Buried Pipelines Research Articles

Root cause analysis of cracking in buried X80 natural gas pipelines

In 2021, cracks formed in an onshore buried X80 natural gas pipeline with a diameter of 1219 mm. The present study investigated the cause of this failure through environmental and operational assessment, metallurgical evaluation, mechanical testing, material testing, stress analysis, and hydrogen embrittlement (HE) sensitivity testing. The results indicated that the failure was primarily attributable to hydrogen-induced cracking (HIC). The main factors contributing to this failure were identified as excessive material hardness and strength, which resulted in a high sensitivity to HE, even within the normal cathodic protection range. In addition, the mechanical damage that occurred during the construction process resulted in the destruction of the coating, causing stress concentration on the pipe body and further facilitating HIC.

Evaluation of Jacking Forces in Weathered Phyllite Based on In Situ Pressuremeter Testing and Deep Learning

Pipe jacking is a trenchless technology used to install buried pipelines, such as sewer lines in wastewater management systems. Existing mechanistic approaches based on geomaterial strength parameters (i.e., friction angle and apparent cohesion) can provide an estimation of the potential jacking forces during construction. However, extracting intact rock cores for strength characterisation is challenging when dealing with highly weathered ‘soft rocks’ which exhibit RQD values of zero. Such was the case for a pipe jacking drive traversing the highly weathered lithology underlying Kuching City, Malaysia. Furthermore, mechanistic approaches face limitations during construction when jacking forces are dependent on operation parameters, such as jacking speed and lubrication. To address these knowledge gaps, the primary objectives of this study are the development of rock strength parameters based on in situ pressuremeter testing for the purpose of estimating jacking forces. Furthermore, this study investigates the influence of various pipe jacking operation parameters, with a particular focus on their impact on jacking forces in weathered ‘soft rocks’. To achieve this, a novel deep learning model with an attention mechanism is introduced. The proposed methods of rock strength parameters derived from pressuremeter testing and the utilisation of deep learning will help to provide insights into the key factors affecting the development of jacking forces. This paper successfully shows the use of in situ pressuremeter testing in developing Mohr–Coulomb (MC) parameters directly from the site. In addition, the developed deep learning model with an attention mechanism successfully highlights the significance of pipe jacking operation parameters with an accuracy of 88% in predicting the jacking forces.

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.

Field Testing of a Mixed Potential IoT Sensor Platform for Methane Quantification

Emissions of CH4 from natural gas infrastructure must urgently be addressed to mitigate its effect on global climate. With hundreds of thousands of miles of pipeline in the US used to transport natural gas, current methods of surveying for leaks are inadequate. Mixed potential sensors are a low cost, field deployable technology for remote and continuous monitoring of natural gas infrastructure. We demonstrate for the first time a field trial of a mixed potential sensor device coupled with machine learning and internet-of-things platform at Colorado State University’s Methane Emissions Technology Evaluation Center (METEC). Emissions were detected from a simulated buried underground pipeline source. Sensor data was acquired and transmitted from the field test site to a remote cloud server. Quantification of concentration as a function of vertical distance is consistent with previously reported transport modelling efforts and experimental surveys of methane emissions by more sophisticated CH4 analyzers.

Study on response patterns and influencing factors of buried pipelines with corrosion defects under fault action

It is evident how corrosion flaws affect the tension and strain of pipelines that pass oblique-slip faults. The pipeline is very risky and is more likely to experience tensile and buckling damage when corrosion develops in the major deformation region of the pipeline. This will also significantly diminish the pipeline's failure slippage. This research uses a three-dimensional finite element modeling of trans-fault pipes to study the mechanical reaction and influencing factors of corroded pipelines under the action of oblique-slip faults. It is determined that the distribution of stress and strain as well as the pipeline's extension trend are changed when corrosion faults are present. The concentration of tensile and compressive strain along the corroded circular cross-section at the time of damage, followed by a gradual expansion through the entire corroded circumferential cross-section, and the pipeline's extrusion, folding, and bulging, are the manifestations of the influence of corrosion defects on the pipeline at damage. Tensile and compressive strains in the pipeline increase, failure slippage is reduced, and the pipeline experiences tensile damage and corrosion. The length of the pipeline corroded in the circumferential direction, the length of the corroded length in the direction of corrosion along the pipeline axis, and the corrosion depth increase all contribute to these outcomes. The location of corrosion defects has the greatest influence on the dynamics of the pipeline and is most dangerous in the large deformation section from -10 m to 10 m; the corrosion effect is very small when the corrosion is located on the right side of the fracture surface at 25 m. The risk of buckling damage is higher in this scenario, where the corrosion depth has the greatest effect. The conclusions of this paper can be used as a reference for the seismic and corrosion-resistant design of cross-fault pipelines.

