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Abstract

In deep mines, since the broken surrounding rocks & high-stress level of a roadway being near a coal seam, the creep characteristics of surrounding rocks should be considered as the main influencing factor in the selection for the roadway’s location of the lower coal seam. Both VI15 and VI16-17 coal seams of the Pingdingshan No. 4 Coal Mine, in China, Henan province, are close coal seams with a depth of around 900 m. According to the traditional formula calculation results, when the lower coal seam roadway is staggered 10 m to the upper coal seam goaf, the roadway pressure behaviour is significant, and the support becomes difficult. In this paper, the properties of surrounding rock were tested and the influence of lower coal seam on the stress state of surrounding rock is analysed by numerical simulation, and systematic analysis on the stress and creep characteristics of the surrounding rock of the mining roadway and its effects on the deformation is performed. The results demonstrated that the roadway’s locations in the lower coal seam can be initially divided into three zones: the zone with accelerated creep, the transition creep zone and the insignificant creep zone. The authors believed that the roadway layout in an insignificant creep zone can achieve a better supporting effect. Based on the geological conditions of the roadway 23070 of the VI16-17 coal seam of the Pingdingshan No. 4 Coal Mine, combined with the above analysis, a reasonable location of roadway (internal offset of 30 m) was determined using numerical simulation method. The reliability of the research results is verified by field measurement. The above results can provide a reference for selecting the roadway’s location under similar conditions.
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Bibliography


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[4] Y . Zhang, C.L. Zhang, C.C. Wei, Y.D. Liu, S.Q. Zhang, J.J. Zhao,. The Study on Roadway Layout in Coordination of Mining Coal Seams Base on Failure of Floor Strata. Trans Tech Publications 889-890, 1362-1374 (2014). DOI: https://doi.org/10.4028/www.scientific.net/AMR.889-890.1362
[5] W. Yang, C.Y. Liu, B.X. Huang, Y. Yang, Determination on Reasonable Malposition of Combined Mining in Close- Distance Coal Seams. Journal of Mining & Safety Engineering 29 (1), 101-105 (2012). DOI: https://doi.org/10.3969/j.issn.1673-3363.2012.01.018
[6] G . Yan, Y.Q. Hu, X. Song, Y.P. Fu, Z. Liu, Y. Yang, Theory and Physical Simulation of Conventional Staggered Distance during Combined Mining of Ultra-close Thin Coal Seam Group. Chinese Journal of Rock Mechanics & Engineering 28 (03), 591-597 (2009). DOI: https://doi.org/10.3321/j.issn:1000-6915.2009.03.019
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[9] C.L. Ju, G.D. Zhao, F. Gao, Coal Pillar Size of Ultra Closed Distance Seam and Layout of Mining Gateway. Advanced Materials Research 616-618, 465-470 (2012). DOI: https://doi.org/10.4028/www.scientific.net/AMR.616-618.465
[10] D .D. Qin, X.F. Wang, D.S. Zhang, X.Y. Chen, Study on Surrounding Rock-Bearing Structure and Associated Control Mechanism of Deep Soft Rock Roadway Under Dynamic Pressure. J. Sustainability, (2019), DOI: https://doi.org/10.3390/su11071892
[11] T. Majcherczyk, P. Małkowski, Z. Niedbalski, Rock Mass Movements Around Development workings in various density of standing-and-roof-bolting support. Journal of Coal Science and Engineering (China) 14 (3), 356-360 (2008). DOI: https://doi.org/10.1007/s12404-008-0078-1
[12] T. Majcherczyk, Z. Niedbalski, P. Małkowski, Ł. Bednarek, Analysis of yielding steel arch support with rock bolts in mine roadways stability aspect. Archives of Mining Sciences 59 (3), 641-654 (2014). DOI: https://doi.org/10.2478/amsc-2014-0045
[13] P. Małkowski, Z. Niedbalski, T. Majcherczyk, Ł. Bednarek, Underground monitoring as the best way of roadways support design validation in a long time period. J. Mining of Mineral Deposits 14 (3), 1-14 (2020). DOI : https://doi.org/10.33271/mining14.03.001
[14] X. Sun, A yielding bolt-grouting support design for a soft-rock roadway under high stress: a case study of the Yuandian No. 2 coal mine in China. Journal of the Southern African Institute of Mining and Metallurgy 118 (1), 71-82 (2018). DOI: https://doi.org/10.17159/2411-9717/2018/v118n1a9
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[16] H . Yan, M. Weng, R. Feng, W.K. Li, Layout and support design of a coal roadway in ultra-close multiple-seams. Journal of Central South University 22 (11), 4385-4395 (2015). DOI: https://doi.org/ 10.1007/s11771-015-2987-7
[17] Y .J. Qi, Q.H. Jiang, Z.J. Wang, C.B. Zhou, 3D creep constitutive equation of modified Nishihara model and its parameters identification. Chinese Journal of Rock Mechanics and Engineering 31 (2), 347-355 (2012). DOI: https://doi.org/10.3969/j.issn.1000-6915.2012.02.014
[18] A.M. Kovrizhnykh, Deformation and failure of open and underground mine structures under creep. Journal of Mining Science 45 (6), 541-550 (2009). DOI: https://doi.org/10.1007/s10913-009-0068-8
[19] I . Paraschiv-Munteanu, N.D. Cristescu, Stress relaxation during creep of rocks around deep boreholes. International Journal of Engineering Science 39 (7), 737-754 (2001). DOI: https://doi.org/10.1016/S0020-7225(00)00060-4
[20] H . Wang, W.Z. Chen, Q.B. Wang, P.Q.Zheng, Rheological properties of surrounding rock in deep hard rock tunnels and its reasonable support form. Journal of Central South University 23 (4), 898-905 (2016). DOI: https://doi.org/0.1007/s11771-016-3137-6
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Authors and Affiliations

