Stability analysis of inclined bauxite pillar under goaf of coal seam considering principal stress rotation

Abstract

The “upper coal and lower bauxite” resource distribution pattern is widespread in China, where mining of the overlying coal seam significantly alters the stress environment of the underlying bauxite layer. This study investigates the stability of inclined bauxite pillars under the influence of stress redistribution caused by coal seam extraction. A theoretical model is developed to calculate the direction and magnitude of principal stresses in the inclined floor strata, and a pillar stability analysis model is established that considers the effect of principal stress rotation. The research employs a combination of theoretical analysis, physical modeling, numerical simulation, and field observation. Findings indicate that stress rotation is most pronounced at both ends of the coal seam goaf, with the maximum clockwise and counterclockwise rotation angles of 19° and −40°, respectively, observed in the bauxite layer. Inclined bauxite pillars are subjected to combined compressive and shear loading. Under such conditions, clockwise rotation of principal stress increases the shear-to-normal stress ratio, thereby reducing pillar stability. Pillars located beneath the coal wall are the first to fail due to stress concentration and principal stress rotation, which can trigger a cascade of instability among the adjacent pillars. The findings provide a theoretical basis and practical guidance for ensuring the safe co-mining of coal seams and bauxite resources.

Keywords

principal stress rotation / theoretical model / inclined bauxite pillar / stability analysis / floor stress distribution

References

[1] Wang T, Sun J, Lin Z-y, et al.. Coordinated exploration model and its application to coal and coal-associated deposits in coal basins of China [J]. Acta Geologica Sinica - English Edition, 2021, 95(4): 1346-1356

[2] Tang Y, Zhu W-b, Xie J-l, et al.. Energy release and disaster-causing mechanism of ore-pillar combination [J]. Minerals Engineering, 2024, 219: 109082

[3] Li Y, Pan S-q, Ning S-z, et al.. Coal measure metallogeny: Metallogenic system and implication for resource and environment [J]. Science China Earth Sciences, 2022, 65(7): 1211-1228

[4] Gao L, Li J-h, Wang D-h, et al.. Outline of metallogenic regularity of bauxite deposits in China [J]. Acta Geologica Sinica - English Edition, 2015, 89(62072-2084

[5] Li S, Zhang R, Feng R, et al.. Feasibility of recycling bayer process red mud for the safety backfill mining of layered soft bauxite under coal seams [J]. Minerals, 2021, 11(7): 722

[6] Jiang L-c, Shen B-b, Xue L-L. Determining the critical blasting load of cracked strip bauxite pillars [J]. Bulletin of Engineering Geology and the Environment, 2021, 80(64639-4650

[7] Wang X-r, Guan K, Liu J, et al.. Instability and pillar burst mechanism in roof-pillar system with rock beam embedded in elastic foundation [J]. Bulletin of Engineering Geology and the Environment, 2021, 80(3): 2447-2459

[8] Tan Y-l, Ma Q, Liu X-l, et al.. Study on the disaster caused by the linkage failure of the residual coal pillar and rock stratum during multiple coal seam mining: Mechanism of progressive and dynamic failure [J]. International Journal of Coal Science & Technology, 2023, 10(1): 45

[9] Rumbaugh G M, Mark C, Kostecki T R. Massive pillar collapses in US underground limestone mines: 2015–2021 [J]. Mining, Metallurgy & Exploration, 2023, 40(51547-1556

[10] Wang Z-k, Li W-p, Hu Y-bo. Experimental study on mechanical behavior, permeability, and damage characteristics of Jurassic sandstone under varying stress paths [J]. Bulletin of Engineering Geology and the Environment, 2021, 80(6): 4423-4439

[11] Pan W-d, Jiang P, Li B-y, et al.. The spatial evolution law and water inrush mechanism of mining-induced overburden in shallow and short coal seam group [J]. Sustainability, 2022, 14(9): 5320

[12] Qin Y, Xu N-x, Zhang Z-j, et al.. Failure process of rock strata due to multi-seam coal mining: Insights from physical modelling [J]. Rock Mechanics and Rock Engineering, 2021, 54(52219-2232

[13] Fang S-j, Liang B, Sun W-j, et al.. Study on stress evolution law of upper coal seam in long-distance advance mining of lower coal seam [J]. Energy Science & Engineering, 2023, 11(5): 1753-1769

[14] Zhang J, Wu J-j, Yang T, et al.. Analysis of fracture evolution characteristics and formation mechanism of inter-layer rock under different mining areas [J]. Rock Mechanics and Rock Engineering, 2024, 57(5): 3787-3811

[15] Cui G-l, Wei J, Feng X-t, et al.. Preliminary study on the feasibility of co-exploitation of coal and uranium [J]. International Journal of Rock Mechanics and Mining Sciences, 2019, 123: 104098

