盐岩三轴卸荷力学特性试验研究

结合金坛地下盐穴储气库工程，以腔体围岩实际受力状态为研究依据，进行了盐岩卸围压力学特性试验，得到了盐岩卸围压过程的应力-应变关系、变形特征及其规律。试验结果表明，在卸围压初始阶段，试样的轴向和径向应变增加相对缓慢，且应变值和围压基本呈线性，随着围压继续降低，轴向与径向应变值急剧增加；卸载曲线与加载曲线相比，在最大主应力 相等的条件下，当卸载围压达到与常规三轴压缩围压相对应值时，对应的轴向和径向应变值较三轴压缩时应变值要大，表明卸荷试验能引起试样更大的变形，卸荷产生的扩容量比加载时扩容量更大，更容易导致试样变形破坏；盐岩卸围压表现为塑性变形特征，与其他硬岩卸围压属脆性破坏有较大区别。研究结果对盐穴储气库工程的稳定性评价和注采气过程具有一定的指导意义和参考价值。

Experimental research on mechanical characteristics of salt rock under triaxial unloading test

With the project of Jintan underground gas storage,taking the cavity actual bearing conditions as the object of study,carrying out unloading confining pressure test of salt rock under different conditions,the complete stress-strain curves,deformation characteristics are obtained.The test results show that axial and radial strains increase slowly in the initial stage of unloading confining pressure;and the relation between strain and confining pressure is linear.Along with the confining pressure continuous decrease,axial and radial strain values increase sharply.Comparing the loading and unloading curves,under the conditions of the same maximum principal stress,when the unloading confining pressure is the same as triaxial compression pressure value,the axial and radial strains variations are larger than that of loading conditions.Under the same initial stress conditions,the changing magnitude of stress required for rock failure is less than that of triaxial compressive process.It is shown that the plastic deformation of salt rock is different from hard rock of brittle failure under unloading confining pressure.The conclusion can be useful in underground gas storage engineering stability analysis and gas injection/extraction process.