不连续周期荷载作用下砂岩力学特性试验研究

Experimental study on mechanical properties of sandstone under discontinuous cyclic loading

为探究砂岩在不连续周期荷载作用下的力学特性,基于周期荷载作用下岩石的损伤特性,开展普通周期荷载试验中加入时间间隔的疲劳试验。试验结果表明:普通周期荷载试验中,随着循环次数的增加,岩石的轴向残余应变逐步趋于稳定值;在时间间隔的影响下,设置时间间隔后的轴向残余应变始终大于未设置时间间隔时的残余应变;时间间隔越长残余应变累加得越快,砂岩的疲劳寿命越小;砂岩的疲劳破坏是不同时间间隔条件下由内部微裂纹压密、闭合、张开、扩展等作用下的宏观表现,时间间隔使残余应力在砂岩内部持续产生作用,时间间隔越长作用效果越明显。

In order to explore the mechanical properties of sandstone under discontinuous cyclic loading,based on the damage characteristics of rock under cyclic loading,fatigue tests with time intervals were carried out in ordinary cyclic loading tests.The results show that the axial residual strain of rock tends to be stable gradually with the increase of cyclic times in ordinary cyclic load test;The longer the time interval,the faster the residual strain accumulates,and the smaller the fatigue life of sandstone.The fatigue failure of sandstone is the macroscopic performance under the action of internal micro-crack compaction,closure,opening and expansion under different time intervals.The time interval makes residual stress continue to act in sandstone,and the longer the time interval,the more obvious the effect.