Construction Monitoring Techniques for North Anchorage Caisson Foundation of the Fourth Nanjing Changjiang River Bridge

The caisson in dimensions of 69.0 m×58.0 m×52.8 m is used for the foundation of the north anchorage of the Fourth Nanjing Changjiang River Bridge and is set at a place only 90 m apart from the river dyke.The caisson is huge,the place where it is located is geologically complicated and the overburden stratum is deep.In accordance with the technical specification and with reference to the previous construction experiences,the criteria for monitoring the status of the caisson during sinking are formulated.The specific monitoring of the sinking depth,plane positions,offsetting,cutting edge reaction force,side wall soil resistance,structural stress of the caisson,the underground water level,the water level inside the caisson,the excavated ground topography at the bottom of the caisson,the ground surface settlement and the settlement the river dyke are all presented herewith.Through the monitoring,the real-time information of the caisson sinking has been understood,the guidance to the construction has been provided and the safe and smooth proceeding of the construction of the caisson has been ensured.