• Journal of the Korean earth science society
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• v.36 no.1
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• pp.16-26
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• 2015

To investigate the applicability of physical prospecting technique in soft ground assessment, the resistivity monitoring data of 6 months are acquired. The Multichannel Analysis Surface Wave (MASW) has been additionally performed to identify the shear wave velocity and strength distribution of soft ground. Moreover, by using the Cone Penetration Test (CPT) and laboratory tests of drilling samples, a relationship with the physical prospect data is checked and the reliability of the physical prospect data is increased. Through these activities, the behavior patterns of soft soil are identified by long term monitoring, and the significant relationship between the shear wave velocity and laboratory tests has been confirmed, both of which can be useful in the surface wave exploration to evaluate the strength of soft ground. Finally, using the geostatistical method, 3-dimensional soil base distribution images are obtained about the combined physical prospecting data with heterogeneous data. Through the studies, the nature of entire area can be determined by long term resistivity monitoring for the soft ground assessment in wider area. It would be more economic and reliable if additional exploring and drilling samples can be analyzed, which can reinforce the assessment.

• Geomechanics and Engineering
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• v.8 no.1
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• pp.113-132
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• 2015

In this study, lime (L), silica fume (SF), and lime-silica fume (L-SF) mix have been used for stabilizing and considering their effects on the soft clay soil. The improvement technique adopted in this study includes improving the behaviour, of a square footing over soft clay through grouting the clay with a slurry of lime-silica fume before and after installation of the footing. A grey-colored densified silica fume is used. Three percentages are used for lime (2%, 4% and 6%) and three percentages are used for silica fume (2.5%, 5%, 10%) and the optimum percentage of silica fume is mixed with the percentages of lime. Several tests are made to investigate the soil behaviour after adding the limeand silica fume. For grouting the soft clay underneath and around the footing, a 60 ml needle was used as a liquid tank of the lime-silica fume mix. Slurried silica fume typically contains 40 to 60% silica fume by mass. Four categories were studied to stabilize soft clay before and after footing construction and for each category, the effectiveness of grouting was investigated; the effect of injection hole spacing and depth of grout was investigated too. It was found that when the soft clay underneath or around a footing is injected by a slurry of lime-silica fume, an increase in the bearing capacity in the range of (6.58-88)% is obtained. The footing bearing capacity increases with increase of depth of grouting holes around the footing area due to increase in L-SF grout. The grouting near the footing to a distance of 0.5 B is more effective than grouting at a distance of 1.0 B due to shape of shear failure of soft clay around the footing.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1031-1034
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• 2007

Electric transmission lines pass through a variety of area. Foundation supporting the conductors and tower are selected properly in accordance with external load, for example dead load, wind load, snow load, construction load etc, and topography and geology condition. Typical types of foundation are as follows: pad foundation for small load and hard soil or rock in mountainous area, pile foundation for medium or large load and soft soil in plain field area. This paper introduced cylindrical foundation design & construction for large load and mountainous area. This foundation failure mode against pulling-out show splitting failure by tensile force toward circumferential direction.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.11c
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• pp.105-116
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• 1999

The Inchon International Airport site was formed by reclaimed soil from the sea. The average thickness of soft soil Is about 5 m and most of soft soils are normally consolidated or slightly over consolidated. There are many box culverts which are being constructed under the runways in the airfield. Sometimes, differential settlement can be occurred in the adjacent of box culvert or underground structures at the top layer of runway Soil compaction at very near to the structure is not easy all the time. Thus, one layer of geogrid was placed at the bottom of lean concrete layer for the concrete paved runway and at the middle of cement stabilized sub-base course layer for the asphalt paved runway. The length of geogrid reinforcement is 5m from the end of box culvert for both sides. The extended length of geogrid was 2m from the end of backfill soil in the box culvert. The tensile strength tests of geogrid were conducted for make sure the chemical compatibility with cement treated sub-base material. The location of geogrid placement for the concrete paved runway was evaluated. The construction damage to the geogrid could be occurred. Because the cement treated sub-base layer or lean concrete was spread by the finisher. The magnitude of tensile strength reduction was 1.16%~1.90% due to the construction damage and the ultimate tensile strength is maintained with the specification required. Total area of geogrid placement in this project is about 50,000 $m^2$.

