“逆作法”基坑竖向支承系统设计研究

"逆作法"基坑在逆作施工期间,由于基础底板(或承台)尚未封底,地下室墙、柱等竖向构件的传力路径尚未形成,逆作施工期间的结构自重及施工荷载均由竖向支承系统承担,因此,竖向支承系统的设计是基坑"逆作法"设计的关键环节之一。结合杭州西湖凯悦大酒店、杭州中国丝绸城、杭州地铁1号线武林广场站、绍兴好望大厦等逆作法基坑工程,归纳了竖向支承系统的常见形式,总结了竖向支承柱的垂直度校正技术。采用弹簧单元模拟竖向立柱周围土体的侧向约束作用,同时计入下部混凝土立柱桩的约束作用,通过压杆临界荷载的欧拉公式反算竖向立柱的计算长度系数,并进一步分析了周边土体值、插入深度和支撑梁刚度等因素对竖向立柱计算长度系数和稳定承载力的影响。

Study on design for the vertical supporting systems of foundation pit using top-down method

In the process of construction of foundation pit using top-down method,all of the structure weight and construction loading are supported by vertical supporting systems,because the construction of the pile cap and foundation floor have not been completed,and the path of conduct force of the vertical structural component such as the walls and columns in the basement has not yet formed.So the design of the vertical supporting systems is a key step.With the background of Hangzhou,such as the Hangzhou Westlake Hyatt Hotel,Hangzhou Chinese Silk City,and Wulin Square stop of Hangzhou Metro Line No.1,etc,the most common form of the vertical supporting systems and the verticality control of erect columns are summarized.By using spring element to calculate the effect of soil lateral resistance,the effective length coefficient of erect supporting column is analyzed through the Euler′s formula for critical load of compression bar.The factors to influence the effective length coefficient and stable bearing capacity of erect columns are analyzed,including the effect of lateral soil,embed depth,and the stiffness of sustain to column.