Evaluation of Post-Liquefaction Shear Strength and Shear Wave Velocity of Uniform Gravels

Assessing post-liquefaction shear strength is critical to robust design within a performance-based earthquake engineering framework. However, most research in soil liquefaction has focused on triggering of liquefaction and not post-liquefaction response. In addition, the liquefaction and post-liquefaction response of gravelly soils is not as well understood as sandy soils due to the challenges of testing large particle size materials in the laboratory. In this study, a prototype large-size cyclic simple shear (CSS) device was utilized to evaluate the post-liquefaction response of uniform gravels. Tested materials included 9 mm sub-rounded pea gravel, 8 mm angular crushed limestone, and 5 mm angular crushed limestone. Constant volume simple shear tests were performed to assess post-liquefaction undrained shear strength. Shear wave velocity was also measured in every specimen using a custom-built accelerometer system and was used as a comparison metric for test data with other laboratory and field data. Comparisons were made between existing design charts for clean sands and the data for uniform gravels in this study. Test results show that, in general, uniform gravels have higher VS1 values and greater post-liquefaction undrained shear strengths than the sands from case histories.