Narrow Results

The geological environment along a buried pipeline in permafrost regions is complex, where differential frost heave often occurs. To understand the changes in the stress behavior of pipeline structures caused by corrosion while laying them in permafrost regions, we established a thermo-mechanical coupling model of buried pipeline with corrosion defects by using finite element software. Numerical simulation analysis of buried pipeline was conducted. The effects of the frost heave length, the length of the transition section, the corrosion depth, and the corrosion length on the stress displacement were obtained. These analyses showed that the stresses and displacements of the pipeline with corrosion defects in permafrost regions can be simulated by using the finite element software numerical simulation method. Afterward, the corrosion resistances of pipelines with different corrosion lengths and depths were investigated via an electrochemical testing method. These results can provide some useful insights into the possible mechanical state of buried pipeline with regard to their design and construction, as well as some useful theoretical references for simulating real-time monitoring and safety analysis for their operation in permafrost regions.

The interaction between underground pipelines and soils is crucial to the design and maintenance of underground pipeline network systems. In this paper, the dynamic stiffness matrix in the frequency-domain of the buried pipeline is obtained by the improved scaled boundary finite element method (SBFEM) coupled with the finite element method (FEM) at the interface between the far and near fields. A new coordinate transformation together with a scaled line is introduced in the improved SBFEM. Combined with the mixed variable algorithm, the time-domain solution of the buried pipeline under dynamic loads is then obtained. The accuracy of the proposed algorithm was verified by numerical examples. A parametric study is performed to assess the influence of the anisotropic characteristics of the layered soils on the dynamic response of the pipeline, the result of which provides a reliable basis for engineering practice. The results show that these parameters have a significant impact on the pipeline. The understanding of this impact can contribute to the design, construction, and maintenance of the corresponding engineering projects.

In this study, a pipe-soil finite element analysis model was built using the shaking table test results of buried pipelines that were achieved through longitudinal multipoint excitation and multipoint excitation under different seismic intensities, so as to numerically simulate the seismic response of buried pipelines under longitudinal multipoint excitation and multipoint excitation under different seismic intensities. As indicated by the result of this study, the numerical calculations and the shaking table test findings in terms of long-distance oil and gas pipelines under longitudinal multipoint stimulation were well consistent, such that the validity of both sets of results was verified. The peak pipe stresses during the multipoint excitation under different seismic intensities declined by 13.8% to 30.9% compared with case 2 longitudinal multipoint stimulation. The acceleration of the pipe and the soil was reduced rapidly as the measuring point moved farther away from the pipe’s leftmost distance. The displacement variation of the oil and gas pipelines under longitudinal multipoint excitation suggested that the soil displacement was increased with the length of the monitoring point from the bottom of the soil box for different elevations of the same section. The soil displacement declined notably for the same stretch at the identical elevation with the reduction of seismic intensity. The findings of this study can lay a basis for in-depth research on the effect of multipoint stimulation with different seismic powers on the seismic response of underground pipes.

This paper is concerned with the spectral characteristics of leak noise at the source relevant to fluid dynamics for natural gas pipelines. Comparison is made between the flow field characteristics for the buried and above-ground pipelines to demonstrate the differences in aero-acoustics generation mechanism. The fundamental spectral parameters including the sound pressure level (SPL) and power spectral density (PSD), are extracted to characterize the leak noise under different pipeline conditions of operation pressure and leak orifice diameter. Numerical results show that the leak noise of buried pipelines has less energy and are more concentrated at lower frequencies, compared with that of above-ground pipelines. It is demonstrated that leak noise is predominantly governed by the dipole and the quadrupole sources, generated from the gas–solid interaction and turbulent disturbance, respectively. It is shown that the dipole source is attenuated and the quadrupole source is amplified with the leak orifice diameter for buried pipelines whereas both are amplified for above-ground pipelines. Moreover, it is suggested that the feature parameters of fluid dynamics, such as the average dynamic pressure and turbulent kinetic energy, can be used to characterize the leak noise mechanism for natural gas pipelines.

As time passes, the buried pipeline, under the influence of transport medium, soil and loading environment, especially metal pipelines are prone to corrosion phenomenon. This paper studies the buried pipeline as the object of the research, explores the impact of pipeline corrosion depth, corrosion width and corrosion location on the seismic performance of the pipeline. The purpose is to provide a theoretical reference for the safety and practicability of pipelines and provide guidance for continual use, maintenance or replacement and safe usage of pipelines. This paper presents the actual project as the background, and analyzes buried pipeline response based on different parameters by using the seismic response displacement method in the finite element software ANSYS.