scholarly journals Study of Gob-Side Entry Retaining Technology with Roof Cutting under Upper Roadway Condition

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Xingen Ma ◽  
Manchao He ◽  
Xuewei Sun ◽  
Jianfeng Li ◽  
Gang He ◽  
...  
Keyword(s):  
Coal Seam ◽  
Surrounding Rock ◽  
Pressure Relief ◽  
Application System ◽  
Thick Coal Seam ◽  
Working Face ◽  
Geological Conditions ◽  
Key Technologies ◽  
Releasing Effect ◽  
System Designs

Gob-side entry retaining technology with roof cutting (GERRC) has been widely used in flat and near-flat coal seam conditions, but its application under inclined coal seam is still very deficient. In order to further improve the application system of GERRC and overcome the application difficulties under special geological conditions, this paper takes the 43073 working face of Yixin coal mine as an example to research the GERRC with upper roadway under gently inclined thick coal seam. Firstly, the difficulties in the upper entry retaining with inclined coal seam are analyzed and the corresponding key technologies and system designs are put forward. Subsequently, the roof cutting and upper entry retaining are designed in detail according to geological conditions of test working face, and the roof cutting and pressure releasing effect is analyzed by numerical simulation to expound the stress distribution and pressure releasing mechanism of surrounding rock. Finally, the upper entry retaining field test is carried out to verify the feasibility and applicability of the technology and related designs. Through field monitoring, it is found that the weighting step increases significantly, the weighting strength decreases effectively on the roof cutting side, and the pressure relief effect is obvious. Meanwhile, the maximum roof to floor convergence is 361 mm and the maximum shrinkage of both sides is 280 mm, so the retained entry can meet the reuse requirement of adjacent working face.

scholarly journals Study on Microseismic Monitoring, Early Warning, and Comprehensive Prevention of a Rock Burst under Complex Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Ke Ding ◽  
Lianguo Wang ◽  
Mei Yu ◽  
Wenmiao Wang ◽  
Bo Ren
Keyword(s):  
Coal Seam ◽  
Rock Burst ◽  
Large Diameter ◽  
Elastic Strain Energy ◽  
Surrounding Rock ◽  
Control Effect ◽  
Pressure Relief ◽  
Working Face ◽  
Geological Conditions ◽  
Microseismic Events

Rock bursts in coal mines are usually unpredictable. In view of this problem, the energy–frequency relationship and spatial distribution characteristics of microseismic events during the mining of 5305 working face in Xinhe Coal Mine under complex geological conditions were analyzed in this study. Besides, the law and precursors of rock burst occurrence in this working face were discussed. The following research results were obtained. Before the rock burst occurred in 5305 working face, the energy and frequency of microseismic events vary in the following order: “peak-drop-rise-rock burst.” The analysis on spatial characteristics of microseismic events suggests that microseismic events were mainly concentrated at the boundary between the roof and the coal seam or at the hard roof near the coal seam within 0–160 m in front of the working face, and most of the events lay on the goaf side. Moreover, the energy and frequency of microseismic events both decrease in the above region before the rock burst occurred. This “microseismic event absence” phenomenon can be regarded as one of the precursors of rock burst occurrence. In addition, a multilevel antiburst scheme was proposed for the complex conditions: (1) to adopt large-diameter boreholes pressure relief technology and key layer high-level pressure relief technology for adjusting the stress distribution in the surrounding rock of crossheading in front of the working face and dissipating elastic strain energy; (2) to determine the advance speed to be 1.5 m/d for reducing the mining disturbance; (3) to adopt full-section reinforced support of the roadway for enhancing the antiburst capacity of surrounding rock. After the implementation of this scheme, the energy and frequency of microseismic events monitored on-site changed gently, and 5305 working face was safely recovered to the stop line position. The scheme boasts a remarkable rock burst prevention and control effect.

scholarly journals Determination of cyclic filling length in gob-side entry retained with roadside filling and its application

2020 ◽  
Author(s):  
Zizheng Zhang ◽  
Jianbiao Bai ◽  
Xianyang Yu ◽  
Weijian Yu ◽  
Min Deng ◽  
...  
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Difference Method ◽  
Suggested Method ◽  
Stress Difference ◽  
Thick Coal Seam ◽  
Mechanics Model ◽  
Working Face ◽  
Geological Conditions ◽  
The Relationship

