考虑空间效应的深长基坑围护结构受力与变形分析

Analysis of stress and deformation of retaining structure in deep foundation pit based on spatial effect

城市道路的下穿改造工程经常需要开挖深基坑,而深基坑的开挖存在较明显的空间效应。为深入研究深基坑开挖的空间效应对工程围护结构及周边环境的影响,以深圳市公常路下穿改造工程K2+000~K2+120段为工程背景,开展现场监测和数值模拟研究。采用Midas GTS有限元软件,对其开挖过程进行模拟,通过参数分析,探讨超载、围护桩桩径以及钢支撑预加力等因素对深基坑围护结构受力及变形的影响。研究结果表明:基坑周边超载增大将导致围护桩变形与周边地表沉降的显著增大;周边超载的变化将影响基坑受力、变形及周边地表沉降。当围护桩桩径大于0.8 m时,其对围护结构弯矩的空间效应影响显著。通过对钢支撑施加预加力,可调节围护结构弯矩,减小桩体位移,控制周边地表沉降值。在该工程中,钢支撑预加力对基坑的空间效应影响甚微。该研究可为类似基坑工程的设计与施工提供参考。

The excavation of a deep foundation pit is often required for the reconstruction of urban road underpasses,and deep foundation pit excavation has obvious spatial effect.In order to gain an in-depth understanding of the spatial impact of deep excavation on the enclosure structure and the surrounding environment,the on-site monitoring and numerical simulation studies based on the deep foundation pit project of the K2+000~K2+120 section of the Shenzhen Gongchang Road underpass reconstruction project were carried out.Numerical software Midas GTS was used to investigate the effects of overloading,enclosure pile diameter and steel support preloading on stress and deformation of deep foundation pit enclosure structure through parametric analysis.The results shows that overload around the perimeters of the pits deformed the perimeters and caused significant settlement of the surrounding ground.The spatial effects of pit stress,deformation and settlement of the surrounding ground surface were affected by changes in peripheral overload.When the diameter of fender pile was greater than 0.8m,its spatial effect on the bending moment of the surrounding structure was of great importance.By applying a pre-stressing force to the steel support,the bending moment of the enclosure structure could be adjusted to reduce pile displacement and control the value of the surrounding surface settlement.For this project,the prestressing force of the steel columns did not have a significant effect on the spatial effect of the pit.The study could serve as a reference for designing and constructing similar pits in other areas.