Influence of joints on Rock mass strength through modeling

Abstract

An assessment of the strength and deformational response of jointed rock masses is an essential requirement in the site selection, design and successful execution of Civil and Mining Engineering projects. An attempt has been made in the present study to develop a interrelation between strength and deformability of jointed block masses with the properties of intact specimens, obtained from simple laboratory tests, taking into account the influence of the properties of the joints in various angle and orientation. Jointed rock masses comprise interlocking angular particles or blocks of hard brittle material separated by discontinuity surfaces which may or may not be coated with weaker materials. The strength of such rock masses depends on the strength of the intact pieces and on their freedom of movement which, in turn, depends on the number, orientation, spacing and shear strength of the discontinuities. Various joint configurations will be introduced to achieve the most common modes of failure occurring in nature. A coefficient called Joint factor has been used to account for the weakness brought into the intact rock by jointing. Considering the importance of this study the experimental study has been under taken to determine the strength and deformation behavior of jointed rock mass. Models has been prepared using plaster of Paris and plaster of Paris & fine sand and different degrees of anisotropy have been induced by making joints in them varying from 0 to 90 degree. The specimens were tested under direct shear, uniaxial compression to determine the various parameters. From this study a guidelines would made for assessing probable modes of failure of a jointed mass which will enable one to estimate the relevant strength and tangent modulus of the jointed rock mass.