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.

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.

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.

scholarly journals The Ground Settlement and the Existing Pipeline Response Induced by the Nonsynchronous Construction of a Twin-Tunnel

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Shicheng Sun ◽  
Chuanxin Rong ◽  
Houliang Wang ◽  
Linzhao Cui ◽  
Xin Shi
Keyword(s):  
Three Dimensional ◽  
Ground Surface ◽  
Construction Process ◽  
Ground Settlement ◽  
Three Dimensional Model ◽  
Relative Stiffness ◽  
Twin Tunnel ◽  
Calculation Results ◽  
Negative Impacts ◽  
Final Settlement

Shielding tunnel construction always has negative impacts on the surrounding buildings. Because of repeated disturbances caused by the construction, more attention should be paid to the impacts of the nonsynchronous construction of a twin-tunnel. In this research, a three-dimensional model was established to simulate the construction process of a twin-tunnel in a section of the Hefei No. 4 metro line, and the calculation results were validated with the measured settlement data. Based on the model, the ground settlement and the existing pipeline responses were studied in detail. The results showed that, after the first tunnel (FT) construction, the settlement curves conformed to a Gaussian distribution. Additionally, after the second tunnel (ST) construction, the final settlement curves were no longer completely symmetrical. The influences of the twin-tunnel space and the pipeline-soil relative stiffness on the settlements were further studied. The results showed that the final settlement curves of the ground surface and the pipeline were mainly W-shaped, U-shaped, and V-shaped. As the twin-tunnel space increased and the pipeline-soil relative stiffness decreased, the settlement curve gradually changed from V-shaped to W-shaped. C was defined as the ratio of two maximum settlements in the W-shaped settlement curve. As the space increased, C started to decrease from 1 and then increased to 1.

Three Dimensional Numerical Analysis of Ground Settlement Induced by Shield Tunneling

2012 ◽  
Vol 182-183 ◽  
pp. 937-940
Author(s):  
Zhong Chang Wang
Keyword(s):  
Soil Layer ◽  
Three Dimensional ◽  
Ground Surface ◽  
Vertical Displacement ◽  
Ground Subsidence ◽  
Shield Tunnel ◽  
Ground Settlement ◽  
Shield Tunneling ◽  
Tunnel Face ◽  
Maximum Settlement

The fine numerical simulation is used to study the ground settlement of complex stratum owing to shield construction by ANSYS program. It is shown that the closer the distance between soil layer and the axis of tunnel is, the smaller the disturbance of construction is, the obvious the ground surface settlement is. The value of the maximum settlement at the center of the surface is 7.4mm. The maximum settlement of vault is 14mm. The ground subsidence in cross section distribution is shaped of normal distribution. The closer the distance between soil layer and ground surface is, the smaller the vertical displacement is, the bigger the width of settlement trough of soil layers is. The width of settlement trough is 25m. The volume loss rate of shield tunnel is about 0.32%. The width coefficient of ground settlement trough is 0.56. The tendency of ground settlement decrease to become gentle with the advance of shield construction. The ground settlement keeps constant after tunnel face advancing to 30m.

Simulation and Survey of Stratum Disturbance for Shield Tunneling in Water-Rich Soil Layers

2016 ◽  
Vol 680 ◽  
pp. 486-490
Author(s):  
Huai Liang Zhu ◽  
Li Feng Yu ◽  
L.C. Wei
Keyword(s):  
Hybrid Approach ◽  
Three Dimensional ◽  
Ground Surface ◽  
Survey Method ◽  
Shield Tunneling ◽  
Soil Layers ◽  
Normal Distribution Curve ◽  
Site Survey ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

In this paper, a hybrid approach is presented for modeling the stratum disturbance during the shield construction in water-rich soil. The disturbance mechanism of stratum is analyzed based on the theory of shield excavation. The deformation and settlement of ground surface are simulated by three-dimensional finite element method. Some physical properties and displacements of soil layers are measured by site survey method. The transverse settlement trough of tunnel is a normal distribution curve and the largest displacement to happen on the above of excavation face. There is also an important influence of shield tunneling on the ground settlement in the longitudinal profile, but this effect disappears a certain distance apart. It is shown that the results based on the numerical simulation and the data from site survey in this work are much rational.