Analysis of faulting destruction and water supply pipeline damage from the first mainshock of the February 6, 2023 Türkiye earthquake doublet

In 2023, two consecutive earthquakes exceeding a magnitude of 7 occurred in Türkiye, causing severe casualties and economic losses. The damage to critical urban infrastructure and building structures, including highways, railroads, and water supply pipelines, was particularly severe in areas where these structures intersected the seismogenic fault. Critical infrastructure projects that traverse active faults are susceptible to the influence of fault movement, pulse velocity, and ground motions. In this study, we used a unique approach to analyze the acceleration records obtained from the seismic station array (9 strong ground motion stations) located along the East Anatolian Fault (the seismogenic fault of the MW7.8 mainshock of the 2023 Türkiye earthquake doublet). The acceleration records were filtered and integrated to obtain the velocity and displacement time histories. We used the results of an on-site investigation, jointly conducted by China Earthquake Administration and Türkiye’s AFAD, to analyze the distribution of PGA, PGV, and PGD recorded by the strong motion array of the East Anatolian Fault. We found that the maximum horizontal PGA in this earthquake was 3.0 g, and the maximum co-seismic surface displacement caused by the East Anatolian Fault rupture was 6.50 m. As the fault rupture propagated southwest, the velocity pulse caused by the directional effect of the rupture increased gradually, with the maximum PGA reaching 162.3 cm/s. We also discussed the seismic safety of critical infrastructure projects traversing active faults, using two case studies of water supply pipelines in Türkiye that were damaged by earthquakes. We used a three-dimensional finite element model of the PE (polyethylene) water pipeline at the Islahiye State Hospital and fault displacement observations obtained through on-site investigation to analyze pipeline failure mechanisms. We further investigated the effect of the fault-crossing angle on seismic safety of a pipeline, based on our analysis and the failure performance of the large-diameter Thames Water pipeline during the 1999 Kocaeli earthquake. The seismic method of buried pipelines crossing the fault was summarized.

Thrust Restraint of Buried Pipelines Subjected to Internal Pressure, Thermal, and Earthquake Loads

Thrust Restraint of Buried Pipelines Subjected to Internal Pressure, Thermal, and Earthquake Loads

Investigation on wave-induced responses of heterogeneous seabed around a buried pipeline based on nonstationary random field model

The instability of the seabed poses a threat to the structural integrity and functionality of submarine pipelines. This numerical study investigates wave-induced responses in a heterogeneous seabed around a buried pipeline, considering spatial variability in soil properties through nonstationary random field models. Three scenarios of spatial variability for soil parameters changing with depth are simulated using both stationary and nonstationary random field models via the Karhunen-Loève expansion method. The discrete random fields are validated in terms of correlation structures and statistical characteristics. The stochastic finite element method, incorporating random fields and a poroelastic seabed model through a LiveLink code, is employed to examine probabilistic outcomes of dynamic soil responses and liquefaction zone distributions within a probabilistic framework. Contrastive analyses are conducted for seabed models with different random field scenarios, in addition to deterministic analyses. The results of the stochastic analysis show that the increasing trend of soil strength with depth has significant effects on the seabed responses and transient liquefaction characteristics around a pipeline.

Protection of Buried Pipelines from High-Speed Train Vibrations with Expanded Polystyrene Geofoam

High-speed railway (HSR) lines commonly operate over hundreds of kilometers, crossing several other large-scale infrastructures, such as highways, tunnels, bridges, and pipelines. This fact makes adjacent infrastructure more vulnerable to high-speed train (HST)-induced vibrations; thus, their potential distress should be carefully examined. The current study aims to assess the level of traffic-induced vibrations on the surface of buried pipelines vertically crossing under an HSR line. Firstly, the necessity to reduce high vibration levels is highlighted, utilizing a three-dimensional (3D) finite element model in conjunction with the moving load approach. Subsequently, an efficient mitigation measure is proposed to minimize these vibrations. For this purpose, a low-weight, high-performance geosynthetic fill material, i.e., expanded polystyrene (EPS) geofoam blocks, has been implemented between the HSR line and the buried pipeline to minimize the impact of vibrations. In this manner, HST-induced vibrations are reflected on EPS blocks, preventing them from reaching the pipeline surface. Based on this detailed parametric study, useful conclusions are drawn regarding the mechanical properties and geometry of the EPS protection layer.

