泥砂组合岩体预制裂隙扩展规律室内压缩试验研究

Experimental study on fracture propagation law of precast rock mass of combined rock mass

针对煤层开采断层构造在顶底板不同岩层中的发育问题,以含预制三维裂隙的泥砂组合岩体为研究对象,采用单轴压缩、三轴压缩试验并结合声发射监测的方法对泥砂组合岩体裂纹扩展演化规律展开研究。试验结果表明:3种岩体的峰前应力-应变曲线较为相似,泥砂组合岩体由于裂隙在穿层传播时发生变化,上部和下部岩体破坏不一致,峰后呈现不同形态;三轴加载下泥砂组合岩体峰值强度的均值分布为16~18 MPa,且在声发射监测中,泥砂组合岩体预制中部裂隙位置声发射活动较多,破坏后振幅达到最大值,基本在70 dB以上,随后声发射活动骤减,振幅降至60 dB以下;当含预制裂隙的泥岩或砂岩达到极限时,裂纹进行穿层传播,进而引发新一轮的声发射活动;当预制裂隙在泥砂组合岩体分界位置时,预制裂隙已提前突破了穿层阻力,会引导裂纹向两方向传播;泥砂组合岩体上部和下部裂隙位置岩样的声发射峰值振铃计数和峰值振幅均小于泥砂组合岩体中部裂隙位置岩样,泥砂组合岩体中部位置裂隙的存在使岩体结构面破坏,受力更容易发生变形破坏。研究成果为煤炭开采断层构造活化、穿层诱发的灾害防治研究提供新思路。

In order to solve the problem of the development of coal seam mining fault structure in different rock layers of the roof and floor,the mud-sand composite rock mass with prefabricated three-dimensional fractures was taken as the research object,and the crack propagation and evolution law of the mud-sand composite rock mass was studied by uniaxial compression and triaxial compression tests combined with the method of acoustic emission monitoring.The test results show that the pre-peak stress-strain curves of the three rock masses were relatively similar,and the mud-sand composite rock mass changes due to the change of fractures during the propagation of the layer,and the failure of the upper and lower rock masses was inconsistented,and the post-peak rock mass presents different shapes.The average distribution of the peak intensity of the mud-sand composite rock mass under triaxial loading was 16-18 MPa,and in the acoustic emission monitoring,there were more acoustic emission activities at the fracture position in the middle of the precast mud-sand composite rock mass,and the amplitude reaches the maximum value after failure,which was basically above 70 dB,and then the acoustic emission activity decreases sharply,and the amplitude drops to less than 60 dB.When the mudstone or sandstone with prefabricated fractures reaches the limit,the cracks propagate through the layer,which in turn triggers a new round of acoustic emission activities.When the prefabricated fracture was at the boundary position of the sediment composite rock mass,the prefabricated fracture had broken through the penetration resistance in advance,which will guide the crack to propagate in both directions.The peak acoustic emission ringing count and peak amplitude of the rock samples at the fracture location in the upper and lower parts of the mud-sand composite rock mass were smaller than those in the rock samples at the fracture location in the middle of the mud-sand composite rock mass,and the existence of the fracture in the middle of the mud-sand composite rock mass makes the rock mass structural plane fail,and the deformation and failure are more likely to occur under stress.The research results provide new ideas for the research on the prevention and control of disasters induced by fault tectonic activation and through-bed in coal mining.