汕头市苏埃通道南岸明挖隧道位于海域围堰内,围堰内上软下硬的特殊地层给地下连续墙施工过程中的泥浆护壁、成槽造成极大的困扰.地下连续墙成槽施工前期主要采用"抓—冲结合"成槽工艺;在淤泥层、砂层、全风化岩层采用液压抓斗成槽机直接成槽;在强风化、中风化、微风化岩层采用冲击钻机冲孔、修槽成孔工艺.单元槽段成槽时一般完成1个槽段需要20d以上,最长1个槽段达40d,严重影响工期进度.为了改变地下连续墙施工状况,结合类似工程实践经验,在旋挖钻的基础上进行改造,将钻头设计为牙轮钻钻头,对强、中风化岩层钻孔取芯,通过组合使用"成槽机+冲击锤+旋挖钻(牙轮钻)"后,实现了地下连续墙施工效率的极大提升.经过成槽施工方案比选、入岩墙深设计优化、孤石破碎和基岩处理工艺探讨,顺利完成了该基坑工程,积累了在该类上部淤泥下部基岩地层中地下连续墙施工的经验.%The tunnel of the southern side of Suai Passage in Shantou constructed by open cut method is located in sea cofferdam area. The special characteristics of upper-soft lower-hard strata of the cofferdam cause great difficult for slurry protection of the trench wall and trenching of the underground diaphragm wall. The trench cutting technology of"soil clawed by trench cutting machine + impact drill"is adopted at the early stage of trench cutting of underground diaphragm wall;the hydraulic claw bucket is adopted for the trench cutting in mucky soil,sandy soil and fully weathered rock;and the compact drill is adopted for hole drilling and correcting in strongly weathered rock,moderately weathered rock and slightly weathered rock. It takes more than 20 days to complete a single trench section,and the longest time is up to 40 days,which severely affects the construction schedule. The construction efficiency of underground diaphragm wall has been remarkably improved by modifying drill bit of rotary drill, core drilling of strongly weathered and moderately weathered rock and adopting trench cutting machine, compact hammer and rotary drill. Through comparing and selecting of trench cutting scheme, design optimizing of in-rock wall thickness, boulder breaking and bedrock treating, the foundation pit is completed successfully, which accumulates construction experience for underground diaphragm wall in upper-soft lower-hard strata.
展开▼
