基于局部冲刷分析的深水基础施工工艺研究

Research on Deepwater Foundation Construction Technology Based on Local Scour Analysis

摘要:

水下基础局部冲刷对其自身及上部结构的安全稳定性均具有重大影响。以某跨江大桥深水基础为研究对象，构建三维局部冲刷数学模型，量化分析强冲刷河段群桩及围堰冲刷特征。结果表明群桩前三排桩之间冲刷较大，钢围堰迎水面两端角处发生强烈冲刷；采用规范公式、数学模型方法，钢围堰局部最大冲刷深度较群桩分别增加58%~69%，40%~46%，钢围堰若在汛期着床，底部冲刷严重，脱空面积较大；针对强冲刷河段超大埋深式基础施工，建议枯水期先进行冲刷防护，其后开展围堰着床、下沉，最后进行钻孔桩施工，待汛期来临前再进行冲刷防护。

Abstract:

The local scouring of underwater foundations significantly affects the safety and stability of both the foundation itself and the superstructure. Using the deepwater foundation of a cross-river bridge as a study case, a 3D numerical model of local scouring is built to quantitatively analyze the scouring characteristics of group piles and cofferdams in the intensely scouring river section. The results indicate that there is significant scouring among the first three rows of piles in the pile group, and the intense scouring occurs at the two corners of the water-facing side of the steel cofferdam. By using the standard formulas and the mathematical modeling methods, the maximum local scour depth of the steel cofferdam increases by 58% to 69% and 40% to 46% compared with the pile group, respectively. If the steel cofferdam is placed during the flood season, severe bottom scouring and large void areas will occur. For constructing the ultra-deep foundations in intensely scouring river sections, it is recommended to implement the scour protection firstly during the dry season, and then the placement and sinking of the cofferdam are conduced, finally the construction of bored piles is followed. The scour protection should be carried out before the flood season arrives.