山区高速公路隧道仰拱拆换结构变形机制

仰拱是隧道支护体系的关键构件，当运营隧道的仰拱结构因腐蚀等原因难以满足其受力要求时，就需对其进行拆换。为研究不同拆换工况下隧道结构的变形机制，本文拟通过数值计算的方法对不同拆换工况进行模拟。基于西南山区某高速公路隧道，本文使用Midas GTS NX有限元软件，建立了三维数值模型，分析了不同拆换距离、拆换顺序等因素对结构变形的影响。结果表明：（1）仰拱拆换造成隧道断面向内收缩，其中拱脚、拱顶、拱底的变形较大；（2）单次跳槽拆换的影响范围为3倍单次拆换距离；（3）应尽量选择能使新浇筑的仰拱尽早闭合成环的拆换方案，可以减小隧道因仰拱拆换产生的变形；（4）在不同的拆换距离情况下，单次拆换距离越小，隧道结构的变形就越小。在本文条件下，单次拆换距离在小于1.2D（D为隧道等效直径）时，隧道结构均处于稳定状态。研究成果可为类似工程提供借鉴和参考。

Study on Structural Deformation Mechanism of Highway Tunnel Invert in Mountainous Area During the Removal and Replacement Process

Invert is the key component of mountain highway tunnel support system. When the invert structure of operating tunnel is difficult to meet its stress requirements due to corrosion and other reasons, it needs to be removed and replaced. In order to study the deformation mechanism of tunnel structure under different dismantling and replacement conditions, numerical calculation method is used to simulate different dismantling and replacement conditions. Based on a highway tunnel in southwest mountainous area, this paper uses Midas GTS NX finite element software to establish a three-dimensional numerical model, and analyzes the influence of different dismantling distance and dismantling sequence on the structural deformation. The results show that :(1) the inverted arch replacement causes the tunnel fault to shrink inward, and the deformation of arch foot, arch roof and arch bottom is large; (2) The influence range of single job-hopping is 3 times of single job-hopping distance; (3) The demolishing and replacing scheme should be selected as far as possible to make the newly poured invert close into a ring as soon as possible, which can reduce the deformation caused by the demolishing and replacing of the tunnel; (4) In the case of different demolition distance, the smaller the single demolition distance, the smaller the deformation of tunnel structure. Under the conditions described in this paper, the tunnel structures are in a stable state when the single removal distance is less than 1.2D (D is the equivalent diameter of the tunnel). The research results can provide reference for similar projects.