STUDY OF STRENGTH CRITERIA OF ROCKS

Abstract

A criterion of failure is an algebric expression of the mechanical condition under which a material fails by fracturing or deforming beyond some specified limit. This specification can be in terms of load, deformation, stress, strain or other parameters. The difficulty of finding a realistic failure criterion for rock masses, is due to transition from intact rock material to a heavily jointed rock mass. Till now a number of failure theory and empirical relationship has been developed. Some important are : (i) Coulumb - Navier criterion (1773) (ii) Shear failure (Mohr) theory (1900) (iii) Griffith criterion (1921) (iv) Hoek criterion (1968) (v) Bieniawski criterion (1974) (vi) Hoek-Brown criterion (1980) (vii) Modified Hoek (Yoshinaka-Tadasi) criterion (1980) (viii) Generalised Bieniawski (Yudhbir) criterion (1983) (ix) Ramamurthy criterion (1985) (x) Johnston criterion (1985) The above criteria have been compared rationally for the rocks tested. It has been found that though in general no single criteria seems to be acceptable for all the types of rocks but Hoek (1968) criterion has been found to be applicable to the types of rocks tested. It seems to be more rational in case of basalt and dolomite.