Buried Polyethylene Pipelines Research Articles

Research on acoustic methods for buried PE pipeline detection based on LSTM neural networks

As an essential component of urban infrastructure construction, polyethylene (PE) pipelines face the challenging task of underground detection due to the complex and dynamic nature of the subsurface environment, diverse installation paths, and the inherent insulating properties of PE materials. In order to address the non-excavation detection of buried PE pipelines, this paper proposes an acoustic method based on the long short-term memory (LSTM) neural network. The study begins by analyzing the propagation and reflection mechanisms of elastic waves in the pipe-soil coupling system, and a impact excitation source is designed to generate the excitation signal. After establishing the experimental environment and collecting experimental data, a comprehensive analysis is conducted, and the LSTM neural network is employed for data classification to determine the presence of buried PE pipelines. Through neural network training, accurate identification of the PE pipeline’s existence and prediction of its burial depth are achieved, providing an efficient and reliable solution for buried PE pipeline detection. The practical results demonstrate the significant application prospects of the combined acoustic method and LSTM neural network in buried PE pipeline detection. This research contributes a novel solution to the field of non-destructive PE pipeline detection, with both theoretical and practical implications.

A non-excavation detection method for buried PE pipelines based on 3D time-domain stacking focusing of elastic wave reflection

This paper proposed a method for locating buried polyethylene (PE) pipelines based on three-dimensional time-domain stacking focusing on elastic wave reflections. Research is conducted on the elastic wave propagation mechanism in solids. A finite element model of the propagation of elastic waves in a pipe–soil coupling system excited by a vertically oriented source is established. The transverse wave energy component below the excitation source is zero for elastic waves excited by a vertically oriented source. Based on this characteristic, an elastic wave probe array is first used, circularly distributed around the excitation source. The symmetry of the probe array is utilized to locate the buried PE pipes in the horizontal direction. Then, interference from the transverse waves is reduced by placing the excitation source directly above the buried PE pipeline. A three-dimensional image of the buried PE pipeline is formed using high-frequency elastic wave reflection signals and three-dimensional time-domain stacking. The results show that the proposed method can determine the horizontal position and burial depth of buried PE pipes without excavation. In addition, this work is significant for the localization methods of other buried pipe materials. The related detection systems and imaging methods have certain universality and reference value for detecting other buried public facilities.

Determination of Blast Vibration Safety Criteria for Buried Polyethylene Pipelines Adjacent to Blast Areas, Using Vibration Velocity and Strain Data.

In order to ensure the safe operation of buried polyethylene pipelines adjacent to blasting excavations, controlling the effects of blasting vibration loads on the pipelines is a key concern. Model tests on buried polyethylene pipelines under blasting loads were designed and implemented, the vibration velocity and dynamic strain response of the pipelines were obtained using a TC-4850 blast vibrometer and a UT-3408 dynamic strain tester, and the distribution characteristics of blast vibration velocity and dynamic strain were analyzed based on the experimental data. The results show that the blast load has the greatest effect on the circumferential strain of the polyethylene pipe, and the dynamic strain response is greatest at the section of the pipe nearest to the blast source. Pipe peak vibration velocity (PPVV), ground peak particle velocity (GPPV), and the peak dynamic strain of the pipe were highly positively correlated, which verifies the feasibility of using GPPV to characterize pipeline vibration and strain level. According to the failure criteria and relevant codes, combined with the analysis of experimental results, the safety threshold of additional circumferential stress on the pipeline is 1.52 MPa, and the safety control vibration speed of the ground surface is 21.6 cm/s.

Dynamic response and safety analysis of polyethylene pipeline under rockfall conditions

AbstractThe safety of buried gas pipelines in mountainous cities is at risk due to potential hazards such as landslides and rock falls. To ensure the safety of pipelines, this paper develops a three‐dimensional dynamic response model to reveal the impact of rockfall radius, rockfall impact velocity, and pipe burial depth on the dynamic response of buried polyethylene pipelines (PE pipelines) under rockfall conditions. Subsequently, an orthogonal experimental design and analysis of variance (ANOVA) are performed to identify critical factors. Ultimately, a multi‐factor limit state equation is constructed to assess the safety of PE pipelines accordingly failure prevention actions for buried gas pipelines under the impact of rockfall is specified. Overall, this proposed method contributes to safety analysis of buried PE pipelines in rockfall‐prone areas.

