STRESS DISTRIBUTION IN SHOTCRETE LINING IN CAVERNS

Abstract

There has been an increase in the number of underground power projects in India because of economic and environmental reasons. Construction of wide caverns is the prime necessity for the successful installation of hydro-power projects. Since the long-term stability of the cavern is of primary concern, the analysis of cavern involves evaluation of stresses and displacements in the shotcrete and steel fibre reinforced shotcrete (SFR) lining provided as a support system. In this present study, the distribution of stresses in the shotcrete and steel fibre reinforced shotcrete lining around the periphery of the wide cavern have been plotted after analyzing the problem by finite element method. The mode of failure of the shotcrete and SFR shotcrete has been studied. It has been found that there will be tensile failure in the lining along the wall of the cavern while lining on the roof will fail due to shear stresses. The maximum shear stress occurs at two third points in the roof. This fact offered from deterministic approach matches with the observation made by Singh et.al (1995) in design philosophy of support system for caverns. As the present study matures, it becomes obvious that in-situ stresses are more dominant as compared to the support pressure for creating stresses in the shotcrete lining. The effects of provision of anchors and surface waviness have been found only marginal. The offered conclusion from the study is that the recommendation of SFR shotcreting is justified due to its high tensile strength and ductile nature.