Response Of Buried Pipelines Research Articles

Layered seabed effects on buried pipeline response to ice gouging

In ice gouging analyses, the seabed is often simplified as a uniform material domain, over-looking the potential complexities inherent in layered seabed formations, which are wide-spread in numerous Arctic regions. This study investigates the pipeline response into the distinct seabed configurations, including layered soft over stiff clay, layered stiff over soft clay, and uniformly soft and uniformly stiff compositions, to ice gouging. This was achieved through comprehensive large deformation finite element (LDFE) analysis, employing a Coupled Eulerian Lagrangian (CEL) algorithm. Incorporation of the strain-rate dependency and strain-softening effects involved the development of a user-defined subroutine and incremental update of the undrained shear strength within the Abaqus software. The pipeline is explicitly incorporated into the model, allowing for a detailed investigation of its response to ice gouging phenomena within these layered seabed scenarios. This research demonstrates that simplifying a layered seabed into a uniform can be misleading. Such an approach can lead to significant errors, potentially overestimating or underestimating pipeline response to ice gouging. By incorporating these complexities, engineers can develop more optimized designs with enhanced safety margins in Arctic environments prone to ice gouging phenomena.

Predictive models for assessment of buried pipeline response under seismic landslides in Iran

In seismic regions both in Iran and around the world, subterranean gas pipelines inevitably extend through high-risk areas prone to seismic landslides. The seismic landslide-pipe failure mechanism constitutes a continuum geomechanical challenge influenced by factors such as sliding mass configuration, pipe positioning relative to potential slope failure surfaces, and seismic input characteristics. In this study, response of steel pipeline buried in sand under seismic landslide action is analyzed by finite difference models using an advanced soil constitutive model. The numerical model is first validated based on the shaking table test results and then several dynamic analyses are performed using the selected records of the Iranian ground motions database. The outcomes of the dynamic analysis demonstrate that Arias Intensity (Ia) can be identified as an optimal intensity measure (IM) for predicting the seismic response of a slope-pipe system in terms of maximum pipe deflection, axial strain, and shear stress. Predictive models are then developed based on the optimal IM for estimating the pipe deflection, axial strain, and shear stress subjected to a seismic landslide. These proposed predictive models offer valuable insights for assessing the response of buried pipelines to seismic landslides in Iran within the framework of performance-based earthquake engineering.

Dynamic Behavior and Parameter Characteristics of Buried Pipeline in Airports

Buried pipeline, as one of the crucial facilities of airport ground engineering, has been extensively utilized for the transportation of petroleum, natural gas, industrial wastewater, and more. However, there are significant gaps in the research on the dynamic response of buried pipelines in airports under the action of dynamic traffic loads, which severely hampers the design and engineering quality of oil transmission pipelines. This study builds a three-dimensional finite element model to simulate the action of vehicles on the pipe–soil structure with actual loads. Moreover, the current research establishes a dynamic analysis model of pipe–soil interaction to analyze the material damping and load parameters. Using the structural dynamic response equation and Rayleigh damping calculation theory, this study investigates the change law of pipe dynamic stress and influencing factors and presents the recommended values of the parameters related to the pipe–soil interaction. Results are as follows. A damping ratio of 0.05 can enhance the time lag of the dynamic response of the structure and weaken the response peak. For the Rayleigh damping parameters, the viscous damping coefficient [Formula: see text] has almost no effect on the dynamic response of the pipe–soil structure, so it can be disregarded in the calculation. With the increase of the axial weight of the traffic load above the pavement structure, the peak value of each dynamic response quantity of the pipe–soil structure and load magnitude. The suggested value of the dynamic load coefficient of the pipe–soil structure is 1.5. Lastly, the earth pressure and dynamic load coefficients are suggested to take values for different load and axle type cases.

