• Korean Journal of Soil Science and Fertilizer
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• v.16 no.1
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• pp.7-13
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• 1983

Laboratory determinations of saturated hydraulic conductivity were conducted with four soils varying in texture from sand to clay and with five waters with different salinity level. The waters varied in total dissolved solids from 1,250 to $15,000mg/{\ell}$ and in SAR from 16 to 57 and were representative of saline waters in New Mexico. Saturated hydraulic conductivities of the soils were not significantly affected by water salinity if these waters were the sole source of irrigation water. However, small additions of distilled water, assuming simulated to rain, to soils previously equilibrated with the saline waters significantly decreased soil permeability. Dispersion and short or long-distance transport of clay apparently clogged conducting pores when distilled water was introduced. Swelling was an important mechanism in reducing soil permeability only in the clay soil. The data suggest that, when saline water is the dominant irrigation source and is supplemented by rain, (1) all saline waters could be used on very sandy soils, (2) no saline waters should be used on very heavy soils, and (3) slightly saline, but not very saline, waters could be used on medium-textured soils.

• The Journal of Engineering Geology
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• v.32 no.2
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• pp.209-219
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• 2022

To experimentally investigate the variation of soil characteristics in slope during rainfall and the shape of slope failure, the model test was performed using soil box and artificial rainfall simulator. The model test of slope formed by the homogenous sand was performed, and the saturation pattern in the model slope due to rainfall infiltration was observed. The slope model with the inclination of 35° was set up on the slope of 30°, and the rainfall intensity of 50 mm/hr was applied in the test. The soil depth of 35 cm was selected by considering the size of soil box, and the TDR (time domain reflectometry) sensors were installed at various depths to investigate the change of soil characteristics with time. As the result of model test, the slope model during rainfall was saturated from the soil surface to the subsurface, and from the toe part to the crest part due to rainfall infiltration. That is, the toe part of slope was firstly saturated by rainfall infiltration, and then due to continuous rainfall the saturation range was enlarged from the toe part to the crest part in the slope model. The failure of slope model was started at the toe part of slope and then enlarged to the crest part, which is called as the retrogressive failure. At the end of slope failure, the collapsed area increased rapidly. Also, the mode of slope failure was rotational. Meanwhile, the slope failure was occurred when the matric suction in the slope was reached to the air entry value (AEV) estimated in soil-water characteristic curve (SWCC).

• Journal of the Korean Geotechnical Society
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• v.24 no.1
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• pp.37-49
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• 2008

A geothermal heat pump system is a preferable alternative energy system in Korea because it uses the heat energy of the earth, which is environmentally friendly and inexhaustible. In order to characterize the thermal conductivity and viscosity of grout materials used for backfilling ground heat exchangers, nine bentonite grouts, one marine clay from Boryung, and cement grouts adapted in the United State have been considered in this study. The bentonite grouts indicate that the thermal conductivity and viscosity increase with the content of bentonite or filler (silica sand). In addition, material segregation can be observed when the viscosity of grout is relatively low. The marine clay turns out to be unsuitable for backfilling the ground heat exchanger due to its insufficient swelling potential. The saturated cement grouts appear to possess much higher thermal conductivity than the saturated bentonite grouts, and the reduction of thermal conductivity in the cement grouts after drying specimens is less than that in the case of the bentonite grouts. Maintaining the moisture content of grouts is a crucial factor in enhancing the efficiency of ground heat exchangers.

• Journal of the Korean Geotechnical Society
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• v.23 no.2
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• pp.71-83
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• 2007

Liquefaction resistance depends strongly upon the degree of saturation, which is expressed in terms of the pore pressure coefficient, B. The B-value has been widely used to quantify the state of saturation of laboratory samples. However, it is practically impossible to determine in situ state of saturation by using the B-value. So, P-wave velocity can be alternatively used as a convenient index for evaluating the in situ state of saturation. In this paper, the Stokoe type torsional shear (TS) testing system was modified to saturate the specimen, with which it is also possible to measure P ($V_p$), S-wave velocity ($V_s$) and the excess pore water pressure buildup In order to examine the effect of B-value for nearly saturated sands. A series of the tests were carried out at 3 relative densities (40%, 50% and 75%) and various B-values using Toyoura sand. Based on the test results, the variations of $V_p\;and\;V_s$ with B-value were analyzed and compared with a existing theoretically derived formula. The normalized pore water pressure, $du/{\sigma}{_0}'$ and cyclic threshold shear strain, ${\gamma}^c_{th}$ with B-value were also analyzed. Additionally the test results related to pore water pressure were analyzed by $V_p$ to apply to the field seismic analysis.