Assessment of interference scope induced by stray current in the metro depot for the corrosion risk of buried metal pipeline

Assessment of interference scope induced by stray current in the metro depot for the corrosion risk of buried metal pipeline

Experimental Investigation of Pore Pressure on Sandy Seabed around Submarine Pipeline under Irregular Wave Loading.

The propagation of shallow-water waves may cause liquefaction of the seabed, thereby reducing its support capacity for pipelines and potentially leading to pipeline settlement or deformation. To ensure the stability of buried pipelines, it is crucial to consider the excess pore pressure induced by irregular waves thoroughly. This paper presents the findings of an experimental study on excess pore pressure caused by irregular waves on a sandy seabed. A series of two-dimensional wave flume experiments investigated the excess pore pressure generated by irregular waves. Based on the experimental results, this study examined the influences of irregular wave characteristics and pipeline proximity on excess pore pressure. Using test data, the signal analysis method was employed to categorize different modes of excess pore-water pressure growth into two types and explore the mechanism underlying pore pressure development under the influence of irregular waves.

Perimeter monitoring of urban buried pipeline threated by construction activities based on distributed fiber optic sensing and real-time object detection.

Urban construction activities seriously jeopardize the security of buried pipeline. Distributed optical fiber vibration monitoring is one of the most promising ways to prevent third-party threats, of which the biggest challenge is to quickly and accurately detect rare abnormal events from extremely large amounts of time-space raw data. By analogy with image recognition, the task here is similar to object detection if considering the time-space optical signals as the grayscale images and the abnormal events as the objects. Given this, what we believe to be a novel monitoring method is proposed, which consists of two Faster R-CNN models, a max pooling layer and a monitoring strategy. In the field tests, the 86-hour optical vibration signals for 5.25 km distance are recognized within 6.6 minutes with the recognition rate of 98.85% for construction activities, and only two false alarms are issued. The proposed method can reduce the recognition time by 99.59% compared to the CNN-based method.

Corrosion Behavior of X80 Steel in a Simulated Soil Solution Under Square-Wave Current Interference

The buried pipeline is disturbed by the dynamic direct current (DC) stray current with the subway as the main leakage source, which has the safety risk of accelerating corrosion, resulting in pipeline failure, which not only causes economic losses but also threatens personal safety. Therefore, it is necessary to study the corrosion behavior of pipeline steel under dynamic DC interference. The corrosion behavior of X80 steel under dynamic DC interference were studied by a mass loss test, alternating current impedance, circuit simulation, x-ray diffraction, and a Pourbaix diagram. Combined with the corrosion efficiency and Pourbaix diagram of the Fe-H2O system, the reversible process and reduction process mechanism in the Faraday process are proposed. The reason why the corrosion efficiency slows down in the process of non-Faraday is analyzed by the electric double-layer model of equivalent circuit calculation. In addition, based on the above corrosion process, the corresponding conceptual model of the corrosion mechanism is proposed. The experimental results show that with the asymmetry of positive and negative half-cycle interference duration and the increase of current density, the corrosion efficiency, and current corrosion efficiency of X80 steel decrease, and local corrosion intensifies. The length of the negative half-cycle interference affects the capacitive charge-discharge effect at the metal/solution interface and the reduction reaction process of corrosion products, resulting in corrosion slowing down and corrosion efficiency reduction. This is also an important reason for the reduction of corrosion mass loss observed in the experiment compared with steady-state DC.

Seismic fragility curves for buried steel gas pipelines with corrosion damage

Seismic fragility curves for buried steel gas pipelines with corrosion damage

Time–frequency dual-domain electromagnetic detection technology for buried pipelines

ABSTRACT Monitoring and detecting buried pipelines under concrete pavement are often complex and difficult tasks. The time–frequency electromagnetic technology, with the fast information acquisition and strong anti-interference ability, is first applied in the buried pipeline inspection. The purpose is to verify if this method can monitor and detect the pipelines status change effectively, even if covered by concrete pavement. Three representative scenarios (normal, coating-damaged and leaking) and two types of pavement (plain concrete and reinforced concrete) are created and applied in the simulations with the finite element method. The simulated results are processed and analysed with the proposed method. In the frequency domain, the maximum change of the electric and magnetic field signals for the coating-damaged scenario from the normal one are 0.4% and 9.9% respectively, and 97.7% and 157.7% for the leaking scenario. In the time domain, the shifts of the electric and magnetic field signal peak are 6.2 μs and 6.5 μs respectively when the coating damage occurs, and 11.4 μs and 13.1 μs when leakage appears. The results indicate that the above technology is valid for buried pipelines. Moreover, it can be used to locate and identify the abnormalities and types of concrete pavement can be differentiated.

