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Upon leakage in underground gas pipelines, the interaction between soil particles and gas will produce acoustic events exhibiting varied frequencies, amplitudes, and energy characteristics. In order to obtain the acoustic response of gas pipeline leaks that are buried, experiments were conducted using a two-dimensional visual leak testing facility. Employing time-domain parameter analysis, fast Fourier transform (FFT), and wavelet packet analysis (WPT), this study meticulously investigated the impact of gas pressure and soil moisture on the time-frequency characteristics of the acoustic waves throughout the leakage process. The results show that: (1) the amplitude, dominant frequency, and energy of acoustic waves closely relate to the deformation and disturbance of soil morphology, (2) the amplitude of acoustic waves increases and decreases exponentially with the increase of gas pressure and soil moisture content, respectively, (3) the main frequency response of acoustic waves during the erosion process predominantly lies within the 0 to 1 kHz range, exhibiting an "N-shaped" cyclical variation, and it tends to decrease with the increase in gas pressure and increase with the rise in soil moisture content, (4) as the leakage process continues, the energy ratio of 0–156.25 Hz increases continuously, the maximum is 45.24%, and the frequency bands of 0–156.25 Hz and 156.25–312.5 Hz demonstrate a strong responsive pattern to variations in soil moisture content and gas pressure, respectively. Therefore, these two can be utilized as the characteristic frequency bands to represent the effects of moisture content and gas pressure, and (5) the leakage acoustic sources primarily originate from pipe wall vibrations, gas impact on soil particles, and friction within the soil particle medium, with the latter two types of vibrations generating more propagative acoustic waves. The research results are of great significance to the prediction of soil structure damage and the acoustic monitoring of gas leakage. [ABSTRACT FROM AUTHOR]

A subway station's operation is susceptible to accidents when there is a high-pressure gas pipeline overlaying it, and analyzing the correlations between the safety influencing factors (SIFs) in this operating situation can provide paths to reduce safety accidents. Thus, this paper investigated the coupling correlations between the SIFs. We firstly identified the SIFs during subway station operation under a high-pressure pipeline (SSOUHP) based on a literature review and discussion with experts. Then, the analytic hierarchy process (AHP) and coupling degree analysis (CDA) were combined to assess the coupling correlations between the SIFs, and Y subway station was selected to test the proposed hybrid coupling analysis approach. Research results show that (a) 23 second-level SIFs were identified and these SIFs can be summed up into five first-level SIFs, namely, human-related SIFs, pipeline-related SIFs, station-related SIFs, environment-related SIFs, and management-related SIFs; (b) the proposed hybrid approach can be used to evaluate the coupling correlations between SIFs; (c) of the coupling situations during Y subway station's operation, the internal coupling correlations among environment-related SIFs, the coupling correlations between pipe-related SIFs and environment-related SIFs, and the coupling correlations among human-related SIFs, pipe-related SIFs, and environment-related SIFs are all greater than 1, and the coordination degree is 0.778, 0.781, and 0.783, respectively, which is a high security risk; (d) the overall coupling degree among all SIFs during Y subway station's operation is 0.995 and the coordination degree is 0.809, which is a low safety risk. The research can enrich knowledge in the safety evaluation area, and provide a reference for onsite safety management. The results are basically consistent with the conclusion of the enterprise report, which verifies the scientificity and validity of the evaluation method. [ABSTRACT FROM AUTHOR]

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The article discusses the problems of the occurrence of unaccounted-for-gas (UAG) during the operation of the gas pipelines. The paper proposes a simple and effective algorithm for the classification of UAG, as well as for the search for the origin of the cause of UAG, which is based on fuzzy logic methods. The article deals with the implementation of a fuzzy system of control and management over the balance of gas volume and the implementation of the algorithm for finding the causes of UAG. The article shows the ways of implementing this algorithm using the example of programming languages of the IEC 61131 standard, and also discusses issues related to dispatching control of gas pipelines, and the role of such systems in controlling the balance of gas volumes. [ABSTRACT FROM AUTHOR]