Designing, analyzing, and experimentally verifying a uniaxial shear box for investigating the length effect of buried pipelines during soil liquefaction

During an earthquake, buried pipelines can be threatened by various factors such as fault movement, ground motion, and soil liquefaction. Among these, fault movement and ground displacement have been identified as the most direct causes of pipeline fracture and rupture, as evidenced by previous earthquake disasters. While numerous studies have focused on the failure modes and mechanisms of pipelines crossing faults, little attention has been given to the dynamic uplift behavior of buried pipelines during soil liquefaction. To address such an issue, this study designed a uniaxial shear box to investigate the dynamic characteristics of buried pipelines during soil liquefaction. The box dimensions are 3600 mm × 1000 mm × 1100 mm and can embed a pipeline specimen of 3000 mm in length for testing. The seismic input motion direction is designed to be consistent with the axial direction of the pipeline to avoid lateral input motion influence. This study used DEEPSOIL analysis software to investigate whether the response of a uniaxial shear box under conditions of dry sand and saturated sand is consistent with theoretical analysis results. In addition, a preliminary test was conducted to ensure compliance with the requirements of subsequent pipeline tests, specifically on the uplift behavior of buried pipelines. The results showed that the soil dynamic responses under both dry sand and saturated sand conditions were consistent with the DEEPSOIL analysis software results. Furthermore, the pipeline test results verified that the input motion did not generate additional forces on the buried pipeline, but did indeed trigger soil liquefaction and cause the pipeline to uplift. These findings demonstrate that the uniaxial shear box designed in this study meets the design requirements and can be used to investigate the dynamic response of buried pipelines subjected to soil liquefaction under the influence of length effects in future studies.

Effects of groundwater table on buried pipeline response to a surface explosion

Effects of groundwater table on buried pipeline response to a surface explosion

Dynamic Behavior and Safety Criteria of Buried Concrete Pipeline System under Blasting

In urban blasting engineering, researching the dynamic response of buried pipeline is a method for evaluating the stability of the pipeline. The dynamic response of buried pipeline under blasting includes peak particle velocity (PPV) and peak effective stress (PES) on the pipeline. This paper aims to analyze the dynamic response of the concrete pipeline with bell-and-spigot joints under a metro-connected aisle blasting, and provide a PPV safety criterion for evaluating the stability of the field concrete pipeline. This includes an analysis of the dynamic response of the concrete pipeline in the field monitoring and numerical simulation. The monitoring results reveal that the PPV is affected by the field factor, such as the explosion source distance, and it is noteworthy that the Sadovsky’s formula considering the influence of explosion source distance (data correlation coefficient—0.708) has higher accuracy in predicting the PPV compared to the original Sadovsky’s formula (data correlation coefficient—0.632). The dynamic response distribution characteristics of the concrete pipeline are analyzed based on the numerical simulation, and the results show that the PES of the joint is three times stronger than that of the barrel. A PPV safety criterion (1.43 cm/s) is provided for the site to evaluate the stability of the concrete pipeline according to the dynamic response of the pipeline joint.

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.

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.

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.

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.

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.

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.

Different failure modes assessment of bell-spigot jointed ductile iron pipes under abrupt transverse ground movements

Abrupt ground movements induced by earthquake, landslide, tunnelling and excavation, etc., pose significant threats to the safety of underground jointed pipelines. Most previous studies have investigated the response of buried pipelines through experimental tests and numerical simulations, but analytical solutions for the safety evaluation of jointed pipelines are limited. In this study, enhanced analytical solutions of pipe bending moment and joint shear force are derived, in which the effects of different pipe-fault crossing configurations and pipe-soil interactions are considered. Then, the allowable offset distances are investigated using the proposed solutions, respectively, for three different failure modes, i.e., joint shear failure, pipe bending failure, and joint pull-out failure. The results show that the joint pull-out failure governs the pipe safety when the burial depth is relatively shallow, while the pipe bending failure dominates when they are buried deeply. The worst pipe-fault crossing position is not at the pipe joint or the midspan of the pipe segment, but at one tenth of the pipe segment adjacent to the joint. The results offer new insights into buried DI pipe failure mechanism and provide a basis for the protection of buried DI pipes under abrupt transverse ground movement conditions.

