• Journal of the Korean GEO-environmental Society
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• v.11 no.10
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• pp.15-24
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• 2010

In the case of underground power utilities pipe such as circular pipe, the most difficult problem is low compaction efficiency of the bottom of pipe inducing the failure of utilities. To overcome this problem, various studies have been performed and one of these is CLSM(Controlled Low Strength Materials) accelerated flow ability. But underground power utilities pipe backfill materials is also needed to have good thermal property that can dissipate the heat as rapidly as it is generated. So, in this study, we performed thermal resistancy test for various materials such as sand, weathered soil, clay and mixed soil to analyze the thermal characteristics of CLSM(Controlled Low Strength Materials) with accelerated flow ability for various conditions(water content, unit weight, void ratio, curing time) and to evaluate the applicability for backfill material of underground power utilities pipe. The test results of 16 specimens for thermal resistancy test showed good thermal property that maintained below $85^{\circ}C\;cm/W$.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.227-232
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• 1999

In this paper, a laboratory investigation was carried out to estimate the strength improvement of quicklime mixture for the effective use of surplus soils, and the shear strength with curing time was estimated at the content of lime. The effect of strength improvement has been established through the change of lime content with chlorides and sulfates from the samples taken at Samsan region, Ulsan. The test results indicated that the presence of calcium sulphate encouraged the efficiency of lime stabilization, and increased shear strength. Furthermore, it is necessary for inquiring into the relationship between the characteristics of strength and the chemical components.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.55-62
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• 2000

In this paper, a laboratory investigation was carried out to estimate the strength improvement of quicklime mixture with fly ash and rice husk ash for the effective use of surplus soils, and the shear strength with curing time was estimated at lime 10 percent with the change of fly ash and rice husk ash content. The effect of strength improvement has been established through the change of fly ash and rice husk ash content from the samples taken at Samsan region, Ulsan. The test results indicated that the presence of lime with fly ash and rice husk ash encouraged the stabilization efficiency of lime with fly ash and rice husk ash, and increased shear strength. Furthermore, it is necessary for inquiring into the relationship between the characteristics of strength and the chemical components.

• Clean Technology
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• v.19 no.4
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• pp.423-429
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• 2013

This study aimed to develop flowable backfill material using oyster shell, coal ash, and surplus soil. The high temperature (> $800^{\circ}C$) reaction was required to convert $CaCO_3$ to CaO. The solid specimens formed by pozzlanic reaction between CaO and coal ash showed low unconfined compressive strength. The effect of kaolin and blast furnace slag was also examined. It was found that CaO and coal ash could not be utilized due to high cost and low performance. The use of oyster shell without calcination ($CaCO_3$) was evaluated. The specimens composing of oyster shell and cement showed the higher unconfined compressive strength than that composing of coal ash and cement. However, use of oyster shell is limited in mortar due to the presence of salt. Addition of soil into oyster shell-coal ash-cement mixture satisfied the specification of flowable backfill material by optimizing their ratio.

• The Korean Journal of Ecology
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• v.20 no.2
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• pp.133-143
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• 1997

From 1984 to 1989 reclaimed coastal lands in Choongnam Province of the western coast of Korea were studied for soil texture at three sites(Daeho, Hyundai A and Hyundai B) and for desalination one site(Hyundai B). The soil textures of varied sites in Hyundai A were horizontally similar and composed of 39-40% clay, 40-49% silt and 8-14% sand. But those in Da돼 and Hyundai B differed horizontally in the same area and vertically at the same site. Soil texures of Da돼 were composed of 15-17% clay, 30-45% silt and 40-55% sand and those of Hyundai B were composed of 22-45% clay, 26-49% silt and 17-31% sand. The measured electrical conductivity(EC), which represents whole salt content of the reclaimed soil, decreased year by year. The vertical distribution of the EC changed temporally and spatially in the upper zone above a 50 cm depth but not in The lower zone below a 50 cm depth. The EC valus of the soil were inversely proportional to the magnitued of annual precipitation, evaporation and the numbers of rainy days with r equalling -0.97. But the annual decrease of the EC was directly proportional to climatic factors with r=0.7. Salt in the reclaimed land was leached out by the percolative action of surplus rain water, or moved up by evaporation and carried away by running rain water. The running out of the salt on the soil surface was most efficiently carried out over 10 mm precipitation per day.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.84-93
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• 2010

Compaction of backfill material of Underground power lines is difficult, especially under pipeline. so it could cause structural problem because of low compaction efficiency. So various methods have been taken to solve the problem and one of them is CLSM(Controled low-strength material accelerated flow ability). But In other countries, these are already in progress for a long time to research and development and recently on practical steps. But, in our country, study for only general structures, not for underground power line structure that is being constructed at night rapidly. In this study, we performed property tests and indoor & outdoor test (3 cases). The tests showed flow ability reached at the limit construction(160 mm) flowability by 9 to 15 minute after starting to mix, and construction buoyant is lowering after placing CLSM by 70 % of theoretical buoyant that is calculated by unit weight of material. In this paper, we performed indoor tests and outdoor tests to estimate mechanical properties and to suggest construction method(using batch plant, setting spacer at 1.8 m and placing at 2m) for CLSM that using surplus soil. And the test showed good results for construction quality, workability and structure safety.

