Numerical simulation of mechanisms of deformation, failure and energy dissipation in porous rock media subjected to wave stresses

Abstract

The pore characteristics, mineral compositions, physical and mechanical properties of the subarkose sandstones were acquired by means of CT scan, X-ray diffraction and physical tests. A few physical models possessing the same pore characteristics and matrix properties but different porosities compared to the natural sandstones were developed. The 3D finite element models of the rock media with varied porosities were established based on the CT image processing of the physical models and the MIMICS software platform. The failure processes of the porous rock media loaded by the split Hopkinson pressure bar (SHPB) were simulated by satisfying the elastic wave propagation theory. The dynamic responses, stress transition, deformation and failure mechanisms of the porous rock media subjected to the wave stresses were analyzed. It is shown that an explicit and quantitative analysis of the stress, strain and deformation and failure mechanisms of porous rocks under the wave stresses can be achieved by using the developed 3D finite element models. With applied wave stresses of certain amplitude and velocity, no evident pore deformation was observed for the rock media with a porosity less than 15%. The deformation is dominantly the combination of microplasticity (shear strain), cracking (tensile strain) of matrix and coalescence of the cracked regions around pores. Shear stresses lead to microplasticity, while tensile stresses result in cracking of the matrix. Cracking and coalescence of the matrix elements in the neighborhood of pores resulted from the high transverse tensile stress or tensile strain which exceeded the threshold values. The simulation results of stress wave propagation, deformation and failure mechanisms and energy dissipation in porous rock media were in good agreement with the physical tests. The present study provides a reference for analyzing the intrinsic mechanisms of the complex dynamic response, stress transit mode, deformation and failure mechanisms and the disaster mechanisms of rock media. porous media, three-dimensional finite element model, rock media, stress wave, failure mechanism, energy dissipation Citation: JU Y, Wang H J, Yang Y M, et al. Numerical simulation of mechanisms of deformation, failure and energy dissipation in porous rock media subjected to wave stresses.

Energy Evolution Characteristics and Distribution Laws of Rock Materials under Triaxial Cyclic Loading and Unloading Compression

“…Yang et al conducted triaxial compression experiments on tight sandstone to analyze the relationships among elastic energy density, dissipated energy density, and confining pressure [25]. Ju et al studied the influence of porosity on rock energy dissipation and the energy dissipation situation during critical rock failure through methods of experiment and numerical simulation [26]. Under the same impact rate, with an increase of porosity of the rock, the energy dissipated by the rock increased, and the energy dissipated by critical failure decreased.…”

Computation of fractal dimension of rock pores based on gray CT images

“…Hence steady progress has been made in two areas, specifically the mechanism of evolving defects or cracks and the elucidation of damage constitutive relationships. Ju et al [20][21][22] investigated the geometric features and distribution properties of pores in rocks by means of CT scanning tests of sandstone and foam concrete, and then constructed a statistical model of rock pore structure that was used in numerical simulation by finite-element software. The results indicated the important role of CT technology for researching microscopic damage of rock materials.…”

Energy analysis for damage and catastrophic failure of rocks

“…Some consistent conclusions are made: Rock fracturing is generally accompanied by strong acoustic emission; the strain increase is accompanied by decreasing infrared radiation intensity, electromagnetic radiation intensity and temperature after fracturing; before rock fracturing under compression, acoustic emission signal is weak while the infrared radiation intensity, electromagnetic radiation intensity and temperature would rise [1][2][3][4][5][6][7][8][9][10][11][12]. Some experimental studies [17] have shown that the change of material temperature or infrared radiation intensity is related to the volumetric strain.…”

“…In the past decades, many efforts have been dedicated to these fields and some valuable results have been achieved [1][2][3][4][5][6][7][8][9][10][11][12]. On the other hand, as catastrophic failure of underground structures received particular attention [13][14][15][16] in engineering, it has become the focus of studies on how the underground structure and the surrounding materials gradually damage, yield, fracture and fail under various excavation and construction conditions.…”