A new statistical damage model for true triaxial pre-and post-peak behaviors of rock considering intermediate principal stress and initial compaction effects

Abstract

Deep underground engineering excavation will induce complex change in the true three-dimensional stress state of the surrounding rock, causing rock damage and then leading to a change in mechanical properties. In this research, the true triaxial compression tests are conducted to study the influence of σ2 and σ3 on the mechanical properties of marble, such as the characteristic strength (crack initiation stress σci, damage stress σcd, peak strength σp, and residual strength σr), post-peak deformation, ductility and brittleness. The peak strength σp, crack initiation stress σci and damage stress σcd of rock increase with the increase in σ2, while the variation of residual strength σr with σ2 is different from that of peak strength. As σ2 increases or σ3 decreases, the pre-peak plasticity of the rock decreases, the post-peak curve shape of the rock changes significantly, and the overall shape of the post-peak curve transforms from Class I to Class II. The Mogi-Coulomb strength criterion with intermediate principal stress effect was used to characterize the rock microelement strength, and then the new statistical damage constitutive model considering the initial compaction effect and damage threshold was proposed, and the model validation was carried out based on the experimental results and the effects of the proposed model parameters m and F0 on the rock strength and post-peak curve morphology were further explored.

Seepage-stress combined experiment and damage model of rock in different loading and unloading paths

“…Various defects inside the rock lead to its own destruction with great randomness. The Weibull distribution law (Tang et al., 2000; Weibull, 1951; Zheng et al., 2023d) can better reflect the random failure of rocks, and it is assumed that the probability density function of its failure is: …”

“…(2019) complement previous scholars' research by establishing a micromechanical model. Research scholars (Chen, 2020; Shen et al., 2012; Wang and Ma, 2022; Zheng et al., 2023b, 2023c, 2023e) established a model combining the two kinds of mechanics by analyzing the macro mechanics and micro mechanics of materials, and supplemented the limitations of the above two theories. Zhu (2017) established a new damage micromechanical constitutive model of porous rock based on the continuum micromechanics and thermodynamics theory by eliminating the porosity, initial porosity and the generation of new cracks in the rock, that is, the expression of the three-phase system material of rock skeleton, quasi-brittle rock material.…”

A thermodynamic damage model for 3D stress-induced mechanical characteristics and brittle–ductile transition of rock

“…After excavation of deep underground engineering, complex stress redistribution occurs inside surrounding rock, and rock is damaged or even destroyed (Feng et al, 2019;Hoek et al, 1995;Hudson, 1972;Kaiser, 2010;Xie et al, 2022), which will reduce the stability of surrounding rock and even cause a series of engineering disasters such as rockburst and spalling, and threat engineering safety (Gao and Wang, 2021;He et al, 2021;Zhao et al, 2022). Previous researches on mechanical properties and mechanical models of rock based on conventional triaxial compression play an important role in the excavation and support of underground engineering (Al-Shayea and Mohib, 2011;Tian et al, 2021;Wang et al, 2014;Yang et al, 2019Yang et al, , 2021Zheng et al, 2022e). However, unlike ground and shallow rocks which are in conventional triaxial stress (r 1 > r 2 ¼ r 3 ), deeply buried engineering rocks are in true triaxial stresses (r 1 > r 2 > r 3 ), the intermediate principal stress and minimum principal stress have obvious effects on strength, deformation and brittleductile transition behaviour of rock, which are not completely clear, and the mechanical model reflecting such mechanical properties and relations is lack for stability analysis of deep underground engineering, which is the important factor of frequent occurrence of deep underground engineering accidents.…”