scholarly journals Stability Analysis of the Entry in a New Mining Approach Influenced by Roof Fracture Position

2019 ◽  
Vol 11 (22) ◽  
pp. 6349
Author(s):  
Jun Yang ◽  
Hongyu Wang ◽  
Yajun Wang ◽  
Binhui Liu ◽  
Shilin Hou ◽  
...  
Keyword(s):  
Coal Pillar ◽  
Main Roof ◽  
Surrounding Rock ◽  
Fracture Position ◽  
Solid Coal ◽  
Rock Structure ◽  
Temporary Support ◽  
Coal Wall ◽  
Pillar Mining ◽  
The Stability

Non-coal pillar mining with roadway formed automatically (RFANM) is a new mining approach, which demonstrates revolutionary significance because it does not require making roadway before mining and coal pillar retaining. In order to explore the stability of the surrounding rock structure in RFANM, the deformation of the surrounding rock was theoretically analyzed and simulated based on three different fracture positions of the main roof. It was concluded that reasonable control of temporary support strength in roadway is of great importance to control the deformation of the entry. The deformation process of surrounding rock under different fracture positions in RFANM was simulated by using the Universal Discrete Element Code (UDEC). The results of the numerical simulation showed that the main roof was fractured at the solid coal side or gob side; the deformation of the roadway was small. The fracture condition of the main roof at the gob side required a higher effect of roof slitting or temporary support from the roadway. Through drilling and peeping at the retained roadway, it was judged that the main roof was broken inside the coal wall. Field monitoring results revealed that the deformation of the roadway can be effectively controlled.

scholarly journals Stability of Split-Level Gob-Side Entry in Ultra-Thick Coal Seams: A Case Study at Xiegou Mine

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 628 ◽  
Author(s):  
Junwen Zhang
Keyword(s):  
Coal Mine ◽  
Coal Pillar ◽  
Peak Stress ◽  
Coal Seams ◽  
Solid Coal ◽  
Stress Fluctuation ◽  
Pillar Mining ◽  
The Stability ◽  
Rock Specimens

Split-level longwall gob-side entry (SLGE) has been applied as a special form of small gate pillar mining (or non-coal pillar mining) in thick coal seams. The stability of the coal pillar directly affects the rationality of the layout of the SLGE. Starting from the mining-induced influence around the SLGE, this paper compares the mechanical properties of coal under different mining effects, and studies the rationality of “zero pillar” location against the Xiegou coal mine. The study shows that the key to success of the application of the SLGE is the existence of an intact zone within the triangular coal pillar in spite of double disturbances due to tunneling and coal mining extraction. Laboratory testing shows that the density and uniaxial compressive strength of rock specimens obtained from the triangular coal pillar are smaller than that from the other part of the panel which is concluded to be due to the varied degree of mining-induced influence. The numerical modeling results show that most of the triangular coal pillar is intact after extraction of the panel, and that the peak stress is located in the solid coal beyond the triangular coal pillar. The plastic zone of the triangular coal pillar is only about 1 m after the excavation of the tail gate of the next split-level panel. The physical modeling shows that the tail gate of the next panel is in the destressed zone with only a very small stress fluctuation during the extraction of the next panel. The study shows that the location of the SLGE at Xiegou coal mine is reasonable. SLGE is preferable for ultra-thick coal seams.

scholarly journals Research on the Transmission of Stresses by Roof Cutting near Gob Rocks

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1237
Author(s):  
Zhibiao Guo ◽  
Haohao Wang ◽  
Zimin Ma ◽  
Pengfei Wang ◽  
Xiaohui Kuai ◽  
...  
Keyword(s):  
Early Stage ◽  
Pressure Coefficient ◽  
Influence Factors ◽  
Stress Transfer ◽  
Main Roof ◽  
Surrounding Rock ◽  
Pressure Relief ◽  
Rock Structure ◽  
Immediate Roof ◽  
The Stability

