软土地区路堤填筑下桥梁桩基变形控制计算

Calculation method of deformation control of bridge pile foundation under embankment filling in soft soil area

我国沿海地区软土深厚,高速公路与城市道路共线工程存在施工交织的复杂工况,软基处理及后续路堤荷载产生的地基沉降和水平位移,可能对邻近先行施工的桥梁桩基产生影响,进而影响桥梁结构安全。为防止深厚软土地区路堤填筑可能引起的邻近桩基破坏和不同路段差异沉降过大的问题,采用桩-板式复合地基处理方案进行加固处理。鉴于我国现有规范对于桥梁桩基变形尚未有明确统一的控制标准,依托广东省中山市地区某路桥共线工程,提出适合当地的桩基变形控制计算方法和指标,分析了不同软基处理方案路堤填筑下桥桩桩身内力及变形。结果表明:就地固化结合混凝土管桩方案比就地固化结合水泥土搅拌桩方案更能控制桥桩内力和变形;该地区路桥共线工程中桥桩应采用桩身水平位移控制在25 mm以内,桩身裂缝控制在0.2 mm以内的双控指标;为了改善桥桩的变形及内力,在原方案基础上,提出采用泡沫轻质土填筑的改进方案。

The soft soil in China’s coastal areas is deep,and there are complicated working conditions in the collinear project of expressway and urban road.The foundation settlement and horizontal displacement caused by soft foundation treatment and subsequent embankment load may have an impact on the adjacent bridge pile foundation,and then affect the bridge structural safety.In order to prevent the damage of adjacent pile foundation and excessive differential settlement of different sections caused by embankment filling in deep soft soil area,the pile-sheet composite foundation treatment scheme is adopte d for reinforcement.In view of the fact that there is no clear and unified control standard for the deformation of bridge pile foundation in our country’s existing codes,this paper puts forward a calculation method of pile foundation deformation control suitable for soft soil areas based on a road-bridge collinear project in the Pearl River Delta region,and analyzes the internal force and deformation of bridge pile under embankment filling with different soft foundation treatment schemes.The results show that:the in-situ curing concrete pipe pile scheme can control the internal force and deformation of bridge pile better than the in-situ curing cement-soil mixing pile scheme.In the road-bridge collinear project in this area,the double control standard of pile horizontal displacement within 25 mm and pile crack within 0.2 mm should be adopted.In order to control the deformation and internal force of bridge piles,based on the original scheme,an improved scheme of filling with foam lightweight soil is put forward.