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The underground pipeline is a critical component of urban water supply and drainage infrastructure. However, the absence of accurate pipe information frequently leads to construction delays and cost overruns, adversely impacting urban management and economic development. To address these challenges, the digital management of underground pipelines has become essential. Despite its importance, research on the structural analysis and reconstruction of underground pipelines remains limited, primarily due to the complexity of underground environments and the technical constraints of LiDAR technology. This study proposes a framework for reconstructing underground pipelines based on unstructured point cloud data, aiming to accurately identify and reconstruct pipe structures from complex scenes. The Random Sample Consensus (RANSAC) algorithm, enhanced with parameter-adaptive adjustments and subset-independent fitting strategies, is employed to fit centerline segments from the set of center points. These segments were used to reconstruct topological connections, and a Building Information Model (BIM) of the underground pipeline was generated based on the structural analysis. Experiments on actual underground scenes evaluated the method using recall rate, radius error, and deviation between point clouds and models. Results showed an 88.8% recall rate, an average relative radius error below 3%, and a deviation of 3.79 cm, demonstrating the framework's accuracy. This research provides crucial support for pipeline management and planning in smart city development. [ABSTRACT FROM AUTHOR]

The paper introduces a new algorithm that can determine the location of the compromised pipeline and its path while also examining the impact of the sensor array's parameters on imaging outcomes. Results show that the sensor array rotates at a specific angle relative to the pipeline, and the pipeline's path remains visible. Experimental trials using a vibration sensor to capture vibrational data indicate that at an acceleration of water reaching 9 m/s2, the maximum output analog voltage (corresponding to the leakage point) reaches 35.6 mv, with the analog voltage decreasing as one moves away from the main leakage point, thereby validating the viability of the new algorithm. Rotating the pipeline at a certain angle can result in an output analog voltage of up to 37.4 mv, and the presence of the leaking pipe and its path continues to be observable. [ABSTRACT FROM AUTHOR]

In the rapid development of urban construction, underground pipelines play a crucial role. However, the current underground pipelines have poor association with relevant management departments, and there are deficiencies in data completeness, accuracy, and information content. Managing and sharing information resources is relatively difficult, transforming the constructed 3D underground pipeline geographic information systems into an 'Information silo'. This results in redundant construction and resource wastage of underground utilities. The complex distribution characteristics of underground utilities make rapid batch modeling and post-model maintenance challenging. Therefore, researching a 3D spatial data fusion model for urban underground utilities becomes particularly important. Given the above problem, this paper proposes a spatial data fusion model for underground pipeline scene modeling. It elaborates on the geometric, semantic, and temporal characteristics of underground pipelines, encapsulating these features. With underground pipeline objects as the core and pipeline characteristics as the foundation, a spatial data fusion model integrating multiple characteristics of underground pipelines has been constructed. Through software development, the data model designed in this paper facilitates rapid construction of underground pipeline scenes. This further enhances the consistency and integrity of underground pipeline data, enabling shared resources and comprehensive supervision of facility operations on a daily basis. [ABSTRACT FROM AUTHOR]

In the rapid development of urban construction, underground pipelines play a crucial role. However, the current underground pipelines have poor association with relevant management departments, and there are deficiencies in data completeness, accuracy, and information content. Managing and sharing information resources is relatively difficult, transforming the constructed 3D underground pipeline geographic information systems into an ‘Information silo’. This results in redundant construction and resource wastage of underground utilities. The complex distribution characteristics of underground utilities make rapid batch modeling and post-model maintenance challenging. Therefore, researching a 3D spatial data fusion model for urban underground utilities becomes particularly important. Given the above problem, this paper proposes a spatial data fusion model for underground pipeline scene modeling. It elaborates on the geometric, semantic, and temporal characteristics of underground pipelines, encapsulating these features. With underground pipeline objects as the core and pipeline characteristics as the foundation, a spatial data fusion model integrating multiple characteristics of underground pipelines has been constructed. Through software development, the data model designed in this paper facilitates rapid construction of underground pipeline scenes. This further enhances the consistency and integrity of underground pipeline data, enabling shared resources and comprehensive supervision of facility operations on a daily basis.

In this study, a machine learning-based prediction model was developed using the attribute information of underground pipelines and the history information of ground subsidence in order to predict the risk level of ground subsidence in urban areas. The target area was divided into a grid with sizes of 100m $\times 100\text{m}$ , 300m $\times 300\text{m}$ , and 500m $\times 500\text{m}$ , and the attribute information of underground pipelines in the grid and ground subsidence data were utilized to build a dataset. For input data, the pipeline’s diameter, the number of years used, and density were selected based on the pipeline’s length as the basic unit. Additionally, the risk level of ground subsidence was determined as the output data using historical information. A total of 36 datasets were built according to the conditions, and factors with significant correlation were selected through a correlation analysis of the datasets. The developed datasets were divided into training data and evaluation data. The synthetic minority oversampling technique was used to resolve the data imbalance. The model performance evaluation indexes used in this study were F1-score and AUC(Area Under the Curve). The performance of each model was compared, and the comparison results showed that a model that applied a preprocessed dataset with 500m $\times 500\text{m}$ grid size, 10 years in use, 100mm pipeline diameter, and 1–2 ground sinks in Level 1 risk range to the LGBM(Light Gradient Boosting Model) classifier derived the best evaluation indexes(F1-Score:0.750, AUC:0.840). The map was found to be effective for predicting the risk level of ground subsidence in urban areas.