X70 steel gas transmission pipeline has a large market share and a long operation time, and the problem of pipeline integrity, represented by corrosion, is now becoming increasingly prominent. Under actual working conditions, the corrosion of gas transmission pipelines is complex. In order to study the corrosion characteristics of X70 steel gas transmission pipeline under different soil environments, help pipeline integrity management and ensure operational safety, the raw gas pipeline of an LNG project was used as the object of study, and firsthand data were obtained with the help of OLYMPUS 38DL PLUS thickness gauge with the help of special hanging sheet deployment mode on site. The data were brought into a suitable gray prediction model to detect trends in condition data and to predict future corrosion levels. Finally, a sampling inspection plan with the best combination of time and cost was obtained. The results are as follows: 1. The trend in the corrosion data exhibits a typical single-peak sequence, coupled with the "S"-shaped growth characteristics of biological growth, which ultimately reveals that SRB is the main cause of pipeline corrosion; 2. Among the uncoated original state hangings, the greatest corrosion depths can be observed in 2018 and 2019, with the greatest change in corrosion depth in 2020. 3. The best Verhulst model is with cumulative corrosion depths of 249.00 μm and 250.61 μm for the next 2 years. The next step is to perform a full inspection of 50 uncoated original hanging pieces, while performing sampling inspection of 15 three-layer PE parcel pieces will improve the integrity of the pipeline. [ABSTRACT FROM AUTHOR]

Location class is an essential factor in the gas pipeline project because it considers factors such as population density and the number of buildings along the gas pipeline route. As these parameters change, the pipeline operator needs to review the location class, also requiring a possible assessment of changes in allowable pipeline operating pressure. Brazilian regulations related to the safety of pipeline processes are defined in the Onshore Pipeline Technical Regulation and this document indicates the application of the requirements of the ASME B31.8 standard for changing the location class. Although there are preventive and mitigating measures in the ASME B31.8 standard, they are seen as overly conservative. Other international standards have different concepts, with evaluation criteria based on risk analysis. The issue has also been a challenge for other countries, which are reviewing their regulations and developing guidelines for gas pipeline operators. The main objective of this study is to carry out a survey of international practices related to changing the location class of gas pipelines and to propose a criterion based on the best international practices based on risk management, allowing a more comprehensive view of this subject. [ABSTRACT FROM AUTHOR]

Experimental setups using steel and transparent glass pipes, along with equally spaced steel stamped and transparent plastic tees, were designed for testing. The experimental results provided insights into the influence of flow directions, pig length, material properties, and air consumption on the dynamics and strength of the pigs within the tees. Furthermore, the study identified the causes of temporary halting, jamming, and the mechanisms of damage to cylindrical pigs made of hyperelastic materials within pipeline tees.

[Objective] High-frequency acoustic energy generated by gas passing through decompression devices induces high-order modes of the pipeline wall, leading to acoustic-induced vibrations of the pipeline structure. These vibrations can potentially trigger fatigue failures at discontinuous, such as welded supports, tees, and areas of pipeline corrosion defects, over a short period. [Methods] Initially, the infuence of sound source strength was quantified by calculating the noise spectrum and converting the sound power levels into sound pressure levels.A finite element model was created to simulate acoustic-induced vibrations in a gas pipeline featuring corrosion defects. Acoustic pressure was applied to the pipeline wall within the model to investigate the impact of corrosion defect dimensions on acoustic-induced vibrations,i.e. length, width, and depth. Subsequently, the obtained results were compared against the evaluation outcomes derived from the Energy Institute(EI) guidelines. [Results] Under varying dimensionless lengths of corrosion defects, the gas pipeline exhibited stress responses characterized by hump-like fuctuations. Specifically, the stress level initially increased and then decreased corresponding to increases in dimensionless defect length. However, the stress concentration weakened with increasing dimensionless defect lengths. As the defect width increased, the gas pipeline showed a uniform stress distribution. Additionally, the pipeline stress fuctuated in a saddle shape with increases in dimensionless defect depth. Specifically, the gas pipeline experienced initial decreases followed by rises in the stress level. [Conclusion] This study reveals the substantial impact of corrosion defects on gas pipeline's stress responses, highlighting the most noticeable impact from the length of corrosion defects. Furthermore, corrosion defects with dimensionless depths over 0.6 lead to significant increases in their infuence on the stress and vibration modes of gas pipelines. Consequently, future research should focus on investigating the impact of corrosion defect depths on acoustic-induced vibrations. The quantitative analysis outcomes of acoustic-induced vibration responses in gas pipelines with corrosion defects not only offer theoretical support for mitigating strong vibrations of gas pipelines but also serve as a reference basis for gas pipelines across design, construction, operation, and maintenance stages.

