Abstract
In order to study the coal deformation and failure mechanism in fully mechanized caving face under the high-intensity mining, based on the equivalent mechanical model of transversely isotropic cylindrical coal with fractures, the equivalent equations for axial, radial, and volume strains of coal sample loaded in linear elastic and plastic stages were derived in this paper. The equivalent mechanical model shows good reliability through the conventional triaxial experiment. Taking the N1206 workface in Yuwu coal mine of Luan group as the example, we have simulated the stress concentration factor of the coal body ahead of the working face with FLAC and divided three regions according to stress distribution in coal mining. Mathematical equations were derived to express the horizontal and vertical stress, which provide theoretical guidance of the stress paths in triaxial experiment about real mining stress environment simulation. Experimental results show that the volume strain’s value is about 0.4% in the coal mass deformation progress of axial compression increasing slowly area. In axial compression increasing rapidly area, the volume strain’s value varies from 0.41% to 0.27%, and the radical strain changes from compression deformation to expansion deformation gradually. The volume strain of coal sample increases sharply in axial compression releasing rapidly area; meanwhile, there are good linear relationships between Poisson’s ratio and axial strain and radial strain.
Highlights
China’s coal seam gas is richly endowed, and its reserves are roughly comparable to those of natural gas
Xie et al [9] studied the distribution law of mining-induced stress of Advances in Civil Engineering coal body ahead of fully mechanized caving by establishing a mechanical model of coal body damage in working face. e isotropic damage model established by Hansen and Schreyer [10, 11] was used to study the damage characteristics of coal body
Su and Huang et al [15, 16] simulated the in situ stress field through deformation and failure tests of coal samples under different stress paths, and the deformation and failure laws of coal body ahead of the working face were studied
Summary
China’s coal seam gas is richly endowed, and its reserves are roughly comparable to those of natural gas. Intensive study on the deformation and failure mechanism of coal body ahead of fully mechanized caving face is helpful to make the corresponding fracture and seepage fields of coal body clear [4,5,6] It has important theoretical guiding significance and engineering application value for the gas control and coal and gas outburst prevention in high gas working face [7, 8]. Due to the differences between the loading and unloading paths of triaxial test and the real stress state of coal body ahead of the working face, how to improve the accuracy of the test and quantitatively judge the deformation of coal body still needs to lucubrate, especially for the deformation characteristics study of coal body ahead of fully mechanized caving face under high-intensity mining condition. According to the real working face stress distribution in different stages, the GCTS triaxial instrument is used to load and unload simultaneously the axial pressure and confining pressure to the coal sample. e deformation characteristics of coal body and the development of fractures under the real stress environment of fully mechanized caving face are emphatically studied. e research results provide a reference for the study of coal and gas solid-gas coupling law, which is of great significance to realize the comining of coal and gas in the high-strength fully mechanized caving face
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