scholarly journals Numerical Study on Soft Coal Pillar Stability in an Island Longwall Panel

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Qingyun Xu ◽  
Jian-Biao Bai ◽  
Shuai Yan ◽  
Rui Wang ◽  
Shaoxu Wu
Keyword(s):  
Plastic Zone ◽  
Numerical Study ◽  
Deformation Characteristic ◽  
Coal Pillar ◽  
Surrounding Rock ◽  
Pillar Width ◽  
Soft Coal ◽  
Geological Conditions ◽  
Longwall Panel ◽  
Coal Pillars

Roadway support and management of longwall panels in an island soft coal panel are always difficult work. In a test mine, stress distribution, deformation characteristic, and plastic zone distribution around the roadway and coal pillars in the development and mining periods were investigated with respect to the widths of different coal pillars using theoretical and simulation methods. The most reasonable width of coal pillars was comprehensively determined, and the field test was conducted successfully. The results show that a reasonable width of coal pillars is 7.0–8.2 m using the analytical method. The distribution of vertical stress in the coal pillars showed an asymmetric “double-hump” shape, in which the range of abutment pressure was about 26.0–43.0 m, and the roadway should be laid away from stress concentration. When the coal pillar width is 5.0–7.0 m, deformation of the roadway is half that with 8.0–10.0 m coal pillar in the development and mining period. The plastic zone in the surrounding rock firstly decreases and increases with increasing coal pillar width; the smallest range occurs with a coal pillar width of 5.0 m. Finally, a reasonable width for coal pillars in an island panel was determined to be 5.0 m. Industrial practice indicated that a coal pillar width of 5.0 m efficiently controlled deformation of the surrounding rock, which was an important basis for choosing the width of coal pillars around gob-side entries in island longwall panels with similar geological conditions.

scholarly journals Deviatoric Stress Evolution Laws and Control in Surrounding Rock of Soft Coal and Soft Roof Roadway under Intense Mining Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Dongdong Chen ◽  
Chunwei Ji ◽  
Shengrong Xie ◽  
En Wang ◽  
Fulian He ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Plastic Zone ◽  
Theoretical Calculations ◽  
Coal Pillar ◽  
Surrounding Rock ◽  
Deviatoric Stress ◽  
Anchor Cable ◽  
Soft Coal ◽  
Working Face ◽  
Failure Line

Aiming at the problem of large deformation and instability failure and its control of soft coal and soft roof roadway under intense mining, laboratory experiments, theoretical calculations, Flac3D numerical simulation, borehole peeping, and pressure observation were used to study the deflection characteristics of the deviatoric stress of the gas tailgate and the distribution and failure characteristics of the plastic zone in the mining face considering the strain softening characteristics of the roof and coal of roadway, and then the truss anchor cable-control technology is proposed. The results show the following: (1) The intense mining influence on the working face will deflect the peak deviatoric stress zone (PDSZ) of the surrounding rock of the gas tailgate. The influence distance of PDSZ is about 20 m in advance and 60 m in lag; the PDSZ at the gob side of the roadway is located in the range of 3–5.5 m from the surface of the coal pillar, while the coal wall side is mainly located in the range of 3–4.5 m at the shoulder corner and bottom corner of the solid coal. (2) The intense mining in the working face caused the nonuniform expansion of the surrounding rock plastic area of the gas tailgate. The two shoulder angles of the roadway and the bottom of the coal pillar have the largest damage range, and the maximum damage location is the side angle of the coal pillar (5 m). Angle and bottom angle of coal pillar are the key points of support control. (3) The plastic failure line of the surrounding rock of the gas tailgate is always between the inner and outer contours of the PDSZ, and the rock mass in the PDSZ is in a stable and unstable transition state, so the range of anchor cable support should be cross plastic failure line. (4) The theoretical calculations and numerical simulation results agree well with the drilling peep results. Based on the deflection law of the PDSZ and the expansion characteristics of the plastic zone, a truss anchor cable supporting system with integrated locking and large-scale support function is proposed to jointly control the roof and the two sides, which effectively solves the problem of weak surrounding rock roadway under severe mining deformation control problems realizing safety and efficient production in coal mines under intense mining.

