某软土地层“台阶”式分隔型基坑变形特性及施工顺序的影响  

Deformation characteristics of stepped divided excavation in soft soil layers and the influence of the construction sequence

作　　者：周鼎文 应宏伟[1,2] 朱成伟 李慧慧[3] ZHOU Dingwen;YING Hongwei;ZHU Chengwei;LI Huihui(Research Center of Coastal and Urban Geotechnical Engineering,Zhejiang University,Hangzhou 310058,Zhejiang,China;Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering,Hohai University,Nanjing 210098,Jiangsu,China;Hangzhou Survey and Design Research Institute Co.,Ltd.,Hangzhou 310013,Zhejiang,China)

机构地区：[1]浙江大学滨海和城市岩土工程研究中心,浙江杭州310058 [2]河海大学岩土力学与堤坝工程教育部重点实验室,江苏南京210098 [3]杭州市勘测设计研究院有限公司,浙江杭州310013

出　　处：《地基处理》2025年第2期163-170,184,共9页Journal of Ground Improvement

基　　金：国家自然科学基金(51678523);浙江省建设科研项目(2018K119)。

摘　　要：工程实践已证明分坑施工是控制软黏土深大基坑变形的有效措施,本文在常规相同挖深的“平台”式分坑方案的基础上,提出了进一步减小近坑深度的“台阶”式分坑施工技术。以杭州钱塘江北岸某邻近既有隧道的深基坑工程为背景,建立有限元分析模型,通过围护墙变形实测与数值模拟数据的对比验证了参数的合理性,深入研究了“台阶”式分隔型基坑施工全过程的墙体、坑外地层及邻近既有地铁盾构隧道的位移变化规律和分坑施工顺序的影响。分析表明,基坑开挖、拆换撑和地下室回筑完成的全过程受分坑施工和伺服支撑技术的影响,近坑围护墙变形呈现出从“内凸型”、“复合型”到“悬臂型”的变化趋势。将与既有隧道的相对距离作为远、近分坑的区分标准,与先远后近分坑施工方案相比,近坑地下室在阻隔应力传递方面起到了积极作用;对于杭州典型软土地层“台阶”式分隔型深基坑,先近后远施工时的围护墙最大水平位移和坑外最大地表沉降可减小约15%~25%。本文提出了分坑施工顺序对杭州“台阶”式分隔型基坑坑外地层位移影响分区的概念,实践中可根据重点保护设施所属分区选择合理的施工顺序。It has been proved from engineering practice that segregated pits construction is an effective measure to control the deformation of deep and large foundation pits in soft clay.On the basis of conventional split-pit scheme with unified excavation depth,the stepped divided excavation method is proposed to reduce the depth of the close sub-pit.A finite element analysis model was established with the background of a deep foundation pit project adjacent to existing tunnels on the north of Qiantang River in Hangzhou.By comparing the measured and numerical simulation displacements of the retaining wall,the rationality of the parameters of the constitutive model was verified.An in-depth study was conducted on the displacement patterns of the retaining wall,the stratum outside the pit,and the adjacent existing metro tunnels during the whole process of the construction,as well as the influence of the sequence of the sub-pits construction.The analysis shows that during the entire process of the construction,the deformation curve of the close pit retaining wall shows a trend of convex,composite to cantilever type due to the influence of segregated pits construction and servo support technology.Using the relative distance to the existing tunnel as a criterion for dividing the far and close sub-pit,compared with the construction scheme of constructing the pits from far to near,the basement of the close sub-pit plays a positive role in blocking stress transmission.For the typical soft soil stratum in Hangzhou,the maximum displacement of the close pit retaining wall and the maximum ground settlement outside the pit can be reduced by approximately 15%to 25%when the construction is carried out from near to far for the stepped divided excavation.The concept of the displacement impact zone of stepped divided excavation pits in Hangzhou resulting from different construction sequences was proposed,and the reasonable construction sequence should be selected according to the zone where the existing underground infrastructure is located

关 键 词：“台阶”式分隔型基坑 分坑施工顺序 围护墙变形 土体位移 影响分区 

分 类 号：TU753[建筑科学—建筑技术科学]