Research on movement and fracture laws of overlying strata in fully mechanized top-coal caving faces within shallow-buried weathered and oxidized zones

Abstract

Affected by the depositional environment, coal seams in the weathered and oxidized zone and their overlying strata are characterized by developed fractures and poor self-stability, leading to difficulties in roadway roadway and working face roof management. This paper analyzes the failure characteristics of coal-rock masses in this zone. Combined with model tests and numerical simulation methods, it investigates the stress distribution status, deformation-failure characteristics, and movement-fracture laws of the overlying strata in a fully mechanized top-coal caving working face. Results indicate: (1) Weathering and oxidation significantly degrade strength and increase plastic deformation in coal-rock masses; (2) Under mining-induced disturbance, overlying strata stress is released from the in-situ state and sharply reduced, forming stress concentration zones ahead of the coal wall and at face ends; (3) During mining, fractures propagating upwards from the coal wall trigger rib spalling and top-coal collapse, forming combined cantilever and articulated rock beam structures. The overlying strata seuentially undergo four deformation-failure stages: “bed separation → immediate roof fracture → main roof fracture → high-level strata collapse”. The research findings can provide a basis for the safe mining of fully mechanized top-coal caving faces in weathered and oxidized coal.

Keywords

wind oxidation zones / fully mechanized top coal caving mining / similarity model test / overburden failure characteristics / migration law

References

[1] Li C-t, He Y-l, Sun X-yet al. . Fracture evolution characteristics and deformation laws of overlying strata during the initial period of longwall mining: Case study [J]. Sustainability. 2023, 15(11): 8596.

[2] Yuan Y-f, Guo G-l, Huang Cet al. . Breakage patterns of high-level thick weakly cemented overburden for coal safe and sustainable mining [J]. Sustainability. 2024, 16: 5707.

[3] Guo W-b, Zhao G-b, Bai E-het al. . Effect of overburden bending deformation and alluvium mechanical parameters on surface subsidence due to longwall mining [J]. Bulletin of Engineering Geology and the Environment. 2021, 8032751-2764.

[4] Li L, Zhang S-x, Xue Y-let al. . Overburden breaking law and safe mining technology in thin bedrock stope with thick alluvium [J]. Applied Sciences. 2022, 122412833.

[5] Wang K-j, Zhai X-r, Tang Met al. . Exploration and evaluation of weathering zone of working face 1410(3) roof in zhangji coal mine, Huainan mining area [J]. Coal Technology. 2024, 435180-183(in Chinese)

[6] Zhang G-j, Guo G-l, Wei Wet al. . Mechanical properties and failure mechanism of the weakly cemented overburden in deep mining [J]. Minerals. 2022, 12(10): 1276.

[7] ZHU Deng-xing, GUO Yu, WANG Wei, et al. Grouting reinforcement technique in wind oxidation zone by power law superfine cement slurry considering the time-varying rheological parameters [J]. Advances in Civil Engineering, 2019: 2495850. DOI:https://doi.org/10.1155/2019/2495850.

[8] Tian M-l, Gao X-x, Zhang A-fet al. . Study on the deformation failure mechanism and coupling support technology of soft rock roadways in strong wind oxidation zones [J]. Engineering Failure Analysis. 2024, 156: 107840.

[9] Zhao Q-feng. Study on the mechanism and control of deformation, instability and collapse of wind-oxidized water-rich roadway. 2019(in Chinese)

[10] Khorasanipour M. Environmental mineralogy of Cuporphyry mine tailings, a case study of semi-arid climate conditions, Sarcheshmeh mine, SE Iran [J]. Journal of Geochemical Exploration. 2015, 15340-52.

[11] Zhou Z-q, Zhang F-lin. Study on reasonable height of water-proof coal pillar under ultrathin bedrock during coal mining [J]. China Mining Magazine. 2013, 221084-87(in Chinese)

[12] Deng B-l, Chen S-j, Tian M-let al. . Experimental study on mechanical properties of wind-oxidized sandstone reinforced by grouting under cyclic loading and unloading [J]. Sustainability. 2025, 17(5): 2190.

