Water distribution networks are essential components of water supply systems. The combination of pipe structural deterioration and mechanics leads to the failure of pipelines. A physical model for estimating the pipe ...Water distribution networks are essential components of water supply systems. The combination of pipe structural deterioration and mechanics leads to the failure of pipelines. A physical model for estimating the pipe failure must include both the pipe deterioration model and mechanics model. Winkler pipe-soil interaction (WPSI), an analytical mechanics model developed by Rajani and Tesfamariam (2004), takes external and internal loads, temperature changes, loss of bedding support, and the elastoplastic effect of soil into consideration. Based on the WPSI model, a method to evaluate the elastic and plastic areas was proposed in the present study. An FEM model based on pipe-soil interaction (PSI) element was used to verify the analytical model. Sensitivity analyses indicate that the soft soil, long pipe and high temperature induced the axial plastic deformation more likely, which, however, may not occur in normal scenarios. The soft soil, pipes in small diameters, long unsupported bedding are prone to form flexural plastic area. The results show that the pipes subjected to the same loads have smaller stresses in the elastoplastic analysis than elastic analysis. The difference, however, is slight.展开更多
To analyze the pipeline response under permanent ground deformation,the evolution of resistance acting on the pipe during the vertical downward offset is an essential ingredient.However,the efficient simulation of pip...To analyze the pipeline response under permanent ground deformation,the evolution of resistance acting on the pipe during the vertical downward offset is an essential ingredient.However,the efficient simulation of pipe penetration into soil is challenging for the conventional finite element(FE)method due to the large deformation of the surrounding soils.In this study,the B-spline material point method(MPM)is employed to investigate the pipe-soil interaction during the downward movement of rigid pipes buried in medium and dense sand.To describe the density-and stress-dependent behaviors of sand,the J2-deformation type model with state-dependent dilatancy is adopted.The effectiveness of the model is demonstrated by element tests and biaxial compression tests.Afterwards,the pipe penetration process is simulated,and the numerical outcomes are compared with the physical model tests.The effects of pipe size and burial depth are investigated with an emphasis on the mobilization of the soil resistance and the failure mechanisms.The simulation results indicate that the bearing capacity formulas given in the guidelines can provide essentially reasonable estimates for the ultimate force acting on buried pipes,and the recommended value of yield displacement may be underestimated to a certain extent.展开更多
Owing to the complexity of the pipe-in-pipe (PIP) riser system in structure, load and restraint, many problems arise in the structural analysis of the system. This paper presents a new method for nonlinear static fini...Owing to the complexity of the pipe-in-pipe (PIP) riser system in structure, load and restraint, many problems arise in the structural analysis of the system. This paper presents a new method for nonlinear static finite element stress analysis of the PIP riser system. The finite element (FE) model of the PIP riser system is built via software AutoPIPE 6.1. According to the specialties of a variety of components in the PIP riser system, different elements are used so as to model the system accurately. Allowing for the complication in modeling the effects of seabed restraint, a technique based on the bilinear spring concept is developed to calculate the soil properties. Then, based on a pipeline project, the entire procedure of stress analysis is discussed in detail, including creation of an FE model, processing of input data and analysis of results. A wide range of loading schemes is investigated to ascertain that the stresses remain within the acceptable range of the pipe material strength. Finally, the effects of the location of flanges, the thermal expansion of submarine pipelines and the seabed restraint on stress distribution in the riser and expansion loop are studied, which are valuable for pipeline designers.展开更多
Due to high temperature and pressure,unburied or shallow buried submarine pipelines experience lateral global buckling. Excessive bending caused by uncontrolled deformation may threaten the safety of the pipeline syst...Due to high temperature and pressure,unburied or shallow buried submarine pipelines experience lateral global buckling. Excessive bending caused by uncontrolled deformation may threaten the safety of the pipeline system. Thus,the integer of a post-buckling pipeline section should be assessed under design temperature and pressure differences. This study focuses on the post-buckling pipeline safety assessment.First,a series of model tests based on sand obtained from Bohai Gulf were proposed,and soil resistance to pipelines with different embedment are measured. A dynamic soil resistance model with varying pipeline embedment and lateral displacement was established. The influence of embedment on peak soil resistance and residual soil resistance was analyzed. Second,the critical buckling forces of pipelines with different imperfections were analyzed. A"critical force range"was proposed to evaluate whether the pipeline exhibits lateral global buckling or not. Third,the limit state of a post-buckling pipeline in an engineering case was assessed. The assessment was proposed based on both load control condition and displacement control condition. Further comparisons show that pipelines reach their limit state according to load control condition far more quickly than according to displacement control condition.展开更多
