大型钢沉井第二次取土下沉施工监控分析

Monitoring and analysis of the second borrowing and sinking construction of large steel open caisson

常泰长江大桥5号墩基础采用平面圆端形、立面台阶形沉井结构,沉井长95.0 m,宽57.8 m,高64 m,为目前世界上最大水中钢沉井。在第2次取土下沉过程中,由于地层分布差异大,沉井底面受力不均匀,长边和短边倾斜姿态敏感性强等特点,施工采用了台阶形取土工艺,遵循对称、同步、均匀取土原则,通过一系列主动控制和动态纠偏措施,实现了沉井高效、平稳下沉。通过反演,下沉系数与下沉速率正相关,当下沉系数小于1时,沉井几乎不会下沉;当下沉系数超过1.1,沉井下沉速率可进一步加快;沉井下沉到位后受力状态、支撑状态及几何姿态均保持良好。

The foundation of the No.5 pier of the Changtai Yangtze River Bridge is designed as a flat round-end type and a stepped-faced open caisson structure.Its dimensions are 95.0 m in length,57.8 m in width and 64 m in height,which is currently considered the largest underwater steel open caisson in the world.During the second borrowing and sinking construction process,due to the large difference in the stratum distribution,uneven stress on the bottom of the caisson,and strong sensitivity of the long side and short side tilt attitude,the"stepped"method of borrowing was adopted in the construction,following the principles of symmetry,synchronicity and uniformity.Through a series of active control and dynamic correction measures,the caisson sinks efficiently and smoothly.Through inversion analysis,the subsidence coefficient is positively correlated with the subsidence rate.When the subsidence coefficient is less than 1,the caisson will hardly sink;when the subsidence coefficient exceeds 1.1,the sinking rate of the caisson can be further accelerated.Finally,after sinking the open caisson in place,the stress state,support state and geometric attitude are kept in good condition.