Abstract
Deep brittle rock exhibits characteristics of rapid stress dropping rate and large stress dropping degree after peak failure. To simulate the whole process of deformation and failure of the deep brittle rock under load, the Lemaitre strain equivalent theory is modified to make the damaged part of the rock has residual stress. Based on the damage constitutive model considering residual strength characteristics, a correction factor reflecting stress dropping rate is added, the Weibull distribution is used to describe the inhomogeneity of rock materials, and Drucker–Prager criterion is used to quantitatively describe the influence of stress on damage; a damage constitutive model of deep brittle rock considering stress dropping characteristics is established. According to the geometric features of the rock stress-strain curve, the theoretical expressions of model parameters are derived. To verify the rationality of the model, triaxial compression experiments of deep brittle rock under different confining pressures are conducted. And the influence of model parameters on rock mechanical behaviour is analysed. The results show that the model reflects the stress dropping characteristics of deep brittle rock and the theoretical curve is in good agreement with the experimental results, which indicates that the proposed constitutive model is scientific and feasible.
Highlights
With the reduction of mining resources in the shallow strata of the world, the mining depth of resources is gradually increased [1, 2]
In order to meet the needs of production and life, China has proposed the “deep earth” strategy during the 13th Five-Year period. e number and scale of deep rock engineering will increase significantly in the future [3, 4]. e deep rock is in the deep stratum, and its internal damage is continuously generated and developed under the action of external high stress, and it still has a certain bearing capacity after the peak failure [5]. erefore, the whole process of deep rock failure under load is studied, and the stress dropping characteristics in the postpeak stage are analysed, which provides an important theoretical model for the construction of deep rock engineering
Yang et al [7] carried out a series of postpeak cyclic loading and unloading experiments on sandstone to study the mechanical behaviour, deterioration parameters, energy indexes, and failure modes of rock samples in the postpeak stage
Summary
With the reduction of mining resources in the shallow strata of the world, the mining depth of resources is gradually increased [1, 2]. Cao et al [14] established a statistical damage constitutive model that can simulate the characteristics of the whole process of rock deformation, which can reflect the residual strength of the rock in the postpeak stage. Cao et al [15] considered the residual strength of rock in the postpeak stage, modified the damage variable, and established a statistical damage constitutive model, which can describe the stress-strain relationship and residual strength of rock. Substituting equation (9) into equation (5) and the damage constitutive model considering residual strength characteristics can be obtained as follows: σ1 Eε1(1 − D) + N D + μ σ2 + σ3,. Combining equations (16) and (17), a damage constitutive model considering the characteristics of stress dropping rate and residual strength is obtained: σ1.
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