Natural aging mechanism of buried polyethylene pipelines during long-term service

Currently, accelerated aging tests are widely used to study the aging process of polyethylene pipelines. However, this approach can only simulate one or several main influencing factors in the natural environment, which are often quite different from the actual environment of the buried pipelines. In this study, five types of PE80 buried pipelines in service for 9–18 years were taken as the research object, while new PE80 pipelines were taken as the reference group. The aging process and mechanism of polyethylene buried pipelines were studied through mechanical and chemical property tests and microstructural analysis. The results showed that the pipeline exhibited cross-linking as the main aging mechanism after being in service for 0–18 years. The aging degree and law of the inner and outer surface of the pipeline were compared, and the observed mechanism of both surfaces was explained. After 18 years in service, the elongation at the break of the pipe decreased by 16.2%, and the toughness of the matrix in the main collapse area of the tensile sample was the fundamental reason responsible for changes in the mechanical properties. Finally, after 18 years in service, the oxidation induction time of the pipeline was 25.7 min, which was 28.5% higher than the national standard value. There were no potential safety hazards during continuous long-term service. The results of this paper provide reference data and theoretical guidance for the aging process study of buried polyethylene pipelines.

Study on X-ray testing of buried polyethylene pipeline thermal fusion welding

Thermal fusion welding is a common method for high-density polyethylene (HDPE) pipelines. However, defects are easy to occur at the joints in the welding process, causing hidden danger. In this study, HDPE pipes with thermal fusion welding defects were made and the X-ray technology was used for detection. The results show that the testing effects of different defects are quite different. The X-ray cannot detect cold-welding defects. The weld seam of the over-welding in the negative is narrowed. Besides, the unfilled holes collapse during welding, resulting in poor detection results. The filled holes can be detected.

Dynamic performance prediction and influencing factors analysis of buried polyethylene pipelines under subsurface localized explosion

Although polyethylene (PE) pipelines have been extensively used in engineering fields, very little effort has been devoted to their abilities against blast loads. In the present study, numerical method is used to predict the dynamic performance of buried small-diameter PE pipelines under subsurface localized explosion. The effectiveness of a numerical model was firstly evaluated to entirely replicate the experimental damage process of PE pipelines. Then, parametric studies are performed to show the dynamic response of PE pipelines under subsurface localized explosion. Finally, the main influencing factors are analyzed according to the grey system theory. The results show that the front and back faces, top and bottom of the pipelines, where facing explosive charge are the main failure positions of PE pipelines due to the local effect of blast load. The peak pressure, resultant displacement, peak effective strains, and peak vibration velocities of the PE pipelines increase with the explosive mass increasing. The peak pressures and peak vibration velocities decrease with the pipe size decreasing. Reducing the pipe size could increase the maximum effective strain of the pipe facing the explosive center, and reduce the vibration velocity of the pipe near the explosive center. The change law of peak pressure of PE pipelines caused by changing explosive mass and pipe size is different from that of peak vibration velocity of PE pipelines. As a sequence, the three influencing factors (explosive mass, pipe size and blasting distance) should also be considered to analyze the influence of subsurface explosion on the buried small-diameter PE pipelines.

Numerical Simulation of Pipeline-Pavement Damage Caused by Explosion of Leakage Gas in Buried PE Pipelines

