[Lin, Hang; Liu, Taoying; Cao, Ping; Pu, Chengzhi] Cent S Univ, Sch Resources & Safety Engn, Changsha 410083, Hunan, Peoples R China.;[Liu, Taoying; Pu, Chengzhi] Univ South China, Nucl Resource Coll Engn, Hengyang 421001, Hunan, Peoples R China.
[Liu, Taoying] Cent S Univ, Sch Resources & Safety Engn, Changsha 410083, Hunan, Peoples R China.
Rock-like material;Multiple pre-existing flaws;Crack propagation and coalescence;Uniaxial compression
Fracture coalescence, which plays an important role in the behavior of brittle materials, is investigated by loading rock-like specimens with two and three pre-existing flaws made by pulling out the embedded metal inserts in the pre-cured period. Different geometries are obtained by changing the angle of the flaws with respect to the direction of loading and the spacing. With reference to the experimental observation of crack initiation and propagation from pre-existing flaws, the influences of the third pre-existing flaw on the cracking processes was analyzed. It was found during the test that: with the increase of the angle of the rock bridge, the rock specimen takes a turn from wing crack propagation failure to crack coalescence failure, and it will be more obvious with the increase of the prefabricated crack angle. According to the different geometries of pre-existing cracks, seven types of coalescence have been identified based on the nature of the cracks for the specimen with two pre-existing flaws. The multi-crack interaction results in the continuous degradation of the macroscopic mechanical properties of the rock mass. On one hand, it weakens the trend of relative sliding of the coplanar cracks, and on the other hand, it changed the coalescence patterns of the fractured specimen. The research reported here provides increased understanding of the fundamental nature of rock mass failure in compression. (C) 2014 Elsevier B.V. All rights reserved.
The rockburst is a severe underground geological disaster, which has great damage to the workers, equipments and engineering structures. This paper aims to find a suitable way to assess the risk of rockburst within complicated decision making circumstances. First, plenty of literature related to the risk assessment indexes and methods of rockburst is reviewed. On account of the specific characteristics of rockburst, both quantitative and qualitative evaluation indexes are recognized in this paper. Owing to the fuzziness of human thinking and the complexity of risk assessment problems, triangular fuzzy numbers (TFNs) are advised to describe these indexes values. Meanwhile, the superiority linguistic ratings of decision makers (DMs) are used to determine the weights of indexes. After that, an extended multi-attributive border approximation area comparison (MABAC) method corresponding to TFNs is put forward to obtain the ranking results and specific risk levels of rockburst under fuzzy environment. Finally, an example of assessing the risk of rockburst in Kaiyang phosphate mine is illustrated. The rockburst proneness of four crucial areas is evaluated with the proposed method, and the ranking result is consistent with the field status. Besides, the effectiveness of this method is demonstrated with parameter and comparison analyses. The results show that the extended MABAC method is reliable and effective for evaluating the risk of rockburst, and provides references for the prevention and management of rockburst.