三轴循环加卸载过程中盐岩声发射演化特征分析

Characteristic Analysis on Rock Salt Account Emission Evaluation in the Triaxial Loading and Unloading Process

为探究盐岩储气库运行过程中的声发射特征,对取自平顶山岩穴一号钻孔的盐岩进行不同围压作用下的三轴循环加卸载试验及全过程声发射监测试验。试验研究表明:围压施加过程中,声发射信号主要出现在围压施加前期,声发射振铃计数率和能量率的最大值出现在围压压力5~10 MPa的时间区段,且振铃计数率和能量率达到最大以后,声发射信号随着围压的增大逐渐减弱;围压越低,试验加载初期产生的声发射信号越强,整个试验过程中累积振铃计数越多,能量率和能量越高;围压会使试验过程中声发射信号后移,且围压越大,后移现象越明显;围压的增大会使得盐岩加载过程中的平静期缩短和后移,直至平静期的消失;考虑三轴加卸载过程,加载段有明显的声发射信号,卸载段鲜有声发射信号,偏应力峰值前有明显的Kaiser现象,峰值后伴随大量的声发射信号,但Kaiser现象消失。

To explore the characteristics of acoustic emission of the running rock salt gas storage,a series of triaxial loading and unloading experiments are carried out on the salt rock samples from Pingdingshan under different confining pressures,and the account emission is detected at the same time.From these tests,conclusions are drawn as below.Acoustic emission signals mainly appear in the early stage of the confining pressure applying process,and the peaks of ringing count rate and energy rate both appear when the confining pressures are during 5 ~ 10 MPa,and the two rates decline after their own peak,and they decline more when the confining pressure higher.In addition,the lower the confining pressure is,the stronger the acoustic emission signals will be in the early axial loading stage and the more AE count and energy in sum in the whole process.What＇s more,Acoustic emission signals delay under the higher confining pressure,and the phenomenon get more obvious when the confining pressure is higher.Moreover,with the increase of the confining pressure,the quiet period will get short and backward,until the quiet period disappears.From the point of the whole loading and unloading process,the acoustic emission signals are weak in the unloading process,not as strong as the loading process,and the Kaiser effect is obvious before the peak of deviator stress,which disappears after the peak.