针对不同的实际工程，开展不同应力路径的试验来研究岩体的力学特性是解决实际问题的关键。为研究粉砂岩在围压循环卸-加载特殊应力路径下的力学特征，采用MTS815岩石力学测试系统开展不同轴力水平下分级循环卸-加载围压试验，研究不同轴力水平下轴、环向塑性应变及弹性模量的演化特征，并结合耗散能量的计算，分析能量演化与试件变形破坏之间的关系。结果表明：随着循环次数的增加，滞回环向应变增大方向移动，卸-加围压下应力-应变曲线逐渐闭合，滞回环间距整体表现为由“疏”到“密”的变化特征；单一变量时，围压卸载等级越低弹性模量越低，轴力水平越低弹性模量越高，弹性模量受轴力水平和围压卸载等级两种参量共同作用；单次循环中环向塑性应变在数值上总是大于对应的轴向塑性应变，循环卸-加围压特殊应力路径下，高轴力水平下岩石抵抗塑性变形的能力要强于低轴力水平；岩石破坏最终所耗散的总能量与轴力水平一定程度上呈线性正相关。

For engineering practice, conducting experiments with different stress paths to study the mechanical characteristics of rock masses is essential. In order to study the mechanical characteristics of siltstone under the special stress path of cyclic unloading-loading of confining pressure, the MTS815 rock mechanics testing system was used to conduct staged cyclic unloading-loading confining pressure tests at different axial force levels, and the evolution characteristics of axial and circumferential plastic strain and elastic modulus at different stress levels were analyzed. The relationship between the energy evolution and the deformation as well as the damage of the specimens was also analyzed via calculation of dissipated energy. The results show that the hysteresis loops move in the direction of strain increase as the number of cycles increases, and the stress-strain curves of unloading-loading confining pressure gradually close, and the overall change of hysteresis loop spacing is from “sparse” to “dense”. The lower the unloading level is, the lower the modulus of elasticity is, while the lower the stress level is, the higher the modulus of elasticity is. Modulus of elasticity is affected by both the axial force level and the unloading level; the circumferential plastic strain is generally larger than the axial value in a single cycle, and the resistance to plastic deformation at high axial force levels is stronger than that at low force levels under the special stress path; the total energy dissipated in the final damage of the rock is positively correlated with the axial force level to some extent.

TU452

国家自然科学基金(51974014、51574014)