关键词: 岩土工程, 页岩, 声发射, 声发射事件数, 信息熵, 临界态

Abstract: In order to clearly understand the self-organized critical phenomenon of shale in the process of tension and compression fracture, uniaxial compression and Brazilian splitting tests were carried out for shale with brittle characteristics at different rates. The number of acoustic emission (AE) events in the whole process was collected synchronously. The information entropy H of AE event number was defined by combining information entropy theory with AE event number, and the evolution law of AE event number in the process of loading was obtained. The research results show that under the tension and pressure conditions, the information entropy of AE events increases with time, and the law is similar. When the information entropy of AE events keeps stable (r≈0.95), the rock enters the critical state. According to the acoustic emission localization map, the entropy value is maximum when the critical point is reached, and the penetrating crack begins to form. After entering the critical state, the entropy value is in steady a state, and the location signals gather towards the fracture area until the failure. Through the acoustic emission localization changes of four states, the evolution process of defects in shale from the disordered state of slow random development to the orderly state of instantaneous development according to certain laws is revealed, which is well corresponding to the entropy change. The energy probability density function satisfies the power law distribution (P≈X-r) in the process of tension and compression, which has a similar critical index.

Key words: geotechnical engineering, shale, acoustic emission, the number of acoustic emission events, information entropy, critical state