Response Of Pipelines Research Articles

Effects of Laying Depth and Pipe Arc Length on the Mechanical Performance of Large-Diameter Cold-Water Pipes during Float-and-Sink Installation

The successful operation of a large-diameter cold water pipeline installation is crucial for harnessing the potential of ocean thermal energy conversion. However, there is a shortage of research focused on mechanical performance analysis during installation. This study establishes a pipeline response analysis model based on a nonlinear beam theory to elucidate the underlying mechanical behaviour. Employing the method of singular perturbation, the general solution for the exterior region of the pipeline, the solution at the boundary layer, and the valid solution across the entire domain are derived. A comparison with numerical solutions is conducted to validate the accuracy and effectiveness of the theoretical model. Based on the theoretical analysis, the influence of installation depth and pipeline curvature on the pipeline’s shape, tension, curvature, and stress is discussed. The results indicate that increasing the installation depth leads to intensified pipeline bending and significant deformation, reaching a maximum bending moment of 3.92 MN∙m at a distance of 50~100 m from the bottom of the pipeline. The results also show that, as the pipeline’s arc length increases from 0 to 100 m, the bending curvature, Von Mises stress, and bending stress exhibit a trend of initial growth followed by a decline, peaking at 7.45 MPa, and 6.83 Mpa, respectively, while the actual tension and axial tension decrease initially and then increase, reaching −0.17 MN and −0.17 MPa, respectively, at the maximum arc length. The findings of this study provide valuable insights for practical cold-water pipe installation and laying.

Numerical Analysis and Experimental Study on Seismic Coupling Response of Pipe-Soil System Under Bidirectional Seismic Excitation

The seismic response of buried pipeline is significantly affected by the soil around the pipeline. In this study, a numerical analysis model of the pipeline and the soil around the pipeline is built, and the finite element numerical analysis of its seismic response law is conducted to address the problem of pipeline soil seismic coupling response. A shaking table test of the seismic response of buried pipeline under two-way seismic excitation is performed based on the developed two-way layered shear continuum model soil box. The peak strain response at the middle section of the pipeline grows fastest, the peak strain of the pipeline under non-uniform seismic excitation constantly exceeds that under uniform excitation, and the axial strain of the pipeline exhibits more sensitivity to earthquake than the bending strain, as indicated by the results of numerical analysis and shaking table test. The peak value of soil acceleration response under non-uniform excitation exceeds under uniform excitation. The displacement of soil increases with the height. The pipeline soil interaction becomes more intense under non-uniform excitation, and the relative movement between pipeline and soil becomes more significant. The seismic excitation more significantly affects the axial displacement of soil. The peak value of soil acceleration response varies from larger along the pipeline to larger along the axis with the increase of the loading grade. A slight difference exists between the peak value of axial and transverse acceleration response of the pipeline. The peak value of pipeline acceleration response declines in the axial direction than the peak value of soil acceleration response, whereas it rises in the transverse direction than the peak value of soil acceleration response, especially under non-uniform excitation. As revealed by the above results, the effect of bidirectional non-uniform seismic excitation on the lateral pipeline soil interaction is enhanced, and soil is more seriously damaged.

Performance of parallel double pipelines under non-uniform seismic excitation

This paper investigates the structural safety of parallel double-buried pipelines under non-uniform seismic excitation considering the soil-pipeline interaction. A three-dimensional nonlinear numerical model has been established to study the effects of seismic wave propagation and ground motion intensity, as well as the pipeline internal pressure and spacing between the pipelines on their structural safety. The dynamic response of the parallel double buried pipelines was evaluated in terms of the acceleration amplification, settlement of ground surface, and strain, displacement, and elliptical deformation of the pipeline. The results demonstrate that the seismic response of buried pipelines under non-uniform excitation has obvious nonlinear characteristics, especially when the loading intensity is high. It is found that the internal pressure has virtually no effect on the site acceleration response, but it amplifies the settlement of the ground surface. Meawhile, it inhibits the elliptic deformation of the pipeline. Furthermore, the variation of the elliptic deformation of parallel buried pipelines is found to be the same for different pipeline spacings considered in this study. On the other hand, the pipelines spacing has a significant influence on their seismic response as the interaction between the two pipelines gradually decreases with the increase in the spacing.