Online monitoring of natural gas in urban underground space has proven to be an effective method for resolving minor leakage and explosion accidents in urban low-pressure natural gas pipelines. However, the harsh environment of urban underground space is often accompanied by the generation of biogas, whose components are more similar to those of natural gas, causing great disturbance to early warning of natural gas leakage. This study correlates the biogas generation principle and its transport law with human activities and environmental changes, analyzes and extracts the characteristics of the natural-gas-biogas CH 4 concentration using big data analysis technology, and establishes a natural-gas-biogas sample database. The imbalance between positive and negative samples in the database is addressed by two oversampling techniques. The models trained by two different machine learning algorithms were then evaluated. The results of the study are summarized as follows: (1) There are daily and annual cycles in the CH 4 concentration in biogas. The daily trend of biogas in the same manhole is similar, and the biogas in different manholes shows various changes periodically with human activities. Biogas early warnings often occur during the high temperature season (April-September). (2) Features such as period, temperature of alarm, and average concentration over 24 h are positive for improving model accuracy. (3) The combined model of XGBoost and the borderlineSMOTE algorithm has an f-score of 72.7 %, an accuracy of 71.2 %, and a recall of 73.4 %. Compared with the traditional manual classification method, the model proposed in this study can identify natural gas and biogas in a more real-time and accurate manner, reduce the workload of on-site confirmation, and effectively shorten the emergency response time. [ABSTRACT FROM AUTHOR]

In this study, a new mechanical model is proposed to compute earth pressure above a pipeline considering pipe-soil interaction and three-dimensional soil arching effects of cohesive fills, based on the Terzaghi vertical sliding surface theory. In this model, the pipeline was mechanically separated into buried and suspended segments, whose stress distribution and deformation were solved according to the boundary conditions and geometric conditions. Comparisons to both the test data and corresponding finite element codes concretely verify the proposed mechanical model. Then a parametric investigation indicated that the mechanical behavior of the pipe is greatly affected by the size of a subsidence area and the flexural rigidity of the pipe. [ABSTRACT FROM AUTHOR]

Underground pipelines are the lifelines of a modern city. The precise positioning of underground pipelines is essential to avoid pipeline damage during successive construction above it. However, detecting deep-buried pipelines in soft clayey deposits is challenging. This paper proposes a new method called the surface-to-borehole electromagnetic induction method (SB–EIM) by combining the traditional ground EIM with the magnetic gradient response in a borehole. Firstly, a depth measurement method was established based on the magnetic fl ux response to the applied magnetic field in a borehole. Secondly, a theoretical analysis method was proposed to calculate the pipeline depth and its horizontal position using the measured data. By analyzing the magnetic flux response characteristics at different depths, the relationship between the maximum response point and the spatial location of the target pipeline was determined. Finally, an in-situ test was conducted, and the eff ectiveness of the proposed method was verified. [ABSTRACT FROM AUTHOR]

The possibility of partial splitting of the dynamic equations of the linear theory of elasticity for bulk expansion and the components of the rotation vector of medium particles in cylindrical coordinates in the general case of a nonstationary problem is proved. This result is a generalization of a similar fact established by A. Love with a simple harmonic dependence of the named functions on time and two spatial coordinates. An exact analytical solution of the problem on bending vibrations of an elastic space with a circular cylindrical cavity (external Pochhammer–Chree problem) is given. It is shown that the study published by K. Toki and Sh. Takada on this problem does not provide a solution to the posed problem. On the basis of the solution obtained for the external Pochhammer–Chree problem, bending vibrations of an underground pipeline caused by the action of a seismic wave are studied. The results obtained in this case provide, apparently, the first theoretical substantiation of the engineering theory of rigid jamming of the pipeline in the soil for the case of bending vibrations, widely used in regulatory documents on seismic construction. [ABSTRACT FROM AUTHOR]

To ensure the reliable management of the safe operation of an underground pipeline in a chemical industrial park and accurately determine the location of the pipeline leakage point, a precise location method for the leakage point of an underground pipeline in a chemical industrial park based on ultrasonic creeping wave flaw detection and data integration is proposed. In this method, the ultrasonic creeping wave flaw detector is used to detect the underground pipelines in the chemical industry park and obtain the status signals of the underground pipelines in the chemical industry park. The improved K-means algorithm is used to fuse the signals collected by clustering to obtain abnormal signals in the signals; The wavelet transform is used to process the ultrasonic abnormal signals obtained by clustering, extract the local time energy density characteristics of the frequency band, and superimpose the image. By introducing image enhancement factors, the leakage area can be centrally located, the coordinates of the pipeline leakage points can be determined, and the leakage degree can be determined by calculating the sum of the damage probability of each leakage point. The test results show that the clustering effect of this method is good, and the separability measurement indexes are all above 0.925, which can complete the location of single point and multi-point leakage points, and the maximum location error is 11.55 mm. The reliability of the location of the leakage point is high.

The paper considers a set of issues affecting the actual problems of operational repair and restoration work on underground pressure water and drainage pipelines made of various materials that have exhausted their standard service life and are subject to numerous defects in the form of cracks, joint divergences, rust growths, fistulas and others. The aim of the work is to consider trenchless technology as a promising method of repairing dilapidated pipelines, which uses the application of polymer hoses to the inner surface of pipeline networks. The general requirements for flexible polymer sleeves and their characteristics, the scope of application of sleeves, as well as requirements for structural materials used in the production of flexible polymer sleeves are considered as the subject of research. The result of the work is an analysis of the sequence and essence of preparatory operations, including in-line diagnostics and a coding system for the results of visual inspection of pipelines. As conclusions, examples of calculating energy savings during water transportation before and after repair and restoration work at an exemplary facility are given, depending on the technical characteristics of the hoses used, as well as their thickness, depending on the depth of the pipeline.

Leaks in pipelines caused by acid are destructive to both economic growth and capital which should be avoided at all costs. Damage to underground pipelines is caused by a hard-to-find leak, the unavailability of a real-time monitoring system and the lack of a pipeline history database. The aim of this work is to develop an early warning system to detect acid leaking in the pipeline using Internet of Things (IoT) technology. To detect changes in the pH of acid soil parameters near the pipeline, two mechanisms are required: first, to provide an early warning before the leak is detected and second, to report the occurrence of the leak. The notification system is equipped with three LED indicators, each showing the offline, online and signal detection status. The novelty of the work is a prototype that can detect the acid leak in the pipeline and record the pH values in a database for future research. Using continuous pH monitoring, real-time analysis and a database, this system can detect leaks before they become a major problem. Consequently, the manufacturing industry will benefit from this initiative as it is automated, efficient and cost-effective. [ABSTRACT FROM AUTHOR]

