循环荷载作用下岩石损伤变形与能量特征分析

针对不同围压作用下的岩石损伤变形与能量特征，开展了循环加卸载试验研究。基于原有损伤变量原理，进行修正，探讨了岩石在不同的偏应力量级下，每次循环的耗散能、损伤变量、塑性变形等与循环次数、应力之间的相互关系；进而，得到了岩石损伤破坏过程中能量的转化规律，从能量损耗的角度定量分析了岩石疲劳破坏的门槛值。试验研究结果表明：①应力水平越高、损伤变量与塑性变形越大，一次循环的能耗值越大，滞回圈的面积也就越大；②在门槛值前后，耗散能、损伤变量与塑性应变随着循环次数的增加变化趋势明显不同，并且在破坏前也呈疏00097;密00097;疏的发展过程；③不同的围压下，岩石疲劳破坏时所处的损伤状态不同，但破坏前循环一次的能耗值与损伤变量近似成线性关系，进而基于循环能耗值与损伤变量建立了能量破坏方程。

Energy characteristics and damage deformation of rock subjected to cyclic loading

According to the damage deformation and energy characteristics of rock element under different confining pressures, a series of tests on rock subjected to cyclic loading and unloading are carried out. Based on the current rationale of damage, the damage variable is revised. On this basis, the relationship among the dissipated energy, damage variable, plastic strain and cycle index under different stress levels is explored, and likewise the energy transformation rule of rock in the process of fatigue damage is obtained. Meanwhile, the threshold value of fatigue damage is analyzed quantitatively. The results indicate that the hysteresis loop area and dissipated energy will enlarge if the stress level rises, and the same happens on the condition that the damage variable and plastic strain rise. Above and below the threshold value, it is shown that the variation trends of the dissipated energy, damage variable and plastic strain are markedly different along with the increase of cycle index, and they exhibit the sparse-dense-sparse development process. The fatigue damage states are different under different confining pressures, however, there is a significant linear correlation between the dissipated energy and damage variable before destruction. An equation for energy is proposed based on the analysis of the dissipated energy and damage variable.