[16] Yuan A-y, Wang P, Li Y. Movement laws of overlying strata and prevention measures of dynamic disasters under deep adjacent coal seam group with high gas [J]. Geomatics, Natural Hazards and Risk, 2020, 11(1): 2340-2360

[17] Huang B-x, Zhao X-l, Yu B, et al.. Research framework of theory and technology for coordinated mining of coal and its co-existed and associated strategic metal minerals [J]. Journal of the China Coal Society, 2022, 47(72516-2533(in Chinese)

[18] Zhang D-y, Sui W-h, Liu J-W. Overburden failure associated with mining coal seams in close proximity in ascending and descending sequences under a large water body [J]. Mine Water and the Environment, 2018, 37(2): 322-335

[19] Lin N, Sasaoka T, Shimada H, et al.. Numerical analysis of interaction effects in double extra-thick coal seams mining [J]. Procedia Earth and Planetary Science, 2013, 6: 343-349

[20] Huang Q-s, Cheng J-L. Analytical model of stress field and failure depth in multilayered rock masses of mining floor based on the transfer matrix method [J]. Geotechnical and Geological Engineering, 2017, 35(6): 2781-2788

[21] Liang Z-z, Song W-c, Liu W-T. Theoretical models for simulating the failure range and stability of inclined floor strata induced by mining and hydraulic pressure [J]. International Journal of Rock Mechanics and Mining Sciences, 2020, 132: 104382

[22] Li J-z, Ti Z-y, Zhang F, et al.. Research on failure characteristics of goaf floor in the inclined coal seam based on the fracture mechanics [J]. SN Applied Sciences, 2020, 2(12): 2065

[23] Cao M, Yin S-x, Xu B. Water inrush and failure characteristics of coal seam floor over a confined aquifer [J]. Energy Reports, 2021, 7: 8298-8311

[24] He T, Li G-d, Sun C, et al.. Floor failure characteristics of thick coal seam mining above confined aquifer [J]. Mining, Metallurgy & Exploration, 2022, 39(41553-1562

[25] Shan R-l, Li Z-l, Wang C-h, et al.. Study on distortion energy and stability of gob floor based on stress deviator field [J]. Energy Science & Engineering, 2022, 10(8): 2756-2771

[26] Liu Y-h, Zhao H-b, Ding H, et al.. Characterization of arching effect and failure mode of longwall panel floor [J]. Engineering Failure Analysis, 2022, 138: 106427

[27] Liu Y-m, Mao H-j, Xu C-m, et al.. DEM investigation on the mechanical behavior of mudstone in the hollow cylinder torsional shear test [J]. Computers and Geotechnics, 2021, 137: 104236

[28] Gu L-j, Feng X-t, Kong R, et al.. Effect of principal stress direction interchange on the failure characteristics of hard rock [J]. International Journal of Rock Mechanics and Mining Sciences, 2023, 164: 105365

[29] Wang Z-h, Yang S-l, Tang Y-s, et al.. A stress rotation-based method for improving roof stability of a deep longwall panel [J]. International Journal of Geomechanics, 2023, 23(7): 04023085

[30] Wu X-y, Wang S, Gao E-p, et al.. Failure mechanism and stability control of surrounding rock in mining roadway with gentle slope and close distance [J]. Engineering Failure Analysis, 2023, 152: 107489

[31] Zhai W-l, He F-l, Li L, et al.. Study on deflection of principal stress and deformation characteristics of roadway surrounding rock under mining action in close-distance coal seams [J]. Geomatics, Natural Hazards and Risk, 2023, 14(12227327

[32] Prassetyo S H, Irnawan M A, Simangunsong G M, et al.. New coal pillar strength formulae considering the effect of interface friction [J]. International Journal of Rock Mechanics and Mining Sciences, 2019, 123: 104102

[33] Zhang C, Zhao Y-x, Han P-h, et al.. Coal pillar failure analysis and instability evaluation methods: A short review and prospect [J]. Engineering Failure Analysis, 2022, 138: 106344

[34] Vlachogiannis I, Benardos A. Proposed formulas for pillar stress estimation in a regular room-and-pillar pattern [J]. International Journal of Rock Mechanics and Mining Sciences, 2024, 180: 105826

[35] Poulsen B A. Coal pillar load calculation by pressure arch theory and near field extraction ratio [J]. International Journal of Rock Mechanics and Mining Sciences, 2010, 47(71158-1165

[36] Bieniawski Z T. In situ strength and deformation characteristics of coal [J]. Engineering Geology, 1968, 2(5325-340

[37] Sheorey P R, Das M N, Barat D, et al.. Coal pillar strength estimation from failed and stable cases [J]. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 1987, 24(6): 347-355

