公安长江公铁两用特大桥4号墩基础施工关键技术  

Key Techniques for Construction of Foundation of Pier No.4 of Gong′an Changjiang River Rail-cum-Road Bridge

作　　者：房保华 

机构地区：[1]蒙西华中铁路股份有限公司湖北指挥部,湖北襄阳441021

出　　处：《桥梁建设》2015年第3期1-6,共6页Bridge Construction

摘　　要：公安长江公铁两用特大桥主桥为(98+182+518+182+98)m双塔钢桁梁斜拉桥,该桥4号主墩采用2.8m/3.1m变直径钻孔桩承台基础,共有36根桩,承台为圆端形,长58.4m、宽33.6m、高6m,承台埋置于河床中。4号墩基础采用双壁钢套箱围堰施工方案,先围堰、后平台,先钻孔、后封底,最后进行承台施工。施工中采取了以下关键技术:底节围堰(长68.2m、宽40m、高16m)采用气囊法整体下河;由底节围堰、围堰内支撑桁架和桩位钢护筒组成半浮式水上平台作为钻孔平台;钻孔桩采用泥浆护壁的气举反循环旋转钻进工艺成孔;在钻孔桩施工后,下放围堰并接高,灌水、吸泥、下沉围堰,下沉到位后分区进行围堰封底,围堰抽水,分2层、按大体积混凝土工艺进行承台施工。T he main bridge of Gong′an Changjiang River Rail‐cum‐Road Bridge is a steel truss girder cable‐stayed bridge with double pylons and with span arrangement （98＋182＋518＋182＋98） m .The foundation of Pier No .4 of the bridge is the one of bored piles plus pile cap ,of which the piles are in variable diameters of 2 .8 m/3 .1 m ,the numbers of the piles are totally 36 and the pile cap ,designed in the rounded end shape ,is 58 .4 m long ,33 .6 m wide and 6 m high and is em‐bedded in the riverbed .The foundation of the pier was constructed by the scheme of double‐wall steel boxed cofferdam in the sequence that the cofferdam was set up first ,the working platform was late ,the boring of the piles was carried out first and the base sealing of the cofferdam was late and the pile cap was concreted finally .In the construction of the foundation ,the following key techniques were applied .The first lift of the cofferdam （68 .2 m long ,40 m wide and 16 m high） was integrally launched to the river by the air bag method .The first lift of the cofferdam ,the in‐ternal support trusses of the cofferdam and the steel casings at the pier site were used to form a semi‐floating boring platform .The bored piles were constructed by the air lifting reverse circula‐tion boring aided by the bored hole wall mud protection .At the time the construction of the bored piles was completed ,the cofferdam was lowered down ,the height of the cofferdam was extended , the water was pumped into the cofferdam ,the dredging inside the cofferdam was carried out and the cofferdam was sunk down .After the cofferdam was sunk down in place to the designed eleva‐tion and the base of the cofferdam was sealed in areas .The water inside the cofferdam was pumped out and the pile cap was finally concreted in two layers according to the workmanship of massive concrete .

关 键 词：铁路公路两用桥 斜拉桥 桩基础 钢围堰 承台 钻孔平台 封底 桥梁施工 

分 类 号：U448.27[建筑科学—桥梁与隧道工程] U445.55[交通运输工程—道路与铁道工程]