深基坑桩-撑-土组合支护结构的受力特性与优化设计

Mechanical characteristics and optimization design of pile−brace−soil combined supporting structure for deep foundation pit

依托某高层建筑深基坑工程,通过现场试验获得不同施工阶段组合支护结构及基坑关键部位的变形规律。基于土体硬化模型建立深基坑组合支护体系的三维数值模型,对基坑开挖施工进行全过程模拟,分析支护结构体系的桩身弯矩、桩身位移和土压力分布规律。针对反压土的顶宽、高度、坡度以及斜支撑的间距、直径等影响因素设计正交试验,对围护桩受力变形的影响参数进行敏感性分析,并提出优化建议。研究结果表明:围护桩最大位移与最大正弯矩随反压土顶宽、高度、斜支撑直径的增大而减小,随着反压土坡度、斜支撑间距的增大而增大。桩身变形影响因素敏感性从大至小依次为反压土坡高、顶宽、反压土坡度、斜支撑间距和斜支撑直径;对组合支护体系进行设计时,建议在确定土坡自稳角度的前提下,尽量增大反压土土坡高度。

Based on a deep foundation pit of a high-rise building,the deformation of the key parts of combined supporting structure and foundation pit subjected to different construction stages was obtained by field investigation.A three-dimensional numerical model of the combined supporting structure for deep foundation pits was established by using soil hardening model.The entire process of excavation construction was simulated,and the distribution rules of pile bending moment,pile displacement and soil pressure of supporting structure system were analyzed.Orthogonal tests were designed to analyze the sensitivity of the parameters that affected the deformation of the retaining pile,such as the width,the height and the slope of counterweight soil,the spacing and diameter of inclined braces.The optimization suggestion was proposed.The results show that the maximum displacement and the maximum positive bending moment of the retaining pile decrease with the increase of the top width and height of counterweight soil,and the diameter of inclined brace,and they increase with the increase of the slope of counterweight soil and the spacing of inclined braces.The sensitivity ranking of factors affecting pile deformation from large to small are height of counterweight soil,top width of counterweight soil,slope of counterweight soil,spacing of inclined brace and diameter of inclined brace.For the engineering design of the combined support system,it is recommended to increase the height of counterweight soil as much as possible when the stability angel of counterweight soil slope is guaranteed.