scholarly journals Simulation Study of the Roof Fracture Pattern of a Horizontal Sublevel Caving in a Steeply Inclined Thick Coal Seam

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Xin Kang ◽  
Sheng-li Yang ◽  
Ping Zhan ◽  
Liang-hui Li
Keyword(s):  
Coal Seam ◽  
Fracture Pattern ◽  
Tensile Failure ◽  
Experimental Simulation ◽  
Mining Equipment ◽  
Horizontal Section ◽  
Thick Coal Seam ◽  
Toppling Failure ◽  
Sublevel Caving ◽  
Simulation Results

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.

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

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.

A Coal Mine Hydraulic Support Design and Type Selection of Medium Thick Coal Seam

2014 ◽  
Vol 633-634 ◽  
pp. 1128-1132
Author(s):  
Li Rong Zhang
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Simulation Method ◽  
Bottom Plate ◽  
Mining Equipment ◽  
Hydraulic Support ◽  
Support Design ◽  
Thick Coal Seam ◽  
Technical Parameters ◽  
Selection Of

Design and selection of hydraulic support is the core of coal mine fully mechanized mining equipment selection and matching, determine the hydraulic supporting strength Using the numerical simulation method and shallow buried depth of roof structure of theoretical calculation method, determines the necessary technical parameters such as the support frame, the bracket height and the bottom plate pressure According to the coal seam thickness and coal seam structure, which has the instructive meaning in application.

scholarly journals Thermal infrared characteristics of rock strata fracture in steeply inclined and extra thick coal seam

2020 ◽  
Vol 24 (6 Part B) ◽  
pp. 3933-3940
Author(s):  
Yan-Bin Yang ◽  
Feng Cui
Keyword(s):  
Coal Seam ◽  
Infrared Radiation ◽  
Thermal Infrared ◽  
Horizontal Section ◽  
Thick Coal Seam ◽  
Mining Depth ◽  
Movement Rules ◽  
The Relationship ◽  
Thermal Infrared Radiation ◽  
Rock Strata

In view of the complexity of the rules of rock strata fracture in steeply inclined and extra thick coal seam, the mining method of horizontal section top coal caving was put forward. In this paper, the physical similarity simulation model is established to analyze the movement rules of rock strata. The relationship between the form of rock strata fracture and the thermal infrared radiation is analyzed according to studying the characteristics of the thermal infrared radiation temperature of the rock strata fracture. Meanwhile, the changes characteristics of abnormal area of thermal infrared radiation were mastered, and the precursors of thermal infrared radiation of rock strata fracture were predicted. The results showed that the rock strata fracture form of steeply inclined and extra thick coal seam is related to the mining depth.

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

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

scholarly journals Longwall Top-Coal Caving Mechanism and Cavability Optimization with Hydraulic Fracturing in Thick Coal Seam: A Case Study

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4832
Author(s):  
Zhaohui Wang ◽  
Yuesong Tang ◽  
Hao Gong
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Shear Failure ◽  
Tensile Failure ◽  
Hydraulic Fractures ◽  
Thick Coal Seam ◽  
Face Length ◽  
The Face ◽  
Upper Level ◽  
Longwall Top Coal Caving

Longwall top-coal caving mechanisms and cavability optimization with hydraulic fracturing are analysed in this study. Based on the geological and geotechnical conditions of the Dongzhouyao coal mine, it is revealed that top-coal failure mechanisms are dominated by both compressive and tensile stresses. Ahead of the face line, shear failure initiates at the lower level of the top-coal and propagates to the upper level. Compressive stress-induced damage leads to obvious deterioration in tensile strength, causing the onset of tensile failure in the top-coal behind the face line. Accumulated plastic strain (APS) is selected as a top-coal cavability indicator. The cavability degrades gradually at the higher elevation of the top-coal while it is greatly strengthened as the top-coal approaches closer to the face line. In a thick coal seam without hydraulic fractures, the maximum APS occurs at the middle section of the face length in the Longwall top-coal caving (LTCC) panel. After hydraulic fracturing, top-coal cavability is significantly enhanced. But the spatial distribution of the APS transitions from uniform to non-uniform type due to the existence of hydraulic fractures, causing great variety in the cavability along the panel width. With increasing fracture intensity and fracture size, the failure zone expands significantly ahead of the longwall face, which means the cavability becomes increasingly favourable.

Investigation on Fully Mechanized Mining Technology of Thin Coal Seam under the Near Goaf

2014 ◽  
Vol 998-999 ◽  
pp. 426-429 ◽  
Author(s):  
Chuan Wei Zang ◽  
Miao Chen ◽  
Er Yu Wang
Keyword(s):  
Coal Seam ◽  
High Grade ◽  
Mining Equipment ◽  
Mining Technology ◽  
Thick Coal Seam ◽  
Thin Coal Seam ◽  
Roof Structure ◽  
Working Space ◽  
Mining Methods

With the resources exhaustion of medium-thick and thick coal seam, the mining technology of thin coal seam has attracted more attention. Due to the little working space for mining in thin coal seam, blasting mining and high-grade conventional mining are main mining methods that were used in thin coal seam. Taking the 17th coal seam of Liyan mine as an example, in this paper we analyze the roof structure of the lower thin coal seam under the goaf of the upper coal seam. The fully mechanized mining equipment is selected on the basis of the new roof structure and applied in field. Finally, safe and efficient mining is achieved by improving the adaptability of the equipment.

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

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.

scholarly journals Cooperative Control Mechanism of Long Flexible Bolts and Blasting Pressure Relief in Hard Roof Roadways of Extra-Thick Coal Seams: A Case Study

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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