• The Journal of the Acoustical Society of Korea
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• v.25 no.5
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• pp.246-256
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• 2006

The plane wave reflection coefficient is an acoustic property containing all the information concerning the ocean bottom and can be used as an input parameter to various acoustic propagation models. In this paper, we measure the plane wave reflection coefficient, the sound speed, thd the attenuation for saturated granular medium in the water tank. Three kinds of glass beads and natural sand are used as the granular medium. The reflection experiment is performed with the sinusoidal tone bursts of 100 kHz at incident angles from 28 to 53 degrees, and the sound speed and attenuation experiment are performed also with the same signal. From the measured reflection signal, the reflection coefficient is calculated with the self calibration method and the experimental uncertainties are discussed. The sound speed and the attenuation measurements are used for the estimation of the porosity and permeability, the main Biot parameters. The estimated values are compared to the directly measured values and used as input values to the Biot theory in order to calculate the theoretical reflection coefficient. Finally, the reflection coefficient predicted by Biot theory is compared to the measured reflection coefficient and their characteristics are discussed.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.643-646
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• 2005

The gas hydrate exploration using seismic reflection data, the detection of BSR(Bottom Simulating Reflector) on the seismic section is the most important work flow because the BSR have been interpreted as being formed at the base of a gas hydrate zone. Usually, BSR has some dominant qualitative characteristics on seismic section i.e. Wavelet phase reversal compare to sea bottom signal, Parallel layer with sea bottom, Strong amplitude, Masking phenomenon above the BSR, Cross bedding with other geological layer. Even though a BSR can be selected on seismic section with these guidance, it is not enough to conform as being true BSR. Some other available methods for verifying the BSR with reliable analysis quantitatively i.e. Interval velocity analysis, AVO(Amplitude Variation with Offset)analysis etc. Usually, AVO analysis can be divided by three main parts. The first part is AVO analysis, the second is AVO modeling and the last is AVO inversion. AVO analysis is unique method for detecting the free gas zone on seismic section directly. Therefore it can be a kind of useful analysis method for discriminating true BSR, which might arise from an Possion ratio contrast between high velocity layer, partially hydrated sediment and low velocity layer, water saturated gas sediment. During the AVO interpretation, as the AVO response can be changed depend upon the water saturation ratio, it is confused to discriminate the AVO response of gas layer from dry layer. In that case, the AVO modeling is necessary to generate synthetic seismogram comparing with real data. It can be available to make conclusions from correspondence or lack of correspondence between the two seismograms. AVO inversion process is the method for driving a geological model by iterative operation that the result ing synthetic seismogram matches to real data seismogram wi thin some tolerance level. AVO inversion is a topic of current research and for now there is no general consensus on how the process should be done or even whether is valid for standard seismic data. Unfortunately, there are no well log data acquired from gas hydrate exploration area in Korea. Instead of that data, well log data and seismic data acquired from gas sand area located nearby the gas hydrate exploration area is used to AVO analysis, As the results of AVO modeling, type III AVO anomaly confirmed on the gas sand layer. The Castagna's equation constant value for estimating the S-wave velocity are evaluated as A=0.86190, B=-3845.14431 respectively and water saturation ratio is $50\%$. To calculate the reflection coefficient of synthetic seismogram, the Zoeppritz equation is used. For AVO inversion process, the dataset provided by Hampson-Rushell CO. is used.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.4
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• pp.347-354
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• 2016

This study was conducted to investigate the physical and chemical properties of soils in Saemangeum reclaimed lands. The investigated areas were total 5,020 ha which included 220 ha for Agricultural Life site, 2,450 ha for Tourism & Leisure site, 1,130 ha for Industrial & Research site, 820 ha for Bioenergy crop production site, and 400 ha for Rural City site. Soil samples consisting of the upper 20 cm from the surface were collected in every $200m{\times}500m$ of the each site in March and September, 2015. Particle size distribution of soils in the reclaimed land was 83.2% sand, 8.6% silt and 8.2% clay in average. Soil texture was distributed as 40.8% sandy soil, 35.5% loamy sand, and 19.7% sandy loam. Based on the investigation of soil chemical properties conducted in March, 2015, soil pH, electrical conductivity of a saturated soil paste extract (ECe), and exchangeable (Exch.) $K^+$ and $Mg^{2+}$ concentrations were higher than those of the optimum levels for upland soil, whereas soil organic matter content, available (Avail.) phosphate concentration, and Exch. $Ca^{2+}$ concentration were lower than those of the optimum ranges. Depending on the results of the soil chemical properties measured in September, 2015, soil pH, ECe, and Exch. $K^+$ concentration were higher than those of the optimum levels, but soil organic matter, Avail. phosphate, and Exch. $Ca^{2+}$ concentration were lower than the optimum ranges. In addition, distribution of sodic soil ranged between 41.4% and 50.0%, and saline soils were from 16.4 to 31.8%. Soils with pH values above 7.0 increased from 15.3% in March to 35.2% in September. Soils with ECe values over $4.8dS\;m^{-1}$ increased from 45.6% to 50.7%, whereas soils with the values below $2.0dS\;m^{-1}$ decreased from 42.8% to 36.9%.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.363-369
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• 2003