Long-distance gas pipelines in service inevitably are exposed to harsh conditions such as extreme temperature. It is also recognized that corrosion is one of most influential factors on the structural reliability and safety of pipelines, even coated pipelines. Therefore, there is an important need to investigate the temperature effect on the failure behaviors of gas pipelines with corrosion. In this study, a thermomechanically nonlinear finite-element model of a corroded gas pipeline with a polyethylene protective layer was established, in which a large diameter is considered for the long-distance gas pipeline. Thermal stresses obtained from cases with and without the protective layer were compared. Based on the stress-based failure criterion, the failure pressure values of corroded pipeline at different temperatures were obtained, and the deformation and strain of the corroded pipeline were evaluated. The random forest algorithm was adopted to analyze the parametric sensitivity of failure pressure. Taking temperature into account, an estimation model for predicting the failure pressure of corroded pipelines is proposed using the nonlinear least-squares method, which could be useful for performing a preliminary assessment of the failure pressure of long-distance gas pipelines in practice. [ABSTRACT FROM AUTHOR]

Thermomechanical steels are widely used in oil and gas pipelines due to their high toughness and high resitance against crak growth. A large part of the steel pipelines used in the oil and gas industry in Iran is made of API X65 steel. The fluctuations of internal gas pressure in steel pipes can cause fatigue failure and lead to gas leakage and explosion. So, the control of damage initiation and structural integrity of gas pipelines is of great importance. In this study, the S-N curve and the fatigue strength of the base metal of the API X65 steel were estimated by performing fatigue tests. For this purpose, 24 and 25 test specimens along the seam weld in the coil transverse direction, and perpendicular to the seam weld along the coil rolling direction were prepared according to ISO 1143 standard, respectively. All test samples were cut from an spirally welded pipe with 1219mm outside diameter and 14.3mm wall thickness and were tested on a completely reverse rotating-bending fatigue machine. Statistical analysis of the results was performed by considering the normal logarithmic distribution. The mean curve, characteristic curve, and confidence interval of the results were obtained both in the finite fatigue life range and in the fatigue resistance. The mean endurance limit of the base metal perpendicular to and parallel to the seam seam were 305 and 291 MPa, respectively which were in the range of 0.4 to 0.6 of material tensile strength and above the seam weld endurance limit (258 MPa). [ABSTRACT FROM AUTHOR]

Measurements of residual stresses inherited by pipes during the pipe manufacturing process were carried out, and the relationship of SCC with these stresses in the pipe metal was studied. The obtained correlations demonstrate the possibility of optimizing the pipe manufacturing process to reduce their susceptibility to stress corrosion. [ABSTRACT FROM AUTHOR]

