i+1
Pile‐Soil Interface
Soil Model ParametersSoil Model Parameters
ki,Rui
Ji
RIGID SOIL
ki+1,Rui+1
Ji+1
ki-1,Rui-1
Ji-1
GRLWEAP - Santa Cruz, 201578
FixedSoil
Smith’s Soil ModelSmith’s Soil Model
Total Soil ResistanceRtotal = Rsi +Rdi
Total Soil ResistanceRtotal = Rsi +Rdi
Displacement uiVelocity vi
Pile
Segment i
GRLWEAP - Santa Cruz, 201579
The Static Soil ModelThe Static Soil Model
Displacement uiVelocity vi
Pile
Segment i
Pile Displacement
Rui
Static Resistance
Rui … ult. resistanceqi … quake
ksi = Rui /qi
GRLWEAP - Santa Cruz, 201582
Recommended Toe Quakes, qtoeRecommended Toe Quakes, qtoe
0.1” or 2.5 mm forall soil types0.04” or 1 mm for hard rock
qtoe
Static Toe Res.
qtoe Ru,toe
Toe Displacement
D/120 for very dense or hard soilsD/60 for soils which are not very dense or v. hard
Displacement pilesNon‐displacement piles
D
GRLWEAP - Santa Cruz, 201583
Toe Quake Effect on Blow Count Toe Quake Effect on Blow Count
S200
10
0 m
61
0x
12
95
m
Approximatelyy 50% Shaft Resistance
Total No. of Blows: ∞ (qt =D/60); 27,490 (qt=D/120)
0
10
20
30
40
50
60
70
80
90
100
0 200 400 600 800
Dep
th o
f P
ile T
oe
Pen
etra
tio
n -
m
Blow Count - Blows/m
qt = D/60
qt = D/120
GRLWEAP - Santa Cruz, 201584
The Dynamic Soil ModelThe Dynamic Soil Model
Displacement uiVelocity vi
Pile
Segment i
Rd = RuJsv vSmith‐viscous
damping factor,Jsv [s/m or s/ft]
For RSA and Vibratory Analysis
Smith damping factor,
Js [s/m or s/ft]
Rd = RsJs v
Standard
GRLWEAP - Santa Cruz, 201585
Recommended Smith damping factors(Js or Jsv)
Recommended Smith damping factors(Js or Jsv)
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 - Santa Cruz, 201586
Shaft Damping on Blow Count Shaft Damping on Blow Count
S200
10
0 m
61
0x
12
95
m
Approximatelyy 50% Shaft Resistance
Total No. of Blows: ∞ (Js=0.65 s/m); 27,490 (Js=0.16 s/m)
0
10
20
30
40
50
60
70
80
90
100
0 200 400 600 800
Dep
th o
f P
ile T
oe
Pen
etra
tio
n -
m
Blow Count - Blows/m
Js = 0.65 s/m
Js = 0.16 s/m
GRLWEAP - Santa Cruz, 201588
GRLWEAP’s Static Analysis MethodsGRLWEAP’s Static Analysis Methods
Rs
Rt
QIcon 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.
GRLWEAP - Santa Cruz, 201589
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
GRLWEAP - Santa Cruz, 201592
Resistance DistributionResistance Distribution3. More Involved:
