Statnamic Pile Load Testing
Flip Hoefsloot, Fugro The Netherlands January 2010
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Load Testing Methods Description Statnamic Video of Test Application Interpretation Guidelines Conclusion
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STATIC HighHigh 100 % pressurepressure gas gas
Load Displacement STATNAMIC DYNAMIC 5-10% 1-2 %
Strain Load Acceleration Displacement
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A = Pile B = Load cell C = Cylinder D = Piston with chamber E = Platform F = Silencer 1 2 G = Reaction mass H = Gravel Container I = Gravel J = Laser K = Laser beam L = Laser sensor 3 4
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Clients Knowledge and experience Word wide Statnamic (Peter Middendorp)
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Hydraulic Catching Mechanism Containers filled with local material (gravel or equivalent) 4 test a day Simple inspection ignition system Transport on one trailer
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Equipment: 80 tons reaction mass 7 trailers for transport 2 to 3 days a test one cycle of testing
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Advantages: •Static behaviour •Separation of: •End Bearing •Shaft Friction
Disadvantages: •Cost •Selection of Test Piles
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Advantages: •Low Cost •Test on all Piles
Disadvantages: •Dynamic Pile-Soil behaviour •High stresses in Pile •Requires advanced analyzing Techniques •Applicable only for Steel Pipe Piles
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Advantages: Relatively low Cost Free selection of test Piles
Disadvantages: Difficult to determine Bearing Capacity Difficult to distinguish between End Bearing and Shaft Friction
Application: Re-use of existing Piles Load-Settlement behaviour
Condition: T Duration of rapid load Tf f 10 ≤ ≤1000 L pile length c stress wave velocity test pile L/cp p
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Fstn Fstn = statnamic force, measured Fst = static resistance u = displacement, measured M v = du/dt u a = d 2u/dt 2 F stn m = pile mass C = damping coefficient
m
k C
= + ⋅ + ⋅ Fstn (t) Fst (t) m a(t) C v(t)
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Time [ms] 0 50 100 150 200 250 300 20
15 Load Cell 10
Load[MN] 5
0
Time [ms]
0 50 100 150 200 250 300 0 10 20 30 Laser Sensor 40 Accelerometer 50 Displacement[mm] 60
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Load [MN] 0 5 10 15 20 0
10
20
30
40 Fstn(t) Displacement [mm] . Displacement[mm] 50 Fstatic(t) UP 60 = − ⋅ − ⋅ Fst (t) Fstn (t) m a(t) C v(t)
Estimated damping parameter C (hyperbolic curve)
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Dynamic Analysis, PLAXIS
Simplified input of dynamics boundary conditions with Microsoft notepad
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Dynamic Analysis, PLAXIS
Calibration model with static behaviour Average damping parameter selected based on hyperbolic curve
Statnamic Test Numerical Simulation PLAXIS
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Load [MN]
0 5 10 15 20 25 0 Extrapolation according to 20 Middendorp and Bakker
40
60 Correction for “rate effects”: 80 Undrained behaviour
Fy [kN/rad] 100 -5000 Undrained analysis 120 -4000 Displacement [mm] . Displacement[mm] -3000 “Rate effect ” 140
Fstn(t) -2000 160 Drained analysis Fu(t) -1000 180 Hyperbolic F=u/(p+q.u) 0 Hyperbolic F=Fref(u/uref)^0.5 0 0,05 0,10 0,15 0,20 200 |U| [m]
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Bochum, Pfahl 57 STN Cyclic Load Displacement Diagram 0 Cycle 1 Cycle 2 Cycle 3
5 Bochum, Pfahl 57 STN Static Cyclic Load Displacement Diagram Cycle 1 Cycle 2 Cycle 3 Hyp. Appr. Static Quick 10 0 Hyp. Appr. Static Long Term
15 5
Displacement [mm] 20 10
25 15
30 Displacement [mm] [mm] Displacement 20 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Load [MN]
25
30 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Load [MN]
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The Netherlands
CUR-comittee H410 “Rapid load tests” goal: preparation European Codes Fugro is member (Maarten Profittlich)
European Codes
Draft standard Rapid Load Testing procedure Working group 4 of TC 341 (Testing of geotechnical structures; Testing of piles: rapid load testing (reference EN-ISO 22477-# version: 3.3, 23 April 2008)
Guideline on the interpretation of Rapid Load test on piles 7 November 2008
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Statnamic provides alternative in case
Static load tests are not feasible
Re-use of existing Piles
Determine Load-Settlement behaviour
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