In order to investigate the damage influence of the leakage explosion in urban gas pipeline on the surrounding environment, the numerical models of buried PE (polyethylene) pipes under urban pavement were established by using ANSYS/LS-DYNA in this study. The reliability of the numerical models was verified on the basis of the explosion experiments. According to the amount of gas leakage, the TNT explosive equivalent was determined. The gas leakage explosion process of buried PE pipes was studied, and the pressure and stress changes of pipes and pavements under different explosive equivalents and buried depths were analyzed; at last, the deformation law of pipes and pavements were discussed. The results show that the PE pipes are fractured during the leakage explosion and a spherical explosion cavity is formed in the soil. The pavement above the explosion point bulges upward and forms a circle. The maximum pressure of pipe near the explosion point increases linearly with the increase of explosive equivalent, and a proportional relation is observed between the fracture width of pipe and the explosive equivalent. The degree and duration of pavement deformation increase significantly with the increase of explosive equivalents. The dynamic response of the pipes is rarely affected by the buried depth, and the change of maximum effective stress is no more than 7%. However, the buried depth is of great influence on the damage degree of pavement. When the buried depth increases from 0.9 m to 1.5 m, the pavement deformation can be reduced effectively. The variation rule of pavement deformation is similar to the change rule of maximum overpressure and effective plastic stress; they change in the form of concave functions with the increase of buried depth. The results can provide theoretical basis for municipal pipeline construction design and urban safety planning and provide references for the risk assessment of gas explosion in buried pipelines.

Seismic vulnerability analysis of buried polyethylene pipeline based on finite element method

Lifeline engineering plays an important role in the development of human society and economy. A large number of seismic damage events show that the buried polyethylene pipeline is easy to be damaged under the earthquake action, however, the research on the seismic vulnerability of the buried polyethylene pipeline is still lacking. In this paper, the seismic vulnerability of buried polyethylene pipeline is studied based on the finite element method (FEM). The FE model and vulnerability analysis model are established. The establishment of the FE model mainly considers different site categories, soils damping that calculated by the Rayleigh damping theory and the wave pattern and input mode of seismic wave. At the same time, the grid sensitivity analysis and model verification are carried out. The vulnerability model includes the seismic demand model and the seismic capacity model. Based on the previous research, the damage state of the polyethylene pipeline is defined, and the sample combination of pipeline and seismic wave is considered to calculate the vulnerability curve of the pipeline. In all, this study provides a useful idea for the rapid evaluation of the seismic performance of buried polyethylene pipes.

Mechanical response of buried polyethylene pipeline beneath the roadway and its influential factors

To investigate the 2D mechanical response of flexible buried pipelines beneath roadway under static loads, taken high-density polyethylene (PE) as an object, ANSYS finite element commercial software is employed to construct pipe-soil interacting coupled model. The influence of burial depth, the diameter of the pipe, and modulus of backfilled earth on the deformation of the pipe are studied with the newly developed model. These results indicate that: (1) the maximum vertical displacement and Von Mises stress appear at the top of pipe and side of the internal surface of the pipe, respectively; (2) even if burial depth does not have a significant effect on mechanical characteristics of pipe, there is optimal burial depth; (3) the higher the diameter of conduits, the larger modulus backfilled earth, the more difficult it is to destroy pipe breaks.

Mechanical Response of Buried Polyethylene Pipeline Beneath the Roadway and Its Influential Factors

In order to investigate the 2D mechanical response of flexible buried pipeline beneath roadway under static loads, taken high density polyethylene as object, ANSYS finite element commercial software is employed to construct pipe-soil interacting coupled model. By means of newly developed model, the influence of burial depth, diameter of pipe and modulus of backfilled earth on deformation and mechanical characteristics of pipe is studied. Furthermore the viscoelastic properties of tubular product are considered to simulate creep deformation of pipe under constant loading. These results indicate that: (1) the maximum vertical displacement and Von Mises stress appear at top of pipe and side of internal surface of pipe, respectively; (2) the viscoelastic properties significantly improve the safety of pipe; (3) even if burial depth does not have significant effect on mechanical characteristics of pipe, there is optimal burial depth; (4) the greater the diameter of conduits, the larger modulus backfilled earth, the more difficult it is to destroy pipe breaks.

