An Improved CRR-Vs1 Characterization Model for Sand-Like Gravelly Soils Validated by Dynamic Centrifuge Tests

Abstract

Liquefaction of natural deposited sand-like gravelly soils has been widely reported in past earthquakes. Assessing the liquefaction resistance (CRR) of sand-like gravelly soils in a cost-effective and reliable way raises a challenge for geotechnical engineers. Although the overburden stress-corrected shear wave velocity (Vs1)-based liquefaction evaluation methods are well established for sands, they are not applicable to gravelly soils because the gravel content’s effect will lead to an overestimation of soil liquefaction resistance. Based on the previously proposed improved CRR-Vs1 characterization model for sand–gravel binary mixtures, both soil element tests and centrifuge model tests were performed in this study to validate the performance of the proposed model. First, cyclic triaxial tests were carried out to obtain the key parameters for establishing the improved characterization model. Then dynamic centrifuge tests on level model grounds of the sand and two types of sand-like gravelly soils with a gravel content of 20% and 60% were conducted to check the efficacy of the proposed model. The test results show that the developed CRR-Vs1 curves for sand-like gravelly soils tend to shift to the right with increasing gravel content, and these curves can accurately classify the liquefied and non-liquefied case history data sets generated from the dynamic centrifuge tests. Besides, the validation results suggest that the improved characterization model could provide a promising way to efficiently evaluate the liquefaction resistance of sand-like gravelly soils with various gravel contents on a regional scale for engineering practice, which only requires a few soil element tests of both the sand and a type of sand-like gravelly soil with a given gravel content. The existing liquefaction triggering curves are usually established for sands, which might overestimate the liquefaction resistance of gravelly soils. It is unsafe to directly apply the current liquefaction discrimination methods for sands to gravelly soils. To move toward a cost-effective and reliable liquefaction assessment of gravelly soils, the authors proposed an improved characterization model of liquefaction resistance by shear wave velocity for gravelly soils, which treats the gravel content as a crucial parameter. This study successfully validates the performance of the proposed model by three well-controlled centrifuge model tests. Based on the test results in this study, it is highly feasible to realize the liquefaction risk assessment of gravelly soils covering various gravel contents on a regional scale by conducting a few benchmark element tests on the gravelly soils in question. Such reliable and accurate liquefaction evaluation of gravelly soils will aid in the seismic design of important infrastructures and reduce the cost of foundation treatment.