scholarly journals A physical model study of surrounding rock failure near a fault under the influence of footwall coal mining

2020 ◽  
Author(s):  
Shukun Zhang ◽  
Lu Lu ◽  
Ziming Wang ◽  
Shuda Wang
Keyword(s):  
Rock Mass ◽  
Physical Model ◽  
Hanging Wall ◽  
Coal Pillar ◽  
Vertical Displacement ◽  
Surrounding Rock ◽  
Pillar Width ◽  
Model Study ◽  
Working Face ◽  
Coal Pillars

AbstractA study of the deformation of the surrounding rock and coal pillars near a fault under the influence of mining is conducted on a physical model for the design of coal pillars to support and maintain the roofs of adjacent fault roadways. This research is based on the 15101 mining face in the Baiyangling Coal Mine, Shanxi, China, and uses simulation tests similar to digital speckle test technology to analyse the displacement, strain and vertical stress fields of surrounding rocks near faults to determine the influence of the coal pillar width. The results are as follows. The surrounding rock of the roadway roof fails to form a balance hinge for the massive rock mass. The vertical displacement, vertical strain and other deformation of the surrounding rock near the fault increase steeply as the coal pillar width decreases. The steep increase in deformation corresponds to a coal pillar width of 10 m. When the coal pillar width is 7.5 m, the pressure on the surrounding rock near the footwall of the fault suddenly increases, while the pressure on the hanging wall near the fault increases by only 0.35 MPa. The stress of the rock mass of the hanging wall is not completely shielded by the fault, and part of the load disturbance is still transmitted to the hanging wall via friction. The width of the fault coal pillars at the 15101 working face is determined to be 7.5 m, and the monitoring data verify the rationality of the fault coal pillars.

scholarly journals Roadway Surrounding Rock under Multi-Coal-Seam Mining: Deviatoric Stress Evolution and Control Technology

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Dongdong Chen ◽  
En Wang ◽  
Shengrong Xie ◽  
Fulian He ◽  
Long Wang ◽  
...  
Keyword(s):  
Plastic Zone ◽  
Coal Seam ◽  
Coal Pillar ◽  
Surrounding Rock ◽  
Deviatoric Stress ◽  
Mine Pressure ◽  
Coal Face ◽  
Surrounding Rock Control ◽  
Seam Mining ◽  
Peak Value

Multi-coal-seam mining creates surrounding rock control difficulties, because the mining of a coal face in one seam can affect coal faces in another. We examine the effects of multi-coal-seam mining on the evolution of the deviatoric stress distribution and plastic zone in the roadway surrounding rock. In particular, we use numerical simulation, theoretical calculation, drilling detection, and mine pressure observation to study the distribution and evolution characteristics of deviatoric stress on Tailgate 8709 in No. 11 coal seam in Jinhuagong mine when the N8707 and N8709 coal faces in No. 7-4 coal seam and the N8707 and N8709 coal faces in No. 11 coal seam are mined. The evolution laws of deviatoric stress and the plastic zone of roadway surrounding rock in the advance and behind sections of the coal face are studied, and a corresponding control technology is proposed. The results show that the peak value of deviatoric stress increases with the advance of the coal face, and the positions of the peak value of deviatoric stress and the plastic zone become deeper. The deflection angle of the peak stress after mining at each coal face and the characteristics of the peak zone of deviatoric stress and the plastic zone of the roadway surrounding rock under the disturbance of multi-coal-seam mining are determined. In conclusion, the damage range in the roadway roof in the solid-coal side and coal pillar is large and must be controlled. A combined support technology based on high-strength and high pretension anchor cables and truss anchor cables is proposed; long anchor cables are used to strengthen the support of the roadway roof in the solid-coal side and coal pillar. The accuracy of the calculated plastic zone range and the reliability of the combined support technology are verified through drilling detection and mine pressure observation on site. This research can provide a point of reference for roadway surrounding rock control under similar conditions.

