Response Of Pipelines Research Articles

Dynamic Response Analysis of Buried HDPE Pipes under Vibration Compaction Considering the Influence of Buried Depth and Filling Modulus

During pavement construction, the gravity load and vibration excitation from vibratory rollers can seriously affect the safety of underground pipelines. However, research on the dynamic response of buried pipelines under the action of large vibration rollers is rarely reported. Therefore, the dynamic response of a high-density polyethylene (HDPE) double-wall corrugated pipe under a vibratory roller was studied via field testing and a three-dimensional nonlinear finite-element model was established. This model was used to analyze the influence of filling property and vibration frequency on the dynamic response of an HDPE pipe under a vibration load from a vibratory roller. The results reveal that with the increase of compaction times, the backfill soil keeps changing between over-compaction (loose) and compaction states, and the pipe top pressure also keeps changing. Moreover, at a shallow burial, the pipe top pressure is more obvious when the compaction degree changes. The elastic modulus of filling soil within a certain range can effectively reduce the stress deformation of the pipeline under vibration compaction. However, when the elastic modulus of filling soil exceeds 10 times the initial elastic modulus, the deformation of the pipeline becomes greater than the initial value.

Resilience of HP/HT pipelines to combined seismic and thermal loadings

Resilience of unburied high pressure/high temperature (HP/HT) pipelines with different outside diameter-to-wall thickness (OD/t) ratios and subjected to the combined action of both earthquake and thermal loads is studied numerically. Unlike most of the existing research on buried or trenched pipelines, the current work analyses the resilience to combined seismic-thermal actions of an unburied pipeline laid on the seabed and resting on a sleeper. By using finite element analyses (FEA), the thermal and seismic responses of pipelines with different OD/t ratios are captured. The pipeline-soil and pipeline-sleeper interactions are modelled using Mohr-Coulomb constitutive contact behaviour. Empirical equations of critical temperatures causing lateral buckling in pipelines with OD/t between 10 and 50 are developed. Rayleigh damping coefficients are calculated following modal analyses, whereby the pipeline-soil system frequencies are found. Resilience to failure under combined seismic and thermal actions is load-path dependent; the earthquake imposed on a laterally buckled pipeline represents the most detrimental scenario. It is understood that the introduction of seismic load can amplify the buckle amplitudes beyond the pre-defined controlled buckle amplitude and thus cause overstressing and/or local buckling in the buckle crown segment. Local buckling due to the interaction between thermal and seismic loading is found to be more pronounced in pipelines with OD/t > 40.

Dynamic Response Analysis of Buried Aviation Oil Pipeline Under Heavy Vehicle Load

The risk of damage caused by the third party construction such as vehicle rolling is increasing day by day, which seriously threatens the production and operation of the aviation oil pipeline and the life and property safety of the people along the line. Based on the theoretical calculation model of vehicle rolling, the finite element models of pipeline, soil and pipe-soil are established respectively. At the same time, the moving load is loaded using the VLOAD subroutine, and the numerical simulation is carried out using ABAQUS. Finally, the influence of vehicle rolling load on the dynamic response of buried gas pipeline under different vehicle weight and speed conditions is analyzed. The research results have important guiding value for preventing the damage accident of aviation oil pipeline caused by vehicle crushing and guaranteeing the safe and smooth operation of aviation oil pipeline.

Mechanical behavior of high-pressure pipeline installed through horizontal directional drilling under seismic loads

The present study investigates the mechanical behavior of high-pressure pipelines installed through horizontal directional drilling (HDD), a crucial trenchless installation method, under seismic loads. Utilizing the finite element method and artificial viscoelastic boundary conditions, this paper analyzes the stress response of pipelines subjected to seismic loads in two directions. The seismic loads are applied using the response spectrum method, and the pipeline stress is analyzed in time history. A comparison of the stress in pipelines installed through the HDD method and the traditional open-cut method is conducted, and the impact of earthquake magnitude on pipeline stress is evaluated. The results indicate that the pipeline stress is greater when the seismic acceleration acts transversely, with bending deformation being the dominant mode of response. A 9.29% increase in maximum stress is observed for each increment in earthquake magnitude. Furthermore, the stress in pipelines installed through the HDD method is 48% lower than that of pipelines installed using the open-cut method when subjected to transverse seismic loads.

