Elastic-plastic analysis and shrinkage properties study of swelling rock boreholes in coalmines

  • Jifeng Hou College of Mining and Safety Engineering, Shandong University of Science and Technology
Keywords: swelling rock, elastic-plastic analysis, boreholes shrinkage, humidity stress field


The shrinkage of swelling rock boreholes in coalmines is a complex problem affected by multiple fields coupling, such as humidity field and stress field. By establishing the equilibrium equation of swelling rock boreholes in coalmines, considering the expansion and softening properties, the elastic-plastic mechanics analysis was carried out, and the plastic zone radius and radial displacement of the surrounding rock of the swelling rock in coalmines were determined under the coupling of humidity and stress field. According to an example based on the research background of the floor rock roadway in the 8# coal seam of Songzao Coal Mine in Chongqing, the calculation results were carried out, and the influences of water content, ground stress and water pressure inside the hole on boreholes shrinkage were studied. The results show that with the increase of water content  of the surrounding rock, the radius of plastic zone and radial displacement of borehole wall gradually increase; Both the humidity expansion and softening have an important influence on boreholes shrinkage in coalmines, and the radial displacement of borehole wall under the coupling of swelling and softening is greater than that of only considering expansion or softening; With the increase of the ground stress P, the radius of plastic zone and radial displacement of borehole wall gradually increase, showing a nonlinear increasing relation; The larger the water pressure in the boreholes, the smaller the radius of plastic zone and radial displacement of borehole walls, and properly increasing the water pressure in the boreholes can effectively control the boreholes shrinkage. The accuracy of theoretical analysis was further verified by indoor model tests. The results can provide a theoretical basis for solving the problem of boreholes shrinkage.


Qingquan Liu, Yuanping Cheng, Liang Yuan, et al. A new effective method and new materials for high sealing performance of cross-measure CMM drainage boreholes[J]. Journal of Natural Gas Science & Engineering , 2014 , 21 :805-813.

Yiyu Lu, Yong Liu, Xiaohong Li ,et al. A new method of drilling long boreholes in low permeability coal by improving its permeability [J]. International Journal of Coal Geology, 2010, 84(2): 94-102.

Chengwei Liu, Binwei Xia and Yiyu Lu. Coal bed Methane Extraction Using the Self-Oscillating Water Jet Slotting Method [J]. Energies, 2018, 11 (4): 897.

BARLA M. Numerical simulation of the swelling behaviour around tunnels based on special triaxial tests[J]. Tunnelling and Underground Space Technology, 2008, 23(5): 508–521.

BC Hawlader, KY Lo and ID Moore. Analysis of tunnels in shaly rock considering three-dimensional stress effects on swelling[J]. Canadian Geotechnical Journal, 2005, 42(1): 1–12.

Yiyu Lu, Xiang Ao, Jiren Tang, et al. Swelling of shale in supercritical carbon dioxide[J].Journal of Natural Gas Science & Engineering , 2016 , 30 (4) :268-275

Luciano Oldecop, Eduardo Alonso. Modelling the degradation and swelling of clayey rocks bearing calcium-sulphate[J]. International Journal of Rock Mechanics and Mining Sciences . 2012,54(22):90-102.

LR Davison, JH Atkinson. Continuous loading Oedometer Testing of Soils [J]. Quarterly Journal of Engineering Geology, London, 1990, Vol.23, 347-355.

F Yazdandoust , SS Yasrobi. Effect of cyclic wetting and drying on swelling behavior of polymer- stabilized swelling clays [J]. Applied Clay Science, 2010, 50 (4): 461- 468.

A.R. Estabragh, B. Parsaei and A.A. Javadi. Laboratory investigation of the effect of cyclic wetting and drying on the behaviour of an expansive soil[J] . Soils and Foundations . 2015 (2)

Maria B Diaz Aguado, C.Gonzalez Nicieza. Control and prevention of gas outbursts in coal mines [J].International Journal of Coal Geology . 2007,69(4):253-266.

Jx Liu, Zq Li and Sh Li. Protection against outburst mechanism of hydraulic extrusion measure in the front of coal road heading face [J].Journal of China Coal Society, 2006 , 31 (2) :183-186.

Fuchang Hao, Lijuan Sun and Weiqin Zuo. Hydraulic flushing aperture variation and anti-blocking technology considering rheological property[J]. Journal of China Coal Society,2016,41(6):1434-1440. (in Chinese)

Haiyang Wang, Binwei Xia, Yiyu Lu, et al. Study on the Propagation Laws of Hydrofractures Meeting a Faulted Structure in the Coal Seam[J].Energies , 2017 , 10 (5) :654.

Zhende Zhu, Aijun Zhang. Research on swelling and strain softening model of swelling rock in hongshanyao [J]. Chinese Journal of Rock Mechanics and Engineering.2005,24(3):389- 393.

F Valès, D Nguyen Minh, H Gharbi, ,et al. Experimental study of the influence of the degree of saturation on physical and mechanical properties in Tournemire shale (France)[J]. Applied Clay Science . 2004 , 26 (1) :197-207.

Qiangling Yao, Futao Zhang, Xiaolei Ding ,et al. Experimental research on instability mechanism of silty mudstone roofs under action of water and its application[J]. Procedia Earth and Planetary Science . 2009 ,1(1):402-408.

Xiexing Miao, Xianbiao Mao and Aihong Lu. Application of the humidity stress field theory to the soft surrounding rock stability control around coal mining roadway [J]. Ground Pressure and Strata Control, 2002, 3: 1-5. (in Chinese)

Xiexing Miao. Large deformation analysis of surrounding rock of a tunnel in swelling rock mass based on the humidity stress field theory [J]. Journal of China University of Mining & Technology, 1995, 24(1): 58-63. (in Chinese)

Xiexing Miao, Chengyong Yang, Zhida Chen. Humidity stress field theory in swelling rock mass [J]. Rock and Soil Mechanics,1993,14(4): 49-55. (in Chinese)

Marco Barla. Numerical simulation of the swelling behaviour around tunnels based on special triaxial tests[J]. Tunnelling and Underground Space Technology incorporating Trenchless Technology Research . 2008,23 (5):508-521.

Christoph Butscher, Peter Huggenberger and Eric Zechner. Impact of tunneling on regional groundwater flow and implications for swelling of clay–sulfate rocks[J]. Engineering Geology . 2010 , 117 (3) :198-206.

Kangquan LI, Zhigang Zhou. Deformation analysis of expansive soils induced by increased humidity based on the theory of humidity stress field[J]. Journal of Changsha University of Science and Technology,2005, 2 (4): 2–6. (in Chinese)

Zhenzhou Ding, Yingren Zheng and Lisheng Li. Trial study on variationregularity of swelling force[J]. Rock and Soil Mechanics,2007, 28(7): 1328–1332. (in Chinese)

Xigui Zheng, Ming Ji and Nong Zhang. Rheological model of swelling rock considering humidity effect[J]. Journal of China Coal Society,2012, 37(3): 396–401. (in Chinese)

Mechanical Engineering (2)