Roadway layout for recycling residual coal pillar in room-and-pillar mining of thick coal seam

During the mining of the shallow-buried and close-distance multiple coal seam, the rheological failure of the surrounding weakly cemented soft rock of the roadway in the lower coal seam under the concentrated stress is very rare. However, the stress on the roof of the upper coal seam is transmitted down through the residual pillar, resulting in this situation. Taking the Gaojialiang coal mine which is located in the mining areas of western China as the research object, the failure mechanism of the roadway roof under the residual coal pillar in the shallow-buried and close-distance multiple seam is studied in combination with field monitoring and numerical simulation. Furthermore, suggestions on the roadway support under such geological conditions are proposed. The results show that the residual coal pillar in the working face of the lower coal seam gradually collapses during the mining of the shallow-buried and close-distance multiple coal seam. The concentrated stress transferred by the coal pillar increases further, which makes the roof stress of the lower coal seam roadway to increase continuously. In addition, the stress of the roadway roof also increases further due to the rotation of the broken rock above the goaf, and the peek region of stress moves to the nongoaf area. Combining the heavy concentrated stress and weakly cemented property, the shallow-buried surrounding rock shows rheological behavior and failure. Therefore, we must pay more attention on the creep failure of the roadway roof under the action of the residual coal pillar even in the shallow-buried coal seam.

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Research on Reasonable Position of Roadway for close Multi-Seam and its Application

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.807-809.2393 ◽

2013 ◽

Vol 807-809 ◽

pp. 2393-2397

Author(s):

Ai Qing Liu

Keyword(s):

Stress Concentration ◽

Coal Seam ◽

Abutment Pressure ◽

Dynamic Pressure ◽

Coal Pillar ◽

Stress Zone ◽

Concentration Degree ◽

Residual Coal

The principle of roadway layout is in the low stress zone. Roadway will be difficult to support due to the lower seam face in the close multi-seam is affected by dynamic pressure of the upper seam face mining. The distribution of abutment pressure after the upper seam face mining were analyzed,concluded that: The layout of lower seam roadway should avoid the stress concentration area of residual coal pillar; Stress concentration of the coal pillar is related with mining order, and stress concentration degree is higher in the first mining side of the coal pillar; when the upper coal seam is gob, the layout of the roadway in the lower coal seam with the pattern of homodromous alternate interior layout will be easy to support.

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Study on Intelligent Identification Method of Coal Pillar Stability in Fully Mechanized Caving Face of Thick Coal Seam

Energies ◽

10.3390/en13020305 ◽

2020 ◽

Vol 13 (2) ◽

pp. 305 ◽

Cited By ~ 3

Author(s):

Jingjing Dai ◽

Pengfei Shan ◽

Qi Zhou

Keyword(s):

Coal Seam ◽

Simulation Experiment ◽

Coal Pillar ◽

Shanxi Province ◽

Parameter Determination ◽

Pillar Stability ◽

Thick Coal Seam ◽

Identification Method ◽

Optimal Value ◽

The Relationship

The combination of coal precise mining and information technology in the new century is one of the important directions for the future development of coal mining. Taking the fully mechanized top coal caving condition of a thick coal seam in the 90,101 working face of Baoshan Yujing Coal Mine in Shanyin City, Shanxi Province as an example, the intelligent identification method of section coal pillar stability was studied. The load transfer law of overlying strata in the upper part of coal pillar was analyzed, and the coal pillar values of each index were obtained by using an empirical formula, mean impact value-genetic algorithm-BP neural network (MIV-GA-BP) simulation experiment, and finite difference algorithm. The Delphi index evaluation system was used to calculate the optimal value of the coal pillar. The results showed that the non-contact cantilevered triangle on the two wings of the coal pillar in the goaf reduced the stress on the coal pillar; according to the width of the coal pillar at 10 m, 14 m, 16 m, and 20 m, combined with the relationship between the plastic zone and the core zone of coal pillar, and the relationship between the stress field and the ultimate strength of coal pillar, the numerical simulation value of the coal pillar was determined. The MIV (mean impact value) characteristics screened out the influencing factors of coal pillar width in the section near the horizontal fully mechanized top coal caving face order of importance; the relative error between the predicted value and the expected value of the MIV-GA-BP simulation experiment was less than 5%, which has good stability for the multi-factor nonlinear coupling prediction problem; and the optimal value of the coal pillar was 16.03 m by the intelligent identification method of the coal pillar. When the 16 m pillar was used, the surrounding rock deformation of the roadway was small, and the control effect was good. The research results provide a theoretical basis and reference for the parameter determination of similar projects.