Abstract Gob-side entry retained with roadside filling (GER-RF) plays a key role in achieving coal mining without pillar and improving the coal resource recovery rate. Since there are few reports on the cyclic filling length of GER-RF, a method based on the stress difference method is proposed to determine the cyclic filling length of GER-RF. Firstly, a stability analysis mechanics model of the immediate roof above roadside filling area in GER was established, then the relationship between the roof stress distribution and the unsupported roof length was obtained by the stress difference method. According to the roof stability above roadside filling area based on the relationship between the roof stress and its tensile strength, the maximum unsupported roof length and rational cyclic filling length of GER-RF. Combined with the geological conditions of the 1103 thin coal seam working face of Heilong Coal Mine and the geological conditions of the 1301 thick coal seam working face of Licun Coal Mine, this suggested method was applied to determine that the rational cyclic filling lengths of GER-RF were 2.4 m and 3.2 m, respectively. Field trial tests show that the suggested method can effectively control the surrounding rock deformation along with rational road-in support and roadside support, and improve the filling and construction speed.

scholarly journals Analysis of pressure relief and outburst prevention effect and mining depth effect of floor roadway in single serious outburst coal seam

2021 ◽  
Vol 267 ◽  
pp. 01051
Author(s):  
Guohong Chen
Keyword(s):  
Coal Seam ◽  
Field Test ◽  
Surrounding Rock ◽  
Test Results ◽  
Pressure Relief ◽  
Depth Effect ◽  
Mining Depth ◽  
Geological Conditions ◽  
Ground Stress ◽  
Outburst Coal Seam

In order to solve the serious problem of single serious outburst coal seam gas disaster, based on the gas geological conditions of Jiangxi Fengcheng Qujiang company, theoretical analysis, numerical simulation, field test and other comprehensive research methods were used to analyze the partition fracture law of roadway surrounding rock under different mining depth conditions. The results show that: under the conditions of high ground stress, high temperature and other environmental conditions, the radius of pressure relief loose circle of surrounding rock of roadway is significantly increased, and it is significantly larger than that of shallow part. In the deep area of - 800m elevation, the distance between floor roadway and coal seam is optimized to be 12 ~ 15m. The field test results show that the original permeability coefficient of overlying coal seam of floor roadway increases by 55.74 times, and the pressure relief effect is good.

Stress Shell Mechanical Mechanism of Fully-Mechanized Face Enhancing the Upper Limit for Coal Mining and Risk Analysis of Support Break-Off

2012 ◽  
Vol 524-527 ◽  
pp. 466-470
Author(s):  
Jun Ling Hou ◽  
Yan Sun
Keyword(s):  
Stress Distribution ◽  
Coal Seam ◽  
Coal Mining ◽  
Surrounding Rock ◽  
Mechanical Environment ◽  
Upper Limit ◽  
Working Face ◽  
Distribution Rule ◽  
Geological Conditions ◽  
Mining Face

Based on the geological conditions and specific mining technology conditions of the 11014 mining face of Panbei mine in HuaiNan mining group ,using the FLAC3D software, simulate the stress distribution rule and disruption field distribution rule of surrounding rock of Fully-Mechanized face enhancing the upper limit for coal mining along the tendency and trend of coal seam by different mining speed of 6 m/d, 4 m/d and 2 m/d. draw the conclusion that enhancing the mining speed can alleviate the pressure of the working face ,improve the working face mechanical environment,and reduce the extent of the failure field.It provides the theory basis and reference for Fully-Mechanized face enhancing the upper limit for coal mining under similar conditions.

The Numerical Simulation and Supporting Design of Gob-Side Entry Retaining in Gradient Medium Thick Coal Seam

2013 ◽  
Vol 368-370 ◽  
pp. 1812-1815 ◽  
Author(s):  
Yong Qin Zhang ◽  
Le Le Sun ◽  
Wei Zhong Zhang ◽  
Li Dan Cao
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Surrounding Rock ◽  
Rock Deformation ◽  
Deformation Characteristics ◽  
Thick Coal Seam ◽  
Geological Conditions ◽  
Immediate Roof ◽  
The Impact ◽  
Surrounding Rock Deformation

