Segment pre-blasting application on 52 m sublevel caving of steep and thick coal seam under complex conditions

Application of a horizontal section top-coal caving in a steeply inclined thick coal seam not only effectively resolves the problem of the large dip angle of the coal seam and slipping and dumping of mining equipment but also significantly reduces the tunnel drivage ratio and improves the extraction yield. In addition, it allows for a safe and efficient mining from a steeply inclined thick coal seam. In this paper, the roof fracture pattern of a steeply inclined thick coal seam has been studied by a similar simulation experiment. The results of the simulation are consistent with those of the numerical calculations, thus verifying the accuracy of the simulation. The experimental simulation results show that the roof can form a step-like toppling failure pattern after drawing the coal, and it is difficult to release a triangular coal mass near the floor, which is the main concentration area of coal loss. The numerical simulation results show that, with the excavation of the coal seam, the rock mass around the goaf produces plastic failure, and the damage is mainly concentrated in the roof area. The upper part of the goaf mainly shows a tensile failure, while the other areas mainly show yield failure.

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Effect of roof movement on gas flow in an extremely thick coal seam under fully mechanized sublevel caving mining conditions

Energy Science & Engineering ◽

10.1002/ese3.541 ◽

2019 ◽

Vol 8 (3) ◽

pp. 677-688

Author(s):

Haijun Guo ◽

Xianzhang Li ◽

Hao Cui ◽

Kaixuan Chen ◽

Yuanyuan Zhang

Keyword(s):

Coal Seam ◽

Gas Flow ◽

Thick Coal Seam ◽

Sublevel Caving ◽

Mining Conditions

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Segment pre-blasting application on 52 m sublevel caving of steep and thick coal seam under complex conditions

Rock Stress and Earthquakes ◽

10.1201/b10555-62 ◽

2010 ◽

pp. 355-359

Author(s):

S Miao ◽

X Lai

Keyword(s):

Coal Seam ◽

Thick Coal Seam ◽

Sublevel Caving

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Research on the Influence of Mining Height on the Movement Characteristics of Overlying Strata during Extremely Thick Coal Seam Fully Mechanized Sublevel Caving Mining

Advances in Civil Engineering ◽

10.1155/2021/6661581 ◽

2021 ◽

Vol 2021 ◽

pp. 1-10

Author(s):

Yongkang Yang ◽

Jie Wei ◽

Chenlong Wang

Keyword(s):

Coal Seam ◽

Physical Simulation ◽

Quadratic Polynomial ◽

Tensile Failure ◽

Thick Coal Seam ◽

Sublevel Caving ◽

Height Increase ◽

Supporting Force ◽

Mining Height ◽

Overlying Strata

The study of the effects of mining height on overlying strata movement and underground pressure characteristics during extremely thick coal seam fully mechanized sublevel caving mining is very important for choosing the reasonable mining height and the support. Based on the geological setting and mining conditions at the Xiegou Coal Mine, the results of the physical simulation test and the numerical simulation technology will be used. Some conclusions can be drawn as follows: (1) With the mining height increase, the top coal gradually converted from tensile failure to shear damage, and the coal wall gradually transformed from shear failure to tensile damage. (2) When the mining height is 7.5 m, the full-seam collapse distance, the immediate first weighting interval, and the main roof first weighting length are shorter than that when the mining height is 4m, and the periodic weighting length for the two mining heights is almost the same. (3) With mining height increase, the initial mining stage and the transition stage become shorter, and the production rates become better. (4) The law of the abutment pressure peak and the sphere of influence increase slightly, and the working resistance of support needed to be strengthened. (5) The subsidence quantity of the top coal in the control area increases along with the mining height in a quadratic polynomial way but decreases along with the initial supporting force in a negative logarithmic rule. (6) After assigning the subsidence, the regression relation between the initial supporting force and the mining height is a quadratic polynomial.

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Study on Strata Behaviors of the Coal Face with Sublevel Caving in Hugely-Thick Coal Seam in Qianqiu Coal Mine

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.671-674.1150 ◽

2013 ◽

Vol 671-674 ◽

pp. 1150-1155

Author(s):

Xin Xian Zhai ◽

Yan Wei Zhai ◽

Shi Wei Zhang

Keyword(s):

Coal Seam ◽

Coal Mine ◽

High Efficiency ◽

Production Model ◽

Practical Significance ◽

Coal Face ◽

Thick Coal Seam ◽

Observation Methods ◽

Sublevel Caving ◽

Safety Production

Qianqiu Coal Mine, Yima Coal Group Company Limited, China, has been mining the gently-inclined and hugely-thick coal seam #2-3. The overburden above the coal seam has hugely-thick conglomerate strata with more than 400m thickness, which has significant effects on the strata behaviors of the coal face with sublevel caving. Therefore, study on strata behaviors has an important practical significance to surrounding rocks control and safety production at the coal face. Using theoretical analysis and field observation methods, the following conclusions can be drawn: (1) the surrounding rocks of the coal face with sublevel caving belongs to difficult control one, i.e., it is the surrounding rocks control of roof and floor at the coal face that is difficult. At last, hydraulic supports with sublevel caving of pattern ZF7000-18/28 and their reasonable matching equipment were chosen. (2) The law of strata behaviors of the coal face was observed. Strata behaviors of the coal face were significant and inconsistent at different coal face zones. The parameters of roof weighting interval and roof weighting strength at the coal face were obtained. The maximum value of supporting resistance during periodical weighting was 4307.70kN, being 61.54% of supports rating resistance. Therefore, the supports at the coal face had a higher reliability. Mine production-model with one-mine and one-face can be realized, which promotes the construction of a modernization mine with high production and high efficiency.

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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.

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