• Earthquakes and Structures
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• v.4 no.2
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• pp.181-202
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• 2013

It is well known that the properties of the soil deposits, especially the damping, depend on both frequency and strain amplitude. Therefore it is important to consider both dependencies to calculate the soil response against earthquakes in order to estimate input motions to buildings. However, it has been difficult to calculate the seismic response of the soil considering both dependencies directly. The author has studied the time domain evaluation of the frequency dependent dynamic stiffness, and proposed a simple hysteretic damping model that satisfies the causality condition. In this paper, this model was applied to nonlinear analyses considering the effects of the strain amplitude dependency of the soil. The basic characteristics of the proposed method were studied using a two layered soil model. The response behavior was compared with the conventional model e.g. the Ramberg-Osgood model and the SHAKE model. The characteristics of the proposed model were studied with regard to the effects of element divisions and the frequency dependency that is a key feature of the model. The efficiency of the model was confirmed by these studies.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.126-131
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• 2007

The Imha watershed is vulnerable to severe erosion due to the topographical characteristics such as mountainous steep slopes. The RUSLE model was combined with GIS techniques to analyze the mean annual erosion losses and the soil losses caused by typhoon "Maemi". The model is used to evaluate the spatial distribution of soil loss rates under different land uses. The mean annual soil loss rate and soil losses caused by typhoon "Maemi"were predicted as $3,450\;tons/km^2/year$ and $2,920\;ton/km^2/"Maemi"$, respectively. The sediment delivery ratio was determined to be about 25% from the mean annual soil loss rate and the surveyed sediment deposits in the Imha reservoir in 1997.

• Water Engineering Research
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• v.7 no.1
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• pp.29-41
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• 2006

The Imha watershed is vulnerable to severe erosion due to the topographical characteristics such as mountainous steep slopes. Sediment inflow from upland area has also deteriorated the water quality and caused negative effects on the aquatic ecosystem of the Imha reservoir. The Imha reservoir was affected by sediment-laden density currents during the typhoon 'Maemi' in 2003. The RUSLE model was combined with GIS techniques to analyze the mean annual erosion losses and the soil losses caused by typhoon 'Maemi'. The model is used to evaluate the spatial distribution of soil loss rates under different land uses. The mean annual soil loss rate and soil losses caused by typhoon 'Maemi' were predicted as 3,450 tons/km2/year and 2,920 ton/km2/'Maemi', respectively. The sediment delivery ratio was determined to be about 25% from the mean annual soil loss rate and the surveyed sediment deposits in the Imha reservoir in 1997. The trap efficiency of the Imha reservoir was calculated using the methods of Julien, Brown, Brune, and Churchill and ranges from 96% to 99%.

• Proceedings of the Korean Geotechical Society Conference
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• 1993.10a
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• pp.63-68
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• 1993

Soil nailing is a method of reinforcing natural deposits of soil with passive inclusions, called nails, of steel or other materials. Its purpose is mainly to increase the tensile and shear strength of the soil mass. This method has been widely used during the last two decades to stabilize steep slopes in several countries (France, Germany, USA, Japan, etc.). The design methods that have been mostly used are Davis method, German method, and French method which are based on limit equilibrium approaches, and Juran method which utilizes the kinematical limit equilibrium design concept. This paper is focussed on the evaluation of the available design methods(especially, the France, Davis and German design methods) through comparison with each different assumption for the failure surface, the concept of failure mechanism and the definition of safety factor. The parametric study to identify the effects of design parameters on the overall factor of safety has also been conducted. By considering the results along with the associated assumptions which have been postulated in the several methods, the applicability of the method for a given soil and nail conditions has been evaluated.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.559-562
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• 2003

The results and discussions of surveyed case site at constructed steel pile in potential acid sulfate soil were as follows. Topography at surveyed site was local alluvial valley and that site soils was classified as BanGog and YuGye series as detailed soil surveyed results in RDA and soil texture was Clay/Clay Loam. Soils pH was neutral, which was average 7.5 but much decreased to average 4.2 after $H_2O_2$ treatment. Organic matter and sulfate ions contents were very rich. The corrosion was severe at ground water fluctuation depth. Deposits colored black were attached to steel pile surface, which because of violent reaction in treatment HCI solution, were guessed as corrosion products (FeS) reduced by sulfate reducing bacteria(SRB). Consequently, main cause was thought microbiologically induced corrosion at this site where there is ground water fluctuation occurring oxidation and reduction reactions in turn and the soil is potential acid sulfate soil.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.579-582
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• 2003

