• Journal of the Korean Institute of Gas
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• v.11 no.3
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• pp.49-55
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• 2007

Polyethylene pipes have been widely used as they are easy to construct and suitable for economical efficient when they are compared with metal pipelines. This paper studies the effect of various external loadings on stress and deflection of the buried PE pipes using Finite Element Method(FEM). For this purpose, stresses of buried PE pipes are calculated according to the loading condition such as pipe types (pipe diameter $50{\sim}400mm$), burial depths ($0.6{\sim}1.2m$) and internal pressures ($0.4{\sim}4bar$). As a result, it is founded the effect and relation with each of loading conditions under the buried condition.

• Journal of the Korean Institute of Gas
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• v.27 no.2
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• pp.1-6
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• 2023

PE piping, which has advantages in terms of construction convenience and economy, is widely used for underground burial in the domestic urban gas field. These PE pipes use squeeze-off in many sites to block gas flow during maintenance and repair work. Squeeze-off refers to a method of compressing a PE pipe to block fluid flow, and damage may occur due to the nature of construction in which the pipe is deformed by physical force. In order to prevent damage to PE pipes due to squeeze-off, the main points to be reflected in the squeeze-off operation procedures such as proper compression range, use pressure, and diameter were derived through damage assessment and confidential test according to the compression rate. The compression experiment for PE pipe damage assessment was conducted while changing the compression rate (20%~40%), the pressure of use (2.8 kPa, 25 kPa, 70 kPa), and the pipe diameters (63 mm, 90 mm, 110 mm). As a result of damage assessment according to the compression rate, damage occurred in pipes with compression rates of 45%(110mm) and 73%(63mm), which are for analyzing the effect of excessive compression. In addition, the leakage test was conducted using Ar(argon) during the squeeze-off, and as a result of the experiment, leakage occurred under the conditions of 70kPa and 110mm of pipe. As a result of this study, it was confirmed that squeeze-off for airtightness should be carried out in pipes within a range not exceeding 25 kPa and 90 mm pipes, and the appropriate compression rate to prevent damage to PE pipes is 30%.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.359_360
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• 2009

KEPCO signed up with LS CABLE as a contractor for HVDC submarine cable construction in February 2009. The desk research has been completed in may 2009. Also, Cable route and the protection method will be selected by November 2009. The tentative cable route between Jindo and Jeju which is consisted of sea farms and shipping route zone will reach almost 105km. The oceanographic survey for the selection of protection method will be carried out and the survey lists are consisted of MBES, SSS, CPT, ADSP. The protection methods such as burial, Concrete Mattress, UP Pipe, Rock Berm will be selected as per each condition of sea area after the oceanographic survey is completed. Kepco has developed variable methods based on the maintenance experience for HVDC submarine cable between HAENAM and JEJU. Based on the such a accumulated know-how, it can be expected for the confidence and stability of the 2nd HVC project to be improved.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.765-774
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• 2004

This paper presents a damage assesment method for buried pipelines subjected to Deep Excavation-induced ground movements. Ground deformation characteristics resulting from 3D finite element analysis was represented mathematically by a hyperbolic tangential function. A parametric study was performed on excavation depth and burial position of pipeline. The result of the parametric study indicate that length of hyperbolic tangential function affects the results of damage assessment. Using numerical studies for buried pipeline response to ground movements by relative flexibility of the pipe-soil system. The result of numerical studies are presented in forms of design charts which can be readily used for various condition encountered in practices.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.3
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• pp.146-159
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• 2016

This study used Navier-Stokes Solver(LES-WASS-2D) for analyzing hydrodynamic characteristics with high order in order to analyze self-burial mechanism of pipeline with spoiler under steady flow. For the validity and effectiveness of numerical model used, it was compared and analyzed with the experiment to show flow characteristics around the pipeline with and without the spoiler. And the hydraulic(flow, vortex, and pressure) and force characteristics were numerically analyzed around the pipeline according to the incident velocity, and shape and arrangement of spoiler. Primarily, if the spoiler is attached to the pipeline, the projected area is increased resulting in higher flow velocity toward the back and strong vortex caused by wake stream in the back. Secondly, the spoiler causes vertically asymmetric flow and vorticity fields and thus asymmetric pressure field. It increases the asymmetry of force on the pipe and thus develops large downward fluid force. Both of them are the causes of selfburying of the pipeline with spoiler.

