Effects of the Deviatoric Stress Ratio on the Coal Failure and Permeability During Deep Mining
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ORIGINAL PAPER
Effects of the Deviatoric Stress Ratio on the Coal Failure and Permeability During Deep Mining Chao Xu . Qiang Fu . Kai Wang . Chaofei Guo . Xiaofang Li
Received: 12 April 2020 / Accepted: 10 June 2020 Ó Springer Nature Switzerland AG 2020
Abstract Practices show that the triaxial stress change of mining-disturbed coal deeply affects its failure and permeability characteristics and easily cause the coal and rock dynamic disasters during deep underground mining process. The combined mechanic-damage-permeability experiments of gasbearing coal were carried out under the mechanical paths of conventional triaxial compression (CTC), fixing axial pressure and unloading confining pressure (FAPUCP) and loading axial pressure and unloading confining pressure (LAPUCP). Then the effects of the deviatoric stress ratio (DSR) on the damage and permeability characteristics of coal were analyzed. The results proved that the distinguishing deformation and strength characteristics of coal were showed due to the different mechanical paths and the coal specimens were converted from brittle deformation to plastic deformation with the effect of higher confining C. Xu Q. Fu K. Wang C. Guo X. Li Beijing Key Laboratory for Precise Mining of Intergrown Energy and Resources, China University of Mining and Technology-Beijing, Beijing 100083, China C. Xu Q. Fu K. Wang (&) C. Guo X. Li School of Emergency Management and Safety Engineering, China University of Mining and Technology-Beijing, Beijing 100083, China e-mail: [email protected] C. Xu Yangquan Coal Industry (Group) Co., Ltd., Yangquan 045000, China
pressure. The coal specimens of the three mechanical paths generated the main shear failure, tensile-shear failure and ‘X’ conjugate shear failure, respectively, and the fracture angles decreased in order. The damage and permeability of coal specimens could be more and more severe in the order of CTC, FAPUCP and LAPUCP paths, which was due to the different DSR. Thus, the deep mining-disturbed coal of lager DSR is seriously prone to cause the coal and rock dynamic disasters. The corresponding measures should be taken to reduce the DSR of miningdisturbed coal and then avoid the dynamic disasters. Keywords Coal mining Coal and rock dynamic disaster Deviatoric stress ratio Coal failure Permeability
1 Introduction China is the major coal producer and consumer in the world (Li et al. 2015). The coal mining depth grows larger at an average rate of 10 * 25 m per year with the rapid economic development and large energy demand in China (Kong et al. 2014). According to a variety of figures, over 50 coal mines in China are of the mining depth of greater than 1000 m to date, of which the Suncun coal mine in Shandong Province, Eastern China, is more than 1500 m in mining depth (Xie et al. 2017).
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Geotech Geol Eng
The deep coal and rock mass would suffer from the process of repeatedly loading and unloading, compared with the shallow. With the combined effects
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