• Journal of Korean Society of Environmental Engineers
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• v.22 no.5
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• pp.927-938
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• 2000

When microorganism is injected into porous medium such as soils along with appropriate substrate and nutrients, biomass retained in the soil pore. Soil pore size and shape are varied from the initial condition as a result of biofilm formation, which make hydraulic conductivity reduced. In this research, hydraulic conductivity reduction was measured after microorganism are inoculated and cultured with synthetic substrates and nutrients. Biomass-soil mixture was evaluated its applicability to the field condition as an alternative liner material in landfill by measuring hydraulic conductivity change after repetitive freeze-thaw cycles. Resistance of biofilm to chemical solution and degree of biodegradation were measured through column test.

• Geomechanics and Engineering
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• v.32 no.4
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• pp.445-452
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• 2023

Temperature is one of the important factors affecting the permeability of water in the soil. In the present study, the impact of water temperature on hydraulic conductivity (k) with and without coarse aggregations by considering six types of soils was analyzed. Moreover, the effect of sand and gravel presence in the soil was investigated through the infiltration based on constant and inconstant water head experiments. Results indicated that by increasing the water temperature, adding gravel to sandy soil caused the hydraulic conductivity to raise. It is supposed that the gravel decreased the contact surface between the water and the soil aggregates. It is deduced that due to decreasing kinetic energy, k tends to have lower values. Furthermore, adding the sand to sandy silt-clay soil showed that the sand did not have a marginal effect on the variation of k since the added sand cannot increase the contact surface like gravel. Finally, increasing the main diameter of the soil will increase the effect of the water temperature on hydraulic conductivity.

• Tunnel and Underground Space
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• v.27 no.2
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• pp.100-108
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• 2017

As a measure of the combined effect of fracture geometry, the fabric tensor parameters could quantify the status of the connected fluid flow paths in discrete fracture network (DFN). The correlation analysis between fabric tensor parameters and hydraulic properties of the 2-D DFN was performed in this study. It is found that there exists a strong nonlinear relationship between the directional conductivity and the fabric tensor component estimated in the direction normal to the direction of hydraulic conductivity. The circular radial plots without significant variation of the first invariant ($F_0$) of fabric tensor for different sized 2-D DFN block are a necessary condition for treating representative element volume (REV) of a fractured rock mass. The relative error (ER) between the numerically calculated directional hydraulic conductivity and the theoretical directional hydraulic conductivity decreases with the increase in $F_0$. A strong functional relation seems to exist between the $F_0$ and the average block hydraulic conductivity.

• Journal of Soil and Groundwater Environment
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• v.16 no.4
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• pp.1-9
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• 2011

Bentonite has been generally used as vertical cutoff barrier material and reported to have several problems regarding its low workability, drying shrinkage cracking by particle cohesion, and ineffective waterproof ability under sea water condition. In this study, the particle sealant, the furnace slag coated by the mixture of bentonite, sepiolite and guargum, was developed to compensate these weak points and the hydraulic conductivity of the particle sealant was evaluated. Drying shrinkage cracking and swelling index was estimated to find the optimal mixing ratio of bentonite, sepiolite and guargum. The hydraulic conductivity of the particle sealants having different amount of sealant (bentonite-sepioliteguargum mixture) coating the furnace slag was estimated using the rigid wall permeameter and flexible wall permeameter. The results showed that drying shrinkage cracking was not found in the bentonite-sepiolite mixture with 20% sepiolite contents and the results from free swelling tests for the sealant having 1 : 0.025, 1 : 0.05 and 1 : 0.075 of weight ratios of bentonite-sepiolite mixture and guargum under simulated sea water condition were higher than those for the bentonitesepiolite mixture without guargum under tap water condition. These three sealants were coated on the furnace slag with 50% and 60% of sealant in the particle sealant and the hydraulic conductivity was estimated. In the cases of the particle sealants having 20% sepiolite in the bentonite-sepiolite mixture and 1 : 0.075 weight ratio of the bentonite-sepiolite mixture and guargum, the hydraulic conductivity from the rigid wall permeameter was below $1.0{\times}10^{-7}$ cm/sec under simulated sea water condition. The hydraulic conductivity of the particle sealant having $1.0{\times}10^{-6}$~$1.0{\times}10^{-7}$ cm/sec by the rigid wall permeameter was estimated using the flexible wall permeameter and found to be below $1.0{\times}10^{-7}$ cm/sec.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2369-2379
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• 2013

The Soil-Water Characteristics Curve (SWCC) is affected by the initial density of soil under unsaturated condition. Also, the characteristic of hydraulic conductivity is changed by the initial density of soil. To study the effect of initial density of unsaturated soil, SWCC and the Hydraulic Conductivity Function (HCF) of Jumoonjin sand with various relative densities, 40%, 60% and 75% were measured in both drying and wetting processes. As the results of SWCC estimated by van Genuchten (1980) model, the parameter related to Air Entry Value(AEV), ${\alpha}$ in the wetting process is larger than that in drying process, but the parameters related to the SWCC slope, n and the residual water content, m are larger than those in wetting process. The AEV is increased or Water Entry Value (WEV) is decreased with increasing the relative density of sand. The AEV is larger than the WEV at the same relative density of sand. As the results of HCF estimated by van Genuchten (1980) model which is one of the parameter estimation methods, the unsaturated hydraulic conductivity maintained at a saturated one in the low level of matric suctions and then suddenly decreased just before the AEV or the WEV. The saturated hydraulic conductivity in drying process is larger than that in wetting process. The saturated hydraulic conductivity is decreased with increasing the relative density of sand in both drying and wetting processes. Also, the hysteresis in unsaturated HCFs between drying and wetting process was occurred like the hysteresis in SWCCs. According to the test results, the AEV on SWCC is decreased and the saturated hydraulic conductivity is increased with increasing the initial density. It means that SWCC and HCF are affected by the initial density in the unsaturated soil.

