Three-Dimensional Response of Buried Pipelines Subjected to Large Soil Deformation Effects: Part II—Effects of the Soil Restraint on the Response of Pipe/Soil Systems

2010 ◽  
Author(s):  
Abdelfettah Fredj ◽  
Aaron Dinovitzer
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Soil Mechanics ◽  
Three Dimensional ◽  
Ground Movement ◽  
Assessment Process ◽  
Pipeline System ◽  
Integrity Assessment ◽  
Soil Systems ◽  
Large Soil

Understanding the effect of soil-pipeline interactions in the event of large ground movement is an important consideration for pipeline designer. Both experimental investigation and computational analyses play significant roles in this research. As part of this effort, a framework incorporating continuum soil mechanics and advanced finite element approach (i.e., ALE and SPH method) for modeling soil pipe interaction is developed. The overall objective is to develop, validate and apply 3D continuum modeling technique to assess the performance of pipeline system subjected to large soil displacement. The numerical models than may be used to predict the wrinkle formation and post formation behavior of the pipeline considering the effect of the soil confinement, and develop a comprehensive wrinkle integrity assessment process. This is the second paper (Part II) in a series of two papers. In the first paper a three-dimensional Continuum models using MM-ALE (Multi-material Arbitrary Eulerian Lagrangian) and SPH (smooth particle hydrodynamics) approaches are developed and run using LS-DYNA. The results are compared with published experimental data of large-scale test to verify the numerical analysis methods. In this paper (Part II) the effects of soil restraint on the response of the pipe/soil systems (e.g., pipeline Wrinkle and buckle, strain demand) are discussed.

Three-Dimensional Response of Buried Pipelines Subjected to Large Soil Deformation Effects: Part I—3D Continuum Modeling Using ALE and SPH Formulations

2010 ◽  
Author(s):  
Abdelfettah Fredj ◽  
Aaron Dinovitzer
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Soil Mechanics ◽  
Three Dimensional ◽  
Ground Movement ◽  
Assessment Process ◽  
Continuum Modeling ◽  
Integrity Assessment ◽  
Particle Hydrodynamics ◽  
Large Soil

Understanding the effect of soil-pipeline interactions in the event of large ground movement is an important consideration for the pipeline designer. Both experimental investigation and computational analyses play significant roles in soil-pipeline research. As part of this effort, a framework incorporating continuum soil mechanics and advanced finite element approach (i.e., ALE and SPH method) for modeling soil pipe interaction was constructed. The overall objective of this work is to develop, validate and apply 3D continuum modeling techniques to assess the performance of pipeline systems subjected to large soil displacements. The numerical models produced may subsequently be used to predict the wrinkle formation and post formation behavior of the pipeline considering the effect of the soil confinement. The aim is to develop a comprehensive wrinkle integrity assessment process. This is the first paper (Part I) in a series of two papers. In this paper a three-dimensional Continuum models using MM-ALE (Multi-material Arbitrary Eulerian Lagrangian) and SPH (smooth particle hydrodynamics) approaches are developed and employed using LS-DYNA. The results are compared with published experimental data of large-scale tests to verify the numerical analysis methods. In the second paper (Part II) the effects of soil restraint on the response of the pipe/soil systems (e.g., pipeline wrinkle and buckle, strain demand) are discussed.

Validation of a Finite Element Toolbox for Studying Flaw Interaction

2020 ◽  
Author(s):  
Harry E. Coules
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Large Scale ◽  
Structural Integrity ◽  
Three Dimensional ◽  
Integrity Assessment ◽  
Linear Elastic ◽  
Wide Range ◽  
Parametric Studies ◽  
Elastic Crack

