scholarly journals An Investigation of Effects and Safety of Pipelines due to Twin Tunneling

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Shao Yu ◽  
Riyan Lan ◽  
Junhui Luo ◽  
Zhibo Duan ◽  
Shaokun Ma
Keyword(s):  
Soil Parameters ◽  
Centrifuge Model Test ◽  
Burial Depth ◽  
Buried Pipelines ◽  
Soil Stiffness ◽  
Maximum Settlement ◽  
Dimensionless Analysis ◽  
Bending Strain ◽  
Calculation Results ◽  
Subway Tunnels

To efficiently and accurately predict the effects of twin tunneling on adjacent buried pipelines, the effects of upward and downward relative pipeline-soil interactions were considered. A series of numerical parametric studies encompassing 8640 conditions were performed to investigate the responses of a pipeline to twin tunneling. Based on the dimensionless analysis and normalized calculation results, the concept of equivalent relative pipeline-soil stiffness was proposed. Additionally, expressions for the relative pipeline-soil stiffness and relative pipeline curvature and for the relative pipeline-soil stiffness and relative pipeline settlement were established, along with the related calculation plots. Relying on a comparison of prediction results, centrifuge model test results, and field measured results, the accuracy and reliability of the obtained expressions for predicting the bending strain and settlement of adjacent buried pipelines caused by twin tunneling were validated. Based on the calculation method, the maximum bending strain and maximum settlement of pipelines can be calculated precisely when the pipeline parameters, burial depth, soil parameters, and curve parameters of ground settlement due to tunneling are provided. The proposed expressions can be used not only to predict the maximum bending strain and maximum settlement of pipelines caused by single and twin tunneling but also to evaluate the effects of single and twin tunneling on the safety of existing buried pipelines. The relevant conclusions of this article can also provide a theoretical basis for the normal service of buried pipelines adjacent to subway tunnels.

Numerical modeling of tunneling effect on buried pipelines

2011 ◽  
Vol 48 (7) ◽  
pp. 1125-1137 ◽  
Author(s):  
Yu Wang ◽  
Jiangwei Shi ◽  
Charles W.W. Ng
Keyword(s):  
Urban Areas ◽  
Ground Movement ◽  
Tunneling Effect ◽  
Burial Depth ◽  
Test Results ◽  
Soil Stiffness ◽  
Bending Strain ◽  
Versus Ratio ◽  
Parametric Studies ◽  
Soil Responses

The underground space in urban areas is frequently congested with utilities, including pipelines and conduits, that are affected by underground construction, e.g., tunneling. This paper carries out finite element (FE) analyses to investigate the effects of tunneling-induced ground movement on pipelines, with special attention to the different soil responses to uplift and downward pipe–soil relative movements. A series of numerical parametric studies with 900 FE simulation runs in total is performed to encompass various combinations of ground settlement profiles, pipe dimensions, material properties, pipe burial depth, and soil properties that are typical for utility pipelines and tunnel construction in urban areas. The results are summarized in a dimensionless plot of relative pipe–soil stiffness versus ratio of maximum pipe curvature to maximum ground curvature, which can be used to directly estimate the maximum pipe bending strain and (or) to directly assess the tunneling-induced risk to pipelines. The FE results and dimensionless plot are validated against field and centrifuge test results reported in the literature. Effect of pipeline orientation with respect to the tunnel centerline is explored. It might be unconservative if design analysis only considers the case that the pipeline is perpendicular to the tunnel centerline.

Study on the Stratum Displacement Changes Caused by the Vertical Shaft Construction in Saturated Ultra Soft Soil

2012 ◽  
Vol 170-173 ◽  
pp. 1005-1012
Author(s):  
Lin You Pan ◽  
Xiao Bing Li ◽  
Chuang Yu ◽  
Fu Xue Sun
Keyword(s):  
Soft Soil ◽  
Field Tests ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
Soil Disturbance ◽  
Soil Parameters ◽  
Finite Element Software ◽  
Total Displacement ◽  
Calculation Results ◽  
Engineering Information

In view of Wenzhou saturated super soft soil, This article studied the influence of different soil parameters for the shaft excavation construction and the stratum displacement change law by using Plaxis finite element software, according to the data obtained in field tests. The considered factors included the lateral brace stiffness, the stiffness of the underground diaphragm wall, and the surrounding soil disturbance. The calculation results provided much important engineering information, such as the horizontal displacement nephogram, the vertical displacement nephogram and the total displacement incremental vector diagram of each construction steps, which can be referred for the construction of the similar underground projects in soft soil areas.

