砂土地基深围井开挖坑底回弹与扰动规律数值分析

    Numerical analysis of shaft excavation-induced rebound and soil disturbance in deep sand deposit

    • 摘要: 通过计算分析揭示基坑底部土体应力与变形以及扰动规律,可为基坑设计与施工、在基坑内部开展勘探取样与原位测试等工作提供科学依据。小应变硬化模型能够考虑土体刚度随应变的非线性变化,被广泛用于应变水平较小的基坑开挖计算分析研究。目前,小应变硬化土模型的研究主要集中于典型的软土地基,针对砂土地基的研究较少。本文针对某深厚覆盖层场地开展了砂土室内试验和小应变硬化模型本构参数标定工作,并利用FLAC3D软件对砂土地基深围井开挖坑底回弹与扰动规律进行了计算分析。研究表明,砂土的HSS模型参数与典型软土存在显著差异,且具有地基深度相关性;围井环形支护体系能有效抑制深开挖引起的结构变形;开挖卸荷对坑内土体的影响程度与范围随开挖深度的增加非线性增大;砂土地基坑底回弹变形主要源于砂土强扰动区,且受支护结构变形的影响。本文研究成果可为深厚砂土地基中类似超深环形基坑的坑底土体扰动评价与设计施工提供参考。

       

      Abstract: The analyses of the stress and deformation fields and soil disturbance at the bottom of a pit provide the guidance for the shaft design and construction, the geotechnical investigation and field testing in it. The small-strain hardening model (HSS) is widely adopted in numerical analysis of excavation problems due to its enhanced capability of considering the nonlinear stiffness-strain relationship of soils at small strain range. Existing research on HSS model parameters mainly focuses on typical soft soils, with limited studies on sandy ground. This study conducts a series of laboratory tests and calibrated the HSS model parameters for a deep sand ground, and then the shaft excavation-induced rebound and soil disturbance are analyzed by FLAC3D. The results illustrate that the HSS model parameters exhibit notable differences from typical soft soils and the depth dependency; the annular support system effectively restrains the structural deformation during excavation; the excavation-induced unloading effects develop nonlinearly with depth; and the rebound of the excavation predominantly occurs within the loosened zone in sandy layer and is also affected by the deformation of supporting structure. These findings provide valuable references for the evaluation of deep excavation-induced soil disturbance, and the design and construction of similar annular shaft in deep sandy ground.

       

    /

    返回文章
    返回