盐岩在围压卸荷作用下的扩容特征研究

Study of dilatancy characteristics of salt rock under unloading action of confining pressure

通过试验模拟盐岩储气库建腔期腔体围岩围压动态降低过程,开展单轴压缩和三轴卸荷扩容试验,并分析温度对盐岩试件卸荷扩容特征的影响。试验结果表明:由于都是应力增加的过程,卸荷试验的扩容特征与常规单轴试验相比,在扩容阶段划分上具有一些共同点,都存在体积压缩段、稳定扩容段和加速扩容段。卸荷试验和单轴试验的压缩极限基本相同。但由于加载方式不同,卸荷试验的稳定扩容段在整体扩容中所占比例更小,扩容速率和扩容幅度也较单轴试验小。在相同的偏应力作用下,卸荷试验产生更大的扩容。温度升高能够促进盐岩的扩容,表现为加速扩容点前移、初始稳定扩容段缩短、加速扩容段变长、扩容速度加快、扩容幅度增大等。

The dynamic reduction of confining pressure of salt rock gas storage surrounding rock during construction period is simulated by uniaxial compression tests and triaxial unloading confining pressure tests.The effect of temperature on dilatancy characteristics of salt rock are analyzed by the unloading tests.The results show that all the tests are the process of stress increasing.Furthermore,both unloading confining pressure tests and uniaxial compression tests have similar deformation stages of dilatancy curves.The similar deformation stage includes the volume compressed segment,the stable dilatancy segment and the accelerating dilatancy segment.Those two types of tests also have the similar compressed limit.However,due to the different loading modes,the ratio of stable dilatancy in uniaxial tests is larger than that in unloading confining pressure experiments.The dilatancy rate and the value of dilatancy are smaller in unloading confining pressure tests.The unloading confining pressure tests have greater dilatancy under the same deviatoric stress.Higher temperature can promote the dilatancy of salt rock.That means the increasing of temperature can make the accelerating dilatancy point appear forward,the initial stable dilatancy segment shorter,the accelerating dilatancy segment longer,the dilatancy rate and the value of dilatancy higher.