Construction Technique of Rock-Socketed Pile Cap in Water Area of Zhenjiang Railway Bridge in Jiangkou County

The Zhenjiang Railway Bridge in Jiangkou County is a 22-span simply-supported T beam bridge accommodating a single Fail track.The piers No.17 ～ No.20 are in-water piers,where the depth of the river is 9 m.The buried depth of the pile caps is 2.12～3.12 m and the river bed is founded by sandstone mingled with gravels.Through the comparison of several schemes,the one of "to construct the pile first and the cofferdam late" is determined and adopted in the pile cap construction.The detailed construction steps are,first,to set up an operation platform using the steel casings after the completion of the pile foundation construction,then,to carry out underwater blasting and channeling and bury single-wall steel cofferdam,at last,to conduct foundation pit excavation and construct the pile caps and the pier shafts.Practice proves that under the geological condition of shallow covering layer and sandstones,the buried single-wall steel cofferdam can reduce the volume of underwater blasting and excavation in pile cap construction,decrease construction cost and shorten construction time.