Reliable assessment of uplift capacity of buried pipelines against upheaval buckling requires a valid failure mechanism and a reliable real-time monitoring technique.This paper presents a sensing solution for evaluati...Reliable assessment of uplift capacity of buried pipelines against upheaval buckling requires a valid failure mechanism and a reliable real-time monitoring technique.This paper presents a sensing solution for evaluating uplift capacity of pipelines buried in sand using fiber optic strain sensing(FOSS)nerves.Upward pipe-soil interaction(PSI)was investigated through a series of scaled tests,in which the FOSS and image analysis techniques were used to capture the failure patterns.The published prediction models were evaluated and modified according to observations in the present study as well as a database of 41 pipe loading tests assembled from the literature.Axial strain measurements of FOSS nerves horizontally installed above the pipeline were correlated with the failure behavior of the overlying soil.The test results indicate that the previous analytical models could be further improved regarding their estimations in the failure geometry and mobilization distance at the peak uplift resistance.For typical slip plane failure forms,inclined shear bands star from the pipe shoulder,instead of the springline,and have not yet reached the ground surface at the peak resistance.The vertical inclination of curved shear bands decreases with increasing uplift displacements at the post-peak periods.At large displacements,the upward movement is confined to the deeper ground,and the slip plane failure progressively changes to the flow-around.The feasibility of FOSS in pipe uplift resistance prediction was validated through the comparison with image analyses.In addition,the shear band locations can be identified using fiber optic strain measurements.Finally,the advantages and limits of the FOSS system are discussed in terms of different levels in upward PSI assessment,including failure identification,location,and quantification.展开更多
To date,with the increasing attention of countries to urban drainage system,more and more regions around the world have begun to build water conveyance tunnels,sewage pressure deep tunnels and so on.However,the suffic...To date,with the increasing attention of countries to urban drainage system,more and more regions around the world have begun to build water conveyance tunnels,sewage pressure deep tunnels and so on.However,the sufficient bearing capacity and corrosion resistance of the structure,which can ensure the actual service life and safety of the tunnel,remain to be further improved.Glass Fiber Reinforced Plastics(GFRP)pipe,with light weight,high strength and corrosion resistance,has the potential to be applied to the deep tunnel structure.This paper proposed a new composite structure of deep tunnel lined with GFRP pipe,which consisted of three layers of concrete segment,cement paste and GFRP pipe.A new pipe-soil spring element model was proposed for the pipesoil interaction with gaps.Based on the C3D8R solid model and the Combin39 spring model,the finite element numerical analysis of the internal pressure status and external pressure stability of the structure was carried out.Combined with the checking calculation of the theoretical formula,the reliability of the two finite element models was confirmed.A set of numerical analysis methods for the design and optimization of the three-layer structure was established.The results showed that from the internal GFRP pipe to the outer concrete pipe,the pressure decreased from 0.5 to 0.32 MPa,due to the internal pressure was mainly undertaken by the inner GFRP pipe.The allowable buckling pressure of GFRP pipe under the cover of 5 GPa high modulus cement paste was 2.66 MPa.The application of GFRP pipe not only improves the overall performance of the deep tunnel structure but also improves the construction quality and safety.The three-layer structure built in this work is safe and economical.展开更多
Existing analytical methods of buried steel pipelines subjected to active strike-slip faults depended on a number of simplifications.To study the failure mechanism more accurately,a refined strain analytical methodolo...Existing analytical methods of buried steel pipelines subjected to active strike-slip faults depended on a number of simplifications.To study the failure mechanism more accurately,a refined strain analytical methodology was proposed,taking the nonlinear characteristics of soil-pipeline interaction and pipe steel into account.Based on the elastic-beam and beam-on-elastic-foundation theories,the position of pipe potential destruction and the strain and deformation distributions along the pipeline were derived.Compared with existing analytical methods and three-dimensional nonlinear finite element analysis,the maximum axial total strains of pipe from the analytical methodology presented are in good agreement with the finite element results at small and intermediate fault movements and become gradually more conservative at large fault displacements.The position of pipe potential failure and the deformation distribution along the pipeline are fairly consistent with the finite element results.展开更多
