• Journal of the Korean GEO-environmental Society
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• v.8 no.2
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• pp.49-55
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• 2007

It is very important to determine the consolidation rate of ground, depending on the progress of time in applying this vertical drain method. Various consolidation analysis solutions capable of forecasting the consolidation rate are being proposed at the moment. However, the degree of consolidation measured from site, has a considerable different from the degree of consolidation which was obtained by the analysis of vertical drain consolidation. This study aims at assessing the applicability and verfication of each consolidation analysis solution by comparing and analyzing the degree of consolidation measured in the field and the degree of consolidation based on the theoretical equation for the analysis of the consolidation of Hansbo, Onoue, Zeng and Xie used as the consolidation analysis solution before the beginning of construction, on the basis of monitored field results and site investigation data as to the deep soft ground in Busan area applied by PBD method.

• Journal of the Korean Geosynthetics Society
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• v.15 no.1
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• pp.47-57
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• 2016

Many researchers reported that artesian pressure exists in thick soft ground of Busan Nakdong river estuary. Artesian pressure in soft ground could affect rate of consolidation, settlement and drainage capasity of prefabricated vertical drain(PVD). This paper investigated consolidation behaviors of soft ground with partially penetrated PVD subjected to artesian pressure. Laboratory tests with 1-dimensional large column equipment and their numerical analyses were carried out. Test results showed that the consolidation settlement of clay ground with artesian pressure was higher than that without artesian pressure. Due to artesian pressure, the dissipation rate of excess pore water pressure was reduced in soft ground with artesian pressure, especially at bottom part of clay ground. Numerical results were in good agreement with experimental test results.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.4
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• pp.338-349
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• 1993

Most of numerical models for studying tide-induced residual currents (TIRC) were to dimensional depth averaged models which were confined to anlayze the horizontal structure of TIRC. In this study, TIRC occurring around a circular island was simulated with the three-dimensional spectral model which employed by the finite difference method in the horizontal direction and the expansion of basis function in the vertical direction. The main results of numerical experiment can be summarized as follows. Firstly. both topographic and nonlinear effect played an important role in the generation of TIRC. Secondly, when the currents were rotary clockwise. the horizontal structure of TIRC appeared to rotate in the same direction. These results were consistent with those of previous studies of two-dimensional numerical models.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.4
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• pp.13-23
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• 1984

The purpose of this paper is to develop a numerical model which can be used to compute the suspended load concentration of which the two-dimensional unsteady diffusion equation is able to be solved by the finite difference method using the implicit scheme. The pick-up rate formula from the bottom used in the open channel as a sink source term and the Coleman's empirical formula for the diffusion coefficient were taken, and especially the hindered settling velocity and the vertical velocity of flow due to the periodical tidal motion were taken into account, while the effects of the variables, such as the horizontal and vertical velocities of flow, tidal range, the settling velocity and hindered settling, on the suspened load concentrations have been discussed, comparing the results obtained from the different cases in the simulation conditions.

• Journal of the Korean Geotechnical Society
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• v.27 no.4
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• pp.77-87
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• 2011

To investigate the effect of drainage spacing and smear on the rate of consolidation and the efficiency of vertical drain method, a series of consolidation tests with a large consolidation chamber and special equipment for inserting mandrels were conducted. As the smeared region increases, total settlement in over-consolidated clay increases whereas apparent change in settlement does not appear in normally consolidated clay. Vertical drain generally accelerates the rate of consolidation, while it could also deteriorate the efficiency of vertical drain method even for the decreasing drainage length and spacing ratio.