scholarly journals Modeling the Spatial and Temporal Evolution of Stress during Multiworking Face Mining in Close Distance Coal Seams

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Yong Zhang ◽  
Jinkun Yang ◽  
Jiaxuan Zhang ◽  
Xiaoming Sun ◽  
Chen Chen ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Stress Distribution ◽  
Temporal Evolution ◽  
Coal Pillar ◽  
Coal Seams ◽  
Geological Conditions ◽  
Coal Pillars ◽  
The Stability ◽  
Close Distance ◽  
Close Distance Coal Seams

Mining in close distance coal seams (CDCSs) is frequently associated with engineering disasters because of the complicated nature of stress distribution within CDCSs. In order to establish a layout of a roadway to minimize the occurrence of disasters associated with mining CDCS, here the spatial and temporal evolution of stress distribution during the multiworking face mining of a CDCS was explored through numerical simulation based on the engineering and geological conditions of the Nantun Coal Mine. The numerical simulation results indicate that, after the extraction of adjacent multiple working faces, the spatial distribution of stress can be characterized with areas of increased, reduced, and intact stress. The superposed stress of inclined seams that are very close to each other propagates through coal pillars in the bottom floor, and this propagation follows neither the line along the axis of the coal pillar nor the line perpendicular to the direction of the floor. It instead propagates along a line angled with the axis of the coal pillar. The roadway can be arranged in the area with reduced stress, to improve its the stability. Based on the computed spatial and temporal evolution of stress, an optimized layout of roadway was proposed. This layout features a reasonable interval between the mining roadway and a minimal proportion of increased stress areas along the mining roadway and is aligned with geological structures.

scholarly journals Research on Failure Mechanism and Strengthening of Broken Roadway Affected by Upper Coal Pillar

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Fulian He ◽  
Zheng Zheng ◽  
Hengzhong Zhu ◽  
Bo Yang
Keyword(s):  
Stress Distribution ◽  
Failure Mechanism ◽  
Coal Pillar ◽  
Control Area ◽  
Surrounding Rock ◽  
Horizontal Line ◽  
Protective Function ◽  
Working Face ◽  
Coal Pillars ◽  
Roadway Deformation

The principal stress difference is introduced as a new evaluation index in order to better understand the failure mechanism of roadways affected by upper coal pillars and characterize failure of rock mass. Compared with traditional methods, it facilitates quantitative analysis. Moreover, we combine the semiplane theory and we obtain the stress distribution on the coal pillar’s bedrock and the strengthening control area from the “change point” position along a 21 m horizontal line. The influence of multiple stresses induced from mining on a roadway is analyzed. It is found that rock failure is most likely while mining the 051606 working face, followed by mining the 051604 working face, and the stress influence on the upper pillar has the lowest failure probability. In addition, based on the asymmetry of the surrounding rock stress distribution, this study proposes strengthening control technology of surrounding rock on the basis of a highly stressed bolting support and anchor cable, adding to the steel ladder beam, steel mesh, and shed support’s protective function to the roadway’s roof and ribs. Finally, through field observations, it is concluded that the roadway deformation is within the controllable range.

Optimization on Gateway Section of Soft Coal Seam and Hard Roof and Supporting Technology

2011 ◽  
Vol 90-93 ◽  
pp. 622-625
Author(s):  
Lu Chen ◽  
Chuan Wei Zang ◽  
Feng Hai Yu ◽  
Xiang Kun Yu
Keyword(s):  
Plastic Zone ◽  
Coal Seam ◽  
Field Application ◽  
Geological Condition ◽  
Hard Roof ◽  
Soft Coal ◽  
Production Safety ◽  
Geological Conditions ◽  
The Stability ◽  
Soft Coal Seam