Stationary oscillations of an underground pipeline caused by oblique incidence of a plane seismic wave are investigated. It is shown that an oblique wave can be represented as several longitudinal and transverse waves propagating along the pipeline at higher velocities. The statement of the coupled problem of joint longitudinal vibrations of elastic soil and pipeline is given. The obtained analytical solution of the external problem for the soil leads to a theoretical expression for the force of interaction between the pipeline and the soil, for which only empirical relationships were previously proposed. Solutions for pipelines in supersonic and subsonic modes demonstrate a significantly different nature of their behavior, which should be taken into account in seismic calculations. [ABSTRACT FROM AUTHOR]

• A novel sewer defect classification model based on the vision transformer (ViT) is proposed. • Two cost-sensitive learning algorithms are incorporated to deal with the imbalanced multi-class sewer dataset problem. • The model outperforms several state-of-the-art CNN models in terms of precision, recall, and F1-score. • The model demonstrates the potential of applying the transformer architecture to sewer defect identification. Sewers are a critical component of urban infrastructure, presenting significant challenges in efficiently detecting defects. Currently, Convolutional Neural Networks (CNNs) are widely applied in CCTV inspections for defects in sewers. However, images of these defects commonly suffer from dataset imbalance, and CNNs can only capture local features of images, lacking a comprehensive understanding of the global image and performing poorly in generalizing across imbalanced datasets. Therefore, we introduces a classification model for sewers based on the self-attention mechanism, SViT/CE, tailored for imbalanced datasets, and proposes the SViT/WCE and SViT/FL models. The results demonstrate that the SViT/CE model achieves precision, recall, and F1-score of 53.64%, 58.51%, and 55.97% respectively on the test set. The SViT/WCE model achieves 55.87%, 59.53%, and 57.64%; the SViT/FL model scores 54.13%, 62.91%, and 58.19%. In comparison, the best-performing model among the baseline models scores 41.56%, 42.86%, and 42.02% in precision, recall, and F1-score, respectively, with the SViT series models outperforming the baseline models across all three metrics. The SViT/WCE and SViT/FL models show improvements of 2.06%, 1.02%, 1.67%, and 0.49%, 4.40%, 2.22% over the SViT/CE model in precision, recall, and F1-score, respectively. This study provides an efficient self-attention mechanism model for the classification task of sewer image defects, ensuring the safety and stable operation of urban drainage infrastructure. [ABSTRACT FROM AUTHOR]

The coupled unsteady vibrations of an underground pipeline and elastic soil caused by an inclined fall of a plane seismic wave are studied. The coupled self-similar problems are formulated. An analytical solution of the external problem for the soil is obtained. This solution leads to a theoretical expression for the force of interaction between the pipeline and the soil, for which only empirical relations were previously available. Solutions for pipeline in supersonic and subsonic cases demonstrate significantly different behavior, which should be taken into account during earthquake resistance calculations. [ABSTRACT FROM AUTHOR]

High-precision detection of the underground pipelines is an indispensable part of the development and construction of cities. At present, the inversion technology for ground-penetrating radar (GPR) data is an effective means of realizing shallow-underground-space visualization in the field of geophysical exploration. However, the traditional full-waveform inversion (FWI) method usually faces the problems of strong nonlinearity of the objective function, high dependence on the initial model, and huge calculation cost. For improving the accuracy and efficiency of GPR data inversion, a wavefield reconstruction inversion (WRI) strategy is used for GPR data imaging to reduce the nonlinearity of the inversion problem and the dependence on the initial model. Then, the frequency weighting strategy and the multi-scale method are adopted to avoid the high-frequency component data dominating the optimization process and enhance the stability of inversion. In this paper, two numerical experiments of pipeline models with different materials and spacing or buried depths verified that the proposed method can effectively reconstruct the subsurface pipelines, and further performance of our algorithm on the field data verified the reliability of high-precision imaging of urban underground pipelines, which shows great potential of application in the field of high-precision detection of the urban underground pipelines. [ABSTRACT FROM AUTHOR]

For long-span structures, such as long bridges and underground pipelines, the loss of correlation of ground movements during an earthquake should be taken into account for seismic analyses. In this paper, longitudinal seismic responses of underground pipelines, which are modeled as distributed mass pipelines with fixed-fixed ends, are derived with a pseudo-excitation method. The seismic excitation is considered a random process and partially correlated. The root mean square (RMS) axial stresses and displacements are compared between pipelines with fixed-fixed and free-free ends. The effects of slenderness ratio and pipe thickness on the seismic responses are also investigated. The results show that the seismic response of fixed-ends and free-ends pipelines matches well when the slenderness ratio is large enough. On the contrary, the boundary conditions should be taken into account for short pipes or pipes with a large external radius. The RMS axial stresses at the midpoint of the pipes decrease with the increase of pipe thickness, and no significant difference is found between fixed-ends and free-ends pipes. [ABSTRACT FROM AUTHOR]

We propose new methods for the analysis of regularities of the kinetics of growth of external corrosion crack in the walls of underground metal pipelines with regard for the given internal pressure and cathodic protection. They are based on the analysis of corrosion currents at the crack tips taking into account the mechanical stresses, Ohmic potential drop, and overvoltage of the anodic dissolution of the metal. We propose an improved method for the evaluation of the service life of underground metallic pipelines in view of the influence of mechanical stresses formed in the vicinity of the crack tip on corrosion currents. It is shown that mechanical stresses lead to a decrease in the service life of the pipeline by a factor of 3.6 as compared with the case where the internal pressure is close to atmospheric. [ABSTRACT FROM AUTHOR]

Ground-penetrating radar (GPR) is widely used in the detection and positioning of underground facilities. Through the inversion analysis of echo signals of GPR, information such as pipe material, burial depth and location of pipelines can be obtained. Unfortunately, underground pipelines are cylindrical, the ladder approximation method used in traditional forward models produces certain errors. In this study, an accurate and efficient numerical model of GPR forward model in underground pipelines is established using symplectic Euler algorithm, graphics processing unit (GPU) acceleration technology and surface conformal technology. With a Ricker wavelet pulse as the GPR source, the convolution perfectly matched layer (CPML) is incorporated in the symplectic Euler algorithm and shown to be effective to truncate the symplectic Euler computational domain. Through the simulation study of different underground pipeline models, GPR image characteristics of the metal pipeline, plastic pipeline and concrete pipeline filled with air and water are obtained. According to the numerical simulation results, parallel conformal symplectic Euler algorithm effectively reduces the false diffracted waves caused by ladder approximation and improves the computational efficiency of the model in metallic and non-metallic media.

