MODELLING OF STRENGTH AND DEFORMATIONAL BEHAVIOUR OF JOINTED ROCK MASS UNDER UNIAXIAL LOADING CONDITION

Abstract

Many engineering structures like dams, tunnels, bridge piers, foundations, underground openings and caverns for hydroelectric scheme are built on and in rock masses. The jointed mass fail in several modes and dilation occurs due to roughness and interlocking of the joints. Understanding the failure mechanism of the rock mass and the modeling of the stress-deformation behaviour is necessary for reliable analysis and design of the structures in such rock masses. Experimental data on jointed block mass under uniaxial loading condition (Singh, 1997), have been analyzed using concept of Joint Factor. Correlation have been suggested to asses the strength of a jointed mass in the field. The strength of the mass is limited to the strength of intact rock through Joint Factor, which can be computed based on mapping of joints in the field, expressions have also been developed to asses the _failure strain of 'ointed mass underuniaxial loading conditions. A constitutive model has been simulated by using experimental data (Singh, 1997) to explain the stress- deformation behaviour of jointed rock mass. The model is based on the normal and shear stiffnesses of the joints. The stiffnesses are treated to be varied with normal stress level. The effect of dilation on the deformational behaviour is also considered in this model.