特大断面隧道原位扩建的施工力学特性分析

以金鸡山特大断面隧道原位扩建工程为背景，介绍了核心五步法的原位扩挖方案，并通过数值模拟与现场监测手段，分析了特大断面隧道原位扩建的施工力学特性。结果表明:目标断面附近掌子面右上、左上部围岩开挖，以及临时竖撑拆除、仰拱回填，使得拱顶沉降显著增大。同时临时竖撑的支承作用，使得作用在衬砌拱顶与拱底处的围岩压力较集中，而先右后左的扩挖方案使得衬砌右侧围岩压力明显大于左侧。金鸡山隧道原位扩建施工过程中，对目标断面的拱顶沉降和水平收敛进行了长期跟踪监测，其结果与数值模拟较为吻合。

Analysis on Construction Mechanics Characteristics for the In-situ Expansion of Extra Large Section Tunnel

Based on the in-situ expansion project of Jinjishan extra large section tunnel, the excavation process of innovative core method is introduced and the construction mechanics characteristics for the in-situ expansion of extra large section tunnel is analyzed through numerical simulation and field monitoring. The simulation results show that the crown settlement in target section increases sharply due to the face excavation of right-upper part and left-upper part as well as the dismantling of temporary vertical support and the backfilling of inverted arch. Meanwhile, the bearing of temporary vertical support causes the concentration of contact pressure upon lining crown and lining invert. The contact pressure carried by the right half part of lining is greater than the left half part significantly due to the lateral expansion sequence from right to left. The crown settlement and the horizontal convergence of target section are monitored for a long time during the construction of in-situ expansion. The monitoring results agree with the numerical simulations generally.