• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1346-1353
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• 2009

In this study, a numerical study was carried out to simulate the expansion of ground borehole by pulse discharge technology using finite element analysis. Considering the mortar in the borehole as an acoustic medium and the surrounding soil as an elasto-plastic material, the strong shock wave developed by the pulse discharge was modeled using the underwater explosion model. The ground expansion was simulated based on a coupled acoustic-structural analysis with varying properties of mortar and soil, and the behavior between acoustic-structural interface.

• Journal of the Korean Society for Railway
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• v.3 no.2
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• pp.84-91
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• 2000

The general concept of reinforced roadbed in the high-speed railway is to cope with the soft ground for the bearing capacity and settlement of foundation soil. The cyclic plate load tests were performed to determine the behavior of reinforced ground with multiple layers of geogrid underlying by soft soil. With the test results, the bearing capacity ratio, elastic rebound ratio, subgrade modulus and the strain of geogrids under loading were investigated. Based on these plate load tests, laboratory model tests under cyclic loading were conducted to estimate the effect of geogrid reinforcement in particular for the high-speed rail roadbed. The permanent settlement and the behavior of earth pressure in reinforced roadbed subjected to a combination of static and dynamic loading are presented.

• Journal of the Korean Society for Railway
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• v.5 no.2
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• pp.70-76
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• 2002

In this study, performance of reinforced railroad roadbeds with the reinforced roadbed materials were investigated through the real scale roadbed tests. It was also found that the reinforced roadbed with reinforced roadbed materials has less elastic and plastic settlement than the one with soil. The slag roadbed was more effective than the crushed stone roadbed with the same condition for load distribution. Therefore considering overall characteristics of reinforced roadbed material, the optimum thickness was recommended as 50 cm. Furthermore the real scale model test under the simulated rainfall condition, the settlement in the slag roadbed was about 8 times smaller than the settlement in the soil roadbed.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.357-364
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• 2002

This paper describes the feasibility of compacting subgrade layer in thicker lifts than currently permitted as 20 cm. This project involved constructing and testing a full scale test section in highway. Soil stiffness in field was evaluated by a nondestructive testing method, called Geogage. Quality control tests and FE Analysis were also conducted. Typical dynamic compaction roller of 11ton weight is applied for full scale test and a Mohr-Coulomb model and Plane strain condition are used for FE Analysis. The results showed that compaction-induced stress and dissipated energy are mainly depend on depth of soil and it could be possible to increase thickness of a lift.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.116-120
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• 2003

To study the trafficability on soft and cohesive benthic terrain, a tracked vehicle model($670mm(L){\times}750mm(B_c)$) is designed and tested. The pitch and chevron angle of grouser, weight and center of gravity of vehicle, and drawbar pull force are chosen as experimental variables. Slip, sinkage and inclined angle of vehicle are picked as performance values. Strength of soil is considered as noise factor. A preliminary straight-line motion test is performed. Then, DOE(Design of Experiment) is discussed for further research.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.2
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• pp.97-103
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• 2008

Determination of stress-strain relationship in torsional tests is complicated due to nonuniform stress-strain variation occurring linearly with the radius in a soil specimen in torsion. The equivalent radius approach is adequate when calculating strain at low to intermediate strains, however, the approach is less accurate when performing the test at higher strain levels. The modified equivalent radius approach was developed to account for the problem more precisely. This approach was extended to generate the plots of equivalent radius ratio versus strain using modified hyperbolic and Ramberg-Osgood models. Results showed the effects of soil nonlinearity on the equivalent radius ratio curves were observed. Curve fitting was also performed to find the stress-strain relationship by fitting the theoretical torque-rotation relationship to measured torque-rotation relationship.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1998.06a
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• pp.91-95
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• 1998

