Rate Effects And Cyclic Loading of Sensitive Clays

Abstract

The paper presents the results of a series of monotonic and cyclic triaxial tests carried out to study the influence of the rate of strain and load cycles on the undrained shear strength of three undisturbed sensitive clays from eastern Canada. For structured clays (naturally overconsolidated), pore pressures generated at a given deviator are essentially independent of the strain rate, while the peak strength envelope is lowered as the strain rate is decreased. For destructured clay (normally consolidated), a lower strain rate results in an increase in pore pressure generation during shearing, due to the tendency of the clay skeleton to creep, while the peak strength envelope remains the same. Nevertheless, from a quantitative standpoint, the increase in shear strength caused by an increase in strain rate is similar for both structured and normally consolidated clay, and it is linear for at least five log cycles of strain rate.