Buried Pipeline Systems Research Articles

Multi-physics coupled simulation and experimental investigation of alternating stray current corrosion of buried gas pipeline adjacent to rail transit system

As the gradual emergence of alternating current (AC) electrified rail transit system in urban areas, buried gas pipeline adjacent to the system will be seriously corroded by induced alternating stray current. These buried gas pipelines are at serious risk of electrochemical corrosion, which leads to safety and environmental threaten. In order to study the distribution of alternating stray current corrosion on pipeline surface on a larger spatial scale, this paper conducted numerical simulation and experimental validation of alternating stray current corrosion of buried gas pipeline. In the numerical simulation model, coupling between different physical fields are realized through the relationship between current density of pipe-to-soil interface, electrolyte, and electrodes. Proposed numerical method based on coupled multi-physics in this paper are in good agreement with experimental results under different influencing factors. A novel evaluation index was proposed to assess the corrosion risk within different zones on the pipeline surface. Results show that corrosion distribution is greatly influenced by spatial interaction between buried pipeline and rail transit system including crossing angle and parallel distance. Besides, alternating stray current corrosion on buried gas pipeline are proved to be both affected by dynamic characteristics due to AC fluctuation and operation mode of locomotive.

Influence of crossing fault position and site soil on the mechanical properties of bellows joint connected buried pipelines under direct shear

Buried pipeline systems are vulnerable to joint damage in earthquakes. Previous studies have shown that bellows joints are effective in increasing deformation capacity and reducing the axial force of the main pipeline. However, the effectiveness of bellows joints in enhancing the deformation capacity of the pipelines is affected by the location of the crossing fault and the soil at the site. This paper constructs and validates a finite element model of a buried steel pipeline connected by a bellows joint using ABAQUS to investigate this issue. The effects of fault location, soil properties, and internal pressure on the bellows joint connected pipelines were analyzed using a finite element model. The results indicate that the bellows joints exhibit the best energy dissipation and deformation enhancement when the fault passes directly through the joints. Bellows joints in soft soil are better at dissipating energy, reducing pipe deformation, and mitigating pipe damage compared to those in hard soils. The internal pressure is helpful to increase the mechanical properties of the pipelines. The findings can provide some guidance for pipeline design and mitigation strategies for ensuring the reliability and safety of buried pipeline systems in earthquake-prone areas.

Experimental Verification on Deep Learning based Monitoring Algorithms for Early Detection of Damage in Buried Pipelines

Recent increases in buried pipeline damage accidents due to third-party interference have significantly heightened attention towards buried pipeline monitoring. Especially, as the sudden damage can lead to large-scale leakage, there is a necessity for preemptive response and maintenance. However, the application of a structural health monitoring approach is difficult, since the extensive network of buried pipelines, stretching over thousands of kilometers, exhibits diverse noise environments and propagation characteristics. As a result, challenges within the buried pipeline system frequently lead to damages being overlooked. In this study, introduces a deep learning-based pipeline damage monitoring algorithm, specifically designed to early detection of accidents caused by third-party interference. This algorithm integrates a CNN-based anomaly detection model, advanced signal processing for data preprocessing, and TDoA-based source localization. The training and test data set are the acquisition under completely independent conditions, which has been experimentally validate for applicability across various environments for buried pipelines. Moreover, both the training and test dataset acquisition were performed using accelerometers on in-service buried pipelines, each with diameters of 1,100 mm, 1,200 mm, and 2,200 mm, extending over lengths ranging from approximately 200 to 500 meters. Despite the independent conditions of the datasets, our study yielded over 95% accuracy in early detection, with the results being in good agreement with the actual excavate locations.

Numerical Study on the Optimal Thermally Affected Region of a Buried Oil Pipeline.

Crude oil pipeline transportation is usually a closed process under a certain depth of burial, and the condition of oil in the pipeline changes with the continuous decline of temperature during the transportation process. The safety and energy consumption of pipeline transportation are closely related to the accurate prediction of oil temperature. It is a popular technique to use the thermally affected region to overcome the problem of an unclosed calculation domain caused by the semi-infinite soil around the pipeline. However, there is no clear and unified guidance on the thermally affected region at present, and improper region size may lead to a loss of the accuracy of the pipeline system. Therefore, our study answers two questions about the optimal form of the thermally affected region and its economic scope of application. The coupled solution of heat transfer and flow in a tridimensional numerical model is carried out, and the thermodynamic influences of the geometric shape and range of the thermally affected region on the buried pipeline system are investigated. The results show that the rectangular region is more suitable for the modeling of buried oil pipelines, and a region with 16 m width and 9 m height is recommended for the conventional case.

