• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.6
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• pp.79-92
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• 2016

The objective of this study is to classify the types of rural areas (138 $si{\cdot}gun$) considering settlement environment by Decision Tree Method (CHAID). The CHAID method was used for decision tree algorithm and the seven dependant variables and 5 explanatory variables were selected, respectively. By decision tree method, rural areas were finally classified into six groups through three separate processes. City area, lower area in aging rate and higher area in farmland area ratio was analyzed to be relatively rich rather than other area in the case of settlement environment index. In the future, this study will be able to utilize as a reference to the planning of rural development projects.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.1
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• pp.101-107
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• 2014

It has been known that Terzaghi's consolidation theory is not well consistent with the consolidation phenomenon on the soft clay ground, but this theory has still been adopted normally in practice because there is no method for estimating the consolidation settlement and rate easier than Terzaghi's theory. It is impossible to map whole part of consolidation settlement vs time curve to the curve of Terzaghi'z average degree of consolidation. If the primary consolidation and the secondary compression are happened same time, it would be useless of trying to find the end of primary consolidation, but it is needed for using Terzaghi's theory that the end of consolidation is determined to the time of beginning consistency between the final settlement analyzed with curve fitting and the experimented consolidation settlement.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.2
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• pp.64-74
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• 2004

In order to accelerate the rate of consolidation settlement, to reduce settlement, and to increase bearing capacity for soft ground under quay wall, sand compaction pile method (SCP) has widely been applied. Improved ground is composite ground which is consisted of the sand pile-surrounding clayey soil. As caisson and upper structures are installed on SCP composite ground, the settlement is compositively occurred by elastic compression of sand compaction piles and also consolidation of the surrounding clay ground. In this study, the combined settlement model is proposed to predict the settlement of SCP composite ground in basis of elastic theory for sand compaction pile and consolidation theory for marine soft clay. Optimization technique was performed based on back-analysis so that real coded genetic algorithm was applied to estimate the parameters of the proposed settlement model. Case analysis was carried out for a domestic SCP composite ground to examine the applicability of the proposed prediction technique.

• Geomechanics and Engineering
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• v.8 no.2
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• pp.187-220
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• 2015

Soil disturbance induced by installation of mandrel driven vertical drains decreases the in situ horizontal hydraulic conductivity of the soil in the vicinity of the drains, decelerating the consolidation rate. According to available literature, several different profiles for the hydraulic conductivity variation with the radial distance from the vertical drain, influencing the excess pore water pressure dissipation rate, have been identified. In addition, it is well known that the visco-plastic properties of the soil also influence the excess pore water pressure dissipation rate and consequently the settlement rate. In this study, a numerical solution adopting an elastic visco-plastic model with nonlinear creep function incorporated in the consolidation equations has been developed to investigate the effects of disturbed zone properties on the time dependent behaviour of soft soil deposits improved with vertical drains and preloading. The employed elastic visco-plastic model is based on the framework of the modified Cam-Clay model capturing soil creep during excess pore water pressure dissipation. Besides, nonlinear variations of creep coefficient with stress and time and permeability variations during the consolidation process are considered. The predicted results have been compared with V$\ddot{a}$sby test fill measurements. According to the results, different variations of the hydraulic conductivity profile in the disturbed zone result in varying excess pore water pressure dissipation rate and consequently varying the effective vertical stresses in the soil profile. Thus, the creep coefficient and the creep strain limit are notably influenced resulting in significant changes in the predicted settlement rate.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.5
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• pp.667-676
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• 1995

Settlement, recruitment, growth and production of Mactra venerifomis were investigated at Kunsan tidal flat located in the west coast of Korea from lune 1993 to May 1994. High density of planktonic larvae of M. veneriformis was observed between the mid and early July in 1993. The size of the newly settled larvae ranged from 250 to 350um in shell length with mean density of 601$inds.\cdot m^{-3}$. Recruitment of M. veneriformis larvae was occurred mainly in the mid June to mid July 1993. The larvae have no substratum preference during the larval settlement phase. Mortality of larval was affected by environment (substratum, exposure time, density of adult clams). After settlement they grew until November, and stopped growing in winter from December. The estimated turnover rate of M. veneriformis larvae was estimated as high as 4.91 and 4.94. Annual production of the 0-age group was estimated to be 2,900g $m^{-2}\;\cdot\;yr^{-l}$, which was relatively high compared with those of other age groups.

