Abstract
Drained true triaxial tests on a normally consolidated clay under a constant mean principal stress condition are performed using a newly made apparatus in which two principal stresses are applied by rigid plates and the other principal stress by a chamber water pressure. After checking the accuracy of the tests, the deformation and strength characteristics of clay in three-dimensional stresses are experimentally discussed, and the test results are compared with the analytical results by the well-known Cam-clay model and those by the tij-clay model which has recently been developed with reference to the extended concept of "Spatially Mobilized Plane". Although the Cam-clay model does not explain uniquely the observed shear behavior of clay in three-dimensional stresses, the tij-clay model takes into account adequately the influence of the intermediate principal stress on the behavior of clay and can describe the deformation and strength characteristics of clay with unified values of soil parameters which are easily determined from a conventional triaxial test and others.