Xufeng Wang
1
ORCID: ORCID
Jiyao Wang
1
ORCID: ORCID
Xuyang Chen
1
ORCID: ORCID
Zechao Chen
1
ORCID: ORCID

  1. Jiangsu Engineering Laboratory of Mine Earthquake Monitoring and Prevention, School of Mines, China University of Mining and Technology, Xuzhou 221116, China
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Abstract

The caving effect of the top coal caving is crucial for efficient mining. Using the Yushuling coal mine, Xinjiang province, China, as a case study, the coal and rock physical and mechanical parameters, such as the compressive, tensile, and shear strength values and hardness of the top coal and roof rock, were determined. The analysis of the effect of different factors on the blasting presplitting process was numerically simulated, and the optimal parameters of blast drilling were identified. Three presplit boreholes were implemented: in the workface, the workface’s advance area, and the two roadway roofs in the workface’s advance area. The optimal blasting drilling parameters and charge structure were designed. The field test results in the mine under study indicated that the top coal recovery rate of the 110501 fully mechanised top coal caving face was improved twice (from 40 to more than 80%), and an effective blasting presplitting was achieved. The proposed blasting presplitting method has an important guiding significance for fully mechanised top coal caving mining in Xinjiang and similar mining areas.
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Authors and Affiliations

Qiang Sun
1
ORCID: ORCID
Chengfang Shan
2
ORCID: ORCID
Zhongya Wu
1
ORCID: ORCID
Yunbo Wang
1
ORCID: ORCID

  1. China University of Mining and Technology, China
  2. Kuqa Yushuling Coal Mine Co., Ltd, Kuqa, Aksu, China
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Abstract

Mining the lower seams in a sequence of shallow, closely spaced coal seams causes serious air leakage in the upper goaf; this can easily aggravate spontaneous combustion in abandoned coal. Understanding the redevelopment of fractures and the changes in permeability is of great significance for controlling coal spontaneous combustion in the upper goaf. Based on actual conditions at the 22307 working face in the Bulianta coal mine, Particle Flow Code (PFC) and a corresponding physical experiment were used to study the redevelopment of fractures and changes in permeability during lower coal seam mining. The results show that after mining the lower coal seam, the upper and lower goafs become connected and form a new composite goaf. The permeability and the number of fractures in each area of the overlying strata show a pattern of „stability-rapid increase-stability“ as the lower coal seam is mined and the working face advances. Above the central area of goaf, the permeability has changed slightly, while in the open-cut and stop line areas are significant, which formed the main air leakage passage in the composite goaf.

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Authors and Affiliations

Zhenqi Liu
Xiaoxing Zhong
Botao Qin
Hongwei Ren
Ang Gao
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Abstract

As one of the key techniques in the fully mechanized mining process, equipment selection and matching has a great effect on security, production and efficiency. The selection and matching of fully mechanized mining equipment in thin coal seam are restricted by many factors. In fully mechanized mining (FMM) faced in thin coal seams (TCS), to counter the problems existing in equipment selection, such as many the parameters concerned and low automation, an expert system (ES) of equipment selection for fully mechanized mining longwall face was established. A database for the equipment selection and matching expert system in thin coal seam, fully mechanized mining face has been established. Meanwhile, a decision-making software matching the ES was developed. Based on several real world examples, the reliability and technical risks of the results from the ES was discussed. Compared with the field applications, the shearer selection from the ES is reliable. However, some small deviations existed in the hydraulic support and scraper conveyor selection. Then, the ES was further improved. As a result, equipment selection in fully mechanized mining longwall face called 4301 in the Liangshuijing coal mine was carried out by the improved ES. Equipment selection results of the interface in the improved ES is consistent with the design proposal of the 4301 FMM working face. The reliability of the improved ES can meet the requirements of the engineering. It promotes the intelligent and efficient mining of coal resources in China.

