Experimental Study of Deformations and Failures of the Coal Wall in a Longwall Working Face

Rib spalling disaster at the coal mining faces severely restricted the safe and efficient output of coal resources. In order to solve this problem, based on the analysis of the current status of rib spalling in the three-soft coal seam 1508 Working Face of Heyang Coal Mine, a mechanical model of sliding-type rib spalling was established and the main influencing factors that affect rib spalling are given. The mechanism of grouting technology to prevent and control rib spalling has been theoretically analyzed. A similarity simulation experiment is used to analyze the change law of roof stress under the condition of three-soft coal seam mining. The optimal grouting pressure is determined by a numerical simulation experiment. And, silicate-modified polymer grouting reinforcement materials (SMPGMs) are used in field experiments. After twice grouting operations in the 1508 Working Face, the coal wall was changed from the original soft and extremely easy rib spalling to a straight coal wall and the amount of rib spalling has been reduced by 57.45% and 48.43, respectively. And, the mining height has increased by 0.16 m and 0.23 m, respectively. The experimental results show that the rib spalling disaster of the three-soft coal seam has been effectively controlled.

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Gas Distribution Law for the Fully Mechanized Top-Coal Caving Face in a Gassy Extra-Thick Coal Seam

Advances in Civil Engineering ◽

10.1155/2018/3563728 ◽

2018 ◽

Vol 2018 ◽

pp. 1-8

Author(s):

Wenlin Wang ◽

Fangtian Wang ◽

Bin Zhao ◽

Gang Li

Keyword(s):

Longwall Mining ◽

Volume Fraction ◽

Vertical Direction ◽

Thick Coal Seam ◽

Working Face ◽

Coal Wall ◽

The Face ◽

Fraction Distribution ◽

Gas Volume Fraction ◽

Gas Volume

Mine gas overflow is a serious threat to the safe and efficient longwall mining of gassy coal seams. Based on the field mining conditions and gas extraction of the fully mechanized top-coal caving face of a gassy coal mine, the space volume fraction distribution and emission (extraction rate) of gas in the face were tested by an arrangement of measuring points in the stereo grid. The isograms of gas volume fraction distribution for each measurement section and air direction in the face are drawn. The research shows that each measurement section gas volume fraction distribution is presented for an asymmetric concave curve along the vertical direction of the coal wall in the air-inlet side and the air-return side of the face; on the working face air-return side, the determination of gas volume fraction distribution of the section appears as falling straight line along the vertical direction of the coal wall. Before the first weighting, the absolute quantity of gas emission in the working face increased with the advancing of the working face, reached the maximum at the time of the first weighting, and then remained stable.

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Comprehensive Measurement of the Deformation and Failure of Floor Rocks: A Case Study of the Xinglongzhuang Coal Mine

Geofluids ◽

10.1155/2020/8830217 ◽

2020 ◽

Vol 2020 ◽

pp. 1-14

Author(s):

Hao Liu ◽

Pu Wang ◽

Weihe Zhang ◽

Qiang Liu ◽

Lijun Su

Keyword(s):

Coal Mine ◽

Abutment Pressure ◽

Three Dimensional ◽

Strain Sensing ◽

Floor Rock ◽

Deformation And Failure ◽

Working Face ◽

Floor Failure ◽

Coal Wall ◽

Different Depths

The isolated island panel 10304 of the Xinglongzhuang coal mine was used as the research subject to study the deformation and damage characteristics of the coal seam floor. The damage of the floor was studied using the borehole strain sensing method and borehole imaging technology, and FLAC3D was used to study the influence of abutment pressure on floor failure. The result shows that the floor under the superimposed area which is affected by lateral and advanced abutment pressure is damaged firstly, and the maximum depth reaches 26 m, other areas of the working face about 23 m. The degree of deformation and failure of floor rock at different depths is decreased. The deformation damage increases with the advancement of the working face until a certain distance at the same depth. The hole image can clearly show the influence range of the abutment pressure in front of the coal wall and influence the degree of the advancement and lag by means of the strain increment curve for each sensor probe and the images from different drilled positions. On the basis that the results of simulation and field measurement are consistent, the results can reflect the three-dimensional failure characteristics of the whole island working face floor in the process of coal mining more comprehensively and accurately; moreover, they also can provide important information for mine flood prevention and ecological environment protection.

