Rock Bolts and Shear Stiffness in Jointed Rock Masses

Abstract

Both deformational response and stress distribution in an anisotropic rock mass are examined. Joint imposed rock mass anisotropy is considered in relation to joint and rock material shear stiffness. Two typical rock mass deformational characteristics are investigated by considering component moduli representing a firm and then soft rock mass. These component moduli are combined to give composite moduli and resultant directional rock mass Young's modulus. The resultant Young's modulus is defined first from classical infinitesimal elastic theory and then considering specific deformations. There are major differences between the two definitions involving shear moduli and Poisson's ratio. For an anisotropic rock mass, the induced horizontal stress derived from a rock bolt produces an armoring effect that is so often observed in practice. Rock bolt effects on rock mass anisotropy and deformability are investigated by considering joint shear characteristics.