• Korean Journal of Soil Science and Fertilizer
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• v.50 no.4
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• pp.275-284
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• 2017

The food situation in North Korea (Democratic People's Republic of Korea, DPRK) has been in difficulty situation because of a shortage of energy, and of raw materials such as fertilizer and agricultural chemicals. The international agricultural aid programs can alleviate some difficulties in the agricultural areas, but the policies and measures in North Korea can not help difficulties in the agriculture due to the institutional obstacles enforced by DPRK. The arable area of DPRK is approximately $20,000km^2$, of which $14,000km^2$ is well for cereal cultivation. Fertilizer supplies in recent years between 700,000 and 750,000 tons annually were less than 50% of the normal requirement. Also, North Korea strongly needed to inject phosphorus fertilizer and lime to increase the fertility. Soil degradation in DPRK was characterized by physical and chemical changes caused by rapid loss of clay particles and organic matter. Intensive ploughing and tilling to grow crops may lead to massive soil degradation and declining yields. Although farmers in the DPRK have faced numerous challenges, not least of which are soil erosion, scarce inputs and extreme weather like drought, flooding and cold spells. Therefore farmers should be encouraged to adopt more environmentally sound cropping practices, to access quality seeds and planting materials and to reduce losses after the harvest.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.2 s.25
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• pp.35-44
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• 2007

Plowable fill is generally a mixture of sand, fly ash, a small amount of cement and water. Sand is the major component of most flowable fill mixes. Marine dredged soil was adopted for flowable fill instead of fly ash. Natural sea sand and in-situ soil were used for comparison. The flow behavior, hardening characteristics, and ultimate strength behavior of flowable fill were investigated. The unconfined compression test necessary to sustain walkability as the fresh flowble fill hardens was determined and the strength at 3-days appeared to correlate well with the water-to-cement ratio. The strength parameters, like cohesion and internal friction angle, was determined along the curing time. The creep test for settlement potential was conducted. Also, potable falling weight deflectometer(PFWD) test has been carried out for elastic modulus of each controlled low strength materials(CLSM). The data presented show that marine dredged soil and in-situ soil can be successfully used in CLSM.

• Journal of the Korean GEO-environmental Society
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• v.12 no.11
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• pp.13-21
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• 2011

To recover basic functions of river such as water control, irrigation, environment, culture, a national river improvement project, the four river restoration projects were currently planned and under construction in Korea. This project is designed to preserve cultural assets and ecosystem from flooding, for that reason, environmentally friendly materials of construction are strongly emphasized. In this study, the soil and cement admixtures are developed. And, the compaction test and the unconfined compressive strength test to evaluate applicability of probiotics as environmentally friendly materials are conducted the soil and cement admixtures. As a result, the probiotic culture was not active in completely dried specimen to obtain accurate mixing proportion. It indicates that the probiotics cannot influence on the development the soil and cement admixtures. A further research will focus on the effect of response between polysaccharide environmentally friendly soil stabilizer and natural specimen.

• Journal of Korean Society of Forest Science
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• v.101 no.2
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• pp.175-184
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• 2012

This study was conducted to develop new mattress systems with vegetation base materials for protecting stream bank and rapid rehabilitation. Vegetation base materials are primarily compounded with fine soil, organic composts and peat moss as plant fibers, a water retainer and a soil improver. Peat moss can usually provide necessary natural fibers and organic materials in soil. Especially, peat moss can absorb up to 25 times its own weight in water and is therefore valued as a water retainer to prevent drying effect of vegetation base materials which can harm the growth of vegetation in mattresses. Normally mattress systems resist the lateral earth pressures or stream power by their own weight. Therefore, filled materials must have suitable weight, compressive strength and durability to resist the loading, as well as the effects of water and weathering. In this project, 100 to 200-mm clean, hard stones were basically specified, and about 50-mm rubbles were also used. Test application of new mattress system carried out in the stream bank of a small stream in the Gwangreung experimental forest, belonging to Korea Forest Research Institute (KFRI) in December 16th, 2006. As a result of the monitoring of vegetation coverage of test application plots (each plot size is 4 by 2 m), the coverage of all plots reached 100% in the end of May, 2007 (approximately 50 days passed after the first gemination of vegetation). The coverage of the plots using big hard stones and organic composts and the plots containing peat moss increased more rapidly. The results show that peat moss is effective to retain soil moisture and establish more sound environment for vegetation gemination.

