Numerical study on the effect of sudden change in coal property on coal and gas outburst during roadway excavation

Tang, Wei; Zhai, Cheng; Yu, Xu; Xu, Jizhao; Sun, Yong; Cong, Yuzhou; Zheng, Yangfeng; Li, Yujie

doi:10.1007/s12665-022-10445-2

Cited by 1 publication

(2 citation statements)

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Section: Methodsmentioning

confidence: 72%

“…Figure 2 depicts the stress distribution affecting the gas drainage borehole, namely the three-dimensional spatial structure of the intersection of the gas drainage borehole and the roadway, forming a stress reduction area, a stress concentration area, and an original rock stress area. These three areas of stress correspond to the stress distribution presented in [23]. The formation of the three-dimensional spatial structure at the intersection of the gas drainage borehole and the roadway is divided into two steps: the first step is to subject the coal seam to in-situ stress and then redistribute the spatial stress of the surrounding rock via the excavation roadway; the second step is to drill a drainage hole in the surrounding rock coal seam to redistribute the stress.…”

Section: Methodsmentioning

confidence: 96%

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Seepage Law of Nearly Flat Coal Seam Based on Three-Dimensional Structure of Borehole and the Deep Soft Rock Roadway Intersection

Zhang

Jing²,

et al. 2022

Energies

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Exploring the evolution characteristics of gas seepage between boreholes during the drainage process is critical for the borehole’s layout and high-efficiency gas drainage. Based on the dual-porous medium assumption and considering the effect of stress redistribution on coal seam gas seepage characteristics, a coal seam gas seepage model with a three-dimensional roadway and borehole crossing structure has been established and numerically calculated, concluding that the coal seam is between the drainage boreholes. The temporal and spatial evolution characteristics of gas pressure and permeability help elucidate the gas seepage law of the nearly flat coal seam associated with the deep soft rock roadway and borehole intersection model. The results indicate that: (1) The roadway excavation results in localized stress in some areas of the surrounding rock, reducing the strength of the coal body, increasing the expansion stress, and increasing the adsorption of gas by the coal body. (2) Along the direction of the coal seam, the permeability decreases initially and then increases. The gas pressure in the coal seam area in the middle of the borehole is higher than the pressure in the coal seam around the borehole, and the expansion stress and deformation increase, reducing the permeability of the coal body; when near the next borehole, the greater the negative pressure, the faster the desorption of the gas attracts the matrix shrinkage effect and causes the coal seam permeability rate to keep increasing. (3) The improvement of gas drainage with the overlapping arrangement of two boreholes firstly increases and then decreases as time goes on. (4) When the field test results and numerical simulation of the effective area of gas extraction are compared, the effectiveness of the model is verified. Taking the change of the porosity and the permeability into the model, it is able to calculate the radius of gas drainage more accurately.

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Section: Methodsmentioning

confidence: 72%

Section: Methodsmentioning

confidence: 96%