scholarly journals In Situ Studies on the Characteristics of Strata Structures and Behaviors in Mining of a Thick Coal Seam with Hard Roofs

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2470 ◽  
Author(s):  
Yiwen Lan ◽  
Rui Gao ◽  
Bin Yu ◽  
Xiangbin Meng
Keyword(s):  
Coal Seam ◽  
Cantilever Beam ◽  
Layer Structure ◽  
Test Method ◽  
Thick Coal Seam ◽  
Hard Roof ◽  
Working Face ◽  
High Layer ◽  
Seam Mining

The movements of overburden induced by mining a thick coal seam with a hard roof extend widely. The effects of breakages in the hard strata on the strata behaviors might vary with the overlying strata layers. For this reason, we applied a test method that integrated a borehole TV tester, borehole-based monitoring of strata movement, and monitoring of support resistance for an in situ investigation of a super-thick, 14–20 m coal seam mining in the Datong mining area in China. The results showed that the range of the overburden movement was significantly high, which could reach to more than 300 m. The key strata (KS) in the lower layer main roof were broken into a ‘cantilever beam and voussoir beam’ structure. This structure accounted for the ‘long duration and short duration’ strata behaviors in the working face. On the other hand, the hard KS in the upper layer broke into a ‘high layer structure’. The structural instability induced intensive and wide-ranging strata behaviors that lasted for a long time (two to three days). Support in the working face were over-pressured by large dynamic factors and were widely crushed, while the roadways were violently deformed. Hence, the structure of a thick coal seam with a hard roof after mining will form a ‘cantilever beam and voussoir beam and high layer structure’, which is unique to a large space stope.

scholarly journals Investigation on the Ground Pressure Induced by Hard Roof Fracturing at Different Layers during Extra Thick Coal Seam Mining

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Rui Gao ◽  
Jingxuan Yang ◽  
Tiejun Kuang ◽  
Hongjie Liu
Keyword(s):  
Coal Seam ◽  
Physical Simulation ◽  
Similarity Criterion ◽  
Thick Coal Seam ◽  
Failure Characteristics ◽  
Hard Roof ◽  
Ground Pressure ◽  
Working Face ◽  
Seam Mining ◽  
Roadway Deformation

The fracturing of hard roofs in different layers would result in complex ground pressure on the working face, such as supports collapsed and severe roadway deformation. However, the mechanism of the ground pressure induced by hard roof fracturing in different layers is still unclear. In the paper, a physical model of a 20 m extrathick coal seam mined with hard roofs existing was established based on the physical simulation similarity criterion. The overburden fracturing structure, abutment stress distribution, and failure characteristics of the coal body were monitored by a noncontact strain measurement system and resistance strain gauges, to reveal the mechanism of ground pressure induced by hard roof fracturing. Furthermore, on-site measurement was used to monitor and analyze the ground pressure affected by hard roofs in different levels. The results provide a theoretical basis for the control of ground pressure in extrathick coal seam mining with hard roofs.

Pressure Regularity Study of Three Soft Complex Coal Caving Coal Face

2011 ◽  
Vol 217-218 ◽  
pp. 1641-1646
Author(s):  
Nian Jie Ma ◽  
Guo Dong Zhao ◽  
Chun Lei Ju ◽  
Chong Li ◽  
Xiang Zhong Dong
Keyword(s):  
Coal Seam ◽  
Mine Pressure ◽  
Related Factors ◽  
Thick Coal Seam ◽  
Factors Affecting ◽  
Soft Coal ◽  
Working Face ◽  
Distribution Rule ◽  
Mining Coal ◽  
Seam Mining

In order to grasp the movement rules of three soft coal caving complex working plane strata and stoping space surrounding rock and hydraulic support interactions relationship, improve the management of mining roof, to do research about the distribution rule of caused abutment pressure and shield support of initial supporting force, the work resistance and adaptability of coal seam. The first coalface of testing mine 1301 mining coal gangue is clip three soft and thick coal seam mining, adopt fully mechanized caving technology, choose ZF6400/17/32 type support screen type top coal caving hydraulic to support working face roof support, in order to provide better services for safe production in the working face, especially study on related factors affecting the observational of working mine pressure.

