Evaluation of the remote lower protective seam mining for coal mine gas control: A typical case study from the Zhuxianzhuang Coal Mine, Huaibei Coalfield, China

Abstract

a b s t r a c tThe protective seam mining technology is the most effective and economical method in realizing the safe mining of outburst-prone coal seams. To study the effects of remote lower protective seam mining on coal mine gas control, a typical case (average layer spacing: 78 m) taken from the Zhuxianzhuang Coal Mine was investigated by a comprehensive evaluation through numerical simulation, gas extraction data statistics, residual gas pressure/content measurements and recovering gas emission analysis. The results indicate that after the recovery of the protective seam, the unloading effects could lead to a maximum expansion deformation rate of the protected seam by 33.4‰, which remarkably increases the permeability of the coal seam by 4320 times. Combining with the pressure-relief gas extraction methods, considerable amount of the gas (about 78.58%) was extracted from the protected seam, resulting in the maximum residual gas pressure and content of 0.26 MPa and 4.29 m 3 /t respectively, which indicate that the outburst risk has been completely eliminated. Additionally, among the gas extraction methods, the penetrating borehole extraction presents the best drainage effect, accounting for 42.58%e55.09% of the total extracted pressure-relief gas. The effect of the surface wells extraction is closely related to the number of wells and whether the wells can work properly or not. However, the effect of interception boreholes extraction is poor and the extracted amount is almost negligible. Moreover, a protected range extension phenomenon is noticed, which demonstrate that the protected area generated by the protective seam mining is larger than that of the theoretical predicted one, and thus a further study is needed.

Influence radius of gas extraction borehole in an anisotropic coal seam: Underground in‐situ measurement and modeling

“…1,3,4 Therefore, controlling methane emissions in coal mines becomes very important for controlling the greenhouse emission in coal industry. [7][8][9][10][11][12] When the concentration of methane is in the explosive range between 5% and 15% in underground roadways, the CMM can be easily ignited resulting in methane explosions. 2 Potential usage of the CMM exists in the following areas such as fuel in boilers, steel furnace, and turbines for power generation, injection gas to natural gas pipelines, and vehicle fuel.…”

“…A proper CMM control system can not only enhance coal productions because of less frequent mining downtime and production slowdown caused by a higher methane concentration in underground entries and working face but also improve the mining safety by eliminating the coal and gas outburst risk of coal seam from a lower CMM content (pressure) in coal seams. [7][8][9][10][11][12] When the concentration of methane is in the explosive range between 5% and 15% in underground roadways, the CMM can be easily ignited resulting in methane explosions. 6 Collectively, the CMM control in underground coal mines is an important step to meet the challenge of climate change, diverse energy supplies and enhance the safety performance and mining management.…”

Simulation of Ground Stress Field and Advanced Prediction of Gas Outburst Risks in the Non-Mining Area of Xinjing Mine, China

“…The main purpose of this technology is to promote stress release and crack development in the protected layer, which favors gas extraction. This approach is the most effective and economical method for preventing coal and gas outburst risks, and includes a far-distance protection layer, a self-protection layer made of a thin coal bed, and other techniques [30][31][32][33].…”

Overburden Failure Associated with Mining Coal Seams in Close Proximity in Ascending and Descending Sequences Under a Large Water Body

“…Excavation in an ascending sequence can reduce water and sand inrush events, gas outbursts, and rock bursts (Jin et al 2016;Liang et al 2013;Liu et al 2016). Also, when the roof of the upper seam is strong or the coal is difficult to mine, an ascending sequence can be used to reduce or even eliminate the periodic pressure surge of the structure and rock bursts.…”