STRENGTH BEHAVIOUR OF IN FILLED ROCK JOINTS

Abstract

The shear strength of rock masses is greatly affected by the infilled material. The material gets infilled into the joint of rock masses by deposition of sediments flowing with water through the joints and weathering of rock surface of joint planes. The factors like nature of infilled material, water content of infilled material, thickness of infilled material, .orientation of joint surface, asperity of joint surface etc. influence the shear strength of rock masses. Due to number of these influencing parameters, it becomes difficult to determine the shear strength of rock masses. The stability of rock masses depends on the geometry of 'discontinuities, slope and orientation of excavated faces. One of the most important factors to which the shear strength of rock mass can be attributed, is the shear strength of potential failure planes. On the basis of mere visualization and conventional laboratory tests on the specimen, the characterization of discontinuities or shear zone is not possible. In present work, an attempt has been made to study the influence of gouge thickness on the shear strength of infilled joints. Triaxial and UCS tests have been conducted on Granite — Gneiss rock joints specimen of size 58.5 mm diameter, filled with gouge of thickness ranging from 0 to 5 mm. Clay has been used as infill material. The joint considered are undulating. The inclination of joint has been kept dip angle (beta (i = 800-900, 70°-80°, 600-700, 500-600 with vertical) i.e. .e. 00-100, 10°-20°, 20°-30°, 30°-40°. with horizontal. The rock triaxial tests have been conducted with confining pressure 10, 15 and 20 MPa. In this investigation, the effect of gouge thickness over the shear strength of rock mass, the effect of dip angles of joint planes, surface profile of joints on the shear strength of rock mass have been studied and analyzed. The behaviour of rock mass under different varying dip angle has been studied in this investigation. The behaviour of rock mass with different gouge thickness, Different joint inclination has been studied by conducting UCS tests on representative rock specimen. An equation for infilled rock joint has been proposed. I'd