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Experimental and Micromechanical Computational Study of Pile Foundations Subjected to Liquefaction-Induced Lateral Spreading - Task 1 (1g Tests)S. Thevanayagam, UBResearch Progress – Year 1Feb. 12, 2007, 2-4 pm; UB-VTCPI: R. Dobry, co-PI’s: A. Elgamal, S. Thevanayagam, T. Abdoun, M. ZeghalUB-NEES Lab: A. Reinhorn, M. Pitman, J. Hanley, SEESL-StaffTulane: Usama El ShamyStudents & Staff: UB (N. Ecemis, B. Raghudeep, Q. Chen) and RPI (J. Ubilla, M. Gonzalez, V. Bennett, C. Medina, Hassan, Inthuorn)
Agenda • Level Ground Liquefaction Test – LG-0 • Test Name (correction – Test in Nov.06 was LG-0; No LG-1 test done) • Instrumentation & Specimen Preparation • Sensor data Interpretation • Draft Results – Discussion • Report Preparation Status – Test LG-0 • Rough Draft completed • Final - Due April 1, 07 • Schedule & Budget Status – Year 2 • Sloping Ground, Single Pile, Group Pile
Test LG-0 • Objectives • Actuator Controls (X, Y & Rotation) • Sand Pumping (Target Dr ~40-50%) • Feasibility of Inducing Liquefaction • Safety Checks • Instrumentation placement & operational Checks • Instrumentation • Accelerometers (33 on rings, 8 inside soil, --- on Shaking Base) • ShapeAccel Array (4 arrays, 3x24 sensors/array) • Piezometers (15) • Potentiometers (18 on rings, 3 on ground surface) • Video (4)
LG-0 Sensor Names & Locations East – Reaction Wall & Actuators; PO-Potentiometer; PW – Piezometer; S – Accelerometer in soil; L – Accelerometer on ring; B – accelerometer on shaking base; Red triangle – Shape Accel Array
LG-0 Bucket Density Data • Water Depth Varied slightly ~ 1 to 2.5 ft (tighter control needed in future) • Nearly Consistent slurry • Slurry Discharge through a Horizontal Diffuser • Delivery Pipe - Vertical inside sand box & Moved Horizontally by crane to spread the discharged sand • About 4 Days to Fill about 5m sand
CPT Testing Read-out Box Electrical standard friction cone: Tip area= 15cm2 Friction sleeve area=200 cm2 The CPT tip resistance and side friction data recorded at 4” depth intervals during penetration.
Reference & Feedback Actuator Accelerations a4 a3 a2 a1 Reference Acceleration a1=0.01 g (5 sec) a2=0.05 g (10 sec) a3=0.15 g (10 sec) a4=0.3 g (10 sec) Feedback Acceleration
Differential Force in Actuators Actuators 1 and 2 appear to lag one another; May need fine tuning….. But, this fine tuning may wait….
Sample Results X&Y Accel. (on Ring and Soil) (Total soil Depth=16ft) @ EL. 4 ft, 8.5ft, 12.5ft and 16ft X&Y Accel. (on Ring) Variation of PGA with depth at different time zones on ring X&Y Accel. (on Base Plate) ay/ax at different time zones 4 PPT’s PW13 (@ EL. 2.5 ft) PW14(@ 7.5 ft) PW15(@ 12 ft) PW3(@ 14 ft) ShapeAccelArray (SAA40019_12_21) Stress-Strain Curve Stress-Time Strain-Time 3 Potentiometers (@ top of soil; EL.16 ft) PO1 PO2 PO3
Acceleration of soil and ring 5 @ EL. 4ft Data obtained from Pacific DAQ (time lag ~2.5s? – This will be resolved before VTC meeting on 12th)
Acceleration of soil and ring 5 @ EL. 4ft Data obtained from Pacific DAQ (time lag ~2.5s?) Data obtained from SAA 40019_12_21 (Vertex 1) (time lag ~ 4s?)
Acceleration of soil and ring 10 @ 8.5ft Data obtained from Pacific DAQ Data obtained from SAA 40019_12_21 (Vertex 6)
Acceleration of soil and ring 16 @ 12.5ft Data obtained from Pacific DAQ Data obtained from SAA 40019_12_21 (Vertex 10)
Acceleration of soil and ring @ 16ft Data obtained from Pacific DAQ Data obtained from SAA 40019_12_21 (Vertex 13)
LG-0 Accelerometer Data • The accelerometers in the soil and SAA starts to differ from Ring accelerometers just a few seconds after strong base shaking at 0.05g • Are ring accelerometers more stable/reliable after liquefaction?
Variation of PGA with depth at different time zones on Ring Data obtained from accelerometers on ring.
Lateral Accelerometer Response Very small lateral acceleration
Recorded Base Ground Motion Base Plate X&Y-Accelerometers Sample Results
X- and Y- Accelerations at Base Recorded Base Ground Motion
Recorded Base Ground Motion Ratio of Base Y-acc to X-acc in different time zones
X- and Y- Accelerations at Ring 10 @ EL8.5ft Recorded Ring Motion
Recorded Ring Motion Ratio of Ring Y-acc to X-acc in different time zones @ EL. 4, 8.5 & 13.5 ft
Pore Pressure Transducer @ depth 2.5 ft PW13 Need depth/pore pressure corrections at shallow depths
Pore Water Pressure Ratio Need depth/pore pressure corrections at shallow depths
Stress-Strain Curve (Draft) SAA 40019_12_21 Data @ EL. 3.5 ft Stress-strain data unreliable after liquefaction
Stress-Strain Curve (Draft) SAA 40019_12_21 Data @ EL. 8.5 ft Stress-strain data unreliable after liquefaction
Stress-Strain Curve (Draft) SAA 40019_12_21 Data @ EL.12.5 ft Stress-strain data unreliable after liquefaction
3D Data Viewer (nees.rpi.edu/3dviewer) Not yet utilized Potentiometers – Lateral Not yet analyzed
Draft Findings - Summary • Actuator Controls (X, Y & Rotation) – Appears to be working with very little lateral shaking • Sand Pumping (Target Dr ~40-50%) – Feasible (but care necessary) • Feasibility of Inducing Liquefaction – Feasible (liquefies at very small shaking intensity…due to loose…sand) • Safety Checks – Level ground ok, but…sloping ground needs more care…. • Instrumentation placement & operational Checks – instruments function well; time-synchronizing…need to check and make sure; accelerometers inside soil disorients and SAA behaves different from sand after liquefaction
Yr-2 Test Schedule & Budget 1. Laminar Box Adaptations & Improvements- January 4 – March 28, 2007 (detail schedule given in next slides)2. SG-1 & Pile Tests- April 1 – December 5, 2007 (detail schedule given in next slides)
