Abstract
Research on the damage and seepage characteristics of unloading rock with high water pressure can help to further understand the mechanism of water inrush in deep mine and to take effective measures to prevent water inrush. In this paper, the finite element software RFPA2D-Flow was used to study the failure and seepage characteristics of unloading rock coupled with high water pressure and high stress. The effects of different water pressure on the failure of unloading rock and the law of seepage were investigated. The results show that the form of unloading rock failure without water pressure is brittle; however, the failure form of unloading rock with water pressure is obviously ductile failure, and the fracture is mainly concentrated at the bottom of the rock sample with high water pressure. During unloading, the seepage coefficient of rock increased with the increase of unloading amount until sudden jump occurs, and the failure form and permeability law of the rock with different water pressure were basically the same, but the larger the water pressure difference, the smaller the effective unloading capacity is needed when the permeability coefficient suddenly jumps, this shows that the larger the water pressure difference is, the more likely the rock mass will be damaged by water inrush under unloading condition.
Highlights
From the perspective of the nature of mechanics, the excavation and support of underground engineering belong to a category of alternating loading and unloading mechanics
Guo [7] adopted the COMSOL software to establish the Darcy-and-non-Darcy-and-free-flow equation before and after the fault over-break in the stages of aquifer, fault and working face, obtaining the fault water inrush and current flow mechanism under the effect of stress and water pressure .Zhang [8] adopted the FLAC 3D numerical software to investigate the formation and evolution of water-inrush channel advancing with workface in high water pressure mining
When the p4 is 6MPa, 8MPa, 10MPa, the permeability coefficient is basically 0.0178 m/d at the initial stage of unloading, and the permeability coefficient after failure is 0.149 m/d, 0.1512 m/d, 0.2343 m/d, respectively. It is 8.37 times, 8.51 times, 13.16 times the original. It indicates that with the increase of water pressure difference, the change of permeability coefficient increases with the failure of rock
Summary
The sample with its brittleness and ductility during the full stress-strain process and the relationship between the permeability and the axial strain and volume strain. Liu [4] took raw coal as the research object and carried out post-peak confining pressure unloading test. The study found that when the axial pressure after the peak is unchanged and the confining pressure is unloaded, the coal sample permeability becomes larger and larger. Zhang [6] analyzed the influence of different unloading rates on the strength of rock samples through 2D elastic-plastic cellular automata numerical test and unloading confining pressure test. In order to be consistent with the actual, in this paper, considering the influence of water pressure difference on confining pressure unloading rock, RFPA2D-flow software is used to analyze and study the strength characteristics and failure evolution of confining pressure unloading rock with different water pressure difference
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