• Proceedings of the KSR Conference
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• 2000.05a
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• pp.392-398
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• 2000

When soft ground improvement is proceeded in costal area using compulsory replacement method, it is very important that the method of stability of embankment above replacement layer can be obtained if non-replaced soft layer is remained, and there are a lot of influence factors which affect the stability of embankment, such as replacement depth, the water content of dredged soil and the width of replacement layer, etc. If soft layer was replaced completely by good quality materials, there would be no problems about stability of embankment, but practically non-replaced layer would be remained as the strength of soft layer will be increased. So another consideration is required to get the stability of embankment. In this study, stability of embankment among these factors was compared, and from that results, the better way that could obtain the stability was presented.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.309-316
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• 2000

When highly compressible, clayey soil layers lies at a limited depth and large consolidtion settlements are expected as the result of construction, precompression of soil may be used to minimize postconstruction settlement. In this study, we tried to find the possibility about the effect of ground improvement using flat dilatometer at the Inchon International Airport where preloading was installed. Field and laboratory tests were performed for soft ground before and after preloading in order to check the effectiveness of the soft ground improvement and compared with the test results of dilatometer which obtained before and after preloading at the same location Field tests such as flat dilatometer, vane, CPTu tests were performed before and after preloading and undisturbed samples are obtained to carry out laboratory tests. As comparing results, after preloading, unit weight, effective stress, undrained shear strength were increased and we can also check the decrease of consolidation late caused of decrease of void ratio. Furthermore, it is assumed that the possibility on the effect of ground improvement by using the flat dilatometer

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.480-488
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• 2010

The CGS method is non-discharge replacement method improving ground stiffness by the effect of static compaction with injecting very low slump mortar into ground, and is applied for increasing bearing capacity and filling ground cavity by lifting or restoring differential settled structures and preventing differential settlement. This paper suggests design of ground improvement and construction case history for civil engineering structures by CGS method. This method can be used for reinforcing soft ground and liquefaction of loose sandy soil. This method was used in SongDo area in Incheon Economic Free Zone due to its low vibration of ground while it can improve the soft soil where underground structures(subway and box culvert) are already existed.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.11a
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• pp.96-109
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• 2001

Land was reclaimed at the waterfront in the Pluit area of Jakarta for a 90ha residential-cum-recreational development. The reclamation works involve construction of permanent and temporary dykes, fill placement, soil improvement, dredging of internal canals and marina, and construction of canal revetment. The site lies on 16m to 18m thick soft seabed deposits. Settlement of the reclaimed areas will result as a consequence of consolidation of the soft underlying sediments. In order to reduce post-construction settlement to within acceptable levels, a system of vertical drains and preloading was adopted. This paper describes the use of Fibredrain, a prefabricated vertical drain made of jute and coir fibres developed at the National University of Singapore, in the soil improvement works and a secondary use in the construction of perimeter dykes for the reclamation works. The construction of the perimeter dyke must be carried out in such a way that slope stability is on ensured. Bamboo rafts and bamboo clusters with Fibredrain inserted, and stage construction were employed to improve stability during the dyke formation for the Pantai Mutiara project.

• Journal of the Korean Society of Safety
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• v.23 no.6
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• pp.131-137
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• 2008

SCP(Sand Compaction Pile) method that forms a composite ground by driving compacted sand piles into the soft ground. This method is one of the soil improvement techniques for reinforcing and strengthening soft ground deposits. This thesis describes the investigation on the behavior of soft ground reinforced with SCP by low improvement ratio. Direct shear test and consolidation test carried out to verified behavior of composite ground reinforced with SCP. Test results were discussed with reference to the amount of consolidation settlement, variation of shear resistance with area replacement ratio and effect of the stress concentration. And, laboratory model loading test carried out to verified the effect of the location and failure mode of reinforced embankment. Residual shear strength varies with the area replacement and constrict load in the low replacement ratio. Calculated stress concentration ratio overestimate than proposed valve by experimental, theoretical and analytical method. As regards the location, improving right below of the top of the slope was more effective than below of the toe of the slope. This thesis carried out to obtain fundamental information of behavior of the composit ground. Hereafter, centrifuge test that reproduce stress state of the in-situ must be necessary through the further study about pile penetration, reinforce position and construct time.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.896-901
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• 2009

A Soil Nail is a structural element which provides load-transfer to the ground in excavation reinforcement applications. The nail may simply consist of a steel tendon, but most commonly the tendon is encapsulated in a cement grouted body to provide corrosion protection and improved load- transfer to the ground. For temporary excavation support in a congested urban area, the steel bar of Soil Nails should be removed to get permission of the private land to install Soil Nails. Several removable nail systems were developed and evaluated by pull-out load tests. The Soil Nail pull-out tests were performed on five nails installed in soft and hard rock at a 00 housing-redevelopment area in seoul. Two nails are plastic socket type and two are complex socket type mixed steel and plastic. The nail was 0.1mm in diameter, 4m long. In this study verification tests, and steel bar removing tests of plastic socket type nails and complex socket type nails were performed and presented.