Study on the calculation method and structural dynamic response of buried pipeline subjected to external explosion load based on multiphase coupling

When the buried pipeline is subjected to the external explosion load, stress and deformation will occur. When the stress and deformation value exceed a specific range, it will affect the normal use of the buried pipeline. In this paper, a multiphase coupled model of pipeline, soil and fluid within the pipeline is established. The penalty function coupling method is used to describe the load between soil and pipeline and the fluid within the pipeline. By specifying the boundary conditions of the coupled system, the multiphase coupled global solution variational principle function of the soil-pipe-fluid is derived. According to the established multiphase coupled calculation method, the numerical simulation analysis of the response of pipeline to external explosion is carried out. The maximum error of the experimental and numerical simulation results is about 5%, which verifies the accuracy of the multiphase coupled calculation method. The soil-pipeline-fluid multiphase coupled numerical calculation model is established to analyze the response of the buried pipeline under the external explosion load. The results show that during the explosion shock wave propagating in the soil, the peak value of the explosion pressure in different positions in the soil of the gas pipeline is greater than that of the oil pipeline. As for the structural response, the maximum radial displacement value of the oil pipeline is reduced by 3.83 mm compared with the gas pipeline, the maximum stress value is reduced by 3.75%. The maximum radial displacement value of the pipeline with a fluid velocity of 1.5 m/s is 2.65 mm larger than that of the pipeline with a fluid velocity of 1 m/s, and the maximum stress value is increased by 5.72%. The deformation resistance and explosion resistance of the oil pipeline are both stronger than that of the gas pipeline. The higher the fluid velocity, the weaker the pipeline's resistance to deformation and explosion will be.

Experimental Study on Pressure Pulsation and Acceleration Response of Fluid Conveying Pipeline Under Multi-Excitation

Abstract The fluid conveying pipelines are often subjected to internal fluid fluctuation excitation in the hydraulic pump and external base excitation from the aircraft engine rotor. To investigate the acceleration response of the pipeline and pressure pulsation response of fluid, the vibration tests of the pipeline under base excitation, fluid fluctuation excitation, and multi-excitation are conducted. A set of test bench and test schemes of pipeline system under multi-excitation are designed. The test data are collected by a piezo-electric pressure sensor and a three-direction acceleration sensor. By analyzing the test data, the following results can be obtained: Under base excitation, the internal fluid still has a weak pressure pulsation response even without fluid fluctuation excitation. However, the pressure pulsation response remains unchanged with the increase of base excitation amplitude. Under fluid fluctuation excitation, the amplitudes of vibration responses at fluid fundamental frequency fp increase with the increase of pump pressure except at 9 MPa and 15 MPa. The natural frequency of the pipeline is close to 3fp when the pump pressure is 9 MPa and 15 MPa, respectively, and the pipeline system will have resonance. Under multi-excitation, the amplitudes of vibration responses are close to the superimposed amplitudes of two single source excitations at fb = 175 Hz and fp = 298 Hz. The vibration responses appear to beat vibration at fb = 298 Hz and fp = 297.6 Hz. The relevant test scheme and test data analysis adopted in this paper have important reference values for the in-depth study of pipeline vibration under multi-excitation and engineering practice.

Analysis of the Dynamic Response of Oil and Gas Long-Distance Pipelines Under Multipoint Excitation of Different Seismic Intensities

In this study, a pipe-soil finite element analysis model was built using the shaking table test results of buried pipelines that were achieved through longitudinal multipoint excitation and multipoint excitation under different seismic intensities, so as to numerically simulate the seismic response of buried pipelines under longitudinal multipoint excitation and multipoint excitation under different seismic intensities. As indicated by the result of this study, the numerical calculations and the shaking table test findings in terms of long-distance oil and gas pipelines under longitudinal multipoint stimulation were well consistent, such that the validity of both sets of results was verified. The peak pipe stresses during the multipoint excitation under different seismic intensities declined by 13.8% to 30.9% compared with case 2 longitudinal multipoint stimulation. The acceleration of the pipe and the soil was reduced rapidly as the measuring point moved farther away from the pipe’s leftmost distance. The displacement variation of the oil and gas pipelines under longitudinal multipoint excitation suggested that the soil displacement was increased with the length of the monitoring point from the bottom of the soil box for different elevations of the same section. The soil displacement declined notably for the same stretch at the identical elevation with the reduction of seismic intensity. The findings of this study can lay a basis for in-depth research on the effect of multipoint stimulation with different seismic powers on the seismic response of underground pipes.

