Numerical investigation of groundwater outbursts near faults in underground coal mines

Permeable geologic faults in the coal seam can cause intermittent production problems or unexpected amounts of groundwater outburst from the underlying aquifers. With the acknowledgment of the basic mechanism for groundwater outbursts, the groundwater outburst along the fault zones in coal mines are numerically investigated using RFPA, a numerical code based on FEM. The fracture initiation, propagation, and coalescence in the stressed strata and the seepage field evolution in the stress field are represented visually during the whole process of groundwater outburst. The numerically obtained damage evolution shows that the floor strata could be classified as three zones, i.e. mining induced fracture zone, intact zone and fault reactivation zone, in which the intact zone is the key part for resisting groundwater outburst and directly determines the effective thickness of water-resisting rock layer. With understanding of the evolution of stress field and seepage flow in floor strata, the groundwater outburst pathway is calibrated and the transformation of floor rock mass from water-resisting strata to outburst pathway is clearly illuminated. Moreover, it is shown that geometrical configuration, including inclination angle of faults and seam drop along faults, have an important influence on groundwater outburst. Finally, based on geological, hydrogeology survey and numerical results, the mechanism analysis of groundwater outburst in an engineering case is studied, which can provide significantly meaningful guides for the investigation on mechanism and prevention of groundwater outburst induced by faults in practice.

[1]  H. Kern,et al.  Development of damage and permeability in deforming rock salt , 2001 .

[2]  Md. Rafiqul Islam,et al.  Mining-induced fault reactivation associated with the main conveyor belt roadway and safety of the Barapukuria Coal Mine in Bangladesh: Constraints from BEM simulations , 2009 .

[3]  Agust Gudmundsson,et al.  Fracture networks and fluid transport in active fault zones , 2001 .

[4]  D. V. Griffiths.  COMPUTATION OF BEARING CAPACITY FACTORS USING FINITE ELEMENTS , 1982 .

[5]  Charles Fairhurst,et al.  On the validity of the ‘Brazilian’ test for brittle materials , 1964 .

[6]  Wang Qian-yuan,et al.  EXPLORATION OF STABILITY ANALYSIS METHODS FOR SURROUNDING ROCKS OF SOIL TUNNEL , 2008 .

[7]  Malgorzata Peszynska,et al.  Coupled fluid flow and geomechanical deformation modeling , 2003 .

[8]  L. Tham,et al.  Influence of Heterogeneity of Mechanical Properties on Hydraulic Fracturing in Permeable Rocks , 2004 .

[9]  Hyeong-Dong Park,et al.  Coal mining above a confined aquifer , 2003 .

[10]  Mingyu Wang,et al.  Investigations of groundwater bursting into coal mine seam floors from fault zones , 2004 .

[11]  C. Tang,et al.  Numerical simulation of progressive rock failure and associated seismicity , 1997 .

[12]  C. A. Tang,et al.  Coupled analysis of flow, stress and damage (FSD) in rock failure , 2002 .

[13]  Françoise Homand,et al.  Damage-induced permeability changes in granite: a case example at the URL in Canada , 2001 .

[14]  Leslie George Tham,et al.  Numerical studies of the influence of microstructure on rock failure in uniaxial compression — Part I: effect of heterogeneity , 2000 .

[15]  Jean-Claude Roegiers,et al.  Experimental Determination of Stress-Permeability Relationship , 2000 .

[16]  L.J. Donnelly,et al.  A review of coal mining induced fault reactivation in Great Britain , 2006, Quarterly Journal of Engineering Geology and Hydrogeology.

[17]  L. Tham,et al.  A coupled flow-stress-damage model for groundwater outbursts from an underlying aquifer into mining excavations , 2007 .

[18]  C. W. Li,et al.  Slope stability analysis by SRM-based rock failure process analysis (RFPA) , 2006 .

[19]  C. Tang,et al.  Microcrack statistics, Weibull distribution and micromechanical modeling of compressive failure in rock , 2006 .

[20]  James P. Evans,et al.  Permeability of fault-related rocks, and implications for hydraulic structure of fault zones , 1997 .

[21]  D. V. Griffiths,et al.  Enhanced visualization of failure mechanisms by finite elements , 1995 .

[22]  Lijun Han,et al.  Application of an Improved Flow-Stress-Damage Model to the Criticality Assessment of Water Inrush in a Mine: a Case Study , 2009 .

[23]  Suping Peng,et al.  Investigation of karst collapse based on 3-D seismic technique and DDA method at Xieqiao coal mine, China , 2009 .

[24]  C. Haberfield,et al.  Laboratory investigation of shaft resistance for piles socketed in basalt , 2004 .

[25]  C. Karacan,et al.  A numerical evaluation on the effects of impermeable faults on degasification efficiency and methane emissions during underground coal mining , 2008 .

[26]  James P. Evans,et al.  Fault zone architecture and permeability structure , 1996 .

[27]  J. P. Harrison,et al.  Development of a hydro-mechanical local degradation approach and its application to modelling fluid flow during progressive fracturing of heterogeneous rocks , 2005 .

[28]  David C. Glick,et al.  Coal and gas outbursts in footwalls of reverse faults , 2001 .

[29]  E. T. Brown,et al.  Rock Mechanics: For Underground Mining , 1985 .

[30]  G. S. Esterhuizen,et al.  Reservoir simulation-based modeling for characterizing longwall methane emissions and gob gas venthole production , 2007 .

[31]  Teng-fong Wong,et al.  The transition from brittle faulting to cataclastic flow in porous sandstones: Mechanical deformation , 1997 .

[32]  Nicholas H.S. Oliver,et al.  Fluid flow in extensional environments; numerical modelling with an application to Hamersley iron ores , 2004 .

[33]  M. Oda,et al.  Damage growth and permeability change in triaxial compression tests of Inada granite , 2002 .

[34]  Lian-guo Wang,et al.  Numerical Simulation of Coal Floor Fault Activation Influenced by Mining , 2006 .

[35]  Daigoro Hayashi,et al.  Finite element modeling of stress distributions and problems for multi-slice longwall mining in Bangladesh, with special reference to the Barapukuria coal mine , 2009 .

[36]  C. David,et al.  Mechanical compaction, microstructures and permeability evolution in sandstones , 2001 .

[37]  Md. Rafiqul Islam,et al.  Numerical simulation of stress distributions and displacements around an entry roadway with igneous intrusion and potential sources of seam gas emission of the Barapukuria coal mine, NW Bangladesh , 2009 .

[38]  Agust Gudmundsson,et al.  The effects of dykes and faults on groundwater flow in an arid land: the Red Sea Hills, Sudan , 2004 .

[39]  M. Zoback,et al.  Fluid flow along potentially active faults in crystalline rock: Geology , 1995 .

[40]  Baohong Shen,et al.  Coal mining under aquifers in China: a case study , 2004 .