Instant EOFF measurement error in cathodically protected pipelines: A parametric assessment study

Buried pipeline systems benefit from mitigation wires (earthing systems) in order to be protected against electric shock hazards. Moreover, cathodic protection (CP) systems are incorporated into pipeline systems to provide protection against corrosion by injecting an impressed DC current. DC decoupling devices are normally installed between the pipeline's metallic wall and the earthing wire, functioning as a filter that blocks the DC component (of the CP system) while allowing the hazardous AC interference current to be dissipated into the earth. However, the internal capacitance of the DC decoupling devices introduces an error in the routine survey measurement of the CP effectiveness, as frequently reported by pipelines’ system operators. In this paper, the factors influencing this measurement error are investigated by modeling the electrical behavior of the CP-pipeline system. This investigation concluded that the capacitive discharge time constant and by extension, the measurement error highly depends on the pipeline resistance to remote earth (coating resistance), as well as on the number and the capacitance C of the capacitive DC decoupling devices. To this extent, methods for minimizing Eoff measurement error are proposed.

Leak Location for Urban Elbowed Water Pipe Based on Complex-Optimized FastICA Blind Deconvolution

Previous research has primarily focused on leak diagnosis algorithms under the interference of outside environment noise. However, the former algorithms in leak detection are easily affected by noise from the pipe, especially the one that contains elbow noise. This article was mainly concerned with the effective and reliable approach to precisely locate leaks in the buried elbow pipeline system. To overcome the drawback of elbow noise interference and extract the leak source from the mixing signal in the greatest extent, this article proposes a novel frequency-domain-independent component analysis (ICA) blind deconvolution algorithm, which is based on a popular optimized FastICA (O-FICA) called complex-optimized FastICA (CO-FICA) algorithm. In comparison, CO-FICA differs from the time-domain blind convolution separation (T-BCS) algorithm, which transforms complicated time-domain convolution into a simple frequency-domain product problem. Compared with the conventional complex FastICA (C-FICA), the proposed CO-FICA method does not need to estimate signal statistics at each step, but it displays more excellent performance in convergent speed and separated precision. Altogether, the results from this study demonstrate that the localization precision of the proposed method is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 87\%$ </tex-math></inline-formula> under the interference of elbow noise.

Application of Seismic Fragility of Buried Piping Systems with Bellows Expansion Joints

Bellows expansion joints are known to have a large displacement capacity and can thus be potentially used to improve the seismic performance of buried piping systems. However, there are no guidelines on the installation of bellows expansion joints for the seismic performance improvement of buried piping systems. Furthermore, there are very few studies on the seismic performance of buried piping systems with bellows expansion joints. In this study, therefore, we performed seismic fragility analysis according to the installation conditions to obtain basic data for the installation guidelines of bellows expansion joints. Therefore, in this study, an experimental test was performed on bellows expansion joints considering the characteristics of earthquake loading conditions, and a 3D finite element (FE) model using the ABAQUS platform was developed and validated based on the experimental results. This model was verified by comparing the force-displacement relationship and energy dissipation. Leakage occurred at a displacement of 113.6 mm in the experiment, and the FE analysis result was also applied up to the same displacement. In the case of energy dissipation, an error between the FE model and experimental result was determined not to be significant. However, the appearance of such physical performance errors is due to the manufacturing errors resulting from the bellows forming process and the variability of material properties. Finally, seismic fragility analysis of buried pipeline systems with bellows expansion joints was performed. In addition, the following cases were used for analysis according to whether bellows were applied or not: (1) without a bellows expansion joints; (2) with a single bellows expansion joint; and (3) with two bellows expansion joints. In conclusion, it was found that the seismic performance of the buried pipeline system was improved when bellows were applied. However, the effect of the seismic fragility curve according to the increase in the number of bellows was insignificant.

Failure prediction of buried pipeline by network-based geospatial-temporal solution

Corrosion is a severe threat to the integrity of buried metal pipes due to the interaction of pipe materials with the surrounding soils. A review of the published literature shows that there are serious challenges for engineers to accurately predict failures in the buried pipeline system. In this paper, a network-based geospatial-temporal solution is developed to predict the risk of pipe failures, considering the spatial dependence and temporal variability of corrosion growth. An algorithm is developed integrating theories of reliability, corrosion science, random field, stochastic process, and copula within the framework of Monte Carlo simulation. The application of the developed algorithm is demonstrated using a real complex gas pipeline network. Also, the effect of discrete intervals, temporal variability and corrosion exposure area on probability of pipe failure is investigated. It is found that the failure probability of pipe segments varies spatially and the location of pipe segment with the largest probability of failure varies with time. It is also found that the largest probability of failure of pipe network is less sensitive to the discrete intervals although a fine discretization of the random field will increase the accuracy of simulation. It can be concluded that the proposed method can predict and visualize the location, time and magnitude of risk of a complex pipe network with reasonable accuracy.

