Shear Strength of Sands during Rapid Loadings

Abstract

Triaxial tests with times-to-failure ranging from 5 min to 5 milliseconds have been used to investigate the effect of strain-rate on the strength of dry and saturated sands. New techniques were developed for applying strains rapidly, and for measuring the resultant stresses and pore pressures. It was necessary to give careful attention to the possible influence of testing errors, of inertia forces, and of the membrane effect. The peak friction angles of the sands that were tested were substantially independent of failure-time. However, the excess pore pressures generated within saturated loose sands did, for certain conditions, vary with failure-time, and for these conditions the compressive strengths were correspondingly time dependent. A tentative hypothesis has been advanced to explain this behavior. One loos e saturated sand exhibited a pronounced yield point at low strains, and the yield point stress decreased as the rapidity of load application increased.