Subsea pipelines passing through the shallow area are physically protected against the environmental,accidental,and operational loads by trenching and backfilling.Depending on construction methodology,environmental lo...Subsea pipelines passing through the shallow area are physically protected against the environmental,accidental,and operational loads by trenching and backfilling.Depending on construction methodology,environmental loads,and seabed soil properties,the stiffness of backfilling material may become largely different from the native ground(softer than native ground in most of the cases).The different stiffness between the backfill and native ground affects the soil failure mechanisms and lateral soil resistance against large pipeline displacements that may happen due to ground movement,landslides,ice gouging,and drag embedment anchors.This important aspect is not considered by current design codes.In this paper,the effect of trench-backfill stiffness difference on lateral pipeline-backfill-trench interaction was investigated by performing centrifuge tests.The soil deformations and failure mechanisms were obtained by particle image velocimetry(PIV)analysis.Three experiments were conducted by using three different backfills including loose sand,slurry,and chunky clay that represent the purchased,natural in-fill,and preexcavated materials,respectively.The study shows that the current design codes underestimate the lateral soil resistance for small to moderate pipe displacements inside the trench and overestimate it for large lateral displacement,where the pipeline is penetrating into the trench wall.展开更多
This work deals with the analysis of soil-structure interaction modeling of pipeline problems in static behavior using the coupling between FEM （finite element method） and BEM （boundary element method）. The repres...This work deals with the analysis of soil-structure interaction modeling of pipeline problems in static behavior using the coupling between FEM （finite element method） and BEM （boundary element method）. The representation of the pipe is made by MEF using one fmite element in the cylindrical panel formulated from the theory of equivalent discrete layers （Layerwise theory）, proposed by J. N. Reddy. The soil is represented by elastic continum infimite or semi-infinite and modeled using boundary elements with special curved surface, associated with cylindrical panel used to represent the soil-structure interaction within the soil, especially at the contact surface with the pipe.展开更多
Buried water pipelines are vulnerable to fail or break due to excessive loading or ground displacements.Accurate evaluation of pipe performance and serviceability relies on the proper understanding of pipe-soil intera...Buried water pipelines are vulnerable to fail or break due to excessive loading or ground displacements.Accurate evaluation of pipe performance and serviceability relies on the proper understanding of pipe-soil interactions(PSI).Analytical methods are important approaches to studying PSI.However,a systematic and thorough literature review to analyze the existing research trends,technological achievements and future research opportunities is not available.This work investigates analytical methods that analyze the stress and deformation of pipes in terms of cross-sectional,transverse and longitudinal PSI problems.First,scientometric analysis is performed to acquire relevant research works from online databases and analyze the existing data of influential authors,productive research sources and frequent key word occurrence in the fields of interest.Second,a qualitative discussion is performed in the three categories of PSI:(1)cross-sectional,including ovalization and circumferential behaviours;(2)transverse,including seismic fault crossing,weak soil zones,ground settlement and pipe uplift;and(3)longitudinal.Third,six research opportunities are discussed,including the role of friction in cross-sectional deformation,combined effects of bending and compression,choice of soil reaction models and calibration of key parameters,effect of pipe flaws,soil spatial variability and behaviours of curved pipes.This study helps beginners familiarize themselves with PSI analytical methods and provides experienced researchers with ideas for future research directions.展开更多
