Effects of strain rate on gravelly soil under undrained condition

In order to study the effects of strain rate on strength and stress-strain behavior of gravelly soil and its mechanism,consolidated-undrained triaxial compression tests under different confining pressures were carried out for saturated gravelly soil mixed by clay and gravel.Effects of strain rate on undrained strength were analyzed quantitatively within the strain rate range from 0.028 %/min to 0.690 %/min.According to those test results,it is shown that the stress-strain curves under different strain rates are similar.For this kind of gravelly soil,undrained strength would increase 7.4%-29.9% with the increase of 10 times of strain rate.The effects of strain rate of gravely soil are caused by both pore water pressure induced by shearing and cohesion of the soil material.However,for these two aspects the degrees of influence on strain rate effects are different under different confining pressures.