城市富水区钢板桩围堰施工技术

Construction technology of steel sheet pile cofferdam in urban water rich area

海关桥改造工程是拆除旧桥并在原位建新桥,由于海关桥跨越流水抚河,在抚河不断流的情况下,为了使桥梁施工在少水—无水环境中进行,使用钢板桩围堰作为基坑围护。钢板桩插打采用振动锤沉桩的方法逐片插打,自下游开始,由东向西、由南往北折返施工,拉森钢板桩插入河床线以下8m,钢板桩两头与截污箱涵连接部位采用C30混凝土做止水堵头;钢板桩围堰封闭受既有DN400mm排水管影响的位置改用钢套箱止水;围堰施工完成后,截污箱涵两端设置集水井排水,同时按要求架设I450b双拼工字钢作为钢围檩,使用A609mm,t=16mm钢支撑支护,桩基工程施工前片石回填挤淤,桩基施工完成后对基底采用水泥水玻璃双液浆压密注浆,同时对围堰内进行钢筋混凝土板施工,确保桥梁上部结构施工时基底稳定。旧海关桥下部结构的拆除及新海关桥的桩基、承台、桥墩及桥梁上部结构施工均在围堰内进行,取得较好的施工环境。得出如下结论:1)既有DN400mm排水管影响钢板桩围堰位置,因排水管迁改难度大,此位置创新性地采用钢套箱止水,使围堰实现了连续封闭止水;2)钢管支撑支护对保证围堰的整体稳定性很重要,施工此位置时,仅临时拆除与施工冲突的钢支撑,注意安全巡查,且施工完成后立即恢复钢管支撑;3)钢板桩围堰占地少、阻水小,围堰使桥梁在施工期间保障基坑内处于少水—无水状态,有利于工程进展。

The reconstruction project of the customs bridge is to demolish the old bridge and build a new bridge in situ.Since the customs bridge crosses the flowing Fuhe River,under the condition that the Fuhe River is not cut off,in order to make the bridge construction in the environment of less water and no water,the steel sheet pile cofferdam is used as the foundation pit enclosure.The steel sheet pile shall be inserted and driven piece by piece by the method of vibrating hammer driving.Starting from the downstream,the construction shall be turned back from east to west and from south to north.The Larsen steel sheet pile shall be inserted 8m below the riverbed line.C30 concrete shall be used as the water stop plug at the connection between the two ends of the steel sheet pile and the sewage interception box culvert;Steel jacketed box shall be used to seal the position affected by the existing dn400mm drainage pipe;After the completion of the cofferdam construction,water collecting wells shall be set at both ends of the sewage interception box culvert for drainage.At the same time,I450b double I-steel shall be erected as the steel purlin as required,and A609mm,t=16mm steel support shall be used.Before the construction of pile foundation,rubble shall be backfilled to squeeze silt.After the completion of pile foundation construction,cement water glass double slurry shall be used for compaction grouting of the base,and reinforced concrete slab construction shall be carried out in the cofferdam at the same time,Ensure that the base is stable during the construction of bridge superstructure.The demolition of the substructure of the old customs bridge and the construction of the pile foundation,bearing platform,pier and bridge superstructure of the new Haiguan bridge are carried out in the cofferdam to obtain a better construction environment.The conclusions are as follows:1)The existing dn400mm drainage pipe affects the position of the steel sheet pile cofferdam.Because it is difficult to relocate the drainage pipe,the steel boxed water stop is innovatively adopted in this position,so that the cofferdam can realize continuous closed water stop;2)Steel pipe support is very important to ensure the overall stability of the cofferdam.When constructing this position,only the steel support in conflict with the construction shall be temporarily removed,pay attention to safety inspection,and the steel pipe support shall be restored immediately after the construction is completed;3)The steel sheet pile cofferdam occupies less land and has small water resistance.The cofferdam ensures that the foundation pit is in a state of less water and no water during the construction of the bridge,which is conducive to the progress of the project.