Analytical Study of Lateral Buckling of Pipelines with Initial Imperfection Based on Fixed-Fixed Beam Model

The beam analysis model and the initial imperfection are predominant factors in analyzing the lateral buckling behavior of submarine pipelines under high temperature. However, the existing beam models do not consider the inhibition provided by the virtual anchor point of the pipeline. In this study, a fixed-fixed beam model is introduced to simulate the lateral buckling response of a submarine pipeline. This model considers the suppression tension provided by the virtual anchor point during the pipeline feeding-in process, which better reduces the buckling response phenomenon of the pipeline. Based on the assumption of rigid-plastic pipe-soil interaction, the analytical solution of the buckling development of pipeline under full-contact repetitive cosine imperfection is derived. The effectiveness of the fixed-fixed model is verified by comparing with the analytical solutions in other literature. The influence of the imperfection model, the temperature difference, and the soil resistance on the pipeline buckling is investigated. Finally, the size effect of the pipeline on the effective axial force development is discussed. The results show that the pipeline undergoes stress vibration under tensile force, and the frequency and density of the pipeline stress vibration increase with the increase of the initial defect amplitude. Increasing the diameter–thick ratio will significantly increase the bending amplitude and bending stress of the pipeline. Attention should be paid to the fatigue damage caused by continuous stress mutations during pipeline buckling, which could further lead to the structural destruction of the pipeline.

Assessment of the Response of Trenched–Backfilled Pipelines to Strike-Slip Faults: An Analytical Approach

Trenched pipelines may experience significant lateral displacement due to natural geohazards such as strike slip-fault movements, landslides, etc. Using pre-excavated soil to backfill trenches is a cost-effective option to protect pipelines against large deformations. These backfilling materials are heavily remolded and therefore softer than the native ground. Therefore, the shear strength difference between the backfill and native ground may affect the pipeline–backfill–trench interaction and the failure mechanism of the surrounding soil. By assuming a simplified uniform soil domain, the influence of softer pre-excavated backfilling material on the pipeline–backfill–trench interaction is neglected in the analytical methods that are usually used in the structural health monitoring of buried pipelines. In this study, the effects of trenching and backfilling were incorporated into an analytical solution for a fast assessment of the pipeline response at the early stages of engineering design projects and structural health monitoring. In comparison with other methods, this methodology provides a convenient and efficient method for computing pipeline strain and deflection curves in geohazardous regions.

Vibration safety evaluation and vibration isolation control measures for buried oil pipelines under dynamic compaction: A case study

As a common treatment method to improve the bearing capacity of soft soil sites, the strong impact vibration generated by dynamic compaction (DC) has adverse effects on the surrounding environment and adjacent structures. In this paper, a series of in-situ tests were conducted to evaluate the vibration safety of adjacent buried oil pipelines under DC shock. The vibration responses and attenuation rules of the site were analyzed. Meanwhile, a numerical method was employed to discuss and determine the minimum tamping distance and rational parameters for isolation trench. Furthermore, the vertical peak vibration velocity index was used to evaluate the vibration safety of the pipeline under DC load. The results show that the vibration response of the site is manifested as vertical vibration and horizontal vibration, while the vibration response of the buried pipeline is dominated by vertical vibration. The empty trench can block the propagation of vibration waves effectively, in which the depth and its distance to the ramming point are the main factors affecting the vibration isolation effect. The vibration isolation effect of the trench increases with the increase of trench depth and the decrease of the distance from the tamping point. The study proposed parameters for an empty trench with a depth of 5 m and a safety distance of 5 m from the compaction point for the final ground treatment scheme. Good results have been achieved in engineering practice. The analysis results provide new ideas and references for promoting the application of underground pipeline vibration protection technology in DC ground treatment.

