Lateral Statnamic Load Testing of Large Diameter Drilled Shafts and Piers Deep Foundation Institute Bay Area Rapid Force Pulse Seminar Don Robertson, P.E. – Applied Foundation Testing

Lateral Set-up Instrumentation Concept of Lateral Statnamic Analysis Results Lateral Statnamic Load Testing of Large Diameter Drilled Shafts and Piers

Lateral Statnamic Load Testing Key Points Capable of Loads Ranging From less than 100 kips to Over 3000 kips Relatively Easy Setup – No Reaction Pile Required Long load pulse width provides a good model of ship impact, earthquake, and other extreme event loads Analysis method provides excellent correlation with static response Has been done simultaneously with liquefied soils Very flexible - Has been used on single drilled shafts, single piles, piers founded on pile groups, piers founded on drilled shafts, auger cast-in-place piles, and ship hull testing

Lateral Statnamic Setup Hemispherical Bearing LVDTs Reference Beam H Accelerometers Lateral Sled Strain Gages Foundation Downhole Accelerometers

Lateral Statnamic Setup Same Concept and Theory as Axial Reaction masses on sled (friction is used to stop sled) Hemispherical bearing between shaft and piston to transfer load without restraining the test rotation and to reduce eccentricity

Lateral Statnamic Setup

Instrumentation Load Cell Strain Gages LVDT opposite load point on ref. beam Accelerometer on ref. beam Accelerometers on shaft opp. Load point to measure lateral acceleration String of 8 Downhole accelerometers in inclinometer casing embedded in shaft or foundation element 2,000 samples/sec recorded for 3+ sec. (longer duration to measure any shaft oscillations)

Instrumentation

Instrumentation

Instrumentation

Instrumentation

Analysis…Lateral Double integration of Accel. and direct measurement of displacement from LVDT Measure Statnamic lateral load with Load Cell Back calculate LPILE model for design from initial soil parameters and adjusted to match observed load/deflection and deflection/depth response of shaft, pile or pier

Analysis…Lateral Model Shaft using single degree of freedom, model includes Non-linear static spring resistance Inertia of the shaft rotating about a hinge pt. Viscous Damping FStatnamic=Finertia+Fdamping+FStatic Finertia = inertial resistance from effective mass of foundation, includes some passive earth pressure wedge of surrounding soil Fdamping=effective viscous damping resistance Fstatic=effective static soil resistance

Results From Lateral Load Test

Results…Lateral Load Test Four Cycles of increasing load applied to shaft

Results…Lateral Load Test LVDT and integrated accelerometer data similar

Results…Lateral Load Test Effective mass in calculations only top 16’, shaft yielded in bending about 9 feet below grade

Results…Lateral Load Test Gage at 75’, clipped in tension, likely much higher

Results…Lateral Load Test Soil criteria used to model test condition in LPILE

Results…Lateral Load Test LPILE model yields much earlier than observed, conservative Otherwise model captures shaft behavior well within general range

Results of Load Test Program Use of Statnamic load testing results by the designers allow the reduction of significant amounts of the drilled shaft quantities for this project: 952 lf of drilled shaft excavation 634 Cubic yards of concrete Total project savings on the order of $230,000.00 Future projects will benefit from these test results Reduced quantities allowed for more efficient equipment setup during production drilled shaft installation (shorter holes = smaller equipment)

Results…Lateral Load Test Four Cycles of increasing load applied to shaft

Results…Lateral Load Test Top of shaft displacement

Results…Lateral Load Test Downhole acceleration and displacement

Results…Lateral Load Test Peak displacement for four load cycles

Results…Lateral Load Test Strain measurements for four load cycles

Results…Lateral Load Test Peak strain measurements for four load cycles

Results…Lateral Load Test Initial shaft stiffness

Results…Lateral Load Test

Results…Lateral Load Test

Results…Lateral Load Test

Results…Lateral Load Test

Questions???

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