• Journal of the Korean Institute of Gas
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• v.15 no.2
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• pp.27-32
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• 2011

In this paper a new defect length estimation algorithm using SQI(self quotient image) is presented for the MFL(magnetic flux leakage) inspection of underground gas pipelines. Gas pipelines are magnetized by the permanent magnets of the MFL PIG(pipeline inspection gauge) when the PIG runs through pipelines. If defects or corrosions exist in the pipeline, magnetic leakage flux is increased. The MFL signals measured by hall sensors are analyzed to estimate defect length using SQI. For 74 real defects carved in KOGAS pipeline simulation facility(KPSF) the accuracy of defect length estimation of the proposed algorithm was compared with that of conventional methods.

• Geomechanics and Engineering
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• v.20 no.1
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• pp.19-28
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• 2020

The spatial variability of geotechnical properties can lead to the uncertainty of settlement for frozen soil foundation around the oil pipeline, and it can affect the stability of permafrost foundation. In this paper, the elastic modulus, cohesion, angle of internal friction and poisson ratio are taken as four independent random fields. A stochastic analysis model for the uncertain settlement characteristic of frozen soil foundation around an oil pipeline is presented. The accuracy of the stochastic analysis model is verified by measured data. Considering the different combinations for the coefficient of variation and scale of fluctuation, the influences of spatial variability of geotechnical properties on uncertain settlement are estimated. The results show that the stochastic effects between elastic modulus, cohesion, angle of internal friction and poisson ratio are obviously different. The deformation parameters have a greater influence on stochastic settlement than the strength parameters. The overall variability of settlement reduces with the increase of horizontal scale of fluctuation and vertical scale of fluctuation. These results can improve our understanding of the influences of spatial variability of geotechnical properties on uncertain settlement and provide a theoretical basis for the reliability analysis of pipeline engineering in permafrost regions.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.40 no.2
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• pp.109-118
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• 2022

GPR (Ground Penetrating Radar), developed as a technology for geotechnical investigations such as sinkhole exploration, was used limitedly as a method to resolve undetectable lines in underground facility exploration. To improve the accuracy of underground facility data, the government made it possible to explore underground facilities using a non-metallic pipeline probe from July 2022. However, GPR has a problem in that the exploration rate is lowered in the soil with high moisture content, such as soft soil, such as clay layer, and there is a lot of variation in long-term accuracy. In this study, as a way to improve the accuracy of exploration considering the characteristics of GPR and the environment of underground facilities, we propose a GPR exploration method for underground facilities using permittivity constant correction and pattern analysis of GPR image data. Through this study, the accuracy of underground facility exploration and high reproducibility were derived as a result of field verification applying GPR frequency band and heterogeneous GPR.

• Journal of the Korean Society of Safety
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• v.21 no.1 s.73
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• pp.41-47
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• 2006

This paper introduces stress monitoring system for buried gas pipeline in poor ground. During the six months of improvement construction of poor ground, maximum settlement of gas pipeline is about 40 cm. This value represents relative small compared to the initial settlement estimation of ground improvement construction plan, 90 cm. Also, this paper includes the result of finite element analysis of gas pipeline to confirm safety of pipelines in poor ground. The stress monitoring system for gas pipeline was developed to guarantee the safety of buried gas pipeline in poor ground. Eventually, the ground improvement workings are ended safely and it is proved that the pipeline has no safety problem.

• Journal of the Korean Society for Environmental Technology
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• v.19 no.6
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• pp.576-585
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• 2018

Systematic management during the whole life cycle from construction to operation and maintenance is very important for the seven underground pipelines (waterworks, sewerage, electricity, telecommunications, gas, heating, oil including waterworks and sewerage). Especially, it is the construction process that affects the whole life cycle of underground buried pipeline. In order to construct a new city or to maintain different underground pipes, it is always necessary to dig the ground and carry out construction and related work. There is a possibility that secondary and tertiary breaks frequently occur in the pipeline construction process after the piping constructed first in this process. To solve this problem, a system is needed which can monitor damage in real time. However, the supply of electric power for continuous operation of the system is limited according to the environment of underground buried pipelines, so it is necessary to develop a stable electric power supply system using natural energy rather than existing electric power. In this study, we developed a system that can operate the pipeline monitoring system for long time (24 hours and 15 days) using natural energy using wind and solar light.

