STUDY ON A CRACK PROPAGATION AND FRACTURE TOUGHNESS OF ROCKS

Abstract

Fracture toughness tests of rocks were performed to investigate a crack propagation behavior and fracture toughness (K_1C) of rocks under a confining pressure or a low temperature. Fracture process markedly indicated nonlinearity. So, in this paper a crack length is evaluated by compliance calibration technique using results of fracture toughness test and then K_1C is calculated with a maximum load and a crack length. As for a shape and scale effect of K_1C, experiments showed that beam specimens was adequate for rocks. K_1C of rocks linearly increases in the pressure range to 15 MPa and a temperature dependence of K_1C is caused for water saturated rocks. A cyclic strain incremental tests indicates that J-integral is a effective parameter as the crack growth criteria.