In order to scientifically evaluate the impact of gas pipeline disasters in karst area, two typical consequence modes of jet fire and vapor cloud explosion were determined based on pipeline failure characteristics, and the hazard criteria of thermal radiation and shock wave overpressure applicable to gas pipeline disasters in karst area were selected. The evaluation model system for the severity of gas pipeline disaster consequences in karst areas was proposed from the four dimensions of hazard area, casualties, economic loss and environmental damage, and the software for analysis of gas pipeline disaster consequences in karst area was developed based on Visual Studio platform. Based on the actual engineering case in karst area, combined with the regional economic and social development, karst natural geology and gas pipeline engineering characteristics, the impact scope of disaster consequences was simulated and analyzed based on PHAST software. Targeted disaster risk control measures were proposed for personnel and objects in the affected area based on hazard criteria. By introducing relevant standards and regulations issued by the government, industry and enterprises, the impact degree of disaster consequences were quantified. The results show that the proposed PHAST-Visual Studio integration method can make up for the subjectivity problems in the evaluation process of previous studies, bring social science ideas into the engineering risk assessment research, and improve the efficiency of disaster consequence analysis through computer software programming, which is helpful to significantly reduce the level of disaster consequences of gas pipelines in karst area. [ABSTRACT FROM AUTHOR]

The most rapid and efficient method to transport natural gas from its source to its destination is through a pipeline network. The optimal functioning of control stations for natural gas pipelines depends on the use of electrical devices, including data loggers, communication devices, control systems, surveillance equipment, and more. Ensuring a reliable and consistent power supply proves to be challenging due to the remote locations of these control stations. This research article presents a case study detailing the design and dynamic modeling of a hybrid power system (HPS) to address the specific energy needs of a particular natural gas pipeline control station. The HOMER Pro 3.17.1 software is used to design an optimal HPS for the specified location. The designed system combines a photovoltaic (PV) system with natural gas generators as a backup to ensure a reliable and consistent power supply for the control station. Furthermore, it provides significant cost savings, reducing the cost of energy (COE) by USD 0.148 and the annual operating costs by USD 87,321, all while integrating a renewable energy fraction of 79.2%. Dynamic modeling of the designed system is performed in MATLAB/Simulink R2022a to analyze the system's response, including its power quality, harmonics, voltage transients, load impact, etc. The experimental results are validated using hardware in the loop (HIL) and OPAL-RT Technologies' real-time OP5707XG simulator. [ABSTRACT FROM AUTHOR]

This article examines the prospects for increased Turkish-American relations in the Caspian region, namely, joint areas of activity for the development and consolidation of cooperation between both states. Utilizing a historical-comparative method, we comprehensively study Turkish-American relations in this region from a historical viewpoint and predict the further development of this cooperation in the future. The key characteristics and features of Turkish-American relations in the Caspian region from 1991 to 2022 are identified, as are the causes of crises in relations between the two countries against the background of a change in US policy. Finally, we emphasize the importance of further strengthening strategic cooperation between Turkey and the US in the Caspian region. [ABSTRACT FROM AUTHOR]

We develop a weakly intrusive framework to simulate the propagation of uncertainty in solutions of generic hyperbolic partial differential equation systems on graph-connected domains with nodal coupling and boundary conditions. The method is based on the Stochastic Finite Volume (SFV) approach, and can be applied for uncertainty quantification (UQ) of the dynamical state of fluid flow over actuated transport networks. The numerical scheme has specific advantages for modeling intertemporal uncertainty in time-varying boundary parameters, which cannot be characterized by strict upper and lower (interval) bounds. We describe the scheme for a single pipe, and then formulate the controlled junction Riemann problem (JRP) that enables the extension to general network structures. We demonstrate the method's capabilities and performance characteristics using a standard benchmark test network. • Formulation of a stochastic hyperbolic PDE as a high-dimensional parametric PDE. • Novel SFV method for quantification of intertemporal uncertainty in systems of conservation laws posed on graphs. • Formulation of the stochastic junction Riemann problem to compute numerical fluxes at the nodes of the graph. • Application of the SFV method to a real-world problem of stochastic gas flows on networks. • Convergence analysis for the statistical moments of the solution. [ABSTRACT FROM AUTHOR]

