盐岩三轴蠕变与损伤恢复变形特征研究

地下盐岩储气库建设在我国能源储备战略中具有重要的地位,盐岩蠕变特性对地下盐岩储气库长期安全运行具有重要意义。为研究长期荷载作用下盐岩蠕变变形与损伤恢复特征,进行了不同围压、定偏应力的三轴蠕变及损伤恢复试验,损伤恢复时长超过150 d。研究结果表明:(1)高偏应力作用下,盐岩试样出现了明显的蠕变变形,轴向变形在30~40 d达到7%,体积变形先压缩后发生扩容;(2)低偏应力作用下,盐岩轴向蠕变变形量较小,体积变形持续压缩并趋于稳定;盐岩体积应变增幅随围压增大而逐渐增大,损伤恢复阶段试验达到150 d时,围压10、15、20、25 MPa对应体积应变分别相对增大1.06%、1.31%、1.30%及1.42%,盐岩体积应变增幅与围压之间呈正线性相关;(3)根据盐岩损伤恢复过程中体积变化特征及盐岩体积变形速率曲线,将盐岩损伤恢复划分为损伤快速恢复与损伤缓慢恢复两个阶段;盐岩损伤恢复主要发生在损伤快速恢复阶段,该阶段的体积增幅均达到全恢复过程的80%以上。

Deformation Characteristics Investigation on Triaxial Creep and Damage Healing of Salt Rock

The construction of underground salt rock gas storage plays an important role in China's energy reserve strategy. The creep characteristics of salt rock are of great significance to the long-term safe operation of underground salt rock gas storage. In order to study the characteristics of creep deformation and damage recovery of salt rock under long-term load, triaxial creep and damage heal tests under different confining pressure and constant deviator stress were carried out, and the self-healing tests lasted more than 150 days. The results show that: (1) under the action of high deviator stress, the salt rock samples show obvious creep deformation, and the axial deformation reaches 7% in 30-40 days, and the volume deformation first compresses and then expands. (2) Under the action of low deviator stress, the axial creep deformation of salt rock is small, and the volume deformation continues to compress and tend to be stable. The volume stress of salt rock increases with the confining pressure increase. When the damage recovery period reaches 150 days, the volume strain of salt rock increases by 1.06%, 1.30%, 1.30% and 1.42% respectively, and there is a positive linear correlation between the volume strain of salt rock and the confining pressure. (3) According to the volume change characteristics and the volume deformation rate curve of salt rock in the process of salt rock damage recovery, the salt rock damage recovery can be divided into two stages: rapid damage recovery and slow damage recovery. The recovery of salt rock damage mainly occurs in the stage of rapid recovery of damage, during which the volume increase of salt rock sample ocupies more than 80% of the whole recovery process.