scholarly journals Ground deformation mechanism due to deep excavation in sand: 3D numerical modelling

2021 ◽  
Vol 9 (6) ◽  
pp. 741-747
Keyword(s):  
Relative Density ◽  
Deformation Mechanism ◽  
Ground Deformation ◽  
Ground Movement ◽  
Soil Stiffness ◽  
Maximum Settlement ◽  
Hypoplastic Model ◽  
3D Numerical Modelling ◽  
Path Dependent ◽  
Underground Transportation

In densely built areas, development of underground transportation system often involves excavations for basement construction and cut-and-cover tunnels which are sometimes inevitable to be constructed adjacent to existing structure. Inadequate support systems have always been major concern as excessive ground movement induced during excavation could damage to neighbouring structure. A detailed parametric analysis of the ground deformation mechanism due to excavation with different depths in sand with different densities (Dr=30%, 50%, 70% and 90%) is presented. 3D finite element analyses were carried out using a hypoplastic model, which considers strain-dependent and path-dependent soil stiffness. The computed results have revealed that the maximum settlement decreased substantially when the excavation is carried out in the sand with higher relative density. This is because of reason that sand with higher relative density possesses higher stiffness. Moreover, the depth of the maximum settlement of the wall decreases as the sandbecome denser.The ground movement flow is towards excavation in retained side of the excavation. On the other hand the soil heave was induced below the formation level at excavation side. The maximum strain level of 2.4% was induced around the diaphragm wall.

scholarly journals Investigating the Factors That Reduce the Urban Gas Pipeline Vulnerability to Explosion Threats

2019 ◽  
Author(s):  
Mohammad reza Fallah Ghanbari ◽  
Mohammad Eskandari ◽  
Ali Alidoosti
Keyword(s):  
Soft Soil ◽  
Shell Element ◽  
Friction Angle ◽  
Burial Depth ◽  
Gas Pipelines ◽  
Three Dimensional Model ◽  
Buried Pipelines ◽  
Burial Site ◽  
Pipe System ◽  
Abaqus Software

Introduction: Buried pipelines used to distribute water, gas, oil, and etc. are considered as one of the vital arteries. The experiences of the past wars have confirmed that the invading country focuses on bombing and destroying vital centers, and that gas pipelines can be a source of serious personal and financial losses as an important transmission arteries during war in the event of damage Methods: The vulnerability of buried urban gas pipelines to explosion was determined and the methods for reducing the vulnerability of pipelines were investigated. To this end, the three-dimensional model of the soil-pipe system in ABAQUS software was used to study the effect of factors affecting the pipe behavior, including pipe diameters, diameter to pipe thickness, internal friction angle of soil, soil type, amount of explosives, depth of buried, the distance of explosion site to the pipe burial site, has been investigated on the pipe deformation capacity according to the ALA regulation. The soil was modeled using Solid three elements and shell element. For parametric studies, analyses were performed by the finite element method using ABAQUS software 6.10.1. Results: Studies were conducted for 4 and 12 inch diameter, diameter/thickness ratio of 26, 21 and 35, burial depth of 1, 2, 3 and 4 meters, the explosive charge of 15, 30, 45, 60 and 200 kg TNT and for soil material, hard, soft and clay sands. The results showed that proper burial depth had the most effect in reducing the vulnerability of pipelines against explosive threats. By increasing the pipe thickness and increasing the diameter and applying soft soil around the pipe, a better behavior of the pipe was observed during the explosion Conclusion: To reduce the vulnerability of gas pipelines against explosive threats, the use of buried pipelines has a greater effect on reducing damage due to explosion compared to other parameters, and it is recommended to use this method to increase the resilience of highly important gas pipelines.

scholarly journals A Precise Prediction of Tunnel Deformation Caused by Circular Foundation Pit Excavation

2019 ◽  
Vol 9 (11) ◽  
pp. 2275 ◽  
Author(s):  
Huasheng Sun ◽  
Lingwei Wang ◽  
Shenwei Chen ◽  
Hengwei Deng ◽  
Jihua Zhang
Keyword(s):  
Engineering Practice ◽  
Foundation Pit ◽  
Retaining Structures ◽  
Soil Stiffness ◽  
Circular Excavation ◽  
Nonlinear Constitutive Model ◽  
Bending Strain ◽  
Precise Prediction ◽  
Path Dependent ◽  
Reasonable Choice

