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The inclination angle of the flaw has an important effect on the cracking behavior of fractured rock. The influence of the inclination angle of closed flaw on the strength, cracking behavior, failure modes, and AE behaviors of specimens has not been investigated thoroughly. Uniaxial compression tests were conducted on gypsum samples containing a single closed flaw with different inclination angles. The flaw orientation influence on strength, cracking mechanism, failure modes, and AE behaviors was analyzed in detail. With the increase of the flaw inclination angle from 30° to 75°, the mechanical parameters such as elastic modulus, wing crack initiation strength, and uniaxial compression strength decrease first and then increase and reach the minimum value at 45°. The wing crack initiation angle decreases from 65° to 35° as the flaw inclination angle increases from 30° to 75°. The wing crack is more difficult to initiate from the tips of closed flaws compared with that of open flaws. The secondary cracks are initially shear cracks and propagate in a stable manner. However,when the axial stress reaches the peak strength, the secondary crack propagates unstably, which results in the macroscopic failure of the sample. The AE behaviors of samples are also analyzed during the uniaxial compression test. The experimental results are expected to provide helpful guidance for safe construction under fractured rock mass condition.

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