Influence of foundation pit excavation on deformation of subway tunnel below

The excavation of foundation pits is one of the most important factors causing changes to the initial stress state of its surrounding soil, thus affecting the safety of nearby existing subway tunnels. In order to study the deformation in metro lines induced by adjacent foundation pit excavation, a three-dimensional model based on an actual engineering case was established, and the deformation regulations of the retaining wall, surrounding soil, and tunnels were investigated, which also validated the model’s feasibility. Additionally, the deformation and strain response of the subway tunnel under different selection parameters of the enclosing structure and soil were studied. The results showed that, after the foundation pit excavation, the soil inside the pit underwent an uplift, the surrounding soil outside of the pit showed vertical settlement, and the retaining wall created a deformation towards the interior of the pit. Mechanical parameters of plate elements have a small influence on the deformation of metro lines. Axial strain and maximum displacement of the subway tunnel increase with the increase in the soil’s Poisson’s ratio, and on the contrary, they decrease with the increase in the m-value and G 0 , ref . The maximum responses of the subway tunnel came from changes to G 0 , ref and υ . These analysis results can be used for the safety evaluation of subway tunnel operation, design, and construction in other similar engineering settings.

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Study on Deformation Law of Deep Foundation Pit with the Top-Down Method and Its Influence on Adjacent Subway Tunnel

Advances in Civil Engineering ◽

10.1155/2020/8852336 ◽

2020 ◽

Vol 2020 ◽

pp. 1-15

Author(s):

Yue Gui ◽

Zhenxing Zhao ◽

Xiaqiang Qin ◽

Jianfei Wang

Keyword(s):

Axial Force ◽

Ground Deformation ◽

Diaphragm Wall ◽

Subway Tunnel ◽

Top Down ◽

Deep Foundation ◽

Foundation Pit ◽

Maximum Settlement ◽

The Impact ◽

The Relationship

Based on a long-term comprehensive instrumentation program, the performance of an excavation pit constructed by the top-down method in downtown Kunming was extensively examined. The measured excavation responses included the deflections of diaphragm wall, vertical column movement, slab axial force, building settlement caused by ground deformation, and the influence of pit excavation on the adjacent subway tunnel. This paper analyses the monitoring data of the existing construction stage. Based on the analyses on the data of field and numerical simulation, the following major findings were obtained: (1) the relationship between the measured maximum wall deflection, δ h m , and excavation depth, H , in this study is δ h m = 0.06 % H ∼ 0.27 % H , which is quite different compared with the relationship of soft-soil pit δ h m = 0.02 % H ∼ 1.2 % H , but closer to the normalized curve of rock-socketed pile δ h m = 0.01 % H ∼ 0.45 % H and rock-socketed diaphragm wall δ h m = 0.031 % H ∼ 0.129 % H . (2) The relationship between the maximum settlement of column ( δ p ) and excavation depth ( H ) is δ p = − 0.09 % ∼ 0.04 % H . The maximum distortion between the diaphragm wall and the column is less than 1/500 of the limit range proposed by Bjerrum. (3) The impact range caused by excavation is about 3.8 times the maximum excavation depth. The ground settlement around the foundation pit is groove type, and the maximum settlement point is located at 2.7 times the maximum excavation depth. (4) The excavation of the foundation pit leads to the maximum vertical settlement of 2 mm and maximum horizontal displacement of 5.2 mm in the subway tunnel; the maximum change of axial force and bending moment are 8.8 kN (the vertical direction) and 6.4 kN·m/m (the horizontal direction), respectively.

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Numerical Modeling of Affection of Foundation Pit Excavation on Metro Tunnel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.368-373.2562 ◽

2011 ◽

Vol 368-373 ◽

pp. 2562-2566 ◽

Cited By ~ 1

Author(s):

Jiang Shu Ding ◽

Yao Qiang Xian ◽

Tian Jun Liu

Keyword(s):

Normal Operation ◽

Deep Excavation ◽

Subway Tunnel ◽

Underground Engineering ◽

Foundation Pit ◽

Element Analysis ◽

Urban Transit ◽

3D Finite Element ◽

Transit Network ◽

Metro Tunnel

With the development of urban construction, urban transit network has been gradually improved, but subway tunnel under its normal operation is inevitably affected by underground engineering activities such as foundation pit engineering. Based on the deep excavation near the effects of tunnel, the research content of 3d finite element analysis, from the qualitative research based on different situations of foundation excavation, is near to optimize the design and construction to provide the beneficial reference.