• Proceedings of the KIEE Conference
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• 2005.07e
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• pp.61-63
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• 2005

In present, most of underground metallic structures, especially gas pipeline, have adopted in order to protect against a corrosion. If a coating defect is be on the surface of gas pipeline, the pitting corrosion is occur normally. So, in the corrosion field, investigation of coating defect is very important activity. In this paper, DCVG(Direct Current Voltage Gradient) method which is can detect a coating defect of gas pipeline is introduced. And also, the assesment of coating defect position according to the position of temporary anode of ICCP(Impresed Current Cathodic Protection) system is presented.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.2
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• pp.74-79
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• 2002

We have been analyzed the interference problems already in steady state, especially AC corrosion when the gas pipeline is burred with power cable in the same submarine tunnel. In the next stage, we analyze the induced voltage in a fault condition of 154[kV] underground T/L. This paper presents the results of them which are limitation of safety voltage. meodeling of power cables, gas pipeline and grounding systems, analysis of induced voltage in a fault condition, and protection of Power line system.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1612-1614
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• 2007

The owner of underground metallic structures (gas pipeline, oil pipeline, water pipeline, etc) has a burden of responsibility for the corrosion protection in order to prevent big accidents like gas explosion, soil pollution, leakage and so on. So far, Cathodic Protection(CP) technology have been implemented for protection of underground systems. The stray current from DC subway system in Korea has affected the cathodic protection (CP) design of the buried pipelines adjacent to the railroads. In this aspect, KERI has developed a various mitigation method, drainage system through steel bar under the rail, a stray current gathering mesh system, insulation method between yard and main line, distributed ICCP(Impressed Current Cathodic System), High speed response rectifier, restrictive drainage system. We installed the mitigation system at the real field and test of its efficiency in Busan and Seoul, Korea. In this paper, the results of field test, especially, distributed ICCP system is described.

• Journal of the Korean Society of Safety
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• v.14 no.4
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• pp.71-77
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• 1999

Exposed gas pipeline in underground, especially subway construction site, has been continuously vibrated by vehicle above ground. Because this vibration can cause unexpected damages to pipeline, we had measured and analyzed the vibration. This paper presents results of the vibration analysis of exposed gas pipeline and the results are as follows. The major vertical vibration frequency of pipeline was about 13 Hz and the other frequency components disappeared when the vibration transmitted to I-beam and wire rope. Existence of wooden casement had not affect vibration of exposed gas pipeline. The results of modal analysis by experimental and analytical methods have good agreement and it is also shown that exposed pipeline has possibility of resonance at second mode.

• Smart Structures and Systems
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• v.30 no.5
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• pp.433-446
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• 2022

Despite efforts to reduce unexpected accidents at confined construction sites, choking accidents continue to occur. Because of the poorly ventilated atmosphere, particularly in long, confined underground spaces, workers are subject to dangerous working conditions despite the use of artificial ventilation. Moreover, the traditional monitoring methods of using portable gas detectors place safety inspectors in direct contact with hazardous conditions. In this study, a long-range (LoRa)-based wireless safety monitoring system that features the network organization, fault-tolerant, power management, and a graphical user interface (GUI) was developed for underground construction sites. The LoRa wireless data communication system was adopted to detect hazardous gases and oxygen deficiency within a confined underground space with adjustable communication range and low power consumption. Fault tolerance based on the mapping information of the entire wireless sensor network was particularly implemented to ensure the reliable operation of the monitoring system. Moreover, a sleep mode was implemented for the efficient power management. The GUI was also developed to control the entire safety-monitoring system and to manage the measured data. The developed safety-monitoring system was validated in an indoor testing and at two full-scale water pipeline construction sites.