The stability of a pipeline jointed to a unit interacting with the surrounding soil is analyzed. The pipeline is subject to axial compression. The stress state of the pipeline body (elastic beam) is directly related to the uplifting of the unit. The axial force at which the stress reaches the critical value is calculated. The influence of the stiffness coefficient (soil conditions) and the location of the unit on the stability of the pipeline are shown. Calculated results for the unit fixed at the middle of the beam (pipeline) and for its asymmetric location are given. The results are presented in the form of curves of the reduced dimensionless frequency and distribution of the longitudinal stress along the beam axis and commented. It is revealed that the asymmetric location of the unit leads to a decrease in the critical force at which stability loss occurs. [ABSTRACT FROM AUTHOR]

Featured Application: Main gas and oil pipelines are critical elements of the world's infrastructure. The integrity of pipelines during earthquakes is a subject of intensive research. At present, underground pipelines' strength to the effect of seismic loads (seismic resistance) is calculated incorrectly. The existing methods do not consider seismic (dynamic) pressure, i.e., the stress normal to the pipeline's outer surface arising from the propagation of a seismic wave in the soil. This leads to an incorrect determination of the pipeline's stress; the longitudinal stress calculations leads to errors of 100% or more. A potential application of the results obtained is the calculation of seismic stability of underground pipelines. The object of the research is an underground straight horizontal pipeline subjected to seismic impact. The research method was analytical. The results were compared with the experimental results of other authors and computer calculations. It was shown that the main disadvantage of the dynamic theory of seismic resistance of underground pipelines is the neglect of the dynamic stress state in soil under seismic wave propagation. The next drawback of the dynamic theory is an inaccurate, approximate accounting for the displacement of the soil medium to which the underground pipeline is embedded. The complete interaction process includes the stages of nonlinear changes in the interaction force (the friction force) by manifesting its peak value and the Coulomb friction. The contact layer of soil undergoes shear deformations until complete structural destruction of the soil contact layer. The interaction force is the friction force, and its peak value does not appear. The seismic resistance of underground pipelines should be considered based on the theory of propagating seismic waves in a soil medium and the interaction of seismic waves with underground pipelines, i.e., based on the wave theory of seismic resistance of underground pipelines. A one-dimensional coupled problem of seismic resistance of underground pipelines under seismic impacts was posed based on the wave theory. An algorithm and a program for the numerical solution of the stated wave problems were developed using the method of characteristics and the method of finite differences. An analysis of the laws of interaction of underground pipelines with soil under seismic influences shows that it is necessary to use in the calculations the laws of interaction that account for the complete interaction processes observed in experiments. The analysis of the obtained numerical solutions and the posed coupled problems of the wave theory of seismic resistance of underground pipelines show the occurrence mechanisms of longitudinal stresses in underground pipelines under seismic influences. The results of calculations stated that an account for the dynamic stress normal to the underground pipeline's outer surface leads to multiple increases in longitudinal stress in the underground pipeline. This multiple increase is due to the transformation of the interaction force into an active frictional force, resulting from a greater strain in soil than the one in the underground pipeline. Based on the analysis results, a theory of the seismic wave propagation process in an underground pipeline and surrounding soil was proposed. [ABSTRACT FROM AUTHOR]

The ground penetrating radar was applied to the detection of underground pipeline. The signal of ground penetrating radar was analyzed to simulate the different sizes of pipelines and oil. The data were processed by GRED HD software. Radar profiles and single-channel waveforms of underground pipelines and oil were obtained. The nonstationary signals of geological radars were processed and analyzed by the finite-difference time-domain method. The different radar characteristic signals of underground pipelines and radar signal variations of pipeline oil were discussed. It can improve the accuracy of interpretation of underground pipelines and oil. [ABSTRACT FROM AUTHOR]

Underground pipeline networks constitute a major component of urban infrastructure, and thus, it is imperative to have an efficient mechanism to manage them. This study introduces a secondary development system to efficiently model underground pipeline networks, using the building information modeling (BIM)-based software Revit. The system comprises separate pipe point and tubulation models. Using a Revit application programming interface (API), the spatial position and attribute data of the pipe points are extracted from a pipeline database, and the corresponding tubulation data are extracted from a tubulation database. Using the Family class in Revit API, the cluster in the self-built library of pipe point is inserted into the spatial location and the attribute data is added; in the same way, all pipeline instances in the pipeline system are created. The extension and localization of the model accelerated the modeling speed. The system was then used in a real construction project. The expansion of the model database and rapid modeling made the application of BIM technology in three-dimensional visualization of underground pipeline networks more convenient. Furthermore, it has applications in pipeline engineering construction and management. [ABSTRACT FROM AUTHOR]

The induced voltage on underground pipelines is a critical parameter to consider for equipment and personnel safety in the field. However, in the real life, such induced voltage estimation on pipelines is difficult especially at the transmission line planning and routing stage. In this article, several factors affecting the induced voltage on underground pipelines due to inductive coupling with nearby transmission lines are investigated. These factors include the angle and separation distance between transmission lines and pipelines, the length of transmission lines and pipelines, and the soil model. A peak induced voltage calculation formula as the function of the angle and separation distance is derived through surface fitting of simulation data. It is proved in the article that other factors, such as the length of the transmission line and the soil model types, do not have significant influence on the peak induced voltage values on underground pipelines. [ABSTRACT FROM AUTHOR]

