Risk Assessment and Control Strategy of Residual Coal Pillar in Room Mining: Case Study in Ecologically Fragile Mining Areas, China

Gradual instability of coal pillars left behind underground with room mining is one of the main reasons for sudden roof caving in the gob, surface subsidence, and other significant hazards. Moreover, room mining implies great losses of coal resources. In this paper, the main failure mode and room mining coal pillar process were analyzed according to the coalfield regional engineering geological and hydrogeological conditions. A numerical model was adopted to study the effect of different sizes of coal mining pillars and progressive instability failure of coal pillar on the plastic zone’s evolution characteristics and stress field of coal pillars in the stope. The proposed technologies of cemented paste backfilling and reinforcement of residual coal pillars are applied, and a numerical simulation model is established to study the strata movement characteristics and analyze the stability degree of residual coal pillar and key aquiclude strata in the Pliocene series of Neogene. Consequently, the performance and application prospect were evaluated. The results obtained substantiate a new method for the long-term stability control of coal pillars in room mining and protecting the ecological environment in China’s western eco-environmental frangible area.

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The Stability Control Technology of Crosscut while Mining without Coal Pillar in Steep Seam

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.90-93.2073 ◽

2011 ◽

Vol 90-93 ◽

pp. 2073-2079

Author(s):

Yu Feng Wang ◽

Zhi Qiang Liu ◽

Bin Song Jiang

Keyword(s):

Support System ◽

Coal Pillar ◽

Stability Control ◽

Surrounding Rock ◽

Steep Seam ◽

Floor Rock ◽

Long Term Stability ◽

Rock Collapse ◽

The Stability

In order to improve the mining benefit of coal resources, Chang Gouyu Coal Mine carried out the technology of mining without coal pillar in steep seam. The key of the technology was to ensure a long-term stability of the cross-entry roadway across the seam. Through the analysis of the nature of steep seam roof and floor rock, and based on the stability analysis and loose circle measured of surrounding rock of crosscut roadway, we brought forward adopting shotcrete rockbolt mesh and U-shaped steel complex support structure system. This complex support system could flex lengthways and compress in radial direction. The entirety integrated with the surrounding rock, and they formed into a whole. Application of the complex support system could effectively control the deformation of the surrounding rock collapse, and maintain the stability of the crosscut.

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Study on the Rheological Failure Mechanism of Weakly Cemented Soft Rock Roadway during the Mining of Close-Distance Coal Seams: A Case Study

Advances in Civil Engineering ◽

10.1155/2020/8885849 ◽

2020 ◽

Vol 2020 ◽

pp. 1-20

Author(s):

Wenkai Ru ◽

Shanchao Hu ◽

Jianguo Ning ◽

Jun Wang ◽

Qingheng Gu ◽

...

Keyword(s):

Coal Seam ◽

Failure Mechanism ◽

Coal Pillar ◽

Soft Rock ◽

Western China ◽

Creep Failure ◽

Mining Areas ◽

Geological Conditions ◽

Residual Coal ◽

Close Distance

During the mining of the shallow-buried and close-distance multiple coal seam, the rheological failure of the surrounding weakly cemented soft rock of the roadway in the lower coal seam under the concentrated stress is very rare. However, the stress on the roof of the upper coal seam is transmitted down through the residual pillar, resulting in this situation. Taking the Gaojialiang coal mine which is located in the mining areas of western China as the research object, the failure mechanism of the roadway roof under the residual coal pillar in the shallow-buried and close-distance multiple seam is studied in combination with field monitoring and numerical simulation. Furthermore, suggestions on the roadway support under such geological conditions are proposed. The results show that the residual coal pillar in the working face of the lower coal seam gradually collapses during the mining of the shallow-buried and close-distance multiple coal seam. The concentrated stress transferred by the coal pillar increases further, which makes the roof stress of the lower coal seam roadway to increase continuously. In addition, the stress of the roadway roof also increases further due to the rotation of the broken rock above the goaf, and the peek region of stress moves to the nongoaf area. Combining the heavy concentrated stress and weakly cemented property, the shallow-buried surrounding rock shows rheological behavior and failure. Therefore, we must pay more attention on the creep failure of the roadway roof under the action of the residual coal pillar even in the shallow-buried coal seam.

