• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1997.04a
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• pp.265-272
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• 1997

This paper presents the result of an international cooperative research on the post-correlation analysis of forced vibration tests and the prediction of earthquake responses of a large-scale seismic test structure. Through the post-correlation analysis, the properties of the soil layers are revised so that the best correlation in the responses may be obtained compared with the measured force vibration test data. Utilizing the revised soil properties as the initial linear values, the seismic responses are predicted for an earthquake using the equivalent linearlization technique based on the specified strain dependent characteristics of the shear moduli and damping ratios. It has been found that the predicted responses by the equivalent nonlinear procedure are in excellent agreement with the observed responses, which those using the initial properties are fairly off from the measured results.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1204-1211
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• 2008

Compression index is one of the important characteristic numbers in soft soil engineering. Since 1940's, many researchers have suggested various practical solutions to define the compression index of clay using other soil properties. But, these results are only can give us an outline of soft soil behavior. In this study, the relationships between pore water pressure dissipation test results and compression index were suggested using comparison results of both tests. This relationships are based on basic concept of consolidation phenomena, essential difference between pore water pressure dissipation test and consolidation test, and disagreements between theoretical time factor and real time factor. To identify proportional factor of proposed equation, Geotechnical investigation results of Kwang-Yang(KY) site and Busan New Port(BN) site were used. The proportional factor was 0.0031 from 20 to 50% of consolidation rate where correlation parameter($R^2$) is 0.9051.

• Journal of Soil and Groundwater Environment
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• v.21 no.1
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• pp.1-5
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• 2016

Capillary barriers, consisting of relatively fine-over-coarse materials, have been suggested as an alternative to traditional compacted soil covers. So, We were analysed to capillary barrier effect according to five cases of multi-layer cover systems. Water balance simulation was conducted with unsaturated flow model HELP to assess unsaturated hydraulic parameters such as hydraulic conductivity, climate affecting the performance of capillary barriers. Simulation were conducted for 5 Cases in the Ulsan area. Result of simulation indicated that three cases was formed unsaturated condition and capillary barrier effect.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.832-835
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• 2005

The free vibration of tapered piles embedded in soil is investigated. The pile model is based on the Bernoulli-Euler beam theory and the soil is idealized as a Winkler model for mathematical simplicity. The governing differential equations for the free vibrations of such members are solved numerically. The square tapered piles with one free and the other hinged end with rotational spring are applied in numerical examples. The lowest two natural frequencies are obtained over a range of non-dimensional system parameters: the rotational spring parameter, the embedded ratio, the foundation parameter, the width ratio of the contact area and the section ratio.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1998.11a
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• pp.76-80
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• 1998

In order to identify the cause of ground water drawdown of a piezometer installed around the LPG storage cavern, parameter estimations were conducted by inverse and forward numerical models. An inverse model, SK-EST developed by SK Engineering & Construction Co., Ltd.(SKEC,1997) was performed to estimate the change of the hydraulic conductivity. It was verified by the commercial forward model, AQUA3D (VATNASKIL,1995). The simulation results showed that the hydraulic diffusivity of the rock mass between the piezometer and the cavern had been increased and the change rate of the hydraulic head had been abruptly increased in response to the change of the operation pressure. Finally the statistical analysis for observed data showed the increase of the change rate of the hydraulic head and thus proved the applicability of SK-EST.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.550-554
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• 2007

A one-dimensional heat transfer model coupled with parameter estimation is developed in this study to predict the effective thermal conductivities of soil formation and borehole resistances from in situ field test data. In this application a new method of using initial ignoring time(IIT) obtained from error estimation is tried and turned out to be successful in determining soil thermal conductivities. The validity of this model is accomplished through comparison of the predicted temperature profiles of the model with the data from laboratory scale experimental setting. Eleven test boreholes were constructed in Ochang, Chungcheong Buk Do, and thermal response test was carried out with each borehole. The results of the in situ tests were analyzed with our 1-D numerical model and compared with the results of line source method. The comparison shows that the thermal properties from line source method is a little lower (${\sim}95%$)than those from numerical method. The reason of such result seems to be the lower thermal conductivity of grout material, which is not counted in line source method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.3
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• pp.163-172
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• 1993

