A comparative study on joints with and without gouge fill

Abstract

Rock is a discontinuous medium and the discontinuity may be in the form of joints or faults. Hence, the strength of rock mass generally depends on the type of discontinuity present in the rock mass. The strength of jointed rock mass generally depends on the joint spacing, inclination parameter and the roughness parameter. This joint roughness is a vital parameter which generally governs the strength of the rock mass. The roughness is usually computed with the help of direct shear test (r = tanφj). The deformation characteristics of rock mass are another parameter which is usually taken care in addition to the strength of rock mass and can be computed with the help of uniaxial compressive strength test. As collection of jointed rock mass and field testing of rock mass is tedious as well as difficult, hence jointed rock mass models are generally made in the laboratory itself. In the present study, plaster of Paris was used for modeling laboratory specimens as it is locally available and at the same time casting of jointed rock mass specimen can be done easily. The joints in rock mass specimen were made at various angles of orientation (β0) which is varying from 00-900. These models were possessing joints with and without gouge fill. Clay was used as gouge material. Here, an attempt was made to compare the results of strength and deformation characteristics of jointed rock mass with and without gouge fill by using model material plaster of Paris. From the experiments it is found that for single jointed rock mass specimen without gouge fill at β= 300 strength was found to be 0.22 MPa which is minimum and at β= 900 strength was found to be 7.34 MPa which is maximum. For single jointed rock mass specimen with gouge , further trend of decrease in strength was found and this is due to decrease in roughness parameter.Here , also at β= 300 strength was found to be 0.11 MPa which is minimum and at β= 900 strength was found to be 6.79 MPa which is maximum. An empirical relationship σcr= e-0.008 x Jf is applicable for joints with gouge.