岩盐椭球储气库应力解析及其稳定性分析

Stress Solutions and Stability Analysis of Ellipsoidal Gas Storage Cavern in Salt Rock

岩盐地下储气库根据成腔方式不同,储气库形状也有较大变化,但简化为细长旋转椭球体(短长轴比s)是合理的.假定岩盐体为无限大各向同性线弹性体,将旋转椭球岩盐储气库受力分解为两种受力状态:有内压的静水压力状态和无内压的非静水压力状态.利用弹性理论应力叠加原理,求得了在地应力场(垂直p,水平p0)和内压(pi)作用下储气库腔壁上关键点(顶点和赤道线上任意点)的应力精确解析解.对某岩盐储气库进行了数值模拟计算,数值计算结果与解析解较接近.分析了关键点应力随椭球腔形状、地应力和内压的变化规律,认为径向应力随内压比(pi/p)的增加而增加,几乎与轴比(s)无关;水平环向应力随内压比和轴比的增加而减小.结合已有试验资料,确定了盐岩广义Hoek-Brown破坏模型参数,并据此计算得到了储气库不出现破坏时的极限内压值范围,当s=0.9时极限内压较小.

The shapes of the gas storage caverns vary with building ways, but simplified as an elongated rotational ellipsoid （ minor to major axis ratio, s ） is reasonable. Assumed that the ellipsoidal cavity is in linear elasticity and isotropy infinite body, the mechanical status of the caverns can be resolved into：hydrostatic pressure with internal pressure and non-hydrostatic pressure without internal pressure. Using principle of superposition on stress in elastic theory, the exact stress solutions for the key points, which are the peak and an arbitrary point on the equator line of the ellipsoidal cavity, were solved under geostress field （vertical stress, p; horizontal stress,p0 ）and internal pressure（pi ）. The numerical simulation analysis on rotational ellipsoidal gas storage cavern in salt rock was conducted, and the results of numerical simulation coincided with analytic solutions. Analyzed the laws of the stresses of the key points varying with shape of cavity, geostresses and internal pressure, the results showed that the radial stress concentration factors increased with the internal pressure ratio（pi/p）and nearly independent of axial ratio（s）, and the horizontal circumferential stress concentration factor decreased with the increase of the internal pressure ratio （pi/p）or axial ratio （s）. According to the pre-existing test data of salt rock,the parameters in generalized Hoek-Brown failure criterion were determined. Based on the failure criterion,the limit of internal pressure（pi）to estimate stability of the ellipsoidal caverns was obtained,and limit internal pressure had the smaller value when s equals 0.9.