Due to the non-conductive and non-magnetic properties, nonmetallic pipelines are difficult to be detected by traditional pipe location technologies. This paper presents a superimposed imaging method of acoustic wave reflections for pipe location, which operates on the propagation of elastic waves. The propagation and attenuation model of elastic waves in soil are constructed according to the geometric relationship between the acoustic source, geophone array and pipelines. The two-dimensional and three-dimensional acoustic field diagrams of underground pipeline are generated by superimposed imaging of the cross-correlation coefficients between the signals from the sound source and geophone array, with the attenuation caused by hysteretic damping and geometric dissipation considered in the imaging process. In order to suppress clutter interference on the imaging results, the strategy of 'multi-point transmit, multi-point receive and cross-correlation coefficient superposition' is adopted. In the simulation, comparison is made to demonstrate the influences of different excitation sources on the detection imaging results, including the single frequency signal, multi-frequency signal, Gaussian pulse signal and sweep signal. It is found that the excitation signals with rich frequency components are more conducive to improving the resolution of detection images. The effectiveness of the proposed imaging method is further verified in the experimental work, which may be beneficial for the visualization and determination of the location, depth and orientation of underground non-metallic pipelines. [ABSTRACT FROM AUTHOR]

A stochastic corrosion growth model is established for underground pipeline structures. The model has been developed with the concept in mind that the evolution of localized corrosion damage is time-dependent following an activation stage (nucleation) – growth stage (propagation) – steady state stage (passivation) mechanism. The temporal correlation of the defect evolution is able to be well represented by a geometric Brownian bridge process. The variation of activation time is taken into consideration. Two applications are illustrated: 1) predicting the evolution of the probability density function (PDF) of the corrosion depth, and 2) assessing the reliability of a pipeline structure. [ABSTRACT FROM AUTHOR]

Underground pipelines have a space-dependent condition that arises from various soil properties surrounding the pipeline (e.g., moisture content, pH, aeration) and the efficiency of protection measures. Corrosion is one of the main threats for pipelines and is commonly monitored with in-line inspections (ILI) every 2 to 6 years. Preliminary characterizations of the surrounding soil allow pipeline operators to propose adequate protective measures to prevent any loss of containment (LOC) of the fluid being transported. This characterization usually requires detailed soil measurements, which could be unavailable or very costly. This paper implements categorical measurements of soil properties and defect depth measurements obtained from ILI to characterize the soil in the surroundings of a pipeline. This approach implements an independence test, a multiple correspondence analysis, and a clustering method with K-modes. The approach was applied to a real case study, showing that more severe defects are likely located in poorly drained soils with high acidity.

The object of the research is an underground straight horizontal pipeline subjected to seismic impact. The research method was analytical. The results were compared with the experimental results of other authors and computer calculations. It was shown that the main disadvantage of the dynamic theory of seismic resistance of underground pipelines is the neglect of the dynamic stress state in soil under seismic wave propagation. The next drawback of the dynamic theory is an inaccurate, approximate accounting for the displacement of the soil medium to which the underground pipeline is embedded. The complete interaction process includes the stages of nonlinear changes in the interaction force (the friction force) by manifesting its peak value and the Coulomb friction. The contact layer of soil undergoes shear deformations until complete structural destruction of the soil contact layer. The interaction force is the friction force, and its peak value does not appear. The seismic resistance of underground pipelines should be considered based on the theory of propagating seismic waves in a soil medium and the interaction of seismic waves with underground pipelines, i.e., based on the wave theory of seismic resistance of underground pipelines. A one-dimensional coupled problem of seismic resistance of underground pipelines under seismic impacts was posed based on the wave theory. An algorithm and a program for the numerical solution of the stated wave problems were developed using the method of characteristics and the method of finite differences. An analysis of the laws of interaction of underground pipelines with soil under seismic influences shows that it is necessary to use in the calculations the laws of interaction that account for the complete interaction processes observed in experiments. The analysis of the obtained numerical solutions and the posed coupled problems of the wave theory of seismic resistance of underground pipelines show the occurrence mechanisms of longitudinal stresses in underground pipelines under seismic influences. The results of calculations stated that an account for the dynamic stress normal to the underground pipeline’s outer surface leads to multiple increases in longitudinal stress in the underground pipeline. This multiple increase is due to the transformation of the interaction force into an active frictional force, resulting from a greater strain in soil than the one in the underground pipeline. Based on the analysis results, a theory of the seismic wave propagation process in an underground pipeline and surrounding soil was proposed.

• A 3D trajectory measurement method for pipelines based on inertial navigation. • A high-reliability measurement algorithm based on multiple sensors. • An algorithm based on the fusion of time forward and time reverse Kalman filter. • A time-saving method that only needs one trip from inlet to outlet of pipeline. • A high-precision algorithm that can correct sensor errors. The three-dimensional (3D) trajectory measurement of underground pipelines is the basis for establishing an underground pipeline network system. Mastering the trajectory of underground pipelines can reduce damage to old pipelines during construction. Traditional pipeline measurement methods have limitations in terms of depth and environment, leading to the inability to obtain accurate information on the pipeline trajectory. In this study, a forward and reverse Kalman filtering fusion measurement algorithm based on MEMS-IMU, MEMS magnetometer, and the odometer was proposed. First, a 16-dimensional Kalman filtering model was established according to the motion mode and working environment of the pipeline measurement instruments; Secondly, based on the 16-dimensional Kalman filtering model, the data of multi-sensors were fused according to the forward and reverse time order respectively. Thus, two kinds of 3D trajectories of the pipeline were obtained. One is the time order, the other one is the reverse time order. Thirdly, in order to get the optimal measurement results of the 3D trajectory of the pipeline, the forward and reverse measurement results were fused according to the covariance matrix of the forward and reverse Kalman filter. Finally, a ground simulation experiment and an underground pipelines experiment with a MEMS sensor (PA-IMU488B) were performed to verify the feasibility of the method. In the ground simulation experiment, the maximum relative error in the plane is 0.14%, and the maximum relative error in the vertical is 0.28%. In the experiment of underground drainage pipelines, the maximum relative error in the plane is 0.22%, and the maximum relative error in the vertical is 0.12%. This method proposed by this study uses one set of data twice which can make the measurement results more accurate. Above all, the sensors used in this method are all cheap and low precision. Moreover, the measuring equipment only needs to travel through the pipe from the entrance to the exit and doesn't need to go back from the exit to the entrance. Therefore, the method proposed by this study is a high-precision, low-cost, and low-time-consuming method for 3D trajectory measurement of underground pipelines. [ABSTRACT FROM AUTHOR]

Underground pipe network is a critical city infrastructure, which plays an important role in smart city management. As the detailed three-dimensional (3D) scene of underground pipe networks is difficult to construct, and massive numbers of pipe points and segments are difficult to manage, a 3D pipe network modeling and organization method is explored in this study. First, the modeling parameters were parsed from the pipe network survey data. Then, the 3D pipe segment and point models were built based on parametric modeling algorithms. Finally, a heterogeneous data structure for the 3D pipe network was established through loose quadtree data organization. The proposed data structure was suitable for 3D Tiles, which was adopted by Cesium (a web-based 3D virtual globe); hence, a multitude of pipe networks can be viewed in the browser. The proposed method was validated by generating and organizing a large-scale 3D pipe network scene of Beijing. The experimental results indicate that the 3D pipe network models formed by this method can satisfy the visual effect and render the efficiency required for smart urban management.

