Experimental study on mechanical response and seepage characteristics of broken coal under true triaxial stress conditions

doi:10.16265/j.cnki.issn1003-3033.2023.06.1428

Abstract

Abstract:

In order to investigate the mechanical response and seepage characteristics of coal in broken areas during deep underground coal mining, the multi-functional true triaxial fluid-solid coupling apparatus was used. The distribution of internal fractures of broken coal after failure was detected and analyzed by using the computed tomography (CT) scanning system. The strength characteristics, permeability evolution, and failure modes of broken coal under different intermediate principal stresses were obtained. The research results show that broken coal presents brittle-ductile failure characteristics under true triaxial stress conditions, and the peak strength shows an ascending-then-descending trend with the increase of intermediate principal stresses. The permeability of the broken coal body does not increase significantly before failure and continues to decrease at the post-peak stage. Furthermore, the permeability varies more at the pre-peak stage. The macro-fracture forms of broken coal after failure are mainly shear fractures, and the macro-shear failure plane presents asymmetrical distribution characteristics. In order to ensure the safe mining of deep coal, attention should be paid to the change of tectonic stress and fracture structure in the broken coal seam area on site, and the gas drainage in the broken coal seam area or the grouting reinforcement scheme for the broken coal rock roadway should be adjusted.

Key words: true triaxial stress, broken coal, mechanical response, seepage characteristic

LIU Yubing, WANG Enyuan, ZHANG Dongming, LI Minghui. Experimental study on mechanical response and seepage characteristics of broken coal under true triaxial stress conditions[J]. China Safety Science Journal, 2023, 33(6): 105-113.

Figures/Tables 12

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σ₂ / MPa	k₀ / (×10^-2 μm²)	峰值强度渗透率 k_p/(×10^-2μm²)	残余强度渗透率 k_r//(×10^-2μm²)
15	4.11	0.54	1.04
20	12.44	6.74	5.51
25	3.50	1.97	1.56
30	5.94	2.91	1.53

σ₂/MPa	D	R²
15	1.34	0.94
20	1.57	0.92
25	1.42	0.93
30	1.33	0.90