卵砾石层浅埋公路隧道支护方案的优化研究

Optimization design of support scheme for a shallow tunnel in gravel deposits

某公路隧道位于特殊残坡积卵砾石层斜坡之中,是一典型的大跨浅埋扁平公路隧道,其支护结构和施工方案的设计直接影响到隧道的安全性和经济性。采用弹塑性非线性有限元模拟分析了该隧道的开挖和支护全过程。引入释放系数模拟开挖围岩应力释放时空效应,以最能直观反映开挖围岩松动变形情况的拱顶下沉量为主要控制目标,对初期支护的施作时机进行优化研究,利用得到的最优施作时机进行初支厚度的优化分析,并对二衬设计的合理性进行评价。提出卵砾石层斜坡中浅埋大跨扁平公路隧道支护设计和施工的优化方案。采用的考虑开挖过程的系统优化方法和研究成果可以为类似地质条件下隧道工程的设计与施工提供参考意见。

One expressway tunnel located in gravel deposits slope is shallow-buried, and of a large-span and a flat shape. Design of the support structure and the construction scheme exerts important influences on the stability and economy of the tunnel. Elasto-plastic FEM is applied to simulate the excavating and supporting process of the tunnel. The temporal and spatial effects of the excavation on the surrounding rocks are simulated with stress release coefficient. With the crown settlement, the most visually effective factor for excavation induced failure zone, as the main objective of control, optimization on the proper timing of setting up the primary support is carried out, and an optimization analysis of the thickness of primary support is performed, with the rationality of the inner lining evaluated. Moreover, the support and construction schemes for shallow, large-span flat tunnels in gravel deposits slope are presented. The systematic optimization method, with the excavation process considered, and the results can be used as reference for the construction and design of shallow large-span tunnels in similar geological conditions.