冻融循环条件下片麻岩蠕变特性试验研究

Experimental study on creep characteristics of gneiss under freeze-thaw cycles

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条件下的三轴蠕变试验,分析了冻融循环作用对片麻岩蠕变特性的影响机制。试验结果表明:随着冻融次数的增加,片麻岩的蠕变变形量逐渐增加,而蠕变破坏应力、蠕变时长、长期强度均有明显降低的趋势。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,表现为冻融循环次数相同时,温度越低,岩样的初始瞬时蠕变越大,而蠕变时长与长期强度越小。同时基于试验结果,利用1st Opt优化软件对Burgers模型参数进行辨识,可得模型理论曲线与试验曲线在蠕变减速段和稳定段吻合较好。最后通过SEM扫描和能谱EDS分析了冻融循环对片麻岩微细观结构的影响机制。岩样在长期荷载作用下的破坏模式均为剪切破坏,随着冻融次数的增加,岩石的破裂程度越来越严重、破坏块度越来越小。研究结果为寒区岩石工程的支护设计和防冻害设计提供了参考和依据。

To investigate the long-term stability of surrounding rock in cold region tunnels, the gneiss in the Huibai tunnel in Jilin Province was selected for triaxial creep test under freeze-thaw cycles. The mechanism of the freeze-thaw cycle influence on the creep properties of gneiss was analyzed. The experimental results show that with increasing number of freeze-thaw cycles, the creep deformation of gneiss gradually increases, while the creep failure stress, creep duration and long-term strength have a significant decrease trend. Simultaneously, the freeze-thaw cycle temperature has a certain influence on the creep parameters of gneiss. For the same cycle number, the lower the temperature, the larger the initial creep of the rock sample, and the smaller the creep duration and the long-term strength. In addition, based on the experimental results, the parameters of the Burgers model were identified by the 1 stOpt optimization software. It performs that the theoretical curve of the model and the experimental curve agree well in the deceleration and stable creep stages. Finally, the influence mechanism of freeze-thaw cycles on the gneiss microscopic structure was analyzed by SEM scanning and energy spectrum EDS. The failure modes of rock samples under long-term load are shear failure. As the number of freeze-thaw cycles increases, the degree of rock rupture becomes more and more serious, and the rock failure block becomes smaller. The research results can provide reference and basis for the support and antifreeze design of rock engineering in cold area.