• Korean Journal of Microbiology
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• v.20 no.4
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• pp.210-222
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• 1982

Coliphages isolated from Han-River from September 1980 to August 1981 were classified by morphological and physiological characteristics. Effects of soil metrial on the fate of coliphage in nature were investigated. 1. The correlation coefficient between coliphage and E.coli which was host of coliphages in nature was 0.7173 (p=0.004). 2. Coliphage I isolated from Han-River of which DNA molecular weight was $27{\times}10^6$ daltons was identified as $T_1$ phage and coliphage II of which DNA molecular weight $72{\times}10^6$ daltons was classified as $T_5$ phage. 3. Soil material SW was composed of 63.65% silt and 21.92% clay. Clay was consisted of illite, kaolinite and chlorite evenly. Soil material J was composed of 68.92% silt and 11.67% clay. Clay consisted of smectite only. 4. Coliphage was absorbed to soil material J more than soil material SW, and $T_1$ coliphage was absorbed to soil material more than $T_5$ coliphage was. 5. The phage adsorption efficiency to soil material was enhanced at lower pH : the phage adsorption efficiency at pH 4 was 27 time higher than at pH 7. 6. Divalent $(Ca^{2+})\;and\;trivalention\;(Al^{3+})$ enhanced the phage adsorption efficiency to soil material from 4 to 39 and from 17 to 91 times higher than monovalent $ion(Na^+)$, respectively. 7. The concentration of organic compound was inversely related to the phage adsorption efficiency to soil. 8. Adsorption of phage onto soil material, and elution efficiency of elutants was in the order of D.D.W>tap water>river water>seawater. 9. The higher the concentration of organic compound was, the more were adsorbed phages to soil eluted. 10. Coliphages survived longer in sterile soil suspension than in nonsterile soil material suspension.

• International Journal of Highway Engineering
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• v.20 no.4
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• pp.21-26
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• 2018

PURPOSES : The objective of this study is to evaluate the application of soil stabilization method for soft shoulder construction in the iRoad Project of Sri Lanka. METHODS : Firstly, the quantitative analysis of soil strength improvement due to soil stabilization was done for soil samples collected from iRoad construction sites. Two types of soils were selected from iRoad Project sites and prepared for soil stabilization testing by the Road Development Authority. Secondly, the appropriate stabilizer was selected at given soil type based on test results. Two different stabilizers, ST-1 and ST-2, produced in Korea were used for estimating soil strength improvements. Finally, the optimum stabilizer content was determined for improving shoulder performance. The uniaxial compressive strength (UCS) test was conducted to evaluate the strength of stabilized soil samples in accordance with ASTM D 1633. The use of bottom ash as a stabilizer produced from power plant in Sri Lanka was also reviewed in this task. RESULTS : It is found from the UCS testing that a 3% use of soil stabilizer can improve the strength up to 2~5 times in stabilized soft shoulder soils with respect to unstabilized soils. It is also observed from UCS testing that the ST-1 shows high strength improvement in 3% of stabilizer content but the strength improvement rate with increase of stabilizer content is relatively low compared with ST-2. The ST-2 shows a low UCS value at 3% of content but the UCS values increase significantly with increase of stabilizer content. When using the ST-2 as stabilizing agent, the 5% is recommended as minimum content based on UCS testing results. Based on the testing results for bottom ash replacement, the stabilized sample with bottom ash shows the low strength value. CONCLUSIONS : This paper is intended to check the feasibility for use the soil stabilization technique for shoulder construction in Sri Lanka. The use of soil stabilizer enables to improve the durability and strength in soft shoulder materials. When applying the bottom ash as a soil stabilizer, various testings should be conducted to satisfy the specification criteria.

