A Method for Correcting Undrained Shear Strength for Sample Disturbance

Abstract

In order to find out an appropriate method for correcting the undrained shear strength for sample disturbance, a series of triaxial compression tests is performed on mixed soil samples having wide range of plasticity index. Conditions of the ideal and perfect samples are brought to by the K 0 consolidation and the shear stress release after the consolidation, then further disturbance is given to specimens by cyclic loadings. Model sampling is made for obtaining the “undisturbed” samples, and unconsolidated undrained triaxial compression tests are performed on these “undisturbed” samples. In these compression tests, the pore pressure is measured for assessing the residual effective stress in the ideal, perfect and “undisturbed” samples respectively. Results of the compression tests show that the pore pressure can increase on shear stress release for soils of low plasticity index, and that the effect of sample disturbance is similar to the effect caused by cyclic loadings. By combining the concepts of strength reduction due to rebound and reduction in effective stress due to sample disturbance, a comprehensive way for correcting the measured value of the undrained shear strength for sample disturbance is proposed.