In comparison with tetragonal retaining structures, circular retaining structures have an advantage in terms of controlling the deformation caused by foundation excavation, and are a reasonable choice in engineering practice. Many results have been obtained regarding the effect of tetragonal excavation on the deformation of an adjacent tunnel. Nevertheless, a sufficient understanding of the circular excavation’s effect on the deformation of an adjacent tunnel is currently lacking. Therefore, this study focused on the problem of precise predicting tunnel deformation below a circular excavation. A numerical model was established to calculate the tunnel deformation caused by the circular excavation. An advanced nonlinear constitutive model, known as a hypoplasticity model, which can capture path-dependent and strain-dependent soil stiffness even at small strains, was adopted. The models and their associated parameters were calibrated by centrifuge test results reported in the literature. The deformation mechanism was revealed, and the calculated results were compared with those obtained with a square excavation and the same excavation amount. The differences between the deformations caused by these two types of excavation shapes were analyzed. It was found that under equal excavation area conditions, the excavation-induced deformations of the metro tunnel below a circular excavation were approximately 1.18–1.22 times greater than those below a square excavation. The maximum tunnel tensile bending strain caused by the circular excavation was 32% smaller than that caused by the square excavation. By comparing with the measured results, it is proved that the proposed numerical method can provide effective reference for engineers to analyze soil-structure problems.

scholarly journals Seismic Behaviour of Buried Pipelines: 3D Finite Element Approach

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Smrutirekha Sahoo ◽  
Bappaditya Manna ◽  
K. G. Sharma
Keyword(s):  
Finite Element ◽  
Seismic Response ◽  
Ground Deformation ◽  
Seismic Wave Propagation ◽  
Pipe Diameter ◽  
Bend Angle ◽  
Burial Depth ◽  
Maximum Magnitude ◽  
Buried Pipelines ◽  
Seismic Behaviour

This paper presents a numerical investigation on six pipeline models to study the seismic response of single and double buried pipelines using finite element method. Different depth and spacing of pipes are considered to investigate their prominent role in the seismic response of buried pipelines under an earthquake loading having PGA of 0.2468 g. In case of single pipeline, the maximum magnitude of final displacement as well as the stress at the end of the seismic sequence is found at the burial depth equal to the pipe diameter. In case of double pipeline, the maximum magnitude of final displacement is found when the spacing between pipes is equal to half the pipe diameter and there is an increasing tendency of developed stress with increase in spacing between pipes. In addition to the above results, the response of the buried pipelines with a particular bend angle (artificially induced bend/buckle) to the permanent ground deformation which is assumed to be the result of seismic wave propagation has also been studied. Remarkable differences in these results are obtained and with these results the designers can reduce seismic risk to their buried pipelines by taking proper precautionary measures.

Analysis and Design of Buried Pipelines for Ice Gouging Hazard: A Probabilistic Approach

2006 ◽  
Vol 129 (3) ◽  
pp. 219-228 ◽  
Author(s):  
Arash Nobahar ◽  
Shawn Kenny ◽  
Tony King ◽  
Richard McKenna ◽  
Ryan Phillips
Keyword(s):  
Probabilistic Approach ◽  
Three Dimensional ◽  
Local Buckling ◽  
Burial Depth ◽  
The Finite Element Method ◽  
Buried Pipelines ◽  
Analysis And Design ◽  
Cold Environments ◽  
Beam Elements ◽  
Environmental Actions

In cold environments, marine pipelines may be at risk from ice keels that gouge the seabed. Large quantities of material are displaced and soil deformations beneath a gouge may be substantial. To meet safety criteria, excessive strains are avoided by burying pipelines to a sufficient depth. In this paper, a probabilistic approach for the analysis and design of buried pipelines is outlined. Environmental actions are applied through distributions of gouge width, gouge depth, subgouge soil deformations, and bearing pressure. Three-dimensional pipe/soil interaction problem is modeled using nonlinear soil springs and special beam elements using the finite element method to estimate pipe response for statistically possible ranges of gouge depths, gouge widths, and burial depths. Relevant failure mechanisms have been considered, including local buckling and a variety of strain and stress based criteria. The methodology presented in the paper was developed and successfully used for several pipeline and electrical cable projects in ice gouge environments. Significantly reduced burial depth requirements have been demonstrated through the application of the probabilistic approach and through the use of strain-based design criteria. Because ice actions are applied through displacements of the soil, more ductile pipes are often necessary to meet reliability targets.

