Model tests on permeability of columnar jointed rock mass

Because of the lack of researches on the permeability of the columnar jointed rock mass, model tests on the similar material of columnar jointed rock mass are carried out to study their permeability during cyclic loading and unloading of confining pressure. It is shown that the equivalent medium model is suitable for analysis of the permeability of columnar jointed rock mass. The method for calculating the permeability tensor of columnar jointed rock mass is proposed based on the tensor invariant theory. The researches show that the major permeability coefficient of the permeability tensor of columnar jointed rock mass is significantly reduced during the first loading of confining pressure, and it maintains a low value during the subsequent cyclic loading and unloading of confining pressure stage. The relationship between the major permeability coefficient of permeability tensor and the confining pressure is power function relationship during each cyclic loading and unloading of confining pressure stage. The major direction of the permeability tensor of columnar jointed rock mass increases gradually along with the loading and unloading of confining pressure. It increases significantly during the first confining pressure loading stage, but its increase becomes slow during the subsequent cyclic loading and unloading of confining pressure stage. The permeability anisotropy of columnar jointed rock mass under low confining pressure is more significant, and it decreases along with the increase of cylinder angle. The permeability anisotropy of columnar jointed rock mass decreases rapidly along with the increase of confining pressure during the first confining pressure loading stage, and cylinder angle has little impact on the permeability anisotropy of columnar jointed rock mass during high confining pressure stage. The permeability anisotropy of columnar jointed rock mass