Abstract Structural integrity assessment often requires the interaction of multiple closely-spaced cracks or flaws in a structure to be considered. Although many procedures for structural integrity assessment include rules for determining the significance of flaw interaction, and for re-characterising interacting flaws, these rules can be difficult to validate in a fracture mechanics framework. int_defects is an open-source MATLAB toolbox which uses the Abaqus finite element suite to perform large-scale parametric studies in cracked-body analysis. It is designed to allow developers of assessment codes to check the accuracy of simplified interaction criteria under a wide range of conditions, e.g. for different interacting flaw geometries, material models and loading cases. int_defects can help analysts perform parametric studies to determine linear elastic crack tip stress field parameters, elastic-plastic parameters and plastic limit loads for simple three-dimensional cracked bodies relevant to assessment codes. This article focusses on the validation of int_defects using existing fracture mechanics results. Through a set of validation examples, int_defects is shown to produce accurate results for a very wide range of cases in both linear and non-linear cracked-body analysis. Nevertheless, it is emphasised that users of this software should be conscious of the inherent limitations of LEFM and EPFM theory when applied to real fracture processes, and effects such as constraint loss should be considered when formulating interaction criteria.

Risk Assessment in Deep Excavations and their Effect on Surrounding Structures : A review

2021 ◽  
Author(s):  
Syed Uzairuddin
Keyword(s):  
Risk Assessment ◽  
Large Scale ◽  
Prediction Models ◽  
Three Dimensional ◽  
Ground Movement ◽  
Deep Foundation ◽  
Deep Excavations ◽  
Ground Deformations ◽  
Theoretical Approaches ◽  
Deep Foundation Excavation

—Construction is crucial to a country's overall economic growth, particularly in developing countries, in the current era of globalization. If construction operations are not carried out strictly according to a local or national building code, they might result in large-scale failures endangering human lives, personnel property, and the economic balance. It is vital to handle the construction process's risk elements. The self weight of soil behind the retaining line is the driving force and shear strength of soil is the resisting force as a result, deep excavations invariably cause lateral and vertical ground deformations. As a result of the produced ground deformations, nearby buildings and utilities become kinetically loaded. Risks associated with ground movement cannot be calculated solely using mathematical predicting models and engineering simulations as it needs to address the uncertainty of soil properties, Geo-materials, ground constitutive nature, building stage modelling, three-dimensional impacts of deep excavations, time-dependent natures of ground deformations, and the critical necessity to include human variables such as craftsmanship into prediction models are all important considerations.This article provides an overview of risk assessment and management technologies and approaches that have been adapted for use in deep excavations. This article presents a review of the most effective methods for evaluating hazards related with deep excavation and current mitigating techniques. Theoretical approaches to enhancing the safety of deep foundation excavation are examined in the context of a hospital building in Khartoum state and a residential district project in southern Jianxi province.

NESC VII: A European Project for Application of WPS in RPV Assessment Including Biaxial Loading

2010 ◽  
Author(s):  
Dominique Moinereau ◽  
Ste´phane Chapuliot ◽  
Ste´phane Marie ◽  
Philippe Gilles
Keyword(s):  
Beneficial Effect ◽  
Brittle Failure ◽  
Large Scale ◽  
Biaxial Loading ◽  
Numerical Models ◽  
Development Program ◽  
Sufficient Evidence ◽  
Load History ◽  
Integrity Assessment ◽  
History Effects

The Reactor Pressure Vessel (RPV) is an essential component liable to limit the lifetime duration of PWR plants. The assessment of defects in RPV subjected to PTS transients made at a European level do not necessarily take into account the beneficial effect of load history (warm pre-stress WPS) on the resistance of RPV material regarding the risk of brittle failure. A 4-year European Research & Development program — SMILE — was successfully conducted between 2002 and 2005 as part of the 5th Framework of the European Atomic Energy Community (EURATOM). The objective of the SMILE project (‘Structural Margin Improvements in aged-embrittled RPV with Load history Effects’) was to provide sufficient evidence in order to demonstrate, to model and to validate the beneficial WPS effect in a RPV integrity assessment. Numerous experimental, analytical and numerical results have been obtained which confirm the beneficial effect of warm pre-stress on RPV steels, with an effective significant increase of the material resistance regarding the risk of brittle failure. In addition to SMILE, a new project dealing with WPS — NESC VII — has been launched in 2008 (linking with the European Network of Excellence NULIFE) with the participation of numerous international organizations (R&D, Utilities and Manufacturers). Based on experimental, analytical and numerical tasks, the project is focused on topics generally not covered by past experience on WPS: biaxiality of loading on large-scale specimens, effect of irradiation, applicability to intergranular fracture, modeling (including analytical and numerical models) … Among these tasks, some new novel WPS experiments are being conducted on large scale cruciform bend bar specimens in order to study the influence of biaxial loading on WPS effect, using a fully representative RPV steel (18MND5 steel similar to A533B steel). After a synthesis of main WPS results available from previous projects on representative RPV steels, a description of the NESC VII project is presented in this paper together with the corresponding organization, including the present status of the project.

