ESTIMATION OF ELASTIC MODULUS FOR JOINTED ROCK MASS

Abstract

This study is the extension of Singh's relationship between static mass modulus and joint frequency, which has been accepted by U.S.Corps of ;engineers in Design Manual. More available field data has been analysed to make recommen-dations on consideration of type of joints and rock material. Further, a theoretical study has been made to correlate static and dynamic modulus of elasticity of rock mass taking into account the deformability and frequency of joints, assuming that joints can be characterised by one dimensional elastic elements whose dynamic stiffness is proportional to static stiffness. The assumption that ratio of dynamic stiffness to static stiffness is a constant (".).9 has been verified partially. Laboratory tests have been conducted to estimate the ratio ( ) between static and dynamic elastic modulii of rock material. Above mentioned theoretical formula for estimating mass modulus have been employed for rocks of Tehri Dam site. Several horizontal and vertical plate load tests have been conducted in various grades of phyllites. The theoretical formula is found to be applicable. It is recommended that seismic tests must also be conducted at site to verify the other theoretical relationship presented here.