Measurement of Residual Strength of Liquefied Soil in Centrifuge Models

A technique for measuring the evolution of shear strength of liquefiable soils in physical models as earthquake-induced pore pressures change is desirable. It was envisioned that the shear strength of liquefying sands can be measured in-flight in a seismic geotechnical centrifuge model by pulling thin coupons (plates) horizontally through the soil models. The large strains and strain rates associated with liquefaction flow failures would thus be simulated by moving the coupon relative to the sand before, during, and after shaking. This paper presents the experimental details and results of seismic centrifuge tests on models of saturated F-75 sand that were used to make such measurements. It is shown that by measuring the drag force on the coupon, it is possible to observe the evolution of the soil shear strength as it decreases to a minimum (residual strength) and subsequently increases as excess pore pressures dissipate.