• Journal of Korean Society of Water and Wastewater
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• v.10 no.1
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• pp.96-111
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• 1996

The failure of water pipelines is progressed by several compound factors and the collection and analysis of data about pipeline failure are inevitable for effective pipeline rehabilitation. Data analysis of pipeline failure was already performed in USA and Europe. Based on such phenomena, failure characteristics about metropolitan pipelines in Korea were analyzed: The conclusions of this study are as followings. 1. The failure cause of pipelines can be classified into natural cause and artificial cause. Artificial cause is 32% of total causes, so artificial failure as several constructions happens frequently in Korea. Although the failure by old pipe is greatest of any other causes m classtfied cause, failure cause is not classified in detail now. 2. The damaged part of pipelines is affected by cities, distribution system inventory, bedding conditions, and so on. In this study, the failure of pipeline body(67%) is greater than the failure of pipeline joint(33%) in natural failure. 3. In regard to pipe materials, failure rate of DCIP(0.8456), PEP(0.7288), and GSP(0.6643) is greater than that of CIP(0.3985) and CWSP(0.2348). 4. Usually, faIlure rate is increased in proportion to diameter of pipeline. In this study, CIP, DCIP, and CWSP have clear trends. But the trends of PEP is reverse, the case of GSP, HP is obscure due to data shortage. 5. There are no direct relationships between burial age and failure rate of pipelines. 6. Annual breaks and winter(Nov.~Feb.) breaks of pipelines are investigated. As a result, WInter breaks to annual breaks of CIP is 51.3%(Seoul), 51.1%(Taegu),38.7%(Pusan). This phenomena have direct correlation with average winter temp. of cities.

• Journal of Energy Engineering
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• v.17 no.4
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• pp.204-211
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• 2008

Polyethylene(PE) pipes have been widely used as they are easy to construct and suitable for economical efficient when they are compared with metal pipelines. This paper studied the effect of various external loadings on stress and deflection of the buried PE pipes using Finite Element Method(FEM). For this purpose, stresses of buried PE pipes were calculated according to the loading condition such as pipe types(pipe diameter $50{\sim}400mm$), burial depths($0.6{\sim}1.2m$) and internal pressures($0.4{\sim}4bar$). As a result, it was founded the effect and relation with each of loading conditions under the buried condition.

• Geomechanics and Engineering
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• v.9 no.6
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• pp.757-774
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• 2015

Reinforcing soils with the geosynthetics have been shown to be an effective method for improving the uplift capacity of granular soils. The pull-out resistance of the reinforcing elements is one of the most notable factors in increasing the uplift capacity. In this paper, a new reinforcing element including the elements (anchors) attached to the ordinary geogrid for increasing the pull-out resistance of the reinforcement, is used. Thus, the reinforcement consists of the geogrid and anchors with the cylindrical plastic elements attached to it, namely grid-anchors. A three-dimensional numerical study, employing the commercial finite difference software FLAC-3D, was performed to investigate the uplift capacity of the pipelines buried in sand reinforced with this system. The models were used to investigate the effect of the pipe diameter, burial depth, soil density, number of the reinforcement layers, width of the reinforcement layer, and the stiffness of geogrid and anchors on the uplift resistance of the sandy soils. The outcomes reveal that, due to a developed longer failure surface, inclusion of grid-anchor system in a soil deposit outstandingly increases the uplift capacity. Compared to the multilayer reinforcement, the single layer reinforcement was more effective in enhancing the uplift capacity. Moreover, the efficiency of the reinforcement layer inclusion for uplift resistance in loose sand is higher than dense sand. Besides, the efficiency of reinforcement layer inclusion for uplift resistance in lower embedment ratios is higher. In addition, by increasing the pipe diameter, the efficiency of the reinforcement layer inclusion will be lower. Results demonstrate that, for the pipes with an outer diameter of 50 mm, the grid-anchor system of reinforcing can increase the uplift capacity 2.18 times greater than that for an ordinary geogrid and 3.20 times greater than that for non-reinforced sand.

• Journal of the Korean Geosynthetics Society
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• v.12 no.1
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• pp.73-81
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• 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 GEO-environmental Society
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• v.19 no.7
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• pp.13-18
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• 2018

Recently, road subsidence has been increasing in urban areas, threatening the safety of citizens. In the lower part of the road, various road facilities such as water supply and drainage pipelines and telecommunication facilities are buried, and the deterioration of the facilities causes the road subsidence. In particular, in the case of old sewer pipes which are attracting attention as a main cause of road subsidence, the management of sewer pipe replacement, repair and reinforcement is being performed depending on the burial year. Therefore, in this study, we tried to suggest a reliable road subsidence risk assessment method considering various sewer specifications and surrounding environment information and CCTV exploration result and GPR exploration result.