China’s economic development is closely related to oil and gas resources,and the country is investing heavily in pipeline construction.Slope geological hazards seriously affect the long-term safe operation of buried ...China’s economic development is closely related to oil and gas resources,and the country is investing heavily in pipeline construction.Slope geological hazards seriously affect the long-term safe operation of buried pipelines,usually causing pipeline leakage,property and environmental losses,and adverse social impacts.To ensure the safety of pipelines and reduce the probability of pipeline disasters,it is necessary to predict and quantitatively evaluate slope hazards.While there has been much research focus in recent years on the evaluation of pipeline slope disasters and the stress calculation of pipelines under hazards,existing methods only provide information on the occurrence probability of slope events,not whether a slope disaster will lead to pipeline damage.Taking the 2015 Xinzhan landslide in Guizhou Province,China,as an example,this study used discrete elements to simulate landslide events and determine the risk level and scope for pipeline damage,and then established a pipe-soil coupling model to quantitatively evaluate the impact of landslide hazards for pipelines in medium-and high-risk areas.The results provide a reference for future pipeline disaster prevention and control.展开更多
The J-lay method is regarded as one of the most feasible methods to lay a pipeline in deep water and ultra-deep water. A numerical model that accounts for the nonlinear soil stiffness is developed in this study to eva...The J-lay method is regarded as one of the most feasible methods to lay a pipeline in deep water and ultra-deep water. A numerical model that accounts for the nonlinear soil stiffness is developed in this study to evaluate a J-lay pipeline. The pipeline considered in this model is divided into two parts： the part one is suspended in water, and the part two is laid on the seabed. In addition to the boundary conditions at the two end points of the pipeline, a special set of the boundary conditions is required at the touchdown point that connects the two parts of the pipeline. The two parts of the pipeline are solved by a numerical iterative method and the finite difference method, respectively. The proposed numerical model is validated for a special case using a catenary model and a numerical model with linear soil stiffness. A good agreement in the pipeline configuration, the tension force and the bending moment is obtained among these three models. Furthermore, the present model is used to study the importance of the nonlinear soil stiffness. Finally, the parametric study is performed to study the effect of the mudline shear strength, the gradient of the soil shear strength, and the outer diameter of the pipeline on the pipelaying solution.展开更多
基金Project supported by the National Natural Science Foundation of China (No. 50278088)the Program for New Century Excellent Talents in University (No. NCET-04-0525), China
文摘Water distribution networks are essential components of water supply systems. The combination of pipe structural deterioration and mechanics leads to the failure of pipelines. A physical model for estimating the pipe failure must include both the pipe deterioration model and mechanics model. Winkler pipe-soil interaction (WPSI), an analytical mechanics model developed by Rajani and Tesfamariam (2004), takes external and internal loads, temperature changes, loss of bedding support, and the elastoplastic effect of soil into consideration. Based on the WPSI model, a method to evaluate the elastic and plastic areas was proposed in the present study. An FEM model based on pipe-soil interaction (PSI) element was used to verify the analytical model. Sensitivity analyses indicate that the soft soil, long pipe and high temperature induced the axial plastic deformation more likely, which, however, may not occur in normal scenarios. The soft soil, pipes in small diameters, long unsupported bedding are prone to form flexural plastic area. The results show that the pipes subjected to the same loads have smaller stresses in the elastoplastic analysis than elastic analysis. The difference, however, is slight.
基金supported by the National Natural Science Foundation of China(Grant Nos.42225702,42077235 and 41722209).
文摘To analyze the pipeline response under permanent ground deformation,the evolution of resistance acting on the pipe during the vertical downward offset is an essential ingredient.However,the efficient simulation of pipe penetration into soil is challenging for the conventional finite element(FE)method due to the large deformation of the surrounding soils.In this study,the B-spline material point method(MPM)is employed to investigate the pipe-soil interaction during the downward movement of rigid pipes buried in medium and dense sand.To describe the density-and stress-dependent behaviors of sand,the J2-deformation type model with state-dependent dilatancy is adopted.The effectiveness of the model is demonstrated by element tests and biaxial compression tests.Afterwards,the pipe penetration process is simulated,and the numerical outcomes are compared with the physical model tests.The effects of pipe size and burial depth are investigated with an emphasis on the mobilization of the soil resistance and the failure mechanisms.The simulation results indicate that the bearing capacity formulas given in the guidelines can provide essentially reasonable estimates for the ultimate force acting on buried pipes,and the recommended value of yield displacement may be underestimated to a certain extent.
