Abstract
Columnar jointed rock mass (CJRM) is a highly symmetrical natural fractured structure. As the rock mass of the dam foundation of the Baihetan Hydropower Station, the study of its permeability anisotropy is of great significance to engineering safety. Based on the theory of composite mechanics and Goodman’s joint superposition principle, the constitutive model of joints of CJRM is derived according to the Quadrangular prism, the Pentagonal prism and the Hexagonal prism model; combined with Singh’s research results on intermittent joint stress concentration, considering column deflection angles, the joint constitutive model of CJRM in three-dimensional space is established. For the CJRM in the Baihetan dam site area, the Quadrangular prism, the Pentagonal prism and the Hexagonal prism constitutive models were used to calculate the permeability coefficients of CJRM under different deflection angles. The permeability anisotropy characteristics of the three models were compared and verified by numerical simulation results. The results show that the calculation results of the Pentagonal prism model are in good agreement with the numerical simulation results. The variation of permeability coefficient under different confining pressures is compared, and the relationship between permeability coefficient and confining pressure is obtained, which accords with the negative exponential function and conforms to the general rule of joint seepage.
Highlights
A columnar jointed rock mass (CJRM) is formed by cutting the intact rock from different structural planes, and has long-term complex geological evolution and possesses strong symmetry [1,2,3]
To study the seepage characteristics of CJRM, the Pentagonal prism model was added on the basis of the commonly used Quadrangular prism and Hexagonal prism models, and the corresponding three-dimensional seepage constitutive model considering hidden joint and prism
To study the seepage characteristics of CJRM, the Pentagonal prism model was added on the basis of the commonly used Quadrangular prism and Hexagonal prism models, and the corresponding three-dimensional seepage constitutive model considering hidden joint and prism deflection angle was established
Summary
A columnar jointed rock mass (CJRM) is formed by cutting the intact rock from different structural planes, and has long-term complex geological evolution and possesses strong symmetry [1,2,3]. The permeability characteristics of the jointed rock mass mainly depend on the joint features [9,10]. The theoretical analytical method providesand a convenient and fasttheway of studying the characteristics of jointed rock masses. Withtorespect to stress-seepage [17] obtained a stress-dependent quadrilateral columnarcolumnar joint seepage model through a triaxial seepage test; Xiong [18]. It can be seen that the Hexagonal columnar joint was obtained using a triaxial seepage test [19,20]. The joint constitutive model of CJRM in three-dimensional space is established, and the joint mechanical aperture is converted into the equivalent hydraulic aperture, and the permeability coefficient is calculated. The results show that the constitutive relation of the Pentagonal prism model has good applicability and can provide a reference for the permeability analysis of large-scale water conservancy and hydropower projects
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