• Journal of the Korean GEO-environmental Society
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• v.12 no.1
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• pp.13-26
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• 2011

Because the allowable current loading of buried electrical transmission cables is frequently limited by the maximum permissible temperature of the cable or of the surrounding ground, there is a need for cable backfill materials to be maintained at a low thermal resistivity during the service period. Temperatures greater than $50^{\circ}C$ to $60^{\circ}C$ may lead to breakdown of cable insulation and thermal runaway if the surrounding backfill material is unable to dissipate the heat as rapidly as it is generated. This paper describes the results of studies aimed at the development of backfill material to reduce the thermal resistivity. A large number of different additive materials were tested to determine their applicability as a substitute material. The results of Dong-rim river sand (relatively uniform) show that as water content level increases, thermal resistivity tends to decrease, whereas the thermal resistivity on dry condition is very high value($260^{\circ}C-cm/watt$). In addition, other materials(such as Jinsan granite screenings, A-2(sand and gravel mixture), E-1(rubble and granite screenings mixture) and SGFC(sand, gravel, fly-ash and cement mixture)) are well-graded materials with low thermal resistivity($100^{\circ}C-cm/watt$ when dry). Based on this research, 4 types of improved materials were suggested as the environmentally friendly backfill materials with low thermal resistivity.

• Journal of the Korean Society for Railway
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• v.19 no.6
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• pp.765-776
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• 2016

In this study, a standard section of a railway bridge abutment wall was designed to satisfy the external stability condition in accordance with the design criteria; this design was used to compare and analyze the active earth pressure and to calculate various types of earth pressure acting on the virtual back (wall, plane) according to the frictional angle of the backfill materials. Also, the external stability, member force and construction cost were analyzed according to the frictional angle of the backfill materials using various theories of earth pressure such as Rankine, Coulomb, Trial Wedge, and Improved Trial Wedge. As for the results, it was found that lateral earth pressure at the virtual back plane was higher than at the virtual back wall, and that these values decreased with the increase of the frictional angle of the backfill materials. The increasing of the frictional angle of the backfill materials decreased the active earth pressure (according to Rankine, Coulomb, Trial Wedge, and Improved Trial Wedge results), and the member force as well as the construction cost were reduced.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1258-1263
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• 2010

Backfill material of buried electrical transmission cable should dissipate the heat as rapidly as it is generated, or high temperatures will lead thermal runaway. These problems could raise thermal resistance and recude trasmission efficiency. So Backfill material of buried electrical transmission cable should have not only structual safty but good thermal property. So, in this study, we performed thermal resistancy test for various materials such as sand, weathered soil, clay and mixed soil to analyze the thermal characteristics of CLSM(controlled low strength materials) for water content.

• Journal of the Korean Geotechnical Society
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• v.21 no.6
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• pp.41-52
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• 2005

Because the allowable current loading of buried electrical transmission cables is frequently limited by the maximum permissible temperature of the cable or of the surrounding ground, there is a need fur cable backfill materials that can maintain a low thermal resistivity even while subjected to high temperatures for prolonged periods. Temperatures greater than $50^{\circ}C\;to\;60^{\circ}C$ may lead to breakdown of cable insulation and thermal runaway if the surrounding backfill material is unable to dissipate the heat as rapidly as it is generated. This paper describes the results of studies aimed at the development of backfill material to reduce the thermal resistivity. A large number of different additive materials were tested to determine their applicability as a substitute material. Tests were carried out for Dongrim river sand, a relatively uniform sand of very high thermal resistivity, $50^{\circ}C-cm/watt\;at\;10\%$ water content, $260^{\circ}C-cnuwatt$ when dry, and Jinsan granite screenings, and D-2 (sand and granite screenings mixture), E-1 (rubble and granite screenings mixture), a well-graded materials with low thermal resistivity, about $35^{\circ}C-cm/watt$ when at 10 percent water content, $100^{\circ}C-cm/watt$ when dry. Based on this research, 3 types of backfill materials were suggested for improved materials with low thermal resistivity and the applicability was assessed through field tests.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.209-220
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• 2002