Parallel and crossing pipelines are frequently implemented due to land-use restrictions and their ease of operation and maintenance. Given the proximity of these pipelines and the hazardousness of the substances they transport, an eventual Loss of Containment (LOC) in a parallel/crossing corridor can lead to a domino effect that should be considered in Quantitative Risk Analysis (QRA). For underground pipelines, this LOC is accompanied by a formation of a crater, which can uncover adjacent pipelines triggering a domino effect scenario to take place. This paper aims to develop a model to predict feasible crater dimensions (i.e., width and depth) from a LOC in underground natural gas pipelines using operational and structural parameters. For this purpose, a recent review of 57 underground natural gas pipeline accidents were considered in a probability-based approach once data was processed. This approach initially predicts the Width-to-Depth crater ratio (WD) using a multivariate regression. Then feasible crater dimensions were determined using the regression prediction interval and the width-depth joint probability function, which is approximated with a Gaussian copula. This approach proposes a worst, mean and less severe scenarios to support decision-making processes regarding parallel or crossing underground natural gas pipelines with a LOC. Besides the identification of domino effect scenarios, this information can be used to support pipeline segmentation for risk analysis or even to support Right-of-Way (ROW) definition during pipeline installation. [ABSTRACT FROM AUTHOR]

• The evolutionary process of pipe jacking method in Japan was reviewd. • The classification system provided by the Japan Microtunneling Association was introduced. • The application status of this method is investigated based on survey data from JSTT. • SPJ and HDSPJ have better performance for the ultra-long pipe jacking construction. • Curved pipe jacking projects account for 40% of total jacking projects, and HDSPJ is most adopted for curved pipe jacking. Pipe-jacking is one of the trenchless methods being widely used for the construction and maintenance of urban underground pipelines. As an eco-friendly construction method, it has the capacity for the installation of pipelines with diameters from 100 mm (4 in.) to 5000 mm (200 in.) covering the majority needs of municipal pipeline construction and is considered the most widely used trenchless method in Japan. However, there is little English literature that systematically introduces the research and application status of pipe jacking technology in Japan, resulting in a serious underestimation of Japanese research achievements in this field. This paper briefly reviews the origin, evolutionary stages, and classification system of the pipe jacking method in Japan, and representative technological advances are also introduced through case statistics. Meanwhile, the deficiencies in the current classification system of the International Society of Trenchless Technology (ISTT) are discussed as well. In addition, the application status of this method is investigated based on survey data from the Japan Society for Trenchless Technology (JSTT). According to the survey data from 5232 projects, a systematic analysis is carried out on the selection of pipe jacking equipment, the scale of jacking construction, the profile of curved projects, and the geological adaptability of the pipe jacking method in Japan. The emphasis of this paper is to introduce the current technical situation and analyze the development trends of the pipe-jacking method based on Japan's experience, and to popularize this method in other countries that need this simple, effective, and economical construction technique under the background of climate change. [ABSTRACT FROM AUTHOR]

Due to the long term usage and irregular maintenance for corrosion checks, catastrophic accidents have been increasing in underground pipelines. In this study, a new safety management methodology of underground pipeline, risk-based pipeline management, is introduced reflecting corrosion effect. First, principle of the risk-based pipeline management is presented compared with an original method, qualitative measure. It is distinguished from the qualitative measure by reflecting societal risk and corrosion in safety management of underground pipeline. And then, it is applied to an existing underground propylene pipeline in Ulsan Industrial Complex, South Korea. The consequence analysis is based on real information, and the frequency analysis reflects degree of corrosion. For calculation of corrosion rate, direct current voltage gradient (DCVG) and close interval potential survey (CIPS) are conducted. As a result of applying the risk-based pipeline management, risk integral is reduced by 56.8% compared to the qualitative measure. Finally, sensitivity analysis is conducted on variables, which affect the risk of the pipeline. This study would contribute to introduce quantitative measure to pipeline management and increase safety of pipeline. [ABSTRACT FROM AUTHOR]

Due to the humid climate in Taiwan area, the underground pipes are prone to be damaged by corrosion, which could be more severe for the environment with high salinity near the coast. In addition, the situation could be worse where the underground pipeline planning was not enforced. For example, a water pipe or a sewage pipe may be too close to a pressurized pipe, which could be corroded if the water pipe or the sewage pipe leaked. In this study, the numerical simulation software ABAQUS was used to simulate underground pipelines damaged by corrosion. The stress and displacement behavior was analyzed for scenarios with different internal pressure and surface loading conditions. In addition, the performance of the cured-in-place-pipe (CIPP) method, a trenchless rehabilitation method was also numerically analyzed. The results suggest that it can reinforce the damaged pipe by reducing the stress concentration and reducing the differential displacement. However, the design of the CIPP liner could be further optimized in terms of its design thickness. [ABSTRACT FROM AUTHOR]