An experimental study on vortex-induced vibration suppression for submarine multispan pipelines

To ensure structural safety, it is necessary to reduce the vortex-induced vibration (VIV) of free-span pipelines in offshore engineering applications. In this study, an experimental investigation on VIV suppression for submarine multispan pipelines was conducted. The VIV response was suppressed by attaching helical strakes to the pipeline. By comparing the vibration response of a smooth multispan pipeline with that of a pipeline with an installed suppression device, the suppression effect of the helical strakes was explored. The coverage of the helical strakes was changed, and differences in the VIV suppression effects were observed in the experiment. The helical strakes effectively suppressed VIV of the multispan pipeline, and the maximum suppression efficiency exceeded 90%. The inhibition effect increased with increasing strake coverage. Furthermore, the burial depth of the pipeline was found to influence the VIV suppression effect.

Dynamic instability mechanisms of offshore pipelines and risers

Dynamic response of offshore pipelines and risers under cross-flow (e.g. ocean currents, vessel motion etc.) has successfully been analysed. Although the pipelines are used for fluid transportation, sufficient attention has not been paid to the dynamic instability under axial flow. In this study, axial flow-induced instability mechanisms of offshore pipelines and risers are investigated. To this end, the interaction of the axial flow forces of a fluid element with the forces of the corresponding pipe element during pipeline flexural motion is analysed. Interpretation of the terms of the motion equation is provided and analogies with the model of dynamic buckling of a Euler beam are detected. Original transfer matrices are developed for the dynamic control of pipelines under axial flow. The critical values of the flow velocity causing dynamic instability and the corresponding axial flow-induced buckling modes are determined. Implementation of the method to a representative case study is provided and discussed.

Seismic Response of Cable-Stayed Spanning Pipeline Considering Medium-Pipeline Fluid–Solid Coupling Dynamic Effect

With the aim of determining the influence of the fluid–structure coupling dynamic effect of the oil and gas transmission medium and pipeline on the seismic response, an oil pipeline supported by a cable-stayed spanning structure was taken as the study object. Kinetic equations taking into account the action of oil and gas medium were studied, and a finite element model structure considering the additional-mass method and the fluid–structure coupling effect were established separately. In addition, the mechanism of the oil–gas–pipeline coupling action on the seismic response of pipeline structure was analyzed, and the results were obtained. The results show that the pipeline has a minimal seismic response at the abutment location, the seismic response gradually increases along the abutment to the main tower, and the seismic response reach is maximized at about one-fifth of the bridge platform. The seismic response of the oil and gas pipeline model structure using the additional-mass method is generally more significant than that based on the fluid–solid coupled dynamic model; moreover, the maximum displacement response differs by about 24%, and the maximum acceleration response differs by approximately 30%, indicating that the oil and gas medium has a certain viscoelastic damping effect on the seismic response of the oil pipeline, which provides a reference for the seismic response calculation theory and analysis method of cable-stayed spanning oil pipelines.

Longitudinal vibrations of underground pipelines of finite length in medium surrounded by soil with different properties along pipeline length

An analysis of the dynamic response of an underground main pipeline under a longitudinal wave propagating in soil along the pipe is given in the article. The problem of the longitudinal wave impact on a pipeline of finite length, interacting with soil according to the elastic-viscous law, is considered. The ends of the pipeline are fixed to massive nodes that interact with the medium according to linear laws. Along the length of the pipeline, the coefficients of the elastic and viscous pipeline-soil interaction change depending on the coordinate. In this article, the influence of the coefficients of elastic and viscous interaction of the "pipe-soil" system is studied when these coefficients are coordinate functions. The variability of the values of the coefficients along the length of the pipeline leads to a change in displacements from 0 to 15% and strain from 0 to 18%, compared with the case when these coefficients are constant. Depending on the length of the pipeline, the response of the pipeline to seismic action is different. This is especially evident at the boundary points. Considering the weight of nodes leads largely to a decrease in the strain of the pipeline relative to the soil strain at the boundary points.

