• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.72-80
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• 2018

In this research, we tried to investigate the influence of concrete on cracks after applying to the actual construction site using the TPS construction method which can be easily charged by the mechanical injection method. To summarize the results, the following It is as follows. First, in the case of ultrasonic velocity, it can be seen that the ultrasonic wave passes rapidly at an average of about 36 mm / sec as compared with the syringe method when using the TPS method, and in the case of the injection depth, the syringe method In the case of TPS construction method, it showed an excellent tendency that 100% of the water retentive material was charged with all the formulations under a strong injection pressure. In the case of compressive strength, it was shown that the average was increased by 16.8% at the time of using the TPS construction method, and it was found to be structurally superior. Taken together, it is possible to confirm the behavior of the crack repairing agent by improving the quality by improving the strength and confirming the window installation by filling the injection material into the closed space at the crack site when using the TPS method compared with the syringe method. In addition, it is expected that construction time will be improved by shortening the construction period of about 5 days for the TPS construction method construction section 532 m, and usability will be expanded by the crack repair method of concrete structure.

• The Journal of Engineering Geology
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• v.28 no.2
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• pp.217-246
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• 2018

During the selection and characterization of target formations in the Small-scale Offshore $CO_2$ Storage Demonstration Project in the Pohang Basin, we have carefully investigated the possibility of induced earthquakes and leakage of $CO_2$ during the injection, and have designed the storage processes to minimize these effects. However, people in Pohang city have a great concern on $CO_2$-injection-intrigued seismicity, since they have greatly suffered from the 5.4 magnitude earthquake on Nov. 15, 2017. The research team of the project performed an extensive self-investigation on the safety issues, especially on the possible $CO_2$ leakage from the target formation and induced earthquakes. The target formation is 10 km apart from the epicenter of the Pohang earthquake and the depth is also quite shallow, only 750 to 800 m from the sea bottom. The project performed a pilot injection in the target formation from Jan. 12 to Mar. 12, 2017, which implies that there are no direct correlation of the Pohang earthquake on Nov. 15, 2017. In addition, the $CO_2$ injection of the storage project does not fracture rock formations, instead, the supercritical $CO_2$ fluid replaces formation water in the pore space gradually. The self-investigation results show that there is almost no chance for the injection to induce significant earthquakes unless injection lasts for a very long time to build a very high pore pressure, which can be easily monitored. The amount of injected $CO_2$ in the project was around 100 metric-tonne that is irrelevant to the Pohang earthquake. The investigation result on long-term safety also shows that the induced earthquakes or the reactivation of existing faults can be prevented successfully when the injection pressure is controlled not to demage cap-rock formation nor exceed Coulomb stresses of existing faults. The project has been performing extensive studies on critical stress for fracturing neighboring formations, reactivation stress of existing faults, well-completion processes to minimize possible leakage, transport/leakage monitoring of injected $CO_2$, and operation procedures for ensuring the storage safety. These extensive studies showed that there will be little chance in $CO_2$ leakage that affects human life. In conclusion, the Small-scale Offshore $CO_2$ Storage Demonstration Project in the Pohang Basin would not cause any induced earthquakes nor signifiant $CO_2$ leakage that people can sense. The research team will give every effort to secure the safety of the storage site.

• Korean Journal of Environmental Agriculture
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• v.22 no.1
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• pp.16-25
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• 2003

Manun Reservoir, located in Andong district has the capacity of 2 million tons in irrigation water supply with the drainage area of $23.8\;km^2$. Manun Reservoir is over fifty year old, and shallow in depth. The ratio of drainage area (DA) to reservoir surface area (SA) as an effective physical parameter on water quality was 56.1 and was higher than those of other agricultural reservoirs. The ratio of reservoir storage (ST) to SA in Manun Reservoir was 4.79, and the mean depth was below 8m. Both ratios of DS/SA, total area (TA)/ST and ST/SA in Manun Reservoir were relatively higher than those in other agricultural reservoir and natural lakes in Korea. These physical parameters in Manun Reservoir, however, had a eutropic potential significance. Average of COD, IN, and TP in Manun Reservoir were 11.1 mg/L 1.426 mg/L, 0.093 mg/L, respectively. In the inflow stream of Manun Reservoir, the TN ($1.426{\sim}3.809\;mg/L$) was higher than those in reservoir. Only Lyngbya spp. was dominant in phytoplankton for this study period and Gymnodinium spp., Peridinium spp., and Cryptomonas spp. were dominant in zooplankton. According to the Carlson's trophic status index, Mnnun Reservoir was eutrophic in 1996, 1997, and 1999, and hypertrophic in 1998.

