循环载荷下煤裂隙演化试验研究

Experimental study on crack evolution of coal under cyclic loading

为了研究循环载荷下的煤体裂隙演化特征,在不同应力水平和不同频率条件下分别进行煤样破坏力学及声发射试验。结果表明:应力-应变曲线呈疏-密-疏的变化特征,对应的振铃数柱状图呈U型;上限应力点的应变值、累积能量、撞击计数均随循环次数增加而上升,曲线呈倒S型;煤裂隙演化经历了原始裂隙闭合、新生裂隙稳定发育和裂纹贯穿破坏等3个不同阶段;循环载荷的应力水平和加载频率对煤体疲劳寿命的影响具有差异性,对煤体裂隙演化和破坏模式均有明显影响。

In order to study the crack evolution characteristics of coal under the cyclic loading,the mechanics and acoustic emission experiments of coal samples failure were carried out under different stress levels and different frequencies respectively.The results showed that the stress-strain curves showed the changing characteristics of sparse-dense-sparse,and the corresponding histograms of ringing count were the"U"type.The strain values of the upper limit stress points,the accumulated energy and the impact count were all rising with the increase of cycling times,and the curves were the reverse"S"type.The crack evolution of coal went through three different stages:the closure of the original crack,the stable development of the new crack and the penetrated failure of crack.The stress level and loading frequency of the cyclic loading had different effect on the fatigue life of coal,and had obvious effect on the crack evolution and failure mode of coal.