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Stability and control of room mining coal pillars—taking room mining coal pillars of solid backfill recovery as an example

Journal of Central South University ◽

10.1007/s11771-017-3515-8 ◽

2017 ◽

Vol 24 (5) ◽

pp. 1121-1132 ◽

Cited By ~ 19

Author(s):

Ji-xiong Zhang ◽

Peng Huang ◽

Qiang Zhang ◽

Meng Li ◽

Zhi-wei Chen

Keyword(s):

Stability And Control ◽

Coal Pillars ◽

Mining Coal ◽

And Control

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Modeling the Spatial and Temporal Evolution of Stress during Multiworking Face Mining in Close Distance Coal Seams

Advances in Civil Engineering ◽

10.1155/2021/5624972 ◽

2021 ◽

Vol 2021 ◽

pp. 1-11

Author(s):

Yong Zhang ◽

Jinkun Yang ◽

Jiaxuan Zhang ◽

Xiaoming Sun ◽

Chen Chen ◽

...

Keyword(s):

Numerical Simulation ◽

Stress Distribution ◽

Temporal Evolution ◽

Coal Pillar ◽

Coal Seams ◽

Geological Conditions ◽

Coal Pillars ◽

The Stability ◽

Close Distance ◽

Close Distance Coal Seams

Mining in close distance coal seams (CDCSs) is frequently associated with engineering disasters because of the complicated nature of stress distribution within CDCSs. In order to establish a layout of a roadway to minimize the occurrence of disasters associated with mining CDCS, here the spatial and temporal evolution of stress distribution during the multiworking face mining of a CDCS was explored through numerical simulation based on the engineering and geological conditions of the Nantun Coal Mine. The numerical simulation results indicate that, after the extraction of adjacent multiple working faces, the spatial distribution of stress can be characterized with areas of increased, reduced, and intact stress. The superposed stress of inclined seams that are very close to each other propagates through coal pillars in the bottom floor, and this propagation follows neither the line along the axis of the coal pillar nor the line perpendicular to the direction of the floor. It instead propagates along a line angled with the axis of the coal pillar. The roadway can be arranged in the area with reduced stress, to improve its the stability. Based on the computed spatial and temporal evolution of stress, an optimized layout of roadway was proposed. This layout features a reasonable interval between the mining roadway and a minimal proportion of increased stress areas along the mining roadway and is aligned with geological structures.

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Numerical Investigation into Evolution of Crack and Stress in Residual Coal Pillars under the Influence of Longwall Mining of the Adjacent Underlying Coal Seam

Shock and Vibration ◽

10.1155/2019/2094378 ◽

2019 ◽

Vol 2019 ◽

pp. 1-18

Author(s):

Xin Wang ◽

Yuechao Wu ◽

Xuehua Li ◽

Shun Liang

Keyword(s):

Coal Seam ◽

Longwall Mining ◽

Distinct Element ◽

Movement Characteristics ◽

Universal Distinct Element Code ◽

Voronoi Method ◽

Mining Safety ◽

Distinct Element Code ◽

Coal Pillars ◽

Residual Coal

Longwall mining of the adjacent coal seam with the presence of residual coal pillars overlying the seam can result in abnormal strata pressure and severe overburden failure, which poses a significant threat to mining safety. The threat is mainly manifested in the form of intense coal or rock burst and hazardous interconnection between gobs. This study employed the universal distinct element code (UDEC) to investigate the microscopic failure mechanism of the overlying residual coal pillars under the influence of longwall mining of an adjacent underlying coal seam in Yuanbaowan coal mine, China. Using the Voronoi method, we innovatively visualized the evolution of cracks in residual pillars, revealed the mechanism behind the failure of pillars, and explored the evolution and distribution of abutment stress. Also, strata movement characteristics during underlying panel extraction have been surveyed. Based on the modeling results, effective measures are proposed to ensure safe mining under residual coal pillars. This study might provide a certain reference for safe extraction of multiple seams in Datong Coalfield, China, and also in the central and western Appalachian Basin, United States, where many mining activities are carried out under residual pillars.

