Abstract
In order to study the mechanical characteristics and cracking behavior of jointed rock mass under hydro-mechanical coupling, a series of uniaxial compression tests and triaxial compression tests were carried out on cylinder gypsum specimens with a single pre-existing flaw. Under different confining pressures, water pressure was injected on the pre-existing flaw surface through a water injection channel. The geometrical morphology and tensile or shear properties of the cracks were determined by X-ray computed tomography (CT) and scanning electron microscope (SEM). Based on the macro and micro observation, nine types of cracks that caused the specimen failure are summarized. The results of mechanical properties and crack behavior showed that the confining pressure inhibited the tensile cracks, and shear failure occurred under high confining pressure. The water pressure facilitated the initiation and extension of tensile crack, which made the specimens prone to tensile failure. However, under the condition of high confining pressure and low water pressure, the lubrication effect had a significant effect on the failure pattern, under which the specimens were prone to shear failure. This experimental research on mechanical properties and cracking behavior under hydro-mechanical coupling is expected to increase its fundamental understanding.
Highlights
Hydro-mechanical coupling effect should be considered in rock engineering, petroleum extraction, and enhanced geothermal exploitation
This section discusses the results of the axial stress–strain response, peak deviator stress, and the deformation characteristics obtained in the uniaxial compression test, conventional triaxial compression test, and hydraulic coupled triaxial test
With the increase of confining pressure, the failure mode of specimens transferred to ductile failure, and with the increase of water pressure, the failure mode changed to brittle failure
Summary
Hydro-mechanical coupling effect should be considered in rock engineering, petroleum extraction, and enhanced geothermal exploitation. The mechanical properties and cracking behavior of rock mass under hydro-mechanical coupling have not been comprehensively understood. A series of related researches have been conducted to investigate the basic failure mechanism of jointed rock mass [1,2,3,4,5,6,7]. Scholars have summarized the crack types of fractured rock mass under uniaxial compression, and crack types initiated from the pre-existing flaws have been proposed.
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