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Experimental Study on the Efficacy of Water Infusion for Underground Mining of a Coal Seam

Applied Sciences ◽

10.3390/app9183820 ◽

2019 ◽

Vol 9 (18) ◽

pp. 3820 ◽

Cited By ~ 1

Author(s):

Nguyen ◽

Do

Keyword(s):

Experimental Study ◽

Moisture Content ◽

Coal Seam ◽

Field Test ◽

Underground Mining ◽

Water Injection ◽

Strength Properties ◽

Water Infusion ◽

Coal Wall ◽

Infusion Method

The main purpose of this study is to evaluate the efficacy of the water infusion method for various coalfaces of a coal seam by an experimental study. First, laboratory tests were performed on several coal samples taken from actual coalfaces to determine the general characteristics, especially the strength properties, with respect to the moisture content and time. The results obtained from the laboratory were employed to evaluate the appropriate parameters (e.g., water injection time and the optimum moisture content) for water infusion works in the field. A field test was then performed in order to assess the efficacy of water infusion for underground mining. The spalling depth (i.e., longwall face failure of coal wall, involving the stability of underground mining coalfaces) and mining velocity (i.e., involving the cost-effectiveness of mining constructions) were monitored at various coalfaces for both case studies (i.e., with and without water infusion). Expectedly, the field test results revealed that the spalling depth decreased significantly, whereas the mining velocity sped up considerably, at coalfaces using water infusion compared to at those without using the water infusion method. In conclusion, the promising findings obtained from the field test reinforced the efficacy of water infusion for underground mining coalfaces.

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

Shock and Vibration ◽

10.1155/2019/5041536 ◽

2019 ◽

Vol 2019 ◽

pp. 1-15 ◽

Cited By ~ 6

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.

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Optimization Study of Advance Support in the Roadway of Paste Filling Working Face

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.255-260.3702 ◽

2011 ◽

Vol 255-260 ◽

pp. 3702-3707

Author(s):

Shao Jie Chen ◽

Wei Jia Guo ◽

Hai Long Wang ◽

Bo Li

Keyword(s):

Working Face ◽

Optimization Study ◽

Coal Wall ◽

The Face ◽

Strata Behavior ◽

Behavior Characteristics ◽

Working Efficiency ◽

Practical Measure ◽

Main Influence ◽

Overlying Strata

On the basis of the field measurement, the characteristics of advance strata behavior are analyzed in the past filling working face and the advance support method is optimized in the roadway. The practical measure researches show that, because the paste filling supports the overlying strata of the goaf availably, the strata behaviors of 2351 paste filling working face in Daizhuang coalmine are not obvious; And the protective pillar bears a little load, The strata behaviors in non-production side are smaller than that in production side. The overlying strata gravity mainly acts on the coal wall in front of the face and the paste filling in the goaf. The value and main influence range of advance stress in front of the face is quite small and the main influence range is less than 15m. According to the advance strata behavior characteristics of the paste filling working face, the advance support of the track roadway is changed from 3 rows to 2 rows. And the support length of each row reduces from 20m to 15m. The advance support after optimizing can reduce the labor intensity greatly and improve the working efficiency of backfill mining.

