Static Liquefaction Assessment Combining Shear Wave Velocity, Peak Strength and Soil Grading

A large set of undrained compression triaxial tests was carried out on different types of cohesionless soils, from sands to silty sands and silts. Shear wave velocity measurements were also carried out. These tests exhibit distinct state transitions ranging from flow liquefaction to strain softening or strain hardening. With the purpose of defining a framework to assess soil liquefaction, it was found that the ratio between the shear wave velocity (V-S(0)) and the peak undrained deviatoric stress (q(peak)), V-S(0)/q(peak), could be accurately used to define a boundary between liquefaction and strain hardening for sands and between strain softening and strain hardening for silty sands and silts. Since this ratio is a function of the tested material, the prediction of these boundaries can be made as a function of soil grading, namely via the coefficient of uniformity, C-U. Despite not being regarded as a strong geomechanical parameter, C-U is easily determined from a grain-size distribution test and has an empirically proven correlation with critical state parameters.

Automated summary

A set of undrained compression triaxial tests was conducted on various types of cohesionless soils, demonstrating distinct state transitions from flow liquefaction to strain softening or hardening. The ratio of shear wave velocity (V-S(0)) to peak undrained deviatoric stress (q(peak)), V-S(0)/q(peak), was found to accurately define the boundaries between liquefaction and strain hardening for sands, as well as between strain softening and strain hardening for silty sands and silts. As this ratio depends on the tested material, the estimation of these boundaries can be achieved through the coefficient of uniformity (C-U) derived from a grain-size distribution test, which empirically correlates with critical state parameters.