scholarly journals Numerical Study on the Mechanism of Water Inrush by Floor Damage and Fault Activation during Longwall Mining

2018 ◽  
Author(s):  
Peisen Zhang ◽  
Wei Yan ◽  
Wenquan Zhang ◽  
Hao Wang
Keyword(s):  
Longwall Mining ◽  
Numerical Study ◽  
Water Inrush ◽  
Fault Activation

scholarly journals Analysis of insidious fault activation and water inrush from the mining floor

2014 ◽  
Vol 24 (4) ◽  
pp. 477-483 ◽  
Author(s):  
Xinyu Hu ◽  
Lianguo Wang ◽  
Yinlong Lu ◽  
Mei Yu
Keyword(s):  
Water Inrush ◽  
Fault Activation

scholarly journals Experimental and Numerical Study of Rock Stratum Movement Characteristics in Longwall Mining

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Wan-rong Liu
Keyword(s):  
Stress Concentration ◽  
Coal Seam ◽  
Longwall Mining ◽  
Roof Rock ◽  
Numerical Study ◽  
High Stress ◽  
Engineering Practice ◽  
Rock Stratum ◽  
Working Face ◽  
Coal Wall

The roof fracture is the main cause of coal mine roof accidents. To analyze the law of movement and caving of the roof rock stratum, the roof subsidence displacement, rock stratum stress, and the rock stratum movement law were analyzed by using the methods of the particle discrete element and similar material simulation test. The results show that (1) as the working face advances, regular movement and subsidence appears in the roof rock strata, and the roof subsidence curve forms a typical “U” shape. As the coal seam continues to advance, the maximum subsidence displacement remains basically constant, and the subsidence displacement curves present an asymmetric flat-bottomed distribution. (2) After the coal seam is mined, the overburden forms an arched shape force chain, and the arched strong chain is the path of the overburden transmission force. The farther away from the coal seam, the smaller the stress concentration coefficient is, but it is still in a high stress area, and the stress concentration position moves toward the middle area of the goaf. The stress concentration in front of the coal wall is the source of force that forms the abutment pressure. (3) Above the coal wall towards the goaf, a stepped fracture was formed in the roof rock stratum. The periodic fracture of the rock stratum is the main cause of the periodic weighting of the working face. Understanding the laws of rock movement and stress distribution is of great significance for guiding engineering practice and preventing the roof accidents.

scholarly journals Floor Failure Evolution Mechanism for a Fully Mechanized Longwall Mining Face above a Confined Aquifer

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Jinghui Zhai ◽  
Danlong Liu ◽  
Gang Li ◽  
Fangtian Wang
Keyword(s):  
Longwall Mining ◽  
Water Inrush ◽  
Friction Angle ◽  
Peak Position ◽  
Depth Range ◽  
Confined Aquifer ◽  
Factors Affecting ◽  
Floor Failure ◽  
Failure Evolution ◽  
Pressure Stress

In longwall mining, the risk of water inrushes from the floors of deeply buried coal seams is closely related to the degree and depth of the destruction for the mining floor. To analyze the main factors affecting floor failure and the evolution of such failures, this study considered the LW2703 working face of the Chengjiao Coal Mine in China, which is characterized by a large buried depth, complex fault structure, and high pressure from a confined aquifer. The characteristics affecting floor crack development depth were analyzed by considering friction angle, cohesion force, floor pressure, stress increase coefficient, and peak position. A FLAC3D simulation was performed to compare the degrees of floor damage that occurred for caving and backfilling methods during the mining process. High-density electrical detection was performed on-site and used to (1) determine the maximum depth range of the floor damage, (2) reveal the laws governing the evolution of damage in a mining floor, and (3) provide a reasonable basis for evaluating and preventing floor water inrush accidents.

scholarly journals The Effects of Backfill Mining on Strata Movement Rule and Water Inrush: A Case Study

Processes ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 66 ◽  
Author(s):  
Jian Hao ◽  
Yongkui Shi ◽  
Jiahui Lin ◽  
Xin Wang ◽  
Hongchun Xia
Keyword(s):  
Longwall Mining ◽  
Water Inrush ◽  
Vertical Stress ◽  
Strata Movement ◽  
Ground Pressure ◽  
In Situ Investigation ◽  
Floor Failure ◽  
Backfill Mining ◽  
Failure Depth

Backfill mining is widely used to control strata movement and improve the stress environment in China’s coal mines. In the present study, the effects of backfill mining on strata movement and water inrush were studied based on a case study conducted in Caozhuang Coal Mine. The in-situ investigation measured abutment pressure distribution (APD), roof floor displacement (RFD), and vertical stress in the backfill area. Results are as follows: (i) The range and peak of APD, RFD, and vertical stress in the backfill area are smaller than in traditional longwall mining with the caving method. (ii) Backfill mining could change the movement form and amplitude of overburden and improve the ground pressure environment. (iii) Floor failure depth (FFD) is much smaller in backfill mining. Backfill mining can be an effective method for floor water inrush prevention.

scholarly journals Numerical study of the influence of coal seam mining under reservoir on deep oversize fault deformation