Transient flow analysis for pumping system comprising pressure vessel using unsteady friction model

Recent myriad studies on the application of pressure vessels (PVs) to dampen the potentially hazardous transient pressure caused by pump failure are available in the literature. However, little research has been done on integrating these PVs into an instantaneous acceleration-based (IAB) model for transient flow analysis, while most of the reported investigations have been accomplished using the steady-state friction models. Also, scarce literature exists on optimizing the connection configuration of the PV. Nevertheless, unsteady friction (UF) is vital in accurately modeling a transient event, and therefore this study utilizes the IAB UF model to accurately predict the transient response of the pumping pipeline protected by a PV. Based on the proposed numerical model and computational algorithms, a novel approach is also explored to increase the working efficiency of the PV during transient events via a modified connection configuration with the main pipeline. A parametric study has been conducted to determine the impact of the PV's numerous parameters on transient pressure signals. The results reveal that the IAB UF model with two decay parameters can accurately replicate the amplitude and form of transient waves in a pumping system comprising a PV, with almost no deviations between numerical and experimental results. Furthermore, the numerical study shows that the initial air volume, polytropic exponent, installation location, PV size, and connection arrangement of PV with the pump-rising pipeline significantly affect the performance of water hammer protection. However, the flow resistance of connecting pipes containing perforated plates in a separate bypass line reduces the desired vessel volume from the standpoint of economy. The energy-based approach corroborates the use of this design for vessel-to-pipeline connections. The redesigned connection configuration reduces the required volume of PV by up to 70%, which leads to cost-effectiveness.

Effects of Vibration on Adjacent Pipelines under Blasting Excavation

Exploring a pipeline’s response to blast vibration during tunnel excavation is critical for ensuring the safety of the pipeline. In this paper, the vibration monitoring and numerical simulation methods are used to evaluate the dynamic response of ground soil and pipelines to blasts. The attenuation law of peak particle velocity (PPV) and the distribution characteristics of peak effective stress (PES) in pipe sections under different working conditions are studied. The following findings are recorded: (1) A three-dimensional model considering in situ stress is established, and it is found the triangular equivalent load simulation blast effect method used in this paper can effectively reflect the impact of blasting on pipelines. The simulation error is controlled at 7.69%. (2) The ground PPV of each monitoring point decays continuously with the increase in horizontal and axial distance, and the cavity enlargement effect is exhibited above the excavation area. The oncoming blast side PPV of the pipe section is more significant than that behind the blast side. (3) When the blast vibration is transmitted to the pipe, there are differences in the PPV and PES distribution characteristics across the pipe cross-section. The PPV is greater in the lower part of the pipe section, while the PES value is greater in the upper part of the pipe section. The maximum PES of 1.53 MPa is significantly lower than the safety threshold (≤4.6 MPa) at the hazardous-section-monitoring point. (4) A pipeline PPV prediction model is proposed to guide subsequent blasting program development. An empirical formula for the safety criterion applicable to this study is proposed for the scientific implementation of safety assessments for subsequent construction. This safety evaluation framework can be used as a reference for similar projects.

Safety Analysis and Emergency Response of Suspended Oil and Gas Pipelines Triggered by Natural Disasters

Pipelines play a dominant role in the transportation of oil and gas and the safety of pipelines is essential for the supply of energy. However, natural disasters such as floods and land subsidence may lead to suspended pipelines, resulting in pipeline failure accidents, causing casualties and environmental pollution. To deal with the emergency caused by suspended pipelines, it is needed to identify the failure mechanisms of suspended pipelines caused by natural disasters. Therefore, this study conducts a safety analysis of suspended pipelines using a nonlinear finite element method (FEM), considering the nonlinear pipe–soil contact and plastic deformation. A case study is conducted to investigate the influencing parameters (e.g., the suspended length, the operating pressure, and the fluid mass). This work demonstrates that irreversible plastic strains occur when the suspended length exceeds 50 m, and it will reach 2% when the suspended length is 340 m. Finally, an emergency response plan based on plastic strain and suspended length is proposed to determine the emergency level of the suspended pipelines caused by natural disasters. This study can provide technical support for the emergency response of pipelines in areas with frequent natural disasters, promoting the sustainable development of oil and natural gas pipelines.

