应力扰动路径对煤岩力学性能的影响试验研究

Experimental study on the influence of stress disturbance path on the mechanical properties of coal specimens

在利用废弃矿井抽水蓄能过程中,煤柱不仅受到单调荷载的影响,而且会遭受频繁的应力扰动。以陕西省河畔煤矿煤岩为研究对象,研究了单调荷载(路径1)、多级等幅循环荷载(路径2)、多级增幅循环荷载(路径3)影响下试样的强度、变形特征以及破坏模式。试验结果表明:循环荷载作用下,试样的应力-应变曲线形成了明显的滞回环,且随着应力水平增加,滞回环面积显著增加;与轴向应变相比,环向应变对应力路径的敏感性更强;单调荷载作用下煤样的峰值强度和峰值应变最大,多级循环荷载作用下试样的强度和峰值轴向应变分别降低了22.12%、18.35%(路径2)、5.30%、10.34%(路径3);应力路径2作用下的试样割线模量明显高于其他应力路径;应力路径对试样宏观破坏模式的影响甚微,但多级循环荷载使得试样表面裂纹数量和尺寸变大。

During pumped energy storage using abandoned mines,coal pillars are not only affected by monotonic loads,but also suffer from frequent stress disturbances.The strength and deformation characteristics as well as the failure mode of the coal specimens under the influence of monotonic loading(stress path 1),multilevel constant-amplitude cyclic loading(stress path 2)and multilevel increasing cyclic loading(stress path 3)were studied using the coal samples from Hepan Coal Mine,Shaanxi Province,as the research object.The test results showed that the stress-strain curves of the coal specimens under cyclic loading formed obvious hysteresis loops,and the area of hysteresis loops increased significantly with the rise of stress level;compared with the axial strain,the circumstantial strain was more sensitive to the stress path;the peak strength and peak axial strain of the coal samples were the largest under monotonic loading,and the peak strength and axial strain of the specimens decreased by 22.12%and 18.35%(path 2)and 5.30%and 10.34%(path 3)under multi-level cyclic loading,respectively;the tangent modulus of the specimens under stress path 2 was significantly higher than the other stress paths;the stress paths had not changed the macroscopic failure mode of the coal specimens,but the cyclic loading caused the number and size of cracks on the specimen’s surface to become larger.