2019 ◽  
Vol 23 (4) ◽  
pp. 2315-2322
Author(s):  
Xinxian Zhai ◽  
Yanwei Zhai ◽  
Xingzi Tu ◽  
Rubo Li ◽  
Guangshuai Huang
Keyword(s):  
Coal Seam ◽  
Numerical Study ◽  
Hanging Wall ◽  
Water Inrush ◽  
Coal Pillar ◽  
Simulation Software ◽  
Face Advance ◽  
Pillar Width ◽  
Coal Face ◽  
Seam Mining

Ground surface in Yonglong coal mine is hilly terrain. There is a Yinshigou reservoir on minefield. Deep coal seam mining under the reservoir has an influence on the deformation of oversize normal fault, and can cause severe mine water-inrush. Using numerical simulation software UDEC, the paper studied the characteristics of plastic zone and stress field in front of coal face in the hanging wall of the fault, while the coal face advance distances from setting-up room to coal face line were different. The results showed that while the distance from coal face to the fault i. e. the width of fault-protected pillar, was 80 m, the front abutment pressure had less influence on two sides rock mass of the fault, the fault reduced the vertical stress of its surrounding rocks; The surrounding rocks in the vicinity of fault were in a same vertical displacement contour, whose displacement was very smaller. Reasonable fault-protected pillar width of the numerical study was much closer to the average water-proof coal pillar width based on coal mines water prevention regulations of China. Consequently, while the width of fault-protected pillar is more than 80 m, coal seam mining in hanging wall of fault has no influence on the fault, and coal seam safely mining under the reservoir could be carried out.

scholarly journals A Numerical Study of Stress Distribution and Fracture Development above a Protective Coal Seam in Longwall Mining

Processes ◽  
2018 ◽  
Vol 6 (9) ◽  
pp. 146 ◽  
Author(s):  
Chunlei Zhang ◽  
Lei Yu ◽  
Ruimin Feng ◽  
Yong Zhang ◽  
Guojun Zhang
Keyword(s):  
Stress Distribution ◽  
Coal Seam ◽  
Gas Flow ◽  
Longwall Mining ◽  
Numerical Study ◽  
Stress Relief ◽  
Coal Industry ◽  
Gas Drainage ◽  
New Findings ◽  
Fracture Development

Coal and gas outbursts are serious safety concerns in the Chinese coal industry. Mining of the upper or lower protective coal seams has been widely used to minimize this problem. This paper presents new findings from longwall mining-induced fractures, stress distribution changes in roof strata, strata movement and gas flow dynamics after the lower protective coal seam is extracted in a deep underground coal mine in Jincheng, China. Two Flac3D models with varying gob loading characteristics as a function of face advance were analyzed to assess the effect of gob behavior on stress relief in the protected coal seam. The gob behavior in the models is incorporated by applying variable force to the floor and roof behind the longwall face to simulate gob loading characteristics in the field. The influence of mining height on the stress-relief in protected coal seam is also incorporated. The stress relief coefficient and relief angle were introduced as two essential parameters to evaluate the stress relief effect in different regions of protected coal seam. The results showed that the rock mass above the protective coal seam can be divided into five zones in the horizontal direction, i.e. pre-mining zone, compression zone, expansion zone, recovery zone and re-compacted zone. The volume expansion or the dilation zone with high gas concentration is the best location to drill boreholes for gas drainage in both the protected coal seam and the protective coal seam. The research results are helpful to understand the gas flow mechanism around the coal seam and guide industry people to optimize borehole layouts in order to eliminate the coal and gas outburst hazard. The gas drainage programs are provided in the final section.

scholarly journals Strata Movement and Fracture Propagation Characteristics due to Sequential Extraction of Multiseam Longwall Panels

2018 ◽  
Vol 2018 ◽  
pp. 1-17 ◽  
Author(s):  
Xiangyang Zhang ◽  
Behrooz Ghabraie ◽  
Gang Ren ◽  
Min Tu
Keyword(s):  
Longwall Mining ◽  
Water Inrush ◽  
Ground Surface ◽  
Fracture Propagation ◽  
Physical Modelling ◽  
Propagation Characteristics ◽  
Gas Drainage ◽  
Strata Deformation ◽  
Seam Mining ◽  
Vertical Subsidence

Multiseam longwall mining-induced strata deformation and fracture propagation patterns are different from those of single-seam mining. This difference is due to interaction of the caved zones as a result of longwall mining activity at different coal seams, which severely impacts formation of subsidence and permeability of the strata after multiseam mining. Understanding this phenomenon is of great importance in order to predict the multiseam subsidence reliably, evaluate the risk of water inrush and take suitable preventive measures, and determine suitable locations for placing gas drainage boreholes. In this study, scaled physical modelling techniques are utilised to investigate strata deformation, fracture propagation characteristics, and vertical subsidence above multiseam longwall panels. The results show that magnitude of the incremental multiseam subsidence increases significantly after multiseam extraction in comparison with single-seam mining. This increase occurs to different extent depending on the multiseam mining configuration. In addition, interstrata fractures above the abutment areas of the overlapping panels propagate further towards the ground surface in multiseam extractions compared with single-seam extractions. These fractures increase the risk of water inrush in presence of underground/surface water and create highly permeable areas suitable for placing gas drainage boreholes.

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