平潭海峡公铁两用大桥主航道斜拉桥深水基础设计

Design of Deepwater Foundations of Main Ship Channel Cable-Stayed Bridge of Pingtan Straits Rail-cum-Road Bridge

平潭海峡公铁两用大桥元洪主航道桥为（132＋196＋532＋196＋132）m的钢桁梁斜拉桥。为满足通航要求并适应深水条件和巨大的水平力荷载,该桥桥塔墩基础采用22～24根Φ4.0m钻孔桩,C45水下混凝土,平均桩长47.3～64.0m,桩距纵、横向均为8.2m。边墩、辅助墩桩基础均采用10根Φ4.0m钻孔桩,C45水下混凝土,平均桩长29.5～70.0m,桩距横向为8.2m、纵向为7.2m。为降低施工风险和工期压力、减少基础施工对通航的影响,将该桥基础承台底高程设计为-4.0m。主墩承台采用圆端哑铃形,C50混凝土,承台顶高程＋5.0m,平面尺寸81.0m×33.0m,厚9.0m;边墩、辅助墩承台均采用倒圆角矩形,C50混凝土,承台顶高程＋4.0 m,平面尺寸31.8m×21.6m,厚8.0m。主墩基础采用双壁钢吊箱围堰施工方案。

The Yuanhong main ship channel bridge of the Pingtan Straits Rail-cum-Road Bridge is a steel truss girder cable-stayed bridge with span arrangement（132＋196＋532＋196＋132）m.To meet the navigational requirements and to accommodate the deepwater construction conditions and the enormous horizontal force loads,the foundations of the pylon piers of the bridge are designed into the ones of 22～24nos.ofΦ4.0mbored piles.The concrete for the piles is the C45 tremie concrete,the average length of the piles is 47.3～64.0mand the spacing of the piles in the transverse and longitudinal directions is all 8.2m.For the foundations of the side and auxiliary piers,each 10 nos.ofΦ4.0mbored piles are designed.The concrete for the piles is the C45 tremie concrete,the average length of the piles is 29.5～70.0mand the spacing of the piles in the transverse directions is 8.2mand in the longitudinal directions is 7.2m.To decrease the construction risk,relief the pressure of the construction time schedule and to minimize the influences of the construction of the foundations on the navigation,the elevation of the pile cap bottoms of all the foundations is designed as-4.0m.The pile caps of the foundations of the pylon piers are the roundend dumbbell shapes and the concrete for the pile caps is the C50 concrete.The elevation of the pile cap tops is＋5.0m,the plan dimensions of the pile caps are 81.0m×33.0mand the depth is9.0m.The pile caps of the foundations of the side and auxiliary piers are the rounded corner rectangular shapes and the concrete for the pile caps is the C50 concrete.The elevation of the pile cap tops is＋4.0m,the plan dimensions of the pile caps are 31.8m×21.6mand the depth is 8.0m.The foundations of the pylon piers are to be constructed,using the scheme of the double-wall steel boxed cofferdams.