Research on numerical modeling of ac interference from high-speed railway to nearby buried pipeline

The large-scale construction of high-speed railways and buried pipelines has led to the parallel or intersection of these lines over long distances in some areas, resulting in dynamic AC interference to buried pipelines. In this paper, the modeling method of the AC interference from high-speed railway employing auto-transformer (AT) power supply mode to the buried pipeline was investigated, and the accuracy of the modeling method was verified by the simulation calculation of the actual field case and the comparison with the field data. Through modeling and calculation, the influence of train running position, rail to ground transition resistance and crossing angle on AC interference of high-speed railway is discussed. Based on the above research, it is analyzed that the dynamic AC interference is caused by the change of current distribution and the train load current. The main mechanism of AC interference caused by high-speed railway operation on nearby pipelines is inductive coupling. Especially when the rail to ground transition resistance is less than 50 Ω km, due to the unbalanced distribution of power supply circuit current, the peak AC interference voltage appears on pipeline where the train is located.

Seismic Assessment Formula for a Buried Pipeline With Local Wall Thinning

Abstract The structural strength of buried pipeline may be reduced by local wall thinning owing to corrosion in long-term operations. In seismic active area, it is necessary to ensure the integrity of buried pipeline with wall thinning against seismic motion. This study proposed a seismic assessment formula for a pipe with wall thinning subjected to cyclic axial loading assuming seismic motion. Cyclic axial loading experiments using pipes with wall thinning and finite element analysis (FEA) were conducted to study the failure behavior. The pipe with wall thinning deformed starting from the wall-thinning part, and finally plastic collapse due to elephant foot buckling or leakage at the wall thinning due to low-cycle fatigue occurred in several to ten and several cycles. Based on the deformation mechanism at wall thinning, a seismic assessment formula was proposed. The proposed formula can easily evaluate the seismic performance of the pipe with wall thinning against design seismic motion. The formula was validated by the results of experiments and FEA. In addition, based on the proposed formula, the assessment curves for an allowable wall-thinning size against design seismic motion were illustrated. The formula can be used to formulate standards and assess the safety of pipes with wall thinning that are subjected to seismic motion.

Analysis of external corrosion protection performance on buried gas pipeline using CIPS and DCVG methods

The present work investigates the effectiveness of external corrosion protection using Close Interval Potential Survey (CIPS) and Direct Current Voltage Gradient (DCVG) on a buried gas pipeline. These surveys were performed on 12” gas pipeline in East Kalimantan. Coating and cathodic protection were the primary corrosion protection on these pipelines. Soil resistivity measurement was conducted every km along the pipeline to obtain the resistivity profile combined with the pH profile. CIPS showed that the Cathodic Protection system protects 79.21 % of the pipeline area. There is no sign of telluric or stray current effect from the result of CIPS. DCVG showed 159 defects that can be divided into three different clusters. There is 6-point coating defects that should be repaired immediately due to the characteristics and category of the defect. The integrated data analysis of CIPS and DCVG showed a correlation which dips pattern on CIPS graph indicating coating defect on DCVG surveyed. Soil resistivity measurement showed that the soil resistivity profile is negligible from KP 0 – 5, while KP 5 – 14 is mildly corrosive. pH measurement showed the acidity level or the soil along the pipeline were neutral. Cathodic protection level could be improved with the increase of cathodic protection current and coating repair along the area with low-level protection.

Study of the uplift of buried pipelines in liquefied soils based on the earthquake record

The uplift of a straight buried pipeline with a middle part located in liquefied soil was considered in the article. The process of uplift of the pipeline under the action of Archimedes’ force in the liquefied soil zone and longitudinal compressive force arising due to the temperature difference of the transported product and its internal pressure and also based on the Gazli earthquake record are investigated. To solve the problem the finite element method is used with the incremental refinement of the solution by the method of successive approximations. In the deformation process takes into account the separation of the pipeline from the base and the decrease of soil pressure along the length of the pipeline during the uplift process, taking into account the increment of displacement from the previous step. The results of solving the problem are presented in the form of graphs and their analysis for specific numerical parameters of the pipeline and its interaction with the surrounding soil.

An investigation of the impact of liquefaction-induced building settlement on buried pipelines

An investigation of the impact of liquefaction-induced building settlement on buried pipelines