A subway station’s operation is susceptible to accidents when there is a high-pressure gas pipeline overlaying it, and analyzing the correlations between the safety influencing factors (SIFs) in this operating situation can provide paths to reduce safety accidents. Thus, this paper investigated the coupling correlations between the SIFs. We firstly identified the SIFs during subway station operation under a high-pressure pipeline (SSOUHP) based on a literature review and discussion with experts. Then, the analytic hierarchy process (AHP) and coupling degree analysis (CDA) were combined to assess the coupling correlations between the SIFs, and Y subway station was selected to test the proposed hybrid coupling analysis approach. Research results show that (a) 23 second-level SIFs were identified and these SIFs can be summed up into five first-level SIFs, namely, human-related SIFs, pipeline-related SIFs, station-related SIFs, environment-related SIFs, and management-related SIFs; (b) the proposed hybrid approach can be used to evaluate the coupling correlations between SIFs; (c) of the coupling situations during Y subway station’s operation, the internal coupling correlations among environment-related SIFs, the coupling correlations between pipe-related SIFs and environment-related SIFs, and the coupling correlations among human-related SIFs, pipe-related SIFs, and environment-related SIFs are all greater than 1, and the coordination degree is 0.778, 0.781, and 0.783, respectively, which is a high security risk; (d) the overall coupling degree among all SIFs during Y subway station’s operation is 0.995 and the coordination degree is 0.809, which is a low safety risk. The research can enrich knowledge in the safety evaluation area, and provide a reference for onsite safety management. The results are basically consistent with the conclusion of the enterprise report, which verifies the scientificity and validity of the evaluation method.

[Objective] Surface gas transmission pipelines suffer serious internal corrosion. To ensure the service safety of pipelines, it is necessary to accurately predict their internal corrosion rate. [Methods] The main control factors that affect corrosion were screened based on the Rough Set(RS) theory, and the reconstructed data set was used as the input while the corrosion rate was used as the output to train the Kernel Based Extreme Learning Machine(KELM) model. Additionally, the Improved Seagull Optimization Algorithm(ISOA) was used to optimize the model hyperparameters, and a prediction method of internal corrosion rate based on the RS-ISOA-KELM model was proposed. The prediction precision was compared with that of other combination models, and the long-term prediction effect and model universality were analyzed. [Results] The convergence analysis for the ISOA algorithm was conducted on five benchmark functions including Sphere, Schaffer, Rosenbrock, Rastrigin, and Griewank, and it was found that the ISOA algorithm had better performance in terms of solution precision and calculation stability. The model was verified using actual operating data from a gas field block. For the selected data set, the temperature, CO2 partial pressure, H2S partial pressure, flow rate, Cl-content, moisture content, and corrosion inhibitor residual concentration were crucial factors that affect internal corrosion. Among them, H2S partial pressure, flow rate, and corrosion inhibitor residual concentration had the largest weight. The RS-ISOA-KELM model was used to predict the corrosion rate, and its average relative error was 1.498%, root mean square error was 0.002 1 mm/a, and coefficient of determination was 0.999 3, which were all better than other common comparison models. [Conclusion] The combined model has strong generalization performance and high prediction precision. By expanding and updating the original database,it can predict the medium-and long-term corrosion rate of pipelines.With different corrosion parameters,data sizes,and training test ratios,the model still maintains a good prediction effect.

