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.

scholarly journals Effect of Geometric Parameters and Construction Sequence on Ground Settlement of Offset Arrangement Twin Tunnels

Geosciences ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 41
Author(s):  
Md Shariful Islam ◽  
Magued Iskander
Keyword(s):  
Three Dimensional ◽  
Ground Surface ◽  
Geometric Parameters ◽  
Horizontal Distance ◽  
Ground Settlement ◽  
Construction Sequence ◽  
Settlement Behavior ◽  
Total Settlement ◽  
Three Dimensional Finite Element ◽  
Twin Tunnels

A parametric study that examines the ground surface settlement due to the excavation of shallow offset arrangement twin tunnels is presented. Offset arrangement tunnels are those that run parallel to each other, but at different elevations. The study focuses on the influence of both the construction sequence and various geometric parameters on the induced soil settlement. A series of three-dimensional finite element analyses was carried out to investigate the settlement behavior and interactions between offset arrangement twin tunnels excavated in clay using a simplified mechanized excavation method. Analyses were carried out for three cover-to-diameter (C/D) ratios, three possible construction sequences, five angular relative positions, and five angular spacings. In addition, settlement data were also investigated by varying horizontal and vertical spacings while keeping the angular spacing constant. The total settlement of the excavated twin tunnels and the settlement induced solely by the new second tunnel are both presented, and special attention was paid to identifying the dominant geometric parameters. The observed data trends from this study are generally consistent with the limited data available in the literature. This study confirmed a few perceived behaviors. First, angular relative position better describes the settlement behavior in comparison to angular spacing. Second, the effect of the vertical distance is noticeably more significant than that of the horizontal distance between the two tunnels. Third, excavation of the lower tunnel at first induces higher total ground settlement than when the upper tunnel is excavated first or when both tunnels are excavated concurrently. Fourth, settlement due to the construction of the newer tunnel decreases with the increase in the cover depth. In addition, two design charts have been proposed to calculate the settlement induced from a new second tunnel excavation and the eccentricity of the maximum total settlement relative to the center of the new tunnel.

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.

Studies for Deformation of Slurry Shield Construction under Across and Parallel Existing Tunnel

2012 ◽  
Vol 204-208 ◽  
pp. 1435-1438
Author(s):  
Yong Qi Ma ◽  
Yin Ning ◽  
Yi Dong ◽  
Feng Lin Wu
Keyword(s):  
Three Dimensional ◽  
Ground Surface ◽  
Initial Position ◽  
Practical Significance ◽  
Engineering Construction ◽  
Dimensional Finite Element ◽  
Survey Results ◽  
Three Dimensional Finite Element ◽  
Slurry Shield ◽  
Surface Settlements

The method combining the construction survey and the numerical simulation is proposed in the paper to accurately obtain the deformation of the slurry shield construction under across and parallel existing tunnel. The surface settlements of the engineering construction initial position are surveyed. The reliability of the three dimensional finite element models is verified by comparing with the survey results. The deformation variation of the existing tunnel and ground surface are obtained by the elastoplasticity nonlinear calculations, showing the feasibility and effectiveness of the proposed method and the credibility and accuracy of the calculated results. Meanwhile, the measures of control deformation are presented. The surveyed settlements after the construction process of implementing measures are smaller than those calculated, indicating the effect obviously of the measures which has practical significance.

The Vertical and Horizontal Displacements of Cross-river Twin-tunnels Surroundings Induced by Tunneling

2018 ◽  
Author(s):  
Lin Wu ◽  
Zhihua Zhang ◽  
Xiedong Zhang ◽  
FaJin Lin
Keyword(s):  
Three Dimensional ◽  
Great Influence ◽  
Scale Model ◽  
Soil Arching ◽  
Tunnel Excavation ◽  
Large Cities ◽  
Vertical Displacements ◽  
The Difference ◽  
Twin Tunnels ◽  
Horizontal Displacements

<p>Twin-tunnels are widely constructed in large cities because of their many advantages. The first tunnel (named tunnel_1) constructed before a period time than the second tunnel (named tunnel_2) which is to reduce the disturbance between twin-tunnels. In this paper, a three-dimensional scale model of twin-tunnels is established utilizing the discrete element method (DEM) with PFC3D, this model aims to investigate the difference of the vertical displacements and the horizontal displacements of the surroundings in construction process. The numerical results indicate that the peak vertical and horizontal displacements of the surroundings around tunnel_2 are larger than those around tunnel_1. The vertical and horizontal displacements of particles decrease with the distance from the out edge of the twin-tunnels shield lining increases. The existence and evolution of soil arching during tunneling process exert great influence on the stress state and deformation of twin-tunnels surroundings. The peak horizontal displacements are larger in the lateral points of twin-tunnels, while the peak vertical displacements are larger in the vault and bottom points, the tunnel excavation leads the particles around the twin-tunnels move to new location to achieve new equilibrium state. The peak vertical and horizontal displacements occur in own tunnel excavation process, whereas the adjacent tunnel construction affects the displacements as well. The excavation and existence of tunnel_1 have magnified effect on the vertical and horizontal displacements of tunnel_2.</p>

Effects of twin-tunnel excavation on an existing horseshoe-shaped tunnel considering the influence of a settlement joint

2017 ◽  
Vol 54 (9) ◽  
pp. 1346-1355 ◽  
Author(s):  
Biao Jiang ◽  
Li’ang Chen ◽  
J.S. Yang ◽  
Shuying Wang ◽  
C.W.W. Ng
Keyword(s):  
Numerical Analysis ◽  
Adverse Effects ◽  
Transverse Direction ◽  
Three Dimensional ◽  
Ground Surface ◽  
Longitudinal Direction ◽  
Middle Section ◽  
Tunnel Excavation ◽  
Twin Tunnel ◽  
Centrifuge Tests

