Effect of Intermediate Principal Stress on Strength of Anisotropic

Rock Mass

(Tunnelling and Underground Space Technology, 1998 USA, Vol. 13, No. 1, pp. 71-79)

R. K. Goel, Bhawani Singh, V.K.Mehrotra, S.K. Garg, M.R. Allu

 

ABSTRACT

Mohr-Coulomb criterion is not applicable to highly anisotropic rock material and jointed rock masses. As such a new strength criterion taking into account s is suggested as both s and s will contribute to the normal stress on the existing plane of weakness. This criterion explains the enormous strength enhancement in the underground openings because s 2 along tunnel axis is not relaxed significantly. Another cause of strength enhancement is lower mass modulus reduction in tunnels due to restrained dilatancy. Empirical correlation obtained from block shear tests and uniaxial jacking tests have been suggested to estimate new strength parameters. Correlation for tensile strength of rock mass is also presented. Hoek and Brown theory is also extended to account for s 2. The attempt is to suggest common criterion for both underground openings and rock slopes.