[38] Reed G, Mctyer K, Frith R. An assessment of coal pillar system stability criteria based on a mechanistic evaluation of the interaction between coal pillars and the overburden [J]. International Journal of Mining Science and Technology, 2017, 27(1): 9-15

[39] Xia K-z, Chen C-x, Zhou Y-c, et al.. Catastrophe instability mechanism of the pillar-roof system in gypsum mines due to the influence of relative humidity [J]. International Journal of Geomechanics, 2019, 19(4): 06019004

[40] Wang X-r, Guan K, Yang T-h, et al.. Instability mechanism of pillar burst in asymmetric mining based on cusp catastrophe model [J]. Rock Mechanics and Rock Engineering, 2021, 54(31463-1479

[41] Wang M-z, Cai M. Numerical modeling of time-dependent spalling of rock pillars [J]. International Journal of Rock Mechanics and Mining Sciences, 2021, 141: 104725

[42] Dong H-y, Zhu W-c, Niu L-l, et al.. Numerical and theoretical study of load transfer behavior during cascading pillar failure [J]. Journal of Rock Mechanics and Geotechnical Engineering, 2024, 16(8): 3014-3033

[43] Li C-q, Zhou J, Armaghani D J, et al.. Stochastic assessment of hard rock pillar stability based on the geological strength index system [J]. Geomechanics and Geophysics for Geo-Energy and Geo-Resources, 2021, 7(247

[44] Jessu K V, Spearing A J S. Performance of inclined pillars with a major discontinuity [J]. International Journal of Mining Science and Technology, 2019, 29(3437-443

[45] Xiong Z-p, Li Y-h, Li K-m, et al.. Study on overburden stability control by expandable pillar support for multi-stope mining in a gently inclined thin orebody [J]. Arabian Journal for Science and Engineering, 2024, 49(4): 4785-4802

[46] Yavuz H. An estimation method for cover pressure reestablishment distance and pressure distribution in the goaf of longwall coal mines [J]. International Journal of Rock Mechanics and Mining Sciences, 2004, 41(2): 193-205

[47] Feng G-r, Hao C-l, Wang P-f, et al.. Asymmetric deformation mechanism and control measures for mining roadway under gob in close proximity [J]. Journal of China University of Mining and Technology, 2022, 51: 617-631(in Chinese)

[48] Yang Y-g, Shang R-p, Huang B-x, et al.. Study on the law of overburden rock movement and fissure development in coal and aluminum co-mining based on particle discrete element method [J]. Journal of Mining & Safety Engineering, 2024, 41(1): 58-66

[49] Yang S, Hua X-z, Liu X, et al.. Stability analysis and support countermeasures of coal wall in large cross-section roadway [J]. Geotechnical and Geological Engineering, 2022, 40(7): 3735-3747

[50] Huang B-x, Zhao X-l, Han X-k, et al.. Collaborative development of co-existed and associated minerals in the coal series [J]. Journal of Mining & Safety Engineering, 2024, 41(1): 1-14

[51] Hauquin T, Deck O, Gunzburger Y. Average vertical stress on irregular elastic pillars estimated by a function of the relative extraction ratio [J]. International Journal of Rock Mechanics and Mining Sciences, 2016, 83: 122-134

[52] Pariseau W G. Design analysis in rock mechanics [M], 20173rd edition337345

[53] Luo B-y, Ye Y-c, Hu N-y, et al.. Investigation of dip effect on uniaxial compressive strength of inclined rock sample by experimental and theoretical models [J]. Rock Mechanics and Rock Engineering, 2020, 53(12): 5659-5675

[54] Sun L-j, Li P-c, Luo B-y, et al.. Dip effect on the orientation of rock failure plane under combined compression-shear loading [J]. Scientific Reports, 2024, 14: 4406

[55] Fan G-w, Fan Z-l, Zhang D-s, et al.. Rock strength and permeability under compression-shear coupling corresponding to different loading angles [J]. Journal of the China Coal Society, 2024, 49(7): 3090-3101(in Chinese)

[56] Krauland N, Soder P E. Determining pillar strength from pillar failure observation [J]. Engineering and Mining Journal, 1987, 188: 34-40

[57] Zhu D-f, Wang D-y, Yu B-B. DEM-ML investigation of bauxite pillar strength prediction method [J]. Journal of China Coal Society, 2024, 49(73038-3050(in Chinese)

[58] Li Y, Wang N, Lei X-h, et al.. Stress evolution of repeated mining based on the double-yield model in multiple coal seam [J]. Rock Mechanics and Rock Engineering, 2024, 57(4): 2809-2827

RIGHTS & PERMISSIONS

Central South University