Abstract
This paper describes a study on the interaction between joint fissures in a nonpersistent jointed rock mass by introducing a self-consistent methodology, amending the traditional method of self-consistency by increasing the number of joints one by one, and deducing a new compound mesoscale and macroscale constitutive damage model based on the Betti energy reciprocity theorem. By analyzing the Mohr–Coulomb failure criterion and generalized von Mises yield criterion and their impact on the calculation result of macroscopic damage, the generalized von Mises criterion is proven to be more appropriate, and it is, thus, chosen for this compound damage constitutive model. Comparing the theoretical calculation and laboratory results of the compound damage model with the existing theoretical calculation results indicates the following: 1. The compound damage model in this paper provides a better fit of the stress–strain curves from the laboratory tests. 2. The theoretical calculative results for the compound damage model in this paper are consistent with the experimental results; that is, the peak load decreases as the connectivity rate increases. 3. For different joint angles and connectivity rates, the overall absolute deviations and relative deviations of the peak stress from the theoretical calculations and the laboratory tests are less than those from the theoretical calculations provided in the original literature. The theoretical calculations of the compound damage model in this paper are more aligned with the experimental results, verifying its correctness and rationality.
Highlights
The theoretical calculative results for the compound damage model in this paper are consistent with the experimental results; that is, the peak load decreases as the connectivity rate increases
To verify the validity of the model built in this paper, the experimental results and corresponding theoretical results of a plaster model test [13], which is deduced from the compound damage constitutive equation based on the Lemaitre hypothesis [22], are compared with the theoretical calculation results of this paper
According to the above failure criteria, the influence factors of the microscopic damage variable calculations are analyzed with the generalized von Mises yield criterion, which produces results that more closely follow the results of the laboratory tests; this leads to the creation of the compound damage constitutive model presented in this paper
Summary
Natural wall rock has certain defects, such as joints, fissures, and cavities [1]. Under the effect of an external force, the mechanical characteristics of a rock mass are influenced by its internal structures. On the basis of the Lemaitre hypothesis, a damage variable equation considering both macroscopic and mesoscopic defects was derived by Yiqing Zhao, Hong-yan Liu, and other scholars [7], and the compound damage constitutive model of a jointed rock mass has been established. According to the equivalent elastic parameter model of the nonpersistent jointed rock mass proposed by Shilin Yan, a macroscopic and mesoscopic coupling damage variable expression was proposed by Xiaoqing Yuan and Hongyan Liu et al [8]. This model established a three-dimensional compound damage constitutive model for a nonpersistent jointed rock, but the complexity of its parameters is not conducive to calculation and application. On the basis of the effects of mesoscopic damage variables on different failure criteria, the difference in the calculation results of mesoscopic damage between the Mohr–Coulomb criterion and generalized von Mises criterion is studied, and these results are compared with laboratory test results [15]
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