Abstract: The depth of deep foundation pit of the main pier of Caijiazhuang Large Bridge is 11.25m, the groundwater level is high, and it is close to the Yangshe railway in operation. After analysis and trial calculation, large-diameter Locking steel pipe piles are adopted as the main supporting structure. According to the variation law of soil and water side pressure, the vertical spacing of the purlin surrounding system is reasonably designed. At the same time, in order to prevent water, the construction method of pouring isolated cement mortar in the lock is used to facilitate the removal of the steel pipe pile. The strength, horizontal displacement and settlement of existing railway subgrade outside the pit meet the requirements by using the straightening software to calculate the supporting structure. Moreover, the results of construction monitoring are in good agreement with the theoretical calculation value, and the removal of the protective pile is smooth. This has a good reference significance for the construction and support scheme design of deep foundation pit near the existing line.

Key words: deep foundation pit, adjacent railway, locking steel pipe pile, still waters, surface settlement

摘要： 蔡家庄特大桥主墩基坑深度11.25m,地下水位高,属于深基坑,且基坑紧邻运营的阳涉铁路,经过分析和试算,采用了大直径锁口钢管桩作为支护结构主体。根据土、水侧压力的变化规律,合理设计了围囹体系的竖向间距。同时为了止水,在锁口内采用了灌注隔离水泥砂浆的施工方法,便于钢管桩的拔除。通过采用理正软件对支护结构进行计算,防护桩的强度、水平位移、坑外既有铁路路基位置的沉降均满足要求,且施工监测的结果与理论计算值切合度高,防护桩拔除顺利。

关键词: 深基坑, 临近铁路, 锁口钢管桩, 止水, 地表沉降