I. ST Input: Soil Type
II. SA Input: SPT Blow Count, Friction Angle or Unconfined Compressive Strength
III. API (offshore wave version) Input: Friction Angle or UndrainedShear Strength
IV. CPT Input: Cone Record including Tip Resistance and Sleeve Friction vs Depth.
Pen
etra
tio
n
All are good for a Bearing GraphII, III and IV OK for Driveability Analysis
Local experience may provide better values
GRLWEAP - Santa Cruz, 201594
Mass i
Mass i-1
Mass i+1
Numerical TreatmentNumerical Treatment• Predict displacements:
uni = uoi + voi ∆t
Fi, ci
uni-1
uni
uni+1
Ri-1
Ri
Ri+1
• Calculate spring compression:
ci = uni - uni-1
• Calculate spring forces:
Fi = ki ci
• Calculate resistance forces:
Ri = Rsi + Rdi
GRLWEAP - Santa Cruz, 201595
Force balance at a segmentForce balance at a segment
Acceleration: ai = (Fi + Wi– Ri – Fi+1) / mi
Velocity, vi, and Displacement, ui, from Integration
Mass i
Force from upper spring, Fi
Force from lower spring, Fi+1
Resistance force, Ri Weight, Wi
GRLWEAP - Santa Cruz, 201597
Set or Blow Count Calculation (a) Simplified: extrapolated toe displacement
Set or Blow Count Calculation (a) Simplified: extrapolated toe displacement
Static soil Resistance
PileDisplacement
Final Set
Max. Displacement
Quake
Ru
Extrapolated
Calculated
GRLWEAP - Santa Cruz, 2015100
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
GRLWEAP - Santa Cruz, 2015101
RSA Effect on Blow Count RSA Effect on Blow Count
S500
10
0 m
12
20
x2
5
0
10
20
30
40
50
60
70
80
90
100
0 200 400 600 800
Dep
th o
f P
ile
To
e P
enet
rati
on
-m
Blow Count - Blows/m
Standard
RSA
95
m
Total No. of Blows: 8907 (Standard); 6235 (RSA)
GRLWEAP - Santa Cruz, 2015103
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
GRLWEAP - Santa Cruz, 2015104
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;
GRLWEAP - Santa Cruz, 2015107
Driveability AnalysisDriveability Analysis
• Analyze a series of Bearing Graphs for different depths for SRD and/or LTSR
• Put the results in sequence so that we get predicted blow count and stresses vs pile toe penetration
• Note that, in many or most cases, shaft resistance is lower during driving (soil setup) and end bearing is about the same as long term
• In the few cases of relaxation, the toe resistance is actually higher during driving than long term
GRLWEAP - Santa Cruz, 2015108
Analysis
Program Flow – DriveabilityProgram Flow – Driveability
Model Hammer &Driving System
Choose first Depth to analyze
Next G/L
Pile Length and Model
Calculate Rufor first gain/loss
Output IncreaseDepth?
Increase Depth
Input
IncreaseG/L?
N
N
Y
Y
GRLWEAP - Santa Cruz, 2015109
Driveability Result
During a driving interruption soil setup occurs
GRLWEAP - Santa Cruz, 2015110
When Should we do the Analysis?When Should we do the Analysis?
• Before pile driving begins
– Equipment selection for safe and efficient installation
– Preliminary driving criterion
• After initial pile tests have been done
– Refined Wave Equation analysis for improved driving criterion
– For different driving systems
• In preparation of dynamic testing
GRLWEAP - Santa Cruz, 2015111
SummarySummary• The wave equation analysis simulates what happens in the pile when it is struck by a heavy hammer input.
• It calculates a relationship between capacity and blow count, or blow count vs. depth.
• The analysis model represents hammer (3 types), driving system (cushions, helmet), pile (concrete, steel, timber) and soil (at the pile‐soil interface)
• GRLWEAP provides a variety of input help features (hammer and driving system data, static formulas among others).
GRLWEAP - Santa Cruz, 2015112
An example for a Dynamic Test Preparation
An example for a Dynamic Test Preparation
• Prepare dynamic test on a 400 mm dia. pile with Expander Body of 600 mm diameter and 2000 mm length.
• Sand and Gravel
• Drop Weights 5 and 8 tons
• Drop Height 1.2 m
• Cushion 100 mm
GRLWEAP - Santa Cruz, 2015113
Ananlysis of a Pile with Expander BodyAnanlysis of a Pile with Expander Body
GRLWEAP - Santa Cruz, 2015114
Analysis resultsHammers 1 m drop height, 9 inch cushioin
Analysis resultsHammers 1 m drop height, 9 inch cushioin
GRLWEAP - Santa Cruz, 2015115
Thank you for your attention!
QUESTIONS?
Thank you for your attention!
QUESTIONS?