Study on stiffness of a mudstone in multiple-step loading triaxial compression test

Abstract

In Multiple-step Loading Triaxial Compression Testing (ML-TCT), it is assumed that the deformation characteristics should only be measured in the first loading step [1]. However, the variations of stiffness in the following loading steps have not been discussed in the literatures. Moreover, the effect of confining pressure on stiffness is found to be difference in different kind of material [2]. Specially, the effect of stepwise increase of confining pressure in ML-TCT is not known yet. In this study, ultrasonic wave measurements and triaxial compression tests were carried out on a mudstone. In triaxial compression tests, multiple-step loading method at different and constant effective confining pressures was used. The effects of confining pressure and accumulated damages in the specimen during shearing on the stiffness are discussed.