煤矿采空区岩体渗透性计算模型及其数值模拟分析
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摘要
煤矿采空区岩体渗透性是煤矿采空区煤层气抽采设计的基本参数。从煤矿采空区岩体变形-破坏特征分析入手,通过理论分析研究了岩体渗透性与应力之间的耦合关系和模型,揭示了采空区岩体应力-应变和渗透性分布规律。研究结果表明:不同岩性岩石的渗透性在全应力-应变过程中为应变的函数,采空区岩体渗透性决定于岩体破坏程度和断裂的张开度,基于采空区岩体应力-应变导致断裂开度变化,推导了采空区岩体渗透系数与应力之间的三维关系与模型;应用FLAC~(3D)计算软件,对采空区岩体应力-应变-渗透性进行了数值模拟计算,分析了采空区岩体的变形破坏的分区分带特征,在纵向上自上而下形成弯曲下沉带、断裂带和垮落带;在横向上划分为原岩应力区、超前压力压缩区、卸载应力区和岩体应力恢复区;揭示了采空区岩体渗透性分布与采空区岩体应力-应变和破坏规律相一致的特征。无论是垂直渗透系数比(K_z/K_(z0)),还是水平渗透系数比(K_y/K_(y0)),均随着距开采煤层垂直距离的增大,采空区岩体渗透性逐渐减小,且采空区边缘的渗透系数较大,采空区两侧煤柱区岩体渗透性显著降低。
Permeability of rock mass is a basic parameter of CBM extraction design in coal mine goaf. Starting from the analysis of deformation and failure characteristics of rock mass in coal mine goaf,through theoretical analysis,the coupling relationship and model between the permeability and stress of rock mass was studied,then the distribution regularity of stress,strain and permeability in the coal goaf was revealed. Research results show that the permeability of different lithology rocks is considered as a function of strain in the stress-strain process,which depends on both the damage degree and the openness of fracture. Based on the openness of fracture caused by the stress-strain of rock mass in the goaf,the three dimensional relationship and model between the permeability and stress was deduced. Using the calculation software FLAC~(3D),the simulated calculation was carried out in the stress-strain-permeability of rock mass in thegoaf,the segmental characteristics of the deformation and failure of rock mass in the goaf was analyzed,which was formed into the bending subsidence zone,fractured zone and carving zone from top to bottom in the vertical direction and divided into the original in-situ stress area,abutment pressure compression area,unloading stress area and recovery area in the horizontal direction. The characteristics of the permeability distribution which is consistent with the stressstrain and failure law was revealed. Both the coefficient ratio of vertical permeability( K_z/ K_(z0)) and that of horizontal permeability( K_y/ K_(y0)) increase with the increase of the vertical distance from mining coal seam,the permeability of rock mass in the goaf gradually decreases,and the permeability coefficient on the edge of the goaf is larger,while the permeability on both sides of the coal pillar zone decreases significantly.
Permeability of rock mass is a basic parameter of CBM extraction design in coal mine goaf. Starting from the analysis of deformation and failure characteristics of rock mass in coal mine goaf,through theoretical analysis,the coupling relationship and model between the permeability and stress of rock mass was studied,then the distribution regularity of stress,strain and permeability in the coal goaf was revealed. Research results show that the permeability of different lithology rocks is considered as a function of strain in the stress-strain process,which depends on both the damage degree and the openness of fracture. Based on the openness of fracture caused by the stress-strain of rock mass in the goaf,the three dimensional relationship and model between the permeability and stress was deduced. Using the calculation software FLAC~(3D),the simulated calculation was carried out in the stress-strain-permeability of rock mass in thegoaf,the segmental characteristics of the deformation and failure of rock mass in the goaf was analyzed,which was formed into the bending subsidence zone,fractured zone and carving zone from top to bottom in the vertical direction and divided into the original in-situ stress area,abutment pressure compression area,unloading stress area and recovery area in the horizontal direction. The characteristics of the permeability distribution which is consistent with the stressstrain and failure law was revealed. Both the coefficient ratio of vertical permeability( K_z/ K_(z0)) and that of horizontal permeability( K_y/ K_(y0)) increase with the increase of the vertical distance from mining coal seam,the permeability of rock mass in the goaf gradually decreases,and the permeability coefficient on the edge of the goaf is larger,while the permeability on both sides of the coal pillar zone decreases significantly.
引文
[1]Meng Zhaoping,Shi Xiuchang,Li Guoqing.Deformation,failure and permeability of coal-bearing strata during longwall mining[J].Engineering Geology,2016,208:69-80.