Aiming at the current challenges of enormous scale, complex structure, difficult control and frequent accidents of city gas high-pressure pipeline network, there are still three aspects of difficulties in the risk monitoring and control of China’s city gas high-pressure pipeline network, namely, rough data, shallow assessment, and lack of power. This paper proposes an intelligent management system for gas pipelines based on C/S model and J2EE enterprise-level framework, in which the failure warning models of gas leakage, Gaussian plume diffusion, and fire and explosion are established. And the Kalman filter algorithm improved by DS evidence theory is used for intelligent fusion of Multi-source data, analyzing and screening the unified adequate information on data types, extracting state characteristics, classifying warning levels, and developing an integrated and visualized pipeline remote diagnosis and warning platform. In the simulation of the intelligent management system of gas pipeline, when the wind speed is 1.5m/s in winter, the ground surface is a safe area within 12.15m of the gas pipeline. When the maximum wind speed is 10m/s, the upper limit distance of the gas leading to fire and explosion is only 2.43m, and the hazardous range of the gas pipeline jet fire is within 12.69m. Relying on the gas high-pressure pipeline network in L city for practical experiments and applications, it provides technical support and decision-making basis for the construction of intelligent pipeline network, comprehensively improves the risk control capability of city gas high-pressure pipeline network, and has reference significance for the risk control of national city gas high-pressure pipeline network.

The most rapid and efficient method to transport natural gas from its source to its destination is through a pipeline network. The optimal functioning of control stations for natural gas pipelines depends on the use of electrical devices, including data loggers, communication devices, control systems, surveillance equipment, and more. Ensuring a reliable and consistent power supply proves to be challenging due to the remote locations of these control stations. This research article presents a case study detailing the design and dynamic modeling of a hybrid power system (HPS) to address the specific energy needs of a particular natural gas pipeline control station. The HOMER Pro 3.17.1 software is used to design an optimal HPS for the specified location. The designed system combines a photovoltaic (PV) system with natural gas generators as a backup to ensure a reliable and consistent power supply for the control station. Furthermore, it provides significant cost savings, reducing the cost of energy (COE) by USD 0.148 and the annual operating costs by USD 87,321, all while integrating a renewable energy fraction of 79.2%. Dynamic modeling of the designed system is performed in MATLAB/Simulink R2022a to analyze the system’s response, including its power quality, harmonics, voltage transients, load impact, etc. The experimental results are validated using hardware in the loop (HIL) and OPAL-RT Technologies’ real-time OP5707XG simulator.

• Model-based method to assess pipe dent due to external interference by excavators. • Numerical scheme for calculating excavator maximum force and kinetic energy. • Excavator-pipe interaction model suitable for static and dynamic contacts. • Dent charts for selecting the excavator to be employed to avoid damaging the pipe. • Preventive action that involve limiting the excavator workspace for risk mitigation. Despite the presence of numerous safety precautions, the primary cause of damage to underground pipes is often attributed to external interference from excavators during their operations. To address this issue, this paper introduces a model-based approach that incorporates both static and dynamic contact in assessing the damage caused by excavators on pipes. The objective of this method is to offer a practical tool that can assist in determining the appropriate excavator size for buried gas pipes. By identifying the maximum safe excavator size, the aim is to minimize the potential risks of mechanical damage to the pipe, to prevent hazards for operators and to protect the integrity of the pipeline. For this purpose, a comprehensive excavator model is constructed. Following this, a suitable damage model for the pipe is selected and the interaction between the bucket tooth and the pipe is modelled. To enhance accuracy, the excavator and pipe are interconnected through the solution of damped contact equations, which take into account the stiffnesses of both the pipe and excavator, as well as the damping effect resulting from pipe deformation. Results provide valuable insight into the potential damage caused to the pipe, which can be attributed to either static or dynamic contacts, depending on which excavator is being used. Failure is addressed by plastic dent, that can be avoided by selecting the most suitable excavator size. Moreover, the analysis of dent depth caused by various excavators on different pipes for gas transmission, opens to the possibility of mitigating the risk of failures by limiting the excavator workspace. [ABSTRACT FROM AUTHOR]

