刘家渠特大桥临近既有线深基坑防护设计

On the Design of the Supporting for the Deep Foundation Pit of the Liujiaqu Mega Bridge near an Existing Railway

针对刘家渠特大桥临近既有线的基坑,通过对工程造价、施工对土层的扰动、施工难度等因素进行综合考量,最后确定采用钢筋混凝土防护桩的支护方案。由于临近既有线,确定了人工挖孔、浇筑混凝土围圈、隔孔施工的方案。结合建筑基坑支护技术规程,合理确定防护桩的计算图示,采用理正深基坑软件进行了内力、位移和地表沉降计算,并且采用经典法进行了防护桩的抗倾覆稳定计算。结果表明防护桩各项指标满足要求,可为相似基坑施工方案设计与施工提供有益的参考。

As the foundation pit of the Liujiaqu Mega Bridge is near an existing railway, the supporting scheme of using rein-forced concrete protective piles is finally chosen for it after comprehensively considering all the factors such as the costs of the project ,the disturbace of the construction to the stratum,construction,etc. Owing to the fact that the project is close to an exist-ing railway, the construction scheme of the manual excavation of holes,building the cofferdam by casting concrete,and perform-ing the construction at every other hole is determined in the end. According to the technical specifications of retaining and sup- porting for architectural foundation pi ts,the calculation chart of the protective pile is rationally determined,with the internal forces,displacement,and the settlement of the ground surface calculated by means of the Leezheng Software for Deep Founda-tion Pits. Besides,the anti-overturning stability of the protective pile is also calculated by the classical method. The result of the calculation shows that the protective pile up to the requirements. Therefore,the project may serve as a useful reference for the design and construction of other similar foundation pits.