煤系逆断层发育过程及上盘岩层应力演化规律试验研究

Experimental study on development process of reverse fault in coal measures strata and law of stress evolution in hanging wall strata

基于逆断层形成的地质及力学成因,研制了煤系地层逆断层发育地质力学试验系统,利用该试验系统研究了逆断层发育过程及上盘岩层应力变形演化规律。结果表明:该系统可模拟煤系地层中逆断层发育过程,从而更加真实地反映近断层附近煤层初始应力分布规律,设置的断层诱发装置可准确控制逆断层起裂位置,逆断层倾角主要取决于岩层性质,落差主要取决于水平应力;煤系地层中逆断层发育过程可分为岩层压缩、局部起裂、逆断层贯通和上下盘错动滑移4个阶段;逆断层形成初期,断层附近区域上盘岩层自下而上水平应力增长幅值呈现单调递减趋势,逆断层基底起裂后,岩层内部水平应力开始下降,断层附近区域上盘岩层自上而下水平应力下降幅度均增大,越靠近断层,水平应力下降速率及幅度越大,其中距模型底部5 cm岩层且距断层右侧12 cm和2 cm处水平应力较峰值降低0.05,0.08 MPa;随着断层不断发育,模型内部水平应力下降速率减缓,上下盘滑动停止后,距模型底部5 cm岩层水平应力仍比原始应力大0.01 MPa,上盘下部岩层仍具有一定程度的构造应力。

Based on the geological and mechanical causes of reverse fault development,a geomechanical test system of reverse fault development in coal measures strata has been developed.By using this system,the development process of reverse fault in coal measures strata and law of stress evolution in hanging wall strata has been studied.The experimental results have shown that the developed system can be used to simulate the development process of reverse faults in the coal measure strata,reflecting distribution of initial stress near fault more objectively.The induced device can control the fracture po-sition of the reverse faults accurately.The dip of the reverse faults depends on the properties of the stra-ta,and the fault throw depends on the horizontal stress values.The development process of reverse faults in the coal measure strata can be divided into four stages:rock stratum compression,local cracking,reverse fault coalescence and walls slippage between upper and hanging wall.In the initial period of reverse fault development process,the horizontal stress increase near the fault presents a monotonically decreasing trend from bottom to top of the hanging wall rock,in which the peaks of horizontal stress,respectively.After the basement of the reverse fault crack,the horizontal stress in the model begins to decrease,while the horizontal stress drop from the top to the bottom near the fault presents a trend of increasing.The closer to the reverse fault,the greater the rate and amplitude of horizontal stress drop.Moreover,the peaks of horizontal stress,with 5 cm to the bottom of model and 12 cm as well as 2 cm to the right side of the fault are reduced by 0.05 MPa and 0.08 MPa,respectively.The rate of horizontal stress drop begin to slow down with the continuous development of reverse fault.After the fault slippage terminates,the horizontal stress with 5 cm to the bottom of the model still remains 0.01 MPa higher than the initial stress level,with the lower strata of hanging wall still subjected to a certain of tectonic stress.