小纪汗煤样在塑性流动下力学性质试验研究

Experimental study on mechanical properties of Xiaojihan coal samples under plastic flow

为了研究小纪汗主含水煤层在采动影响下塑性流动性质和滞回特性,进行了不同围压下的轴向循环加卸载试验;当峰后轴向应力降到峰值应力的70%时开始循环加卸载轴向压缩试压,分析滞环的割线模量、宽长比及相邻滞环的轴向峰值应力比的变化规律。结果表明:随着围压的增大,轴向应变-轴向应力滞回曲线、径向应变-轴向应力滞回曲线的割线模量和宽长比增大,相邻滞环的轴向峰值应力比减小;随着循环次数的增大,轴向应变-轴向应力滞回曲线、径向应变-轴向应力滞回曲线的割线模量和宽长比减小;对于近似相同初始应力状态,围压对滞回曲线的几何特征量和塑性流动具有显著影响。

In order to study the plastic flow properties and hysteresis characteristics of Xiaojihan main water-bearing coal seam under the influence of mining,the axial cyclic loading and unloading tests under different confining pressures were carried out.When the axial stress after the peak drops to 70%of the peak stress,the cyclic loading and unloading axial compression test is started,and the secant modulus,width-length ratio of the hysteresis ring and the change law of the axial peak stress ratio of the adjacent hysteresis ring are analyzed.The results show that:with the increase of confining pressure,the secant modulus and width-length ratio of the axial strain-axial stress hysteresis curves and the hoop strain-axial stress hysteresis curve increase,while the axial peak stress ratio of the adjacent hysteretic loops decreases;with the increase of the number of cycles,the secant modulus and the width-length ratio of the axial strain-axial stress hysteresis curves and the hoop strain-axial stress hysteresis curves decrease.For approximately the same initial stress state,the confining pressure has a significant effect on the geometric characteristics of the hysteresis curve and the plastic flow.