Optimal Route Selection of Offshore Pipelines Subjected to Submarine Landslides

Background: Offshore lifelines (i.e., pipelines and cables) are usually vulnerable to seabed deformations induced by earthquake-triggered geohazards, such as submarine landslides, soil liquefaction, and tectonic faulting. Since the complete avoidance of all areas characterized by offshore geohazards is not always techno-economically feasible, optimal lifeline route selection is deemed necessary for the safety and serviceability of every such infrastructure, in order to minimize the risk of severe environmental and economic consequences. Objective: The current study presents a decision-support tool for the design of offshore high-pressure gas pipelines, capable of performing: (a) the assessment of submarine landslides along a possible pipeline route (i.e., impact force and landslide width), (b) the assessment of their potential impact on the pipeline (i.e., pipeline strains), and (c) the optimal pipeline route selection. Methods: The advanced capabilities of GIS in lifeline optimal route selection are successfully combined with efficient (semi-)analytical models that realistically assess the response of offshore pipelines when subjected to axial or oblique loading conditions due to a submarine landslide. Results: The efficiency of the smart tool is presented through a case study of an offshore pipeline that is crossing potentially unstable slopes -under static and seismic conditions- in the Adriatic Sea. Five alternative routings are proposed based on the adopted design criteria when crossing the seismically unstable slopes and zones characterized by steep inclination. Conclusion: Provided that sufficient and reliable data are available, the developed decision-support tool can be efficiently used for deriving the potentially optimal route of an offshore pipeline.

Dynamic response and safety assessment of inner‐wall corroded concrete pipeline in service subjected to blasting vibration

AbstractBuried pipelines in urban area are prone to corrosion defects for many years. Ensure the safety of buried corrosion pipelines is a key concern during tunnel blasting excavation. Based on the blasting engineering along Shenzhen Metro Line 12, the field test of full‐scale concrete pipeline adjacent blasting was implemented. The dynamic response of concrete pipeline induced by blasting vibration was analyzed by using the dynamic finite element numerical simulation method, and the reliability of numerical simulation was verified by the field monitoring data. On this basis, considering the corrosion defect morphology of pipeline, the distribution characteristics of peak particle velocity and peak effective stress of concrete pipeline with different corrosion depths, corrosion widths, and corrosion lengths induced by blasting vibration were discussed. The parameter analysis method was used to research the influence of corrosion morphology parameters on the dynamic response of the pipeline, and the corrosion depth of the inner‐wall of the pipeline was defined as the main control parameter of the dynamic response. According to the failure criteria of concrete materials, the safety criterion of corroded concrete pipelines with different service years subjected to blasting vibration was established.

Shake table test and numerical analysis of the seismic response of buried long-distance pipeline under longitudinal non-uniform excitation

To investigate the seismic response characteristics of buried pipelines under longitudinal non-uniform seismic excitation, a three-dimensional finite element overall analysis model is established on finite element analysis software based on the shaking table test of buried oil and gas pipelines under longitudinal non-uniform excitation. The calculated results are compared with the experimental analysis results to evaluate the correctness and reliability of the established model. The acceleration response, strain response, and displacement response of buried oil and gas pipelines and surrounding soil under longitudinal traveling wave excitation at different seismic intensities are compared and analyzed using finite element models to supplement the test conditions. The test and analysis results show that the longitudinal displacements at each measurement point under longitudinal non-uniform excitation follow the same pattern except for differences in displacement magnitude and the vibration pattern of the tube and soil when the peak input acceleration reaches 1.00 g. As shown by both experimental and numerical simulation results, the soil acceleration amplification coefficients along the soil height fluctuate between 0.5 and 1.5. The pipe acceleration time curves and Fourier spectrum exhibit the same simulated and experimental pipe acceleration waveforms, and they both show significant amplification in the low to medium frequency band of 5–20 Hz. The testing and numerical simulated pipeline axial strain peak curves are similar and in good agreement, indicating the high reliability of the experimental results.

