既有河道桥处实施地道分析研究

Analysis and Study on Tunnel Construction at Existing River Bridge

摘要:

江浙软土地基区主干路下穿地道工程会遇到附近河道的既有桥梁问题，重点探讨了地道与某既有桥梁桩基冲突的解决方案。工程面临保通要求高、需利用既有合格桥梁、减小周边影响等多重挑战。研究论证了地道分幅绕行、拆除部分老桥实现桥隧共建、地道分幅穿桥以及拆桥改建箱涵四种方案。经综合比选，拆除部分老桥实现桥隧共建方案以其对周边少影响、可利用保留桥幅保通、造价适中等优势被推荐。该方案将新建桥梁墩柱设置于地道顶板上，形成“上桥下隧”的复合结构，通过桩基与地基加固组合控制沉降。在既有桥梁下建设隧道时，桥隧共建模式能高效集成交通、行洪与地下空间功能，对既有桥梁下实施隧道工程具有重要参考价值。

Abstract:

The tunnel project of the main road in the soft soil foundation area of Jiangsu and Zhejiang will encounter the problem of existing bridges in nearby rivers. The solutions to the conflict between a tunnel and an existing bridge pile foundation are discussed in detail. The project faces the multiple challenges, including the high requirements of traffic maintenance, the need to utilize the existing qualified bridges, and the reduction of surrounding influence. Four schemes are studied and demonstrated that is the detour of the tunnel in sections, the demolition of part of the old bridge to achieve the co-construction of the bridge and tunnel, the passage of the tunnel in sections through the bridge, and the demolition of the bridge to rebuild the box culvert. Through comprehensive comparison, the scheme of demolishing part of the old bridge to achieve bridge-tunnel co-construction is recommended due to its advantages such as less impact on the surrounding area, the ability to retain the bridge span for traffic maintenance, and moderate cost. In this scheme, the newly built bridge piers are set up on the tunnel roof to form a composite structure of “bridge above and tunnel below”. The settlement is controlled by combining pile foundation and subgrade reinforcement. When building tunnels under existing bridges, the bridge-tunnel co-construction model can efficiently integrate the functions of traffic, flood discharge and underground space, and has important reference value for the implementation of tunnel projects under existing bridges.