CAPWAP AND REFINED WAVE EQUATION ANALYSES FOR DRIVEABILITY PREDICTIONS AND CAPACITY ASSESSMENT OF...
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Transcript of CAPWAP AND REFINED WAVE EQUATION ANALYSES FOR DRIVEABILITY PREDICTIONS AND CAPACITY ASSESSMENT OF...
CAPWAP AND
REFINED WAVE EQUATION
ANALYSES
FOR DRIVEABILITY PREDICTIONS AND
CAPACITY ASSESSMENT
OF OFFSHORE PILE INSTALLATIONS
OMAE 2009
Honolulu, HI - May 31 to June 5 2009
Frank Rausche, Matt Nagy, Scott Webster GRL Engineers, Inc.Liqun Liang Pile Dynamics, Inc.
Outline Background
PDA Testing and CAPWAP Bearing Graph and Driveability Variable Soil Setup and Plugging Effects
Problem Statement Procedures and Examples for
Blow Count Depth Matching (BCDM) Refined Wave Equation Analysis
(REWE) Summary
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
Dynamic pile testing and analysis Using Pile Driving Analyzer®
measure pile top velocity during pile installation; monitoring results include Stresses Integrity Hammer performance Capacity estimate
Perform signal matching with CAPWAP® to calculate capacity plus resistance distribution
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
CAPWAP (Signal Matching) Result
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
Wave equation analysis
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
Based on Smith’s concept Input requirement
Hammer properties Driving system details Pile geometry Soil information
GRLWEAP analysis options include Bearing Graph Driveability
GRLWEAP Bearing Graph
Wave equation analysis
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
GRLWEAP Driveability Output: Assumption: soil setup gain on shaft is function of log (time)
Problem Statement
We may do PDA/CAPWAP for one pile but need capacity assessment for others
Do Refined wave equation analysis (REWE)
We may have a driving record but no measurements and have to assess bearing capacity
Do Blow Count-Depth Matching (BCDM)
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
The REWE Procedure
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
REWE Example – Pile Details
1067 mm dia. OE pipe – 100 m long 3 pile sections Wall thickness: 34 – 44 mm Final penetration: 42 m Final blow count: 17 bl / 0.25 m
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
REWE Example – Soil Details
Alternate layers of Carbonate clays; Shear strength 100 to 450 kPa Silty, calcareous sands; med. dense to dense
Soils increasing in strength with depth
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
REWE Example - Hammer
Menck MHU 500T 294 kN ram weight 550 kJ maximum rated energy (1.87 m equiv. stroke) 500 kJ max. applied energy (1.70 m equiv. stroke)
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
Measurements
PDA Measurements 3.5 m below top of pile with 2 strain transducers and 2 PR accelerometers
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
REWE ExamplePDA - EOD Results
Transferred Energy (kJ) 473
Max. Top Stress (MPa) 224
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
REWE Example – EOD CAPWAP Results
Capacity Total/Toe (MN) 10.1/2.0
Damping Shaft/Toe (s/m) 0.5/1.3
Quake Shaft/ Toe (mm) 2.0/15
Blows/0.25 m 17
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
CAPWAP Analysis
Force and Velocity Measurements plus pile impedance
0 2000 4000 6000 8000 10000 120000.00
20.00
40.00
60.00
80.00
100.00
Load (kN)
Dis
pla
ce
me
nt
(mm
)
Pile Top
Bottom
Ru = 10137.5 kNRs = 8137.1 kNRb = 2000.4 kNDy = 52.4 mmDx = 67.1 mm
10 100
-15000.0
0.0
15000.0
30000.0
ms
kN
4 L/c
Force Msd
Velocity Msd
Pile
Calculated Load-Set Curve
Wave Equation Model
GRLWEAP Hammer Model Driving System as per contractor Pile Model with stabbing guides Soil model from CAPWAP
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
CAPWAP and GRLWEAP Input/Output Values
Quantity
Default/Measured/Computed
GRLWEAPFirst Trial
Damping Shaft/Toe (s/m) 0.5/1.3 0.5/1.3
Hammer Efficiency 0.95 0.95
Dr. System Stiffness (kN/mm)
N/A N/A
Dr. System CoR N/A N/A
Pile Top Stress (MPa) 224 243
Transferred Energy (kJ) 473 429
Blow Count (Blows/0.25 m) 17 23
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
CAPWAP and GRLWEAP Input/Output Values
Quantity
Default/Measured/Computed
GRLWEAPFirst Trial
GRLWEAPFinal
Damping Shaft/Toe (s/m) 0.5/1.3 0.5/1.3 0.4/1.0
Hammer Efficiency 0.95 0.95 1.0
Dr. System Stiffness (kN/mm)
N/A N/A 8,000
Dr. System CoR N/A N/A 0.93
Pile Top Stress (MPa) 224 243 225
Transferred Energy (kJ) 473 429 473
Blow Count (Blows/0.25 m) 17 23 17
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
Comparison of measured with GRLWEAP calculated force and
velocity
10 100
-15000.0
0.0
15000.0
30000.0
ms
kN
4 L/c
Force Msd
Velocity Msd
Pile
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
Second Procedure: BCDM
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
BCDM – Example properties as before
1st Step: Obtain driving log Blow count vs depth Hammers and Energy
settings Driving interruption
durations Maybe average of several
pile driving logs
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
Get fs vs depth from geotechnical report (starting value)
BCDM
BCDM
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
Get qt vs depth from geotechnical report (starting value)
Determine from driving log match Modified fs
Setup factor Modified qt
Effective toe area
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
BCDM – Blow Count match
Predict long term capacity from• modified fs,
• modified qt,
• setup factor• effective toe area
Summary
The bearing capacity of offshore piles can be assessed by the following methods: From measurements at EOD and CAPWAP
capacity at EOD Capacity at EOD From monitored restrikes plus CAPWAP
capacity including partial setup Capacity at BOR – may be extrapolated to later times
For similar non-monitored piles using REWE From driving record by BCDM
Extrapolated, estimated capacity from driving interruption information
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
Summary (continued)
REWE, the REfined Wave Equation analysis requires measurements and helps determine capacity for non-monitored piles driven in similar soils.
REWE requires matching of Transferred energy and top stress from PDA Blow count and CAPWAP capacity
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
Summary (continued)
BCDM, the blow count-depth matching procedure determines bearing capacity from driving behavior Generally applied to the complete driving log,
including energy and driving interruptions Driving interruption or restrike information
allows for soil setup assessment Without measurements results depend on
hammer performance assumptions
Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..
CAPWAP AND REFINED WAVE EQUATION ANALYSES FOR DRIVEABILITY PREDICTIONS AND CAPACITY ASSESSMENT OF OFFSHORE PILE INSTALLATIONS
Thank You, OMAE Conference
Rausche, Nagy, Webster, Liang