先浅后深深基坑工程的设计与分析

Design and analysis of the deep foundation pit project constructed from shallow to deep

依托某实际深基坑工程,通过计算分析、监测数据验证对先浅后深深基坑支护设计和施工中的关键技术进行了研究。研究表明,深浅基坑交界处存在较大高差时,可通过采用增大支护桩及支撑刚度、加固坑内被动区土体、加强止水帷幕以及严控施工质量等一系列措施,减小深基坑开挖对邻近已建建筑物及浅基坑的影响,确保结构的安全与稳定。深浅基坑交界处,后施工的深基坑支护桩可通过适当提高桩顶标高,使后施工的深基坑形成独立封闭体系,方便后期水平支撑的拆换撑施工;并可通过桩顶箍筋加密的方式来解决支护桩上部超出土面部分的抗剪强度问题。

Based on an actual deep foundation pit engineering project, theoretical analysis and monitoring data verification were conducted to study the key technologies in the design and construction of deep foundation pit supports constructed from shallow to deep. The results indicate that if there is a large difference between the deep pit depth and shallow pit depth, applicable measures can be adopted, such as increasing the rigidity of support piles and supports, reinforcing the soil in the passive zone in the pit, strengthening the water-stop curtain and strictly controlling the construction quality, to reduce the impact of deep pit excavation on the adjacent completed buildings and shallow pits, and ensure the safety and stability of the structure. At the junction of deep and shallow foundation pits, the post-construction deep foundation pit supporting piles can be appropriately raised to increase the pile top elevation so that the post-construction deep foundation pit forms an independent closed system, which facilitates the removal and replacement of horizontal supports in the later stage;the problem of the shear strength of the upper part of the supporting pile beyond the soil surface can be solved by the method of densification of the pile top stirrup.