Controlling roof with potential rock burst risk through different pre-crack length: Mechanism and effect research

Abstract

Roof pre-splitting is an effective method to control the roof with potential rock burst risk. In this study, three-point bending tests were carried out by using fine sandstone specimens with different pre-cracked lengths as test objects, and digital speckle correlation method (DSCM) and acoustic emission (AE) technology were used to track the entire process of crack propagation. The effect of pre-cracks on the fracture of rock beams was evaluated, and the mechanical mechanism of the rock beam fracture process was analyzed. The rock beam pre-splitting design method was developed, and the application effect of the method was proved by the microseismic monitoring data obtained from the 10303 working face of Jining No. 2 coal mine in China. The results show that the loading time history curve of pre-cracked beams exhibits obvious residual characteristics. Compared with the intact rock beam, the tensile strength, and maximum tensile strain of 35 mm pre-cracked rock beam are decreased by 32.4% and 33.1%, respectively and the acoustic emission b value is increased by 30.2%. According to the pre-splitting design method of rock beam, the maximum and average microseismic energy of the 10303 working face after pre-splitting construction are reduced by 25.6% and 6.4%, respectively, with excellent prevention and control effect of thick roof.

Keywords

three-point bending / acoustic emission / roof pre-splitting / digital speckle correlation method / rock burst control

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