Underground Gas Pipes Research Articles

Safety Evaluation of Underground Gas Pipe under Blasting of Subway Connected Aisle: A Case Study

How to ensure the underground gas pipe's safety under blasting construction of subway connected aisles is a key problem in tunnel construction. Based on the blasting excavation project of Wuhan Rail Transit Line 8 phase II, the numerical model whose reliability is verified by field monitoring data is established by ANSYS/LS-DYNA to analyze the dynamic underground gas pipe's dynamic characteristics under blasting excavation of the connected aisle. According to the piping design code, the allowable effective stress control standard of underground pipe is proposed to evaluate the underground pipe's safety under the blasting. The results show that: with the advance of blasting excavation, the position of the most dangerous section will change constantly and the pipe's peak particle velocity (PPV) will appear an obvious amplification phenomenon in both sides of metro tunnels. The pipe's PPV is greater than the ground surface's PPV. A mathematical model is established to predict the pipeline's PPV based on the linear relationship between the pipeline and the ground surface. According to the correlation between PPV and von-Mises stress of gas pipeline, a mathematical model between the pipe's von-Mises stress and distance is established to predict the pipeline's safety, which can provide guidance for actual blasting engineering.

Detection of Underground Anomalies Using Analysis of Ground Penetrating Radar Attribute

Need of specifying underground construction works for supporting further tasks as maintenance, repairing, or setting up new underground structures. For these needs, ground penetrating radar, one of the efficient geophysical methods, can bring high-resolution and quick underground image revealing existence of both natural and artificial anomalies. Its fixed receiver-transmitter antennas setting as constant offset is commonly used in urban areas. Conventionally, hyperbolae events are crucial indicator for scattering objects as kinds of pipes, water drainage system, and concrete building structures as well as sink holes. Calculation of their depths and sizes requires migration analysis with the environment velocity. Migrated sections with different velocity show different chaos degrees of transformation from a hyperbola diffraction curve to its focused area. We have researched diagrams of different Ground Penetrating Radar attributes as energy, entropy, and varimax dependent on two variables, velocity and window zone covering diffraction events from a set of synthetic data and real data, in specifying the environment velocity. We have developed a novel technique for evaluation of the ground velocity and object’s size by combination of the new varimax diagram and the Kirchhoff migration method. The technique can define contribution of diffracted ground penetrating radar waves for building the diagram after removing the reflection contribution. The synthetic datasets consist of different random background noise levels and expressions of different-sized circular and rectangular pipes. The real data is measured for detecting two underground gas pipes in Ba Ria – Vung Tau province, Vietnam.

Experimental and numerical investigations on predictor equations for determining parameters of blasting-vibration on underground gas pipe networks

As underground gas pipe plays a major role for the onshore and offshore gas transportation system, maintaining record levels built up year by year. However, once a rupture happened during aging underground gas transport process, the consequence of gas blasting incident would pose a deadly threat in the vicinity of accidental location. Ground vibration induced by underground gas pipe blasts is one of the most significant effects that can make a serious impact on surrounding environment and integrated facilities. Based on this, this study performed a combined full-scale experiment and numerical investigations on effects of ground vibration from gas pipe blasting. Dynamic characteristics Peak Particle Velocity (PPV), Peak Ground Acceleration (PGA), Dominant Frequency (DF) of blasting ground vibration concerning the safety of gas transport process were analyzed. Blast-induced displacements with parallel pipe was simulated using LS-DYNA and a series of numerical data were collected for comparison. Modified predictor equations for determining different parameters on behavior of blasting ground vibration with certain distance were proposed based by comparative data. The primarily purpose of this study is to bring a new perspective to better prediction the dynamic characteristics governing ground vibration of the underground gas pipe fails to blast in gas transport process.

Experimental study of methane diffusion in soil for an underground gas pipe leak

Pipeline leaks can cause large economic losses as well as environmental hazards such as fires and explosions. A full-scale experimental system was developed to simulate low pressure gas leaks from small holes in four different directions from a pipe buried in soil. The methane concentration variations in the soil were measured during the release phase and after the dissipation phase for various mass flow rates and leak directions. The results show that the larger mass flow rate required less time to reach saturation and had larger concentrations at the end of the release phase. The locations near the soil surface had the fastest gas concentration growth rates and shortest times to reach steady state, while the locations below the pipe had slower grow rates but larger concentrations at the end of the release phase. The leak direction significantly influences the concentration distribution above the pipe, while the concentrations below the pipe differ only for upward flow.

