INFLUENCE OF DISCONTINUITIES ON THE BEHAVIOUR OF PARTIALLY SATURATED COMPACTED CLAY

Abstract

The partially saturated soil behaviour is quite different from those of fully saturated soil because of the presence of matric suction pressure. Although soils are generally assumed fully saturated below the groundwater table, they may be semi saturated near the state of full saturation under certain conditions. Results obtained with the strength theory of saturated soil could not be directly applied to solve the partially saturated soil problems, in particular to the soil containing discontinuities.It has been observed that discontinuities are known to develop when such geological materials are subject to loading. In the case of strong rock, on the other hand, there has been considerable interest in the application of fracture mechanics to account for such discontinuities. Moreover, the mechanical properties of soil that usually conducted by the use of triaxial apparatus rather than biaxial device will be addressed according to the fact that field problems involving geotechnical structures are often truly or close to plane strain situation. This paper will disseminate the result of some experimental testing on the effect of discontinuities on the properties of partially saturated compacted kaolin clay specimen under triaxiall and biaxial condition. A modification of the conventional triaxial apparatus wass used in this study. A high air-entry disc (HAED) was used as the interface between the unsaturated soil and the pore water pressure measuring system. Two types of intact specimen and pre-crack specimen have been tested under biaxial as well as triaxial condition. It was concluded that the discontinuities on the specimen weaken the shear strength as well as compressive strength of specimen.