Structural response of the spiral-welded pipelines buried in different uniform soil types to the strike-slip fault

Buried steel pipelines, which are widely used in, often face the threat of Permanent Ground Deformations (PGD) caused by fault crossings. The structural response of the pipeline can be influenced by the pipe-trench-backfill interaction, resulting in various hoop strains, axial plastic strains, and consequently, formation of wrinkles at different locations in the fault zone. This paper investigates the structural response of spiral-welded pipelines at strike-slip fault crossings by incorporating the burial effects in a range of different soil materials. A dynamic explicit analysis is used to address the convergence issue commonly encountered in the analysis of post-buckling problems. The helix angles and the burial depth effects in different soil types and pipeline-ground interaction angles are examined. The study provides valuable insights into the influence of burial conditions and corresponding helix angle on the performance of spiral-welded pipelines in strike-slip faults.

Physical modeling of the influence of tunnel active face instability on existing pipelines

In congested urban areas, earth pressure balance (EPB) shielding is commonly adopted to alleviate tunneling effects on surrounding structures. Tunnel active face instability can cause excessive ground movements, which threaten the serviceability of nearby underground pipelines. However, previous studies mainly focused on tunnel face support pressure and tunnel face failure induced ground movements, while pipeline deformations due to tunnel active face instability are seldomly explored. In this study, a series of physical model tests are designed and conducted to investigate the effects of tunnel cover to diameter ratio (C/D) and normalized horizontal distance (H/D) between tunnel face and existing pipeline on three-dimensional pipeline deformation mechanisms. Tunnel active face instability induces excessive settlements and tensile strains in the existing pipeline when it is located at 0.1 D ∼ 0.3 D in front of tunnel face. By increasing H/D ratio from 0.1 to 0.5, the maximum settlement and tensile strain of the existing pipeline decrease by up to 64.8% and 59.9%, respectively. But the maximum settlement and tensile strain of the pipeline only decrease by up to 14.9% and 7.3%, respectively, as C/D ratio increases from 1.0 to 1.5. Obviously, the effects of C/D ratio on pipeline response are less prominent than that of H/D ratio. The measured results are used to verify calculation charts for directly predicting maximum tensile strains of existing pipelines due to tunnel face active instability induced differential ground movements.

Analysis of the Buried Pipeline Response Induced by Twin Tunneling Using the Generalized Hermite Spectral Method

For the sustainability of economic, ecological and social development, the safety of infrastructure, including buried pipelines, is extremely important. Undercrossing tunneling can compromise the safety of buried pipelines because of deformations, cracks and dislocations, which can result in wasted resources, environmental pollution and economic losses. Therefore, it is important to assess the pipeline response accurately during tunnel excavation. This paper proposes a generalized Hermite spectral solution to estimate the pipeline response induced by twin tunneling. The proposed solution is formulated by a truncated series of Hermite functions and it is available in an unbounded domain. On the basis of the two-stage analysis method, a general formula for calculating the soil greenfield displacement induced by twin tunneling is first derived using the superposition principle. To obtain the final solution, the soil greenfield displacement and pipeline displacement are expanded using two truncated series of Hermite functions, and the governing differential equation of pipeline displacement is subsequently simplified into a linear algebraic system. After solving this system, a general solution for calculating pipeline displacement is formulated. Then, the convergence of the developed solution is proven, and its validity is verified against existing theoretical solutions and centrifuge test results. The effects of the truncated series number and its scaling factor are investigated. Finally, parametric studies are conducted to discuss pipeline responses induced by twin tunneling.