Three-Dimensional CFD Modeling on the Thermal Characteristics of Buried Oil Pipeline Involving the Heat Transfer of Wax Layer

It is common to have a wax layer on the inner wall of waxy crude oil pipeline. However, the study of the wax layer on the heat transfer of buried pipeline systems is inadequate due to its instability of composition and properties; it may lead to the inaccurate prediction of the pipeline temperature field. Based on the finite element simulation technology, a three-dimensional heat transfer model of buried crude oil pipeline involving wax layer was proposed and solved. The thermal effect of the wax layer on pipeline system was analyzed quantitatively. Numerical results show that the average deviation of soil temperature near the pipeline reach 1.42 K when there is a 4 mm wax layer. Among different thermal conductivity models of heterogeneous materials, the EMT model plays best in predicting the conductivity of a waxy layer. By setting different working conditions, the influence mechanisms of several thermal influencing factors are discussed. The results show that the thermal influence range of heated pipe is positively associated with oil temperature and velocity. The core thermal response zone is about 12 m along the X-axis. Beyond 8 m depth from ground surface, the temperature fluctuation of soil is almost unaffected by the oil pipeline.

Innovative mitigation method for buried pipelines crossing faults

A new remediation technique is proposed to mitigate large deformations imposed on buried pipeline systems subject to permanent ground deformation. In this technique, low-density gravel (LDG) with high

Application of ground-penetrating radar method to detect underground pipes in PAIR BATAN utility area

Underground pipeline systems dominate today’s urban area landscape. This buried pipeline system will continuously develop along with the utility change. The planning for underground pipelines should be done to avoid mistakes in the pipeline path. Thus, mapping for the underground pipeline is necessary to obtain a database for any upcoming construction development. This research purpose is to detect underground pipelines around utility areas using the ground-penetrating radar (GPR) method. A frequency of 300 MHz was used to acquire GPR data from 6 lines, with a total length of 22.6m for each line and 0.5m for the line spacing. A sequence of processing stages of the GPR data was conducted using matGPR, a MATLAB-based program. Interpretable GPR profiles from each measurement line are obtained after adjusting signal position, removing DC, Dewow, mean filter, gaining, removing global background, and KL-filter. The results show an obvious amplitude reflection anomaly. Each line has similar detected underground pipes from its vertical axis, travel time, and horizontal distance. Clearly, all lines show an obvious contrast anomaly located at the 2.5 m horizontal distance. This most striking anomaly is interpreted as a water tunnel. In comparison, the other five parabolic-shaped anomalies were identified as underground pipes.

An efficient numerical approach for simulating soil-pipe interaction behaviour under cyclic loading

Understanding soil-pipe interaction during cyclic axial displacement is essential for the design and evaluation of buried pipeline systems. This study introduces an efficient and practical numerical approach using beam-spring-interface elements to simulate soil-pipe interaction behaviour. Numerical predictions of the evolution of shear and normal stress distributions around the pipe are validated against full-scale experimental results for steel and high-density polyethylene pipes buried in sandy soils. Three different backfill cover depths and soil densities ranging between loose and dense were considered to allow a rigorous comparison between the numerical predictions and the experimental results. The results show that the proposed approach provides a high-fidelity representation of the complex soil-pipe interaction behaviour at the interface zones, including stress cyclic degradation, hardening and softening, cyclic accumulative contraction and stabilization. This numerical framework provides accurate predictions for a fraction of the computational cost of a full three-dimensional finite element analysis.

Prediction and mitigation of AC interference on the pipeline system

Abstract The purpose of this paper is to predict and mitigate AC interference on buried pipeline systems due to transmission lines. Modeling and field verification of AC interference is done. The article also presents the issue of optimizing the mitigation measures. The paper uses the field data on soil resistivity, transmission line, and pipeline details to develop a model using current distribution electromagnetic interference grounding and soil structure analysis (CDEGS) software to predict the AC interference on the pipeline system. The model is validated with field measurements, and post-mitigation measures are considered. Mitigation measures are optimized to develop an economical mitigation plan. The case demonstrates the use of modeling techniques to predict and mitigate AC interference on pipelines. The field validation of modeling results helps improve the modeling results and plan optimized mitigation measures. The study requires providing comprehensive field data relevant to the pipeline system under consideration. The accuracy of the field data may have a bearing on the outcome of the study. The study enables designing and optimizing mitigation measures using modeling. Comparisons with field measurements help achieve desired pipeline system integrity against AC corrosion.

