Study on prediction method of gas emission rate in layered mining of extremely thick coal seam

Abstract It is very difficult to predict the emission of coal gas before the extraction, because it depends on various geological, geographical and operational factors. Gas content is a very important parameter for assessing gas emission in the coal seam during and after the extraction. Large amounts of gas released during the mining cause concern about adequate airflow for the ventilation and worker safety. Hence, the performance of the ventilation system is very important in an underground mine. In this paper, the gas content uncertainty in a coal seam is first investigated using the central data of 64 exploratory boreholes. After identifying the important coal seams in terms of gas emission, the variogram modeling for gas content was performed to define the distribution. Consecutive simulations were run for the random evaluation of gas content. Then, a method was proposed to predict gas emission based on the Monte Carlo random simulation method. In order to improve the reliability and precision of gas emission prediction, various factors affecting the gas emission were investigated and the main factors determining the gas emission were identified based on a sensitivity analysis on the mine data. This method produced relative and average errors of 2% and 0.57%, respectively. The results showed that the proposed model is accurate enough to determine the amount of emitted gas and ventilation. In addition, the predicted value was basically consistent with the actual value and the gas emission prediction method based on the uncertainty theory is reliable.

Download Full-text

Features of Jianshanchong Klippe and its Control to Gas Geology at Qingshan Coal Mine, Jiangxi Province

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.164.501 ◽

2012 ◽

Vol 164 ◽

pp. 501-505

Author(s):

Zhi Gen Zhao ◽

Jia Chen ◽

Jia Ping Yan

Keyword(s):

Coal Seam ◽

Coal Mine ◽

Emission Rate ◽

Coal And Gas Outburst ◽

Jiangxi Province ◽

Coal Seams ◽

Gas Emission ◽

Gas Outburst ◽

Transverse Profile ◽

Tectonic Coal

The coal and gas outburst is serious at Qingshan Coal Mine of Jiangxi Province, so it is of significance to research the features of Jianshanchong klippe and its control to gas geology. The research reveals that: Jianshanchong klippe is distributed from the east boundary of Qingshan Coal Mine to No. 45 Exploration Line, its transverse profile is like a funnel while its longitudinal profile is like a wedge, northwest side of the klippe is thicker and deeper while southeast side is thinner and more shallow. Because of the cover and insert of Jianshanchong klippe, the structure of coal-bearing strata is more complex, some secondary folds are formed, and also, the coal seam is changed greatly, the tectonic coal is well developed and the coal seam is suddenly thickening or thinning. Due to the effect of Jianshanchong klippe, the coal and gas outbursts occur in the area of secondary folds, thicker coal seams or tectonic coals. Concerning the prediction of gas geology in deep area, in view of the facts including simpler structure, stable coal seam and decreased thickness, the gas emission rate and the coal and gas outburst will decrease in Fifth and Sixth Mining Level than that in Second and Third Mining Level

Download Full-text

Gas emission law and control method of working face in extra thick coal seam

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/621/1/012023 ◽

2021 ◽

Vol 621 ◽

pp. 012023

Author(s):

Liangwei Li

Keyword(s):

Coal Seam ◽

Control Method ◽

Gas Emission ◽

Thick Coal Seam ◽

Working Face ◽

And Control

Download Full-text

A Simulative Method on Gas Seepage in Coal Seam around Borehole

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.353-356.3176 ◽

2013 ◽

Vol 353-356 ◽

pp. 3176-3181 ◽

Cited By ~ 2

Author(s):

Guo Qiang Cheng ◽

Yi Wang

Keyword(s):

Numerical Simulation ◽

Coal Seam ◽

Thermal Conduction ◽

Emission Rate ◽

Early Stage ◽

Simulation Method ◽

Actual Situation ◽

Gas Emission ◽

Gas Seepage ◽

Theoretical Results

Based on the analogy between equations of gas seepage in coal seam and that of thermal conduction, a simulative method on gas seepage in coal seam was proposed through that thermal conduction interpreted as gas seepage. The laws of gas emission from borehole in homogeneous and heterogeneous coal seam were analyzed using this method. It indicates that the simulative results of the gas emission from borehole in homogeneous coal seam were satisfied with the corresponding theoretical results during the early stage of gas seepage, while a tolerance between the numerical results and the theoretical ones was appeared in the later period. This is due to the simplification as solving the theoretical equations. The results of heterogeneous coal seam show that curves of gas emission rate conform to the actual situation. The numerical simulation method on the law of gas emission from borehole in coal seam is feasible.

Download Full-text

Cooperative Control Mechanism of Long Flexible Bolts and Blasting Pressure Relief in Hard Roof Roadways of Extra-Thick Coal Seams: A Case Study

Applied Sciences ◽

10.3390/app11094125 ◽

2021 ◽

Vol 11 (9) ◽

pp. 4125

Author(s):

Zhe Xiang ◽

Nong Zhang ◽

Zhengzheng Xie ◽

Feng Guo ◽

Chenghao Zhang

Keyword(s):

Coal Seam ◽

Cooperative Control ◽

Field Tests ◽

Surrounding Rock ◽

Deep Hole ◽

Coal Seams ◽

Thick Coal Seam ◽

Structure Damage ◽

Hard Roof

The higher strength of a hard roof leads to higher coal pressure during coal mining, especially under extra-thick coal seam conditions. This study addresses the hard roof control problem for extra-thick coal seams using the air return roadway 4106 (AR 4106) of the Wenjiapo Coal Mine as a case study. A new surrounding rock control strategy is proposed, which mainly includes 44 m deep-hole pre-splitting blasting for stress releasing and flexible 4-m-long bolt for roof supporting. Based on the new support scheme, field tests were performed. The results show that roadway support failure in traditional scenarios is caused by insufficient bolt length and extensive rotary subsidence of the long cantilever beam of the hard roof. In the new proposed scheme, flexible 4-m-long bolts are shown to effectively restrain the initial expansion deformation of the top coal. The deflection of the rock beam anchored by the roof foundation are improved. Deep-hole pre-splitting blasting effectively reduces the cantilever distance of the “block B” of the voussoir beam structure. The stress environment of the roadway surrounding rock is optimized and anchorage structure damage is inhibited. The results provide insights regarding the safe control of roadway roofs under extra-thick coal seam conditions.

Download Full-text