Damage Constitutive Model Of Rock Research Articles

Numerical simulation of rock fracturing under uniaxial compression using virtual internal bond model

A multi-scale virtual internal bond (VIB) model for the isotropic materials has been recently proposed to describe the material deformation and fracturing. During the simulation process of material fracturing using VIB, the fracture criterion is directly built into the constitutive formulation of the material using the cohesive force law. Enlightened by the similarity of the damage constitutive model of rock under uniaxial compression and the cohesive force law of VIB, a VIB density function of rock under uniaxial compression is suggested. The elastic modulus tensor is formulated on the basis of the density function. Thus the complete deformation process of rock under the uniaxial compression is simulated.

Numerical analysis of blast-induced wave propagation and spalling damage in a rock plate

The paper focuses on the numerical analysis of blast-induced stress wave propagation and related spalling damage in a rock plate or wall. Firstly, a large-scale contact explosion is simplified as a one-dimensional (1-D) strain problem, and a cross-format centered finite-difference scheme is presented. Secondly, the finite-difference code is used to explore the wave propagation in a rock plate, and compared with the commercial software LS-DYNA. Thirdly, a continuum damage constitutive model for rock is introduced and successfully incorporated into the LS-DYNA through its user-defined subroutine. Coupling with the erosion technique, the improved LS-DYNA is used to simulate the blast-induced spalling damage at the back-side of rock plate. Numerical results show that the 1-D finite difference code is convenient and accurate. Also, the user-defined subroutine can well describe the process of spalling damage.

Damage constitutive model for strain-softening rock based on normal distribution and its parameter determination

Firstly, using the damage model for rock based on Lemaitre hypothesis about strain equivalence, a new technique for measuring strength of rock micro-cells by adopting the Mohr-Coulomb criterion was developed, and a statistical damage evolution equation was established based on the property that strength of micro-cells is consistent with normal distribution function, through discussing the characteristics of random distributions for strength of micro-cells, then a statistical damage constitutive model that can simulate the full process of rock strain softening under specific confining pressure was set up. Secondly, a new method to determine the model parameters which can be applied to the situations under different confining pressures was proposed, by deeply studying the relations between the model parameters and characteristic parameters of the full stress-strain curve under different confining pressures. Therefore, a unified statistical damage constitutive model for rock softening which can reflect the effect of different confining pressures was set up. This model makes the physical property of model parameters explicit, contains only conventional mechanical parameters, and leads its application more convenient. Finally, the rationality of this model and its parameters-determining method were identified via comparative analyses between theoretical and experimental curves.

Geometric analysis of damaged microcracking in granites

Practically identical samples are tested at the same confining pressure and temperature but at different deviatoric stress levels. Thin sections are observed using an optical microscope and recorded as images in order to study the crack network evolution. The compound cracks are decomposed into elementary cracks (right segments) with constant orientation and then reassembled in order to determine crack length and cumulated crack length. The results of crack observations are discussed in the light of the mechanisms of crack evolution at microscopic level compared to the stress–strain curves. It results from our observations that mean crack length increases only moderately in comparison with maximal crack length and the number of cracks. Zhao reports similar results (cf. Zhao, Y., 1998. Crack pattern evolution and a fractal damage constitutive model for rock. Int. J. Rock. Mech. Min. Sci. 35 (3), 349–366). The evolution of microcracking can be attributed more to new crack nucleation rather than to growth of the pre-existing cracks.

Crack pattern evolution and a fractal damage constitutive model for rock

To understand the deformation and fracture behavior of rock, it is useful to observe the variation of cracks in rock, and characterize the crack pattern as well as deduce a constitutive model. In this study, the development of microcracks on the surface of rock specimens under increasing stress is monitored under direct SEM observation. The initiation, extension and coalescence of cracks are photographed and then analyzed. The Box fractal dimension of cracks and its variation with stress level for a small unit of specimen is determined. Based on the test results, a fractal damage constitutive relation for the deformation and brittle fracture of rock materials is proposed. The damage variables are defined according to the fractal characteristics of microcracks and microcavities in rock media. The evolution equations for both isotropic and anisotropic damage variables are derived. Predictions of a uniaxial compression test on Fangshan marble are found to agree with the experimental results.