Rock Failure Criteria for Design of Underground Structural Supports

摘要

This report describes an empirical constitutive model for underground excavations in rock which equates the deformation modulus to the ratio of the deviator stress to axial strain. The model requires failure criteria which define both the deviator stress at failure and strain at failure. Available failure criterion allows reasonable estimates of deviator stress for intact rock as well as rock mass. However, a failure criterion for estimating strains at failure for rock does not exist. Thus, this report examines the feasibility of developing a strain-based failure criterion for rock. Stress-strain responses for two rock types, sandstone and granite, were evaluated. Reasonable correlations were found to exist between axial strain at failure normalized with respect to unconfined compressive axial strain at failure and the following: (1) Maximum shear stress normalized with respect to the unconfined compressive strength. (2) Minor principal stress (confining stress) normalized with respect to the unconfined compressive strength. (Author)