• Journal of The Korean Society of Agricultural Engineers
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• v.63 no.3
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• pp.35-45
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• 2021

Digestate or slurry produced from anaerobic digestion is mostly applied to crop lands for its disposal and recovering nutrients. However, minimizing nitrogen losses following field application of the digestate is important for maximizing the plant's nitrogen uptake and reducing environmental concerns. This study was conducted to assess the effects of three different biogas digestate application techniques (sawdust mixed with digestate (SSD), the hole application method (HA), and digestate injected in the soil (SD)) on nitrate leaching potential in the soil. A pot laboratory experiment was conducted at room temperature of 25 ± 2 ℃ for 107 days. The experimental results showed that sawdust application method turned out to be appropriate for quick immobilization of surplus N in the form of microbial biomass N, reflecting its lower total nitrogen and NH₄-N contents and low pH. The NH₄-N and total nitrogen fate in the soil fertilized with manure showed no statistically significant (p > 0.05) differences between the different methods applied during the incubation time under room temperature. In contrast, NO₃-N concentration indicates significant reduction in sawdust treatment (p < 0.05) compared to the control and other application methods. However, the soil sawdust mixed with digestate was more effective than the other methods, because of the cumulative labile carbon contents of the amendment, which implies soil net N immobilization.

• Journal of Animal Environmental Science
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• v.3 no.2
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• pp.125-131
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• 1997

This paper was discussed N-balance of the republic of Korea. About 397Kg N/ha was inputted into the chemical fertilizer, animal feed, precipitation and nitrogen fixation. About 15kg N/ha was outputted from the Korea. The amount of N surplus was 397kg N/ha and loaded into environment. This causes the problem of water, air and soil pollution. It should take measures to improve the situation, such as depending more on selfsufficient feed and using nutrient cycling functions of soils.

• Journal of Wetlands Research
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• v.22 no.1
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• pp.49-58
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• 2020

The excessive use of fertilizer and compost in agricultural land increases the accumulation of nutrients in soil. The surplus nutrients in soil transported through surface and sub-surface flow can lead to water pollution problems and algal bloom. Moreover, nutrient accumulation and continuous crop cultivation changes the physical structure of the soil, which increases the potential of nutrient. The cultivation in the Daecheong Lake reservoir area may have a direct effect on the lake's water quality due to leaching and releasing of nutrients when water level rises. This research was carried out to analyze the physical and chemical properties of soil in the agricultural areas surrounding Daecheong Dam reservoir to provide basic data available for the establishment of Daecheong Lake water quality management measures. The soil of the Daecheong Lake reservoir was classified as sandy Loam, where surplus nutrients can be transported. Chemical compositions in the soil were found to be significantly affected by use of different fertilizer amounts. Nutrient outflow occurred during spring rainfall events from the rice paddy fields, whereas excess nutrients from summer to fall seasons originated from dry paddy fields. Nutrient outflow from dry paddy fields is mainly from sub-surface flow. Organic agricultural wastes from agricultural land and excessive vegetation inside the river was also evaluated to contribute to the increase in organic matter and nutrients of the river. The results can be used to select the priority management area designation and management techniques in the Daecheong Lake for water quality improvement.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2008.10a
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• pp.153-161
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• 2008

Agriculture and forest are basis for livelihood in Nepal while both sectors constitute around 40 percent of the national product and over two-thirds of the economically active population is dependent on agriculture. However, radical changes in land use, depletion in crops production and food availability are major threats due to loss of soil fertilityand severe environmental degradation. In this study, we used time series data from 1986/87 to 2005/06 about food crop production and population published by Government of Nepal, Ministry of Agriculture and Cooperatives and Central Bureau of Statistics. Descriptive statistics and ArcGIS were used to assess and map the food security status of Nepalese Terai based on the local food demand and supply system. Food supply to demand ratio(FSDR) was the main idea of assessment. Our results showed that out of 20 districts, only 8 districts were categorised under secured food districts whereas 5 districts were still under food unsecured situation. The analysis further revealed that 7 districts had faced food deficit more than 8-16 times during the last 20 year periods. Data further showed that there was surplus food supply relative to the requirements dictated by FSDR. However, the average FSDR was less than 1.2(less than 20% surplus) exploring fact that most of the districts were not producing sufficient food to cope up the food shock and after 1995 it was relatively stagnant. Our prediction reveals that food supply in Terai even in the future would remain at almost the same level as now, and there will not more than 16-17% surplus by 2021 considering medium vibrant population growth. The findings thus, indicate that Terai may not be a food secure region in the future, even though the region is considered as a food storage house of Nepal. In addition, this paper suggests ways to make future comprehensive case studies more widely comparable in Terai, Nepal.