• Leak detection methods based on pressure waves in gas pipelines are summarized. • The principles of different infield and outfield acoustic methods are grouped. • Stimulus response and acoustic reflection methods are summarized. • Machine learning is widely applied to pressure wave leakage detection. • Localization range, capability and error of the different methods are surveyed. The integrity of gas pipelines is important for fuel delivery, but pipeline leaks frequently occur for a variety of reasons. As a result, pipeline leak detection for gas pipelines is now an important issue of concern. Currently, there is an absence of review regarding the development of pressure wave-based method for detecting leaks in gas pipelines. Therefore, this paper surveys the published research articles in related fields in recent decades. The principles and applications of leak detection based on pressure wave are categorized. Different signal analysis and machine learning techniques utilized in the detection of leakage are surveyed. In addition, the localization range, localization capability (size of the leak), and localization error of different methods are investigated in detail. The advantages, limitations, and performance of different detection methods are discussed, and potential future directions are proposed. This will be beneficial to experts and engineers working in this area of expertise. [ABSTRACT FROM AUTHOR]

Explosion is one of the primary factors influencing the safety of gas pipelines. To investigate the bucking deformation and failure mechanism of gas pipeline in an explosion shock wave environment, a study was conducted on the stress, deformation, center deflection and energy variation of the pipeline. The analysis was grounded in elastic-plastic theory and utilized the finite element method. Additionally, the study delved into the impact of explosion distance, diameter-to thickness ratio, and charge quantity on the dynamic behavior of pipeline. The research results revealed that high-stress and plastic strain regions emerge on the pipeline during initial loading, causing compression on the outer wall and stretching on the inner wall. As the loading process progresses, the zero circumferential stress surface shifts towards the outer wall, ultimately leading to cracks and pipeline failure. Furthermore, the study observed that pipeline deformation exhibits a direct correlation with charge quantity and an inverse correlation with the diameter-to-thickness ratio. As the explosion distance increases, the center deflection of the pipeline abruptly decreases and then stabilizes. Concurrently, the influence of the diameter-to-thickness ratio and charge quantity on pipeline deformation diminishes. The difference of diameter-thickness ratio gives rise to various failure mechanisms and modes. Finally, the engineering prediction model of the maximum deformation of pipeline is obtained. The study offers valuable insights and references for pipeline design, safety assessments practices. • The stress, deformation of gas pipeline in explosion shock wave environment were studied based on finite element method. • The explosion distance, diameter thickness ratio and charge quantity on the dynamic behavior of pipeline were discussed. • The study provides basis and reference for pipeline laying, safety assessment and maintenance. [ABSTRACT FROM AUTHOR]

The whole process of pipeline–soil interactions between a landslide and a gas pipeline was simulated using the strength reduction method. The main purpose is to investigate how pipeline internal pressure, landslide displacement, crack depth ratio (the ratio of crack depth to wall thickness), crack aspect ratio (the ratio of crack depth to crack half-length), and reinforcement with anti-slide piles influence the J-integral of a circumferential crack in the pipeline under landslide impact. The simulation showed that increases in the landslide displacement, crack depth ratio, and pipeline internal pressure led to an increase in the maximum value of the J-integral at the crack leading edge. An increase in the crack aspect ratio reduced the maximum value of the J-integral. In addition, in the process in which the crack shape changed from semi-elliptical to semicircular, there was a critical crack aspect ratio at which the J-integral at the deepest point of the crack was equal to the J-integral at a point on the surface. The study also found that an increase in the number of anti-slide piles affected the location and distribution of the zone of maximum slippage and effectively reduced the maximum von mises stress and the J-integral at the crack tip. However, when the number and cross-sectional size of anti-slide piles exceed a certain threshold, further increasing or enlarging them barely affects the J-integral. • The strength reduction method simulates the full process of pipe-soil interaction. • The effect of crack depth ratio and crack aspect ratio on J integral is analyzed. • Beyond a threshold, adding or enlarging anti-slide piles barely affects J integral. [ABSTRACT FROM AUTHOR]

