三轴加卸载条件下深部盐穴工程盐岩的声发射特征及能量演化

Acoustic emission characteristics and energy evolution of salt rock for deep-salt-cavern engineering under triaxial loading and unloading

深部盐岩储气库在运行过程中受到周期性高应力载荷。为探索深部盐岩在三轴循环加卸载下的损伤和变形特征,采用MTS815岩石力学测试系统和声发射(AE)信号采集系统,分析了围压和加卸载对盐岩声发射特征和能量演化的影响。结果表明:1)当围压从10 MPa增加到30 MPa时,压实阶段的累积声发射计数减少了86%。Kaiser效应在峰值应力点之前明显,Felicity比与循环次数呈负相关;2)随着偏应力的增加,弹性能(Ue)和耗散能(Ud)的增长率逐渐增加。在相同偏应力下,高围压试样在达到相同应力时的变形和耗散能越小;3)Ue和Ud在实验期间均呈现两阶段增长趋势;在相同应变水平下,随着围压的增加,Ue和Ud呈MnMolecular函数增加,且围压效应增强;在考虑围压的情况下,建立了加卸载过程中声发射计数与Ud的耦合方程。研究结果对深盐穴储气库的安全运行具有一定指导意义。

Deep salt cavern gas storage is subjected to periodic high stress load during operation.To explore the damage and deformation characteristics of salt rock under triaxial cyclic loading and unloading,the MTS815 rock mechanics test system and acoustic emission(AE)signal acquisition system were used,and the effects of confining pressure and loading and unloading on the characteristics of AE and energy evolution of the whole cycle were analyzed.The results showed that:1)as the confining pressure increased from 10 MPa to 30 MPa,the cumulative AE counts in the compaction stage decreased by 86%.Kaiser effect was obvious before the peak stress point,and the Felicity ratio was negatively correlated with the number of cycles;2)With the increase of deviatoric stress,the growth rate of elastic energy(U e)and dissipated energy(U d)increased gradually.Under the same deviatoric stress,the deformation and dissipation energy of high confining pressure specimen were smaller,when it reached the same stress;3)Both U e and U d showed two-stage growth trend during the test.At the same strain level,with the increase of confining pressure U e and U d increased as MnMolecular function,when the confining pressure effect strengthened.Considering the confining pressure,the coupling equation of AE ringing count and U d during loading and unloading was established and verified.It has certain guiding significance for the safe operation of deep salt cavern gas storage.