Post-Liquefaction Volumetric Strain of Gravel-Sand Mixtures in Constant Volume Simple Shear

Estimation of post-liquefaction settlement is critical to robust design within a performance-based earthquake engineering framework. However, most research in soil liquefaction has focused on triggering of liquefaction rather than post-liquefaction response. In addition, the liquefaction and post-liquefaction response of gravelly soils is not as well understood as sandy soils because of 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 gravel-sand mixtures. Test materials included 9 mm subrounded pea gravel, 8 mm angular crushed limestone (CLS8), subrounded Ottawa C109 sand, and mixtures of gravel and sand at varying percentages. Constant volume cyclic simple shear tests were performed to assess post-liquefaction volumetric strain (settlement). The effects of particle angularity, relative density, and mixture percentage on post-liquefaction volumetric strain were investigated. The results show that post-liquefaction volumetric strain is dependent on particle angularity. As particle angularity increased, the post-liquefaction volumetric strain decreased for the uniform materials (Ottawa C109 sand, pea gravel, and CLS8). The subrounded pea gravel and subrounded Ottawa C109 sand had similar post-liquefaction volumetric strains, indicating that uniform gravel and uniform sand can have similar values of post-liquefaction volumetric strain if their particle morphology is similar.