Analysis of the Pipelines Functional Safety on the Mining Areas

Buried pipeline systems, which transports water, sewage, oil or gas, perform the substantial role in urban areas. Sometimes their safe functioning is hampered because of damages caused in mining areas. In this article a characterization of the influence of mining activities on underground pipelines was presented. A description and classification of damages to pipelines with reference to mining influences were given of the various different pipelines systems and pipes materials. An illustrative example of damages to the stoneware sewage pipeline located on the mining area was presented. The effort of such pipe was carried out with using numerical methods (FEM). Model 2D represented stoneware pipe - soil system influenced by traffic load (SLW60) and the mining ground deformations (horizontal strains increasing from 0 to 9 mm/m). Model was built in ZSoil.PC program. The numerical analysis was performed as incremental and iterative. On the basis of the obtained results of numerical analysis (internal forces) the safety factors for various pipes classes with different bending strength were determined. Moreover, functional safety of the spigot-and-socked joints subjected mining impact was also assessed. During increasing of mining impact the insertion length at joints should provide free movement of spigots inside the socket, without losing the join tightness. It has been shown that the insertion length at analyzed stoneware pipes joints wasn’t appropriate which may result in damage of the spigot-and-socked joints during increasing the mining ground deformations.

Performance of buried pipes in moving slopes under axial loading – evaluation tools

Buried pipeline systems form a key part of effective and safe infrastructures for the transportation of natural resources such as natural gas and liquid. However, they may be constructed in areas prone to landslides where ground movement may exert excessive strains on the pipe sections causing rupture. This paper presents a methodology for estimating strains in a pipe under axial loading induced by ground movement. This methodology quantifies effects of soil displacement rate, total stress and pore pressure changes as well as time-independent (intrinsic) and time-dependent properties on the strains exerted on the pipe. These factors are not explicitly considered in current guidelines for constructing pipelines through areas prone to landslides. The procedure is based on a simplified analytical approach that can be readily implemented in practical design and analysis. A series of design charts are generated for performance evaluation of buried pipeline systems constructed in active slopes. They can be used to assess the frequency of necessary remediation such as in-situ stress relief procedure to protect the environment and maintain pipeline integrity and operation. For illustration, the proposed methodology is used in a case study to evaluate the potential risk of yielding in the pipe with the given soil displacement rates that occurred in the slope.

Transient thermal characteristics of the buried crude oil pipeline system during the reverse pipelining

Mathematical models and numerical approaches are applied to the thermal system coupling by the crude oil, pipeline and soil during the reverse pipelining of pipeline. On the basis of the above, five simulation cases are carried out to investigate the transient thermal characteristics of the thermal system. It can be concluded that the time evolution of crude oil temperature can be divided into three stages; among them, thermal performance in each stage is different due to the different dominating mechanisms. Based on the variation of the temperature profile along the pipeline, the crude oil pipeline can be divided into three regions. Among them, the temperature profile characteristics in each region are different due to the different dominating mechanisms. Further, the detailed evolution characteristics of thermal performance along the pipeline during the reverse pipelining are presented. So as to investigate the heat transfer mechanism of the thermal process, the temperature profile of soil around the pipeline is also presented. It can be concluded that the temperature of soil around the pipeline has the similar thermal characteristics as crude oil except the thermal hysteresis phenomena are presented. In addition, there exist two thermal influence regions around the pipeline during the reverse pipelining. One region is influenced by the reverse pipelining process. And another region is much larger and influenced by the crude oil pipeline. Furthermore, the effects of the outlet temperature and flow rate as well as the atmospheric temperature and pipeline diameter on the thermal characteristics of the pipeline system are also analyzed.

