Polar Graphs Presentation of Deformation Modulus in Anisotropic Blocky Rock Masses using Joint Stiffness Matrix

The anisotropy in the deformational behavior of blocky rock masses has been comprehensively investigated. Uniaxial deformation modulus was selected as the key parameter. It is generally anisotropic and depends on the loading direction as well as intact rock and joint properties and joint setting. Representative volumes of blocky rock masses were numerically simulated by the discrete element method and loaded uniaxially in various directions. Then the failure mode and the deformation modulus were studied for different loading directions and for various relative joint settings. A new nonlinear stress-dependent stiffness matrix for joints was introduced and used in wich surface conditions of the joints in terms of the joint roughness coefficient (JRC) and the intact rock materials in terms of the uniaxial compressive strength (UCS) were considered. The results of the assessments are presented in the form of rose diagrams showing variations of the blocky rock mass deformation modulus that are depend on joints JRC, intact rock UCS, and the rock mass structure in term of relative joint angle. Also, the expected degree of anisotropy for various surface joint conditions and uniaxial compressive strengths of intact rock were introduced. In the geological strength index (GSI) table, results are classified such that by assigning a value to JRC for each class of the joint surface conditions, deformation modulus and degree of anisotropy corresponding to GSI values can be determined