This study is a part of the project to identify water-quality degradation mechanism due to Fe and Mn in the river-bank infiltration system in the Changwon city, Kyungsangnam-Do. Results of hydrogeochemical logging indicated that the matrix of the river bank affects groundwater quality, probably related with the hydraulic conductivities of the different layers of bank deposits. Electric conductivity logging data clearly show various layers of groundwater flows. Further studies are necessary to identify mechanisms of increasing dissolved oxygen contents with depths at some monitoring wells.

• Journal of the Korean Geotechnical Society
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• v.27 no.9
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• pp.13-24
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• 2011

The renowned Terzaghi's one-dimensional consolidation theory is not applicable to quantification of time-rate settlement for highly deformable soft clays such as dredged soil deposits. To deal with this special condition, a non-linear finite strain consolidation theory should be adopted to predict the settlement of dredged soil deposits including self-weight and surcharge-induced consolidation. It is of importance to determine the zero effective stress void ratio ($e_{00}$), which is the void ratio at effective stress equal to zero, and the relationships of void ratio-effective stress and of void ratio-hydraulic conductivity for characterizing non-linear finite strain consolidation behavior for deformable dredged soil deposits. The zero effective stress void ratio means a transitional status from sedimentation to self-weight consolidation of dredged soils. In this paper, laboratory procedures and equipments are introduced to measure such key parameters in the non-linear finite strain consolidation analysis. In addition, the non-linear finite strain consolidation parameters of the Incheon clay and kaolinite are evaluated with the aid of the proposed methods in this paper, which will be used as input parameters for the non-linear finite strain consolidation analyses being performed in the companion paper.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.120-127
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• 2001

Long term earthquake observations at different tunnel sites within a variety of alluvial soil deposits have demonstrated that a circular tunnel is liable to deform in such a way that its two diagonal diameters crossing each other expand and contract alternately. Based on this knowledge, the soil-tunnel interaction and isolation effect for this particular vibration mode is investigated. Interaction effect is considered with the condition of fixed tangential strain between the tunnel and the soil. Isolation effect embodied by covering up the tunnel with isolation materials is discussed as a possible measure for mitigating seismic damage to it. When Poisson`s ratio of isolation material decreases or the shear modulus ratios of the soil to isolation material become large, the isolation effect becomes bigger.

• Journal of the Mineralogical Society of Korea
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• v.1 no.1
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• pp.32-39
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• 1988

The effect of soil forming factors on the pedogenesis of basaltic volcanic ash soils and the influence of allophane material on soil properties have been investigated on 5 chronosequence soils situated from at the near sea coast up to the foot slope of Mt. Halla in Jeju Island. Time seems to be the important soil forming factor which today differentiates soil of the Island. Songag and Donghong soils developed in lower elevations are older and somewhat less influenced by ash shower. However, soils developed at higher elevations, Pyeongdae and Heugag, are rather younger and strongly influence by the ash. It is also proved that the parent materials are very heterogeneous. They mainly are basaltic with some contamination of acidic volcanic ashes and continental aeolian deposits where a considerable amount of quartz encountered in most soils studied. Many physico-chemical properties of soil, such NaF pH, phosphate sorption power, pH and extractable acidity are parameters to differentiate andepts and non-andeptic soils.

• Geomechanics and Engineering
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• v.30 no.3
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• pp.233-246
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• 2022

In this study, the city of Osijek is used as a case study area for low to medium seismicity regions with deep soil over deep geological deposits to determine horizontal PGA values. For this reason, we propose new regional attenuation equations for PGA that can simultaneously capture the effects of deep geology and local soil conditions. A micro-zoning map for the city of Osijek is constructed using the derived empirical scaling equations and compared to all prior seismic hazard estimates for the same area. The findings suggest that the deep soil atop deep geological sediments results in PGA values that are only 6 percent larger than those reported at rock soil sites atop geological rocks. Given the rarity of ground motion records for deep soils atop deep geological layers around the world, we believe this case study is a start toward defining more reliable PGA estimates for similar areas.