Numerical Analysis on Settlement Law of an Underpinning Structure Composed of Piles and Beams

2010 ◽  
Vol 163-167 ◽  
pp. 3654-3661
Author(s):  
Qiang Jia ◽  
Fang Gu
Keyword(s):  
Three Dimensional ◽  
Element Model ◽  
Frame Structure ◽  
Settlement Location ◽  
Before And After ◽  
Dimensional Finite Element ◽  
Total Settlement ◽  
Width Change ◽  
Three Dimensional Finite Element ◽  
Column Bases

The settlement law during the underpinning process of a frame structure was analysed using the three-dimensional finite element model based on ANSYS program. The birth and death technique was adopted to simulate the work state of the underpinning structure and the underpinned piles. The secondary settlement deformations in the process of foundation underpinning can be simulated when the settlement values of the column bases before underpinning were applied to the underpinning structure. The settlement-location curves of the frame column bases before and after underpinning can be gained through path operation. The analysis results show that the settlement values and the differential settlements of the underpinning location increase obviously after underpinning, the medial deflection of the underpinning beam increases, and the settlement value of corresponding frame becomes bigger. The deformation of the underpinning beam occupys big proportion in the total settlement deformation. When the length diminishes and the diameter augments of the underpinning pile, the stiffness of the pile increases, therefore the settlement values and the differential settlements decrease. When the span diminishes and the height augments of the underpinning beam, the stiffness of the beam increases, accordingly the settlement values and the differential settlements decrease obviously. The width change of the underpinning beam has little influence on the settlement values and the differential settlements.

scholarly journals Three-dimensional Discrete Element Simulation of Interaction between Aqueduct and Tunnel

2021 ◽  
Author(s):  
Vahab Sarfarazi ◽  
Hadi Haeri ◽  
Kaveh Asgari
Keyword(s):  
Three Dimensional ◽  
Ground Surface ◽  
Ground Settlement ◽  
Tunnel Wall ◽  
Geometrical Properties ◽  
Maximum Value ◽  
Element Simulation ◽  
Before And After ◽  
Effect Of Support ◽  
Support Lining

In this investigation the effect of interaction between aqueduct and tunnel on the ground settlement has been examined using PFC3D. At first, the calibration of PFC3D was conducted based on UCS test results rendered from three different ground layer. Then intact model with dimension of 70 m × 20 m × 34.5 m (x × y × z) was built. These models are consisted of 8 layers with different mechanical and geometrical properties. Four different configurations for aqueduct were created in four models. Diameter of aqueduct was 2 m and its depth was different in four models. After aqueduct generation, tunnel with diameter of 9 m and length of 20 m was drilled in depth of 22 m. After tunnel drilling, the settlement data of ground surface were picked up. After tunnel simulation, the effect of support lining was investigated on the ground settlement. For this purpose, after each step of tunnel drilling, lining support with diameter of 35 cm was performed. The results show that the maximum value of settlement occurred when aqueduct reach to head of tunnel. Also the safety has maximum value when the distance between aqueduct and tunnel wall was 4.5 m. the ground settlement before and after support lining shows that ground settlement reach to zero by support application.

Three-dimensional deformation behavior of the Taipei National Enterprise Center (TNEC) excavation case history

2000 ◽  
Vol 37 (2) ◽  
pp. 438-448 ◽  
Author(s):  
Chang-Yu Ou ◽  
Bor-Yuan Shiau ◽  
I-Wen Wang
Keyword(s):  
Finite Element ◽  
Plane Strain ◽  
Case History ◽  
Three Dimensional ◽  
Ground Surface ◽  
Element Analysis ◽  
Case Record ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
National Enterprise

