On January 28, 2021, the steel caisson of No. 6 pier of Changtai Yangtze River Bridge, designed by China Railway Bridge Research Institute and constructed by China Railway Bridge Bureau, achieved accurate final settlement. The world's largest underwater open caisson foundation has set a new world record for large-scale open caisson construction under the complicated geology of super thick silty clay layer.

According to the introduction, the steel caisson of No. 6 pier of the bridge is a new type of stepped caisson with reduced self weight and erosion, and the foundation plane is round ended. The plane size is 95 meters long, 57.8 meters wide and 64 meters high, with an area equivalent to 13 standard basketball courts. The steel caisson is divided into 36 boreholes. The total weight of the steel shell structure filled with concrete for the shaft wall, the steel structure and concrete of the caisson is more than 220000 tons, which is enough to bear the bridge load with a main span of more than 1000 meters.

The total depth of steel open caisson of pier 6 is 35m, the clay layer accounts for about 21m, and the earthwork volume is about 190000m3. The construction is very difficult. Therefore, China Railway Bridge Bureau has developed hydraulic double auger suction machine, crawler type cutter suction robot, gantry type cutter suction robot, high-pressure jet drilling machine, etc. which are suitable for silty clay layer. The problem of soil sampling in blind area of caisson wall and partition wall has been solved, and the soil sampling efficiency has been greatly improved.

Intelligent crawler cutter suction robot

Intelligent gantry cutter suction robot

During the sinking process, a total of 26 sets of intelligent equipment were put into operation, realizing the average daily sinking of 25 cm, creating the fastest sinking record of large open caisson in silty clay layer.

Changtai Yangtze River Bridge is the first Yangtze River Crossing channel integrating expressway, intercity railway and ordinary highway, connecting Changzhou and Taizhou in Jiangsu Province. After completion, the main span of the main channel bridge will reach 1176 meters, which will become the largest cable-stayed bridge in the world. (please refer to www.seetao.com for reprint.  ）Editor of seetao.com / Sun Mengmeng