• Economic and Environmental Geology
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• v.55 no.5
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• pp.477-495
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• 2022

This study examined the sustainability of CO₂-rich water by analyzing the water level and water quality change pattern with the amount of its use in Angseong area, Chungju. The origin and supply of CO₂ component were discussed in consideration of ⁸⁷Sr/⁸⁶Sr ratio, occurrence of CO₂-rich fluid inclusions in nearby W-Mo deposits and other surrounding geological characteristics. According to the data from 1986 to 2017, the depth of the water level of CO₂-rich water was significantly lowered in the late period (2009-2015) than in the early period (1986-1992) of the development of hot spa wells, and the optimal yields for pumping tests also showed a tendency to gradual decrease. Concentrations of CO₂ component also decreased continuously in the later stages compared to the early stages of development, but it has been stable since 2012. It is inferred that the geological environment related to forming W-Mo quartz vein deposits (0.5×1.5×several km) around the study area are largely involved in the origin and supply of CO₂ component, and the supply of CO₂ component is not infinitely supplied from deep current magma activity. Rather, since it is finitely supplied from a restricted subsurface region formed in the past geological period, it is necessary to efficiently control its use in order to maintain the sustainability of CO₂-rich water in the study area.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.4
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• pp.383-391
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• 2020

In this study, Hunt's analytical solution and Ward & Lough's analytical solution for two-layered leaky aquifer system were used to estimate stream depletions due to shallow and deep groundwater pumping, and their differences were compared. Depending on the combination of the separation distance between the stream and the well, the transmissivity and the storage coefficient of the aquifer, and the leakage coefficient between the upper and lower layers, the stream depletion, which is the amount of stream water reduction compared to the amount of groundwater pumping, for each of 45,000 cases was calculated for both shallow and deep groundwater pumping, and the differences were analyzed quantitatively. When the leakage coefficient was very small, with a value of 10^-61/d, the difference in the average five-year stream depletion due to the pumping of shallow and deep groundwater showed a large deviation of up to 0.9 depending on the given hydraulic characteristics; this value exponentially decreased as the stream depletion factor (SDF) increased. This exponential relationship gradually weakened as the leakage coefficient increased due to interaction effects between layers, resulting in a small difference of up to 0.2 when the leakage coefficient reached 10^-31/d. Under the condition of greater interlayer hydraulic connectivity, there was little influence of the depth of groundwater pumping on the stream water reduction.

• 한국지구물리탐사학회:학술대회논문집
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• 2002.09a
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• pp.101-125
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• 2002

A lake seismic survey was carried out to investigate possible geohazards for construction of the underground LPG storage at Namyang Lake. The proposed survey site has a land-lake combined geography and furthermore water depth of the lake is shallow. Therefore, various seismic methods such as marine single channel high resolution seismic reflection survey, sonobuoy refraction survey, land refraction survey and land-lake combined refraction survey were applied. Total survey amounts are 34 line-km of high resolution lake seismic survey, 14 lines of sonobuoy refraction survey, 890 m of land refraction survey and 8 lines of land-lake combined refraction survey. During the reflection survey, there were severe water reverberations from the lake bottom obscured subsurface profiling. These strong multiple events appeared in most of the survey area except the northern and southern area near the embankment where seems to be accumulated mainly mud dominated depositions. The sonobuoy refraction profiles also showed the same Phenomena as those of reflection survey. Meanwhile the results of the land-lake combined refraction survey showed relatively better qualities. However, the land refraction survey did not so due to low velocity soil layer and electrical noise. Summarized results from the lake seismic survey are that acoustic basement with relatively flat pattern appeared 30m below water level and showed three types of bedrock such as fresh, moderately weathered and weathered type. According to the results of the combined refraction survey, a velocity distribution pattern of the lake bottom shows three types of seismic velocity zone such as >4.5 km/s, 4.5-4.0km/s and <4.0km/s. The major fault lineament in the area showed NW-SE trend which was different from the Landsat image interpretation. A drilling was confirmed estimated faults by seismic survey.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.6
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• pp.327-340
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• 2017

