适用于多夹层盐穴储气库的改进Mohr-Coulomb准则

Improved Mohr-Coulomb criterion applicable to gas storage caverns in multi-laminated salt stratum

考虑到多夹层盐岩在三轴压缩和拉伸应力状态下破坏强度的差别较大,对盐岩破坏的Mohr-Coulomb准则进行修正,得到改进后的Mohr-Coulomb准则,利用室内盐岩实验数据回归出相应的公式,并与已有的两种准则的计算结果进行对比。建立了多夹层盐穴储气库有限元模型,分析了储气库的埋深、顶跨、顶部盐岩厚度、顶部相邻非盐岩层厚度及弹性模量等参数对储气库最小许可运行压力的影响规律,并对比了改进Mohr-Coulomb准则与已有准则的计算结果。综合研究表明:改进Mohr-Coulomb准则与实验数据具有很好的一致性,能够反映盐岩从三轴压缩应力状态转换为三轴拉伸应力状态时破坏强度变化对储气库最小许可运行压力的影响;储气库最小许可运行压力梯度随着顶跨的增加而增加,随着顶部相邻非盐岩层弹性模量的增加而降低,而顶部盐岩和相邻非盐岩厚度对其影响不显著。

The present paper modified and improved the traditional Mohr-Coulomb salt dilation criterion in view of big differences in the failure strength of multi-laminated salt caverns under triaxial compression and extension stress conditions.A comparison of the equation regressed correspondingly by indoor experimental data of salt rocks with the result calculated by the two existing criteria was made and a finite element model for gas storage in multi-laminated salt caverns was built up.Influences of various parameters,such as burial depth and roof span of salt caverns,thickness of roof salt rocks,and thickness and elastic modulus of adjacent roof non-salt rocks,etc.,on the minimum operating pressure of gas storage were dealt with and the result calculated by the improved Mohr-Coulomb criterion was compared with that obtained by the existing criteria.Comprehensive studies showed that the improved Mohr-Coulomb criterion was well consistent with the experimental data,reflecting the influence exerted by the yield strength change in the conversion from the triaxial compression stress to triaxial extension stress in multi-laminated salt caverns on the minimum operating pressure of gas storage.The minimum operating gas pressure gradient increased with increasing roof span of salt caverns,but decreased with increasing the elastic modulus of adjacent roof non-salt rocks,moreover,it was influenced little by the thickness of roof salt rocks or adjacent roof non-salt rocks.