Numerical investigation into effect of rear barrier pillar on stress distribution around a longwall face

Abstract

Numerical investigation was performed to examine the effect of rear barrier pillar on stress distribution around a longwall face. Salamon theoretical formula was used to calculate the parameters of the caving zone, which was later assigned to double yield constitutive model in FLAC^3D. Numerical results demonstrate that high stress concentration zone exists above the region where the second open-off cut intersects with the rear barrier pillar due to stress transfer and plastic zone expansion. It is also found that the maximum vertical stresses with varied distance to the seam floor are all within the projective plane of the rear barrier pillar and their positions concentrate on the barrier pillar adjacent to the connection corner of the second open-off cut. In addition, position of the maximum vertical stresses abruptly transfer from the connection corner adjacent to former panel to that adjacent to current panel along the panel direction.

Keywords

numerical investigation / stress distribution / rear barrier pillar / second open-off cut / stress transfer

References

[1] BradyB H G, BrownE TRock mechanics: For underground mining [M], 2004New YorkSpringer

[2] PengS SLongwall mining [M], 2006Morgantown, WVWest Virginia University, Department of Mining Engineering

[3] GaoF-q, SteadD, CogganJ. Evaluation of coal longwall caving characteristics using an innovative UDEC Trigon approach [J]. Computers and Geotechnics, 2014, 55: 448-460

[4] JuJ-f, XuJ-lin. Structural characteristics of key strata and strata behaviour of a fully mechanized longwall face with 7.0 m height chocks [J]. International Journal of Rock Mechanics and Mining Sciences, 2013, 58: 46-54

[5] WangH-w, JiangY-d, ZhaoY-x, ZhuJ, LiuShuai. Numerical investigation of the dynamic mechanical state of a coal pillar during longwall mining panel extraction [J]. Rock Mechanics and Rock Engineering, 2013, 46(5): 1211-1221

[6] WangS Y, SloanS W, HuangM L, TangC A. Numerical study of failure mechanism of serial and parallel rock pillars [J]. Rock Mechanics and Rock Engineering, 2011, 44(2): 179-198

[7] YangJ-p, CaoS-g, LiX-hua. Failure laws of narrow pillar and asymmetric control technique of gob-side entry driving in island coal face [J]. International Journal of Mining Science and Technology, 2013, 23(2): 267-272

[8] WangX-bin. Analysis of progressive failure of pillar and instability criterion based on gradient-dependent plasticity [J]. Journal of Central South University of Technology, 2004, 11(4): 445-450

[9] ShabanimashcoolM, LiC C. A numerical study of stress changes in barrier pillars and a border area in a longwall coal mine [J]. International Journal of Coal Geology, 2013, 106: 39-47

[10] ChenS-j, GuoW-j, ZhouH, ShenB-t, LiuJ-bo. Field investigation of long-term bearing capacity of strip coal pillars [J]. International Journal of Rock Mechanics and Mining Sciences, 2014, 70: 109-114

[11] ZhangL-y, DengK-z, ZhuC-g, XingZ-quan. Analysis of stability of coal pillars with multi-coal seam strip mining [J]. Transactions of Nonferrous Metals Society of China, 2011, 21: s549-s555

[12] ZhangY, WanZ-j, LiF-c, ZhouC-b, ZhangB, GuoF, ZhuC-tan. Stability of coal pillar in gob-side entry driving under unstable overlying strata and its coupling support control technique [J]. International Journal of Mining Science and Technology, 2013, 23(2): 193-199

[13] HokeE, BrownE T. Practical estimates of rock mass strength [J]. International Journal of Rock Mechanics and Mining Sciences, 1997, 34(8): 1165-1186

[14] LuC-p, DouL-ming. The relationship between vertical stress gradient, seismic, and electromagnetic emission signals at Sanhejian coal mine, China [J]. International Journal of Rock Mechanics and Mining Sciences, 2014, 70(1): 90-100

[15] GaoF-q, SteadD, CogganJ. Evaluation of coal longwall caving characteristics using an innovative UDEC Trigon approach [J]. Computers and Geotechnics, 2014, 55: 448-460

[16] PengS SCoal mine ground control [M], 1986New YorkWiley

[17] ITASCA.FLAC3D version 4. 0 [M], 2009Minneapolis, MinnesotaItasca Consulting Group Inc.

[18] WardleL. The use of numerical modeling for underground coal mine design [C]// HUDSON J A. Comprehensive Rock Engineering, 1993OxfordPergamon733-748

[19] PappasD M, MarkC. Behavior of simulated longwall gob material [M]. US Department of the Interior, Bureau of Mines, 1993

[20] SalamonM D G. Mechanism of caving in longwall coal mining [C]// Rock Mechanics Contributions and Challenges: Proceedings of the 31st US Symposium. Golden, Colorado, 1990161-168

[21] YavuzH. An estimation method for cover pressure re-establishment 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

[22] DouL-m, HeHu. Study of OX-F-T spatial structure evolution of overlying strata in coal mines [J]. Chinese Journal of Rock Mechanics and Engineering, 2012, 31(3): 453-460

[23] XuW-q, WangE-y, ShenR-x, SongD-z, ZhangJ-min. Distribution pattern of front abutment pressure of fully-mechanized working face of soft coal isolated island [J]. International Journal of Mining Science and Technology, 2012, 22(2): 279-284

[24] ZhangN, ZhangN-c, HanC-l, QianD-yu. Borehole stress monitoring analysis on advanced abutment pressure induced by Longwall Mining [J]. Arabian Journal of Geosciences, 2014, 7(2): 457-463

[25] WangH-w, JiangY-d, ZhuJ, ShanR-y, WangChen. Numerical investigation on the assessment and mitigation of coal bump in an island longwall panel [J]. International Journal of Mining Science and Technology, 2013, 23(5): 625-630

[26] LiangS, ElsworthD, LiX, YangD. Topographic influence on stability for gas wells penetrating longwall mining areas [J]. International Journal of Coal Geology, 2014, 132: 23-36

[27] QianM-g, XuJ-lin. Study on the “O-shape” circle distribution characteristics of mining-induced fractures in the overlaying strata [J]. Journal of China Coal Society, 1998, 23(5): 466-469