Pressure relief for roadways retained by roof cutting is essentially caused by stress transfer. In this paper, the stress transfer mechanism of 16011 tail entry with roof cutting in Zhaogu No.1 coal mine is studied from the following two aspects: the change of the tail entry surrounding the rock structure and the interaction between the roadway surrounding rock and supporting structures. It is found by numerical simulation that roof cutting can significantly reduce the magnitude of roadway roof stress, transferring the concentrated stress induced by excavation and mining away from the roadway, and forming an obvious triangle pressure relief area in front of the working face. In the early stage after mining, most of the overburden load is transferred downward through the immediate roof of the roadway. With the movement of overlying strata, the stress, initially transferred to the immediate roof strata, is gradually transferred to the gob, and the calculation formula and influence factors of the transferred stress are derived. In addition, through the establishment of the mechanical model and theoretical calculation of the key rock block of the main roof, the roadside support resistance required to ensure the stability of the main roof block is determined. The field monitoring shows that the lateral pressure coefficient of the roadside caved rocks is 0.36 and the constant resistance and large deformation anchor cable (CRLDAC) and the roadway temporary support play roles of conduction and control in the process of stress transfer, and effectively ensure the stability of surrounding rock during the service life of the retained gob-side entry by roof cutting (RGERC).

scholarly journals Surrounding Rock Movement of Steeply Dipping Coal Seam Using Backfill Mining

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Wenyu Lv ◽  
Kai Guo ◽  
Jianhao Yu ◽  
Xufeng Du ◽  
Kun Feng
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Surrounding Rock ◽  
Maximum Deflection ◽  
Coal Seams ◽  
Physical Similarity ◽  
Working Face ◽  
Rock Structure ◽  
Backfill Mining ◽  
The Stability

The movement of the overlying strata in steeply dipping coal seams is complex, and the deformation of roof rock beam is obvious. In general, the backfill mining method can improve the stability of the surrounding rock effectively. In this study, the 645 working face of the tested mine is used as a prototype to establish the mechanical model of the inclined roof beam using the sloping flexible shield support backfilling method in a steeply dipping coal seam, and the deflection equation is derived to obtain the roof damage structure and the maximum deflection position of the roof beam. Finally, numerical simulation and physical similarity simulation experiments are carried out to study the stability of the surrounding rock structure under backfilling mining in steeply dipping coal seams. The results show the following: (1) With the support of the gangue filling body, the inclined roof beam has smaller roof subsidence, and the maximum deflection position moves to the upper part of working face. (2) With the increase of the stope height, the stress and displacement field of the surrounding rock using the backfilling method show an asymmetrical distribution, the movement, deformation, and failure increase slowly, and the increase of the strain is relatively stable. Compared with the caving method, the range and degree of the surrounding rock disturbed by the mining stress are lower. The results of numerical simulation and physical similarity simulation experiment are generally consistent with the theoretically derived results. Overall, this study can provide theoretical basis for the safe and efficient production of steeply dipping coal seams.

scholarly journals Stability Analysis of Surrounding Rock of Large Section Ultradeep Shaft Wall

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Cheng Li ◽  
Wang Chunlong ◽  
Wang Xi ◽  
Chen Kexu
Keyword(s):  
Control Method ◽  
Stress Test ◽  
Stability Control ◽  
Surrounding Rock ◽  
Main Shaft ◽  
Large Section ◽  
Masonry Construction ◽  
Temporary Support ◽  
The Stability ◽  
Shaft Wall

In order to study the stability of deep surrounding rock during the excavation of new main shaft in Xincheng gold mine, a construction method suitable for large section ultradeep shaft is proposed. A series of analyses were carried out in this study, including the in situ stress test, stress response of surrounding rock disturbance, deformation and failure characteristics, and numerical simulation. Based on the above analysis, the stability control method of surrounding rock in the process of deep excavation of the new main shaft is proposed. The results show that (1) the maximum principal stress of deep surrounding rock of new main shaft is horizontal stress, and the surrounding rock of the shaft has strong rock burst tendency after excavation; (2) the influence range of the deep shaft excavation disturbance is 6.4 times the shaft radius, in which the temporary support should be strengthened to avoid the influence of excavation disturbance on the stability of shaft wall rock; (3) the failure shape of surrounding rock of the deep shaft excavation was “ear” failure, and the failure depth was not more than 2.5 m; (4) after replacing the original “one-excavation and one-masonry” construction with “three-excavation and one-masonry” construction, the temporary support span of the main shaft was adjusted to 12 m, which can make the subsequent concrete shaft wall in the state of “no pressure bearing or slow low pressure bearing,” and the lining compressive safety coefficient was increased to 1.98, which meets the safety requirements.

scholarly journals Study on Overburden Stability and Development Height of Water Flowing Fractured Zone in Roadway Mining with Cemented Backfill