Strength Analysis of Buried Polyethylene Pipeline Under Ground Subsidence Considering Multivariate Influence

Abstract Due to the combined effects of natural and human factors, the ground subsidence is aggravated, which brings potential hazards to the normal operation of buried polyethylene (PE) pipelines. A variety of variables influences the safety of buried pipelines, while the existing research lacks detailed analysis on the issue. A finite element model of buried PE pipeline was developed to analyze how various factors affected the strength of PE pipeline under ground subsidence. Furthermore, the orthogonal test combined with the gray correlation degree was used to analyze the significance of each influencing factor. The results show that (1) the strain rate of the pipe is different at different ground subsidence rates, and the maximum equivalent stress of the pipe increases with the increase of the strain rate; (2) the maximum equivalent stress diminishes with the increasing wall thickness of the pipeline and the length of the transition section; and (3) the factor that has the most significant influence on the maximum equivalent stress of the pipeline is the settlement, followed by the strain rate and the length of the transition section. The internal pressure has the least influence on the maximum equivalent stress in the context of ground subsidence induced stresses.

Investigating peak stresses in fitting and repair patches of buried polyethylene gas pipes

Nowadays, polyethylene composes a large number of natural gas distribution pipelines installed under the ground. The focus of the present contribution is two fold. One of the objectives is to investigate the applicability of polyethylene fittings in joining polyethylene gas pipes which are electrofused onto the pipe ends and buried under the ground, by estimating stress distribution using finite element method. The second objective is to study the effectiveness of polyethylene repair patches which are used to mend the defected pipelines by performing a finite element analysis to calculate peak stress values. Buried polyethylene pipelines in the natural gas industry, can be imposed by sever loadings including the soil-structure interaction, traffic load, soil’s column weight, internal pressure, and thermal loads resulting from daily and/or seasonal temperature changes. Additionally, due to the application of pipe joints, and repair patches local stresses superimposed on the aforementioned loading effects. The pipe is assumed to be made of PE80 resin and its jointing socket, and the repair patch is PE100 material. The computational analysis of stresses and the computer simulations are performed using ANSYS commercial software. According to the results, the peak stress values take place in the middle of the fitting and at its internal surface. The maximum stress values in fitting and pipe are below the allowable stresses which shows the proper use of introduced fitting is applicable even in hot climate areas of Ahvaz, Iran. Although the buried pipe is imposed to the maximum values of stresses, the PE100 socket is more sensitive to a temperature drop. Furthermore, all four studied patch arrangements show significant reinforcing effects on the defected section of the buried PE gas pipe to transfer applied loads. Meanwhile, the defected buried medium density polyethylene gas pipe and its saddle fused patch can resist the imposed mechanical and thermal loads of 22°C temperature increase. Moreover, increasing the saddle fusion patch length to 12 inches reduces the maximum stress values in the pipe, significantly.

Reliability analysis of buried polyethylene pipeline subject to traffic loads

Due to the increasing number of vehicles in urban areas and the degradation of pavement performance, the failure rate of polyethylene pipeline, across roads, has increased rapidly. Based on relevant data, the traffic loads are regarded as a random variable; also its distribution is determined. First, the nonlinear contact interaction model was established, among traffic loads, soil and buried polyethylene pipeline, using finite element analysis software. Second, considering the decline of the pavement performance, the mechanical characteristics of buried gas pipeline suffering from different traffic loads were analyzed. Based on statistics of vehicle load, the distribution law of its maximum equivalent stress was determined by numerical simulation. Particularly, the strength distribution law of polyethylene pipeline was obtained through experiments. The reliability index of polyethylene pipeline was calculated using central point method and Monte Carlo method. Finally, based on the degradation curve of pavement performance, the remaining life of buried polyethylene pipeline was assessed.

Monitoring the Dynamic Response of a Buried Polyethylene Pipe to a Blast Wave: An Experimental Study

