Ground surface settlements due to construction of closely-spaced twin tunnels with different geometric arrangements

2016 ◽  
Vol 51 ◽  
pp. 144-151 ◽  
Author(s):  
Qian Fang ◽  
Qimin Tai ◽  
Dingli Zhang ◽  
Louis Ngai Yuen Wong
Keyword(s):  
Ground Surface ◽  
Geometric Arrangements ◽  
Surface Settlements ◽  
Twin Tunnels

Effects of the construction sequence of twin tunnels at different depths on an existing pile

2014 ◽  
Vol 51 (2) ◽  
pp. 173-183 ◽  
Author(s):  
C.W.W. Ng ◽  
H. Lu
Keyword(s):  
Three Dimensional ◽  
Ground Surface ◽  
Pile Capacity ◽  
Tunnel Excavation ◽  
Construction Sequence ◽  
Pile Shaft ◽  
Different Depths ◽  
Pile Settlement ◽  
Surface Settlements ◽  
Twin Tunnels

Any tunnelling process inevitably induces changes in stress in the ground and may adversely affect nearby pile foundations. The interaction between tunnelling and an existing pile has been investigated by researchers and a certain amount of fundamental understanding has been gained. However, the effects of different tunnel excavation sequences on an adjacent pile remain to be understood. In this paper, a series of three-dimensional centrifuge model tests and numerical back-analyses were carried out to investigate the effects of construction sequence of twin tunnels on an existing pile in dry sand. Two tunnelling sequences were investigated: (i) a sequence involving tunnelling near the pile toe followed by tunnelling near the mid-depth of the pile shaft (i.e., test TS); (ii) sequence involving tunnelling near the mid-depth of the pile shaft followed by tunnelling near the pile toe (i.e., test ST). The measured cumulative pile settlement was about 33% larger for tunnelling sequence ST than for tunnelling sequence TS. Due to different tunnelling sequences, the apparent losses of pile capacity were 40% and 29% for sequences ST and TS, respectively. Although the computed reductions in normal stress acting on the pile induced by twin tunnelling were almost the same in tests TS and ST, tunnelling near the pile toe induced a larger decrease in the end-bearing and shaft resistances at the lower part of the pile in test ST than in test TS. In contrast to the measured pile head settlements, different tunnelling sequences had a limited effect on measured ground surface settlements and additional bending moments in the pile.

Surface Settlements Caused by Three-Bench Seven-Step-Excavation of Large Span Twin Tunnels

2015 ◽  
Vol 744-746 ◽  
pp. 988-991
Author(s):  
Li Yan ◽  
Jun Sheng Yang ◽  
Kang Nan
Keyword(s):  
Cross Section ◽  
Ground Surface ◽  
Weak Rock ◽  
Construction Time ◽  
Large Span ◽  
Cross Section Area ◽  
Section Area ◽  
Weak Rock Mass ◽  
Surface Settlements ◽  
Twin Tunnels

As a new method, the three-bench seven-step-excavation method is more and more adopted by the construction of large span tunnel in weak rock mass. At the portal of Yunyangshan tunnel, there is a long section of the mild clay stratum. Considered that the whole excavated cross section area is very large, the three-bench seven-step-excavation method was adopted. In order to investigate the surface settlements caused by the construction of twin tunnels, three typical cross-section were selected. At each section, the ground surface settlements were monitored. It is shown that the depth of tunnel and the construction time of twin tunnels have influence on the surface settlement curves, and the three-bench seven-step-excavation is effective in the mild clay stratum.

Neural network based prediction of ground surface settlements due to tunnelling

2001 ◽  
Vol 28 (6-7) ◽  
pp. 517-547 ◽  
Author(s):  
C.Y. Kim ◽  
G.J. Bae ◽  
S.W. Hong ◽  
C.H. Park ◽  
H.K. Moon ◽  
...  
Keyword(s):  
Neural Network ◽  
Ground Surface ◽  
Surface Settlements

Displacements around Two Closely Adjacent Circular Openings

2012 ◽  
Vol 170-173 ◽  
pp. 1397-1401
Author(s):  
Li Yan ◽  
Jun Sheng Yang
Keyword(s):  
Boundary Condition ◽  
Deformation Mechanism ◽  
Ground Deformation ◽  
Ground Surface ◽  
Deformation Pattern ◽  
Measured Field ◽  
Ground Loss ◽  
Computer Package ◽  
Convergence Model ◽  
Surface Settlements

Deformations of the tunnels may results in settlements of the ground surface. Based on the characters of deformation of twin closely adjacent tunnels excavated, a basic deformation mechanism of two parallel tunnels constructed close together was present, which is not uniform but oval-shaped ground deformation pattern and represent the ground loss occurred during construction of the tunnels. An improved convergence model of the tunnel boundary for twin closely adjacent tunnels and the related expressions are proposed. Using a computer package FLAC2D, the certain given deformations as the boundary condition were applied to the boundaries of two tunnels, and the surface settlements caused by the excavation of two tunnels were obtained. It is found that the results match well with the measured field results.