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The Sustainable Development of Aged Coal Mine Achieved by Recovering Pillar-Blocked Coal Resources

Energies ◽

10.3390/en13153912 ◽

2020 ◽

Vol 13 (15) ◽

pp. 3912

Author(s):

Huadong Gao ◽

Baifu An ◽

Zhen Han ◽

Yachao Guo ◽

Zeyu Ruan ◽

...

Keyword(s):

Coal Mine ◽

Coal Pillar ◽

Economic Benefits ◽

Industrial Facilities ◽

The Sustainable Development ◽

Coal Resources ◽

Coal Pillars ◽

Social Environmental ◽

Residual Coal ◽

China’S Economy

China faces the problem of depletion of its coal resources, and a large number of mines are becoming aged mines. Demand for coal, however, still increases due to the growth of China’s economy. Energy shortage might restrict the sustainability of China’s national economy. As one contribution to a solution, this paper proposes the innovative exploitation method of solid backfill coal mining (SBCM) technology to exploit parts of pillar-blocked (residual coal pillar resources under industrial square, RCPRIS) that protect industrial facilities. Thus, blocked coal resources may be converted into mineable reserves that improve the recovery ratio of mine resources. Also, waste would be removed from the surface reducing hazards of environmental pollution. Based on the case of the Baishan Coal Mine in Anhui, China, numerical simulation is used to study the size of shaft-protecting coal pillars (SPCP) required at different backfill ratios. Results show that the disturbance to a shaft caused by exploitation decreases with the increase of the backfill ratio. When using SBCM to exploit RCPRIS under the condition of 80% backfill ratio, compared with the caving method, a lot of pillar-blocked coal resources would be freed. The life of Baishan Coal Mine would be prolonged, resulting in appreciable social, environmental, and economic benefits.

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Study on Stress Relief of Hard Roof Based on Presplitting and Deep Hole Blasting

Advances in Civil Engineering ◽

10.1155/2020/8842818 ◽

2020 ◽

Vol 2020 ◽

pp. 1-12

Author(s):

Peng Gong ◽

Yongheng Chen ◽

Zhanguo Ma ◽

Shixing Cheng

Keyword(s):

Stress Distribution ◽

Coal Mine ◽

Coal Pillar ◽

Deep Hole ◽

Hard Roof ◽

Formation Conditions ◽

Coal Pillars ◽

Mining Coal ◽

The Impact ◽

Pillar Size

For the problem that the hard roof causes wider end-mining coal pillar, and the roadway is greatly affected by mining, this paper took Shanxi Luning Coal Mine as the engineering background; based on the stress distribution characteristics of the coal pillar, the calculation method of the limit end-mining coal pillar size was given; considering the formation conditions and transmission forms of the advanced abutment stress, a method combining presplitting and deep hole blasting was proposed to weaken the advanced abutment stress. The numerical simulation was used to analyze the stress distribution of coal pillars, which was verified by on-site industrial tests. The results showed that the presplitting can achieve the blocking of stress. The closer it is to the peak of the abutment stress, the better the blocking effect. Deep hole blasting can weaken the source of the advanced abutment stress and reduce the peak of abutment stress. With the combination of the two blasting methods, the end-mining coal pillar size of Luning Coal Mine can be reduced to 60 m. The method combining presplitting and deep hole blasting can effectively reduce the end-mining coal pillar size and reduce the impact of mining on the deformation of the dip roadway.

