EXPERIMENTAL STUDY ON PERMEABILITY OF POROUS MEDIA UNDER HIGH CONFINING PRESSURE

This paper examines permeability of porous media under different confining pressures. It uses unchangeable water pressure method. Large size soft rocks with low permeability have been systematically tested with a new equipment called high pressure permeability testing machine in laboratory. The penetration water pressure fluctuation scope is 0.01 MPa. The seepage exit water volume testing precision is 0.05 ml. According to a linear relationship of water volume and time, seepage quantity can be accurately calculated. The test results demonstrate that the permeability coefficient decreases with the increasing of confining pressure, and increase when unloading. The increasing rate during unloading is lower than that during loading. On the basis of the axial strain variation situation, it is found that the rock permeability change is mainly affected by the confining pressure during the coupling process of stress-seeping in rock samples at laboratory. The confining lateral pressure makes the porosity and seepage pipes to have compressive deformation.