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2016. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of flow, heat and mass transfer, the reduction of pollutant exhaust gas, cooling and heating, the renewable energy system and the flow around buildings. CFD schemes were used more for all research areas. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results of the long-term performance variation of the plate-type enthalpy exchange element made of paper, design optimization of an extruded-type cooling structure for reducing the weight of LED street lights, and hot plate welding of thermoplastic elastomer packing. In the area of pool boiling and condensing, the heat transfer characteristics of a finned-tube heat exchanger in a PCM (phase change material) thermal energy storage system, influence of flow boiling heat transfer on fouling phenomenon in nanofluids, and PCM at the simultaneous charging and discharging condition were studied. In the area of industrial heat exchangers, one-dimensional flow network model and porous-media model, and R245fa in a plate-shell heat exchanger were studied. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, subjects include mobile cold storage heat exchanger, compressor reliability, indirect refrigeration system with $CO_2$ as secondary fluid, heat pump for fuel-cell vehicle, heat recovery from hybrid drier and heat exchangers with two-port and flat tubes. In the alternative refrigeration/energy system category, subjects include membrane module for dehumidification refrigeration, desiccant-assisted low-temperature drying, regenerative evaporative cooler and ejector-assisted multi-stage evaporation. In the system control category, subjects include multi-refrigeration system control, emergency cooling of data center and variable-speed compressor control. (4) In building mechanical system research fields, fifteenth studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the analyses of indoor thermal environments controlled by portable cooler, the effects of outdoor wind pressure in airflow at high-rise buildings, window air tightness related to the filling piece shapes, stack effect in core type's office building and the development of a movable drawer-type light shelf with adjustable depth of the reflector. The subjects of building energy were worked on the energy consumption analysis in office building, the prediction of exit air temperature of horizontal geothermal heat exchanger, LS-SVM based modeling of hot water supply load for district heating system, the energy saving effect of ERV system using night purge control method and the effect of strengthened insulation level to the building heating and cooling load.

• Journal of the Korean Institute of Landscape Architecture
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• v.41 no.6
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• pp.107-116
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• 2013

This study was undertaken to investigate the characteristics of retention and evapotranspiration in the extensive greening module of sloped and flat rooftops for stormwater management and urban heat island mitigation. A series of 100mm depth's weighing lysimeters planted with Sedum kamtschaticum. were constructed on a 50% slope facing four orientations(north, east, south and west) and a flat rooftop. Thereafter the retention and evapotranspiration from the greening module and the surface temperature of nongreening and greening rooftop were recorded beginning in September 2012 for a period of 1 year. The characteristics of retention and evapotranspiration in the greening module were as follows. The water storage of the sloped and flat greening modules increased to 8.7~28.4mm and 10.6~31.8mm after rainfall except in the winter season, in which it decreased to 3.3mm and 3.9mm in the longer dry period. The maximum stormwater retention of the sloped and flat greening modules was 22.2mm and 23.1mm except in the winter season. Fitted stormwater retention function was [Stormwater Retention Ratio(%)=-18.42 ln(Precipitation)+107.9, $R^2$=0.80] for sloped greening modules, and that was [Stormwater Retention Ratio(%)=-22.64 ln(X)+130.8, $R^2$=0.81] for flat greening modules. The daily evapotranspiration(mm/day) from the greening modules after rainfall decreased rapidly with a power function type in summer, and with a log function type in spring and autumn. The daily evapotranspiration(mm/day) from the greening modules after rainfall was greater in summer > spring > autumn > winter by season. This may be due to the differences in water storage, solar radiation and air temperature. The daily evapotranspiration from the greening modules decreased rapidly from 2~7mm/day to less than 1mm/day for 3~5 days after rainfall, and that decreased slowly after 3~5 days. This indicates that Sedum kamtschaticum used water rapidly when it was available and conserved water when it was not. The albedo of the concrete rooftop and greening rooftop was 0.151 and 0.137 in summer, and 0.165 and 0.165 in winter respectively. The albedo of the concrete rooftop and greening rooftop was similar. The effect of the daily mean and highest surface temperature decrease by greening during the summer season showed $1.6{\sim}13.8^{\circ}C$(mean $9.7^{\circ}C$) and $6.2{\sim}17.6^{\circ}C$(mean $11.2^{\circ}C$). The difference of the daily mean and highest surface temperature between the greening rooftop and concrete rooftop during the winter season were small, measuring $-2.4{\sim}1.3^{\circ}C$(mean $-0.4^{\circ}C$) and $-4.2{\sim}2.6^{\circ}C$(mean $0.0^{\circ}C$). The difference in the highest daily surface temperature between the greening rooftop and concrete rooftop during the summer season increased with an evapotranspiration rate increase by a linear function type. The fitted function of the highest daily surface temperature decrease was [Temperature Decrease($^{\circ}C$)=$1.4361{\times}$(Evapotranspiration rate(mm/day))+8.83, $R^2$=0.59]. The decrease of the surface temperature by greening in the longer dry period was due to sun protection by the sedum canopy. The results of this study indicate that the extensive rooftop greening will assist in managing stormwater runoff and urban heat island through retention and evapotranspiration. Sedum kamtschaticum would be the ideal plant for a non-irrigated extensive green roof. The shading effects of Sedum kamtschaticum would be important as well as the evapotranspiration effects of that for the long-term mitigation effects of an urban heat island.

