盾构穿越防汛墙施工技术

上海某地铁盾构隧道穿越上海第三大河白莲泾，白莲泾防汛墙基础为钢筋混凝土方桩结构、桩基伸入隧道内，盾构通过前须处理桩基。为保证防汛安全和满足盾构穿越要求，先在防汛墙外侧施做砖结构临时防汛墙，然后拆除盾构穿越区域的防汛墙，利用船载起重机拔除影响桩基，在桩孔中灌砂并采用搅拌桩加固扰动地层，在原桩位置打入短桩代替原来的方桩，凿除上部50cm混凝土保留钢筋和基础连接形成整体结构。恢复上部墙体结构，在等强后盾构穿越。

Construction Technology for Shield Boring across Flood Control Walls

A Metro tunnel in Shanghai crosses Bailianjing River, which is the third largest river in Shanghai. The foundations of the flood control walls of Bailianjing River are of square piles made of reinforced concrete, which stretch into the tunneling scope. Before the shield crosses the flood control walls, the pile foundations must be treated. In order to ensure reliable flood control and meet the requirements of shield boring across the flood control walls, firstly, temporary flood control walls made of bricks are built outside the existing flood control walls ; secondly, the flood control walls within the tunneling scope are dismantled; thirdly, the piles that obstruct the shield boring are pulled out by ship-mounted cranes; fourthly, mortar is filled into the pile holes and the disturbed ground is consolidated by means of mixing piles; fifthly, short piles are driven at the original positions to replace the square piles and the concrete of the top 50 cm long part of the short piles are chiseled off, with the re-bars being kept so as to be connected with the foundations to form an integral structure; finally, the upper wall body is built and the shield crosses the flood control walls when the required strength is achieved.