A Study on the Creeping Failure related to Crack Inclination of Brittle Rocks

摘要

A new micro-macro modelling approach is presented for predicting the creeping failure behaviors in brittle rocks. Effect of crack inclination angle is especially considered in this approach. This method is formulated by the combination of an improved stress intensity factor, a time- dependent cracking law, and a correlation of crack extension and axial strain. This improved stress intensity factor is derived by drawing crack inclination effect into Ashby and Sammis' wing crack model. This correlation of crack extension and axial strain is established by coupling the expressions of micro-damage with macro-damage. The analytical stress-strain relation and creep equation considering crack inclination effect are derived. Furthermore, crack inclination phi, crack size a, crack friction coefficient , and parameter are predicted by using the experimental data of crack initiation stress related to confining pressure, which provides a novel method in applying the proposed micro-macro model to natural rock. Influences of confining pressure on creep behaviors subjected to step axial loading and quasi-static behaviors are analyzed. The creep and quasi-static failure properties related to crack inclination are also discussed. Rationality of this proposed micro-macro approach is validated by comparing with experimental results.