본 연구의 목적은 산업활동에 많이 이용되고 환경학적으로 난분해성으로 알려졌으며, 특히 일반적인 미생물에 위한 생분해가 용이하지 않은 대표적인 방향족 화합물인 아조염료의 생분해능이 우수한 방선균을 토양에서 분리하여 그 분해특성을 연구하는데 있다. 본 연구실에서는 용인지역에서 무작위로 채취한 토양에서 방선균들을 분리하고, 이들중 아조계 화합물의 생분해능이 우수한 토양방선균 AD001을 대표적인 아조계화합물인 censored를 model compound로 이용하여 분리해 내었다. 방선균 AD001은 congored가 포함된 agar배지에서 censored를 아주 우수하게 decolorization 시킴이 관찰되었다. 이미 아조염료를 우수하게 분해한다고 알려져 있는 Streptomyces viridosporus T7A와 비교 실험을 수행한 결과, S. viridosporus는 cellulose를 탄소원으로 사용할 때 확실한 congored의 decolorization을 보인 반면 AD001의 경우 sucrose를 탄소원으로 사용할 때 더욱 뚜렷한 congored의 decolorization 현상이 관찰되었다. 또한 이런 분해특성의 특이성을 관찰하기 위해 구조적으고 상이한 new fuchsin으로 실험한 결과, 염료의 농도를 0.005% 주었을 때 S. viridosporus는 성장을 하지 못한 반면 AD001의 경우 배지에 포함된 new fuchsin을 확실하게 decolorization 시킴도 관찰할 수 있었다. 이러한 실험결과는 토양 방선균 AD001이 환경학적으로 아주 유용하게 이용될 수 있음을 제시하고 있다.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1998.06a
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• pp.87-90
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• 1998

본 연구의 목적은 방향족 화합물의 생분해능이 우수한 토양 방선균을 분리하여 방선균에 의한 방향족 화합물의 생분해 기작 및 생분해 특성을 연구하는 것이다. 본 연구실에서는 phenol을 model compound로 실험한 결과, 일반 토양에서 분리한 많은 방선균들이 비록 농노의 차이를 보이기는 하지만 phenol의 생분해능을 갖고 있었다. 그러나 이들 대다수의 방선균들을 낮은 농도의 phenol에서만 일정 기간 성장을 하며, morphological differentiation 및 포자의 형성과 같은 일반적인 방선균의 성장 특성은 전혀 관찰되지 않았다. 이들 중 몇 종류의 분리된 방선균들 낮은 농도에서의 우수한 성장은 물론이고 상당히 높은 농도 (7mM)에서도 phenol을 유일한 탄소 및 에너지원으로 사용하여 성장하며 정상적인 morphological differentiation을 진행시킴이 관찰되었다. 특히 PD001로 명명된 phenol 분해능이 우수한 방선균에서는 일반적인 방선균 성장 온도 (3$0^{\circ}C$) 보다 높은 45$^{\circ}C$의 고온에서 더 빠른 성장을 보이는 고온성 방선균의 특징도 관찰되었다.

• Journal of Soil and Groundwater Environment
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• v.21 no.2
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• pp.22-28
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• 2016

In order to evaluate landfill stabilization based on organic carbon, stoichiometric analysis and a biological methane potential (BMP) test based on modeling were performed at the 2^nd Sudokwon Landfill Site. Mass balance analysis through a BMP test proved to be more adaptable for evaluation, and it showed that 28.9% of landfill organic carbon was expected to remain by 2046, 30 years after landfill closure. The organic carbon ratio of total landfill waste for 2046 is forecasted as 2.9% in demolition waste and 5.1% in household waste, and, if one were to consider plastic as an organic waste, the ratios would increase to 15.9% and 28.3%, respectively. Therefore, it seems that organic matter biodegradation facilitating measures such as bioreactor landfill technology and preemptive recovery of combustible waste are necessary to shorten post closure management periods and to meet the landfill stabilization guidelines more safely.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.3
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• pp.191-199
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• 2019

To calculate proper seismic design load and seismic design category, the exact site class for construction site is required. At present, the average shear-wave velocity for multi-layer soil deposits is calculated by the sum of shear-wave velocities without considering of vertical relationship of the strata. In this study, the transfer function for the multi-layered soil deposits was reviewed on the basis of the wave propagation theory. Also, the transfer function was accurately verified by the finite element model and the eigenvalue analysis. Three methods for site period estimation were evaluated. The sum of shear-wave velocities underestimated the average shear-wave velocities of 526 strata with large deviations. The equation of Mexican code overestimated the average shear-wave velocities. The equation of Japanese code well estimated the average shear-wave velocities with small deviation.