Surface settlement during shield tunnelling at CH218 in Taipei

1998 ◽  
Vol 35 (1) ◽  
pp. 159-168 ◽  
Author(s):  
Chang-Yu Ou ◽  
Richard N Hwang ◽  
Wei-Jung Lai
Keyword(s):  
Ground Surface ◽  
Earth Pressure ◽  
Surface Settlement ◽  
Pressure Balance ◽  
Transit System ◽  
Ground Surface Settlement ◽  
Earth Pressure Balance Shield ◽  
Shield Tunnelling ◽  
Earth Pressure Balance ◽  
Twin Tunnels

This paper presents the surface settlement performance induced by the foamed type of earth pressure balance shield in contract CH218 of the Hsintien Line of the Taipei Rapid Transit System. The surface settlement characteristics caused by the single tunnel and by twin tunnels with reference to two sections spaced at 87 m are studied. Field observations indicate that the surface settlement trough due to the single tunnel can be represented by the normal distribution. The distance of the inflection point to the tunnel center and maximum surface settlement value are consistent with those found in the literature. The characteristics of the surface settlement trough are related to the type of the soil, particularly where the crown of the tunnel is located in a layered soil deposit. The ground surface settlement induced by twin tunnels was found to be larger than estimated using the principle of superposition.Key words: shield tunnelling, surface settlement, field observation.

Optimization Analysis of Different Excavation Offsets in Railway Pilot Tunnel by CRD Method

2014 ◽  
Vol 505-506 ◽  
pp. 134-138
Author(s):  
Chun Kui Li
Keyword(s):  
Production Efficiency ◽  
Ground Surface ◽  
Simulation Method ◽  
Subway Station ◽  
Optimization Analysis ◽  
Tunnel Excavation ◽  
Construction Model ◽  
Surface Settlements ◽  
Stress Variations ◽  
Optimal Construction

This paper focuses on the construction of 10 railway pilot tunnels by CRD method in Jiefang Road subway station in Changchun. To achieve the optimal construction offsets during the pilot tunnel excavation, reduce the impacts of group cavern effect, and maximize the production efficiency, the construction model of railway pilot tunnel in subway station was created by the finite difference software Flac3D. The author used the numerical simulation method to analyze the ground surface settlements and the stress variations with three different construction offsets. Then the optimal construction offset was obtained. It could provide a theoretical guidance to the construction of a similar project.

scholarly journals Design Analysis and Observed Performance of a Tieback Anchored Pile Wall in Sand

2017 ◽  
Vol 2017 ◽  
pp. 1-23 ◽  
Author(s):  
Jian-Yong Han ◽  
Wen Zhao ◽  
Yang Chen ◽  
Peng-Jiao Jia ◽  
Yong-Ping Guan
Keyword(s):  
Design Process ◽  
Case History ◽  
Design Procedure ◽  
Ground Surface ◽  
Deep Excavation ◽  
Construction Methods ◽  
Construction Risk ◽  
European Code ◽  
Practical Guidelines ◽  
Surface Settlements

This paper aims to study the design process and service performance of a deep excavation supported by tieback anchored pile walls. The design procedure and design approaches for deep excavation in China are described. Based on the excavation case history for Shenyang, China, design results obtained using the elastic method and the finite element method (FEM) are compared and analyzed. Special emphasis is given to the analysis of horizontal wall deformations, internal forces in the wall, earth pressures on the wall, ground surface settlements, and stabilities of the excavation. The similarities and differences between the Chinese code (JGJ 120-2012) and the European code (EN 1997-1) for the design of geotechnical structures are presented based on a design example. Through the comparison, it is indicated that the Chinese code focuses on the design result, while the European code focuses on the design process. The crucial construction methods for reducing construction risk based on the excavation case history are described. The mechanical behaviors of the excavation retained by an anchored pile wall were investigated by analyzing observed field cases. The results provide good, practical guidelines for the design and construction of a tieback anchored pile wall retained excavation in sandy soil.

Field Performance of a Deep Multi-Strutted Excavation in Hangzhou Soft Clays

2011 ◽  
Vol 243-249 ◽  
pp. 2324-2327
Author(s):  
Hong Wei Ying ◽  
Yong Wen Yang ◽  
Xin Yu Xie
Keyword(s):  
Large Scale ◽  
Soft Soil ◽  
Soft Clay ◽  
Ground Surface ◽  
Field Performance ◽  
Soft Clays ◽  
Soil Clays ◽  
History Of ◽  
Creep Deformations ◽  
Surface Settlements

A case history of a deep multi-strutted soft clay excavation in Hangzhou is presented in this paper. What makes it particular interest is its three characteristics: large scale, deep excavation and very soft clays. The excavated area was about 99750 square meters. The depth of excavation was 12.85 m. 4 m below the ground surface located about 24 m very soft soil clays. Wall deflections and ground settlements were measured and compared with similar case histories worldwide. It was shown that the maximum horizontal deformations of the excavation was very large which this excavation reached to 220 mm. “Creep” deformations occurred apparently during the curing of the bottom slab of the basement. The distributions of the surface settlements seemed to be parabolic, and the settlement influence zone could reach to a distance of more than 2H, whereHis the final excavation depth. The ratio between the maximum ground settlement and the maximum horizontal deformation of the wall is about 0.6.

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