小相岭隧道围岩力学状态测试及大变形成因分析

为解决小相岭隧道平导和正洞的围岩大变形问题，采用现场试验的方法对围岩力学状态进行测试，基于实测数据对隧道大变形成因进行分析并提出针对性控制治理对策。结果表明： 1）隧道围岩强度偏低且存在明显的各向异性，初始地应力以水平应力为主，属极高地应力；现场实测结果显示底板处围岩损伤范围明显大于边墙处，推断隧道大变形为底隆变形，这与现场结构变形特征相符。2）隧道大变形的主要原因是下伏缓倾层状软弱岩层、高水平地应力、支护结构不对称等因素，尤其是平导底板的不对称结构对抵抗底隆变形能力较弱。3）在采取平导设置仰拱、正洞打设长锚杆、增大预留变形量、提升结构的刚度及强度等措施后，隧道变形得到了有效控制。

Analysis of Large Deformation of Xiaoxiangling Tunnel Based on Mechanical State Test of Surrounding Rock

In order to solve the problem of large deformation of surrounding rock in the parallel heading and main tunnel of Xiaoxiangling tunnel, the mechanical state of the surrounding rock is measured by field test. Based on the obtained data, the causes for tunnel large deformation are analyzed and the targeted control countermeasures are put forward. The results show that: (1) The strength of tunnel surrounding rock is low, and it is obviously anisotropic. The initial geostress is dominated by horizontal stress. It belongs to extremely high geostress. Based on field test results, the damage range of the surrounding rock at the bottom is significantly larger than that at the side. It is inferred to be bottom uplift deformation, which is consistent with the deformation characteristics of the structure in the field. (2) The main reasons for the large deformation are the underlying gently dipping layered weak rock formation, high level in situ stress, asymmetry of the structure, and other factors. Especially the asymmetric structure of the parallel heading floor is weak against bottom uplift deformation. (3) The surrounding rock deformation of tunnel is effectively controlled by setting inverted arch in parallel heading tunnel and long anchor bolts in main tunnel, increasing reserved deformation and improving rigidity and strength of the structure.