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Numerical Investigation on the Ground Response of a Gob-Side Entry in an Extra-Thick Coal Seam

Shock and Vibration ◽

10.1155/2021/8838505 ◽

2021 ◽

Vol 2021 ◽

pp. 1-7

Author(s):

C.W. Zang ◽

G.C. Zhang ◽

G.Z. Tao ◽

H.M. Zhu ◽

Y. Li ◽

...

Keyword(s):

Rock Mass ◽

Coal Seam ◽

Numerical Investigation ◽

Large Scale ◽

Shear Failure ◽

Coal Pillar ◽

Coal Mass ◽

Thick Coal Seam ◽

Anchor Cable ◽

Study Results

This study was aimed at the large deformation phenomenon of rock mass surrounding the gob-side entry driven in a 20 m extra-thick coal seam. Taking tailgate 8211 as the engineering background, a numerical investigation was employed to analyze the deformation law of the gob-side entry. The study results are as follows. (1) Because the immediate roof was composed of weak coal mass with a thickness of 17 m, the roof coal mass was vulnerable to fail with the effect of overlying strata pressure; thus, a visual subsidence of roof coal mass with a maximum convergence of 800 mm was observed in the field. (2) The bearing capacity of the coal pillar was significantly less than that of the panel rib, resulting in the pillar failing more easily under the ground pressure and then generating large-scale squeezing deformation. (3) The roof and panel rib were in a state of shear failure with a failure depth of about 5 m. The coal pillar was entirely in a state of plastic failure. (4) A support scheme including an asymmetric anchor beam truss, roof angle anchor cable, and anchor cable combination structure was proposed. The field work confirmed that this support scheme could efficiently control the deformation and failure of the rock mass surrounding the gob-side entry. This study provides the theoretical basis and technical support for the control of rocks surrounding the gob-side entry in similar conditions.

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Study on Pressure Relief Technology of High-Pressure Water Jet of Residual Coal Pillar in Overlying Goaf in Close Seam Mining

Shock and Vibration ◽

10.1155/2022/7842921 ◽

2022 ◽

Vol 2022 ◽

pp. 1-19

Author(s):

Shang Yang ◽

Xuehui Li ◽

Jun Wang ◽

Shuhao Yang ◽

Zhen Shen ◽

...

Keyword(s):

High Pressure ◽

Coal Seam ◽

Coal Pillar ◽

Water Jet ◽

Hydraulic Support ◽

Working Face ◽

Pressure Water ◽

High Pressure Water Jet ◽

Residual Coal ◽

Close Distance

To solve the problem of strong ground pressure behaviour under a residual coal pillar in the overlying goaf of a close-distance coal seam, this paper proposes the technology of weakening and relieving the residual coal pillar in the overlying goaf by a high-pressure water jet. Based on the geological occurrence of the No. 3 coal seam and mountain No. 4 coal seam in the Yanzishan coal mine, the high-pressure water jet pressure relief technology of residual coal pillars in the overlying goaf of close-distance coal seams was studied by theoretical analysis and field industrial tests. First, the elastic-plastic zone of the residual coal pillar and the stress distribution law of the floor are obtained by theoretical analysis, and the influence degree of the residual coal pillar on the support of the lower coal seam working face is revealed. Then, a high-pressure water jet combined with mine pressure is proposed to weaken the residual coal pillar. Finally, through the residual coal pillar hydraulic cutting mechanical model and “double-drilling double-slot” model, the high-pressure water jet drilling layout parameters are determined, and an industrial field test is carried out. The single knife cutting coal output and 38216 working face hydraulic support monitoring data show that high-pressure hydraulic slotting can weaken the strength of the coal body to a certain extent, destroy the integrity of the residual coal pillar, cut off the load transmission path of the overlying strata, and reduce the working resistance of the hydraulic support under the residual coal pillar to a certain extent, which is beneficial to the safe mining of the working face.

