公路隧道炭质板岩变形规律及蠕变特性研究

Analysis of deformation law and creep characteristics of carbonaceous slate in highway tunnel

针对深部高应力下大跨度隧道围岩大变形问题,开展了大变形支护方法、围岩变形测量和围岩蠕变特性实验研究工作.首先在木寨岭隧道选择相似地质区段,提出采用恒阻大变形锚网索(Negative Poisson’s Ratio,简称NPR锚索)支护方案对隧道围岩进行支护;然后,试验段内每隔5 m设置1个监测断面,每个断面设置5个测点,对围岩变形量进行连续测量;接着,通过两种方案施作条件下围岩变形量的对比分析,判断NPR支护方法的可行性;最后,建立木寨岭隧道典型炭质板岩的Burgers蠕变模型,通过"室内蠕变实验解"和"Burgers蠕变模型解析解"的对比分析,判断蠕变模型的科学性.现场试验结果表明:木寨岭隧道采用NPR锚网索耦合支护后,围岩最大变形量有效控制在350 mm以内,无破坏现象.蠕变实验解和理论解析解显示两个结果具有较高的拟合度,进而研究了木寨岭隧道薄层炭质板岩蠕变特征与板岩层理角度及含水率的关系,得到在不同含水率条件下炭质板岩蠕变规律方程.

In order to solve the problem of large deformation of surrounding rock in deep long-span tunnel under high stress, the supporting method of large deformation, the measurement of surrounding rock deformation and the experimental research on creep characteristics of surrounding rock were emphatically carried out. Firstly, the similar geological section was selected in Muzhailing tunnel, and the support scheme of NPR(Negative Poisson’s Ratio) was proposed to support the surrounding rock of the tunnel. Then, one monitoring section was set every 5 m in the test section, and five measuring points were set in each section to measure the surrounding rock deformation continuously. After that, the feasibility of NPR support method was judged by comparing the deformation of surrounding rock under the two support schemes. Finally, Burgers creep model of carbonaceous slate in Muzhailing tunnel was established. The scientificity of creep model was judged by comparing laboratory creep experimental solution and Burgers creep model analytical solution. The field test results show that the maximum deformation of surrounding rock is effectively controlled within 350 mm and there is no damage phenomenon with using NPR anchor mesh cable coupling support in Muzhailing tunnel. Because the experimental results and theoretical analysis have a high degree of fitting, the relationship between the creep characteristics of thin carbonaceous slate in Muzhailing tunnel and the bedding angle of slate and water content was further studied. The creep law equation of carbonaceous slate under different water content was obtained.