Time effect of step-by-step excavation unloading in soft soils and its influence on adjacent tunnels

被引：1

作者：

Li H. ^{[1
,2
]}

Liao S. ^{[1
]}

He J. ^{[1
]}

Du Y. ^{[3
]}

Wang Y. ^{[4
]}

Bai Q. ^{[4
]}

机构：

[1] Department of Geotechnical Engineering, Tongji University, Shanghai

[2] China Construction Eighth Engineering Division Co., Ltd., Shenzhen

[3] Shanghai Municipal Engineering Design Institute (Group) Co. Ltd., Shanghai

[4] Shanghai Airport (Group) Co. Ltd., Shanghai

来源：

Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | 2023年 / 54卷 / 03期

基金：

上海市自然科学基金; 中国国家自然科学基金;

关键词：

foundation pit; similarity model test; soft clay; step-by-step unloading time-effect; tunnel;

D O I：

10.11817/j.issn.1672-7207.2023.03.021

中图分类号：

学科分类号：

摘要：

A physical model test with a similarity ratio of 1:20 was conducted to study the time-effect of foundation pit excavation unloading in soft soils and its influence on nearby tunnels positioned below the pit bottom. The experiment data regarding lateral retaining wall displacement, ground surface settlement, basal heave, vertical of the tunnel and horizontal displacement of the tunnel, and convergence deformation of tunnel cross section were obtained. The results show that the maximum lateral wall displacement induced by excavation is 0.61%H (H is final excavation depth), which is greater than the upper limit of the maximum retaining wall deflection of metro station in Shanghai soft soils of 0.50%H. The development of lateral wall displacement and surface settlement during the step-by-step excavation presents a noticeable time effect, with the impact on the pit deformation becoming more pronounced as the depth of the excavation increases. Excavation-caused tunnel deformation is characterized by significant horizontal displacement towards the pit and relative smaller upward vertical displacement when the tunnel is located below the basal surface. Lateral displacement of the tunnel is approximately linear with that of retaining wall at the same depth, and hence the lateral deformation of tunnel caused by subsequent excavation can be predicted. The excavation-caused radial convergence of the tunnel is characterized by transverse elongation and vertical compression, and the transverse convergence is about 1.7 times of the vertical convergence. When the clear distance between the tunnel and excavation surface is within 0.2H− 0.5H, the tunnel deformation response caused by excavation unloading is particularly sensitive and the vertical deformation of the tunnel greatly increases with the increase of basal heave. © 2023 Central South University of Technology. All rights reserved.

引用

页码：1044 / 1053

页数：9

共 25 条

[11]

LI Mingguang, XIAO Xiao, WANG Jianhua, Et al., Numerical study on responses of an existing metro line to staged deep excavations[J], Tunnelling and Underground Space Technology, 85, (2019)

[12]

LIAO Shaoming, WEI Shifeng, SHEN Shuilong, Structural responses of existing metro stations to adjacent deep excavations in Suzhou, China, Journal of Performance of Constructed Facilities, 30, 4, (2016)

[13]

WEI Huanwei, YANG Fan, LUO Wei, Et al., Model test study on the effect of foundation pit excavation under single soil layer on existing tunnels, Journal of Shandong Jianzhu University, 35, 6, (2020)

[14]

TAN Yong, LI Xiang, KANG Zhijun, Et al., Zoned excavation of an oversized pit close to an existing metro line in stiff clay: case study, Journal of Performance of Constructed Facilities, 29, 6, (2015)

[15]

XU Zhonghua, ZONG Ludan, SHEN Jian, Et al., Deformation of a deep excavation adjacent to metro tunnels in soft soils, Chinese Journal of Geotechnical Engineering, 41, S1, (2019)

[16]

ZHENG Gang, DU Yiming, DIAO Yu, Et al., Influenced zones for deformation of existing tunnels adjacent to excavations, Chinese Journal of Geotechnical Engineering, 38, 4, (2016)

[17]

YAN Xuli, YAO Aijun, ZHOU Yijun, Et al., Analysis on the stress path of soil around existing tunnels influenced by adjacent excavation of foundation pits, Chinese Journal of Underground Space and Engineering, 15, 5, (2019)

[18]

WEI Huanwei, YANG Fan, LUO Wei, Et al., Model test study on the effect of foundation pit excavation under single soil layer on existing tunnels[J], Journal of Shandong Jianzhu University, 35, 6, (2020)

[19]

CHEN Renpeng, LIU Shulun, MENG Fanyan, Et al., Centrifuge modeling of excavation effects on a nearby tunnel in soft clay, Chinese Journal of Geotechnical Engineering, 42, 6, (2020)

[20]

Foundation design code

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