【作者】 陈海栋；

【导师】 袁亮； 程远平；

【作者基本信息】 中国矿业大学 ， 安全技术及工程， 2013， 博士

【摘要】 保护层开采及卸压瓦斯抽采是目前首选的区域性瓦斯治理措施。虽然近年来对保护层开采理论的研究取得了很大突破，然而理论研究还存在不足，目前的研究成果多偏重于宏观的现象与规律。本文运用岩石力学、卸荷岩体力学、损伤力学、渗流力学等理论，采用理论研究、实验室实验、数值模拟与工程实践相结合的方法，深入研究了保护层开采过程中被保护层卸载煤体的细观损伤与渗透性演化特征及被保护层渗透率的分布特征，最后，将研究成果应用于淮南矿区潘一矿被保护层瓦斯抽采钻孔的优化。本论文的主要研究结论如下：（1）依据被保护层煤体先经历加载而后三向应力同时被卸载的受力过程，选择固定轴向位移卸围压、固定差应力卸围压作为实验室研究的力学路径，采用离散性小且力学性质与原煤样相近的型煤试样，应用有效应力原理和等效力学路径的方法通过耦合CT实时检测实验与渗透性实验的结果分析了卸载过程中煤体损伤对渗透性的影响，同一卸载力学路径下两不同实验获得的应力-应变曲线特征的一致性验证了把CT实时检测实验与渗透性实验的结果耦合起来分析试样损伤对渗透性的影响的合理性。（2）CT检测实验结果表明，卸载初期损伤发育缓慢，随着损伤的累积，在本论文的实验条件下，从围压卸载至5MPa开始，损伤增长速度加快；试样最终破坏时内部裂纹呈锥形，且试样首先从低密度端发生破坏，进而向高密度端发展；同一试样，密度越小的层位，损伤发展越快，同时，固定差应力卸围压应力路径对试样造成的损伤更大。（3）卸载过程中渗透性实验结果表明，随着初始围压的增大，固定轴向位移卸围压与固定差应力两种卸载力学路径下，差应力减小速率增大处的围压值升高；卸载力学路径下，卸载点前加载阶段，渗透率与轴向应变的关系为k A B11e（A1、B1为拟合系数）；卸载点后卸载阶段，渗透率与轴向应变的关系为k AB2e2（A2、B2为拟合系数）。（4）推导出了用根据CT值表示的损伤变量，获得了卸载过程中损伤变量的变化，结合等效力学路径下渗透性实验的结果，获得了卸载煤体损伤对渗透性的影响，即卸载初期损伤与渗透率增加均较小，随着继续卸载，在本论文的实验条件下，两种卸载路径下有效围压均卸载至5MPa左右后，损伤和渗透率的增加速度均加快。（5）依据被保护层的膨胀变形情况与实验室获得的渗透率与轴向应变的关系，利用Matlab软件的Surf函数得出了被保护层渗透率的分布特征，即被保护层可分为原始渗透性区、渗透性减小区、渗透性增大区1、渗透性增大区2，基于此，从被保护层切眼和收作线附近区域至工作面内部，瓦斯抽采钻孔的布孔间距依次设计为5m×5m，10m×10m，40m×40m，被保护层工作面掘进、回采期间的瓦斯参数验证了瓦斯抽采钻孔布孔方式优化的合理性。更多还原

【Abstract】 In present, extraction of protective coal seam and pressure relief gas drainage is thepreferred regional gas control measures. In recent years, although the theoretical study ofmining the protective coal seam has made great breakthrough, however, there are stillinsufficient, at the same time, the current study results play more emphasis on macrophenomena and laws. By using the theory of rock mechanics, unloading rock mass mechanics,damage mechanics and fluid mechanics, together with combining theoretical research,laboratory experiments, numerical simulation and engineering research, the damage&permeability development during unloading in coal and permeability distributioncharacteristics of the protected coal seam were studied. At last, the results were applied togas drainage drilling optimization of Panyi coal mine in Huainan coalfield. The mainconclusions of this paper are as follows.(1) According to the forcing process that the coal body of protected coal seam will beloaded firstly, then unloaded with the three dimensional stress being reduced simultaneously,the fixing axial displacement with unloading confining pressure and fixing deviatoric stresswith unloading confining pressure stress paths were choosed for laboratory experiments, byusing the reconstituted coal with small discrete and similarly mechanical properties comparedto the raw coal samples, on the other hand, taking the principle of effective stress andequivalent mechanical path, the influence of damage on permeality during unloading wasstudied by coupling the results of the CT experiments and permeability experiments, also, theconsistency of stress-strain curve from two different experiments verified the method ofcoupling was feasible.(2) The CT tests denoted that the damage development was low at the initial unloadingstage; the damage growth has accelerated after the confining pressure was unloaded to5MPaunder the experimental conditions in this paper; The internal destroy cracks was invertedconeand, also, the failure occurs firstly at the low-density side, developing toword thehigh-density side; To the same sample, the smaller the density, the faster the damagedeveloped, at the same time, fixing deviatoric stress with unloading confining pressure stresspaths had greater damage to sample.(3) The permeability tests denoted that with the increases of the initial confining pressure,to the stress paths of the fixing axial displacement with unloading confining pressure andfixing deviatoric stress with unloading confining pressure, at the increasing point of thedecreasing rate about the deviatoric stress, the value of the confining pressure became bigger;The relarion between permeality and axial strain before the unloading point isk A B11e, and also, after the unloading point, the relarion isk A2eB2.(4) The damage was gotten CT values. According to the CT values during unloading, thedamage variable changes were gotten, together with the results of permeability tests under thequivalent stress path, this paper gave the influence of damage on permeability that at theinitial stage, the damage and permeability were all small, however, the increases of damageand permeability speeded with the effective confining pressure being unloaded to5MPa underthe fixing axial displacement with unloading confining pressure and fixing deviatoric stresswith unloading confining pressure stress paths.(5) According to the expansion&deformation of the protected coal seam and therelation between permeability and axial strain derived from permeability tests, thepermeability distribution characteristics was gotten by the help of Surf fution in Matlabsoftware. The permeability of protected coal seam could be divided into the originalpermeability district, permeability diminishing district, permeability increasing district1,permeability increasing district2. Based on this, from cut eye and closing to the inside of theprotected coal seam,5m×5m,10m×10m,40m×40m drilling arrangement was used. At last,the gas parameters of mining the wokface vefied the rationality about the drillingarrangement.更多还原