等荷载循环加卸载下砂岩变形滞回环特性

摘要

通过对砂岩试件等荷载循环加卸载试验,探究了砂岩试件的变形特性及塑性滞回环演化特征.结果表明:加载终点与卸载终点应变值均随着循环数有所增加,每一次循环均产生了一定的塑性变形,后四次循环新产生的塑性变形远小于初始循环,且随着循环数增加变形呈逐渐减少的趋势,最终试件被逐步压实,呈现出应变硬化现象.依据滞回环位置指标,发现塑性滞回环随着循环数增加逐渐右移,滞回环面积大小与应变值相关,循环加卸载终点的应变值越大,滞回环面积则越大,滞回环面积随循环数增加逐渐增大.%Through constant and cyclic loading and unloading tests on sandstone specimens, the characteristics of deformation and the plastic loop evolution of sandstone specimens are explored.The results show that the strain values in the end point of loading and unloading are increased with the increase of cycle number, a certain plastic deformation occurred in each cycle, where the later four cycles is far less than the initial cycle, and the deformation decreases gradually with the increase of the cycle number.Finally, specimens are gradually compacted, showing a strain hardening phenomenon.On the basis of the hysteresis loop position index, the plastic loop shift to the right and the areas of hysteresis loops are increased with the increase of cycle number.The area of hysteresis loop is related to the strain values, the grater the strain values in the end point of loading and unloading, the greater the area of hysteresis loop.