BEHAVIOUR OF SOFT ROCK IN TRIAXIAL STRESS CONDITION

Abstract

The objective of the work reported herein, was to determine the behaviour of soft rock in triaxial stress condition under various confining pressuresranging from 10 to 100 kj./cm2 on'airdried and overdried specimens. The effect of confining pressure on deformational and strength parameters such as ultimate strength, modulus of deformation, strain at failure, mode of deformation, type of failure, and angle of internal friction etc. were studied. Silt Stone of Middle siwalk formation (J & K area) were used in this programme. Laboratory tests such as specific gravity, porosity and water content were condubted on all specimens to determine homogeneity of each sample of rock. Results of non-destructive tests indicated that the rock within each rock sample was quite uniform. Results of triaxial tests indicated that the maximum deviator stress and total axial strain increased as the confining pressure was increased. The rock was less brittle at high confining pressure. The MOhr repture envelope is nonlinear. The applicability of. failure criteria suggested . by Beiniawaski, Hoek and Brown are studied. The testing on saturated specimens of the silt stone could not be carried out due to linited facilities available in the laboratory.