An Anisotropic Failure Criterion for Jointed Rocks Under Triaxial Stress Conditions.

In the field of rock engineering, the anisotropic failure criterion plays a vital role in predicting the strength of rocks with varying degrees of anisotropy. This study presents jointed rock as a composite material, encompassing both joints and rock blocks. A comprehensive model has been developed for jointed rock, introducing a new parameter denoted as η to account for the influence of joint thickness. Consequently, a predictive strength model that considers the thickness effect of joints has been formulated. Unlike Jaeger's single weak plane failure criterion, which exhibits a characteristic "U" shape, a novel functional model has been proposed. This new model explains the variation in strength concerning the angle of inclination. As a result, a new anisotropic strength criterion for jointed rocks has been developed. This criterion also provides a method for determining its parameters using Jaeger's failure theory. To validate the proposed criterion, 189 sets of test results from five distinct types of anisotropic rocks were utilized. The newly developed failure criterion aims to accurately estimate the anisotropic strength of jointed rocks. Moreover, it offers new criteria for evaluating the stability of engineering rock structures, particularly its applicability in predicting the strength of jointed or stratified rock mass exhibiting significant anisotropy. Highlights: A new rock strength empirical model considering the effect of joint thickness has been proposed, where the thickness and strength of joint surfaces have a significant impact on the overall strength. The overall strength of jointed rock mass shows a negative exponential decreasing trend with the increase of joint thickness. The larger the proportion of joint thickness, the closer the overall strength is to the strength of the joint surface. As the confining pressure increases, the anisotropy gradually weakens, and the confining pressure has an inhibitory effect on the anisotropy of the rock. A new empirical triaxial anisotropic failure criterion is proposed according to the variations of strength with θ and stress conditions. [ABSTRACT FROM AUTHOR]