The Taipei National Enterprise Center (TNEC) excavation project was constructed using the top-down construction method, in which a diaphragm wall was supported by the concrete floor slab. Previous studies have reported the deformation and stress-strain behaviors along the main observation section, which was considered to be in the plane strain condition. This paper examines the three-dimensional movements of the soil and wall through field observations and finite element analyses. The results indicate that the soil outside the excavation zone tends to move toward the excavation center. Such a tendency increases with excavation depth. The soil settlement near the corner of the excavation is less than that near the center due to the corner effect. The empirical equation proposed by Clough and O'Rourke for estimating the ground settlement appears to be adequate for plane strain sections and other non-plane strain sections. Numerical studies indicate that the wall deformation and ground surface settlement can be reasonably predicted using three-dimensional finite element analysis. Parametric studies revealed that for this case record zoned excavation commencing near the final stage of excavation has very little effect on excavation behavior.Key words: TNEC case history, deep excavation, deformation, three-dimensional finite element method.

Estimation of Bearing Capacity Dropping Due to Cavities from Gypseous Soils Melting

2020 ◽  
Vol 857 ◽  
pp. 409-416
Author(s):  
Ahmed Al-Obaidi ◽  
Reem S. Najim
Keyword(s):  
Bearing Capacity ◽  
Three Dimensional ◽  
Horizontal Distance ◽  
Finite Element Program ◽  
Significant Movement ◽  
Gypsum Content ◽  
Dimensional Finite Element ◽  
Element Program ◽  
Permeable Soil ◽  
Three Dimensional Finite Element

The presence of gypsum in the soil will cause problems if the source of freshwater is available and permeable soil permitting significant movement of water is to take place. The solubility of gypsum by excess water from irrigation or localized leak into the gypseous soil may cause cavity formation. In this research, a model was developed for governing the mass-transport to assess the variation of gypsum content of the soil during dissolution. A general three-dimensional finite element program (PLAXIS tunnel) was selected for the numerical analysis method to generate the solution. Parameters that affect the bearing capacity of a square footing represented by the gypsum content, the cavity volume, and the location of the cavity which represent by three offset distances from the footing center to the cavity center (x, y, and z), where (X) represents the horizontal distance, (Y) represents the vertical (depth) distance, and (Z) represents the diagonal distance. The main results show that the cavity location found to be the most parameter that affects the bearing capacity ratio (BCR). The minimum values are found when the cavity locates at the center of the footing base, and the lowest one (0.211) when the gypsum dissolved equal to 40%, also there is no effect of the cavity location when the ratio of (X/B) and (Z/B) exceed (3.0) for any depth and when the gypsum dissolved less than 10%. For high gypsum dissolution (more than 30%), the dimensionless ratios (X/B), (Z/B), and (Y/B) of the cavity must be more than 5.0.

Interpretation of Buried Pipe Test: Small-Diameter Pipe in Ohio University Facility

1996 ◽  
Vol 1541 (1) ◽  
pp. 64-75 ◽  
Author(s):  
R. W. I. Brachman ◽  
I. D. Moore ◽  
R. K. Rowe
Keyword(s):  
Three Dimensional ◽  
Small Diameter ◽  
Ground Surface ◽  
Horizontal Stress ◽  
Test Cell ◽  
Real Field ◽  
Ohio University ◽  
Buried Pipe ◽  
Soil Failure ◽  
Three Dimensional Finite Element

Two- and three-dimensional finite-element analyses were used to examine the response of a small-diameter leachate collection pipe tested at Ohio University. The influence of the cell boundaries was examined, and the implications of the loading system were investigated. The state of stress in the soil around the cell was studied, and its influence on the expected soil and pipe responses was evaluated. Comparisons between the pipe response induced in the test cell and that which was expected to occur in a real field installation were also made. It was found that nonuniform vertical and horizontal stress distributions different from those expected in real field installations developed in the test cell. This presents various difficulties associated with interpreting loading as an equivalent height of fill. At low load levels in the test cell the granular backfill adjacent to the pipe yielded as local bending developed under the rigid platform used to apply pressure to the ground surface. The decreased lateral support altered the mode of pipe deflection. At high load levels the response in the test cell was governed by soil failure, producing conditions not expected in a landfill environment.

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