• Journal of Korea Water Resources Association
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• v.55 no.11
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• pp.955-967
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• 2022

Existing particle tracking models predict vertical displacement of particles based on the terminal settling velocity in the stagnant water. However, experimental results of the present study confirmed that the settling velocity of particles is influenced by the turbulence effects in turbulent flow, consistent with the previous studies. The settling velocity of particles and turbulent characteristics were measured by using PTV and PIV methods, respectively, in order to establish relationship between the particle settling velocity and the ambient turbulence. It was observed that the settling velocity increase rate starts to grow when the particle diameter is of the same order as Kolmogorov length scale. Compared with the previous studies, the present study shows that the graphs of the settling velocity increase rate according to the Stokes number have concave shapes for each particle density. In conclusion, since the settling velocity in the natural flow is faster than in the stagnant water, the existing particle tracking model may estimate a relatively long time for particles to reach the river bed. Therefore, the results of the present study can help improve the performance of particle tracking models.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.28 no.4
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• pp.337-346
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• 1992

Hydroacoustic surveys were conducted in the East China Sea, in the summers of 1990-1991 to investigate the distribution and migration behavior of fish, such as the diel changes in the distributions of fish, the thermoselection behavior of fish, and the fish reactions to a surveying vessel. The hydroacoustic observations were taken with a scientific echo sounder operating at 50kHz and a microcomputer-based echo processor. Fish samples were collected by bottom trawling and temperature was measured with a DBT system. The patterns of fish distributions were compared with the vertical profiles of water temperature. The results obtained can be summarized as follows: 1. The time series of hydroacoustic observations on the downward migration at dawn in the central region of East China Sea showed that the migration rate was 0.24 m/min. In this region, most of the fish collected by bottom trawling during the surveys were squid (Photologio edulis f. budo) and horse mackeral (Trachurus japonicus). 2. The hydroacoustic observations, which together associated with temperature data, indicated that squid and horse mackeral concentrated nocturally in a narrow vertical band of thermocline, particularly in summer when the survey region was strongly stratified. This result suggest that the nocturnal vertical distribution of these species evidently is controlled by temperature. 3. When the survey vessel, that is running at a speed of 11 knots, has suddenly stopped, the fish which concentrated beneath the transducer showed a strong avoidance reaction in the form of rapid downward migration. After a few minutes, the descending reaction disappeared and the fish slowly began the upward migration toward their original swimming positions. Trawl data suggest that the fish, which showed the avoidance reaction, was Liparis tessellatus.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.3
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• pp.53-60
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• 1988

The behavior of plane buoyant jet issuing vertically upwards into cross flow is analysed by experiments and integral scheme. The integral scheme is based on the self similarity and characteristic length scales to governing equations of continuity, momentum and constituent transport equation, in the horizontal and vertical flow region, respectively. Jet trajectories and the temperature distributions of jet centerlines obtained from experiments are analysed for various velocity ratios and densimetric Froude numbers. It was found that the analytical results about the trajectories and temperatures of jet center lines agree with the experiments and can be expressed as power laws.

• Journal of the Korean Geosynthetics Society
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• v.7 no.4
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• pp.37-45
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• 2008

A pilot test using environmentally friendly drains, was carried out to evaluate their applicability potential in the field. The pilot test site was divided into 5 different areas, with several combinations of vertical and horizontal drains installed for evaluation. Conventional natural fiber drains (FDB), new developed straw drain board (SDB) and plastic drain board (PDB) were used as vertical drains, while sand and fiber mats were used as horizontal drains. Surface settlement rates and excess pore pressure generation/dissipation tendency of PDB and FDB are almost identical except those of SDB. Cone tip resistance obtained from cone penetration test measured at the end of 1st consolidation stage for upper soft layer definitely increased irrespective of types of vertical drains. The monitoring and site investigation test data obtained at the pilot test site prove the vertical natural fiber drains can be used as substitutes of conventional plastic and sand material.

• Journal of the Korean GEO-environmental Society
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• v.7 no.3
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• pp.77-83
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• 2006

The purpose of this study is to analyze lateral displacement behavior of clay layers in case of the banking in soft ground through model tests. Seven model tests varying with thickness of soft clay and loading velocity are performed to correlate between ground heaving and loading velocity. In case of low loading velocity, vertical settlement below loading plate and small ground heaving are obviously observed. In case of the high loading velocity, it is shown that both soil displacement at the end of a loading plate and surface heaving are large. In addition, the calculated displacements show good agreement with three cases of field measurements in clay with high moisture contents so that we can predict the range of heaving area and the amount of heaving.