scholarly journals Measurement and Analysis of Roadway Deformation and Stress under Mining-Induced Stress

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Jianfeng Cui ◽  
Weijun Wang ◽  
Qian Jia ◽  
Gang Peng ◽  
Hai Wu
Keyword(s):  
Surface Deformation ◽  
Coal Pillar ◽  
Surrounding Rock ◽  
Mining Operations ◽  
Absolute Displacement ◽  
Induced Stress ◽  
High Side ◽  
Roadway Stability ◽  
The Absolute ◽  
Coal Pillars

Small coal pillars, which are used to protect roadways, have a significant influence on mining operations and roadway stability and safety. Consequently, the optimal width of coal pillars that provides suitable performance under mining-induced stress must be determined accurately. Based on the deformation data of the surrounding rock along the gob roadway of the 13318 working face in Xieqiao Coal Mine, we analyzed the surface deformation data of the roadway and the displacement of the deep surrounding rock of the roadway under the action of mining-induced stress herein. The separation fractures of the low side of the roadway can be divided into four zones: 0–2 m, 2–5 m, 5–9 m, and 9–11 m. The absolute displacement of the surrounding rock relative to the center of the roadway in the 0–2 m zone was large, and the displacement region in the side of the roadway extended from 0 m to 11 m. The separation fractures of the high side of the roadway can be divided into three zones: 0–3 m, 3–5 m, and 5–5.5 m. The absolute displacement of the surrounding rock relative to the center of the roadway in the 0–3 m zone was large, whereas the deformation separation of the coal pillar was small. The surrounding rock in the 5–5.5 m zone also exhibited absolute displacement relative to the center of the roadway. Furthermore, the stress increased faster on the low side of the roadway than the high side; the core stress region on the high side occurred at approximately 3 m, whereas that on the low side occurred at approximately 8 m. The findings obtained herein can help determine the optimal preset width of small pillars.

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 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.

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 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 Stability Analysis of Roadway Groups under Multi-Mining Disturbances

2021 ◽  
Vol 11 (17) ◽  
pp. 7953
Author(s):  
Yuantian Sun ◽  
Ruiyang Bi ◽  
Qingliang Chang ◽  
Reza Taherdangkoo ◽  
Junfei Zhang ◽  
...  
Keyword(s):  
Coal Mining ◽  
Coal Pillar ◽  
Stability Control ◽  
Surrounding Rock ◽  
Key Strata ◽  
Working Face ◽  
Roadway Stability ◽  
Mining Disturbance ◽  
Mining Face ◽  
The Stability

The roadway stability has been regarded as the main challenging issue for safety and productivity of deep underground coal mines, particularly where roadways are affected by coal mining activities. This study investigates the −740 m main roadway in the Jining No. 2 Coal Mine to provide a theoretical basis for the stability control of the main deep roadway affected by disturbances of adjacent working activities. Field surveys, theoretical analyses, and numerical simulations are used to reveal mechanisms of the coal mining disturbance. The field survey shows that the deformation of roadway increases when the work face advances near the roadway group. Long working face mining causes the key strata to collapse based on the key strata theory and then disturbs the adjacent roadway group. When the working face is 100 m away from the stop-mining line, the roadway group is affected by the mining face, and the width roadway protection coal pillar is determined to be about 100 m. Flac3D simulations prove the accuracy of the theoretical result. Through reinforcement and support measures for the main roadway, the overall strength of the surrounding rock is enhanced, the stability of the surrounding rock of the roadway is guaranteed, and the safe production of the mine is maintained.

scholarly journals Stability Control Mechanism of High-Stress Roadway Surrounding Rock by Roof Fracturing and Rock Mass Filling

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Fuzhou Qi ◽  
Zhanguo Ma ◽  
Dangwei Yang ◽  
Ning Li ◽  
Bin Li ◽  
...  
Keyword(s):  
Rock Mass ◽  
Large Deformation ◽  
High Stress ◽  
Coal Pillar ◽  
Surrounding Rock ◽  
Vertical Stress ◽  
Mining District ◽  
Coal Bump ◽  
Novel Approach ◽  
Roadway Stability

Large deformation of roadway and coal bump failures have always been the focus in deep underground engineering. By considering the Lu’an mining district in China, the failure mode and stability improvement process of high-stress roadways were analysed with the field tests and numerical simulations. The field test results showed that a great amount of deformation and serious damage occurred in surrounding rocks during panel retreat due to the suspended roof. A novel approach employing roof fracturing and collapsed rock filling effect was adopted to maintain the roadway stability. A numerical model was established with the Universal Distinct Element Code (UDEC) to research the fracturing characteristics between the roadway and gob roofs and the stress change in the surrounding rock. The modelling results demonstrated that, without fracturing roof, the peak vertical stress of the coal pillar was 18.3 MPa and the peak vertical stress of the virgin coal rib was 15.6 MPa. The roadway was in a state of high stress. With fracturing roof, the peak vertical stress of coal pillar was 9.3 MPa and the peak vertical stress of virgin coal rib was 13.4 MPa. The fractured rock mass in the gob expanded in volume and provided supporting resistance to the overlying strata, which relieved stress concentrations in the coal pillar. Field measurement results indicated that the roadway large deformation was successfully resolved during excavation and panel retreat after implementing the novel approach, providing useful references for the application of this novel approach in similar coal mines.

