Mechanical and permeability characteristics of rock under hydro-mechanical coupling conditions

A study on the mechanical characteristics and permeability properties of sandstone and limestone from a coal mine under 3D stresses has been carried out with the MTS815 rock mechanics test system, and the characteristics of mechanics and permeability before and after the rock failure under hydro-mechanical coupling conditions have been analyzed and discussed. The research revealed the difference of mechanics and permeability before and after the rock failure and obtained the relationship among the strength, deformation and differential water pressure. It also obtained the correlation among the permeability and stress, strain and revealed the features of fractures which influenced the correlation. The results show that there are obvious weakening effects of differential water pressures on the mechanical properties after the rock damages; the permeability of rock mass in practical engineering is mainly controlled by the features of fractures; the permeability has an negative index correlation with the axial strain epsilon(1), and has a power function correlation with the mean stress sigma(m)(sigma(m) = (sigma(1) + 2 sigma(3))/3); for fractured limestone and coarse sandstone, the permeabiity will tend to be stable gradually when the mean stress reaches or exceeds a certain value sigma(ml).