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

Open Geosciences ◽

10.1515/geo-2019-0036 ◽

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.

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A Method for Determining Feasibility of Mining Residual Coal above Out-Fashioned Goaf under Variable Load: A Case Study

Advances in Civil Engineering ◽

10.1155/2020/8837657 ◽

2020 ◽

Vol 2020 ◽

pp. 1-12

Author(s):

Yuxia Guo ◽

Honghui Yuan ◽

Xiaogang Deng ◽

Yujiang Zhang ◽

Yunlou Du ◽

...

Keyword(s):

Coal Seam ◽

Coal Mine ◽

Coal Pillar ◽

New Method ◽

System Model ◽

Variable Load ◽

Residual Coal ◽

Seam Mining ◽

Suspended Roof ◽

Upward Mining

Out-fashioned goaf is the protective structure for mining the upper residual coal, and its stability is the core problem in mining the upper residual coal. According to the upward mining demand for No. 5 coal seam above the out-fashioned goaf in Baizi Coal Mine, a new method is proposed to determine the upward mining safety. According to the analysis of the actual situation of the mine, the coal pillar and suspended roof in the out-fashioned goaf are taken as the objects. Furthermore, a “coal pillar-suspended roof” system model based on the variable load induced by abutment pressure of upper coal seam mining is established. After the mechanical model was solved, the parameter acquisition method of the model was established. The basic parameters of Baizi Coal Mine were considered to determine the feasibility of mining residual coal above out-fashioned goaf. And the effects of variable load on the coal pillar and suspended roof stability were analyzed. The results show that the upper No. 5 coal seam in Baizi Coal Mine can be mined safely. Compared to the traditional method, which simplifies all the upper loads to uniform loads, the new method is safer. The system stability of the suspended roof and coal pillar is influenced by “a/L” and “L.” Axial stress curves of the coal pillar and suspended roof appear nearly parabolic with “a/L” varying. Their maximum values are obtained when the “a/L” value is around 0.5∼0.6. In this situation, the combination structure is most easy to to be damaged. The ratio q′/q has a linear relationship with all stresses of the system model. The failure sequence of the system model is determined by analyzing the relationship between the tensile strength of the suspended roof and compressive strength of the coal pillar. This study provides a reference case for coal resources upward mining under similar conditions.

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Physical Experiment and Numerical Modeling on the Failure Mechanism of Gob-Side Entry Driven in Thick Coal Seam

Energies ◽

10.3390/en13205425 ◽

2020 ◽

Vol 13 (20) ◽

pp. 5425 ◽

Cited By ~ 1

Author(s):

Xinshuai Shi ◽

Hongwen Jing ◽

Zhenlong Zhao ◽

Yuan Gao ◽

Yuanchao Zhang ◽

...

Keyword(s):

Coal Seam ◽

Failure Mechanism ◽

Coal Pillar ◽

Stability Control ◽

Shear Cracks ◽

Thick Coal Seam ◽

Physical Model Tests ◽

The Stability ◽

Roof Strata ◽

Overlying Strata

In this paper, a combination of physical model tests and numerical simulations were carried out to explore the overlying strata movement laws, failure mechanism, and cracks evolution of the gob-side entry driven in a thick coal seam. The physical experimental results indicated that the hanging cantilever beam was easily developed above the coal pillar after mining out the 2101 panel, resulting in a larger and stronger stress concentration. The overburden loads acting on the coal pillar can be greatly released after the hanging roof strata were cut down with an 18 m cutting line. Additionally, we adopted Universal Discrete Element Code (UDEC) software to investigate the deformation and crack evolution mechanism of the gob-side entry under different conditions. The primary-supported roadway underwent severe deformation, filling with a great quantity of tensile and shear cracks to the inner coal pillar. Both the physical and numerical results proved that the optimized-support parameters combined with roof-cutting measures could effectively guarantee the stability of the gob-side entry. This research can provide valuable guidance for the stability control of the gob-side entry in mines under similar conditions.

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