• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.09a
• /
• pp.638-645
• /
• 2010

This study introduces a reinforcement work case using Twin-Jet Method. The area is located behind the abutment of the bridges built on soft clay along the $\bigcirc\bigcirc$ Express Highway. Its foundation was constructed by installing EPS blocks on the original ground to reduce the embankment load under the highway. However, the ground deformation has continuously occurred due to the settlement of the foundation soft cohesive soils. The amounts of subsidences at the surface turned out to be 20~30.0mm, After the pavement patch work on April 23, 2009, a drastic subsidence occurred together with 10mm swell, For this reason, Twin-Jet grout column construction was applied by passing through the EPS banking blocks without closing traffic flows on the express highway. The outcomes of core sample tests after reinforcing the ground turned out to be TCR 92.5%, RQD 64.6% and unconfined compressive strength 2.3~8.6Mpa. The test results showed that the condition of the ground foundation had improved using Twin-Jet grouting in most layers of ground including the cobble and gravel layer.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.11 no.6
• /
• pp.113-120
• /
• 2007

For the cases of constructing reinforced earth and gabion walls on the soft ground, an appropriate replacement area of soft ground required to maintain the stability of walls was investigated by FEM analyses. Incremental analyses were performed in FEM, in which construction sequences including consolidation of soft soil layer were simulated. As a first step to suggest the appropriate replacement area, a series of analyses for cases varying the replacement depth were conducted to examine the behaviors of wall and adjacent ground according to the construction sequence. The analysis results were, then, evaluated with the proper limiting values of displacements of wall, settlements and shear strains of ground to guarantee the stability of walls, which were specified based on the literature review. Consequently, the typical construction drawings could be suggested, in which appropriate replacement areas for varying wall heights for the ground condition investigated in this study were represented in terms of the ratio of replacement depth to the height of wall.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.37 no.3
• /
• pp.232-248
• /
• 2004

In order to utilize fisheries resources under a joint management scheme with adjacent nations, as well as detecting of fishing grounds, the factors which influence yellow croaker (Pseudosciaena polyactis) in Korean waters were studied using historical catch per unit effort and oceanographic data. The main fishing ground near Cheju Island was located along the thermal front formed between the Yellow Sea Bottom Cold Water (YSBCW) and northward moving warm current. When the YSBCW (index temperature: $10^{\circ}C)$ strongly extended southward, the fishing condition were worse than average. Especially, low temperatures greatly influenced stow net fisheries, which were operated in the deep water layer The concentration and dispersal of fishing ground and catch coincided with oceanographic features and the seasonality of water masses.

• Corrosion Science and Technology
• /
• v.16 no.6
• /
• pp.298-304
• /
• 2017

Coil spring steels from the automobile suspension part after field exposure for 10 years and those after anti-corrosion validation test in proving ground of 5,000 ~ 10,000 km were examined for corrosion damages. Partial loss of paint, accumulation of corrosion product, and cracking of paint and superficial material were observed. The surface and subsurface region of spring steels had compressive residual stress and high hardness by shot peening. The surface hardness values of the specimens were 620 ~ 670 Hv. They were 60 ~ 80 Hv higher than those of the samples taken from the middle part of the spring. The maximum compressive stress was -916 ~ -1208 MPa measured at depth of about $100{\mu}m$. Electrochemical impedance spectroscopy showed that the resistances of charge transfer and the paint layer of the spring steels ranged from several tens to millions ${\Omega}{\cdot}cm^2$. The resistance of the field samples was much higher than that of the proving ground samples used in this study, implying that the proving ground test condition would be more corrosive than the field environment.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.6 no.2
• /
• pp.175-182
• /
• 2002

The cement injection technology on the purpose of ground reinforcement and cut-off has been used in construction sites until now. However, recently it is applied to prevent leakage of underground structure. In this study, applicability of the back side waterproof grouting method was verified through performing field model tests and reviewing case histories. From the results of this study, injection shape of the back side waterproof grouting method was appeared to be root type, and waterproof effect by injection of cement grout material was excellent because grout material infiltrated into boundary between wall of structure and back side ground to be waterproof layer. Components influencing infiltration of injection material are type of soil and degree of compaction. For effective injection, injection pressure has to vary gradually from high pressure to low pessure and small quantity of injection material has to be injected for long times. Also, spacing of injection hole must be designed considering condition of back side ground, injection area, W/C ratio, the number of injection and injection pattern properly.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.10a
• /
• pp.1712-1716
• /
• 2008

