CHARACTERIZATION OF MODEL MATERIAL FOR SHEAR STRENGTH BEHAVIOUR OF JOINTED ROCKS

Abstract

The analysis of engineering behavior of jointed rock is typical and depends upon various properties of jointed rock such as stic, frictional, surface roughness and adhesion properties. Stability analysis in jointed rock is often governed by the stability of a critical joint. In such cases, it is assumed that no interaction exists between the rock and the joint; the joint can therefore be considered isolated. The engineering characteristics of the joint plane are necessary for assessing instability. The direct shear test is a suitable experiment to determine these parameters. In the present study an attempt has been made to study a jointed mass under direct shear test. The specimen has been made large enough. So they have negligible scale effect. Due to ease in working and reproducibility of results a model material has been used. The jointed mass is prepared with the help of cement sand mortar having ratio 1:3 and water cement ratio 0.5. The orientation of the joint varies between 0° to 45° at an interval of 15°. During the direct shear tests normal stress (0.16MPa, 0.246MPa, 0.32MPa, 0.40MPa and 0.48MPa) was kept constant. The shearing displacement and the normal displacements were recorded with respect to shearing stress for all orientations. The instantaneous cohesion and friction angle are also analyzed. The shear behaviour of jointed mass under low normal condition and the effect of orientation of joints with respect to direction of shear stress was analyzed for the present study.