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Impact Assessment of Common Supported Excavation of Double Foundation Pits on the Adjacent Tunnel

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.170-173.1524 ◽

2012 ◽

Vol 170-173 ◽

pp. 1524-1527 ◽

Cited By ~ 1

Author(s):

Hui Shen ◽

Jin Feng Bi ◽

Xian Qi Luo

Keyword(s):

Simulation Analysis ◽

Comprehensive Evaluation ◽

Subway Tunnel ◽

Deep Foundation ◽

Foundation Pit ◽

Support Design ◽

Maximum Displacement ◽

Total Displacement ◽

Common Support ◽

Structure Lead

Based on the deep excavation engineering which used the common support design near the range of Suzhou Rail Transit Line 2, a 3-D numerical model was created to make the numerical simulation analysis of the deep foundation pit construction and obtain the comprehensive evaluation of the influence on the nearby subway tunnel stress and deformation when the 3 # and 4 # block foundation pits were excavated. The numerical results show that: when the pits are excavated to the basement, the total displacement value of the tunnel is 1.6mm. Because of the aspect ratio difference between the 3# and 4# block pits, the subway tunnel displacement of every direction trends to the 3# block. And the preserving soil area between the two blocks makes the tunnel stress present a symmetric distribution along the soil area's cross section. The surface settlements of soil behind enclosure structure lead to a great impact on the pipelines, whose maximum reaches 5mm. For comprehensive, the maximum displacement and spring back deformation of the subway tunnel meet the control requirements, with a certain margin of safety.

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Influence of Large Foundation Pit Excavation on Adjacent Subway Tunnel

DEStech Transactions on Engineering and Technology Research ◽

10.12783/dtetr/iccere2017/18273 ◽

2018 ◽

Author(s):

Fuguang Zhu ◽

He Huang ◽

Xiaodong Liu ◽

Hanyang Liu ◽

Zhangjun Dai

Keyword(s):

Subway Tunnel ◽

Foundation Pit

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Impact Analysis of Foundation Pit Excavation on the Deformation of Nearby Subway Tunnel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.935.233 ◽

2014 ◽

Vol 935 ◽

pp. 233-236

Author(s):

Hui Shen ◽

Jin Feng Bi ◽

Tong Qi Ping

Keyword(s):

Impact Analysis ◽

Simulation Analysis ◽

Three Dimensional ◽

Subway Tunnel ◽

Foundation Pit ◽

Soil Subsidence ◽

Maximum Value ◽

Margin Of Safety ◽

Design Proposal ◽

The Impact

Bracing of foundation pit design proposal based on the excavation near a block of Suzhou Rail Transit Line 1 is used to build a subway tunnel-pit-envelope three-dimensional computational model, which is analyzed by FLAC3D, software for numerical simulation analysis, to evaluate the impact of the foundation pit excavation on the deformation of the subway tunnel. The calculated results show that: when the pit is excavated to the bottom, the deformation of the tunnel achieves the maximum value, 0.6mm of y direction and 6.54mm of z direction. The pipelines with shallow depth are subject to the deformation caused by the soil subsidence back of the envelope, whose maximum value has reached 7.6mm beyond the control standards. In terms of the deformation of the subway tunnel structure, the deformation can meet the control requirements, and have a certain margin of safety.

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Performance of a Large-Scale Excavation by Bottom-Up Technique in Hangzhou Soft Clay

Advances in Civil Engineering ◽

10.1155/2021/6061849 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Ri-qing Xu ◽

Yi-hong Zhu ◽

Pan Ding

Keyword(s):

Large Scale ◽

Lateral Displacement ◽

Soft Soil ◽

Soft Clay ◽

Ground Surface ◽

Diaphragm Wall ◽

Subway Tunnel ◽

Control Effect ◽

Foundation Pit ◽

Rapid Excavation

This paper studied the excavation of a foundation pit above a running subway tunnel in Hangzhou soft soil. The zoned excavation and top-down construction techniques were adopted to control the deformation caused by foundation pit excavation. The excavation was divided into four parts, named Zone A, B, C, and D. Zone A adopted temporary diagonal bracing, and the control effect of deformation was poor; it was cancelled and changed to rapid excavation and thicker cushion in Zones B, C, and D. During the whole construction process, the lateral displacement and settlement of the diaphragm wall, surrounding ground surface, and building settlement were monitored and analysed. The data showed that the lateral displacement of the diaphragm wall was effectively reduced by the zoned excavation technique, and the maximum lateral displacement value of the diaphragm wall in Zone A was the least; rapid excavation and reduced soil exposure time also could effectively control the deformation, and the lateral displacement of the diaphragm wall in Zone C is less than Zone B and Zone D. The ground settlement is strongly related to the lateral displacement of the diaphragm wall. In order to reduce the surrounding ground and building settlements, efforts should be made to reduce the wall lateral displacement.

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