• Journal of the Korean Geotechnical Society
• /
• v.36 no.6
• /
• pp.5-15
• /
• 2020

This study deals with the use of porewater pressure transducers to evaluate the stability of a fill dam through the correlation between the porewater pressure and water level. As a result of performing principal component analysis on a total of eight porewater pressure transducers installed in the fill dam, they were distributed into three groups. It was found to be distributed as internal, external, and top based on seepage line in the dam body. The correlation coefficient between porewater pressures and water level in group A located inside the seepage line indicated 0.94 to 1.00 and they are showing a strong positive linear relationships. It indicates that maintenance of the dam is required by the porewater pressure transducers of the group A. In addition, a linear regression analysis was performed with the determination coefficients of the group A of 0.89 to 0.99. It was found that the pore water pressure can be predicted and the stability of the dam can be evaluated by comparing it with the currently measured values when the water level is fixed as an explanatory variable.

• The Journal of Engineering Geology
• /
• v.31 no.2
• /
• pp.199-209
• /
• 2021

This paper is written to evaluate the ground stability according to the construction of Jeju 2nd airport. Sumgol is the unique characteristics of Jeju soil, which is used to evaluate the ground stability of the airport. The research contents are as follows. 1) The geotechnical characteristics for Jeju 2nd airport was analyzed, and the Sumgol and geotechnical properties were calculated based on the existing geotechnical survey data. 2) The divided sections of Jeju 2nd airport were modeled to evaluate the ground stability after determining the section (runway and airport facilities) which have the different soil and loading properties. 3) The stability and deformation ranges of the airport ground were identified through numerical analysis. The entire airport was divided into three sections to analyze the stability of Jeju 2nd airport, and calculated the stresses, settlements, and strains of each section by computer numerical analysis modeling. For modeling, the ground and load conditions were examined, also pavement conditions for each airport ground section were examined. From the analysis results of each section according to the ground conditions, the vertical settlements were analyzed as 0.11~0.18 m and the sum of effective stress and pore water pressure were 92.75~445 kPa. These results were made by taking into account the Sumgol of the bottom ground without reinforcement, also the soil strength parameters of the airport ground were reduced for computer modeling, Therefore, if proper reinforcements are applied to the ground of Jeju 2nd airport, sufficient airport ground stability can be secured.

• Applied Chemistry for Engineering
• /
• v.18 no.3
• /
• pp.245-250
• /
• 2007

Adsorption characteristics of 1,2-dichlorobenzene on the surface of heat treated silica gel were determined by the moment analysis. The heat treatment of the silica gel was performed at temperatures of 150, 500, and $800^{\circ}C$ and pulse-response of 1,2-dichlorobenzene was measured in a gas chromatograph equipped with thermal conductivity detector (TCD) using the packed column. Equilibrium adsorption constants and isosteric heat of adsorption were recorded the highest value at $500^{\circ}C$. This might be due to the increase of interaction between silica surface and 1,2-dichlorobenzene as the decrease of OH concentration and moisture by increase of heating temperature. Axial dispersion coefficient calculated by the moment method was about $0.046{\times}10^{-4}{\sim}1.033{\times}10^{-4}m^2/sec$ and pore diffusivity of heat treated silica gel at $500^{\circ}C$ measured the lowest value. Because heat treating at $800^{\circ}C$ caused the specific surface area to reduce, equilibrium adsorption constants and isosteric heat of adsorption were decreased.

• Applied Chemistry for Engineering
• /
• v.20 no.3
• /
• pp.279-284
• /
• 2009

The formation of mesoporous pores in the microporous mordenite crystals was performed by controlled silica extraction on alkaline treatment. Inner tunable mesopore size could be controlled by changing the concentration of alkaline solution. The pore structure of mordenite zeolite was studied by instrumental analysis after alkaline-treatment. To obtain the cage type mesopores, Ti-coating on the ourside mordenite crystals before alkaline treatment was investigated to be the most effective. Polymeric chiral salen Co (III) complexes were successfully encapsulated in mesoporous mordenite zeolite by "ship-in-a-bottle" method. The heterogeneous catalyst could be applied in asymmetric ring opening of epichlorohydrine by water. It showed very excellent enantioselectivity with a high yield in the catalysis.

• Korean Journal of Soil Science and Fertilizer
• /
• v.47 no.2
• /
• pp.113-119
• /
• 2014

Arsenic and its compounds which is one of the most toxic elements that can be found naturally on earth in small concentrations are used in the production of pesticides, herbicides, and insecticides. Most arsenic that cannot be mobilized easily when it is immobile is also found in conjunction with sulfur in minerals such as arsenopyrite (AsFeS), realgar, orpiment and enargite. In this investigation we observed the leaching of arsenic in soils amended with several levels of gravel size of arsenopyrite collected from a road construction site. Soil and gravel size of arsenopyrite were characterized by chemical and mineralogical analyses. Results of XRF analysis of arsenopyrite indicated that the proportion of arsenate was 0.075% (wt $wt^{-1}$) while the maximum amount of arsenic in soil samples was 251.3 mg $kg^{-1}$. Cumulative amounts of effluent collected from the bottom of the soil column for different mixing rate of the gravel were gradually increased where proportion of the gravel mixed was greater than 70% whereas the effluent was stabilized to the maximum after approximately 45 pore volumes of effluent or greater were collected. The arsenic in the effluent was recovered from the soil columns in which the proportion of arsenopyrite gravel was 60% or greater. The total amount of arsenic recovered as effluent was increased with increasing proportion of gravel in a soil, indicating that the arsenic in the effluent was closely related with gravel fraction of arsenopyrite.

