• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.1148-1158
• /
• 2005

This work reports results of our study on the dynamic responses of the buried pipelines both along the axial and the transverse directions under various boundary end conditions. We have considered three cases, i.e., the free ends, the fixed ends, and the fixed-free ends. We have studied the seismic responses of the buried pipelines with the various boundary end conditions both along the axial and the transverse direction. We have considered three cases, i.e., the free ends, the fixed ends, and the fixed-free ends for the axial direction, and three more cases including the guided ends, the simply supported ends, and the supported-guided ends for the transverse direction. The buried pipelines are modeled as beams on elastic foundation while the seismic waves as a ground displacement in the form of a sinusoidal wave. The natural frequency and its mode, and the effect of parameters have been interpreted in terms of free vibration. The natural frequency varies most significantly by the soil stiffness and the length of the buried pipelines in the case of free vibration, which increases with increasing soil stiffness and decreases with increasing length of the buried pipeline. Such a behavior appears most prominently along the axial rather than the transverse direction of the buried pipelines. The resulting frequencies and the mode shapes obtained from the free vibration for the various boundary end conditions of the pipelines have been utilized to derive the mathematical formulae for the displacements and the strains along the axial direction, and the displacements and the bending strains along the transverse direction in case of the forced vibration. The negligibly small difference of 6.2% between our result and that of Ogawa et. al. (2001) for the axial strain with a one second period confirms the accuracy of our approach in this study.

• Journal of the Korean Geosynthetics Society
• /
• v.12 no.1
• /
• pp.73-81
• /
• 2013

The objective of this paper is to minimize installation length of pipeline and to reduce burial depth for construction by increasing the friction coefficient caused by the interface between backfill material and pipeline. And then, the sufficient friction coefficient shortens the length of expansion joint pipe and gives the life extension of expansion joint absorber for efficient procedure regarding maintenance and administration of construction. The backfill material which is developed in this study has larger and smaller friction angle than that of conventional backfill material (river sand). The backfill material with tire powder provides low friction angle at curved section when pipe diameter increases in size (38% reduction at pipe diameter in 900 mm). When using backfill material with river sand and fly-ash, the mixture mixed with 1.5% fly-ash has 30% and that with 3% fly-ash has 50% reduction effect for minimum installation length of expansion joint pipe.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.23 no.3
• /
• pp.263-269
• /
• 2003

Magnetic flux leakage (MFL) signals were used for corrosion inspection of buried oil and gas pipeline. 3D finite element analysis was used to examine the effects of far and near-side pit depth and tensile stress on MFL signals. Anisotropci materials were used, and the effects of simulated tensile stress on MFL were investigated. The axial and radial MFL signals depended on far and near-side single pit depth and on the bulk stress, but the circumferential MFL signal did not depend on them. The axial and radial MFL signals increased with increasing pit depth and the bulk stress, but the circumferential MFL signal was scarcely changed.

• The Journal of the Convergence on Culture Technology
• /
• v.10 no.2
• /
• pp.419-427
• /
• 2024

This study assessed the potential impact of gas leakage resulting from accidental damage to buried urban gas pipelines during perforating operation near subway construction sites. The risk of explosions due to ignition sources such as static electricity, arising from gas infiltrating the subway construction site through storm sewers and sewage pipes, was evaluated using the ALOHA program. The results of the threat zone calculation, which input various parameters of urban gas pipelines such as length, diameter, and pressure, indicated that the flammable area within the vapor cloud extended from 1.2 to 1.4 km (red zone), the blast area ranged from 0.8 to 1.0 km (yellow zone), and the jet fire extended from 45 to 61 m (red zone). This study demonstrates that within the flammable area of the vapor cloud, a specific combination of concentration and conditions can increase flammability. The blast area may experience explosions with a pressure of 1.0 psi, sufficient to break glass windows. In the event of a jet fire, high temperatures and intense radiant heat exposure lead to rapid fire propagation in densely populated areas, posing a high risk of casualties. The findings are presented in terms of the sphere of influence and threat zone ranges.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2009.05a
• /
• pp.260-266
• /
• 2009

Non-revenue water reduction(NRW) technologies are implemented to evaluate and manage leakages scientifically in water distribution systems under local governments. A development of quantitative leakage indicator by measuring minimum night flow, pressure control policy by installation of PRV(pressure reducing valve) and the establishment of leakage prevention schemes by residual life modeling of deteriorated water pipes are reviewed and studied. Estimation models of allowable leakage are developed by measuring and analyzing minimum night flow at residential and commercial area in Nonsan city, which is suggested from UK water industry and can improve an existing leakage indicator for the evaluation of non-revenue water. Also, pressure control method is applied and analyzed to Uti distribution area in Sacheon city in the operation aspect. As results, $466\;m^3/day$ of leakage can be reduced and it is expected that 113million won of annual cost can be saved. In the part of corrosion velocity and residual life assessment, non-linear prediction models of residual thickness are proposed by assessment of corrosion velocity based on exposure years, soil and water quality etc., since the deteriorated water pipe play a major role to increase leakage. It is expected that collection data and analyzing results can be applied effectively and positively to reduce non-revenue water by accumulating surveying data and verifying the results in the business field of water distribution systems under local governments.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.328-337
• /
• 2005