Field experiment and numerical investigation on the mechanical response of buried pipeline under traffic load

The acceleration of global urbanization and an increasing intersection of roads and buried pipelines pose a certain threat to the operation safety of pipelines. In this paper, the mechanical response of the X65 pipeline under empty-load, half-load, and full-load traffic loads is investigated via field experiments. The numerical model considering the nonlinear interaction between the pipe and the soil is established. Moreover, an accurate simulation of dynamic vehicle load is achieved by Dload user-defined subroutine. The error between the numerical calculation results and the field experiment results is less than 5 %. On this basis, the influence of five important factors, such as vehicle mass and buried depth, on the axial stress of pipelines is further explored. The results show that the traffic load leads to vertical bending deformation of the pipeline and local deformation of the wheel rolling position. The axial tensile stress generated at the bottom of the pipe is superimposed on the axial tensile stress generated by the internal pressure Poisson effect. The vehicle mass most significantly affects the axial stress of the pipeline, which is generally less than 100 MPa. Furthermore, the operating conditions of the pipeline with large coverage in service are calculated based on Python and ABAQUS co-simulation calculation of 1280 working conditions. The particle swarm optimization-support vector regression (PSO-SVR) hybrid machine learning model is used to accurately predict the axial stress of the buried pipeline under traffic load, and the corresponding correlation coefficient reaches 99.77 %. The research results reveal the mechanical response law of buried pipeline under traffic load, which can provide a basis for the applicability evaluation of buried pipeline in service under traffic load, and accurately evaluate the safety state of buried pipeline.

Seismic Sequence Effects on Buried Pipelines Crossing Nonuniform Sites with Ground Settlement by Dynamic Centrifuge Test

The deformation and residual strength of the buried pipeline caused by the earthquake in nonuniform sites has an important influence on the safety of the pipeline. Most of the previous research focuses on the permanent ground deformation (PGD) caused by fault or transient ground deformation (TGD) due to seismic wave propagation independently. The mechanical character of buried pipelines crossing nonuniform sites during seismic sequence after ground settlement has not been studied. This article carried out a dynamic centrifuge experiment to simulate the seismic response of buried pipelines of polyvinyl chloride (PVC) and aluminum alloy (AL) horizontally crossing the loose and dense site and study the residual strength of pipelines after an earthquake. Two simulated seismic waves with 0.6 g and 0.3 g of input peak ground accelerations (PGAs) were inputted in sequence to simulate the strong and weak earthquakes. The deformations of ground and pipelines were obtained during and after seismic. The numerical model consistent with the experiment was established and compared with test, and it was found that the strain of pipeline caused by TGD was different between numerical and experimental results, especially in the loose site. The mechanical model of the pipeline by earthquake indicated that the total strain of the pipeline was composed of bending deformation by PGD and axial deformation by TGD. PGD caused by a strong earthquake had great effects on the deformation and residual strength of the pipeline. The strain of pipeline by TGD was compressive‐extensional alternating mode between the loose and dense site and the strain amplitude reached peaks near the block interface in the loose site. The residual strain of pipeline in the dense site was a compressive strain, while in the loose site, it was compressive‐extensional alternating mode and varied with the stiffness of the pipeline.

An innovative solution for the dynamic response of buried pipelines in layered transversely isotropic soil under pavement structures

The interaction between a buried pipeline and the surrounding soil under dynamic loads has attracted the attention of researchers. In this paper, a modified scaled boundary finite element method (SBFEM) based on the mechanical derivation method is proposed to determine the dynamic response of the buried pipeline in layered transversely isotropic soil under the pavement structure. A similarity line that replaces the similarity centre of the conventional method was introduced in the modified SBFEM. As a result, a new stiffness matrix equation was established for layered soil. The accuracy of the proposed algorithm was confirmed through numerical examples. Therefore, the effects of the thin layer elastic modulus, pipeline cushion thickness, pipeline radius, pipeline buried depth, and location of the cavity under the pipeline on the dynamic response of pipelines were studied under dynamic pavement loads. The parametric analysis gives a reliable numerical solution for engineering problems.

