• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
• /
• pp.1346-1353
• /
• 2009

In this study, a numerical study was carried out to simulate the expansion of ground borehole by pulse discharge technology using finite element analysis. Considering the mortar in the borehole as an acoustic medium and the surrounding soil as an elasto-plastic material, the strong shock wave developed by the pulse discharge was modeled using the underwater explosion model. The ground expansion was simulated based on a coupled acoustic-structural analysis with varying properties of mortar and soil, and the behavior between acoustic-structural interface.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제6권3호
• /
• pp.61-71
• /
• 2001

A regional master recession curve model to predict groundwater discharges in a given basin was presented. Considering a stream-aquifer system, both theoretical and experimental baseflow equations were compared and a practical groundwater discharge equation was derived, The groundwater discharge equation was expanded and transformed to the discharge equation at the basin exit. For practical use, the equation was expressed as a function of watershed area, the mean slope of basin and the recession constant. To verify the model, the model was applied to Ssang-chi basin where long-term and temporal hydrological data at the upper basin were collected. Our results show that a master recession curve of unmeasured area can be predicted.

• Journal of Electrical Engineering and Technology
• /
• 제11권2호
• /
• pp.446-454
• /
• 2016

In this paper, we present experimental results of the soil discharge characteristics as a function of moisture content when a 1.2/50-㎲ lightning impulse voltage is applied. For this study, laboratory experiments were carried out based on factors affecting the transient behavior in soils. The electrical breakdown voltages in soils were measured for a 0-6% range of moisture content for sand and a 0 - 4% range of moisture content for gravel. A test cell with semi-spherical electrodes buried face-to-face in the middle of a cylindrical container was used. The distance separating the electrodes is 100 mm. As a result, the time-lag to breakdown in soils decreases as the amplitude of applied voltage increases. The time-lag to initiation of ionization streamer is decreased, with an increase in the moisture content. However, the formative time-lag is rarely changed. The behavior of soil discharges depend not only on the type of soil and its moisture content but also on the amplitude of the impulse voltage. When the test voltage is applied repeatedly, electrical breakdown occurs along different discrete paths, leading radially away from the injected electrode. i.e., the fact that the ionization streamers propagate in different paths from shot to shot was observed.

• 한국지형학회지
• /
• 제23권1호
• /
• pp.77-85
• /
• 2016

To understand the difference of runoff discharge processes between Gwangneung deciduous and coniferous forest catchments, we collected hydrological data (e.g., precipitation, soil moisture, runoff discharge) and conducted hydrochemical analyses in the deciduous and coniferous forest catchments in Gwangneung National Arboretum in the northwest part of South Korea. Based on the end-member mixing analysis of the three storm events during the summer monsoon in 2005, the hillslope runoff in the deciduous forest catchment was higher 20% than the coniferousforest catchment during the firststorm event. Howerver, hillslope runoff increased from the second storm event in the coniferous catchment. We conclude that low soil water contents and topographical gradient characteristics highly influence runoff in the coniferous forest catchment during the first storm events. In general, coniferous forests are shown high interception loss and low soil moisture compared to the deciduous forests. It may also be more likely to be a reduction in soil porosity development when artificial coniferous forests reduced soil biodiversity. The forest soil porosity is an important indicator to determine the water recharge of the forest. Therefore, in order to secure the water resources, it should be managed coniferous forests for improving soil biodiversity and porosity.

• 한국물환경학회지
• /
• 제25권5호
• /
• pp.785-791
• /
• 2009

Using artificial rainfall simulator, the soil loss, which is deemed as the most cause of muddy water problem among Non-point source (NPS) pollutant, was studied by the analysis of direct runoff, groundwater discharge, and soil water storage properties concerned with rainfall intensity, slope of area, and land cover. The direct runoff showed increasing tendency in both straw covered and bared soil as slope increases from 5% to 20%. The direct runoff volume from straw covered surface were much lower than bared surface. The infiltration capacity of straw covered surface increased, because the surface sealing by fine material of soil surface didn't occur due to the straw covering. Under the same rainfall intensity and slope condition, 2.4~8.2 times of sediment yield were occurred from bared surface more than straw covered surface. The volume of infiltration increased due to straw cover and the direct runoff flow decreased with decrease of tractive force in surface. To understand the relationship of the rate of direct runoff, groundwater discharge, and soil water storage by the rainfall intensity, slope, and land cover, the statistical test was performed. It shows good relationship between most of factors, except between the rate of groundwater storage and rainfall intensity.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제28권5호
• /
• pp.25-35
• /
• 2023

This study aimed to classify spring types based on the hydrogeological characteristics of springs in Yongsu-ri~Hamo-ri coastal area in western part of Jeju Island. The springs in study area can be broadly categorized into three groups: perched groundwatrer springs (soil type), perched groundwater springs (sediment type), and basal groundwater springs. The perched groundwater springs of soil type correspond to springs where groundwater seeps out from the perched aquifer formed in the soil layer due to the development of clayey Kosan Formation beneath the surface. Because of the low hydraulic conductivity of soil layer, the average of spring discharge is less than 1 m³/day. The quality of spring water is significantly influenced by agricultural activities, resulting in high nitrate nitrogen concentrations and electrical conductivity. While the perched groundwater springs (sediment type) of the Suwolbong Tuff, which are located in the upper part of Kosan Formation, exhibited relatively higher discharge rates, their water quality was similar to soil-type springs. Basal groundwater springs are located in the zone of basal groundwater, mostly near the coastline. This type of spring appears to discharge of up to 3,707 m³, and the salinity content varies with the tidal fluctuations, especially increasing significantly during dry seasons.