Machine learning‐based prediction of the seismic response of fault‐crossing natural gas pipelines

AbstractHerein, we utilized machine‐learning (ML) and data‐driven (regression) techniques to tackle a critical infrastructure engineering problem—namely, predicting the seismic response of natural gas pipelines crossing earthquake faults. Such a 3D nonlinear problem can take up to 10 h to solve by performing finite element analysis (FEA), considering the length of the pipeline and a large number of pipe and soil elements. However, the ML and data‐driven techniques can learn the projection rule of input‐output and predict the pipeline response instantaneously given a set of input features. In addition, the well‐trained ML model can be implemented for regional‐scale risk and rapid post‐event damage assessments. In this study, the input for ML comprised approximately 217K nonlinear FEAs, which covered a wide range of combinations of soil, structural and fault properties and yielded critical pipe strain responses under fault‐rupture displacements. We adopted various regression models and physics‐constrained neural networks, which can accurately and rapidly predict the tensile and compressive strains for a broad range of probable fault‐rupture displacements. Performances of various ML and conventional statistical models were systematically examined. Not surprisingly, neural networks exhibited the best performance for this multi‐output regression problem, in whichR2 > 0.95 was achieved for a wide range of fault displacement (FD) levels. Further, we used the trained neural network with 14.5 million Monte‐Carlo‐generated input samples to predict the maximum tensile and compressive strain curves of pipelines. This new dataset aimed at filling the missing input‐output points from the 217K FEAs, and improved the accuracy of the prediction of probability of failure for natural gas pipelines under FD hazards.

Investigation of the Longitudinal Mechanical Response of Pipeline or Tunnel Under Reverse Fault Dislocation

Investigation of the Longitudinal Mechanical Response of Pipeline or Tunnel Under Reverse Fault Dislocation

Modeling pipe-soil interaction under vertical downward relative offset using B-spline material point method

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.

Dynamic response and safety analysis of polyethylene pipeline under rockfall conditions

AbstractThe safety of buried gas pipelines in mountainous cities is at risk due to potential hazards such as landslides and rock falls. To ensure the safety of pipelines, this paper develops a three‐dimensional dynamic response model to reveal the impact of rockfall radius, rockfall impact velocity, and pipe burial depth on the dynamic response of buried polyethylene pipelines (PE pipelines) under rockfall conditions. Subsequently, an orthogonal experimental design and analysis of variance (ANOVA) are performed to identify critical factors. Ultimately, a multi‐factor limit state equation is constructed to assess the safety of PE pipelines accordingly failure prevention actions for buried gas pipelines under the impact of rockfall is specified. Overall, this proposed method contributes to safety analysis of buried PE pipelines in rockfall‐prone areas.

Fluid-induced vibration analysis of pipe based on the transfer matrix method and added mass, added damping analogy method

In this paper, the 14-equations of pipeline system were written as matrix forms in frequency domain with Laplace transformation and further solved by transfer matrix method (TMM). Moreover, the added mass and added damping models were established and combined with the TMM for decoupling investigated the Turbulence-Induced Vibration (TIV) of clamped-clamped pipe system. Firstly, the feasibility of the TMM for analyzing the frequency responses of water-filled pipelines with free support boundary conditions and the added mass, added damping for decoupling investigation of TIV were finished verify. Then the frequency responses for Fluid-Structure Interaction (FSI) problems of pipeline with different flow velocities were acquired. The results indicate that the calculated frequencies agree well with corresponding data yield from Galerkin method. And the increasing flow velocity results in a decreased amplitudes of the frequency responses due to the effect of fluid added damping. Those results of the research in this paper implied that the decoupling method composed of the TMM that considered the added mass and added damping is validity and accuracy for frequency response analysis of the pipeline.

Fracture Response of X80 Pipe Girth Welds under Combined Internal Pressure and Bending Moment.

In order to determine the effect of defect size on the pipeline fracture performance of girth welds in oil and gas pipelines, ABAQUS was used to simulate the fracture responses of X80 pipelines with girth weld defects under internal pressure and bending moment conditions based on damage mechanics. In particular, the length and depth of defects were parametrically studied; the defect depth range was 20-80% of the wall thickness, and the circumferential length range of the defects was 5-20% of the pipeline circumference. The results show that, under the combined action of internal pressure and bending moment, the defect depth was more associated with adverse effects than the circumferential length of the defect. The failure load did not linearly decrease as the size of the defect increased, but when the depth of the defect reached a certain value, the failure load suddenly decreased.