Because the allowable current loading of buried electrical transmission cables is frequently limited by the maximum permissible temperature of the cable or of the surrounding ground, there is a need for cable backfill materials that can maintain a low thermal resistivity (less than 5$0^{\circ}C$-cm/watt) even while they are subjected to high temperatures for prolonged periods. Temperatures greater than 5$0^{\circ}C$ to 6$0^{\circ}C$ may lead to breakdown of cable insulation and thermal nlnaway if the surrounding backfill material is unable to dissipate the heat as rapidly as it is generated. This paper describes the results of studies aiming at the development of backfill material to reduce the thermal resistivity. A large number of different additive materials were tested to determine their applicability as a substitute material. Tests were called out for DonUing river sand, a relatively uniffrm sand of very high thermal resistivity (5$0^{\circ}C$ -cnuwatt at 10% water content, 26$0^{\circ}C$-cm/watt when dry), and Jinsan granite screenings, and A-2(sand and gravel mixture), E-1 (rubble and granite screenings mixture), a well-graded materials with low thermal resistivity (about 35$^{\circ}C$ -cm/watt when at 10 percent water content, 10$0^{\circ}C$-cm/watt when dry). Based on this research, 3 types of backfill materials were suggested for improved materials with low thermal resistivity.

• Journal of the Korean Geosynthetics Society
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• v.10 no.4
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• pp.123-130
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• 2011

In the precedent study it was presented that the comparison of thermal resistivity using various backfill materials including river sand regarding water content, dry unit weight and particle size distribution. Based on the precedent study, this study focused on developing the optimized backfill material that would improve the power transfer capability and minimize the thermal runaway due to an increase of power transmission capacity of underground power cables. When raw materials, such as river sand, recycled sand, crush rock and stone powder, are used for a backfill material, they has not efficient thermal resistivity around underground power cables. Thus, laboratory tests are performed by mixing Fly-ash, slag and floc with them, and then it is found that the optimized backfill material are required proper water content and maximum density. Through various experimental test, when coarse material, crush rock, is mixed with recycled sand, stone powder, slag or floc for a dense material, the thermal resistivity of it has $50^{\circ}C$-cm/Watt at optimum moisture content, and the increase of thermal resistivity does not happen in dry condition. The result of experiments approach the optimization of the backfill materials for underground power cables.

• Journal of the Korean Geotechnical Society
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• v.22 no.1
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• pp.15-23
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• 2006

During earthquake, force components acting on quay walls consist of inertia force, earth pressure and water pressure. The earth pressure is largely influenced by the backfill condition such as soil density and the installation of gravel backfill. Therefore, shaking table tests were performed by using four different model sections, which were designed by varying the soil density and the backfill materials. The magnitude and the phase of force components acting on quay wall were analyzed. Test results showed that the gravel backfill and the soil compaction were effective to reduce the excess pore pressure in backfill and the magnitude and phase of backfill thrust were much influenced by the excess pore pressure in backfill. When the input acceleration was 0.10g, the average ratios of the inertia force, the front dynamic water force and the thrust to the total force were $64\%,\;21\%\;and\;16\%$, respectively. As the excess pore pressure increased, the ratio of the thrust to the total force increased.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.1
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• pp.72-83
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• 2015

Underground transmission lines always generate heat and transmit heat through surrounding backfill materials. Therefore, in the design of power lines it becomes a very crucial factor to transfer heat effectively into the neighbouring soils. In this study, in order to enhance field applicability of recycled aggregates for backfill material of transmission lines, quality criteria and construction criteria were proposed, and thermal stability of power lines through field demonstration tests were analyzed. In the field tests, two types of recycled aggregates and sand which is currently used for backfilling were compared in terms of thermal behaviour. Test results showed that recycled aggregates represented similar trends with sand in temperature and moisture content corresponding to time lapse and distance from the heat source. Consequently, recycled aggregates can be utilized for backfill materials of underground transmission lines as a substitute material of sands.

• Journal of the Korean GEO-environmental Society
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• v.10 no.5
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• pp.11-18
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• 2009

When underground pipe is installed, backfill materials need proper compaction. But in case of circular underground pipe, compaction of backfill material is difficult and compaction efficiency is poor at beloe the pipe. It caused the stability of underground pipe is reduced and various damages occurred. One of the solutions to solve this problem for underground pipe is to use controlled low strength material (CLSM). CLSM is made by concept of low strength concrete, which is applied to geotechnical engineering field. The representative characteristics of CLSM are self-leveling, self-compacting and flowability. In addition, its strength can be controlled and its construction method is simple. The behavior of underground pipe was investigated by finite element analysis for various backfill materials under same condition. As a result, in case of using the CLSM as backfill material, surface settlement and displacement of pipe are reduced comparing with those in case of using field soil or sand.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.250-252
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• 2003

This paper is the estimation of the thermal property for the backfill materials according to the experimental measurements both a laboratory and field test.