基于核磁共振的冻融片麻岩蠕变特性试验研究

Experimental study on creep properties of freeze-thawed gneiss based on nuclear magnetic resonance

为探讨寒冷地区隧道围岩的长期稳定性,选取吉林省辉白隧道中的片麻岩进行冻融循环后三轴蠕变试验,分析讨论了冻融循环作用对片麻岩蠕变特性的影响机制。并对不同冻融循环后的同一岩样进行核磁共振(NMR)检测,得到同一岩样不同冻融循环次数后的横向弛豫时间T2分布。试验结果表明:随着冻融次数的增加,岩样经历的蠕变时长缩短,承受的加载等级逐渐减少。同时冻融循环温度的幅度对片麻岩的各蠕变参数也有一定影响,冻融后片麻岩在长期荷载作用下的破坏模式为剪切破坏,随着冻融次数的增加,岩石的破裂程度越来越严重。本文研究结果对于寒区工程的全寿命周期评价具有参考意义。

In order to investigate the long-term stability of surrounding rock in tunnels in cold regions,the gneiss in the Huibai tunnel in Jilin Province is selected for the triaxial creep test after freeze-thaw(F-T)cycles.The influence mechanism of F-Tcycles on the creep properties of gneiss is analyzed and discussed.Besides,nuclear magnetic resonance(NMR)measurements are carried out and the transverse relaxation time T2distribution is obtained for the same rock sample after different F-T cycles.The results show that as the number of F-Tcycles increases,the creep length experienced by the rock sample is shortened,and the loading level is gradually reduced.At the same time,the temperature range of F-T cycle also has some influence on the creep parameters of gneiss.The damage mode of gneiss under long-term load after F-Tcycles is shear failure.With the increase of F-Tcycles,the degree of rock rupture becomes more and more serious.The research results provide valuable guidance for the life cycle assessment of cold area projects.