SEISMIC PERFORMANCES OF A LIQUEFIABLE SAND DEPOSIT USING 1-G SHAKE TABLE TESTING CONSIDERING AGING AND SHAKING HISTORY EFFECTS AND THE NUMERICAL SIMULATION OF SAND LIQUEFACTION

Restricted (Penn State Only)
Author:
Wang, Jintai
Graduate Program:
Civil Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
June 14, 2018
Committee Members:
  • Ming Xiao, Dissertation Advisor
  • Ming Xiao, Committee Chair
  • Patrick Joseph Fox, Committee Member
  • Tong Qiu, Committee Member
  • Shimin Liu, Outside Member
Keywords:
  • 1-G SHAKE TABLE TESTING
  • SHAKING HISTORY EFFECT
  • AGING EFFECT
  • CPTu TESTING
  • NUMERICAL SIMULATION
  • PM4Sand
  • LIQUEFACTION
Abstract:
Earthquake-induced liquefaction is a cause of substantial damage to geotechnical structures. The examples of liquefaction-induced damage include slope failures, foundation failures and flotation of buried structures. Underground structures embedded at shallow depths such as large underground parking garages, pipelines and manholes, can suffer significant uplift in liquefied soil. Understanding the seismic performance of a liquefiable ground during and after shaking is urgently needed. The main objectives of this research are to (1) investigate the seismic performance of a liquefiable sand deposit under a series of shaking events, (2) investigate the strength gain of the liquefied sand deposit using piezo-cone penetration (CPTu) testing, (3) simulate the shaking table testing using advanced constitutive model (PM4Sand) and understand the predictive performance of this model. A uniform liquefiable sand deposit was air-pluviated and fully saturated in a large laminar shear box (L×W×H: 2.29 m × 2.13 m × 1.83 m). The sand deposit was subjected to a liquefying shaking event (1st shaking) in the laminar box. Accelerometers and piezometers were embedded at different depths to capture the seismic response of liquefied sand. The measured excess pore pressures were used to verify the occurrence of liquefaction. LVDTs were attached to different frames of the laminar shear box to monitor the lateral displacements of the soil. The test recordings from piezometer, accelerometer and LVDT were presented and discussed. Another three major shaking events were designed and performed on the sand deposit after the first shaking. The shake table test results from different shaking events were compared to investigate the seismic response of the sand deposit under multiple shaking events. The time-dependent liquefaction resistance of a post-liquefaction sand deposit was studied using CPTu after 1st shaking event. A series of CPTu tests were conducted to measure the cone penetration resistance, friction resistance, and pore water pressure throughout the depth of the post-liquefaction sand deposit. To capture the sand aging effect after liquefaction, CPTu tests were done at different locations over a total elapsed time of 135 days. The results suggest that (1) the cone penetration resistance of the sand deposit decreased significantly immediately after liquefaction when compared with that before liquefaction; (2) the cone penetration resistance of the post-liquefaction sand deposit increased with time. The CPTu results were normalized with respect to effective overburden stress and the relationship between normalized CPTu results of the post-liquefaction sand deposit and time was proposed. To evaluate the predictive capabilities of the PM4Sand model, a numerical simulation of the shake table test was developed. The model was first calibrated using cyclic direct simple shear tests. The calibrated model was then used to simulate the seismic performance of the uniform soil deposit under sinusoidal seismic motions. Further insight into the strengths and limitations of the PM4Sand model gained from this research was presented.