scholarly journals Hydro- and morphodynamics in curved river reaches – recent results and directions for future research

2013 ◽  
Vol 37 ◽  
pp. 19-25 ◽  
Author(s):  
K. Blanckaert ◽  
G. Constantinescu ◽  
W. Uijttewaal ◽  
Q. Chen
Keyword(s):  
Sediment Transport ◽  
Secondary Flow ◽  
Large Scale ◽  
Numerical Models ◽  
Three Dimensional ◽  
Future Research ◽  
Turbulence Structures ◽  
Outer Bank ◽  
Flow Processes

Abstract. Curved river reaches were investigated as an example of river configurations where three-dimensional processes prevail. Similar processes occur, for example, in confluences and bifurcations, or near hydraulic structures such as bridge piers and abutments. Some important processes were investigated in detail in the laboratory, simulated numerically by means of eddy-resolving techniques, and finally parameterized in long-term and large-scale morphodynamic models. Investigated flow processes include secondary flow, large-scale coherent turbulence structures, shear layers and flow separation at the convex inner bank. Secondary flow causes a redistribution of the flow and a transverse inclination of the riverbed, which favour erosion of the outer bank and meander migration. Secondary flow generates vertical velocities that impinge on the riverbed, and are known to increase the erosive capacity of the flow. Large-scale turbulent coherent structures also increase the sediment entrainment and transport capacity. Both processes are not accounted for in sediment transport formulae, which leads to an underestimation of the bend scour and the erosion of the outer bank. Eddy-resolving numerical models are computationally too expensive to be implemented in long-term and large-scale morphodynamic models. But they provide insight in the flow processes and broaden the investigated parameter space. Results from laboratory experiments and eddy-resolving numerical models were at the basis of the development of a new parameterization without curvature restrictions of secondary flow effects, which is applicable in long-term and large-scale morphodynamic models. It also led to the development of a new engineering technique to modify the flow and the bed morphology by means of an air-bubble screen. The rising air bubbles generate secondary flow, which redistributes the patterns of flow, boundary shear stress and sediment transport.

scholarly journals EFFECT OF MACRO-ROUGHNESS ELEMENTS ON TSUNAMI INUNDATION: SINK TERM FORMULAE FOR DEPTH-AVERAGED NUMERICAL MODELS

2018 ◽  
pp. 27
Author(s):  
Stefan Leschka ◽  
Clemens Krautwald ◽  
Hocine Oumeraci
Keyword(s):  
Hydraulic Resistance ◽  
Large Scale ◽  
Numerical Models ◽  
Three Dimensional ◽  
Bottom Surface ◽  
Tsunami Propagation ◽  
Tsunami Inundation ◽  
Sink Term ◽  
Roughness Elements ◽  
Computational Element

Tsunami propagation and inundation are commonly simulated using large-scale depth-averaged models. In such models, the quadratic friction law with a selected Manning’s coefficient is generally applied to account for the effect of bottom surface roughness in each computational element. Buildings and tree vegetation in coastal areas are usually smaller than the computational element size. Using empirical Manning’s coefficients to account for such large objects is not physically sound and, particularly in tsunami inundation modelling, this may result in large uncertainties. Therefore, an improved understanding of the processes associated with the hydraulic resistance of the so-called macro-roughness elements (MRE) is required. Relevant parameters such as shape, height and arrangement of the MRE should be investigated through laboratory experiments or numerical tests using a well-validated three-dimensional CFD model. Given the correlation of such parameters to the MRE-induced hydraulic resistance, empirical formulae were developed and directly implemented as sink terms in depth-averaged numerical solvers such as non-linear shallow-water (NLSW) models.