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Authors and Affiliations

Chen Wang
ORCID: ORCID
Jie Chen
Cheng Liu
Chengyu Jiang
ORCID: ORCID
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Abstract

The knowledge of the dynamic elastic properties of a coal seam is important in the context of various types of calculations of the seam behavior under various stress-strain conditions. These properties are often used in numerical and analytical modeling related to maintaining the stability of excavations and the analysis of mechanisms, e.g. related to the risk of rock bursts. Additionally, during the implementation of seismic surveys, e.g. seismic profiling and seismic tomography in coal seams, the reference values of the elastic properties of coal are used in the calculation of relative stresses in various geological and mining conditions.
The study aims to calculate the dynamic elastic parameters of the coal seam located at a depth of 1,260 m in one of the hard coal mines in the Upper Silesian Coal Basin (USCB). Basic measurements of the velocity of P- and S-waves were conducted using the seismic profiling method. These surveys are unique due to the lack of the velocity wave values in the coal seam at such a great depth in the USBC and difficult measurement conditions in a coal mine. As a result, dynamic modulus of elasticity was calculated, such as Young’s modulus, volumetric strain modulus, shear modulus and Poisson’s ratio. The volumetric density of coal used for calculations was determined on the basis of laboratory tests on samples taken in the area of the study. The research results showed that the calculated mean P-wave velocity of 2,356 m/s for the depth of 1,260 m is approximately consistent with the empirical relationship obtained by an earlier study. The P-wave velocity can be taken as the reference velocity at a depth of approx. 1,260 m in the calculation of the seismic anomaly in the seismic profiling method.
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Bibliography

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Chlebowski, D. and Burtan, Z. 2021. Geophysical and analytical determination of overstressed zones in exploited coal seam: A case study. Acta Geophys. 69, pp. 701–710. DOI: 10.1007/s11600-021-00547-z.

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Dubiński, J. 1989. Seismic method of shock hazard assessment in hard coal mines (Sejsmiczna metoda wyprzedzającej oceny zagrożenia wstrząsami górniczymi w kopalniach węgla kamiennego). Prace Głównego Instytutu Górnictwa. Katowice: Central Mining Institute, 163 pp. (in Polish).

Dubiński, J. and Konopko, W. 2000. Rock bursts – assessment, prognosis, defeating (Tąpania – ocena, prognoza, zwalczanie). Katowice: Central Mining Institute, 378 pp. (in Polish).

Dubiński et al. 2001 – Dubiński, J., Pilecki, Z. and Zuberek, W. 2001. Geophysical research in mines – past, present and future plans (Badania geofizyczne w kopalniach – przeszłość, teraźniejszość, i zamierzenia na przyszłość). Kraków: MEERI PAS (in Polish).

Gustkiewicz, J. ed. 1999. Physical properties of Carboniferous rocks of the Upper Silesian coal basin. Rocks of Saddle beds (Właściwości fizyczne wybranych skał karbońskich Górnośląskiego Zagłębia Węglowego – skały warstw siodłowych). Kraków: MEERI PAS, 267 pp. (in Polish).

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Authors and Affiliations

Krzysztof Krawiec
1
ORCID: ORCID

  1. Mineral and Energy Economy Research Institute, Polish Academy of Sciences, Kraków, Poland
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Abstract

The deformation and failure law of stope roofs is more complicated than horizontal coal seams affected by the angle of the coal seam during the mining process of steeply dipping coal seams. This study focused on and analysed the working face of a 2130 coal mine with steep dipping and large mining height. Through the use of numerical calculation, theoretical analysis, physical similar material simulation experiments, and field monitoring, the distribution characteristics of roof stress, as well as the threedimensional caving migration and filling law, in large mining height working faces under the dip angle effect was investigated. The influence mechanism of the dip angle change on the roof stability of large mining heights was investigated. The results revealed that the roof stress was asymmetrically distributed along the inclination under the action of the dip angle, which resulted in roof deformation asymmetry. With the increase in the dip angle, the rolling and sliding characteristics of roof-broken rock blocks were more obvious. The length of the gangue support area increased, the unbalanced constraint effect of the filling gangue on the roof along the dip and strike was enhanced, and the height of the caving zone decreased. The stability of the roof in the lower inclined area of the working face was enhanced, the failure range of the roof migrated upward, and the damage degree of the roof in the middle and upper areas increased. Furthermore, cross-layer, large-scale, and asymmetric spatial ladder rock structures formed easily. The broken main roof formed an anti-dip pile structure, and sliding and deformation instability occurred, which resulted in impact pressure. This phenomenon resulted in the dumping and sliding of the support. The ‘support-surrounding rock’ system was prone to dynamic instability and caused disasters in the surrounding rock. The field measurement results verified the report and provided critical theoretical support for field engineering in practice.
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Authors and Affiliations

Panshi Xie
1 2
Baofa Huang
1 2
Yongping Wu
1 2
ORCID: ORCID
Shenghu Luo
2 3
ORCID: ORCID
Tong Wang
1 2
ORCID: ORCID
Zhuangzhuang Yan
1 2
Jianjie Chen
4

  1. Xi’an University of Science and Technology, School of Energy Engineering, Xi’an 710054, China
  2. Xi’an University of Science and Technology, Key Laboratory of Western Mine Exploitation and Hazard Prevention Ministry of Educat ion, Xi’an 710054, China
  3. Xi’an University of Science and Technology, Department of Mechanics, Xi’an, 710054, China
  4. Xinjiang Coking Coal Group Corporat ion Limited, Xinjiang 830025, China

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