In order to solve the technical problem of gob-side entry retaining in inclined coal seam, combined with the practical mining conditions in a certain mine, this paper adopts the discrete element method, applies numerical simulation to analyze inclined coal seam gob-side entry retaining with three different supporting ways, and studies surrounding rock deformation characteristics of gob-side entry retaining. The research results show that the filling body upper boundary for right side can control the roadway surrounding rock deformation better compared with the boundary is used as the hypotenuse; Meanwhile, the pressure of surrounding rock of coal seam gob-side entry retaining is mainly from the impact of the immediate roof natural fall of the upper goaf tilt and the weight of caving coal gangue and coal seam of immediate roof above; According to the surrounding rock deformation characteristics of coal seam remain gateway along goaf, it is determined to use combined supporting method of concrete filling in roadway sides and anchor wire rope supporting inside the roadways, providing the design basis of gob-side entry retaining in coal seam for the similar geological conditions.

scholarly journals Reasonable Arrangement of High-Level Orientation Extraction Boreholes of Pressure Relief Gas in Overlying Strata under High-Strength Fully Mechanized Mining in Low-Gas-Thick-Coal Seam

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Han Gao ◽  
Xuanping Gong ◽  
Xiaoyu Cheng ◽  
Rui Yu ◽  
Hui Wang
Keyword(s):  
Coal Seam ◽  
Gas Flow ◽  
High Strength ◽  
Distribution Characteristics ◽  
Pressure Relief ◽  
Gas Field ◽  
Thick Coal Seam ◽  
Gas Accumulation ◽  
Working Face ◽  
Gas Control

In order to solve the problem of pressure relief gas control under high-strength fully mechanized top-coal caving in low-gas-thick-coal seams, this paper studies the evolution of overburden structures and the distribution characteristics of fissure fields during the initial and stable period of working face by physical simulation and numerical analysis. The mathematical model of coupling between mining fracture field and pressure relief gas field is established. The results reveal the distribution characteristics of pressure relief gas field that considers mining-induced fissure field. According to the distribution of mining gas accumulation area, the high directional long boreholes have been put forward to control the pressure relief gas in goafs, and the effect has been tested. The results show that the initial pressure and three periodic pressures occurred from the cutting hole to 135 m in the initial mining period of the working face. The height of collapse zone developed to 22 m, and fracture height developed to 75 m. The development height of caving zone is stable at 25∼27 m, and the development height of fissure zone is stable at 75∼95 m. The process and distribution of pressure relief gas flow in goaf are obtained by solving the numerical model of pressure relief gas flow in mining fissure field. The gas accumulation area is located within 25∼55 m from return laneway and 25∼50 m from the roof of coal seam. After the implementation of high directional long drilling gas drainage technology in the initial mining period and the stable mining period, good results have been obtained in the gas control, where the average concentration of gas extraction is 5.8%, the average gas flow rate is 0.71 m3/min, and the gas concentration in upper corner and return air is less than 0.8%. The results can provide a reference for pressure relief gas control under similar conditions.

Numerical Analysis of Influencing Factors of Stability in Thick Coal Seam Mining Roadway

2012 ◽  
Vol 256-259 ◽  
pp. 1453-1457
Author(s):  
Zhi Hua Li ◽  
Xin Zhu Hua ◽  
Ke Yang ◽  
Ruo Jun Zhu ◽  
De Sheng Zhou
Keyword(s):  
Coal Seam ◽  
Abutment Pressure ◽  
Surrounding Rock ◽  
Rock Body ◽  
Thick Coal Seam ◽  
Mining Depth ◽  
Working Face ◽  
Face Length ◽  
Seam Mining ◽  
Mining Height

The FLAC-3D software was used to study the surrounding rock displacement and the side abutment pressure distribution laws about roadway in thick coal seam. Based on this model, through change the mining height, working face length and mining depth, the differences of roadway underground pressure characteristics were analyzed between thick coal seam working face and normal working face. The results indicate that: ①the displacement of roadway surrounding rock increases with the increase of mining depth and mining height, the closer to the coal wall the larger of the increase range of roadway displacement. ②the peak of side abutment pressure increases with the increase of mining depth and mining height, the peak district of the stress will move toward the inner department of rock body. ③ the effect of working face length on the roadway displacement and the side abutment pressure is very feeble.

scholarly journals Study on the “Pressure Relief and Yielding Support” Joint Prevention and Control Technology for the Weak Impact Roadway in the Extremely Thick Coal Seam

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Zengde Yin ◽  
Jinxiao Liu ◽  
Wenbin Sun ◽  
Kebao Guo ◽  
Feng Zhang
Keyword(s):  
Coal Seam ◽  
Prevention And Control ◽  
Surrounding Rock ◽  
Control Technology ◽  
Pressure Relief ◽  
Thick Coal Seam ◽  
Roadway Support ◽  
Yielding Support ◽  
And Control ◽  
The Impact