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Yu Dong ◽  
Yucheng Huang ◽  
Jifang Du ◽  
Fei Zhao
Keyword(s):  
Empirical Formula ◽  
Mechanical Model ◽  
Fractured Rock ◽  
Coal Pillar ◽  
Main Roof ◽  
Mechanical Analysis ◽  
Overburden Rock ◽  
Fractured Zone ◽  
The Stability ◽  
Rock Beam

In order to explore the stability of overburden rock and the development height of water flowing fractured zone in roadway filling mining, based on the movement and deformation mechanism of overburden rock, the mechanical analysis of overburden stability and failure was carried out, and the mechanical model of main roof rock beam was established, and the ultimate span and limit deflection of rock beam fracture were deduced. Combined with the mechanical model of the main roof fractured rock, the basis for the judgment of overburden failure developing to fractured zone is given in this paper. Taking a coal mine roadway backfill under water-bearing stratum as an example, based on the equivalent mining height, the theoretical calculation and analysis are carried out on the stability of overburden rock and the height of water flowing fractured zone. The reliability of the theoretical analysis is verified compared with the empirical formula and the numerical simulation results. The results showed that the water flowing fractured zone developed to the bottom of no. 7 glutenite, with a height of 32.5 m, slightly less than the calculation result of the empirical formula. The thickness of the waterproof coal pillar was 39.8 m, which was much less than the distance from the aquifer to the coal seam and can be mined safely.

scholarly journals Control of Gob-Side Roadway with Large Mining Height in Inclined Thick Coal Seam: A Case Study

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Xie Fuxing
Keyword(s):  
Numerical Simulation ◽  
Coal Pillar ◽  
Simulation Software ◽  
Surrounding Rock ◽  
Mine Pressure ◽  
Thick Coal Seam ◽  
Working Face ◽  
Rock Structure ◽  
Large Mining Height ◽  
Mining Height

The gob-side roadway of 130205, a large-mining-height working face in the Yangchangwan coal mine, was investigated in terms of the mine pressure law and support technology for large mining heights and narrow coal pillars for mining roadways. The research included field investigations, theoretical analysis, numerical simulation, field tests, and other methods. This paper analyzes the form of movement for overlying rock structure in a gob-side entry with a large mining height and summarizes the stress state and deformation failure characteristics of the surrounding rock. The failure mechanism of the surrounding rock of the gob-side roadway and controllable engineering factors causing deformation were analyzed. FLAC3D numerical simulation software was used to explore the influence law of coal pillar width, working face mining height, and mining intensity on the stability of the surrounding rock of the gob-side roadway. Ensuring the integrity of the coal pillar, improving the coordination of the system, and using asymmetric support structures as the core support concept are proposed. A reasonably designed support scheme for the gob-side roadway of the working face for 130205 was conducted, and a desirable engineering effect was obtained through field practice verification.

Research on Supporting Technology of Roadway Driving along Next Goaf of Second Mining Strip Pillar

2012 ◽  
Vol 446-449 ◽  
pp. 1657-1660
Author(s):  
Wei Dong Lv ◽  
Nan Nan Zhao
Keyword(s):  
Abutment Pressure ◽  
High Strength ◽  
Main Roof ◽  
Surrounding Rock ◽  
Control Effect ◽  
General Stability ◽  
High Strength Bolt ◽  
Mining Face ◽  
The Stability ◽  
Surrounding Rock Deformation

For roadway driving along next goaf of strip pillar second mining, being influenced by the abutment pressure of previous coal mining face and main roof breaking rotary deformation, the surrounding rock deformation is serious and the control effect of ordinary bolt supporting on the general stability of roadway driving along next goaf is poorer. According to the concrete geological and technique condition of the 2351 second mining strip pillar in Daizhuang Colliery, adopting the united support pattern combined high strength bolt of levorotatory continuous thread and anchor of low relaxation prestress, the safety of the roadway can be ensured and the stability of the roadway surrounding rocks can be improved. It is of significant reference meaning for bolting support of roadway driving along next goaf of second mining strip pillar under similar condition.