scholarly journals Investigation on Hydraulic Fracturing and Cutting Roof Pressure Relief Technology for Underground Mines: A Case Study

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Qingliang Chang ◽  
Xingjie Yao ◽  
Xiangyu Wang ◽  
Sen Yang ◽  
Yuantian Sun
Keyword(s):  
Hydraulic Fracturing ◽  
Stable State ◽  
Coal Pillar ◽  
Industrial Test ◽  
Surrounding Rock ◽  
Underground Mines ◽  
Mine Pressure ◽  
Damage Degree ◽  
Working Face ◽  
Coal Pillars

Abstract Using hydraulic fracturing for cutting roof pressure is a critical technology to protect coal pillars. In this paper, based on the engineering background of 18506 working face in the Xiqu Coal Mine, using the methods of theoretical analysis, numerical simulation, and field measurement, a reasonable coal pillar width and practical parameters of hydraulic fracturing are given. The results show that roof cutting can significantly increase the stress in goaf and relieve the advanced pressure of the working face. Taking 18506 working face as the research object, the industrial test is carried out, and the surrounding rock control scheme of hydraulic fracturing and roof cutting is put forward, the mine pressure monitoring results show that the auxiliary roadway of 18506 working face reaches a stable state within 20 days, the deformation and damage degree of roadway surrounding rock are small, and the integrity of surrounding rock is improved.

scholarly journals Stability Analysis of Surrounding Rock in Paste Backfill Recovery of Residual Room Pillars

2019 ◽  
Vol 11 (2) ◽  
pp. 478 ◽  
Author(s):  
Nan Zhou ◽  
Hao Yan ◽  
Shuyin Jiang ◽  
Qiang Sun ◽  
Shenyang Ouyang
Keyword(s):  
Surface Deformation ◽  
Surrounding Rock ◽  
Induced Earthquakes ◽  
Mining Areas ◽  
Rock Stability ◽  
Study Results ◽  
Deformation Properties ◽  
Paste Backfill ◽  
Northern Shaanxi ◽  
Coal Pillars

A method of paste backfill recovery for residual room coal pillars is hereby proposed. The principles and processes of this method are systemically explained to address issues such as mining-induced earthquakes from spontaneous destabilization, surface subsidence, and low recovery rates. These are caused by the instability of residual coal pillars due to their spontaneous combustion in room-and-pillar mining in medium-to-small coalmines in the northern Shaanxi area. This method is based on the local abundance of surface aeolian sand and solid wastes to be used as paste-backfilling materials in coalmines in the northern Shaanxi area. Uniaxial compressive strength, bleeding rate, and slump tests were performed on paste-backfilled samples constituted at different ratios based on the types of materials involved in paste backfilling in the northern Shaanxi region, thereby helping to confirm the optimal ratios for paste-backfilling materials for the Ershike coal mine. A simulation was conducted to investigate the failure, goaf vertical stress distribution, and surface deformation properties of paste-backfilled pillars and coal pillars, where paste backfilling was used with paste-backfilling materials constituted at different compressive strengths. This was to verify the experimental results that would be obtained with paste-backfilling materials constituted at different ratios, and reveal the mechanism by which paste backfilling of residual room pillars can maintain the mine’s surrounding rock stability. These study results are of great instructive significance to the safe recovery of residual room pillars in China’s western mining areas.

scholarly journals The Influence of the Backfilling Roadway Driving Sequence on the Rockburst Risk of a Coal Pillar Based on an Energy Density Criterion

2018 ◽  
Vol 10 (8) ◽  
pp. 2609 ◽  
Author(s):  
Yi Xue ◽  
Zhengzheng Cao ◽  
Feng Du ◽  
Lin Zhu
Keyword(s):  
Energy Density ◽  
Dynamic Instability ◽  
Coal Pillar ◽  
Optimal Choice ◽  
Mining Technology ◽  
Pillar Stability ◽  
Rockburst Hazard ◽  
Density Factor ◽  
Coal Pillars ◽  
Energy Density Factor

The rockburst hazard has always been an important issue affecting the safety production of coal mines in China. The unreasonable sequencing of roadway driving can lead to the dynamic instability of coal pillars, which subsequently causes rockburst accidents in roadway backfilling mining engineering and poses a serious threat to the safety of the mines. Roadway backfilling mining technology is an effective approach with which to mine corner residual coal resources under buildings, railways, and rivers. An energy density criterion is established and programmed with FISH language using numerical analysis software for the rockburst risk evaluation of coal pillars. On this basis, a numerical simulation model is established based on four scheme types, namely, the sequential mining, one-roadway interval mining, two-roadway interval mining, and three-roadway interval mining schemes. The influence of the backfilling roadway driving sequence on coal pillar stability is investigated, and the change law of vertical stress and energy density factor of coal pillars in different driving sequences in roadway backfilling mining technology are analyzed. According to the research results, the maximum energy density factor value of 21,172 J/m4 for coal pillars in one-roadway interval mining is the lowest among the different schemes. Therefore, the one-roadway interval mining scheme is the optimal choice in roadway backfilling mining technology. The results can be treated as an important basis for the prevention and treatment of coal pillar instability and rockburst in roadway backfilling mining technology.

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