• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.39 no.5
• /
• pp.579-586
• /
• 2019

Pilot Point Method (PPM) is one of the popular methods to search hydraulic conductivities in the inverse method using groundwater flow equations. In this study, the Simultaneous Search based Pilot Point Method (SSBM) was applied with diverse information (e.g. hydraulic heads and/or tracer concentration) applications over previously developed sensitivity based Pilot Point Method (e.g. D-optimality based Pilot Point Method: DBM). In the case of DBM, due to the minimized the variance size, tracer concentration can be recognized as a tool to control the searching space of hydraulic conductivities. SSBM reduced the procedure of hydraulic conductivity searching, though it produced more variance for exploring hydraulic conductivities. In addition, SSBM was dependent on the initial hydraulic conductivity values for search finalized hydraulic conductivities. When tracer concentration was applied, searching hydraulic conductivities was more preferable than only when hydraulic head was applied. Applications of various data for searching hydraulic conductivities is recommended as a more efficient way.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1998.03a
• /
• pp.307-314
• /
• 1998

• KCID journal
• /
• v.5 no.1
• /
• pp.63-74
• /
• 1998

This study was performed to evaluate the hydraulic conductivity of sand-bentonite mixtures according to 8 kinds of the bentonite content using the reassembled air-entry permeameter. Results obtained are as follows: 1. The maximum dry density and optimum m

• Journal of Korea Water Resources Association
• /
• v.30 no.6
• /
• pp.699-708
• /
• 1997

The effective unsaturated hydraulic conductivity in stratified soils is evaluated using a three-dimensional stochastic approach. Because of the disparity of the correlation scales in a stratified soil, the general stochastic equations are simplified. This allows analytical evaluation of generic expressions for the effective hydraulic conductivities. Simple asymptotic expressions, valid at particular ranges(wetting front, drying condition, wetting condition) of the mean flow characteristics, are also derived. An example of applying the derived theoretical result to a imaginaryl clay soil is presented. It reveals found that the effective unsaturated hydraulic conductivity showed large-scale hysteresis. Such large-scale hysteresis was produced by the spatial variability of hydraulic soil properties rather than hysteresis of the local parameters. In addition the results show that the effective hydraulic conductivities were larger in the case of accommodating heterogeneity of soil preperties rather than neglecting heterogeneity of soil properties.

• Journal of Korea Soil Environment Society
• /
• v.2 no.3
• /
• pp.59-67
• /
• 1997

To investigate the effects of organic matter and soil depth on soil water flow in a multi-layered soil, the saturated hydraulic conductivities(Ksat) were measured from the single- and multi-layered soil columns, that the soils were mixed with the oven-dried cow manure compost(CMC) at 4 different ratios such as 0, 2, 4, and 6% on a weight basis. The measured hydraulic conductivities(Ksat) were compared with theoretical hydraulic conductivity (Keff calculated by Jury's equation of effective hydraulic conductivity. In the single layered soil column saturated hydraulic conductivities(Ksat) were significantly decreased with increasing the application rate of compost. In the multi-layered the soil columns Ksat was also decreased with increasing rate of compost and soil depth. Calculated Keff showed the similar results of Ksat as obtained from the measured Ksat, whereas steadily increased with increasing soil depth. Therefore, modification of Jury's equation should be required to adapt theoretical Keff for Held application.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.7
• /
• pp.47-55
• /
• 2007

In this study, applicability of electrical conductivity monitoring technique for containment barrier such as soil-bentonite wall was evaluated. Laboratory tests including permeability tests and column tests were performed to understand variations in electrical conductivity at different bentonite contents, hydraulic conductivities, and heavy metal concentrations. The electrical conductivity of compacted soil-bentonite mixtures was found to increase proportionally with bentonite content. Accordingly, the hydraulic conductivity of compacted soil-bentonite mixtures which decreases linearly with increasing bentonite content was found to have an inversely proportional relationship with the electrical conductivity. In column tests, electrical conductivity breakthrough curves and concentration breakthrough curves were simultaneously obtained. These results indicated that electrical conductivity measurement can be an effective means of detecting heavy metal transport at the desired locations within barriers and verifying possible contaminant leakage. Experimental results obtained from this study showed that the electrical conductivity measurement can be a promising tool for monitoring of containment barrier.

• Economic and Environmental Geology
• /
• v.46 no.3
• /
• pp.215-220
• /
• 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 Soil and Groundwater Environment
• /
• v.16 no.4
• /
• pp.1-9
• /
• 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.

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

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