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Microseismic Precursory Characteristics of Rock Burst Hazard in Mining Areas Near a Large Residual Coal Pillar: A Case Study from Xuzhuang Coal Mine, Xuzhou, China

Rock Mechanics and Rock Engineering ◽

10.1007/s00603-016-1036-7 ◽

2016 ◽

Vol 49 (11) ◽

pp. 4407-4422 ◽

Cited By ~ 40

Author(s):

An-ye Cao ◽

Lin-ming Dou ◽

Chang-bin Wang ◽

Xiao-xiao Yao ◽

Jing-yuan Dong ◽

...

Keyword(s):

Rock Burst ◽

Coal Mine ◽

Coal Pillar ◽

Mining Areas ◽

Burst Hazard ◽

Residual Coal

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Duffing Chaotic System Stability Control Based on Sliding Mode Control

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.605-607.1639 ◽

2012 ◽

Vol 605-607 ◽

pp. 1639-1642

Author(s):

Ding Ma

Keyword(s):

Chaotic System ◽

Control Method ◽

Sliding Mode ◽

Variable Structure ◽

Stability Control ◽

System Stability ◽

Terminal Sliding Mode ◽

Sliding Mode Variable Structure ◽

The Stability ◽

And Control

Considering the Duffing chaotic system, the problem of stability control based on the terminal sliding mode variable structure is studied. A new terminal sliding mode surface and control law are designed. On this basis, the stability of closed-loop system is analyzed. Simulation results show the effectiveness of the control method.

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Mechanism of Coal Burst and Prevention Practice in Deep Asymmetric Isolated Coal Pillar: A Case Study from YaoQiao Coal Mine

Shock and Vibration ◽

10.1155/2021/3751146 ◽

2021 ◽

Vol 2021 ◽

pp. 1-19

Author(s):

Chengchun Xue ◽

Anye Cao ◽

Wenhao Guo ◽

Songwei Wang ◽

Yaoqi Liu ◽

...

Keyword(s):

Numerical Simulation ◽

Coal Mine ◽

Prevention And Control ◽

High Stress ◽

Coal Pillar ◽

Support Pressure ◽

Mining District ◽

Coal Pillars ◽

And Control ◽

The Impact

Coal pillar bursts continue to be a severe dynamic hazard. Understanding its mechanism is of paramount importance and crucial in preventing and controlling its occurrence. The extreme roadway deformations from the asymmetric isolated coal pillars in the central mining district of YaoQiao Coal Mine have responded with frequent intense tremors, with risky isolated coal pillar bursts. The theoretical analysis, numerical simulation, and field measurements were done to research the impact of spatial overburden structure and stress distribution characteristics on the isolated coal pillar area, aiming to reveal the mechanism of coal pillar burst leading to the practice of prevention and control in the asymmetric isolated coal pillar area. The study shows that the overburden structure of the asymmetric is an asymmetric “T” structure in the strike-profile, and the stress in the coal pillar is mostly asymmetric “saddle-shaped” distribution, with the peak stress in the east side of the coal pillar, and the coal pillar is a “high stress serrated isolated coal pillar.” Numerical simulation results showed that the support pressure in the isolated coal pillar area on the strike profile was asymmetrically “saddle-shaped” distribution. The peak vertical stress in the coal pillar area continued to rise and gradually shifted to the mining district's deep part. As a result, the response of the roadway sides to the dynamic load disturbance was more pronounced. They developed a coal burst prevention and control program of deep-hole blasting in the roof of asymmetrical isolated coal pillar roof and unloading pressure from coal seam borehole. Monitored data confirmed that the stress concentration was influential in the roadway’s surrounding rock in the asymmetric isolated coal pillar area, circumventing coal pillar burst accidents. The research outcomes reference the prevention and control of coal bursts at isolated working faces of coal pillars under similar conditions.

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