Weakening Effect of Water on Mechanical Properties of Brittle Shale under Triaxial Compression

Abstract

The mechanical properties of rock materials are remarkably affected by water. To reveal the effect of water on the mechanical properties of shale, the conventional triaxial compression tests were implemented for shale with the five kinds of water saturation coefficient. According to the test results, the influence of the saturation coefficient on strength and deformation parameters was analyzed. Based on the fitting result of the Mohr-Coulomb criterion, the relationship between the strength parameters and the water saturation coefficient was analyzed. The softening effect of water on shale is mainly due to the decrease of cohesion and internal friction coefficient with increasing of water saturation coefficient. The strength criterion considering the influence of water weakening was established according to the function relationship between the fitting parameters and the water saturation coefficient. In addition, three kinds of brittleness indexes were selected to quantitatively analyze the influence of the saturation coefficient on shale brittleness. The results indicated that the brittleness indexes all decreased with the increase of the saturation coefficient, and the brittleness of shale is weakened after water absorption. The research results can provide a reference for the evaluation of saturated shale brittleness.