Improvements and Modifications to Electromagnetic Pipeline Surveys

2004 ◽  
Author(s):  
Jim Hunter ◽  
Shawn McGregor ◽  
Shamus McDonnell ◽  
Len Krissa
Keyword(s):  
Three Dimensional ◽  
Small Diameter ◽  
National Research Council ◽  
Cost Effective ◽  
Assessment Process ◽  
Evaluation Tool ◽  
Data Set ◽  
Integrity Assessment ◽  
Survey System ◽  
Uniform Diameter

This paper outlines the development and manufacture of a new pipeline evaluation tool with the capability for multipurpose applications on various types of pipeline systems. Developed with financial assistance from the National Research Council, the new survey system provides pipeline companies access to a cost-effective in-direct integrity assessment process to assist with ensuring safe and reliable operation of their facilities. The technological options available to pipeline integrity assessment are extremely costly and/or considerably outdated. Until recently, external evaluation instrumentation had not been significantly modified since its inception in the mid-1980’s. Although there are inline inspection (ILI) tools or “smart pigs” available to assess the overall integrity of a pipeline, they are extremely expensive. The use of internal inspection tools is also restricted to only those pipelines of uniform diameter and which are modified to accommodate launching and receiving traps. The data from ILI logs does not include depth of cover or coating condition assessment, which are also critical in maintaining the integrity of a pipeline. The majority of small diameter pipelines, such as those in gathering systems, are typically not compatible with the internal inspection technique. The incentive for improving and modifying electromagnetic pipeline coating assessment equipment was based upon: • Customer demand for new pipeline maintenance technologies; • Aging infrastructure; • Increased regulation; • Higher facility throughput and less down time requirements. The new generation of instrumentation is still based upon electromagnetic theory while incorporating the latest in computer and digital technology. In comparison to its predecessors, the package is more accurate, efficient, dependable and robust for a variety of harsh field conditions. The equipment has the ability to reliably collect and evaluate substantial amounts of data in real-time through environmentally sensitive areas such as water crossings and regions of wildlife. Compatibility with industry standards was considered in the development of the associated software used for processing and managing the significant quantity of information collected. The software also offers compatibility with GPS (Global Positioning System) and sonar technologies. Geodetic co-ordinates and, if applicable, water depths are obtained simultaneously with all the associated pipeline survey data, providing permanent reference should future remedial action be required. With the collected data set, it is now possible to effectively monitor erosion effects and shifts in pipeline position through three-dimensional modeling of the pipeline corridor and water crossing.

scholarly journals A Mesh Reduced Method for Speeding Up Structured Grid-Based Water Quantity and Quality Models in Large-Scale River Networks

Water ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 437
Author(s):  
Jin Kang ◽  
Yonggui Wang ◽  
Jing Xu ◽  
Shuihua Yang ◽  
Haobo Hou
Keyword(s):  
High Performance ◽  
Large Scale ◽  
Numerical Models ◽  
Water Environment ◽  
Three Dimensional ◽  
Discrete Element ◽  
River Network ◽  
Labor Costs ◽  
Simulation Performance ◽  
Reservoir Basin

High-precision and efficiently distributed discrete element models for water environment simulation are urgently needed in large-scale river network areas, but most distributed discrete element models are serially computed and need performance improving. Parallel computing and other common methods for models’ high performance have large labor costs and are complicated. We put forward a new mesh reduced method for promoting computational efficiency with grid re-organization according to the structure and algorithm characteristics of 2D and 3D numerical models. This simple and cheap method was adapted to a classical three-dimensional hydrodynamic and sediment model (ECOMSED) for model improvement and effective evaluation. Six schemes with different grids were made to investigate the performance of this method in the river network area of the Three Gorges Reservoir Basin. It showed good characteristics of simulation performance and model speed-up. We concluded that the method is viable and efficient for optimizing distributed discrete element models.

