Numerical simulation on stress evolution and deformation of overlying coal seam in lower protective layer mining

In the process of coal mining, the surface subsidence under ultrathick loose layer is abnormal (subsidence coefficient greater than 1.0), which will cause great damage to the surface ecological environment. The fracture propagation and stress evolution of bedrock are of great significance to the prevention of surface subsidence. Taking the 1305 working face of a mine as the background, this paper study the process of crack propagation and stress evolution of bedrock under the influence of ultrathick loose layer by methods of on-site measurement, similar simulation, and numerical simulation. During the research process, the physical model was verified by the measured data. Then, the numerical model was verified by the crack propagation angle and subsidence of bedrock, which were obtained in a similar simulation. Based on the verified numerical model, it was obtained that after the coal seam was mined out, the bedrock above the mined-out area was mainly damaged by tension, while the strata on both sides of the crack expansion angle were mainly damaged by shear and tension. During coal seam mining, for bedrock the process of fracture expansion, subsidence, and stress evolution all could be divided into four stages. This research provides a basis for the control of surface subsidence.

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Numerical and Similarity Simulation Study on the Protection Effect of Composite Protective Layer Mining with Gently Inclined Thick Coal Seam

Shock and Vibration ◽

10.1155/2021/6679199 ◽

2021 ◽

Vol 2021 ◽

pp. 1-15

Author(s):

Jianhong Ma ◽

Chao Hou ◽

Jiangtao Hou

Keyword(s):

Numerical Simulation ◽

Coal Seam ◽

Simulation Analysis ◽

Protective Layer ◽

Vertical Displacement ◽

Vertical Stress ◽

Distribution Law ◽

Gas Drainage ◽

Thick Coal Seam ◽

Maximum Expansion

Protective layer mining, as a dominating method for preventing coal and gas outburst, is generally adopted in highly gassy coal mines. In the absence of a suitable thickness coal seam to serve as the protective layer, the rock-coal composite protective layer was proposed in this paper. We conducted a series of simulations and engineering measurements to investigate the protective effect under the mining of the rock-coal composite protective layer of the Zhongtai coal mine located in the Hebi area of Henan, China. The numerical simulation analysis showed that, after the completion of protective layer mining, the minimum vertical stress of the No. 2-1 coal seam had been reduced to 3.46 MPa. The maximum vertical displacement of the No. 2-1 coal seam is 455.01 mm. The maximum expansion deformation of the No. 2-1 coal seam is 9.77‰; the effective pressure relief range is as long as 160 m. The similarity simulation experiment revealed that, after the completion of protective layer mining, the minimum vertical stress of the No. 2-1 coal seam is 4.0 MPa. The maximum vertical displacement of the No. 2-1 coal seam is 640 mm. The maximum expansion deformation of the No. 2-1 coal seam is 26.37‰; the effective protection range reaches 130 m. The engineering measurements demonstrated that the variation law of gas drainage parameters in the protected layer corresponds to the protected layer's vertical stress distribution law in numerical simulation and similarity simulation. With the exploitation of the composite protective layer, the protective layer’s pressure begins to release. The average gas drainage concentration is 2-3 times of that before the composite protective layer mining.

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Numerical Simulation of Pressure Relief for Extremely Thin Coal Seam as Protection Seam Based on UDEC

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.295-298.2879 ◽

2013 ◽

Vol 295-298 ◽

pp. 2879-2883

Author(s):

Li Ming Zhang

Keyword(s):

Numerical Simulation ◽

Coal Seam ◽

Protective Layer ◽

Base Plate ◽

Roof Displacement ◽

Pressure Relief ◽

Thin Coal Seam ◽

The Face ◽

High Concentrations ◽

Overlying Strata

Overlying strata stress distribution, pressure relief region and crack distribution characteristics are analyzed based on numerical simulation of pressure relief with extremely thin coal seam as protection seam used by UDEC. The result is a true reflection of overlying strata movement and fissures for extremely thin coal seam as protection seam. Studies have shown that the roof displacement in the face of protective layer promoting is big, and as far away from the protective layer, the roof displacement is gradually reduced, the base plate displacement is almost the same, but the roof and floor to stress have been fully release; after protective layer mining, an "O" type pressure relief crack area is formed above the goaf, which is gas rich region and gas channels at the same time and suitable for extracting high concentrations gas.

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Permeability Enhancement and Gas Drainage Effect in Deep High Gassy Coal Seams via Long-Distance Pressure Relief Mining: A Case Study

Advances in Civil Engineering ◽

10.1155/2021/6637052 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Xiang He ◽

Ke Yang ◽

Penghua Han ◽

Wenjie Liu ◽

Zhonghao Zhang ◽

...

Keyword(s):

Numerical Simulation ◽

Coal Seam ◽

Protective Layer ◽

Enhancement Effect ◽

Yield Model ◽

Long Distance ◽

Pressure Relief ◽

Gas Drainage ◽

Permeability Enhancement ◽

Seam Mining

Coal 3 in group A is employed as a protective layer to release long-distance coal 4 in group B in Paner colliery (approximately 80 m vertical interval) as the mining depth extends downward, which is the first engineering test in the Huainan coal mining area. To evaluate the validity of the scheme, the permeability distribution, and evolution law, gas pressure distribution characteristics, swelling deformation, pressure relief range, and gas drainage volume of the protected coal seam are analyzed using a FLAC3D numerical simulation and field measurements. Therefore, different stress-permeability models are adopted for caved, fractured, and continuous deformation zones, and a double-yield model is applied in the goaf based on compaction theory to improve the accuracy of the numerical simulation. The results indicate that the extraction of coal 3 has a positive effect on permeability enhancement and pressure relief gas drainage. However, the dip angle of coal measurements causes asymmetric strata movement, which leads to the pressure relief and permeability enhancement area shifting to the downhill side, where the permeability enhancement effect of the downhill side is better than that of the uphill side. The permeability enhancement zone is an inverted trapezoid, but the effective pressure relief range is a positive trapezoid. The permeability of the protected coal seam in the pressure relief zone is significantly higher than that in the compressive failure zone. The permeability in the pressure relief zone will decrease again due to the recompaction of the coal seam with an advancement of the longwall face. Thus, pressure relief gas drainage is suggested during long-distance protective coal seam mining to eliminate gas hazards.

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Reasonable Entry Layout of Lower Seam in Multi-Seam Mining Based on Numerical Simulation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.295-298.2980 ◽

2013 ◽

Vol 295-298 ◽

pp. 2980-2984

Author(s):

Xiang Qian Wang ◽

Da Fa Yin ◽

Zhao Ning Gao ◽

Qi Feng Zhao

Keyword(s):

Numerical Simulation ◽

Stress Distribution ◽

Coal Seam ◽

Coal Mine ◽

Abutment Pressure ◽

Surrounding Rock ◽

Geological Conditions ◽

Seam Mining

Based on the geological conditions of 6# coal seam and 8# coal seam in Xieqiao Coal Mine, to determine reasonable entry layout of lower seam in multi-seam mining, alternate internal entry layout, alternate exterior entry layout and overlapping entry layout were put forward and simulated by FLAC3D. Then stress distribution and displacement characteristics of surrounding rock were analyzed in the three ways of entry layout, leading to the conclusion that alternate internal entry layout is a better choice for multi-seam mining, for which makes the entry located in stress reduce zone and reduces the influence of abutment pressure of upper coal seam mining to a certain extent,. And the mining practice of Xieqiao Coal Mine tested the results, which will offer a beneficial reference for entry layout with similar geological conditions in multi-seam mining.

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