The purpose of this study is to understand the dissipation pattern of excess pore pressure after liquefaction and to estimate the variation in permeability during shaking load, which should be known for settlement predictions of the ground undergoing liquefaction. In this study, 1-g shaking table tests were carried out for 5 different kinds of sands, all of which had high liquefaction potentials. During the tests excess pore pressure at various depths, and surface settlements were measured. The measured dissipation curve of the excess pore pressure after liquefaction was linearly simulated using the solidification theory, and from the analysis of the slopes of linearly simulated curves, the correlation between dissipation velocity and the gradation characteristics was obtained. By substituting this correlation and the measured settlement to the dissipation velocity equation recommended in solidification theory, the permeability during dissipation was calculated, which was used for estimating the permeability variation during shaking load. The dissipation velocity of excess pore pressure after liquefaction had a linear correlation with the effective grain size divided by the coefficient of uniformity. The permeability during dissipation and liquefaction increased by 1.1∼2.8 times and 1.4∼5 times compared to the initial permeability of the original ground, respectively. And the amount of increase became greater as the effective grain size of the test sand increased and the coefficient of uniformity decreased.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2003.10a
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• pp.134-135
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• 2003

The dental implant materials required good mechanical properties, such as fatigue strength, combined with a high resistance to corrosion. For increasing fatigue resistance and delaying onset of stress corrosion cracking, shot peening has been used for > 50 years to extend service life of metal components. However, there is no information on the electrochemical behavior of shot peened and hydroxyapatite(HA) coated Ti-6Al-4V alloys. To increase fatigue strength, good corrosion resistance, and biocompatibility, the electrochemical characteristics of Ti/TiN/HA coated and shot peened Ti-6Al-4V alloys by electron beam physical vapor deposition(EB-PVD) have been researched by various electrochemical method in 0.9%NaCl. Ti-6Al-4V alloys were prepared under the condition of hydrogen and vacuum arc furnace. The produced materials were quenched at 1000$^{\circ}C$ under high purity dried Ar atmosphere and were hold at 500$^{\circ}C$ for 2 hrs to achieve the fatigue strength(1140㎫) of materials. Ti-6Al-4V alloys were prepared under the condition of hydrogen and vacuum arc furnace. Shot peening(SP) and sand blasting treatment was carried out for 1, 5, and 10min. On the surface of Ti-6Al-4V alloys using the steel balls of 0.5mm and alumina sand of 40$\mu\textrm{m}$ size. Ti/TiN/HA multilayer coatings were carried out by using electron-beam deposition method(EB-PVD) as shown Fig. 1. Bulk Ti, powder TiN and hydroxyapatite were used as the source of the deposition materials. Electrons were accelerated by high voltage of 4.2kV with 80 - 120mA on the deposition materials at 350$^{\circ}C$ in 2.0 X 10-6 torr vacuum. Ti/TiN/HA multilayer coated surfaces and layers were investigated by SEM and XRD. A saturated calomel electrode as a reference electrode, and high density carbon electrode as a counter electrode, were set according to ASTM GS-87. The potentials were controlled at a scan rate of 100 mV/min. by a potentiostat (EG&G Co.273A) connected to a computer system. Electrochemical tests were used to investigate the electrochemical characteristics of Ti/TiN/HA coated and shot peened materials in 0.9% NaCl solution at 36.5$^{\circ}C$. After each electrochemical measurement, the corrosion surface of each sample was investigated by SEM.

• Korean Journal of Soil Science and Fertilizer
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• v.35 no.4
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• pp.207-215
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• 2002

Changes in salinity, hydraulic conductivity and penetration resistance in a reclaimed tidal land reclaimed in 1986 were studied. The salinity monitoring based on electrical conductivity of saturated extract, ECe, was conducted from 1994, when the land use for experimental crop production started after tile drainage. The site was abandoned since 1999. The hydraulic conductivity was measured by a sand fill auger hole method, and the resistance was measured with a dynamic penetrometer in situ. The averaged ECe in 1994 was $33.7dS\;m^{-1}$ ranging from 25.5 to $44.8dS\;m^{-1}$, and was decreased to $25.7dS\;m^{-1}$ with large range from 0.8 to $70.3dS\;m^{-1}$ before experiment was $1.89{\times}10^{-7}m\;s^{-1}$. It increased to $1.32{\times}10^6m\;s^{-1}$ in the top 20-cm soil with large variability, while it showed $3.44{\times}10^7m\;s^{-1}$ beneath the 20-cm soil depth with less variability. The penetration resistance of the soil ranged from 0.05 to 9.99MPa. The vertical distribution of penetration resistance indicated the hardened layer was developed at the depth of 20~40 cm where the hydraulic conductivity was sharply decreased.