This work reports results of our study on the dynamic responses of the buried pipelines both along the axial and the transverse directions under various boundary end conditions. We have considered three cases, i.e., the free ends, the fixed ends, and the fixed-free ends for the axial direction, and three more cases including the guided ends, the simply supported ends, and the supported-guided ends for the transverse direction. In order to investigate the effect of the boundary end conditions for the dynamic responses of the buried pipeline, we have devised a computer program to find the solutions of the formulae on the dynamic responses (displacements, axial strains, and bending strains) under the various boundary end conditions considered in this study. The dynamic behavior of the buried pipelines for the forced vibration is found to exhibit two different forms, a transient response and a steady state response, depending on the time before and after the transfer of a seismic wave on the end of the buried pipeline. The former is identified by a slight change in its behavior before the sinusoidal-shaped seismic wave travels along the whole length of the pipeline whereas the latter by the complete form of a sinusoidal wave when the wave travels throughout the pipeline. The transient response becomes insignificant as the wave speed increases. We have observed a resonance when the mode wavelength matches the wavelength of the seismic wave, where the mode number(k) of resonance for the axial direction is found to be $\overline{\omega}/{\pi}V+1/2$ for the fixed-free ends, $\overline{\omega}/{\pi}V+1$ for the free ends, and $\overline{\omega}/{\pi}V$ for the fixed ends, respectively. By adding 10 more modes to the mode number(k) of resonance, we were able to study all the dynamic responses of the buried pipeline for the axial direction. On the other hand, we have not been able to observe a resonance in the analysis for the transverse direction, because the dynamic responses are found to vanish after the seventh mode. From the results of the dynamic responses at the many points of the pipeline, we have found that the responses appeared to be dependent critically on the boundary end conditions. Such effects are found to be most prominent especially for the maximum values of the displacement and the strain and its position.

• Fire Science and Engineering
• /
• v.18 no.1
• /
• pp.54-66
• /
• 2004

In this article, we are to suggest the hazard-assessing method for the underground pipelines, and find out the pipeline-maintenance schemes of high efficiency in cost. Three kinds of methods are applied in order to refer to the approaching methods of listing the hazards for the underground pipelines: the first is RBI(Risk Based Inspection), which firstly assess the effect of the neighboring population, the dimension, thickness of pipe, and working time. It enables us to estimate quantitatively the risk exposure. The second is the scoring system which is based on the environmental factors of the buried pipelines. Last we quantify the frequency of the releases using the present THOMAS' theory. In this work, as a result of assessing the hazard of it using SPC scheme, the hazard score related to how the gas pipelines erodes indicate the numbers from 30 to 70, which means that the assessing criteria define well the relative hazards of actual pipelines. Therefore. even if one pipeline region is relatively low score, it can have the high frequency of leakage due to its longer length. The acceptable limit of the release frequency of pipeline shows 2.50E-2 to 1.00E-l/yr, from which we must take the appropriate actions to have the consequence to be less than the acceptable region. The prediction of total frequency using regression analysis shows the limit operating time of pipeline is the range of 11 to 13 years, which is well consistent with that of the actual pipeline. Concludingly, the hazard-listing scheme suggested in this research will be very effectively applied to maintaining the underground pipelines.

• Journal of Korean Society of Forest Science
• /
• v.76 no.2
• /
• pp.161-168
• /
• 1987

Forest road (10 Km) constructed for the demonstrational purpose by Forest Work Training Center (F.T.C.) in 1984 was partly damaged through the roadside landside and ditch erosion by the typhoon in 1986. The causes were investigated to apply for protecting against the damage of mountain forest road. The damaging length caused by roadside landside is around 3% out of total length of 10 Km forest road, and mostly coming from the curve road filled up more than 10 m slope length on the concave mountain slope, partly from the foot of fillslope along the ever-following valley and from the both side of fillslope under the outlet of culvert with ever-flowing water. In case of ditch erosion, the big damage at V-type ditch is coming from the overflow of valley water flowing down along the inside slope. Other problem is also showing in the steepness of longitudial gradient, which is felt as a problem in road to be constructed under more than 10 persent of gradient. Other cause of ditch erosion is coming from the bury of sand basin (water collecting wall) by the debris in small diameter culvert zone, namely less than 400mm, in diameter and by the soil mass slumped down from steep wall slope. From above results the causes of F.T.C. model road damage is showing to come from no-following the general guide or little experience to protect against the forest road damage. When improved above mentioned mistakes, F.T.C. Method of mountain forest road type could be developed as a model of Mountain forest road.