文摘Owing to the complexity of the pipe-in-pipe (PIP) riser system in structure, load and restraint, many problems arise in the structural analysis of the system. This paper presents a new method for nonlinear static finite element stress analysis of the PIP riser system. The finite element (FE) model of the PIP riser system is built via software AutoPIPE 6.1. According to the specialties of a variety of components in the PIP riser system, different elements are used so as to model the system accurately. Allowing for the complication in modeling the effects of seabed restraint, a technique based on the bilinear spring concept is developed to calculate the soil properties. Then, based on a pipeline project, the entire procedure of stress analysis is discussed in detail, including creation of an FE model, processing of input data and analysis of results. A wide range of loading schemes is investigated to ascertain that the stresses remain within the acceptable range of the pipe material strength. Finally, the effects of the location of flanges, the thermal expansion of submarine pipelines and the seabed restraint on stress distribution in the riser and expansion loop are studied, which are valuable for pipeline designers.
基金Sponsored by the National Basic Key Research Program of China(Grant No.2014CB046802)the National Natural Science Foundation of China(Grant No.51679162)
文摘Due to high temperature and pressure,unburied or shallow buried submarine pipelines experience lateral global buckling. Excessive bending caused by uncontrolled deformation may threaten the safety of the pipeline system. Thus,the integer of a post-buckling pipeline section should be assessed under design temperature and pressure differences. This study focuses on the post-buckling pipeline safety assessment.First,a series of model tests based on sand obtained from Bohai Gulf were proposed,and soil resistance to pipelines with different embedment are measured. A dynamic soil resistance model with varying pipeline embedment and lateral displacement was established. The influence of embedment on peak soil resistance and residual soil resistance was analyzed. Second,the critical buckling forces of pipelines with different imperfections were analyzed. A"critical force range"was proposed to evaluate whether the pipeline exhibits lateral global buckling or not. Third,the limit state of a post-buckling pipeline in an engineering case was assessed. The assessment was proposed based on both load control condition and displacement control condition. Further comparisons show that pipelines reach their limit state according to load control condition far more quickly than according to displacement control condition.
基金support provided by the National Natural Science Foundation of China(Grant No.42077235)the Science and Technology Plan Project of Xuzhou,China(Grant No.KC21310)the Open Fund of the State Key Laboratory for Geomechanics and Deep Underground Engineering(Grant No.SKLGDUEK 1902).
文摘Reliable assessment of uplift capacity of buried pipelines against upheaval buckling requires a valid failure mechanism and a reliable real-time monitoring technique.This paper presents a sensing solution for evaluating uplift capacity of pipelines buried in sand using fiber optic strain sensing(FOSS)nerves.Upward pipe-soil interaction(PSI)was investigated through a series of scaled tests,in which the FOSS and image analysis techniques were used to capture the failure patterns.The published prediction models were evaluated and modified according to observations in the present study as well as a database of 41 pipe loading tests assembled from the literature.Axial strain measurements of FOSS nerves horizontally installed above the pipeline were correlated with the failure behavior of the overlying soil.The test results indicate that the previous analytical models could be further improved regarding their estimations in the failure geometry and mobilization distance at the peak uplift resistance.For typical slip plane failure forms,inclined shear bands star from the pipe shoulder,instead of the springline,and have not yet reached the ground surface at the peak resistance.The vertical inclination of curved shear bands decreases with increasing uplift displacements at the post-peak periods.At large displacements,the upward movement is confined to the deeper ground,and the slip plane failure progressively changes to the flow-around.The feasibility of FOSS in pipe uplift resistance prediction was validated through the comparison with image analyses.In addition,the shear band locations can be identified using fiber optic strain measurements.Finally,the advantages and limits of the FOSS system are discussed in terms of different levels in upward PSI assessment,including failure identification,location,and quantification.
