内河沉管隧道岸上接口段设计与施工

Design and Construction of Connection Section between Land Section and Underwater Section of Inland Immersed Tunnel

为解决南昌红谷隧道高水位差条件下岸上暗埋段与沉管段连接处(接口段)挡水,顺利完成前期接口段的施工以及后续沉管浮运前接口段的拆除问题,综合考虑工程施工的安全性、可靠性及经济性,选用大型充砂长管袋围堰及防渗墙作为岸壁保护结构,钢管桩、旋喷桩和搅拌桩的组合形式作为围护结构。对常规水上拆除接口段方案进行优化,研究出干拆除堰内基坑堵头钢管桩、陆上进行管节基槽开挖以及对接范围内围堰陆上同步拆除等关键施工技术。施工效果表明:充砂长管袋围堰及防渗墙的组合止水效果好,陆上拆除接口段钢管桩、管节基槽及长管袋围堰质量有保证,作业安全可靠,接口段拆除工期缩短约31%,拆除成本降低约26%,取得了较好的应用效果,可为类似沉管隧道工程提供参考。

In consideration of safety, reliability and economy of construction, large-scale sandbag cofferdam and anti- seepage wall are selected as soil retaining system of Honggu Immersed Tunnel; and the steel pipe pile, jet grouting pile and mixing pile are used as retaining structures, so as to guarantee the water retaining effect of connection section between mined section and immersed section of Honggu Immersed Tunnel in Nanchang under large water-head difference condition, successfully finish preliminary construction of the connection section and dismantle the connection section before segment floating and transportation. Key technologies, drying out method for steel tube plug pile in foundation pit, overland foundation trench excavation and overland cofferdam dismantling synchronously, are adopted by optimizing conventional construction scheme. The construction results show that the composite structure of sandbag cofferdam and anti-seepage wall has a good water retaining effect; the quality of dismantling of steel pipe pile, segment foundation trench and sandbag cofferdam has been guaranteed; the construction period has been reduced by 31% and the structure dismantling cost has been reduced by 26%. The results can provide reference for similar projects in the future.