应力恢复对采动裂隙岩体渗透性演化的影响  

Influence of cover stress re-establishment on the permeability evolution of the mining-induced fractures

作　　者：王文学[1,2] 隋旺华[1,2] 董青红[1,2] 

机构地区：[1]中国矿业大学资源与地球科学学院,江苏徐州221008 [2]中国矿业大学深部岩土力学与地下工程国家重点实验室,江苏徐州221008

出　　处：《煤炭学报》2014年第6期1031-1038,共8页Journal of China Coal Society

基　　金：国家自然科学基金委员会与神华集团有限公司联合资助项目(51174286);国家重点基础研究发展计划(973)资助项目(2013CB227903);江苏高校优势学科建设工程资助项目(地质资源与地质工程)

摘　　要：研究了采动岩体应力恢复对断裂带渗透性的影响并将其应用于分层开采和残煤复采导水断裂带的计算。通过试验对侧限作用下裂隙岩体在轴向分级加载条件下渗流变化规律进行了研究,以模拟应力恢复作用对裂隙岩体渗透性的影响;依据实测的采动裂隙岩体体积膨胀系数的对数分布规律,对采动裂隙岩体渗透性分布规律进行了描述,计算了应力恢复作用下,裂隙岩体内裂隙开度及渗透性演化规律。试验结果表明:轴向加载条件下裂隙模块开度及渗透性均显著下降,加载初期应力较小但其对裂隙模块的开度及渗透性影响更显著,后期应力增大但其对裂隙试块的渗透性影响程度降低,在20 MPa压力作用下裂隙很难完全闭合;理论计算结果表明:应力恢复作用下采空区上覆裂隙岩体内下部大开度裂隙渗透性有降低但仍为较好的导水通道,上部裂隙开度较小层段渗透性也有明显降低。根据水利水电工程地质勘查规范将渗透系数小于0.01 m/d的层段视为不透水层,采空区上覆导水断裂带最大高度在应力恢复后较初始实测最大值减小了约26%。依据研究结果对传统的分层开采覆岩导水断裂带高度计算公式进行了修正,采用修正公式计算下分层煤或残煤开采防水(砂)煤柱的留设方案更为合理。This paper presented an investigation of the influence of cover stress re-establishment on the permeability of mining-induced fractured zone and its application to the calculation of the height of water flow fractured zone for slices mining and re-mining of abandoned coal seams. An experiment on the hydraulic conductivity of the fractures under axial loading with lateral restraint was conducted to simulate influence of cover stress re-establishment on the permeability of fractured zone. Based on the in-situ measured logarithmic distribution of the bulking factor with the distance from the gob in the mining-induced fractured zone,the distribution of permeability in the water flow fractured zone has been proposed,and the evolutions of permeability and aperture of the mining-induced fractures under cover stress re-establishment were analyzed by the fractured rock mass mechanics method. The experimental results show that the apertureand the hydraulic conductivity of the fracture decrease more significantly in the earlier stage of the axial loading than that in the later stage,even though the stress is smaller; the later stage of the axial loading plays a less role on the influence of the fracture＇s permeability,and the aperture is hardly compressed to be closed under an axial loading of 20MPa. The theoretical calculation results show that the permeability of the fractures with larger aperture in the lower part of the water flow fractured zone has been decreased but still has a good permeable pathway for water flow; and the permeability of the upper part of the water flow fractured zone has been decreased obviously. According to the code for engineering geological investigation of water resources and hydropower,the hydraulic conductivity of 0. 01 m /d is determined as the standard for impermeable layer,the maximum height of the water flow fractured zone after the cover stress re-establishment is decreased by 26% compared to the original one. The formula for calculating height of water flow fractured zone is modified

关 键 词：煤层复采 裂隙 应力恢复 渗透系数 导水断裂带 

分 类 号：TD313[矿业工程—矿井建设]