• Journal of the Korea Concrete Institute
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• v.26 no.1
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• pp.71-78
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• 2014

The long term integrity of concrete cask is very important for spent nuclear fuel dry storage system. However, there are serious concerns about early deterioration of concrete cask from creaking and corrosion of reinforcing steel by chloride ion because the cask is usually located in seaside, expecially by combined deterioration such as chloride ion and heat, carbonation. This study is to investigate the relation between temperature and chloride ion diffusion of concrete. Immersion tests using 3.5% NaCl solution that were controlled in four level of temperature, i.e. 20, 40, 65, and $90^{\circ}C$, were conducted for four months. The chloride ion diffusion coefficient of concrete was predicted based on the results of profiles of Cl- ion concentration with the depth direction of concrete specimens using the method of potentiometric titration by $AgNO_3$. Test results indicate that the diffusion coefficient of chloride ion increases remarkably with increasing temperature, and there was a linear relation between the natural logarithm values of the diffusion coefficients and the reciprocal of the temperature from the Arrhenius plots. Activation energy of concrete in this study was about 46.6 (W/C = 40%), 41.7 (W/C = 50%), 30.7 (W/C = 60%) kJ/mol under a temperature of up to $90^{\circ}C$, and concrete with lower water-cement ratio has a tendency towards having higher temperature dependency.

• Journal of Korean Society of Forest Science
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• v.97 no.5
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• pp.492-500
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• 2008

Since vegetation significantly influences on soil carbon and nutrient storage, vegetation change has been focused on terrestrial carbon and nutrient cycling studies. In this study we investigated soil carbon and major nutrient capitals at the abandoned fields, which had different vegetation composition: a three year abandoned field ($AGR_3$), two ten years abandoned fields ($PD_{10}$ dominant with Pinus densiflora and Fraxinus rhynchophylla and $PM_{10}$ dominant with Populus maximowiczii), and an over sixty years forest ($FOR_{60}$). which were located at Hongcheon-gun, Kangwon-do, South Korea. Both main effects for organic matter (%) were significant: shallow soil > deep soil and $FOR_{60}=PM_{10}$ > $AGR_3=PD_{10}$. Nitrogen concentrations at $PM_{10}$ were the highest, while the lowest at $PD_{10}$. Available phosphorus concentrations were the highest at $PD_{10}$, which were over 10 times of site $FOR_{60}$ and $AGR_3$ at 0-10 cm soil depth. The average organic matter ($173Mg\;ha^{-1}$) and nitrogen contents ($10Mg\;ha^{-1}$) of $PM_{10}$ and $FOR_{60}$ were higher than those of $AGR_3$ and $PD_{10}$ by 57% and 42%, respectively. The available phosphorus contents above 30 cm mineral soil at $PD_{10}$ ($3.8Mg\;ha^{-1}$) and $PM_{10}$ ($1.3Mg\;ha^{-1}$) were over 120 times and 40 times more than at $FOR_{60}$. Calcium ($3.7Mg\;ha^{-1}$) and magnesium contents ($2.8Mg\;ha^{-1}$) at $FOR_{60}$ were twice or three times higher than at other sites. Organic matter amounts in 0-10 cm and 10-30 em soil had significant positive relationships with nitrogen, calcium, and magnesium contents, but not available phosphorus and potassium contents. This study could not identify the effect of chronological factor and vegetation composition on soil carbon and nutrient capital owing to diverse topography as well as limited study sites. However, this study suggests the accuracy of investigation for regional carbon and nutrient sequestration can be achieved by considering the period of abandoned time on the fields and the land use types. These results may suggest the benefits of forest restoration for soil carbon and nutrient accumulation in marginal agricultural lands in South Korea.