[2]Kim J M,Parizek R R,Elsworth D.Evaluation of fully-coupled strata deformation and groundwater flow in response to longwall mining[J].International Journal of Rock Mechanics and Mining Sciences,1997,34(8):1187-1199.
[3]刘天泉.矿山岩体采动影响与控制工程学及其应用[J].煤炭学报,1995,20(1):1-5.Liu Tianquan.Influence of mining activities on mine rockmass and control engineering[J].Journal of China Coal Society,1995,20(1):1-5.
[4]Palchik V.Formation of fractured zones in overburden due to longwall mining[J].Environmental Geology,2003,44(1):28-38.
[5]Yavuz H.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.
[6]张金才,刘天泉,张玉卓.裂隙岩体渗透特征的研究[J].煤炭学报,1997,22(5):481-485.Zhang Jincai,Liu Tianquan,Zhang Yuzhuo.Study on the permeability of fractured rock mass[J].Journal of China Coal Society,1997,22(5):481-485.
[7]孟召平,王保玉,徐良伟,等.煤炭开采对煤层底板变形破坏及渗透性的影响[J].煤田地质与勘探,2012,40(2):39-43.Meng Zhaoping,Wang Baoyu,Xu Liangwei,et al.Influence of coal mining on the deformation-failure and permeability of seam floor[J].Coal Geology&Exploration,2012,40(2):39-43.
[8]孟召平,师修昌,刘珊珊,等.废弃煤矿采空区煤层气资源评价模型及应用[J].煤炭学报,2016,41(3):537-544.Meng Zhaoping,Shi Xiuchang,Liu Shanshan,et al.Evaluation model of CBM resources in abandoned coal mine and its application[J].Journal of China Coal Society,2016,41(3):537-544.
[9]王文学,隋旺华,董青红.应力恢复对采动裂隙岩体渗透性演化的影响[J].煤炭学报,2014,39(6):1031-1038.Wang Wenxue,Sui Wanghua,Dong Qinghong.Influence of cover stress re-establishment on the permeability evolution of the mininginduced fractures[J].Journal of China Coal Society,2014,39(6):1031-1038.
[10]朱斌,高峰,杨建文,等.深部薄层煤岩体裂隙-孔隙双渗流模拟研究[J].中国矿业大学学报,2014,43(6):987-994.Zhu Bin,Gao Feng,Yang Jianwen,et al.Simulation research on fissure-porosity double percolation in deep-buried thin layer coal rock mass[J].Journal of China University of Mining&Technology,2014,43(6):987-994.
[11]Schatzel S J,Karacan C,Dougherty H,et al.An analysis of reservoir conditions and responses in longwall panel overburden during mining and its effect on gob gas well performance[J].Engineering Geology,2012,127:65-74.
[12]Adhikary D P,Guo H.Modeling of longwall mining-induced strata permeability change[J].Rock Mechanics and Rock Engineering,2015,48(1):345-359.
[13]Louis C.A study of groundwater flow in jointed rock and its influence on the stability of rock masses[R].London:Imperial College of Science and Technology,1969.
[14]孟召平,侯泉林.高煤级煤储层渗透性与应力耦合模型及控制机理[J].地球物理学报,2013,56(2):667-675.Meng Zhaoping,Hou Quanlin.Coupling model of stress-dependent permeability in high-rank coal reservoir and its control mechanism[J].Chinese Journal of Geophysics,2013,56(2):667-675.
[15]Meng Zhaoping,Zhang Jincai,Wang Rui.In-situ stress,pore pressure,and stress-dependent permeability in the Southern Qinshui Basin[J].International Journal of Rock Mechanics&Mining Sciences,2011,48:122-131.
[16]陈育民,徐鼎平.FLAC/FLAC3D基础与工程实例[M].北京:中国水利水电出版社,2009.
[17]孟召平,田永东,李国富.沁水盆地南部地应力场特征及其研究意义[J].煤炭学报,2010,35(6):976-981.Meng Zhaoping,Tian Yongdong,Li Guofu.Characteristics of in-situ stress field in Southern Qinshui Basin and its research significance[J].Journal of China Coal Society,2010,35(6):976-981.
[18]王金安,谢和平,Kwasniewski M A,等.建筑物下厚煤层特殊开采的三维数值分析[J].岩石力学与工程学报,1999,18(1):12-16.Wang Jin’an,Xie Heping,Kwasniewski M A,et al.3-D numerical analysis on thick coalseam extraction by special mining method under buildings[J].Chinese Journal of Rock Mechanics and Engineering,1999,18(1):12-16.