scholarly journals Determination of p-y curves for offshore piles based on in-situ soil investigations

2018 ◽  
Vol 219 ◽  
pp. 05003
Author(s):  
Kamila Międlarz ◽  
Lech Bałachowski
Keyword(s):  
Field Tests ◽  
Soil Parameters ◽  
Lateral Loads ◽  
Cohesionless Soils ◽  
In Situ Tests ◽  
Soil Stiffness ◽  
Soil Response ◽  
Direct Design ◽  
Offshore Piles

Offshore piles are subjected to complex loads with considerable lateral component. The pile-soil response to lateral loads can be described with the p-y method. For a given depth the load–deflection relationship is built to simulate the surrounding soil stiffness. This state-of-art paper presents a brief discussion of determination methods for the p-y curves using a standard approach based on the soil parameters derived from laboratory and in-situ tests or directly from field tests. The basic relationships for both cohesive and cohesionless soils are discussed. The advantage of direct design methods to describe the p-y curve relies in the reduction of necessary laboratory tests.

scholarly journals Numerical Modeling of Pipe-Soil Interaction Under Transverse Direction

2014 ◽  
Author(s):  
Bahar Farhadi ◽  
Ron C. K. Wong
Keyword(s):  
Finite Element ◽  
Transverse Direction ◽  
Soil Parameters ◽  
Burial Depth ◽  
Soil Behavior ◽  
Finite Element Software ◽  
Failure Envelopes ◽  
Winkler Method ◽  
Pipe Deflection ◽  
Resultant Forces

Based on the Winkler method, a pipe can be treated as a beam, and pipe-soil interactions can be represented by soil springs in the axial, horizontal and vertical directions. Pipe deflection and resultant forces are correlated by coefficient K in the equation F=Kδ, where F is the resultant force and δ is the pipe displacement. This paper studies pipe-soil interaction for pipelines buried in clay and sand subjected to displacements in oblique directions. The objective is to measure the effect of soil parameters on coefficient K as well as the maximum soil resistance. Pipe-soil behavior has been studied using the finite element software ABAQUS/CAE. There are 48 models in total with varying soil parameters, pipe burial depth and pipe-soil interaction friction for the investigation of the effect of each variable on pipe-soil behavior. In addition, the finite element results have been compared to the analytical results from American Lifelines Alliance guideline (ALA, 2001) and proposed failure envelopes in previous studies.

scholarly journals Model Test Study on the Influence of Ground Surcharges on the Deformation of Shield Tunnels

Symmetry ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1565
Author(s):  
Gang Wei ◽  
Shuming Zhang ◽  
Pengfei Xiang
Keyword(s):  
Model Test ◽  
Three Dimensional ◽  
Theoretical Method ◽  
Shield Tunnel ◽  
Burial Depth ◽  
Scaled Model ◽  
Test Study ◽  
Dimensional Finite Element ◽  
Calculation Results ◽  
Three Dimensional Finite Element

Aiming at studying the harm caused by sudden ground loadings on existing shield tunnels, a indoor scaled model test with a geometric similarity ratio of 1:15.5 was adopted. Considering the influencing factors such as ground loading, burial depth of the shield tunnel, loading position and soil properties, tunnel convergence deformation, tunnel settlement and deep settlement of soil caused by sudden ground loadings are studied. A three-dimensional finite element simulation is carried out using the Midas software, and deep settlement of soil is calculated by a theoretical method. The purpose of this model test is to further understand the influence of ground surcharges on shield tunnel deformation. The results show that the greater the ground surcharge, the greater the settlement and vertical convergence deformation of the shield tunnel; The further away from the ground surcharge, the smaller the settlement, vertical convergence deformation and lateral convergence deformation of the tunnel. When the pile load size is constant, the greater the burial depth of the tunnel, the smaller the vertical convergence deformation and settlement of the tunnel; the maximum value of deep settlement of the soil always remains at the closest point to the ground surcharge; compared with the use of dry sand, the vertical convergence deformation and settlement of the tunnel are significantly reduced when using wet sand. Both the theoretical calculation results and the numerical simulation results are in good agreement with the indoor model test results.

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