基金This project was supported by the Fundamental Research Funds for the Central Universities(WUT:2018IB001)the Fundamental Research Funds for the Central Universities(WUT:2019III130CG).
文摘To date,with the increasing attention of countries to urban drainage system,more and more regions around the world have begun to build water conveyance tunnels,sewage pressure deep tunnels and so on.However,the sufficient bearing capacity and corrosion resistance of the structure,which can ensure the actual service life and safety of the tunnel,remain to be further improved.Glass Fiber Reinforced Plastics(GFRP)pipe,with light weight,high strength and corrosion resistance,has the potential to be applied to the deep tunnel structure.This paper proposed a new composite structure of deep tunnel lined with GFRP pipe,which consisted of three layers of concrete segment,cement paste and GFRP pipe.A new pipe-soil spring element model was proposed for the pipesoil interaction with gaps.Based on the C3D8R solid model and the Combin39 spring model,the finite element numerical analysis of the internal pressure status and external pressure stability of the structure was carried out.Combined with the checking calculation of the theoretical formula,the reliability of the two finite element models was confirmed.A set of numerical analysis methods for the design and optimization of the three-layer structure was established.The results showed that from the internal GFRP pipe to the outer concrete pipe,the pressure decreased from 0.5 to 0.32 MPa,due to the internal pressure was mainly undertaken by the inner GFRP pipe.The allowable buckling pressure of GFRP pipe under the cover of 5 GPa high modulus cement paste was 2.66 MPa.The application of GFRP pipe not only improves the overall performance of the deep tunnel structure but also improves the construction quality and safety.The three-layer structure built in this work is safe and economical.
基金Project(50439010) supported by the National Natural Science Foundation of ChinaProject(DUT10ZD201) supported by the Fundamental Research Funds for the Central Universities in China
文摘Existing analytical methods of buried steel pipelines subjected to active strike-slip faults depended on a number of simplifications.To study the failure mechanism more accurately,a refined strain analytical methodology was proposed,taking the nonlinear characteristics of soil-pipeline interaction and pipe steel into account.Based on the elastic-beam and beam-on-elastic-foundation theories,the position of pipe potential destruction and the strain and deformation distributions along the pipeline were derived.Compared with existing analytical methods and three-dimensional nonlinear finite element analysis,the maximum axial total strains of pipe from the analytical methodology presented are in good agreement with the finite element results at small and intermediate fault movements and become gradually more conservative at large fault displacements.The position of pipe potential failure and the deformation distribution along the pipeline are fairly consistent with the finite element results.
文摘Subsea pipelines passing through the shallow area are physically protected against the environmental,accidental,and operational loads by trenching and backfilling.Depending on construction methodology,environmental loads,and seabed soil properties,the stiffness of backfilling material may become largely different from the native ground(softer than native ground in most of the cases).The different stiffness between the backfill and native ground affects the soil failure mechanisms and lateral soil resistance against large pipeline displacements that may happen due to ground movement,landslides,ice gouging,and drag embedment anchors.This important aspect is not considered by current design codes.In this paper,the effect of trench-backfill stiffness difference on lateral pipeline-backfill-trench interaction was investigated by performing centrifuge tests.The soil deformations and failure mechanisms were obtained by particle image velocimetry(PIV)analysis.Three experiments were conducted by using three different backfills including loose sand,slurry,and chunky clay that represent the purchased,natural in-fill,and preexcavated materials,respectively.The study shows that the current design codes underestimate the lateral soil resistance for small to moderate pipe displacements inside the trench and overestimate it for large lateral displacement,where the pipeline is penetrating into the trench wall.
