• Korean Journal of Soil Science and Fertilizer
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• v.41 no.4
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• pp.273-278
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• 2008

This study was carried out in order to test unsaturated hydraulic conductivity estimation of van Genuchten's and Campbell's models using one-step outflow method through Tempe pressure cell. The undisturbed soil cores (columns) were taken from Ap1, B1 and C horizons of Songjeong series (the fine loamy, mesic family of Typic Hapludults). After the saturated hydraulic conductivity Ks of the cores was determined by constant head method, water outflow rate and retentivity of cores were measured in Tempe pressure cell. Fitted curves by models accorded to measured data except for both end of pressure range. In near-saturated condition, measured water retention characteristics showed a relatively better fitness with Campbell's model than van Genuchten's. The soil unsaturated conductivity estimated by Campbell's model was higher than by van Genuchten's. In Ap1 and B1 horizon, the soil unsaturated conductivities obtained by one-step outflow method went between van Genuchten's and Campbell's hydraulic functions, slightly closer to van Genuchten's. In C horizon, van Genuchten's model had better fitness with the one-step outflow data. Consequently, van Genuchten's model generally had better fitness with measured hydraulic conductivity than Campbell's model at the soil water potential range of -10~-75 kPa, especially in C1 horizon. In near-saturated condition, Campbell's model could be thought as relatively accurate hydraulic model, because of the better fitness of Campbell's model with soil water retention data than van Genuchten's model.

• The Korean Journal of Ecology
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• v.20 no.3
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• pp.175-179
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• 1997

To explanin allopatric distribution of Carpinus cordata and C. laxiflora in the field the effect of soil flooding on photosynthesis and water relations was tested with field grown saplings. Under the flooding condition stomatal conductance of C. laxiflora decreased markedly from day two after flooding treatment and remanined low throughout the experiment. In contrast, flooding had no effect on stomatal conductance of C. cordata throughout the exper iment. The rate of photosynthesis of C. laxiflora was significantly suppressed under flooding conditions, whereas that of C. cordata was not affected in the flooded condition. On day seven after flooding treatment xylem pressure potential of C. laxiflora significantly decreased. Flooding, however, did not have any effect on the xylem pressure potential of C. cordata throughout the experiment. From these findings it is concluded that there is a difference in resistance to flooding between C. cordata and C. laxiflora and that one of the the factors responsible for allopatric distribution in the two species is flooding.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.5
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• pp.43-49
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• 2005

In this study. it was suggested that the elastic model to analyze the behavior of pore water pressure in saturated sand specimen on the condition of non-drainage. The model based on the experiments which were performed for the relationships between the pore water pressure and the grain size of specimen, and effective stress, respectively. The suggested model embodied the pore water and soil grain as separate elastic springs of different stiffness. The springs were joined parallel and the axial strains were restricted to the same deformation. The suggested model was well consistent with the experiments.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.481-489
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• 2006

Two dimensional diffusion model test was conducted to investigate the sedimentation properties and consolidation process of reclaimed ground using dredging coarse soil which is composed of passing amount 20 percentage and 45 percentage of #200 sieve size respectively. The passing amount of #200 sieve size affected on sedimentation properties. The coarse soil which is passing amount of 20 percent showed that the sedimentation structure was layered type and passing amount of 45 percentage was wall-partition type according diffusion distance. Furthermore, the water content of surface and section, and distribution of fine soil were changed according to diffusion distance. and the change amount of pore water pressure and strength property when soil is diffused, segregated and accumulated can be applied efficiently in design of dredging and reclamation.

• Journal of the Korean Institute of Gas
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• v.14 no.6
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• pp.1-6
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• 2010

River crossing pipelines have been being operated with buried depth of 1.2~4m underneath river bottom to prevent buoyance and external impact. River crossing pipelines have to show resistance to soil load and hydrostatic pressure. In this study, structural integrity of the river crossing pipeline subjected to soil load and hydrostatic pressure was evaluated by using FE analyses. Hoop stress increased with increasing buried depth under identical water height in case of without concrete encasement, however, hoop stress decreased with increasing water height under identical buried depth.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.55-64
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• 2003

Desiccation of a soil is basically the removal of water by evaporation, which is controlled by evaporativity and evaporability. Surface evaporation improves the trafficability which is essential for the access of construction equipment in the area reclaimed with soft clay. The existing traditional methods for evaluating evaporation can not account for the deformation of reclaimed soft soils during evaporation. Therefore, a theoretical model for predicting the rate of evaporation from the surface of a deformable material is proposed. The model is based on a system of equations for coupled heat and mass transfer in unsaturated soils. The modified pressure plate extractor test and glass desiccator test were carried out to obtain the soil-water characteristic curve for a deformable soil. The column drying test was conducted to investigate one dimensional water flow, heat flow and evaporation in the surface. A finite difference program was developed to solve the coupled nonlinear partial differential equations, which permit the study of water, vapor and heat flows in the deformable soil. Comparison between measured and simulated values shows a reasonably good matching between the two.

• Journal of the Korean Geotechnical Society
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• v.31 no.6
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• pp.71-82
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• 2015

Recently, due to the expansion of urban infrastructure for the citizen convenience, the shield tunnel construction has increased considering the civil complaints minimization and construction stability. Most shield tunnels are designed based on the assumption of the undrained condition that underground water does not inflow, but they are operated in the field as drained tunnels with drainage facility to drain underground water. Therefore, the drained condition needs to be considered in the shield tunnel design. It is also necessary to consider the weathered granite soil that is widely distributed throughout the country and consequently is encountered in most of construction sites. In this paper, the model test which can control total stress and pore water pressure and simulate the underground tunnel located in the weathered granite soil below ground water level is conducted. Total stress, pore water pressure and an inflow water into an inner pipe were measured using the testing device. Test results showed that the total stress in a drained condition was lower than in an undrained condition because pore water pressure decreased in a drained condition and an inflow water into an inner pipe was proportional to the loading stress in a drained condition. As a result, if a drained condition is considered in the shield tunnel design, the more economical design can be expected because of the stress reduction of the lining.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.399-406
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• 2004

This paper is experimental study on the effect of improved soil strength which was grouted by pressure grouting method for prevent collapse the tunnel's face during excavate tunnel. This study performs to investigate the proper grouting pressure and grouting method through pressure grouting laboratory model tests using loose dense sandy soil using specially designed and fabricated device($180cm{\times}220cm{\times}300cm$) under changing condition of injection in this test The investigation is carried out through measuring the size and shape of grout bulb, elastic modulus by pressure-meter test Elastic modulus was estimated using relation stress with strain which is result the uni-direction compressive strength test for cured grouted bulb under water during 28days. From these test results, the amount of increased elastic modulus of grouted zone was suggested.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.585-592
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• 2003

The purpose of this paper is to investigate purification characteristic of soil-bentonite landfill liner and to develop of desirable liner system. In this study, column tests for soil-bentonite, reactive soil-bentonite and existing bentomat and reactive bentomat were carried out under the high pressure with water and leachate.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.551-558
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• 2001

The horizontal drain method is one of methods improving reclamation ground. This method reduces consolidation time by using drained installed horizontally, and negative pressure is applied on end of these drains by vacuum pump. But, effective negative pressure still wasn't evaluated in applying this method to reclamation ground. To estimate optimum negative pressure, soil box test that make a model the in-situ by installing horizontal drains in the center is performed pressing different vacuum pressure In the laboratory, and the variations in settlement and volume of drained water through the drains during consolidation process were measured. Also, water content with distance from drain and with depth is measured after the test.