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Abstract In order to include the geometrical characteristics of jointed rock masses in its constitutive relations，a two-order tensor is adopted as damage variable. Joint connectivity at any direction of jointed rock masses is expressed as a continuum function of its normal vector and the damage tensor. Consequently，shear strength parameters of jointed rock masses，i.e.，friction factor and cohesion are weighted average of those of entire rock and entire fissures respectively according to joint connectivity，and implicit anisotropic yield criterion for jointed rock masses can be obtained through the Mohr-Coulomb yield condition for plane in every direction. In principal stresses space，the damage tensor is divided into two parts：the isotropic part and deviatoric part. According to rigor analytical solution to critical normal vector of the most disadvantage section for isotropic damage tensor，explicit yield criterion for isotropic joint rock masses is obtained，and an approximate analytical solution with one order precision to critical normal vector of the most disadvantage section for general damage tensor is obtained. The explicit anisotropic yield criterion for jointed rock masses is a form of quadratic equation of principal stresses in which its coefficients are functions of the damage tensor. The anisotropic yield criterion can be fully determined by the two-order damage tensor which has six independent variables，i.e.，the three principal values of damage tensor and the three Euler angles which represent the relations of principal vectors of damage tensor and those of principal stresses. In four examples，how the six variables affect the anisotropic properties of rock yield stresses in principal stresses space is analyzed by figuring out yield curve in deviatoric plane and meridian plane through the implicit and the explicit anisotropic strength criterion respectively. It is concluded that the explicit anisotropic yield criterion for jointed rock masses which is obtained by approximate analytical method has high precision.
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Received: 30 October 2003
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2005, Vol. 24 
