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Acoustic emission characteristics and damage law for prefabricated single‐crack sandstone under uniaxial compression

The cracks of rock seriously threaten the safety of building structures and underground space. Uniaxial compression tests were carried out on prefabricated single‐crack sandstone samples with different angles and lengths. The results show that the existence of a prefabricated single‐crack has a certain influence on the mechanical properties and acoustic emission response characteristics of sandstone samples. A function formula of the effect of uniaxial compression stress on the angle and length of prefabricated crack is established. It is found that there is an obvious moment of acoustic emission energy mutation in the three deformation and failure stages before sandstone failure. The change of angle and length of crack has a great influence on the stress value corresponding to the energy mutation at the stable development stage of the micro‐crack. Meanwhile, the acoustic emission waveform characteristic parameters of sandstone samples under various fracture conditions are analyzed. Thus, the crack propagation mode of the sample with small angle can be judged. The damage variables based on real‐time acoustic emission energy were defined, and the damage constitutive model of rock material with a single fracture under uniaxial compression was established based on real‐time acoustic emission energy. The results show that the new model and method can not only reasonably explain the damage mechanism of prefabricated rock with a single fracture under uniaxial compression but also accurately simulate the full stress‐strain process of rock with a single fracture at different angles and lengths, which has good rationality and feasibility.