邻近地下结构基坑主动土压力分布规律试验研究

Experimental study on distribution pattern of active earth pressure of foundation pit adjacent to an underground structure

邻近地下结构新建基坑有限土体土压力分布规律是围护结构施工控制的关键问题。针对有限土体常见的3种破坏形式,基于薄层单元理论,定性分析既有地下结构对有限土体主动土压力分布的影响规律。综合采用模型试验与现场测试方法,验证提出的有限土体土压力分布规律合理性。结果表明:(1)半无限土体下邻近既有地下结构新建基坑主动土压力为两端小、中间大的非线性鼓形;(2)既有地下结构侧墙部位有限土体主动土压力增加幅度发生变化,转变部位在既有地下结构的顶部与底部;(3)滑裂面与既有地下结构相交于底板时,土压力呈现B型非线性分布,在既有地下结构底板处土压力值骤减;(4)有限土体土压力随有限土体面积增加(埋深增大、近接距离增大)而增大。研究成果可为探究邻近地下结构的基坑主动土压力分布情况提供新的思路与定性分析方法。

The distribution pattern of earth pressure in confined soil masses adjacent to newly excavated foundation pits near underground structures is a critical aspect of controlling the construction of retaining structures.Focusing on the three common failure modes of confined soil masses,this study qualitatively analyzes the influence of existing underground structures on the distribution of active earth pressure in confined soil masses based on the thin-layer element theory.Through a combination of model testing and field measurements,the rationality of the proposed earth pressure distribution pattern in confined soil masses is verified.The results indicate that:(1)the active earth pressure distribution in a newly excavated foundation pit adjacent to an existing underground structure and beneath semi-infinite soil masses takes on a nonlinear drum shape,with smaller values at the ends and a larger value in the middle.(2)The magnitude of increase in active earth pressure varies in the confined soil mass adjacent to the side walls of the existing underground structure,with transition points occurring at the top and bottom of the structure.(3)When the slip surface intersects the existing underground structure at its base,the distribution of soil pressure takes on a nonlinear B shape,with a sharp decrease in soil pressure at the base of the existing underground structure.(4)The earth pressure in confined soil masses increases with an increase in the area of the confined soil mass(greater depth of burial or closer proximity to the adjacent structure).The findings of this study offer new insights and qualitative analysis methods for exploring the distribution of active earth pressure in foundation pits adjacent to underground structures.