[13] Islavath S R, Deb D, Kumar H. Development of a roof-to-floor convergence index for longwall face using combined finite element modelling and statistical approach [J]. International Journal of Rock Mechanics and Mining Sciences. 2020, 127: 104221.

[14] Zhu J-z, Li W-p, Liu Y. Analysis of overburden deformation and migration under huge thick unconsolidated layers based on multiple approaches [J]. Minerals. 2022, 12121510.

[15] Yu L-q, Yao Q-l, Chong Z-het al. . Mechanical and micro-structural damage mechanisms of coal samples treated with dry - wet cycles [J]. Engineering Geology. 2022, 304106637.

[16] Liu J-s, Wang Y, Zuo J-pet al. . Asymmetric analogous hyperbola model of overburden movement and its verification [J]. Scientific Reports. 2024, 1415614.

[17] Sun B-y, Zhang P-s, Wu R-xet al. . Research on the overburden deformation and migration law in deep and extra-thick coal seam mining [J]. Journal of Applied Geophysics. 2021, 190104337.

[18] Cheng J-w, Sheng S-p, Xu Y-get al. . Deformation prediction of overlying strata in multi-seam mining based on the influence function method-key stratum hybrid model [J]. Geomechanics and Geophysics for Geo-Energy and Geo-Resources. 2024, 101178.

[19] Zhao K, Zhou Y, Yu Xet al. . Dynamic prediction model of overburden settlement in deep mining areas based on space - time relationship [J]. Natural Resources Research. 2021, 3053839-3852.

[20] Xie J-l, Li K, Zhang J-ket al. . Mining-induced displacement deformation law in full-columnar overburden and its design guidance in gas extraction [J]. Fuel. 2024, 363: 130934.

[21] Bai E-h, Li X-y, Guo W-bet al. . Characteristics and formation mechanism of surface residual deformation above longwall abandoned goaf [J]. Sustainability. 2022, 142315985.

[22] Li M, Zhang J-x, Huang Y-let al. . Measurement and numerical analysis of influence of key stratum breakage on mine pressure in top-coal caving face with super great mining height [J]. Journal of Central South University. 2017, 2481881-1888.

[23] Guo H-x, Yu W-j, Wu G-set al. . Mechanism of stratum instability and dynamic deformation under discontinuous boundary conditions [J]. Applied Sciences. 2024, 1441441.

[24] Wang X-f, Zhang Q, Liu W-get al. . Study on space - time evolution law and mechanism of instability failure of deep high-stress overburden rock [J]. Applied Sciences. 2023, 1374573.

[25] Cheng G, Xu W-t, Shi Bet al. . Experimental study on the deformation and failure mechanism of overburden rock during coal mining using a comprehensive intelligent sensing method [J]. Journal of Rock Mechanics and Geotechnical Engineering. 2022, 1451626-1641.

[26] Qin Z, Zhang R-c, Wang Ket al. . Shear damage constitutive model of rock-like joint surface considering the coupling effect of cyclic water intrusion and loading [J]. International Journal of Mining Science and Technology. 2025, 35(6): 881-895.

[27] Ma H-w, Sui W-h, Ni J-M. Environmentally sustainable mining: A case study on surface subsidence control of grouting into overburden [J]. Environmental Earth Sciences. 2019, 78(10): 320.

[28] Wang F, Chen T, Chen Z-tet al. . Failure analysis of overlying strata in fault fracture zone during coal mining [J]. Journal of Geophysics and Engineering. 2023, 2061127-1139.

[29] Tian M-l, Han L-j, Meng Q-bet al. . Physical model experiment of surrounding rock failure mechanism for the roadway under deviatoric pressure form mining disturbance [J]. KSCE Journal of Civil Engineering. 2020, 24(4): 1103-1115.