In urban centres, the construction of a new tunnel would cause ground disturbance and affect any adjacent existing tunnel. Tunnel–tunnel interaction problems have not yet been comprehensively studied. In particular, the response of an existing horseshoe-shaped tunnel to the construction of two perpendicularly undercrossing tunnels remains unclear. In this study, three-dimensional centrifuge tests and three-dimensional numerical analysis were designed and conducted in dry sand to investigate the effects of twin-tunnel undercrossing on an existing horseshoe-shaped tunnel considering the influence of a settlement joint. It is found that the adverse effects caused by the tunnel excavated later were smaller than those by the earlier one. For the existing tunnel without a settlement joint, the settlement at the invert and crown along the longitudinal direction showed sagging and hogging curves, respectively, owing to significant vertical elongation of the middle section. The presence of a settlement joint resulted in an increase in the settlement of the ground surface and the existing tunnel by over 100%. In both cases, larger bending strains were induced in the transverse direction than in the longitudinal direction, particularly around the corners.

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.

Characteristics of wall deflections and ground surface settlements in Shanghai

2005 ◽  
Vol 42 (5) ◽  
pp. 1243-1254 ◽  
Author(s):  
Zhong W Wang ◽  
Charles WW Ng ◽  
Guo B Liu
Keyword(s):  
Similar Case ◽  
Soft Clay ◽  
Three Dimensional ◽  
Ground Surface ◽  
Maximum Displacement ◽  
Aspect Ratios ◽  
Surface Settlements ◽  
Shanghai Metro ◽  
Corner Effects ◽  
Ground Settlements

The characteristics of wall deflections and surface ground settlements at six deep multi-strutted excavations in Shanghai soft soils were studied and compared with those of similar case histories reported worldwide, particularly in Taipei and Singapore. The measured wall deflections at the six metro stations of the Pearl II Circle Line show a typical bulging profile (or deep-seated shape) at the end of the excavation. The ratio between the measured maximum wall deflection and the depth of the excavation (δhm /H) in Shanghai was <0.007, which was similar to the ratio measured in Taipei, but it was substantially smaller than the Peck bounding limit of 0.01. At each station, the measured maximum displacement was <0.45% of the final excavation depth. Because of the large aspect ratios of the underground excavations, no significant three-dimensional effects or corner effects were observed. The measured maximum settlements of the six metro excavations fell within zone I of the Peck classical normalized settlement-distance chart. These small measured settlements were consistent with the small measured wall deflections. The observed relatively small maximum wall deflections can likely be attributed to the use of prestressed struts, the constant adjustment of the stresses to about 0.7 times the total vertical stress during the excavation, and the short horizontal span of the excavation.Key words: multi-strutted excavations, soft clay, Shanghai, metro stations, horizontal deflection, settlement.

scholarly journals The Effect of Loading Type on the Amount of Effect of Loading on the Surface Settlement During Forepoling Tunnel Excavation in Different Geotechnical Conditions

2020 ◽  
Vol 10 (1) ◽  
pp. 55-60
Author(s):  
H. Norouzi
Keyword(s):  
Urban Areas ◽  
Ground Surface ◽  
Surface Settlement ◽  
Residential Areas ◽  
Tunnel Excavation ◽  
Good Opportunity ◽  
Partially Saturated ◽  
Surface Settlements ◽  
Static And Dynamic Loading ◽  
Unique Relationship

AbstractAmong the important phenomena caused by tunnel excavations, the settlements on the ground surface can be mentioned, which are particularly important for shallow tunnels excavated in urban areas, and especially when passing under residential areas of cities. Numerous methods such as mathematical (numerical and analytical) ones can be used to predict surface settlement. This study was conducted aimed at using modern techniques such as artificial neural networks to analyze the parameters affecting the occurrence of surface settlement during forepoling tunnel excavation. Tabriz Subway project is a good opportunity to examine the effect of forepoling tunnel excavation the surface settlement in a granular soil with average groundwater level offers. None of the performance parameters (such as the features of the forepoling protective umbrella) and the environmental features (such as the geological effects and tunnel geology) establish a unique relationship with the surface settlement, but several factors together do so. In this study, the forpolling tunnel was modeled using Plaxis software and analyzed in various geotechnical conditions (drained, partially saturated and saturated) under static and dynamic loading. Finally, the values of the surface settlements were examined.

scholarly journals Hyperspectral Three-Dimensional Fluorescence Imaging Using Snapshot Optical Tomography

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3652
Author(s):  
Cory Juntunen ◽  
Isabel M. Woller ◽  
Yongjin Sung
Keyword(s):  
Fourier Transform ◽  
3D Imaging ◽  
Optical Tomography ◽  
Three Dimensional ◽  
High Spectral Resolution ◽  
Functional Information ◽  
Fluorescent Beads ◽  
Different Depths ◽  
Projection Images ◽  
Imaging Performance

Hyperspectral three-dimensional (3D) imaging can provide both 3D structural and functional information of a specimen. The imaging throughput is typically very low due to the requirement of scanning mechanisms for different depths and wavelengths. Here we demonstrate hyperspectral 3D imaging using Snapshot projection optical tomography (SPOT) and Fourier-transform spectroscopy (FTS). SPOT allows us to instantaneously acquire the projection images corresponding to different viewing angles, while FTS allows us to perform hyperspectral imaging at high spectral resolution. Using fluorescent beads and sunflower pollens, we demonstrate the imaging performance of the developed system.

Sign in / Sign up

Export Citation Format

Share Document