[2]Kim J M,Parizek R R,Elsworth D.Evaluation of fully-coupled strata deformation and groundwater flow in response to longwall mining[J].International Journal of Rock Mechanics and Mining Sciences,1997,34(8):1187-1199.
[3]刘天泉.矿山岩体采动影响与控制工程学及其应用[J].煤炭学报,1995,20(1):1-5.Liu Tianquan.Influence of mining activities on mine rockmass and control engineering[J].Journal of China Coal Society,1995,20(1):1-5.
[4]Palchik V.Formation of fractured zones in overburden due to longwall mining[J].Environmental Geology,2003,44(1):28-38.
[5]Yavuz H.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.
[6]张金才,刘天泉,张玉卓.裂隙岩体渗透特征的研究[J].煤炭学报,1997,22(5):481-485.Zhang Jincai,Liu Tianquan,Zhang Yuzhuo.Study on the permeability of fractured rock mass[J].Journal of China Coal Society,1997,22(5):481-485.
[7]孟召平,王保玉,徐良伟,等.煤炭开采对煤层底板变形破坏及渗透性的影响[J].煤田地质与勘探,2012,40(2):39-43.Meng Zhaoping,Wang Baoyu,Xu Liangwei,et al.Influence of coal mining on the deformation-failure and permeability of seam floor[J].Coal Geology&Exploration,2012,40(2):39-43.
[8]孟召平,师修昌,刘珊珊,等.废弃煤矿采空区煤层气资源评价模型及应用[J].煤炭学报,2016,41(3):537-544.Meng Zhaoping,Shi Xiuchang,Liu Shanshan,et al.Evaluation model of CBM resources in abandoned coal mine and its application[J].Journal of China Coal Society,2016,41(3):537-544.
[9]王文学,隋旺华,董青红.应力恢复对采动裂隙岩体渗透性演化的影响[J].煤炭学报,2014,39(6):1031-1038.Wang Wenxue,Sui Wanghua,Dong Qinghong.Influence of cover stress re-establishment on the permeability evolution of the mininginduced fractures[J].Journal of China Coal Society,2014,39(6):1031-1038.
[10]朱斌,高峰,杨建文,等.深部薄层煤岩体裂隙-孔隙双渗流模拟研究[J].中国矿业大学学报,2014,43(6):987-994.Zhu Bin,Gao Feng,Yang Jianwen,et al.Simulation research on fissure-porosity double percolation in deep-buried thin layer coal rock mass[J].Journal of China University of Mining&Technology,2014,43(6):987-994.
[11]Schatzel S J,Karacan C,Dougherty H,et al.An analysis of reservoir conditions and responses in longwall panel overburden during mining and its effect on gob gas well performance[J].Engineering Geology,2012,127:65-74.
[12]Adhikary D P,Guo H.Modeling of longwall mining-induced strata permeability change[J].Rock Mechanics and Rock Engineering,2015,48(1):345-359.
[13]Louis C.A study of groundwater flow in jointed rock and its influence on the stability of rock masses[R].London:Imperial College of Science and Technology,1969.
[14]孟召平,侯泉林.高煤级煤储层渗透性与应力耦合模型及控制机理[J].地球物理学报,2013,56(2):667-675.Meng Zhaoping,Hou Quanlin.Coupling model of stress-dependent permeability in high-rank coal reservoir and its control mechanism[J].Chinese Journal of Geophysics,2013,56(2):667-675.
[15]Meng Zhaoping,Zhang Jincai,Wang Rui.In-situ stress,pore pressure,and stress-dependent permeability in the Southern Qinshui Basin[J].International Journal of Rock Mechanics&Mining Sciences,2011,48:122-131.
[16]陈育民,徐鼎平.FLAC/FLAC3D基础与工程实例[M].北京:中国水利水电出版社,2009.
[17]孟召平,田永东,李国富.沁水盆地南部地应力场特征及其研究意义[J].煤炭学报,2010,35(6):976-981.Meng Zhaoping,Tian Yongdong,Li Guofu.Characteristics of in-situ stress field in Southern Qinshui Basin and its research significance[J].Journal of China Coal Society,2010,35(6):976-981.
[18]王金安,谢和平,Kwasniewski M A,等.建筑物下厚煤层特殊开采的三维数值分析[J].岩石力学与工程学报,1999,18(1):12-16.Wang Jin’an,Xie Heping,Kwasniewski M A,et al.3-D numerical analysis on thick coalseam extraction by special mining method under buildings[J].Chinese Journal of Rock Mechanics and Engineering,1999,18(1):12-16.