大直径盾构始发段冻结对槽壁影响的实测研究  

In situ monitoring on influence of deep foundation pit wall in freezing construction for launching of large diameter tunnel shield

作　　者：黄丰 石荣剑[1] 岳丰田[1] 张勇[1] 陆路[1] HUANG Feng;SHI Rongjian;YUE Fengtian;ZHANG Yong;LU Lu(State Key Laboratory for Geomechanics and Deep Underground Engineering,School of Mechanics and Civil Engineering,China University of Mining&Technology,Jiangsu 221116,China)

机构地区：[1]中国矿业大学深部岩土力学与地下工程国家重点实验室力学与土木工程学院,江苏徐州221116

出　　处：《中南大学学报（自然科学版）》2022年第11期4392-4400,共9页Journal of Central South University:Science and Technology

基　　金：国家高技术研究发展计划项目(2012AA06A401)。

摘　　要：为了分析大直径盾构始发段冻结过程中冻胀对槽壁变形的影响,评价工作井的结构设计和稳定性,依托上海上中路越江隧道盾构始发段冻结加固工程,通过现场监测,分析深基坑槽壁承受冻胀力及变形的变化规律。研究结果表明:冻结初始阶段,冻胀作用主要引起地层压缩变形,当冻土温度降低到-20℃以下时,冻胀作用会引起深基坑槽壁水平位移明显增加,盾构始发前实测槽壁顶端最大位移达到28.76 mm;在冻土形成过程中,土体温度降低会明显提高冻土强度和弹性模量,使冻胀力明显增加,而最大冻胀力出现在冻土温度降低到-20℃以后,且随着埋深的增加而呈线性增大,施工中实测最大冻胀力由埋深6 m处的0.314 MPa增加到埋深20 m处的0.782 MPa,为相应深度地层压力的1.5~2.0倍,地层最大冻胀力与周围地层的约束作用紧密相关,冻土周围约束作用的变化会明显改变冻胀力及其分布。冻土冻胀力导致工作井底板上部和下部的槽壁结构分别向工作井内部和外部产生弯曲变形,施工中实测最大水平位移分别为2.11mm和3.62 mm,而冻结38 d后,槽壁水平位移的增加不仅会抑制冻胀力增长幅度,而且可以减小槽壁的弯曲变形。深基坑槽壁的水平变形会明显减小其承受的冻胀力,相应减小其内部的应力分布,而工作井槽壁变形和承受冻胀力的协调作用是影响工作井稳定性的关键因素。In order to evaluate the structural design and stability of the working well by analyzing the influence of frost heaving force and deformation of the groove wall during the freezing process for launching of the large diameter tunnel shield,the following conclusions were obtained through in-site monitoring and the variation law of frost heaving force and deformation of the groove wall of the deep foundation pit,relying on the freezing and reinforcement construction for tunnel shield launching in Shanghai Shangzhong Road Tunnel.The results show that,firstly,the horizontal displacement of the wall increases significantly due to frost heave when the frozen soil temperature drops to-20℃,which limits the growth of frost heaving force,and the frost heave mainly causes formation deformation in the initial stage of freezing construction.Secondly,during the formation of frozen soil,the decrease in soil temperature will significantly increase the strength and elastic modulus of frozen soil,resulting in a significant increase in frost heaving force,and the maximum frost heaving force occurs when frozen soil temperature drops to-20℃and increases linearly with the increase of depth.During the freezing construction,the measured maximum frost heaving force increases from 0.314 MPa(at position of 6 m depth)to 0.782 MPa(at position of 20 m depth),which is 1.5-2.0 times of the formation pressure at corresponding depth,and the maximum frost heaving force of the stratum is closely related to the surrounding constraint,the change of the constraint around the frozen soil will obviously change the distribution and magnitude of the frost heaving force.Thirdly,the upper and lower groove walls of the working well floor bend inward and outward as a result of the frost heave,and the maximum horizontal displacement is 2.11 mm and 3.62 mm,respectively,and the increase in horizontal displacement of the groove wall after 38 d of freezing will not only inhibit the growth of the freezing expansion force,but also reduce the bending deformation

关 键 词：人工冻结 大直径盾构 盾构始发 槽壁变形 现场监测 

分 类 号：TU443[建筑科学—岩土工程]