2A2-P03 空気圧駆動式イモムシ型管内走行ロボットの走行実験(特殊移動ロボット(2))

This paper describes the suggestion of in-pipe mobile robot can inspect pipe inside without excavation underground gas pipe and so on. Manufacture the green caterpillar type in-pipe mobile robot using suction brake for correspond to various the pipes inner diameter. This robot used pneumatic actuator which is advantageous in powor-weight ratio. This robot imitate structure of abdominal prolegs and movement of the somites of the green caterpillar. The inspection by in-pipe mobile robot is necessary to reciprocate the inspection section to a robot runs by oneself. The inspection is needed to runs not only straight pipe but also right angle pipe and pipe such as a three-forked road. So I executed motion experiment in laying pipes form of various. Paper report this experiment results.

가스관 굴착사고 예방을 위한 RFID 인식기술의 적용성 연구

According to the last 5 year statistics of KGS, there occurred 22 under ground gas pipe accidents per year in Korea. And about 5 accidents per year were caused from the third party digging. IT recognition technique could reduce such underground gas accidents. Among IT recognition technique, RFID is most poplar. In the air, RFID were applied to various fields including the distribution industry, but underground condition, the research and application cases of RFID were little This research was undertaken to see the applicability of RFID to underground gas pipe safety. By use of 900 MHz RFID reader and commercial metal tag, the stable recognition distance was measured in the similar underground condition of LNG pipe. Stable recognition depth of RFID tag were measured to be 50, 45, 25 cm in the medium of soil, 5 cm-thick-concrete+soil, and water respectively. The measured distances were considered to be the meaningful distance to prevent the gas pipe accidents Also the efficient ways to input the required gas pipe data to the 24 byte metal tag were proposed. Application of RFID to underground LNG supply system will not only reduce the gas accidents due to third party digging but also improve the gas line maintenance efficiency.

Flaw detection of underground pipeline using electrical potential method

This paper presents a modeling approach to characterize adjacent cracks on underground gas pipe. Electrical potential method is used for capturing signals from surface cracks on the gas pipe. A three dimensional potential problem is considered for the inspection model. A defect parameter-to-output mapping is represented by means of finite element method in three dimensions. Computational methods for sizing and positioning of cracks are proposed based on our modeling approach.

Techniques for Methane Gas Leak Detection Using a Near-Infrared Diode Laser

In recent years, a requirement has emerged for cost-effective techniques for the detection of leaks of methane gas, the principle ingredient of natural gas. To realize such techniques, laser absorption spectroscopy at the absorption line of methane has been intensively researched. The author has developed two types of equipment for methane gas leak detection using a compact and low-cost near-infrared diode laser (InGaAsP DFB laser,λ=1.65372μm). One system can survey the leaks in underground gas pipes while driving along the roadabove the pipes. The other can provide remote detection and pinpointing of the leaks in exposed gas pipes. To accomplish highly sensitive detection, despite weak absorption in near-infrared range, these two equipments employ second-harmonic detection of wavelength modulation spectroscopy.

磁気センサを用いたドリル先端位置検知精度の改善

Precise measurement of drill head position is required to avoid the collision between the drill head and underground facilities, when a horizontal drilling machine is used for constructing underground gas pipes in the city. A positioning technique without special devices on the ground surface has been expected especially beneath the waterway or heavy traffic road, because it is difficult to conduct the measurement for locating the drill head position on the ground surface.The authors have studied both magnetic and pitch sensors installed inside the drilling tool for locating drill head position, and we have found that alignment of two sets of magnetic sensors is effective to reduce noise in the city which disturbs the natural magnetic field. We have confirmed that the sensors can keep the drill head position with a precision less than 10 cm, when the drill head progresses 12 m along the drill hole. Engineers and workers do not have to walk around just above the underground drilling site to locate the drill head position by using the sensors.

