• Journal of The Geomorphological Association of Korea
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• v.28 no.2
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• pp.45-57
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• 2021

In this study, the changes in morphology of Dokdo's gravel beach and its responses due to a storm event were analyzed using the aerial photos and 3D LiDAR data obtained during an ecosystem survey of the Dokdo in 2020. Dongdo Island's gravel beach, shown by aerial photo analysis, increased in area due to sedimentation after the construction of a dock, but there was no more significant changes in area after having grown to Sutdolbawi inside the dock. The changes in volume of the gravel beach were indicated based on 3D data acquired in May and November 2020. A strong typhoon that passed in September, 2002, caused erosion on the backshore and sedimentation on the foreshore and formed the berm by about 1.5 to 2 m high. The analysis showed that the sedimentation was 94.76 m³ in volume and 329 m² in area and the erosion was 250.75 m³ in volume and 603m² in area, which suggested that the overall change of the gravel beach was erosion. The changes in the morphology of the gravel beach on Seodo Island occurred with the seasons along with the changes in area. In addition, berms of different altitudes appeared on the southern and northern sides of the spit, which was also estimated to have formed by the seasonal current direction and wave energy.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1121-1128
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• 2007

Subway routes $1{\sim}4$ were constructed in gravel roadbed track structure in consideration of the technological capabilities, construction cost and duration at the time of the initial construction. As such, 224.8km, approximately 81.2% of entire length, of total length of railway track at 276.9km was constructed on gravel roadbed. However, improvement of gravel roadbed to concreted roadbed began in 1998 due to problems including frequent repair works and limited time application for such works caused by occurrence of tract distortion during operation as well as lowering of roadbed functions and generation of dust caused by frictional power, impact absorption capabilities, abrasion and crushing of gravel on roadbed. Currently, this improvement is continuing with target of converting entire route into concreted roadbed structure. Therefore, this Study modifies formula for setting cant, analyze the correlation between wearing of rail side of the curvature and cant insufficiency following increasing of the running speed of the train, and to present the directions for fundamental review for adjustment of cant insufficiencies at the time of improvement of gravel roadbed to concreted roadbed that is being implemented on the operational tracks of the railway trains.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.119-122
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• 2009

The gravel compaction pile method has been used as a soft foundation improvement method because bearing capacity and discharge capacity is excellent. But the discharge capacity decreased when the clogging was generated because the clay penetrate into a void of gravel compaction pile. Accordingly, the purpose of this study is to reduce the clogging generation in gravel compaction pile constructing in the soft ground and take a step to minimize a void of gravel compaction pile. And the proper mixing ratio was determined with the large scale direct shear test performed to get strength and permeability with mixing ratio of crushed stone and sand(100:0, 90:10, 85:15, 80:20, 75:25). As a result of the test, it was showed that internal friction angle was the highest at 85:15 mixing ratio of crushed stone and sand and we can make sure a tendency of internal friction angle's decrease when the mixing ratio of crushed stone and sand passed 15%.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.151-157
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• 2008

Subway routes $1\sim4$ were constructed in gravel roadbed track structure in consideration of the technological capabilities, construction cost and duration at the time of the initial construction. As such, 224.8km, approximately 81.2% of entire length, of total length of railway track at 276.9km was constructed on gravel roadbed. However, improvement of gravel roadbed to concreted roadbed began in 1998 due to problems including frequent repair works and limited time application for such works caused by occurrence of tract distortion during operation as well as lowering of roadbed functions and generation of dust caused by frictional power, impact absorption capabilities, abrasion and crushing of gravel on roadbed. Currently, this improvement is continuing with target of converting entire route into concreted roadbed structure. Therefore, this Study modifies formula for setting cant, analyze the correlation between wearing of rail side of the curvature and cant insufficiency following increasing of the running speed of the train, and to present the directions for fundamental review for adjustment of cant insufficiencies at the time of improvement of gravel roadbed to concreted roadbed that is being implemented on the operational tracks of the railway trains.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.1
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• pp.103-108
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• 2008