Support invalidity of a roadway have a largely influence on production safety of coal mines, especially the soft coal roadway, which deforms heavily. To solve this problem, it began from the gateway section optimization, based on the actual geological condition of Chang-gouyu Mine. The computational model was established up to optimize tunnel shapes using FLAC3D. The scopes of plastic zone, stress field, displacement field were compared and analysed for different shapes of roadway. The irregular trapezoid section is adopted, then the bolt support parameters were designed and field application was done. By using the irregular trapezoid, the stress distribution around the roadway is improved and the deformation and plastic zone is decreased. Under the geological conditions of the soft coal seam and hard roof strata, the stability of roadway was effectively controlled by using optimized trapeziform cross-section and bolting support.

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 Simulation Analysis and Engineering Application of Retaining Width of Waterproof Coal Pillar in Island Working Face

2021 ◽  
Author(s):  
Lili Zheng ◽  
Zheng Gao
Keyword(s):  
Service Life ◽  
Simulation Analysis ◽  
Engineering Application ◽  
Coal Pillar ◽  
Surrounding Rock ◽  
Simulation Research ◽  
Working Face ◽  
Before And After ◽  
Mining Face ◽  
Coal Pillars

The old mining area in Pingdingshan coalfield has the following problems: long mining service life, many remaining coal pillars, and great difficulty in mining; to extend the service life of the mine, realize cost saving and efficiency increasing, it is urgent to recover the remaining coal pillars, but the mining of isolated island face faces the problem of reasonable retention of waterproof coal pillars, if the protection is not good, it is easy to cause mine water damage and increase the mining cost. Therefore, in view of the practical engineering problems faced by the field, aiming at eliminating or reducing the goaf water disaster, this paper adopts numerical simulation research methods to optimize the original design scheme and carry out comparative analysis, dynamically reappear the surrounding rock stress field, displacement field and plastic failure law under multi face mining and roadway mining, and carry out engineering practice application. The results show that there is a certain thickness of elastic core area before and after mining with 25m coal pillar width. The deformation of surrounding rock is small, which is conducive to roadway maintenance, without obvious stress concentration. It can meet the actual needs of the project. The mining face has achieved safe mining, without water inrush accident in the goaf, and the coal resources have been recovered to the maximum extent. The research results are left over to similar mining areas in China The safe recovery of coal pillar can be used for reference.

scholarly journals Research on the Reasonable Coal Pillar Width and Surrounding Rock Supporting Optimization of Gob-Side Entry under Inclined Seam Condition

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Li-li Jiang ◽  
Zeng-qiang Yang ◽  
Gang-wei Li
Keyword(s):  
Stress Field ◽  
Control Mechanism ◽  
Coupling Effect ◽  
Coal Pillar ◽  
Surrounding Rock ◽  
Control Technology ◽  
Pillar Width ◽  
Monitoring Methods ◽  
Anchor Cable ◽  
Surrounding Rock Control

In order to study the optimal coal pillar width and surrounding rock control mechanism of gob-side entry under inclined seam condition, the 130205 return air entry adjacent to 130203 gob in Yangchangwan No. 1 well is taken as a typical engineering background. By means of engineering background analysis, theoretical analysis based on inside and outside stress field, numerical simulation by FLAC3D software, and in situ industrial test and relevant monitoring methods, the optimal coal pillar width and surrounding rock control technology are obtained. The results show that the influence range of inside stress field is about 12.2∼12.8 m based on theoretical calculation result; under the influence of 10 m coal column, the overall deformation of the roadway is relatively small and within the reasonable range of engineering construction, so the width of the coal pillar along the return air roadway is set to 10 m which is more reasonable; the cross-section characteristics of special-shaped roadway lead to asymmetric stress distribution and fragmentation of surrounding rock, and then the asymmetric surrounding rock control technology under the coupling effect of roof prestressed anchor + high-strength single anchor cable + truss anchor cable support is proposed. The monitoring results of this support method are effective for the maintenance of gob-side entry, and the study conclusions provide new guidance for the surrounding rock control mechanism of gob-side entry under inclined seam conditions.

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