THE EFFECTS OF IRREGULAR PRE-LIQUEFACTION LOADING AND PARTICLE ANGULARITY ON POST-LIQUEFACTION RESPONSE
Aqshems Meten Nichols, Wing Shun Kwan, Chadi El Mohtar.
The University of Texas at Austin, Austin, TX.
Liquefaction of saturated sand is recognized as a devastating hazard. It is important to assess the characteristics of liquefied soil, which is a topic that hasn’t been comprehensively explored. In current practice, the shear strength of liquefied soil is usually crudely correlated with SPT or CPT indices, for which conservatism is often incorporated. In this study, the investigation of liquefied soil is conducted by monotonic loading following cyclic loading in a triaxial testing setup. The results show that the stress-strain curve has a low stiffness region preceding the dilative response region, which concurs with the existing literature. The testing program encompasses 2 factors that affect the post-liquefaction soil response: 1) preliquefaction loading history, and 2) the sand particle roundness. Three types of loading motion (uniform, taper up, and taper down) were applied to reconstituted loose sand specimens to initiate liquefaction, and monotonic loading was applied thereafter. Two types of sand were used, one with well-rounded particles and one with angular particles. Recent studies in this topic are limited to harmonic motion only. The taper motions are more representative of actual transient ground motions in which the dominant pulses occur during the early or later loading phases. The testing results exhibit that the transition of low stiffness to a dilative response is correlated with the history of pre-liquefaction loading and sand particle roundness. A better knowledge of the stress-strain behaviors in liquefied soil can improve the engineering assessment of geohazards, such as the induced displacement of soil particles during an earthquake.