| Rock mass is a geological body composed of numerous structural planes of different size and various occurrence and abundant rocks of diverse shape and unequal magnitude by structural planes cutting. Thus, deformations of rock mass under stresses are also mainly composed of deformations of structural planes and rocks. As rocks are usually stiffer than structural planes, deformations of rock mass mainly occur in structural planes. Normal deformations and shear deformations of structure planes may result in closure, tension crack, initiation and propagation of the structure planes, causing changes in the fracture network and structural characteristics. Rock seepage in essence is also affected by the control of the structure planes. Deformations of structural planes and changes of rock structural characteristics will cause changes in rock mass permeability properties, which demonstrates the dependency of rock mass permeability properties on states of rock mass deformations and stresses. In summary, the engineering properties of the rock mass on mechanics, thermodynamics and fluid mechanics, as basic scientific issues of rock mechanics, are significantly affected by the existence of structural planes. In this article, works closely focusing on rock mechanics and hydraulic characteristics were carried out, and combinative methods of theoretical analysis, numerical simulation and experimental research were adopted. Its main contents are as follows:1. Previous theoretical works of3D morphology parameters of structural planes were systematically summaried. Based on Grasselli’s and Homand’s works, on account of data of3D morphology measurement and shear tests,3D morphology parameters of structural planes such as weighted average of effective shear angles and maximum effective shear area were proposed. The3D morphology parameters variation of rock joints before and after shear test is analyzed, and the variation of different lithological structural planes and its influencing factors comparatively studied.2. Two types of structural planes such as granite and red sandstone, each divided into five groups, were adopted in the shear tests. The variation of shear strength and morphology parameters of structural planes under constant normal stresses during shear were analyzed. Based on the Mohr-Coulomb strength theory and the variation of shear stresses and normal stresses measured in shear tests, the value of the total frictional angle were determined. The evolution of the dilatancy angle, excluding the basic friction angle of the joints, was analyzed. Then, an empirical model is proposed to relate3D morphology parameter with the shear strength of rock joints. Based on multiple shear tests of the same structural planes, the attenuation law of shear strength and the influence of morphology on shear strength were analyzed. The quantitative relation of shear times, shear strength and morphology parameters was studied, and shear strength model of structural planes in multiple shear was proposed.3. Permeable experiments on deformation and failure process of rough sandstone were carried out in triaxial test instrument, the hydraulic conductivity of rough sandstone in deformation and failure process was analyzed, the impact confining pressure on hydraulic conductivity of rough sandstone was discussed, and the relationship between hydraulic conductivity and volume strain was studied. During the process of deformation and failure, the hydraulic conductivity is more sensitive to the change of lateral strain. With increase of confining pressure, the peak and residual value of hydraulic conductivity in deformation and failure process decreases, the curve of hydraulic conductivity-strain tends to be gentle. Based on the mass conservation equation of the theory of porous media, the relationship between porosity and volume strain was deduced. By using the Kozeny-carman equation, the relationship between the hydraulic conductivity and volume strain was studied, the results show that Kozeny-carman equation has good applicability when pores dominate the flow channel.4. Based on the conclusions of the existing study on the shear-flow tests, a new laboratory apparatus for coupling shear and seepage of rock joints was developed and used to investigate coupling effect of joint shear deformation and dilatancy on hydraulic conductivity of rock joints. The structure and function of the apparatus were described in detail. Two kinds of normal loads way can be used in this technique, constant normal load (CNL) and constant normal stiffness (CNS). The sealing system of shear box consists of polyurethane rubber seals in the two side panels and polyurethane rubber blocks in the water inlet and outlet. By adopting this technique, four groups of granite joints specimens were used to carry out the shear-flow test under the conditions of CNL and CNS. The reliability of this technique was demonstrated by the experiment results. |
PDF Full Text Request