• 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.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.09a
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• pp.75-78
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• 2001

Authors evaluated the feasibility of a permeable reactive biobarrier (PRB) treated with biofilm formed by Beijerinckia indica (B.indica). This study focused on evaluating two potentials of B.indica for the requirements of PRB: reducing the hydraulic conductivity and degrading the polycyclic aromatic hydrocarbons (PAHs). The hydraulic conductivity was estimated by rigid wall column test and finally the values were converted to the values of intrinsic permeability. The nutrient solution was passed through the biobarrier column to activate the bacterium and then leachate was in turn carried into the column to evaluate the durability of the biobarrier. Phenanthrene was selected as a representative substance of PAHs. The ability of degrading phenanthrene by B.indica was evaluated by two-phase partitioning bioreactor after estimating the possibility with two pretests: observing the colony formation and the optical density on glucose-free medium containing phenanthrene. With the results, B.indica produced large amount of strongly adhesive exopolysaccharides (EPS) and reduced several orders of magnitude of the hydraulic conductivity after 2 weeks of cultivation. Furthermore, about 1000mg/1 of phenanthrene could be degraded by B.indica in the two-phase partitioning bioreactor. In conclusion, the application of the bacterium, B.indica, was found to have a potential role of a PRB to retain and remove contaminants in porous media.

• Ocean Systems Engineering
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• v.3 no.1
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• pp.9-34
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• 2013

Submarine pipelines encounter significant wave forces in shallow coastal waters due to the action of waves. In order to reduce such forces (also to protect the pipe against anchors and dropped objects) they are buried below the seabed. The wave force variation due to burial depends on the engineering characteristics of the sub soil like hydraulic conductivity and porosity, apart from the design environmental conditions. For a given wave condition, in certain type of soil, the wave force can reduce drastically with increased burial and in certain other type of soil, it may not. It is hence essential to understand how the wave forces vary in soils of different hydraulic conductivity. Based on physical model study, the wave forces on the buried pipeline model is assessed for a wide range of wave conditions, for different burial depths and for four types of cohesion-less soils, covering hydraulic conductivity in the range of 0.286 to 1.84 mm/s. It is found that for all the four soil types, the horizontal wave force reduces with increase in depth of burial, whereas the vertical force is high for half buried condition. Among the soils, well graded one is better for half buried case, since the least vertical force is experienced for this situation. It is found that uniformly graded and low hydraulic conductivity soil attracts the maximum vertical force for half buried case. A case study analysis is carried out and is reported. The results of this study are useful for submarine buried pipeline design.

• Economic and Environmental Geology
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• v.46 no.3
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• pp.215-220
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• 2013

We estimated the hydraulic conductivity of the sediments using constant-head permeability tests and electrical resistivity measurements with Jumoonjin standard sand of a uniform size and glass beads of different grain sizes. In this study, we determined the variations of the porosity, the hydraulic conductivity, and the resistivity in case 1 (changing the packing of the Jumoonjin standard sand) and in case 2 (varying the size of the glass beads). The results of case 1 showed that the hydraulic conductivity decreased with an increase in the electrical resistivity. This occurred because the sand grain while packing became rhombohedral with the a decrease of both the pore size and porosity. The results of the case 2 showed that the hydraulic conductivity increased due to the increase in the pore size as caused by the increased glass bead size. In addition, the porosity decreased and the electrical resistivity increased. Therefore, the relationship between the hydraulic conductivity and the electrical resistivity is negatively proportional as regards the grain packing with a change from cubic to rhombohedral whereas this relationship is positively proportional to the increase in the grain size.

• Journal of Korea Water Resources Association
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• v.49 no.9
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• pp.741-748
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• 2016

Laboratory scale model was constructed for open-cut riverbed infiltration experiment and four kinds of media were selected, medium sand, sand, volcanic rock, and gravel, for the experiment. Hydraulic conductivity for each medium and flow rate from the collecting pipe with functional screen were estimated from the experiment. Modified hydraulic conductivity scenarios considering turbid water (30~50 NTU) were applied in Visual MODFLOW modeling to analyze the effects of turbid water on the flow rate. Twenty-two scenarios were generated considering prticles in turbid water and applied to each medium cases in MODFLOW modeling. The minimum error was occurred when the gravel medium had 20% less hydraulic conductivities for the third layer-depth from the top and clay particles in turbid water might play a role in adsorption process to the surface of volcanic rock (2~5 mm). For medium sand case the error was also quite small when the mediumhas 5% less hydraulic conductivities for the second layer-depth from the top.