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Experimental Study on Kilometer-Deep Shaft Working Face Advancing Step and Mining-Induced Stress Distribution Law

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.353-356.1422 ◽

2013 ◽

Vol 353-356 ◽

pp. 1422-1426

Author(s):

Chang Qing Ma ◽

Bao Qing Dai ◽

Guang Peng Qin

Keyword(s):

Stress Distribution ◽

Peak Position ◽

Distribution Law ◽

Support Design ◽

Limit Value ◽

Induced Stress ◽

Working Face ◽

Coal Wall ◽

Pressure Peak ◽

Sphere Of Influence

Based on the engineering background of Tangkou in Shandong province, this thesis carries out mining-induced stress distribution law comparative study and analysis of 2313 working face which is lying below-1100 miles, using methods of theoretical analysis, numerical simulation and field measurement, and obtains the limited synergistic effect of mining-induced stress variation and working face advancing steps under the condition of kilometer-deep shaft. That is, with the increase of working face advancing steps, there will be a corresponding increase in the advanced abutment pressure peak, sphere of influence, and the distance from the peak position to the coal wall, within its limit value. The conclusion of this study have some guidance for the safe production and support design of working face in kilometer-deep shaft.

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Research on the Rock Pressure Behavior at Close-Distance Island Working Faces under Deep Goaf

Advances in Civil Engineering ◽

10.1155/2021/4714012 ◽

2021 ◽

Vol 2021 ◽

pp. 1-11

Author(s):

Shoulong Ma

Keyword(s):

Numerical Simulation ◽

Vertical Displacement ◽

Support Pressure ◽

Mining Areas ◽

Theoretical Support ◽

Working Face ◽

Coal Wall ◽

Coal Rock ◽

Advanced Support ◽

Close Distance

In order to realize the safe and efficient mining of the short-distance isolated island working face under the deep goaf area, the 120502 isolated island working face of Liuzhuang Mine was taken as the engineering background. The method of combining numerical simulation and field measurement were used comprehensively to systematically simulate and study the spatial evolution of the stress field, plastic strain field, and fracture field of coal rock during the mining process. The leading support pressure and the vertical displacement of the roof in the overlapping section and noncoinciding section of the isolated working face and the goaf above were measured on site. The results are that the peak value of the advanced support pressure of the overlap section and the nonoverlapping section is 10 m before the coal wall of the working face; the advanced support pressure of the nonoverlapping section is 33.3 MPa, and the vertical displacement of the roof is 300 mm. The advanced support pressure and the vertical displacement of the roof in the noncoincidence section were significantly higher than those in the coincidence section of 18.2 MPa and 210 mm. The results are consistent with those predicted by numerical simulation. This provides theoretical support for the safe mining of the 120502 isolated island working face in Liuzhuang Mine and, at the same time, provides a reference for the study of similar working faces in other domestic mining areas.

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Study on the Mine Pressure Law and the Pressure Frame Mechanism of an Overlying Goaf in a Shallow Coal Seam

Shock and Vibration ◽

10.1155/2021/9675137 ◽

2021 ◽

Vol 2021 ◽

pp. 1-15

Author(s):

Haifeng Zhou ◽

Qingxiang Huang ◽

Yingjie Liu ◽

Yanpeng He

Keyword(s):

Coal Pillar ◽

Coal Extraction ◽

Mine Pressure ◽

Prevention Measures ◽

Overburden Pressure ◽

Load Pressure ◽

Working Face ◽

Coal Wall ◽

Numerical Simulation Methods ◽

Mining Face

To study the problems of dynamic load pressure and frame pressure caused by the concentration of stress by coal extraction pillars during the mechanized short-distance mining of goaves in shallow coal seams, a frame pressure accident, in the Shendong Shigetai Coal Mine, during the overlying of a fully mechanized mining goaf is taken as a research example. By applying the field measurement, theoretical analysis, and numerical simulation methods, we throughly analysed the working face coal pillar, got the regular pattern of fully mechanized overburden pressure, summarized a pillar of fully mechanized working face in the overburden strata movement regularity and development characteristics, analyzed the reason and mechanism of broken coal pillar, and put forward the corresponding prevention measures and management method. The results show that when the fully mechanized mining face enters the goaf by about 3 m, the pressure arches of the lower coal face and the upper goaf arising from the extracted coal overlap. When the vertical stress is greater than the supporting force of the hydraulic support and the coal wall, a roof ejection accident may occur.

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