芜湖长江公铁大桥设置式沉井基础施工关键技术

摘要

芜湖长江公铁大桥主桥为主跨588 m的双塔双索面箱桁组合梁斜拉桥,该桥3号桥塔墩采用平面尺寸为65 m×35 m的圆端形设置式沉井基础.在沉井施工中,基坑采用钻爆法整层水下爆破成型;采用2艘抓斗挖泥船进行水下清渣;采用船载多波束和侧扫声纳法进行水下测量;采用重型锚碇系统及沉井调平系统进行沉井精确定位;采取抛填袋装碎石的方式进行沉井外壁防护;沉井分2次灌注水下封底混凝土,第1次全断面封底,第2次采用逐个井孔、逐舱的方式进行混凝土灌注;沉井盖板混凝土分2次浇筑成型,从盖板四周向中间分层、分段浇筑混凝土.%The main bridge of Wuhu Changjiang River Rail-cum-Road Bridge is a box and truss composite girder cable-stayed bridge with double pylons,double cable planes and with a main span of 588 m.The foundation of the pylon pier No.3 of the bridge is the round-ended setting type open caisson in plan dimensions of 65 m×35 m.In the construction of the caisson,the foundation pit for the caisson was blast into a complete pit in a whole stratum mode underwater,using the drill-ing and blasting method.The blasted stone and soil sludge in the pit were cleared off underwater, using the 2 grab dredgers and the pit was measured underwater,using the multi-beam and side-scan shipboard sonar.The caisson was accurately positioned in the pit,using the heavy anchorage system and the caisson leveling system and was protected at its outer wall by means of riprapping the bagged rubble.The tremie concrete for the base sealing of the caisson was cast in 2 times,that was,for the 1st time,the concrete was cast for the full section of the caisson and for the 2nd time, was cast well hole by well hole and compartment by compartment.The concrete for the cover slab of the caisson was cast in 2 times and in layers and in sections from the circumference of the caisson to the center.