SEISMIC STABILITY ANALYSIS OF UNDERGROUND CAVITY IN JOINTED ROCK MASS USING DISTINCT ELEMENT METHOD

Abstract

The mechanical behaviour of a jointed rock mass is strongly, and sometimes dramatically, affected by the behaviour of the discontinuities present in jointed rock mass. In many cases, preferential failures are dominated or defined by the natural discontinuities present in the neighbourhood of engineering works. Closed formed solutions are available for some typical shapes of openings. However, in practical the tunnels as well as other underground openings are of different shapes for which the closed forms of solutions are not available. The numerical methods are mostly used for analyses of rock engineering problems. Distinct element method (DEM) is a powerful approach in modeling the behavior of fractured rock mass. This method can account for large displacement and rotation of rock mass and is more useful for the field of rock engineering. Other numerical method like Finite element method, boundary element methods etc. can attempt to model the discontinuities but this methods gives the limited representation of jointed rock mass. The present work is an attempt to use the distinct element method to evaluate the displacements and stresses caused due to excavation. Two dimensional distinct element code (UDEC) has been used for the analyses. The analysis of Tehri powerhouse cavern has been done for this study. This cavern has been excavated in jointed rock masses intersected by the fault zones. The stability of cavern is also studied under the static and earthquake condition. The results are presented in the form of displacement and stresses around the opening. The behaviour of rock bolts is also studied.