• Journal of the Korean Wood Science and Technology
• /
• 제43권5호
• /
• pp.548-557
• /
• 2015

This study investigated environmental assessments of leachate containing formaldehyde from medium density fiberboard (MDF) disposed in laboratory-scale simulated landfills. Environmental impact assessment of leachate was conducted by measuring formaldehyde, toxicity, biochemical oxygen demand (BOD), chemical oxygen demand (COD), bacterial enumeration, and pH. Amount of formaldehyde in leachate from MDF in soil decreased to the level of soil only treatment by 28 days, and toxicity decreased as the amount of formaldehyde decreased. BOD and COD levels in leachate from the treatments containing MDF exceeded permissible discharge levels of BOD or COD throughout the experimental period. The pH levels of all treatment were within permissible discharge range except on day 0. Fewer bacteria were observed in leachate from MDF in soil treatment than other treatments (MDF only, cured UF resin in soil, and soil only). Consequently, the leachate from disposal of MDF in soil detrimentally affect on environment. However, soil buffered formaldehyde leaching and pH on leachate in this study. Waste MDF may be required the pre-water soaking treatment for leaching formaldehyde to reclaim on land.

• 한국농공학회논문집
• /
• 제56권5호
• /
• pp.67-75
• /
• 2014

In this study, the large-scale hydraulic model test was performed to investigate the hydraulic characteristics for development of the non-power soil cleaning and keeping system at the dike gate. The outlet height, outflow number, outflow discharge, and outflow cycle were compared and analyzed. The non-power soil cleaning and keeping system was most effective at 11.2 mm in the outlet height. And then the mean outflow cycle was 1.09 sec, and the mean outflow discharge was $0.00164m^3/s$. The total outflow number increased gradually as the water level of a water tank increased, and the outlet height decreased. As a level of water tank decreased, the mean outflow cycle was lengthened, and the unit outflow discharge increased. This result showed this system was most effective. To remove the silty clay deposited in facilities, the methods of excavation, dredging, high pressure washing, etc have been applied to the tidal facilities such as land reclamation, a small size fishing port, and a harbor for maintenance. However, this is extremely cost-ineffective, whereas the non-power soil cleaning and keeping system will bring about an enormously positive economic effect. In addition, when the non-power soil cleaning and keeping system is applied to the dike gate of land reclamation, a thorough examination of the local tidal data and the careful system planning are required to prevent the disaster damage caused by flooding.

• 한국터널지하공간학회 논문집
• /
• 제21권5호
• /
• pp.699-715
• /
• 2019

도시기반시설인 지중관거의 노후화가 심화되면서, 최근 도심지의 관거 주변에서 공동발생과 지반함몰 사례가 빈번하게 보고되고 있다. 지중관거 균열과 관련된 공동발생 및 지반함몰에 대해 많은 연구가 수행된 바 있으나, 기존 연구내용은 주로 관거의 균열 발생원인과 지반침하 거동에 집중되어 있다. 본 연구에서는 관거의 균열을 통한 지하수와 토립자 유출특성과 공동발생 메커니즘을 조사하였다. 또한, 토사유출로 인해 공동이 발생하고 지반함몰로 발전해가는 과정에 대한 가설을 수립하여 토립자 유출의 수리적 특성을 규명하고자 하였다. 관거 균열을 통한 토립자 유출 및 공동발생 메커니즘 규명을 위해 실내모형실험을 수행하였다. 모형실험으로부터 관거 균열을 통해 유출된 토립자를 측정하고, 실험과정을 영상촬영하여 PIV 분석을 통해 입자의 이동특성을 조사하였다. 본 연구를 통해 지중에서 발생하는 토립자의 이동, 공동발생 및 지반함몰 거동은 근본적으로 지하수의 이동에 의해 발생하는 것이며, 균열 위치와 관거 형상에 영향을 받음을 확인하였다.

• 한국지반환경공학회 논문집
• /
• 제19권11호
• /
• pp.23-30
• /
• 2018

최근 지반사고 발생통계에 따르면 도심지를 중심으로 지반함몰 및 침하발생 빈도수가 매년 증가하고 있어 사회적으로 문제가 되고 있다. 이 연구는 지반공동현상 실내모형실험을 통해 지하수위 변동과 지반함몰과의 연관성을 규명하고자 하였다. 화강풍화토와 표준사를 1:1로 혼합한 후 상대다짐도 30%, 50%, 80%로 사질지반을 조성하고, 지하수위 변화에 따른 토사유출량의 변화를 비교분석하였다. 사용재료의 물리적 특성은 입도분포가 양호한 모래질로서 최대건조단위중량 $1.94kg/cm^3$, 내부마찰각 $37^{\circ}$로 조성하였다. 하단으로부터 10cm, 20cm, 30cm 높이에 지하수위를 조성한 후 유출량을 분석하였다. 실험결과 지하수위가 높을수록 유출속도가 증가하며, 시간에 따른 공동의 크기도 증가하는 것으로 나타났다. 시간에 따른 토사의 누적유출량은 35분 경과 후 최대 30kg까지 발생하였으며, 지하수 하강에 따른 토사유출로 인해 지반함몰 범위가 증가한 것을 확인하였다.