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 The Mechanism and Control Technology of Strong Strata Behavior in Extra-Thick Coal Seam Mining Influenced by Overlying Coal Pillar

2019 ◽  
Vol 11 (1) ◽  
pp. 452-461
Author(s):  
Rui Gao ◽  
Tiejun Kuang ◽  
Yiwen Lan
Keyword(s):  
Coal Seam ◽  
Coal Pillar ◽  
In Situ Monitoring ◽  
Thick Coal Seam ◽  
Maximum Deformation ◽  
Working Face ◽  
Strata Behavior ◽  
Seam Mining ◽  
Roadway Deformation ◽  
And Control

Abstract This work aimed at revealing the mechanism of strong strata behavior in extra-thick coal seam mining which was influenced by an overlying coal pillar (OCP). To this end, the evolution characteristics of the stress and displacement in advance coal body of the working face were studied via numerical simulation. On this basis, the mechanism of strong strata behavior in working face affected by OCP was revealed. In situ monitoring also demonstrated that, as the working face mining near to the position of OCP, severe rib spalling and roadway deformation frequently appeared. The scheme of strengthening the hydraulic supports resistance and adding anchor cables was put forward to control the surrounding rocks in the stope. As a result, the maximum deformation of the roadway height was 0.66m and could completely meet the demands for safe mining. The study on the mechanism of strong strata behavior in working face and the strengthen supporting scheme would provide a theoretical basis for similar mining conditions, thus ensure safe and efficiency coal seam mining.

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.

scholarly journals Mining-Induced Stress-Fissure Field Evolution and the Disaster-Causing Mechanism in the High Gas Working Face of the Deep Hard Strata

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Litong Dou ◽  
Ke Yang ◽  
Wenjie Liu ◽  
Xiaolou Chi ◽  
Zhijie Wen
Keyword(s):  
Coal Seam ◽  
In Situ Monitoring ◽  
Gas Content ◽  
Hard Roof ◽  
Induced Stress ◽  
Field Evolution ◽  
Working Face ◽  
Dynamic Disaster ◽  
Seam Mining ◽  
The Impact

The compound dynamic disaster of coal and gas outbursts and rockburst is a typical hazard jeopardizing the mining of the high gas content coal seam under a hard roof condition. In this study, the hard roof’s mechanism inducing this hazard is analyzed. Physical analog modeling experiments and in situ monitoring of mining-induced stress were performed during coal seam mining under a hard roof condition. The pattern of hard roof breakage effect on the stress-fissure field evolution was revealed. The elastic energy was released and propagated on both sides immediately after the hard roof breaking, leading to energy accumulation. Meanwhile, expansive roof collapse resulted in the intense weighting of the working face and rockburst. Thus, the coal and gas outburst occurred under the joint action of the impact energy generated by breaking the hard roof and gas expansion energy. In other words, the compound dynamic disaster happened. Synergistic stereoextraction integrating cross-seam drilling and along-seam drilling was combined with deep hole advanced presplitting blasting technology to cope with the compound dynamic disaster in the high gas coal seam under a hard roof condition.

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.

scholarly journals Comprehensive technical support for safe mining in ultra-close coal seams: A case study

2021 ◽  
pp. 014459872110093
Author(s):  
Wei Zhang ◽  
Jiawei Guo ◽  
Kaidi Xie ◽  
Jinming Wang ◽  
Liang Chen ◽  
...  
Keyword(s):  
Coal Seam ◽  
Technical Support ◽  
Surrounding Rock ◽  
Coal Seams ◽  
Deformation Control ◽  
Hard Roof ◽  
Working Face ◽  
Close Coal Seams ◽  
Safe Mining

In order to mine the coal seam under super-thick hard roof, improve the utilization rate of resources and prolong the remaining service life of the mine, a case study of the Gaozhuang Coal Mine in the Zaozhuang Mining Area has been performed in this paper. Based on the specific mining geological conditions of ultra-close coal seams (#3up and #3low coal seams), their joint systematic analysis has been performed, with the focus made in the following three aspects: (i) prevention of rock burst under super-thick hard roof, (ii) deformation control of surrounding rock of roadways in the lower coal seam, and (iii) fire prevention in the goaf of working face. Given the strong bursting tendency observed in upper coal seam and lower coal seam, the technology of preventing rock burst under super-thick hard roof was proposed, which involved setting of narrow section coal pillars to protect roadways and interleaving layout of working faces. The specific supporting scheme of surrounding rock of roadways in the #3low1101 working face was determined, and the grouting reinforcement method of local fractured zones through Marithan was further proposed, to ensure the deformation control of surrounding rock of roadways in lower coal seams. The proposed fire prevention technology envisaged goaf grouting and spraying to plug leaks, which reduced the hazard of spontaneous combustion of residual coals in mined ultra-close coal seams. The technical and economic improvements with a direct economic benefit of 5.55 million yuan were achieved by the application of the proposed comprehensive technical support. The research results obtained provide a theoretical guidance and technical support of safe mining strategies of close coal seams in other mining areas.

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