To determine the ultimate load of buried gas pipelines under different working conditions under landslide action and provide a quick decision-making tool for landslide risk management, a pipe–soil coupling model is established based on smoothed particle hydrodynamics and the finite element method. The double elastic slope criterion and fault tree analysis method are used to perform limit and failure analyses on the pipelines. The research results indicate that pipeline stress and strain during oblique crossing are positively correlated with the crossing angle. The upper section of the pipeline exhibits tensile bending, whereas the lower section exhibits compressive bending. Local stress is concentrated at the elbows at both ends of the pipeline during longitudinal crossing, which is similar to the force applied during oblique crossing. The ultimate pipeline bearing capacity is negatively correlated with its burial depth and pressure. There is a positive correlation between the distance from the pipeline to the rear edge of the landslide and the width of the landslide. There is also an optimal value for the moisture content of landslides. Fault tree analysis reveals that, to prevent pipeline failure under the action of landslides, priority should be given to determining a reasonable pipeline laying method, reducing the moisture content of the sliding body, controlling the thickness and width of the landslide body, controlling the displacement and inclination angle of the sliding body, timely eliminating soil and soil pressure, and avoiding the failure of drainage systems and support facilities. Based on the research results, we propose a method that can preliminarily identify the main control factors affecting pipeline integrity. This method provides a reference for studying and developing engineering mitigation measures, identification procedures, and operation guidance documents for geological disaster risks for pipelines crossing landslide sections. [ABSTRACT FROM AUTHOR]

The recognition of pipeline features contributes to its safe management by preventing severe consequences such as leakage resulting from bending deformation and denting under external pressure. However, extracting features of such a facility is complex and challenging when machine learning techniques are applied to feature recognition. Hence, this paper proposes a feature recognition technique for gas pipelines based on Gramian Time Frequency Enhancement Net (GTFE-Net), Bi-directional Long Short-Term Memory (BiLSTM) and attention mechanism (AM), namely GTFE-Net-BiLSTM-AM. Specifically, GTFE-Net is applied to enhance the time-frequency input bending strain signal, which is subsequently incorporated with the BiLSTM model to extract spatio-temporal features. The attention mechanism computes the corresponding weight of output features. The results show that the proposed method's recognition accuracy reaches 93.7%. The comparison study with the existing models validates the proposed method's superiority and shows that its accuracy is higher than that of the existing models (more than 0.9%) or their combined models (more than 1.1%). Overall, the proposed method contributes to the safety, reliability, and operation of natural gas pipelines. • An intelligent feature recognition method fo pipelines based on GTFE-Net-BiLSTM and attention mechanism is proposed. • GTFE-Net is used for time-frequency enhancement of the raw signal. • AM is used to calculate the weight of output features and improve the classification accuracy of the model. • A real-world IMU detection data is used for model training and validation. [ABSTRACT FROM AUTHOR]

A gas pipeline system is in an almost continual state of transition due to changing gas demand. A control method is required to keep a gas pipeline operating in an energy-saving status and provide reliable transmission service for the customers. Model predictive control (MPC) predicts the future states of a system, making it suitable for following gas demand changes. However, to avoid computation time challenges associated with formulating the MPC problem as a large-scale MINLP, an online two-level MPC system is proposed, comprising an upper-level economic MPC (EMPC) and a lower-level tracking MPC (TMPC). EMPC adopts energy cost as the objective function and utilizes a simplified nonlinear model to address long-horizon optimization, while TMPC tracks the status optimized in EMPC, to find the optimal output pressure and the on-off status of the compressors and compressor stations. The performance of the method is demonstrated through application to case studies. • Novel 2-layer MPC strategy for optimal operation of gas pipeline networks. • Upper-level economic MPC (EMPC) and a lower-level tracking MPC (TMPC). • EMPC utilizes aggregate compressor station model for longer economic prediction horizon. • TMPC determines on/off switching of the compressors and compressor stations. • Performance of the approach demonstrated on case studies. [ABSTRACT FROM AUTHOR]