Abstract
Abstract To study the shear failure modes of rock fractures with different morphologies, rock types and test conditions, direct shear tests were conducted with the aid of an acoustic emission test system to obtain the characteristics of acoustic emissions in the shear process. The test results indicated that sandstone fractures experienced brittle shear failure under higher constant normal loads (15-30 kN) and plastic shear failure under lower normal loads (5 kN and 10 kN), while the marble fracture experienced plastic shear failure under each normal load. Dropping of shear stress, sharp change from shear dilatation to shear shrinkage and sudden release of high AE energy could be found when brittle shear failure occurred in sandstone fracture under a higher normal load. Thus, combining the location evolution characteristics of acoustic emission, it can be concluded that the entire shear dislocation of sandstone fracture in brittle shear failure mode happened just after the peak under higher normal loads. However, the entire shear dislocation of sandstone fracture under lower normal loads and marble fracture under all normal loads occurred just at the beginning of the shear process.
Highlights
To study the shear failure modes of rock fractures with different morphologies, rock types and test conditions, direct shear tests were conducted with the aid of an acoustic emission test system to obtain the characteristics of acoustic emissions in the shear process
The test results indicated that sandstone fractures experienced brittle shear failure under higher constant normal loads (15-30 kN) and plastic shear failure under lower normal loads (5 kN and 10 kN), while the marble fracture experienced plastic shear failure under each normal load
Sharp change from shear dilatation to shear shrinkage and sudden release of high Acoustic emission (AE) energy could be found when brittle shear failure occurred in sandstone fracture under a higher normal load
Summary
Abstract: To study the shear failure modes of rock fractures with different morphologies, rock types and test conditions, direct shear tests were conducted with the aid of an acoustic emission test system to obtain the characteristics of acoustic emissions in the shear process. Combining the location evolution characteristics of acoustic emission, it can be concluded that the entire shear dislocation of sandstone fracture in brittle shear failure mode happened just after the peak under higher normal loads. The influences of normal stress and fracture surface morphology on the shear failure mechanism of rock fracture are not fully understood yet, meaning it is necessary to further study the shear failure mechanism of rock fracture with the help of the AE method and 3D scanning technology. Direct shear tests were conducted on sandstone and marble specimens containing a single fracture under different CNL conditions, in which the AE method was used to monitor the shear failure process of rock fracture while 3D scanning technology were used to obtain the initial 3D morphology of rock fracture surfaces
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