• Polymer(Korea)
• /
• v.36 no.6
• /
• pp.739-744
• /
• 2012

In this work, we prepared the carbons from synthesized styrene-acrylonitrile carbon precursor. The prepared carbons were chemically activated, and then the activated SAN-based carbons were named as A-SANs. The activations were carried out at different temperatures to investigate the effect of activation temperature on the surface and electrochemical properties of the activated SAN-based carbons for using as an electrode of electric double layer capacitors (EDLC). The characteristics of A-SAN were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area and pore size analysis. Also, the electrochemical behaviors were observed by cyclic voltammetry and galvanostatic charge-discharge method. From the results, the A-SAN 700 showed excellent electrochemical property and the highest specific capacitance, but these properties decreased when the activation temperature was above $700^{\circ}C$. This is due to the fact that the activation at a temperature over $700^{\circ}C$ causes deformation of micropore structures.

• Journal of the Korean GEO-environmental Society
• /
• v.15 no.1
• /
• pp.13-23
• /
• 2014

Geotechnical evaluation on the reactive drain pile which can achieve simultaneously both the soft ground improvement and the remediation of contaminated pore water in reclamation site was performed. Applicability of steel-making slag used as a inside reactive material was confirmed. To investigate the consolidation characteristics of the soft ground improved by reactive drain pile, testing devices to form and install the reactive drain pile were developed and laboratory tests were performed according to the existence of outside sand drain and the length of impermeable barrier. Test results showed that the consolidation time was decreased as the shortening of impermeable barrier. However, the effect of outside sand drain on consolidation time was dominant compared with the length of impermeable barrier.

• Geomechanics and Engineering
• /
• v.13 no.1
• /
• pp.1-23
• /
• 2017

A coupled liquid-gas-solid three-phase model, linking two numerical codes (TOUGH2/EOS3 and $FLAC^{3D}$), was firstly established and validated by simulating an in-situ air flow test in Essen. Then the coupled model was employed to investigate responses of multiphase flow and soil skeleton deformation to compressed air or freshwater injection using the same simulation conditions in an aquifer of Tianjin, China. The simulation results show that with injecting pressurized fluids, the vertical effective stress in some area decreases owing to the pore pressure increasing, an expansion of soil skeleton appears, and land uplift occurs due to support actions from lower deformed soils. After fluids injection stops, soil deformation decreases overall due to injecting fluids dissipating. With the same applied pressure, changes in multiphase flow and geo-mechanical deformation caused by compressed air injection are relatively greater than those by freshwater injection. Furthermore, the expansion of soil skeleton induced by compressed air injection transfers upward and laterally continuously with time, while during and after freshwater injection, this expansion reaches rapidly a quasi-steady state. These differences induced by two fluids injection are mainly because air could spread upward and laterally easily for its lower density and phase state transition appears for compressed air injection.

• Korean Journal of Agricultural Science
• /
• v.41 no.4
• /
• pp.369-377
• /
• 2014

This study was carried out to evaluate the effect of rice husk (RHB) and food waste biochar (FWB) on upland soil with sandy loam texture, in terms of physico-chemical analysis, lettuce seed germination test, and orgainc carbon leaching experiment. RHB and FWB had different physico-chemical properties each other. Carbon to nitrogen ratio (C/N ratio) of RHB was 32, showing two times higher than that of FWB. FWB had high salt and heavy metal content, compared to RHB. This is probably due to different ingredients and production processing between two biochars each other. Results of germination test with Lettuce showed lower germination rate when FWB was applied because of higher salt concentration compared to control and RHB. Organic carbon leaching test using saturated soil column (${\Phi}75{\times}h75mm$) with $10MT\;ha^{-1}$ biochar application rate, showed higher saturated hydraulic conductivity in rice husk biochar treatment column, compared to control and food waste biochar treatment. The highest total organic carbon concentration in column effluent was lower than those in both of rice husk biochar and food waste biochar, whereas the differences was negligible after 9 pore volumes of effluent. Consequently, biochars from byproducts such as rice husk and food waste in sandy loam textured upland soil could enhance a buffer function such as reduction of leaching from soil, but the harmful ingredient to crops such as high salt and heavy metals could limit the agricultural use of biochars.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.40 no.11
• /
• pp.697-704
• /
• 2016

Coal modified by acid treatment was investigated to analyze the correlation between the cell performance and electrochemical parameters in a direct carbon fuel cell (DCFC). The fuels were subjected to thermogravimetry analysis, gas adsorption test, and X-ray photoelectron spectroscopy to investigate the fuel properties and surface characteristics. After the treatment of raw coal, the thermal reactivity of the treated fuels increased, and the specific surface area decreased, though the mean pore diameters of three fuels were similar. The coal treated by $HNO_3$ showed the highest ratio of oxygen to carbon, and also an increase in the surface oxygen groups on the fuel surface. Through comparison between the fuel surface properties and electrochemical performance, it was confirmed that the surface oxygen groups have an influence on the improvement in the DCFC performance.