Stress redistribution of longwall mining stope and gas control of multi-layer coal seams

Yang, Wei; Lin, Baiquan; Yan, Qing Rong; Zhai, Cheng

doi:10.1016/j.ijrmms.2014.08.009

Cited by 53 publications

(26 citation statements)

References 30 publications

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“…The gas from the goaf cannot be taken away by the fresh air in the roadway due to the fact that an eddy always forms in the upper corner when air flows through the right angle there. As a consequence, gas overruns in the upper corner of the coal face [1,2]. Additionally, a large-sized coal pillar between two U-type longwall panels is needed to support the overburden and protect the gateroad space [3], as shown in Figure 2c, which causes serious coal resources waste and potential risk of rock burst [4,5].…”

Section: Geological and Engineering Conditionsmentioning

confidence: 99%

Numerical Study on the Effectiveness of Grouting Reinforcement on the Large Heaving Floor of the Deep Retained Goaf-Side Gateroad: A Case Study in China

Zhang

Shimada

2018

Energies

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Abstract:To study the effectiveness of grouting reinforcement on a large heaving floor of the retained goaf-side gateroad (RGSG) at a 900 m depth in the Zhuji coal mine, a numerical model involving strain softening constitutive material was built. First, the simulated deformations of the RGSG were compared with field data to verify the reliability of the numerical model. Then, the dynamic distribution of the stress in the RGSG floor was examined to reveal the mechanism of floor heave. Finally, grouting reinforcement was proposed to control the RGSG floor, and the corresponding effectiveness was verified by improving the rock mechanics of the floor strata based on the results of numerical uniaxial compressive tests. The results demonstrated that a fairly good match was achieved between the field and numerical data, and the proposed FLAC3D (Fast Lagrangian Analysis of Continua) numerical model was an effective approach to study the stability of the deep RGSG. A variation of the ratio between horizontal stress to vertical stress in the floor strata was the root cause of floor heave in the deep RGSG. Ideally, the floor heave could be reduced by 41%, 62%, and 79% when the floor strata of 1 m depth were reinforced with grouting schemes I, II, and III, respectively.

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Section: Geological and Engineering Conditionsmentioning

confidence: 99%

Numerical Study on the Effectiveness of Grouting Reinforcement on the Large Heaving Floor of the Deep Retained Goaf-Side Gateroad: A Case Study in China

Zhang

Shimada

2018

Energies

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“…The maximum failure depth of the floor, which is caused by stress concentration under ultimate bearing pressure conditions of the floor rock, can be obtained by using (16). The ultimate bearing capacity of strata was calculated using Mohr-Coulomb failure criterion [30].…”

Section: Geofluidsmentioning

confidence: 99%

“…The width of the plastic area was calculated by using (16). Equation (17) was used for determining the maximum failure depth of the floor.…”

Section: Geofluidsmentioning

confidence: 99%

“…Presently, more attention is paid to pressure relief effect of the protected seam, but factors causing methane concentration to exceed the limit are ignored during PCSM [13,14]. A qualitative method is mainly used to estimate pressure relief gas seepage, which is not applicable for gas drainage and control [15][16][17]. Besides, there are few studies on the main influencing factors of pressure relief gas seepage.…”

Section: Introductionmentioning

confidence: 99%

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A Gas Seepage Modeling Study for Mitigating Gas Accumulation Risk in Upper Protective Coal Seam Mining Process

Zhang

et al. 2018

Geofluids

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Protective coal seam mining (PCSM) is one of the most significant mitigation measures of regional outburst in the process of deep coal seam mining, which has high outburst risk in China. During the PCSM process, the phenomenon of methane concentration exceeding the limit usually occurs in the working face. It is vital to understand factors affecting gas emission from the protective seam working face (PSWF) and to obtain an equation for determining the quantity of gas emission. A gas seepage model (GSM) was developed to simulate the gas emission during the process of upper PCSM. In this study, an equation was formulated to determine the quantity of gas desorbed from the protected seam into PSWF. These equations have been developed by using Fick’s second law of diffusion and Darcy’s flow law. The relationship between permeability and stress was described in an elastic-plastic state, and the mechanics of surrounding rock were investigated. It can be concluded from GSM that the initial gas pressure of protected seam, the characteristics of interlayer rocks, and the ventilation pressure of PSWF were the main factors that influenced the desorption of gas emission from the protected seam into PSWF. The developed GSM was tested for calculating gas emission quantity from the PCSM process by utilizing the actual geological condition data of a coal mine, which is located in Hancheng, China. The results have shown great agreement with obtained field measurements, which is done by combining the fitting curve of ventilation air methane quantity for PSWF with an interlayer spacing. A loss coefficient (δ) of 1.012 × 10−3 was obtained in this study.

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“…However, when multi-layered coal seams are present, stress-relieved gas from adjacent coal seams can trigger a gas explosion [13] . Therefore, measures should be taken to ensure safe mining in the protective seam to realize safe and efficient coal mining with gas extraction.…”

Section: Geological and Engineering Conditionsmentioning

confidence: 99%

Gas Permeability Evolution Mechanism and Comprehensive Gas Drainage Technology for Thin Coal Seam Mining

2017

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Abstract:A thin coal seam mined as a protective coal seam above a gas outburst coal seam plays a central role in decreasing the degree of stress placed on a protected seam, thus increasing gas permeability levels and desorption capacities to dramatically eliminate gas outburst risk for the protected seam. However, when multiple layers of coal seams are present, stress-relieved gas from adjacent coal seams can cause a gas explosion. Thus, the post-drainage of gas from fractured and de-stressed strata should be applied. Comprehensive studies of gas permeability evolution mechanisms and gas seepage rules of protected seams close to protective seams that occur during protective seam mining must be carried out. Based on the case of the LongWall (LW) 23209 working face in the Hancheng coal mine, Shaanxi Province, this paper presents a seepage model developed through the FLAC3D software program (version 5.0, Itasca Consulting Group, Inc., Minneapolis, MI, USA) from which gas flow characteristics can be reflected by changes in rock mass permeability. A method involving theoretical analysis and numerical simulation was used to analyze stress relief and gas permeability evolution mechanisms present during broken rock mass compaction in a goaf. This process occurs over a reasonable amount of extraction time and in appropriate locations for comprehensive gas extraction technologies. In using this comprehensive gas drainage technological tool, the safe and efficient co-extraction of thin coal seams and gas resources can be realized, thus creating a favorable environment for the safe mining of coal and gas outburst seams.

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Stress redistribution of longwall mining stope and gas control of multi-layer coal seams

Cited by 53 publications

References 30 publications

Numerical Study on the Effectiveness of Grouting Reinforcement on the Large Heaving Floor of the Deep Retained Goaf-Side Gateroad: A Case Study in China

Numerical Study on the Effectiveness of Grouting Reinforcement on the Large Heaving Floor of the Deep Retained Goaf-Side Gateroad: A Case Study in China

A Gas Seepage Modeling Study for Mitigating Gas Accumulation Risk in Upper Protective Coal Seam Mining Process

Gas Permeability Evolution Mechanism and Comprehensive Gas Drainage Technology for Thin Coal Seam Mining

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