Analytical method for the mechanical response of buried pipeline under the action of strike-slip faulting

Buried pipelines are commonly damaged when laid across strike-slip faults, always leading to some level of destruction with fault movement. The moment of the neutral axis of a pipe section was obtained by integration, and the equations for the bending moment and the bending strain on a pipeline’s section were presented here, based on a trilinear stress–strain model. The calculation method for the lateral soil pressure and pipeline’s bending strain near the fault-crossing point was improved. Lateral soil pressure was regarded as being related to lateral pipeline movement and, for accurate calculation, this part of the pipeline was divided into finite element segments. An iterative process for solving for pipe bending strain was derived, and the algorithm and program for calculating bending strain and the potential damage position of the pipeline’s sections was compiled based on Matlab software. Compared with finite element method (FEM) results and the current standard method, in the situation of a pipeline being in tension under the action of a strike-slip fault (intersection angle < 90°), the result of the proposed method is in good agreement with FEM results. This shows that the proposed analytical method possessed a good reference value for the strain response analysis of tensile steel pipelines under strike-slip faulting.

Influence of the topographic effect on the seismic response of buried pipelines

Detailed study of the response of pipelines during seismic excitation can help reduce physical and financial losses during and after an earthquake. The current research investigated the seismic behavior of pipelines passing through variations in topography using two-dimensional and three-dimensional modeling. Their behavior has been modeled at the crest and toe of a slope and during longitudinal passage through the topography. The effects of the soil stiffness, diameter-to-thickness ratio of the pipeline, height-to-half-width ratio (shape factor), and input wave characteristics on the performance of the pipeline have been investigated. The results indicate that topographic effects can increase the strain on pipelines and the factors studied are crucial to accommodating this potential hazard.

Multi-fidelity approach for uncertainty quantification of buried pipeline response undergoing fault rupture displacements in sand

A new efficient approach for uncertainty quantification of pipeline structural response undergoing reverse-slip fault rupture displacements in sand is presented using multi-fidelity Gaussian processes. Uncertainty quantification problems generally take large numbers of scenarios to be analysed considering variations in the influencing parameters. Analysing large numbers of computationally expensive detailed geo-technical numerical models is practically not feasible. Hence, a multi-fidelity approach employing Gaussian process is proposed to tackle this problem which combines the accuracy of a relatively few number of detailed geo-technical numerical models and the efficiency of large numbers of simplified numerical models to track the uncertainty response. The detailed model utilizes a previously validated pipe-soil finite element (FE) model including a non-linear sand constitutive model implemented in finite element software ABAQUS. The simplified model utilizes beam element pipe and bi-linear soil springs. The multi-fidelity model is first trained using data from high-fidelity and low-fidelity model analyses, thereafter cross-validated and subsequently used to quantify uncertainty in the peak compressive strains generated and to identify the most sensitive input variables. Finally, fragility curves are derived for a site specific pipe-soil fault rupture problem.

Seismic response analysis of buried pipelines with the high drop

To study the seismic response of buried pipelines with the high drop, a small-size test based on shaking table was conducted to analyze the effects of pipeline wall thickness, pipeline diameter and inclination angle on the seismic response of buried pipelines with high drop. Meanwhile, a finite element model was proposed for numerical simulation. The research results show that the peak axial strain of the pipeline increases with the decrease of the thickness and the diameter of the pipeline in the action of seismic waves and the increase of the inclination of the pipeline. Based on the results of experiments and finite element simulations, a regression equation of the peak axial strain of buried pipelines with the high drop was developed with the consideration of the effects of the ratio of wall diameter to wall thickness and height. Meanwhile, some valuable conclusions were obtained for the instruction of the seismic design of pipelines in engineering.