P-1-66 - Peculiarities of clinical presentation, diagnosis and surgical treatment of arteriovenous malformations (AVM) in the acute stage of intracranial hemorrhage

The paper describes the results of theoretical and experimental investigation of environmental low-frequency noise and vibration. The main aim of this investigation was to examine the popular belief that this noise is being generated by underground gas pipes. The theoretical hypothesis has been developed which shows that under certain circumstances underground gas pipes may be in fact one of the sources of low-frequency noise. According to this hypothesis, underground pipes are able to effectively generate Rayleigh surface waves in the ground. Then, propagating to the buildings, these waves can result in generating structure-borne noise in buildings. The experimental investigations of the low-frequency noise and vibration were carried out in several locations throughout the East Midlands (UK) and included high resolution measurements of noise and vibration spectra. Records were taken inside and outside the houses, as well as near buried gas distribution lines. In 50% of cases the low-frequency noise complained of has been detected. However, the presence of ground vibrations was not observed in any location. Thus, at least during this series of experiments, there was no evidence of underground gas pipes being a source of low-frequency noise. The measured characteristics of the air-borne noise show that as a rule its level is below the average threshold of human sensitivity. Thus, only exceptionally sensitive people can be affected. Nevertheless, even though the number of people sensitive to low-frequency noise is relatively small, the technical and legal aspects of this problem deserve further consideration.

Investigation of environmental low-frequency noise

The paper describes the results of theoretical and experimental investigation of environmental low-frequency noise and vibration. The main aim of this investigation was to examine the popular belief that this noise is being generated by underground gas pipes. The theoretical hypothesis has been developed which shows that under certain circumstances underground gas pipes may be in fact one of the sources of low-frequency noise. According to this hypothesis, underground pipes are able to effectively generate Rayleigh surface waves in the ground. Then, propagating to the buildings, these waves can result in generating structure-borne noise in buildings. The experimental investigations of the low-frequency noise and vibration were carried out in several locations throughout the East Midlands (UK) and included high resolution measurements of noise and vibration spectra. Records were taken inside and outside the houses, as well as near buried gas distribution lines. In 50% of cases the low-frequency noise complained of has been detected. However, the presence of ground vibrations was not observed in any location. Thus, at least during this series of experiments, there was no evidence of underground gas pipes being a source of low-frequency noise. The measured characteristics of the air-borne noise show that as a rule its level is below the average threshold of human sensitivity. Thus, only exceptionally sensitive people can be affected. Nevertheless, even though the number of people sensitive to low-frequency noise is relatively small, the technical and legal aspects of this problem deserve further consideration.

Generation of Low-Frequency Ground Vibrations by Sound Waves Propagating in Underground Gas Pipes

The hypothesis is examined about sources of disturbing low-frequency hums arising from buried gas or petrol pipes in which turbulent flows of gas or liquid generate sound waves of high amplitude propagating in pipe-lines as in waveguides. Theoretical investigation of this problem shows that if the velocities of sound inside the pipes (450 m/s for methane) are higher than the velocities of Rayleigh surface waves in the ground (typically 300–600 m/s) then ground Rayleigh waves are effectively generated by sound waves propagating inside the pipes, the mechanism of generation being similar to that of sonic boom from supersonic jets. The Rayleigh waves then propagate to buildings and cause building vibration and structure-borne noise. Central frequencies of generated Rayleigh wave spectra are in the range of 5–20 Hz and depend on pipe-depth. The amplitudes of ground vibration velocity may achieve 70 dB (relative to 10−9 m/s). This is quite enough to annoy some people both due to the direct impact of vibrations and to structure-borne noise. The results obtained may contribute to a fuller understanding of the nature of low-frequency hums.

Ground probing radar system

Two types of battery-powered, compact, ground probing radar (GPR) systems have been developed. The systems have CRT displays mounted on antenna units and are used to locate such underground objects as gas pipes, water pipes, and transmission cables. The performance of the systems and results of field tests are reported. The GPR detected 59 of 64 underground gas pipes; a 200-mm-diameter pipe is clearly detected at a depth of 2.3 m. >