Weak impact occurs during roadway excavation in some extremely thick coal seams in China. Although this hazard is not enough to destroy the roadway, it will cause fracturing and large deformation of the roadway surrounding rock, resulting in the fracturing of bolts and anchor cables and bringing great difficulties to roadway support. In the hope of solving this problem, firstly, the reason for impact occurrence in the roadway of the extremely thick coal seam is analyzed from the perspective of energy. Then, the surrounding rock fracture evolution in such a roadway is explored by means of numerical simulation, microseism, and borehole observation. Furthermore, the “pressure relief and yielding support” joint prevention and control technology is proposed and applied to Yili No. 1 Coal Mine. The field engineering application results show that the joint prevention and control technology can effectively reduce the impact energy and ensure the stability of the roadway surrounding rock in the extremely thick coal seam. The research findings can provide a theoretical foundation for the roadway support of the same type.

scholarly journals Determination of Cyclic Filling Length in Gob-Side Entry Retained with Roadside Filling and Its Application

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Zizheng Zhang ◽  
Jinlin Xin ◽  
Jianbiao Bai ◽  
Xianyang Yu ◽  
Weijian Yu ◽  
...  
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Difference Method ◽  
Suggested Method ◽  
Stress Difference ◽  
Thick Coal Seam ◽  
Mechanics Model ◽  
Working Face ◽  
Geological Conditions ◽  
The Relationship

Gob-side entry retained with roadside filling (GER-RF) plays a key role in achieving coal mining without pillar and improving the coal resource recovery rate. Since there are few reports on the cyclic filling length of GER-RF, a method based on the stress difference method is proposed to determine the cyclic filling length of GER-RF. Firstly, a stability analysis mechanics model of the immediate roof above the roadside filling area was established, and then, the relationship between the roof stress distribution and the unsupported roof length was obtained by the stress difference method. According to the roof stability above the roadside filling area based on the relationship between the roof stress and its tensile strength, the maximum unsupported roof length and rational cyclic filling length were determined. Combined with the geological conditions of the 1103 thin coal seam working face of Heilong Coal Mine and the 1301 thick coal seam working face of Licun Coal Mine, the suggested method was applied to determine that the rational cyclic filling lengths were 2.4 m and 3.2 m, respectively. Field trial tests show that the suggested method can effectively control the surrounding rock deformation along with rational road-in support and roadside support and improve the filling and construction speed.

scholarly journals Disastrous Mechanism of Water Discharge in Abandoned Gob above the Stope in Mining Extra-Thick Coal Seam

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Haixiao Lin ◽  
Feng Yang ◽  
Zhengzheng Cao ◽  
Yue Wang ◽  
Xiaojian Jiao
Keyword(s):  
Coal Seam ◽  
Water Discharge ◽  
Mining Area ◽  
Thick Coal Seam ◽  
Research Results ◽  
Key Stratum ◽  
Working Face ◽  
Geological Conditions ◽  
Induced Fractures ◽  
Seam Mining

The Datong mining area is a typical double system coal seam mining area in China, where the Jurassic and Carboniferous coal seams are mined simultaneously. The upper Jurassic coal seam has been largely mined, leaving a large amount of gob area. Besides, a large amount of harmful water is accumulated. With the exploitation of the 3-5# extra-thick coal seam in the Carboniferous system, the scope of overburden damage is greatly increasing, and the mining fracture field is further developed. Once the mining-induced fractures connect with the overlying gob, it is easy to induce the water discharge disaster. With the mining geological conditions of the 8202 working face in the Tongxin coal mine as references, the disastrous mechanism of water discharge in the abandoned gob above the stope in the mining extra-thick coal seam is researched by numerical simulation with the UDEC numerical software, and the research results are obtained. The water in the overlying gob percolates through the mining-induced fractures in the higher key layer forming a “shower” seepage pattern. The water in the above gob converges in the key fracture channel, flowing into the working face. The seepage in the fractures in the high key stratum experiences the process of increase, decrease, and stabilization, related with the stretching and extrusion deformation between the high key stratum blocks. Compared with other fractures, the flow rates in the No.2 and No.4 fractures in the far field key lay are larger, because the fractures are in the tension state, forming the “saddle-shaped” flow pattern. The influencing distance of mining-induced seepage is about 80 m in front of the working face. The research results provide a guided reference for the prediction and prevention of water discharge disaster in an abandoned gob above the stope in a mining extra-thick coal seam.

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