A probabilistic approach for evaluation of prediction of the strains using Lade's single surface constitutive model was employed, based on first-order approximate mean and variance. Several experiments such as isotropic compression and drained triaxial compression tests were conducted to examine the variabilities of soil parameters for Lade's model. By taking into account the results of the experimental data such as mean values and standard deviations of soil parameter's, a new probabilistic approach, which explains the uncertainty of computed strains, is applied. The magnitude of the COV for each parameter and the correlation coefficient between the two parameters can be effectively used for reducing the number of the parameters for the model. It is concluded that Lade's single surface constitutive model is surperior model for the prediction of the strain, because the COV of strains is under the "0.51".

• Earthquakes and Structures
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• v.9 no.2
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• pp.391-413
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• 2015

Damage of torsionally coupled buildings situated on soil sites has been reported in literature, however no site-specific studies are available for torsionally coupled buildings having site characteristics as a parameter. Effect of torsion is being accounted in seismic codes by the provision of design eccentricity where the dynamic to static eccentricity ratio is a parameter. In this paper, a methodology to determine dynamic to static eccentricity ratio of torsionally coupled buildings has been demonstrated for Delhi region for two torsionally coupled buildings on three soil sites. The variations of average and standard deviations of frame shears for stiff and flexible edges are studied for four eccentricity ratios for the two buildings for the three sites. From the limited studies made, it is observed that the dynamic to static eccentricity ratios observed for site-specific earthquakes are different from Indian seismic code specified value, hence a proposal is made to include a comment in Indian seismic code. Methodology proposed in this paper can be adopted for any region, for the estimation of dynamic to static eccentricity ratio for site specific earthquake.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.6
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• pp.712-719
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• 2016

Understanding N mineralization dynamics in soil is essential for efficient nutrient management. An anaerobic incubation experiment was conducted to examine N mineralization potential and N mineralization rate of the organic amendments with different C:N ratio in paddy soil. Inorganic N in the soil sample was measured periodically under three temperature conditions ($20^{\circ}C$, $25^{\circ}C$, $30^{\circ}C$) for 90 days. N mineralization was accelerated as the temperature rises by approximately $10%^{\circ}C^{-1}$ in average. Negative correlation ($R^2=0.707$) was observed between soil inorganic N and C:N ratio, while total organic carbon extract ($R^2=0.947$) and microbial biomass C ($R^2=0.824$) in the soil were positively related to C:N ratio. Single exponential model was applied for quantitative evaluation of N mineralization process. Model parameter for N mineralization rate, k, increased in proportion to temperature. N mineralization potential, $N_p$, was very different depending on C:N ratio of organic input. $N_p$ value decreased as C:N ratio increased, ranged from $74.3mg\;kg^{-1}$ in a low C:N ratio (12.0 in hairy vetch) to $15.1mg\;kg^{-1}$ in a high C:N ratio (78.2 in rice straw). This result indicated that the amount of inorganic N available for crop uptake can be predicted by temperature and C:N ratio of organic amendment. Consequently, it is suggested that the amount of organic fertilizer application in paddy soil would be determined based on temperature observations and C:N ratio, which represent the decomposition characteristics of organic amendments.

• Journal of the Korean Geotechnical Society
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• v.33 no.4
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• pp.25-34
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• 2017

The soil-water characteristics is the most important state parameter for understanding changes in suction and water contents of unsaturated soil slopes. In the field, the hysteretic behaviors of drying and wetting soil-water characteristic curve are real and the adoption of path-dependent suction-water content is needed to predict the hydro-mechanical analysis of unsaturated soils. In this study, in-situ monitored hydraulic behavior of various soil slopes are compared with the data from numerical analysis with the laboratory soil water characteristic curve. Then, the verifications are performed based on the field monitored data respectively. Therefore, the use of path-dependent soil-water characteristic curves could be more rational for design and analysis of unsaturated soil slopes under rainfall conditions.