• Journal of the Society of Disaster Information
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• v.18 no.4
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• pp.706-712
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• 2022

Purpose: In this study, field experimental research was conducted to analyze the settlement characteristics of soft ground in the central inland region of Korea and use it in practice. Method: The design predicted values and comparative analysis were performed using the ten settlement measurement data actually measured in the field experiment. For the design prediction value, Terzaghi's one-dimensional consolidation settlement analysis was used. In the experiment, the surface subsidence plate was used for field measurement. Result: The settlement behavior of the predicted value and the actual value was generally similar, but in the settlement value, the actual settlement value showed a settlement behavior of 30% or less compared to the predicted settlement value. The rate of consolidation settlement in this study area was in the range of 9.6% to 27.0%, and the average value was 18.21%. It is analyzed that the prediction of the settlement amount of the silty soils distributed in the inland plains of the central region of Korea can be relatively overestimated. Conclusion: It is judged that precise ground investigation and detailed prediction are necessary because there is a possibility of over-design in the design for predicting the amount of settlement of the silty soils distributed in the inland plains of the central region of Korea.

• The Korean Journal of Malacology
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• v.30 no.4
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• pp.343-351
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• 2014

We determined the effects of neuroactive compounds known as synthetic larval settlement inducers on the settlement of the Pacific oyster C. gigas pediveliger on the larval collector. Six types of the inducers, serotonin (5-HT), ${\gamma}$-amino butyric acid (GABA), L-3,4-dihydroxyphenylalanine (L-DOPA), norepinephrine, epinephrine and methyl bromide (MB) were tested. All the chemicals induced larval settlement, MB being the most effective with settlement rate of $42.7{\pm}2.7%$, followed by GABA ($35.4{\pm}2.0%$), 5-HT ($29.1{\pm}2.2%$), L-DOPA ($19.2{\pm}2.1%$), epinephrine ($15.2{\pm}0.9%$), and norepinephrine ($11.0{\pm}1.2%$). The chemicals ${\gamma}$-amino butyric acid and methyl bromide were also better in terms of settled density on the collector with their respective density of $1.97{\pm}1.42$ and $2.37{\pm}1.86ind/cm^2$, reminiscent of being most effective candidates for a larval settlement inducer in the oyster hatchery.

• The Korean Journal of Malacology
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• v.29 no.2
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• pp.139-146
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• 2013

We determined the effects of neuroactive compounds known as synthetic larval settlement inducers on the settlement of the Pacific oyster C. gigas pediveliger on the larval collector. Six types of the inducers, serotonin (5-HT), ${\gamma}$-amino butyric acid (GABA), L-3,4-dihydroxyphenylalanine (L-DOPA), norepinephrine, epinephrine and methyl bromide (MB) were tested. All the chemicals induced larval settlement, MB being the most effective with settlement rate of $42.7{\pm}2.7%$, followed by GABA ($35.4{\pm}2.0%$), 5-HT ($29.1{\pm}2.2%$), L-DOPA ($19.2{\pm}2.1%$), epinephrine ($15.2{\pm}0.9%$), and norepinephrine ($11.0{\pm}1.2%$). The chemicals ${\gamma}$-amino butyric acid and methyl bromide were also better in terms of settled density on the collector with their respective density of $1.97{\pm}1.42$ and $2.37{\pm}1.86\;ind/cm^2$, reminiscent of being most effective candidates for a larval settlement inducer in the oyster hatchery.

• Journal of the Korean GEO-environmental Society
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• v.8 no.5
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• pp.31-38
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• 2007

The practical design method on sandmat uses a drain length, rate of consolidation settlement and permeability of sand as a major design factors. And, on the basis of this design process, it has been installed beneath the embankment with same thickness. However, the possibility the underestimation on the thickness of sandmat and the delayed drain have been pointed out by several authors caused by a differential settlement at the center and the end of embankment. In this study, therefore, the effect of the differential settlement on the thickness of sandmat and delayed drain through the numerical analysis of embankment was analyzed. As a result, a substantial sandmat thickness becomes small and the possibility of the delayed drain can be certified because of the development of differential settlement at the center and ends of embankment. As a countermeasure to overcome this problem, the applicability of the mound type sandmat was also investigated by the numerical method. It can be concluded that it maintains the designated substantial sandmat thickness throughout consolidation process, and is useful method to maintain the drain capacity. Especially, the mound type sandmat is effective method for a construction site where can cause a differential settlement such as embankment. Furthermore, it has to be designed on the basis of the accurate prediction of consolidation settlement as well as rate of consolidation settlement, drain length and permeability of sand.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.888-895
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• 2009

Compaction is a process of increasing soil density using physical energy. It is intended to improve the strength and stiffness of soil. In embankment, degree of compaction affects the construction time, money, also method of soil improvement. In large scale embankment project, difficulties of embankment should change due to uncertainty of settlement. So it is very important to predict the final settlement and factor of safety induced by embankment. In many construction site, there are primarily design of high embankment using in-situ soil. Therefore numerical analyses are necessary for valid evaluation of the settlement prediction. But due to the construction cost and schedule, there were lacking in properties of soil and also limited number of in-situ test were performed. So we proposed the method that can easily estimate the proper soil parameters and suggest the proper method of numerical analysis. From this, two-dimensional finite-difference numerical analysis was conducted to investigate the settlement and factor of safety induced by embankment with various case of compaction rate and embankment height.