• Korean Journal of Environmental Agriculture
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• v.41 no.2
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• pp.101-107
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• 2022

BACKGROUND: Soil amendment was necessary applied for the sand that had been used to root zone of green ground in golf course because of its low water retention power and cation exchangeable capacity. This study was conducted to evaluate the effect of the mixed ratio of peat moss and coconut coir as soil amendment materials on the soil physicochemical properties applied to rootzone based on sand. METHODS AND RESULTS: The soil amendments were blended at 0, 3, 5, 7 and 10% by soil volume. The pH in the peat moss treatment was lower than that of control (0% soil amendment), and pH and electrical conductivity (EC) in the coconut coir were higher. The blending ratio of peat moss was negatively correlated with pH of rootzone soil (p<0.01), and that of coconut coir positively with EC (p<0.01). As compared with control, capillary porosity, the physical factors such as air-filled porosity, total porosity, and hydraulic conductivity of rootzone soil were increased by applying peat moss and coconut coir. For correlation coefficients between percentage of soil amendments and soil physical factors, peat moss and coconut coir were positively correlated with porosity and hydraulic conductivity (p<0.01). CONCLUSION(S): These results indicated that the application of peat moss and coconut coir affected on the change of physicochemical properties of rootzone soil, and improved soil porosity and hydraulic conductivity.

• Korean Journal of Soil Science and Fertilizer
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• v.38 no.5
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• pp.247-252
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• 2005

Soil pH is an intensity factor of releasing hydrogen ion which is buffered by aluminum. It depends on pH buffer capacity of Al whether soil pH is governed directly by cations or not. A study was conducted to elucidate the pattern of pH changes by soil EC. Fertilizer and three kinds of organic manures composed of cow and pig and fowl dropping and one kind of rice straw compost were added independently into upland sandy loam soil. This treated soils and four upland soils under plastic film house having different levels in electrical conductivity (EC) were incubated with field capacity at $30^{\circ}C$ for 5, 10, 20 and 40 days. Soil pH varied directly as the cations contained in organic materials according to degree of saturating pH buffer capacity (pBC) of sandy loam soil. pH of the soils under plastic film house was lowered by soil EC due to governing by overplus of cation beyond pBC.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.89-98
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• 2010

Recently, many researches on bottom ash which is produced in the burning process of power plant are actively performed for its utilization for soil-subbase materials. In this paper, bottom ashes from 5 different power plants are prepared and several tests including compaction, CBR, and tri-axial compression are carried out for mixed bottom ash and weathered soil considering 3 replacement ratio of 30%, 50%, and 70%. Through the tests, CBR result over 20 are evaluated without plastic property, which shows availability of subbase material. With higher increase in replacement ratio of bottom ash, CBR of mixed soil increases due to the higher mechanical performance of bottom ash. However, replacement effects of bottom ash on friction angle and cohesion are evaluated to be little since bottom ash plays a little role in rearrangement of mixed soil. Bottom ash with a good mechanical property is evaluated to have reasonable bearing capacity which shows a good property for subbase materials.

• Journal of Soil and Groundwater Environment
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• v.16 no.4
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• pp.53-61
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• 2011

This study examined evaluation on stabilization of major and trace elements in tailings by various surface water-preventing materials. Six columns were filled with tailings of the Sinlim mine, then covered with tailings only, compacted soils, clay, soil-bentonite mixture, pozzolan and bentonite mat. After injection of artificial rain water, the leachate was sampled with times (3, 6, 9 and 12 pore volume) and analysed for major (Ca, Na, Mg, K) and trace elements (As, Cd, Cu, Pb, Zn) by ICP-AES. With exception to pozzolan type, the pH values of leachate from the other types became stabilized from 5.5 to 7.5, and EC (electric conductivity) of leachate from them decreased with times. For the pozzolan type, however, the pH and EC of leachate increased with time due to its alkalinity producing system. Concentrations of most major and trace elements in leachate decreased and stabilized with time. Consequently, soil-bentonite mixed cover shows the best ability of water-preventing and reducing mobility of elements in tailings site.