Supersonic Virtual Valve Design for Numerical Simulation of a Large-Bore Natural Gas Engine

2007 ◽  
Vol 129 (4) ◽  
pp. 1065-1071 ◽  
Author(s):  
Gi-Heon Kim ◽  
Allan Kirkpatrick ◽  
Charles Mitchell
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Large Scale ◽  
Numerical Models ◽  
Three Dimensional ◽  
Injection System ◽  
Limiting Factor ◽  
Length Scales ◽  
Poppet Valve ◽  
The Impact

In many applications of supersonic injection devices, three-dimensional computation that can model a complex supersonic jet has become critical. However, in spite of its increasing necessity, it is computationally costly to capture the details of supersonic structures in intricate three-dimensional geometries with moving boundaries. In large-bore stationary natural gas fueled engine research, one of the most promising mixing enhancement technologies currently used for natural gas engines is high-pressure fuel injection. Consequently, this creates considerable interest in three-dimensional computational simulations that can examine the entire injection and mixing process in engines using high-pressure injection and can determine the impact of injector design on engine performance. However, the cost of three-dimensional engine simulations—including a moving piston and the kinetics of combustion and pollutant production—quickly becomes considerable in terms of simulation time requirements. One limiting factor is the modeling of the small length scales of the poppet valve flow. Such length scales can be three orders of magnitude smaller than cylinder length scales. The objective of this paper is to describe the development of a methodology for the design of a simple geometry supersonic virtual valve that can be substituted in three-dimensional numerical models for the complex shrouded poppet valve injection system actually installed in the engine to be simulated. Downstream flow characteristics of the jets from an actual valve and various virtual valves are compared. Relevant mixing parameters, such as local equivalent ratio and turbulence kinetic energy, are evaluated in full-scale moving piston simulations that include the effect of the jet-piston interaction. A comparison of the results has indicated that it is possible to design a simple converging-diverging fuel nozzle that will produce the same jet and, subsequently, the same large-scale and turbulent-scale mixing patterns in the engine cylinder as a real poppet valve.

The liquefaction of sands, a collapse surface approach

1985 ◽  
Vol 22 (4) ◽  
pp. 564-578 ◽  
Author(s):  
J. A. Sladen ◽  
R. D. D'Hollander ◽  
J. Krahn
Keyword(s):  
Steady State ◽  
Large Scale ◽  
Soil Mechanics ◽  
Limit Equilibrium ◽  
Three Dimensional ◽  
Beaufort Sea ◽  
Triaxial Tests ◽  
Necessary Condition ◽  
State Testing ◽  
Hydraulic Fill

Recent large-scale slides occurring during the hydraulic placement of an artificial island berm in the Beaufort Sea resulted from the liquefaction of the berm sand. Subsequent laboratory tests and back analyses have led to advancements in the understanding of the liquefaction potential of sand. Analyses of undrained triaxial tests, undertaken to measure steady state parameters, suggest that there is a "collapse surface" in three-dimensional void ratio – shear stress – normal stress space. A necessary condition for liquefaction is that the soil state lie on this surface. This collapse surface concept is fundamentally an extension of the steady state concepts proposed by others, and in many respects follows the principles of critical state soil mechanics. Replotted published tests support the concept. Parameters used to describe the position of the surface are termed collapse parameters. These can be converted into parameters analogous to Mohr–Coulomb failure parameters and can therefore be used in conventional limit equilibrium stability analyses. Utilizing these parameters overcomes limitations inherent in previously proposed undrained steady state analysis methods. These concepts also provide a basis for a rational explanation of the Beaufort Sea hydraulic fill slides. Key words: liquefaction, sand, hydraulic fill, slope stability, steady state testing.

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