文摘This work deals with the analysis of soil-structure interaction modeling of pipeline problems in static behavior using the coupling between FEM （finite element method） and BEM （boundary element method）. The representation of the pipe is made by MEF using one fmite element in the cylindrical panel formulated from the theory of equivalent discrete layers （Layerwise theory）, proposed by J. N. Reddy. The soil is represented by elastic continum infimite or semi-infinite and modeled using boundary elements with special curved surface, associated with cylindrical panel used to represent the soil-structure interaction within the soil, especially at the contact surface with the pipe.
基金The authors gratefully acknowledge the Innovation and Technology Support Programme(ITSP)[Grant No.ITS/033/20FP]the Water Supplies Department of Hong Kong,China.Suggestions given by Dr.Andy Y.F.Leung are also appreciated.
文摘Buried water pipelines are vulnerable to fail or break due to excessive loading or ground displacements.Accurate evaluation of pipe performance and serviceability relies on the proper understanding of pipe-soil interactions(PSI).Analytical methods are important approaches to studying PSI.However,a systematic and thorough literature review to analyze the existing research trends,technological achievements and future research opportunities is not available.This work investigates analytical methods that analyze the stress and deformation of pipes in terms of cross-sectional,transverse and longitudinal PSI problems.First,scientometric analysis is performed to acquire relevant research works from online databases and analyze the existing data of influential authors,productive research sources and frequent key word occurrence in the fields of interest.Second,a qualitative discussion is performed in the three categories of PSI:(1)cross-sectional,including ovalization and circumferential behaviours;(2)transverse,including seismic fault crossing,weak soil zones,ground settlement and pipe uplift;and(3)longitudinal.Third,six research opportunities are discussed,including the role of friction in cross-sectional deformation,combined effects of bending and compression,choice of soil reaction models and calibration of key parameters,effect of pipe flaws,soil spatial variability and behaviours of curved pipes.This study helps beginners familiarize themselves with PSI analytical methods and provides experienced researchers with ideas for future research directions.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.42120104002,42271075,and U21A2008)。
文摘China’s economic development is closely related to oil and gas resources,and the country is investing heavily in pipeline construction.Slope geological hazards seriously affect the long-term safe operation of buried pipelines,usually causing pipeline leakage,property and environmental losses,and adverse social impacts.To ensure the safety of pipelines and reduce the probability of pipeline disasters,it is necessary to predict and quantitatively evaluate slope hazards.While there has been much research focus in recent years on the evaluation of pipeline slope disasters and the stress calculation of pipelines under hazards,existing methods only provide information on the occurrence probability of slope events,not whether a slope disaster will lead to pipeline damage.Taking the 2015 Xinzhan landslide in Guizhou Province,China,as an example,this study used discrete elements to simulate landslide events and determine the risk level and scope for pipeline damage,and then established a pipe-soil coupling model to quantitatively evaluate the impact of landslide hazards for pipelines in medium-and high-risk areas.The results provide a reference for future pipeline disaster prevention and control.
基金supported by the China Scholarship Council,the Technology Major Project of China(Grant No.2011ZX05027-002)the National Natural Science Foundation of China(Grant No.51409128)the University Natural Science Research Project of Jiangsu Province(Grant No.14KJB570001)
文摘The J-lay method is regarded as one of the most feasible methods to lay a pipeline in deep water and ultra-deep water. A numerical model that accounts for the nonlinear soil stiffness is developed in this study to evaluate a J-lay pipeline. The pipeline considered in this model is divided into two parts： the part one is suspended in water, and the part two is laid on the seabed. In addition to the boundary conditions at the two end points of the pipeline, a special set of the boundary conditions is required at the touchdown point that connects the two parts of the pipeline. The two parts of the pipeline are solved by a numerical iterative method and the finite difference method, respectively. The proposed numerical model is validated for a special case using a catenary model and a numerical model with linear soil stiffness. A good agreement in the pipeline configuration, the tension force and the bending moment is obtained among these three models. Furthermore, the present model is used to study the importance of the nonlinear soil stiffness. Finally, the parametric study is performed to study the effect of the mudline shear strength, the gradient of the soil shear strength, and the outer diameter of the pipeline on the pipelaying solution.