Although the use of polyethylene (PE) pipelines has become increasingly widespread in recent years, few studies have addressed their seismic design and ability to withstand blast waves. In order to establish their seismic capacity, the dynamic response of buried pipelines subjected to blast waves must be explored in depth. Here, we studied the dynamic response of PE pipes situated near an explosive source. Time histories of dynamic strains were measured by conventional strain gauges after simple waterproof treatment, and pipe and ground vibration velocity curves were obtained. Based on the experimental data, the attenuation law of the peak strains under the conditions of different charge masses and blast center distances was analyzed, and the spectrum characteristics of strain, velocity of the pipe, and ground velocity were studied. The results revealed that a large hoop strain on the PE pipes was produced due to the local impact near the explosive source. We found that peak hoop strain (PHS) or peak axial strain (PAS) had a power attenuation relationship with the scaled distance, and this relationship could also be derived by dimensional analysis. The average frequency of strains had the same attenuation form as the charge mass, which was between 10 Hz and 50 Hz. Additionally, the vibration of the pipe showed a low frequency. We also determined that the attenuation of the average frequency of pipe and ground vibration velocity was closely related to the charge mass and the scaled distance. Pipe peak vibration velocity (PPVV), ground peak particle velocity (GPPV), and the peak dynamic strain of pipe were highly positively correlated, which verifies the feasibility of using GPPV to characterize pipeline vibration and strain level. Thus, a blasting criterion of 10% minimum request strength (MRS) for PE pipe was proposed, which means that the additional PHS or PAS of the dangerous point must be less than 10% MRS, and we also propose limiting the safety distance–charge mass for blasts near buried PE pipelines by the criterion. Some results in this paper can serve as the basis for future in-depth theoretical research.

Mechanical Analysis of Buried Polyethylene Pipelines under Ground Overload

Polyethylene (PE) pipelines are widely used in natural gas transmission systems in urban areas. With the acceleration of urbanization, the scale of PE natural gas pipelines has expanded rapidly. Thus, urban gas pipeline accidents caused by ground overload are inevitable. In this paper, the mechanical behavior of PE pipeline subjected to ground overload was investigated by the finite element method. PE pipe and soil were all established into a three-dimensional finite element model by using continuous solid elements. And parametric analysis was conducted to discuss the effects of pressure parameters, pipeline parameters and soil parameters on PE pipe’s mechanical response. The numerical simulation results indicated that the main failure form of buried PE pipe subjected to ground overload is ovalization deformation. With the increase in ground load, the ovalization deformation of the pipeline increases gradually and the maximum stress point of the pipe is transferred from the top (bottom) of the pipe to the midsection of the pipe. The buried depth of pipe, the wall thickness of pipe, internal pressure and backfill type play a great role. Within a reasonable range, it will be safer if the pipe has greater wall thickness, buried depth and internal pressure. Meanwhile, the high soil’s elasticity modulus and Poisson ratio backfill type are more conducive to the safety of buried PE pipelines.

Mechanical response of buried polyethylene pipelines under excavation load during pavement construction

Abstract Polyethylene (PE) pipelines are the most popular kinds of urban gas pipelines used in industry. With rapid development of urban pavement construction and increasing demand of natural gas in China. Urban gas pipe accidents caused by pavement mechanical construction have taken place more frequently in recent years, which becomes one main reason for accidents caused by third party damage. Thus, it is of great importance to investigate the failure mechanism of urban pipeline under mechanical excavation for safe operation of urban gas pipelines. A rigorous 3D finite element model was established for mechanical response of PE pipe under mechanical excavation in this study. Soil, tooth of the mechanical excavator and pipe were all modelled by continuum solid elements. Surface to surface contact algorithm was utilized simulating the actual interaction between excavation tooth, pipe and soil. Failure procedure of PE pipeline under excavation load was investigated in detail in a baseline analysis based on two commonly adopted criteria, the stress based failure criterion and the strain based criterion. Parametric analysis was also conducted to discuss the effects of excavation position, pipe diameter, pipe wall thickness and internal pressure on PE pipe's mechanical response. Results show that, large stress and strain will occur at longitudinal ends of the dent in the pipe induced by excavation load. And large ovality will occur in the whole contact area of the pipe. The strain based criteria is more suitable for safety assessment of PE pipe, as the outstanding plastic performance of PE material. The excavation position and internal pressure have little influence on pipe's response, while increasing the pipe diameter and wall thickness can decrease the pipe stress and ovality to a certain extent.

Evaluation of durability of buried polyethylene pipelines and tanks with a cellular wall

Evaluation of durability of buried polyethylene pipelines and tanks with a cellular wall