ENGINEERING BEHAVIOUR OF INFILLED 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 instability of rock masses depend 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. The combined effect of shear zone, its stress... strain history and the resulting strength-deformation relation control the behaviour of rock mass. In present work, an attempt has been made to study the influence of gouge thickness on shear strength of infilled joints. Triaxial tests have been conducted on rock joints filled mr with gouge of thicknesses ranging from 0 to 20 mm. Clay has been used as infilled material. mot? The joint considered are smooth and undulating. The inclination of joint has been kept at 0° , 10° and 20° to the horizontal. The rock triaxial (HEICO) tests have been conducted with confining pressure varying from 2.5 to 8 MPa. The discontinuities have been modulated with phyllite rock sample by taking rock core of 38 mm diameter and 76 mm length. 1--/ 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. Linear relationships for the effect of normalized friction angle and thickness amplitude ratio have been obtained in this study. The behavior of rock mass under different dip angle varying from 0° to20° has been studied in this investigation. The behavior of rock mass with different gouge thickness, different joint inclination has been studied by conducting UCS tests on representative rock specimen.