昆明枢纽扩能改造下穿通道基坑支护工程设计研究

Design Study on Foundation Pit Support Engineering of the Underpass for the Kunming Hub Capacity Expansion and Reconstruction Project

昆明枢纽沿线软土发育范围广、深度大、成分复杂,工程地质条件、水文地质条件极为复杂。枢纽扩能改造工程下穿通道基坑多毗邻既有铁路、军事管制区、市政道路及高层建筑物等,变形控制要求高、难度大。复杂敏感环境下软土深基坑的支护设计及变形控制成为扩能改造工程的设计难点。本文在搜集、分析昆明地区既有基坑工程案例经验教训的基础上,归纳总结了影响昆明枢纽基坑工程安全的关键性因素,研究了软土基坑中围护结构、内支撑的受力变形特征,揭示了基坑施工对临近设施影响的作用机理,提出了"防渗水、保安全、控变形、重监测"的基坑设计原则,形成了复杂敏感环境下软土基坑加固及变形控制成套技术,可为未来昆明地区基坑工程的安全设计提供理论支撑。

Soft soil is extensively developed along the Kunming Hub featuring deep depth,complicated composition,and extremely complex engineering-geological conditions and hydro-geological conditions.Most foundation pits of the underpass for the Kunming Hub capacity expansion and reconstruction project approach existing railways,military control zones,municipal roads,and high-rise buildings,with high requirements and construction difficulties on deformation control.In the complex and sensitive environment,the support design and deformation control for deep foundation pits in soft soil has brought great difficulties for the design of the capacity expansion and reconstruction project.This document collects and analyzes the cases and experience of existing foundation pit projects in Kunming,summarizes the key factors affecting the safety of foundation pit engineering of Kunming Hub,studies the stress and deformation features of the enclosure and inner support for foundation pits in soft soil,reveals the mechanism how foundation pit construction affects adjacent facilities,presents the design principles of"seepage prevention,safety protection,deformation control,and monitoring highlight"for foundation pits,and forms packaged technologies for reinforcement and deformation control of soft-soil foundation pits in the complex and sensitive environment.It provides theoretical support for the safety design of foundation pit engineering in Kunming in the future.