盐岩屈服后强度与变形参数演化规律及物理机制研究

The safety and stability of underground energy storage group becomes more and more severe along with its large-scale construction in China. This research project focuses on the evolution law and physical mechanism of post-yield strength and deformation parameters and for rock salt. The basic experimental tests are conducted to explore the strain hardening/softening, brittle-ductile transition,and time-dependent strength and deformation properties. The relationships between the post-yield cohesion, internal friction angle, elastic modulus, and dilation angle of rock salt under different stress states and stress paths and equivalent plastic strain and confining stress are established to illustrate the mobilization of cohesive and frictional strength, the time-dependent effect of unloading modulus, as well as the propagation mechanism of micro-cracks. Then, a new elasto-viscoplastic strain hardening/softening model for rock salt with clear expression and physical meaning is proposed using plasticity, rheology, and damage mechanics theory to take into consideration the strain hardening/softening, dilation, and the effects of low-frequency cyclic loading. The constitutive model is then implemented into the FLAC3D program and ultilized to predict the satbility of deep underground gas storage cavern. The time- and space-evolution of volume convergence and progressive failure of surrounding rock is revealed through numerical simulation. The project achievements could complete the investigation on the mechanical behaiviour of gas storage cavern and its calculation method.

随着我国盐岩地下能源储备库群大规模建设的兴起，储库安全稳定性问题也愈发突出。本课题着眼于盐岩屈服后强度与变形参数演化规律及其物理机制，开展盐岩应变硬化/软化、脆－延转化、体变扩容及强度与变形时间效应等基础物理力学特性试验研究，建立不同应力水平和不同应力路径下盐岩屈服后黏聚力、内摩擦角、弹性模量及扩容角等特征参数与等效塑性应变和围压间的联系，揭示黏结强度和摩擦强度作用机制、卸载弹模的时间效应及体变扩容的微观裂纹扩展机理；继而在塑性理论、流变力学及损伤力学理论框架内，构建一种物理意义清晰且综合考虑盐岩应变硬化/软化、扩容和低频循环荷载效应的黏弹塑性应变硬化/软化模型；基于FLAC3D二次开发平台实现新模型的软件嵌入，并运用于深部盐岩储气库稳定性数值计算，揭示低频循环内压下储库溶腔变形收敛和渐进破坏的时空演化过程。课题成果对于完善我国盐岩储气库力学特征与计算方法研究具有重大的理论意义和工程价值。

随着我国盐岩地下能源储备库群大规模建设的兴起，储库安全稳定性问题也愈发突出。本项目系统开展了盐岩屈服后强度与变形参数演化规律及其物理机制研究。基于Mohr-Coulomb剪切强度理论，提出了获取不同应力状态和应力路径下岩石屈服后强度与变形特征参数的普适方法，揭示了盐岩屈服后黏聚力、内摩擦角及扩容角与等效塑性应变和围压之间的联系，阐明了盐岩应变软化/硬化、脆－延转化的物理力学机制及体变扩容的微裂纹扩展机理，构建了非线性黏聚力弱化－内摩擦角强化模型和非线性扩容角演化模型；探讨了低频循环荷载下盐岩非线性流变力学行为，揭示了不同应力路径下盐岩非线性蠕变规律、强度与弹模的时间效应，指出了低频循环荷载作用下盐岩初始衰减、稳态等阶段性变形与定常荷载下变形的相似性，确定了盐岩循环变形破坏的上限应力阈值，给出了盐岩长期强度劣化与长期弹模折减的预测公式；继而在塑性理论、流变力学及损伤力学理论框架内，构建一种物理意义清晰且综合考虑盐岩应变硬化/软化、扩容和低频循环荷载效应的黏弹塑性应变硬化/软化模型；基于FLAC3D二次开发平台实现新模型的软件嵌入，实现了我国首个盐岩储气库（金坛）水溶建腔、注采运营至失控卸压全过程精细化数值模拟，阐明了深部含夹层地层地应力场时空演化规律，揭示了硬夹层总是先于盐岩体而屈服形成明显屈服带的现象，率先从工程尺度验证了层状盐岩Cosserat介质扩展理论，揭示了低频循环内压下储库溶腔变形收敛和渐进破坏的时空演化过程，系统建立了失控灾害模式下储库稳定性预测方法。课题成果对于完善我国盐岩储气库力学特征与计算方法研究具有重大的理论意义和工程价值。