Performance of ground improvement project using prefabricated vertical drains of condition, in which approximately 10m dredged fill overlies original soft foundation layer in the coastal area has been conducted. From field monitoring results, excessive ground settlement compared to predicted settlement in design stage developed during the following one year. In order to predict the final consolidation behavior, recalculation of consolidation settlements and back analysis using observed settlements were conducted. Field monitoring results of surface settlements were evaluated, and then corrected because large shear deformation was occurred by construction events in the early stages of consolidation. To predict the consolidation behavior, material functions and in-situ conditions from laboratory consolidation test were re-analyzed. Using these results, height of additional embankment is estimated to satisfy residual settlement limit and maintain an adequate ground elevation. The recalculated time-settlement curve has been compared to field monitoring results after additional surcharge was applied.

• Journal of Soil and Groundwater Environment
• /
• v.6 no.3
• /
• pp.107-117
• /
• 2001

The characteristics of groundwater movement under the heavy rainfall at Nan-ji waste landfill site are studied using HELP(Hydraulic Evaluation of Landfill Performance) program, which calculates the daily leachate in the Nan-ji waste landfill site. In this study, instead of the average recharge value, which is used in the past study, the real reacharge value is used to calculate the daily leachater. It is found about 70 times greater than thor average recharge value under the condition of heavy rainfall in the rainy season. The flow characteristics of groundwater for water level fluctuation is simulated using the ground water flow model MODFLOW(A Modular 3-D Finite Different Groundwater Flow Model) program, and the slurry layer is newly added. The result of the study is different from that of the ordinary simulation, which shows much higher ground water level than from the ordinary simulation.

• Journal of Conservation Science
• /
• v.27 no.4
• /
• pp.451-458
• /
• 2011

This study aims at identifying wall painting production technique of Songsanri No. 6 tomb based on optical examination and scientific analysis along with the investigation of written records of ancient wall paintings. The result displays that bricks with mortar were used for the construction of the wall, and masonry joint were made of lime, sand and gypsum. The surface of brick were plastered with black and thereafter with white lime. Finely sifted clay on the top of the white surface, were applied not with plasterer's trowel but with a brush for making ground surface. The clay are mineral particles smaller than $30{\mu}m$ of silt. The wall paintings of Sonsanri No. 6 is the only example of making ground layer with clay for painting of Sasindo (literally four heavenly animals painting) among remaining wall paintings of ancient tombs. The historical value of the painting should be attributed not only in terms that it displays a rare production techniques which were never discovered in any other paintings in Korea and Asia, but also it might had been uncompleted when the tomb were closed, even though it considers the fact that the wall painting were discovered in damaged condition in 1933.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.22 no.3
• /
• pp.1-7
• /
• 1986

This is a basic study of further investigating the effect of oceanographic conditons, such as bottom profile, currents, and temperature, to the fish migrating course around the set-net. The survey was held at Dojang Po, southern part of Geoje Island, from July to October in 1985. There was a sea valley of which depth was 20 to 40 meters around the set-net. Near the bottom of that sea valley, there was different current pattern to the upper layer. In the sea calm condition of July and October, the vertical profiles of current and water temperature were simple. But in rough condition of September, they were complicated because of wind tuburance.

• Journal of the Korean Geosynthetics Society
• /
• v.18 no.4
• /
• pp.299-306
• /
• 2019

In this study, a model experiment that simulates the behaviour of the ground composed of several compacted layer was intended to measure the loosened area in the event of a ground cavity through a LAD (Loosened area detector). It was confirmed that the size of the cone diameter was affected by the ground composed of fine grain + granulated soil layered through the model soil. In order to select the appropriate cone type, a scale effect experiment was conducted. From the test results, a micro-cone was chosen for the most suitable indoor model experiment. In the case of applying LAD in this study, the loosening condition of the ground was determined by the rapid change in penetration resistance caused by the difference in the boundary surface and relative density due to the compaction of the ground for indoor model testing. The range of loosened area occurring in the cavity was estimated through the penetration resistance characteristics on the ground, and the failure area was identified through the reduction rate of penetration resistance in the loosening area.