Short-Term Electromagnetic Interference on a Buried Gas Pipeline Caused by Critical Fault Events of a Wind Park: A Realistic Case Study

Short-term electromagnetic interference (EMI) pertains to the total result produced by the occurrence of intermittent, inductive, and conductive couplings on a buried pipeline system. For example, this type of EMI takes place when considering the fault conditions of a single ac power line, acting in the nearby vicinity of a pipeline system. In the context of this article, the effect of the short-term EMI is unfolded through a real case study. This case study involves a 20.7-MW wind park (WP) with extended underground power cable connections, which are laid nearby a high-pressure gas pipeline system. In particular, the impact of critical fault events, associated with the WP's power cables, on the pipeline system is comprehensively assessed. The assessment is achieved by the concurrent use of two powerful software tools that are respectively eligible for the accurate short-circuit analysis of the electrical circuit of the WP and for EMI evaluation on the pipeline. To this extent, the simulation results are thoroughly discussed and an effective mitigation solution is evidently presented.

Will a buried composite pipeline system fail at its joints under the effects of overburden soil, pipe operating pressurization, and traffic loads?

In real world applications, buried pipelines span across great lengths. It is inevitable that certain sections of a buried pipeline experience external loads in addition to top soil overburden, such as weights of aboveground buildings and traffic loads located directly above these sections. The present study investigated the effects of overburden soil, pipe internal pressurization, and traffic loads on fiber-reinforced plastic pipelines at various pipe sections with particular emphasis on pipe joints using finite element method. This study includes realistic modeling of traffic loading on service road running across a buried pipeline system, consisting of straight, bent, and joint sections. Our results also revealed that surcharge loading might not be a predominant factor in pipe failure or leakage issues as compared to the cyclic pipe internal pressurization. Moreover, it was also confirmed in our study that the pipe joint remained as the most critical region for pipe failure or leakage issues.

A Novel Experimental Technique to Investigate Soil–Pipeline Interaction under Axial Loading in Saturated and Unsaturated Sands

Abstract Comprehensive experimental and numerical models are required for reliable investigation of unsaturated soil-structure interaction problems. In this study, a reliable testing technique and a numerical modeling methodology were developed to study the performance of a buried pipeline system in sand subjected to relative soil movement in a direction parallel to its axis under both saturated and unsaturated conditions. A novel testing system was developed using a specially designed test box of 1.5-m length, 1.2-m width, and 1.1-m height. The system utilizes the hanging column technique to achieve different soil matric suction profiles. The experimental results on the tested sand suggest that the measured axial force exerted on a pipe in unsaturated sand is significantly higher compared with the saturated condition. The measured behavior of the prototype pipe was numerically modeled using the commercial software SIGMA/W extending the principles of saturated and unsaturated soil mechanics. The predicted axial force, following the suggested finite element analysis (FEA) methodology, is in good agreement with the measured axial force on the tested prototype pipe. Both the experimental technique and numerical method proposed in this article are useful for the practicing engineers in the rational design of pipelines in sandy soils, taking account of the influence of saturated and unsaturated conditions in sandy soils.

A Numerical Study of Axisymmetric Wave Propagation in Buried Fluid-Filled Pipes for Optimizing the Vibro-Acoustic Technique When Locating Gas Pipelines

Buried pipeline systems play a vital role in energy storage and transportation, especially for fluid energies like water and gas. The ability to locate buried pipes is of great importance since it is fundamental for leakage detection, pipeline maintenance, and pipeline repair. The vibro-acoustic locating method, as one of the most effective detection technologies, has been studied by many researchers. However, previous studies have mainly focused on vibro-acoustic propagation in buried water pipes. Limited research has been conducted on buried gas pipes. In this paper, the behavior of gas-dominated wave motion will be investigated and compared against water-dominated wave motion by adapting an established analytical model of axisymmetric wave motion in buried fluid-filled pipes. Furthermore, displacement profiles in spatial domain resulting from gas-dominated wave in buried gas pipeline systems will be analyzed, and the effects of pipe material, soil property, as well as mode wave type will be discussed in detail. An effective radiation coefficient (ERC) is proposed to measure the effective radiation ability of gas-dominated wave and water-dominated wave. It is observed that the gas-dominated wave in gas pipes cannot radiate into surrounded soil as effectively as water-dominated wave in water pipes because of the weak coupling between gas and pipe-soil. In this case, gas-dominated wave may not be the best choice as the target wave for locating buried gas pipes. Therefore, the soil displacements result from the shell-dominated wave are also investigated and compared with those from gas-dominated wave. The results show that for buried gas pipes, the soil displacements due to radiation of shell-dominated wave are stronger than gas-dominated wave, which differs from buried water pipe. Hence, an effectively exciting shell-dominated wave is beneficial for generating stronger vibration signals and obtaining the location information. The findings of this study provide theoretical insight for optimizing the current vibro-acoustic method when locating buried gas pipes.