循环围压下的盐岩扩容特征

盐穴储库运行过程中围岩应力呈周期性变化,为揭示应力波动对其稳定性和密闭性的影响,针对盐岩试样开展了动态围岩循环试验,分析了不同轴向恒定应力与循环上限围压对盐岩试样扩容及损伤特征的影响规律.结果表明:体应变曲线分为减速扩容段和稳定扩容段,试样达到稳定扩容点所用的循环数并无显著差异.上限围压越小或轴向恒定应力越大,盐岩试件扩容幅度越大,其疲劳寿命就越短,相应匀速扩容段在整个扩容过程中所占比例就越小,即加速扩容点会前移.随着试验循环数的增加,盐岩等容变形比的总体趋势不断减小,韧性特征减弱,扩容能力增强.上限围压越小或轴向恒定应力越大,都会使盐岩的韧性能力损失得更快,盐岩的扩容能力增强得更显著.

Expansion Characteristics of Salt Rock Under Cyclic Confining Pressure

The rock stress changes periodically during the operation of the salt cavern storage. The dynamic rock cyclic tests on the surrounding rock were carried out， and the influence rules of expansion and damage characteristics of salt rock samples under different axial constant stress and confining pressure cycling cap were analyzed to reveal the influence of stress fluctuations on the stability and tightness of rock. The results showed that volumetric strain curves present a decelerating expansion stage and a steady expansion stage， but there is no significant difference in the cycle’s number of times needed for reaching the stable expansion point of the sample. The smaller the confining pressure cap is or the bigger the constant axial load is， the greater the expansion margin is and the shorter the fatigue life is; the proportion of steady expansion out of uniform expansion is smaller， namely the accelerated expansion points move forward. With the increase of test cycles， the isovolumetric strain ratio becomes smaller and the toughness decreases while the expansion capability increases. The smaller the confining pressure cap is or the bigger the constant axial load is， the faster the loss of toughness capacity is and the stronger the expansion capacity of salt rock is.