Numerical analysis of buried pipelines response to bidirectional non-uniform seismic excitation

The multi-directional, spatially variable earthquake motion is a primary cause of pipeline damage during earthquakes. A comprehensive finite element model considering soil nonlinearity and pipeline-soil interaction nonlinearity was established and validated based on shaking table tests and then employed to investigate the difference in response of buried pipelines subjected to longitudinal unidirectional (UD) and bidirectional (BD) horizontal non-uniform excitations. The responses were evaluated in terms of the acceleration and axial strain time histories along with the peak axial strain, hoop strain, and radial strain in the pipeline cross-section. The results demonstrate that the strain response and axial force of the pipeline under BD excitation are 50%-70% larger than under UD excitation. The large difference is attributed to the increase in maximum frictional force and the delay of the strain growth inflection point under the BD excitation. It was also observed that the pipeline cross-section experienced only lateral ovalization under the UD excitation. For the BD excitation, the cross-section experienced both lateral ovalization and vertical ovalization. Finally, the existence of the Y-direction seismic component in the BD excitation did not significantly change the X-direction acceleration response of the pipeline but increased the peak values.

Determining the Soil Modulus for Use in Soil–Pipe Interaction Modeling

Research and engineering practice for the earthquake, landslide, or tunneling response of underground pipelines has focused on large ground deformation (LGD) effects, recognizing that LGD often causes the most serious local damage in buried pipelines. The adjacent soil reaction that develops as the pipe moves, i.e., soil–pipe interaction, is of key importance in the response of underground pipelines subject to LGD. A finite-element elastoplastic model can be used to analyze the soil–pipe interaction, and the model requires a soil modulus to simulate the force versus displacement behavior. In the simulation of soil–pipe interaction, a secant modulus associated with high stress and strain should be used in the finite-element model rather than an initial tangent modulus. This research provides a strain-compatible secant modulus that can be used in a finite-element analysis (FEA) of soil–pipe interaction for lateral, upward, downward, and oblique pipe movements. The favorable comparison between the experimental data and the FEA using the strain-compatible secant modulus implies that the proposed approach is suitable to predict soil–pipe behavior under large ground deformation.

Buckling response of subsea pipeline with irregular corrosion defect under external pressure

The subsea pipeline is prone to corrosion due to the combined influence of a complex environment and internal fluid. The corrosion defect results in the local thinning of the wall thickness of the pipeline, affecting the pipeline collapse response under external pressure. In the present study, the buckling response of subsea pipelines with irregular corrosion defect is analyzed. First, a method for calculating the critical buckling pressure of pipelines with irregular corrosion defect is proposed. The accuracy of the proposed method is verified by comparing it with finite element (FE) results and experimental tests. Then, the effects of defect size, steel grade and diameter-to-thickness ratio on the defect interaction and critical buckling pressure of the pipeline are explored. Finally, the application range of the present method is extended by considering defect length, initial ovality and internal pressure.

Vortex-Induced Vibration Response Features of A Submarine Multi-Span Pipeline via Towing Tank Experimental Tests

In offshore engineering, the phenomenon of free span often occurs, and the pipeline may have multiple free spans adjacent to each other, forming a multi-span pipeline. The interaction of different spans makes the structural vibration characteristics more complex, which may change the fatigue characteristics of the pipeline and affect the safety of the structure. In this paper, model tests were designed to explore the vortex-induced vibration (VIV) characteristics of multi-span pipelines and investigate the multi-span interaction mechanism. The experimental study mainly focused on the dynamic response of double-span pipelines, and further extended to triple-span pipelines, hoping that the results can be applied to more complex environment. The effects of span-length ratio, buried depth and axial force on VIV of the pipeline were investigated and discussed. The dynamic response of the pipeline varied with the span length. There was obvious interaction between different spans of multi-span pipelines, and the pipe-sediment interaction obviously affected the vibration characteristics of pipeline. The differences of pipeline burial depth and axial force changed the structural stiffness. With the increase of buried depth, the response amplitude presented a downward trend. The spanwise evolutions were asymmetric caused by the pipe-sediment interaction and multi-span interaction. The results can help to identify multi-span pipelines in engineering, and realize the prevention and control of free spans.

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.