It is shown that the method of contactless current measurement (CCM) makes it possible to perform rapid monitoring of the state of corrosion protection in different sections of underground pipelines, determine the state and detect defects in the insulation of underground pipelines (UGP). The method of simultaneous measurements of direct-current and alternating-current voltages enables us to determine the polarization potential (with removal of the Ohmic component) which is regarded as the main criterion for the monitoring of electrochemical corrosion protection of the metal in conducting media. The realization of this method in the equipment aimed at measuring the polarization potential makes it possible to detect defects of the insulation both by using an alternating current (Pearson method) and according to the potential drop on the surface of soil (gradient method). The use of a GPS modulus in the developed BVS-K installation guarantees the possibility of automatic determination of the geographic coordinates and the time of measuring the current and depth of the underground pipelines, which strongly facilitates the procedures of processing and documentation of the results of inspection, in particular, in the course of determination of the current density, current losses, and the 'pipe-ground' transient resistance in different sections of the underground pipeline. The contactless current measurements together with the measurements of the polarization potential enable us to determine the distributions of densities of the currents of corrosion protection, the resistivities of soils around the pipe, and the protective insulation in different sections of the underground pipeline. [ABSTRACT FROM AUTHOR]

Corrosion is often the cause of pipeline failure potentially resulting in disasters causing damage and fatalities. To maintain the integrity of non-piggable lines, NACE's external corrosion direct assessment (ECDA) methodology is commonly applied to assess external corrosion that can occur at coating defects on underground pipelines. Work presented here is from a validation exercise carried out on the results of ECDA assessment using subsequent excavation data. The ECDA was carried out over 300 km of crude oil pipelines with excavation carried out at 200 locations. This paper models the relationships between pipeline coating defect area (area with coating breakdown), corrosion depth, direct current-voltage gradient (DCVG) measurements (in terms of %IR values) and factors capturing diverse environmental conditions through novel application of regression models. This paper sheds light on the challenges in drawing conclusions in the assessment of corrosion from DCVG inspection data and other types of data that form key inputs to ECDA. We expect that the analyses shown here using innovative regression models will support more reliable predictions of external corrosion in pipelines. [ABSTRACT FROM AUTHOR]

[Display omitted] • An automatic method is established for localization of underground pipelines using GPR. • A deep learning algorithm is proposed for automatic detection of underground pipelines. • The YOLOv3 model is trained and tested using a real GPR dataset. • The buried depth of the pipeline is estimated with a high accuracy by migration and binarization. • High recognition and location accuracy is achieved on the real GPR dataset. Ground penetrating radar (GPR) is a popular non-destructive method for detecting and locating underground pipelines. However, manual interpretation of a large number of GPR B-scan images is time-consuming, and the results highly relies on the practitioner's experience and the priori information at hands. An automatic GPR method for recognition and localization of underground pipelines is proposed based on a deep learning model in the paper. Firstly, a dataset containing 3,824 real GPR B-scans of pipelines is established. Secondly, a You Only Look Once version 3 (YOLOv3) model is trained to recognize the regions of the underground pipelines in a GPR image. Thirdly, the hyperbolic response of a pipeline is focused by migration, and transformed into a binary image by an iterative thresholding method. Finally, the apex of the hyperbola is employed to estimate both the horizontal position and the buried depth of the pipeline. Field experiments validated that the absolute errors of the estimated depths are less than 0.04 m and the average relative error is lower than 4 %. It is demonstrated that the proposed method is automatic, high-speed, and reliable for recognition and localization of underground pipelines in urban area. [ABSTRACT FROM AUTHOR]

The previously proposed method of one-dimensional deformation of soil is used to solve the problems of joint seismic vibrations of an underground pipeline and elastic soil under nonideal contact conditions assuming that there is sliding at the interface and that resulting shear stresses at it are proportional either to the relative displacement of the soil particles and pipeline or to their relative speed of motion. The dependence of maximum stresses in the pipeline on the coefficients is investigated under boundary conditions. For supersonic flow around the pipeline, resonance is observed with decreasing shear stresses at the interface. [ABSTRACT FROM AUTHOR]

This study is related to underground pipeline gas explosions that occurred in the southern region of Taiwan in July 2014. This disaster, which resulted in substantial numbers of fatalities and injuries in addition to about 6 km of damaged roads, was the largest petroleum catastrophe in Taiwan's history. Because pipeline gas explosions of such a large extent are rare, the Kaohsiung District Prosecutors Office and Kaohsiung Fire Department launched an investigation in which an author of this paper participated. The aim of this paper is to explore the causes of the explosions, thereby contributing to the prevention of similar cases in the future. First, the causes of the large explosions are thoroughly investigated. Second, metallographic studies are conducted on the ruptured pipelines. Finally, the results are summarized, and conclusions are drawn. [ABSTRACT FROM AUTHOR]

The exact solution of the problem of coupled seismic vibrations of an underground pipeline and an infinite elasticmediumis given. A method dramatically simplifying the solution of the exterior problem for themedium is proposed on the basis of the established theorem on the separation of the boundary conditions for the wave potentials on the surface of the cylinder. The obtained results permit improving the incorrect consideration of the problem accepted in the literature. The exact statement of the problem allows one to use the solution of the problem as a test for estimating the accuracy of appropriate approaches and solutions in seismodynamics of extended underground structures. The results of comparison show that the solutions practically coincide both in the subsonic operation mode (when the seismic wave velocity is smaller than the rod velocity of wave propagation in the pipeline) and in the supersonic operation mode, where a resonance is possible. Thus, the high accuracy of the significantly simpler theory of one-dimensional deformation is confirmed. [ABSTRACT FROM AUTHOR]

Reliable prediction of asset condition and its likelihood of failure is one of the core requirements for a utility to establish effective asset management strategies for optimized maintenance, rehabilitation, and replacement plans. Although there have been many research efforts in academia to predict the failure of pipe assets, many utilities across the United States still find it challenging to effectively predict the likelihood of failure (LOF) of their pipeline assets. Most of them still use subjective scales and rely on engineers' anecdotal experience and judgments. This study developed a holistic procedural framework that utilities can follow to develop a data driven LOF prediction model of their pipeline assets. The unique contribution of this paper is that the framework addresses issues that a utility will encounter from data collection and data organization to LOF prediction model development, and discusses possible solutions as well. Historical performance records of sewer pipes from a major city were used to demonstrate and validate the framework. The procedural framework developed in this study is anticipated to facilitate and accelerate the practical use of advanced data-driven methods for underground pipeline asset management, which will result in more reliable and high-quality investment decisions. As a derivative of the case study, the study also found that different lengths of sewer pipes actually do change the expected life of a sewer pipe, which indicates that most of the previous deterioration models for sewer pipes without consideration of pipe length may be seriously flawed. [ABSTRACT FROM AUTHOR]