Numerical analysis of vortex-induced vibration on a flexible cantilever riser for deep-sea mining system

The flexible cantilever riser, as a special form of the marine riser, can be encountered in a deep-sea mining system, where the bottom of the long vertical lifting pipeline is connected with the intermediate warehouse. The main objective of this paper is to investigate the effects of the bottom weight caused by the intermediate warehouse and the flow speed on the dynamic responses of the cantilever pipeline. A quasi-3D coupling algorithm based on the discrete vortex method and finite element method is employed to calculate the unsteady hydrodynamic forces and vortex-induced vibrations of this pipeline in the time domain, respectively. We first simulate the VIV of a long flexible riser with two fixed ends in a stepped flow to validate the feasibility of the present method. Then, systematic simulations of cross-flow VIV of the cantilever riser are carried out under a wide range of bottom weights and different current speeds. The number of the vibration mode shows the decreasing tendency with the increase of the bottom weight. In a certain range of the weight, the number of the dominant mode remains unchanged, while the vibration amplitude declines with increasing weight. An amplitude jump phenomenon can be observed when the transition of the dominant mode in two contiguous mode clusters occurs. Moreover, the higher-order modes are excited with the increase of the current speed.

Random response analysis of hydraulic pipeline systems under fluid fluctuation and base motion

Aero hydraulic pipeline systems are subjected to internal fluid fluctuations and random base motions during operation, resulting in time-varying system parameters and nonstationary random responses. To analyse this situation, a nonstationary random response analysis method and a fatigue damage assessment formula for periodic time-varying systems under stationary random excitations are proposed. The nonstationary random response is described by a time-varying power spectral density function, which is strictly characterised by a set of pseudo responses of a periodic time-varying system under a series of harmonic excitations. A frequency-domain iterative solution format for the pseudo responses is constructed and combined with the fast Fourier transform to obtain the time-varying power spectral density function. A fatigue damage assessment formula is derived by discretising the time-varying power spectral density function of the pipeline stress in both the time and frequency domains. The proposed method only requires a few iterations at specific frequency points to calculate each pseudo response in a wide-band random airframe motion environment, showing high computational efficiency. A practical application concerning a section of the wingtip hydraulic pipeline is presented to demonstrate the correctness and efficiency of this method. The variations of pipeline responses and fatigue damage rates under fluid fluctuations and random base motions are also discussed.

Experimental modeling of far-field effects in buried pipelines subjected to reverse faulting

Buried pipelines often traverse a broad geographical area and are subject to permanent ground deformations (PGDs) induced by fault movement, lateral spreading, or landslides. These PGDs distort the pipeline locally and mobilize the soil resistance along the pipe interface and outside of the affected area. This study primarily investigates the influence of far-field and transitional soil-pipe resistance on the response of pipelines crossing reverse fault regions. A series of 2.5 m long, one-tenth experimental-scale buried pipelines, representing 60 cm diameter steel pipe at 1.5 m depth prototype in cohesionless sandy soil was subjected to reverse faulting movement. The reverse faulting was simulated by a split-box apparatus under 1g conditions. The end-joint fixities should represent the far-field and transitional effects in full-scale pipes. Four scenarios of far-field and transitional effects were simulated using different pipe-end fixities: (1) free: movement of the pipe end is free in all three directions, (2) axially-free: pipe ends movement is axially free but radially fixed, (3) axially-fixed: pipe end movement is axially fixed and radially constrained by springs, and (4) spring-restrained: pipe end movements are axially and radially restrained by springs. For representing axial soil-spring forces in far-field and transitional zones, two methods were considered: a) the axial soil-spring forces recommended by ASCE (1984) guidelines; and b) an analytical-experimental method that is a combination of an analytical solution, proposed by Vazouras et al. (2015), and a series of pull-out tests, conducted in this study. The radial springs were designed based on ASCE (1984) guideline for both Scenarios of 3 and 4. The results show that the boundary conditions of the pipe have a significant effect on the mode of failure and required fault offset for occurrence of such failure mode. It is also indicated that the ASCE (1984) guideline recommendations on the axial soil-spring representation results in less soil resistance than analytical-experimental method in far-field zone, which may result in a non-conservative estimation of the pipeline performance in fault zones.