Mechanical Properties and Energy Analysis of Rock under Different Unloading Confining Pressures
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Yi Luo, Yiping Zhang
In order to study the mechanical properties and energy characteristics of rock under different unloading confining pressures, the triaxial unloading confining pressure of granite was studied by MTS815 rock mechanics test system; and the curve deformation characteristics of whole process of rock stress-strain under different unloading conditions and the energy dissipation law of the rock specimen in unloading and confining failure process were analyzed. The results show that the granite fracture is dominated by shear failure under the conventional triaxial path and the macroscopic cracks generated by rock specimen failure under low confining pressure are significantly more than the high confining stress state; the circumferential hazard and volumetric strain of rock during unloading confining pressure has a linear relationship with the confining pressure in the initial stage, and then changes into a significant nonlinear relationship; Under the unloading confining pressure condition, the rock also has strain softening characteristics and fracture expansion characteristics after yield failure; the elastic modulus hardly changes in the initial stage and is greatly reduced after the break point; the elastic strain energy that can be released increases slowly in the initial stage, and increases sharply when the confining pressure decreases to a certain extent; the initial confining pressure on the axial strain energy, the circumferential expansion capacity and the degree of influence of elastic strain energy is significantly greater than that of the unloading path, and both increase approximately linearly with the increase of initial confining pressure. The study results of this paper provide a reference for further research on rock mechanics and energy properties under unloading confining pressure.
Rock mechanics, Triaxial unloading test, Rock mechanical properties, Rock energy properties