The excavation of underground pipelines in Taiwan has led to widespread complaints and, in some cases, claims for national compensation. This issue has also caused significant challenges for road authorities, directly impacting the citizens' satisfaction with the government's policy of the so-called Smooth Roads Project. This study interviewed executives from road authorities, pipeline agencies, and engineering consulting companies to obtain a thorough understanding of current underground pipeline management, public utility databases, and common duct policies in Taiwan. In addition, building information modeling (BIM) is currently applied mostly to buildings, rarely to road infrastructure. Therefore, in this study, BIM was used as a basis for developing the concept of road information modeling (RIM). According to the interview surveys, respondents generally agreed that RIM would be tremendously beneficial to underground pipeline management. This study examined frameworks and strategies for the promotion of RIM from policy, legal, technical, implementation, and application viewpoints and developed an implementable example of RIM. This study presents a significant contribution to underground pipeline management, and its findings provide a basis for improvements in road maintenance and management. [ABSTRACT FROM AUTHOR]

• Attitude error and velocity scale factor correcting based pipeline robot positioning method. • Optimization pipeline robot positioning technique of round-trip positioning data based on adaptive weights. • Pipeline mapping technique for underground pipeline robot based on inertial sensor/wheel odometer. For traditional underground pipeline robot based on the inertial sensor/wheel odometer, the outliers of the data collected by the positioning system, the attitude error of the inertial sensor and the velocity measurement error of the wheel odometer are crucial factors affecting positioning accuracy of the pipeline robot, and have a significant influence on underground pipeline maintenance and pipeline mapping. To solve the above three error factors, an enhanced positioning method for the underground pipeline robot based on the inertial sensor / wheel odometer is proposed in this paper. Firstly, basic principles including robot attitude calculation based on inertial sensors, robot velocity calculation based on wheel odometer, position calculation of pipeline robot and outliers elimination based on extrapolation fitting method are introduced; secondly, the velocity information and attitude angle of the pipeline robot is corrected by prior-backtracking method; thirdly, the round-trip positioning data optimization method based on adaptive weight is designed to improve the accuracy of the whole pipeline robot positioning system; finally, three pipelines with different lengths are introduced to verify the effectiveness and reliability of the proposed method. The experimental results show that the error of position information is no more than 0.18%, 0.07% and 0.11% of survey length, respectively. [ABSTRACT FROM AUTHOR]

In the problems of common vibrations of extended underground structures (pipelines and tunnels) and soil, an approach of the one-dimensional deformation of the medium is developed; this approach is based on the assumption that the soil deformation in the direction of seismic wave propagation coinciding with the pipeline axis is prevailing. The analytic solutions are obtained in the cases where the wave velocity in the soil is respectively less or greater than the wave velocity in the pipeline. The parameters influencing the pipeline fracture are revealed and methods for increasing the seismic stability of such structures are given. The possibility of the pipeline fatigue fracture is pointed out. The statements and solutions of parabolic problems modeling the physical phenomena in soils in the case of discontinuous velocity on the boundaries at the initial time are given. The notion of generalized vorticity diffusion is introduced and the cases of self-similarity existence are classified. A detailed analysis is performed for the non-Newtonian polynomial fluid, the medium close in properties to the rigidly ideally plastic body, and the viscoplastic Shvedov-Bingham body. In the case of physically linear medium, new self-similar solutions are obtained which describe the process of unsteady axially symmetric shear in spherical coordinates. The first approximation to the asymptotic solution of the problem of the vortex sheet diffusion is constructed in a medium with small polynomial nonlinearity. The solutions polynomially decreasing to zero as the self-similar variable increases are proposed in the class of two-constant fluids. [ABSTRACT FROM AUTHOR]

Underground pipelines, on which a city relies for survival and development, have become an important part of lifeline engineering. Underground pipelines are utilized for conveying liquid, gas or loose solid, pipeline leakage and damage occasionally resulting from corrosion. Corrosion monitoring of underground pipelines is aimed at ensuring their normal operation and preventing loss of life and property. In this paper, a new method to monitor corrosion of pipelines has been proposed to solve the mentioned problem. Under the influence of internal pressure and corrosion, the pipeline wall becomes thinner and the circumferential deformation increases. The method is to indirectly investigate pipeline corrosion by monitoring the circumferential deformation. Numerical simulation confirms that the circumferential strain curve of the pipeline wall measured by using the proposed method to describe the corrosion is feasible. The proposed method provides a new way for real-time and long-term monitoring and management of underground pipelines. [ABSTRACT FROM AUTHOR]

Scenarios of underground gas pipeline failure, crater formation, dispersion of gas, explosion and subsequent fires are investigated with semi-empirical and with CFD (Computational Fluid Dynamics) modelling. In order to strengthen the accident based learning approaches present investigations are performed in the context of recent GAIL (Gas Authority of India Limited) natural gas pipeline incident occurred in India. The foreseeability of damages to lives of people and assets due to explosion overpressure and thermal radiation are assessed. The released gas is considered as slightly dense-than-air i.e. 1.5 times. Depending on the LFL (Lower Flammability Limit) of gas the dispersion diameter and heights are predicted which followed the visual evidences appropriately. The model was furthermore tested with an even denser medium and was found to be worked well there too. The estimated explosion overpressures with the standard methods and also with CFD reproduced the scenario nicely. The effects of congestion VBR (Volume Blockage Ratio) in form of vegetation on stable atmospheric boundary layer flow is analysed and its contribution towards turbulence and hazard enhancement is studied. It is found that the major source of fatalities was higher thermal radiation emitted by pool fires of methane. The estimated thermal safety distances clearly demonstrate the ignorance/under estimation of likelihood and consequence of such hazardous events. For such incidents CFD demonstrated a strong capability to assess the pre or/and post events foreseeabilities within a reasonable amount of time and with an acceptable level of accuracy meeting the industrial needs for risk analysis. [ABSTRACT FROM AUTHOR]