Hydro-mechanical properties of rock-like specimens with pre-existing intermittent joints.

Pre-existing joints within a rock mass has a significant effect on the hydro-mechanical properties of the rock mass. The study investigates the hydro-mechanical properties of rock-like materials with intermittent joints under different confining and hydraulic pressures. Cylindrical specimens containing two sets of parallel pre-existing joints were prepared, and the hydro-mechanical experiments under different hydraulic pressures were carried out using a servo-controlled rock triaxial testing system. The test results show that the strength, permeability and deformation properties of the specimens were influenced by the hydraulic pressure. The four stages of evolution of permeability in the deformation process is closely correlated with the development of joints and cracks within the specimen. The relations between volumetric strain and permeability were analyzed and discussed. It is found that the exponential function describes the permeability and volumetric strain relation well in the contraction stage. When the fluid pressure is high, the fluid pressure has a larger impact on the specimen failure mode than the pre-existing thin joints within the specimen in this test. [ABSTRACT FROM AUTHOR]