Riverbed change is greatly influenced by artificial factors such as dam construction, gravel collection, and river improvement. This study simulated a long-term bed change based on the GSTARS3 model using actual data from the area downstream of the Geum River Daecheong Dam and compared the estimation with a section of the actual measurement. As a result, it was found that the section of the actual measurement was far lower than the result of the simulation in terms of long-term bed change. While the area downstream of Daecheong Dam displayed approximately an average of 2.29 m of streambed degradation on average while the upper stream area showed approximately 0.63 m of bed degradation over 24 years. In the simulation of the area downstream of Daecheong Dam based on the GSTARS3 model, similar bed degradation was observed. However, a great difference was detected between the result and the actual measurement. According to the cause analysis, the riverbed in the area downstream of Daecheong Dam has continuously degraded due to the dam construction and mass collection of gravel. The mass collection of gravel was the main cause of riverbed change. It was found that about 76% of all riverbed degradation was caused by the mass collection of gravel.

• Tunnel and Underground Space
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• v.26 no.6
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• pp.466-474
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• 2016

Pre-reinforcement with umbrella arch grouting is conducted around a tunnel where a portion of the upper part of the tunnel is located in a sand and gravel layer. Surroundings of a first tunnel situated below groundwater table are reinforced with LW or SSM that is composed of ultra-fine cement and injected into multi-stages through large diameter steel pipes. With them, a first tunnel is safely excavated without both leaking of groundwater and fallings of sand and gravel from the arch. A second tunnel where groundwater is drained down to the bedrock is reinforced with jet grouting. The effect of the pre-grouting reinforcement is monitored by checking whether groundwater is dripping or sand or gravel is falling from the arch of the tunnels.

• Geomechanics and Engineering
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• v.30 no.5
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• pp.479-487
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• 2022

This study evaluates the performance of gravel impact compaction piers system (GICPs) in strengthening retrofitting a very loose silty sand layer with a very high liquefaction risk with a thickness of 3.5 meters in a multilayer coastal soil located in Bushehr, Iran. The liquefiable sandy soil layer was located on clay layers with moderate to very stiff relative consistency. Implementation of gravel impact compaction piers is a new generation of aggregate piers. After technical and economic evaluation of the site plan, out of 3 experimental distances of 1.8, 2 and 2.2 meters between compaction piers, the distance of 2.2 meters was selected as a winning option and the northern ring of the site was implemented with 1250 gravel impact compaction piers. Based on the results of the standard penetration test in the matrix soil around the piers showed that the amount of (N₁)₆₀ in compacted soils was in the range of 20-27 and on average 14 times the amount of (1-3) in the initial soil. Also, the relative density of the initial soil was increased from 25% to 63% after soil improvement. Also the safety factor of the improved soil is 1.5-1.7 times the minimum required according to the two risk levels in the design.

• Journal of Ocean Engineering and Technology
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• v.25 no.2
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• pp.47-54
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• 2011

A piled raft foundation is one of the systems used to reduce the settlement of structures. However, the general design method for a piled raft foundation system assumes that the piles only support external loads, which exclude the bearing capacity of the raft itself. In this study, an experimental model test was performed to evaluate the raft capacity for the external load on the sand. Additionally, a part of the sandy ground under the raft was replaced with a gravel mat to reinforce the piled raft foundation system and increase the bearing capacity. Then, parametric studies of the reinforced ground were performed to determine the displacement and load-sharing ratio of the piled raft foundation system.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.506-513
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• 2006

In this study, multi-level hi-direction pile load tests for drilled shaft pile socketed into the gravel were performed. The lower and upper hi-direction load test assemblies were located on tip of pile and 15m above the tip of pile. Based on the results of pile load test, it was analyzed bearing capacity of gravel, skin firction of upper soils and skin friction of lower soils. It was confirmed that drilled shaft socketed into the gravel had enough bearing capacity.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.836-841
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• 2008

CFRD (Concrete Faced Rockfill Dam) has been world-widely constructed due to a lot of advantages compared with rockfill dam and recently, sand/gravel materials, instead of crushed rock materials, are also utilized as a main rockfill material to overcome geological and environmental problems. In this paper, the process of water infiltration into the originally unsaturated sand/gravel-fill dam is studied using two-dimensional saturated-unsaturated seepage theory. According to the results of seepage analysis, if the effective drainage zone is installed in the dam, the reservoir water infiltrate into the dam along a downward flow path towards the lower drainage area. The main body constructed with sand/gravel materials, therefore, remains unsaturated.