DDA Simulation Study on Mechanical Failure of Heterogenous Rock

Abstract

Heterogeneity is an important characteristic that affects the mechanical behavior of rock. In the present work, a statistical rock mesoheterogeneity model based on the Weibull distribution function is introduced into the discontinuous deformation analysis (DDA) method to simulate the mechanical failure of heterogeneous rock, in which the general heterogeneity degree is controlled by a heterogeneity index and the mechanical property of each subblock element is randomly assigned. Brazilian disc and uniaxial compressive rectangular specimens are simulated as examples. Results show that it is more reasonable to consider the heterogeneity of elasticity properties (the elastic modulus and Poisson’s ratio) and strength properties (the tensile strength, cohesion, and friction angle) simultaneously in the heterogeneity model. It is also shown that with a larger heterogeneity index, which means a lower degree of heterogeneity, the reproducibility of the macroscopic response curves of a specimen gets better, while the exact cracking always differs but with less scattered cracks, and the global fracturing failure pattern and mode are weakly influenced by the heterogeneity. Moreover, with the increase in the heterogeneity index, the macroscopic equivalent modulus and strength get larger and approach those of a homogeneous specimen. This work indicates the importance of heterogeneity for rock mechanical behaviors including the macroscopic equivalent response and the fracturing failure. By the subblock DDA method to simulate fracturing realistically, the fracturing failure process of heterogeneous rock can be successfully reproduced, which builds good foundation for the simulation study of heterogeneous rock fracturing in practical problems, e.g., coal and rock fracturing in fluidization mining in the future.

DDA simulation study on fracturing failure reproducibility of heterogenous rock

“…However, it is a fact that the strength varies with locations like that of the elasticity in real rock at the mesoscale, which means that the heterogeneity of strength should be considered as well. It was proved that rock is more prone to be destructed accompanied by more dispersing cracks when considering the heterogeneity of elasticity and strength simultaneously (Ning et al, 2021). Therefore, in the present study the elasticity and strength heterogeneities are both considered.…”

“…An element-level mesoscale heterogeneity model is applied in DDA based on the Weibull distribution function. By introducing the mesoscale heterogeneity, the macroscale nonlinear behaviors of rock could be well represented based on the linear-elastic constitutive relation of DDA (Ning et al, 2021). From the Weibull distribution formula, p x ( )…”

“…In the previous work (Ning et al, 2021), the influence of the heterogeneity degree on the fracturing failure of intact disc and rectangular specimens was investigated by considering five different values of the heterogeneity index m, namely, 1.5, 2.5, 5, 20, and 200. In the present work, a middle level heterogeneity, namely, m = 5, is considered for all the simulations.…”

“…DDA has been widely used Frontiers in Earth Science frontiersin.org in various static and dynamic rock mechanics and engineering problems (Ning et al, 2017;Ning and Lv, 2022), in which rock fracturing could be successfully simulated by the sub-block element approach (Ning et al, 2011;Jiao et al, 2012;Ni et al, 2020). Ning et al (2021) also have introduced a mesoscale statistic heterogeneity model for rock based on the Weibull distribution introduced into DDA. In that work, the fracturing failure of intact heterogeneous disc and rectangular specimens under compression were comprehensively simulated to investigate the influence of heterogeneity on the fracturing failure pattern and macroscale equivalent response of intact rock.…”

Study on Freezing-Thawing Failure Process of Natural Damage Sandstone Based on Cellular Automata

“…Under long geological action and various physical and chemical actions, the internal formation of initial damage structures such as joints, cracks, pores, and discontinuous surfaces causes the heterogeneity of rocks. Heterogeneity has an important influence on the failure process, the failure mode, and the rock stress-strain relationship [1][2][3][4]. Especially in a low-temperature environment and load, the rock undergoes the elastic-plastic stage and presents discontinuous deformation after the plastic deformation reaches a certain degree.…”