The Stability Control Technology of Crosscut while Mining without Coal Pillar in Steep Seam

2011 ◽  
Vol 90-93 ◽  
pp. 2073-2079
Author(s):  
Yu Feng Wang ◽  
Zhi Qiang Liu ◽  
Bin Song Jiang
Keyword(s):  
Support System ◽  
Coal Pillar ◽  
Stability Control ◽  
Surrounding Rock ◽  
Steep Seam ◽  
Floor Rock ◽  
Long Term Stability ◽  
Rock Collapse ◽  
The Stability

In order to improve the mining benefit of coal resources, Chang Gouyu Coal Mine carried out the technology of mining without coal pillar in steep seam. The key of the technology was to ensure a long-term stability of the cross-entry roadway across the seam. Through the analysis of the nature of steep seam roof and floor rock, and based on the stability analysis and loose circle measured of surrounding rock of crosscut roadway, we brought forward adopting shotcrete rockbolt mesh and U-shaped steel complex support structure system. This complex support system could flex lengthways and compress in radial direction. The entirety integrated with the surrounding rock, and they formed into a whole. Application of the complex support system could effectively control the deformation of the surrounding rock collapse, and maintain the stability of the crosscut.

scholarly journals The segmental subsidence structure with immediate roof of gob side entry retaining in backfill mining

2021 ◽  
pp. 014459872199654
Author(s):  
Xin-yuan Zhao ◽  
Xin-wang Li ◽  
Ke Yang ◽  
Zhen Wei ◽  
Qiang Fu
Keyword(s):  
Mechanical Model ◽  
Surrounding Rock ◽  
Extreme Conditions ◽  
Structure Characteristics ◽  
Rock Structure ◽  
Immediate Roof ◽  
Backfill Mining ◽  
The Difference ◽  
The Stability ◽  
Supporting Force

When gob side entry retaining is carried out in backfill mining, the roof will show different subsidence morphology due to the difference of compactness and supporting force of the backfill body at different positions. This paper analyzed the immediate roof subsidence structure under two extreme conditions, constructed the roof segmented subsidence structure and the mechanical model of roadside backfill body, and used FLAC3D software to investigate the roof migration and the force law of the roadside backfill body under the conditions of different goaf backfilled rates, different width and strength of roadside backfill body. Finally, the backfill practice of a mine in Shandong Province of China is taken as an example for analysis. The results show that the segmented subsidence structure of the immediate roof is related to the mechanical properties of the roadside backfill body and the goaf backfill body. When the backfilled rate of goaf decreases from 95% to 70%, the width of roadside backfill body decreases from 5 m to 1 m, and the elastic modulus decreases from 10 GPa to 0.5 GPa, the greater difference in the subsidence and inclination of the immediate roof on both sides of the roadside backfill body is, the more obvious the segmented subsidence structure characteristics of the immediate roof are, and the greater force on the roadside backfill body will be, the more unfavorable it is to maintain the stability of the roadway surrounding rock and the roadway backfill body. Therefore, when gob side entry retaining is carried out in backfill mining, the surrounding rock structure and the force on roadside backfill body should be considered comprehensively.

scholarly journals Accident Analysis in Relation to Main Roof Structure When Longwall Face Advances toward a Roadway: A Case Study

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Chang Liu ◽  
Zengqiang Yang ◽  
Peilin Gong ◽  
Kai Wang ◽  
Xiaoqiang Zhang ◽  
...  
Keyword(s):  
Sharp Increase ◽  
Coal Pillar ◽  
Main Roof ◽  
Mechanical Analysis ◽  
Longwall Face ◽  
Good Effect ◽  
Key Factors ◽  
Roof Structure ◽  
Similar Simulation Experiment ◽  
The Stability

Practices show that hydraulic supports crushing accidents or roadway supports failure often take place when a longwall face advances toward an abandoned roadway or a predriven equipment recovery room. Therefore, a 2D similar simulation experiment is conducted to reveal the loading mechanism. The result shows that when the workface advances close to roadways, the main roof breaks ahead of the workface and leads to instability of higher strata. These two changes induce a sharp increase of the load on supports and lead to an accident. Thus, more attention should be paid to the advanced fracture. Therefore, mechanical analysis is used to explain the advanced fracture. Results show that the failure of coal pillar being excavated induces a sharp increase in the main roof’s hanging length. Once the hanging length reaches the limit, the advanced fracture takes place. Therefore, the stability of the coal pillar and the hanging length of roof strata are two key factors that may induce an accident. To prevent the a similar supports crushing accident, the partial backfilled technology which partly backfills the abandoned roadway in height and length to maintain the stability of the coal pillar is put forward and put into practice. The field test shows a good effect.

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