[30] Du H, Song D-q, Liu G-wet al. . Influence of the extra-thick coal seam exploitation on the deformation characteristics of the overlying rock mass in an open-pit mine slope [J]. Geomatics, Natural Hazards and Risk. 2023, 14(1): 1-23.

[31] Gao D-y, Sang S-x, Liu S-qet al. . Experimental study on the deformation behaviour, energy evolution law and failure mechanism of tectonic coal subjected to cyclic loads [J]. International Journal of Mining Science and Technology. 2022, 32(6): 1301-1313.

[32] Sun Y-j, Zuo J-p, Karakus Met al. . Investigation of movement and damage of integral overburden during shallow coal seam mining [J]. International Journal of Rock Mechanics and Mining Sciences. 2019, 117: 63-75.

[33] Zhang J-h, Cheng Z-h, Xing Y-wet al. . Roof stability analysis model of super-long fully mechanized working face and its application [J]. Geomechanics and Geophysics for Geo-Energy and Geo-Resources. 2024, 10(1): 189.

[34] Han P-h, Zhang C, Ren Z-pet al. . The influence of advance speed on overburden movement characteristics in longwall coal mining: Insight from theoretical analysis and physical simulation [J]. Journal of Geophysics and Engineering. 2021, 181163-176.

[35] Deng D-x, Wang H-w, Xie L-let al. . Experimental study on the interrelation of multiple mechanical parameters in overburden rock caving process during coal mining in longwall panel [J]. International Journal of Coal Science & Technology. 2023, 10(1): 47.

[36] Zhang J-w, Zhang Y-p, Yang S-let al. . Theoretical and experimental investigation on top coal drawing mechanism considering overburden pressures in longwall top-coal caving [J]. Rock Mechanics and Rock Engineering. 2025, 5832901-2927.

[37] Ren Y-w, Yuan Q, Chen Jet al. . Evolution characteristics of mining-induced fractures in overburden strata under close-multi coal seams mining based on optical fiber monitoring [J]. Engineering Geology. 2024, 343: 107802.

[38] Ye Q, Wang G, Jia Z-zet al. . Similarity simulation of mining-crack-evolution characteristics of overburden strata in deep coal mining with large dip [J]. Journal of Petroleum Science and Engineering. 2018, 165477-487.

[39] He C-c, Lu W-y, Zha W-het al. . A geomechanical method for predicting the height of a water-flowing fractured zone in a layered overburden of longwall coal mining [J]. International Journal of Rock Mechanics and Mining Sciences. 2021, 143: 104798.

[40] Yang Z-p, Zhao Q, Liu X-ret al. . Experimental study on the movement and failure characteristics of karst mountain with deep and large fissures induced by coal seam mining [J]. Rock Mechanics and Rock Engineering. 2022, 55(8): 4839-4867.

[41] Yuan Q, Chai J, Zhang D-det al. . Monitoring and characterization of mining-induced overburden deformation in physical modeling with distributed optical fiber sensing technology [J]. Journal of Lightwave Technology. 2020, 384881-888.

[42] Niu J-b, Liu Q. Experimental analysis of key stratum stability and overburden settlement monitoring combined OFDR and mining-crack-evolution characteristics [J]. Measurement. 2025, 250117167.

[43] Chai J, Ma Z, Zhang D-det al. . Experimental study on PPP-BOTDA distributed measurement and analysis of mining overburden key movement characteristics [J]. Optical Fiber Technology. 2020, 56102175.

[44] Zhu L, Gu W-z, Pan Het al. . Calculation model of overburden rock failure volume in mined-out area based on Brillouin optical time-domain analysis technology [J]. Optical Fiber Technology. 2021, 66102640.

[45] Gao L, Zhao H-b, Ji D-let al. . Fracture development and permeability evolution of overburden rocks containing faults [J]. Physics of Fluids. 2025, 372022028.

[46] Li C, Zhang L-k, Luo X-ret al. . Clay mineral transformations of Mesozoic mudstones in the central Junggar Basin, northwestern China: Implications for compaction properties and pore pressure responses [J]. Marine and Petroleum Geology. 2022, 144105847.

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