• Journal of the Korean Geosynthetics Society
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• v.16 no.3
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• pp.31-39
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• 2017

Applicability of Skempton's and Hansbo's equation for estimating strength incremental ratio of Korean marine clayey soil was analyzed. These empirical equations have been commonly applied to design soft ground improvement by, especially, staged loading method. Strength incremental ratios proposed by Skempton (1954, 1957) and Hansbo (1957) using field vane tests(FVTs), measured in Scandinavia depends on plasticity index and liquid limit. Although lean clay in Scandinavia can be classified as clay based on USCS, this soil contains no clay mineral because it was produced by the glacial grinding of rock, sometimes, called rock flour. On the contrary, plasticity indices of Korean marine clayey soils increase linearly with the percentage of clay fraction (% finer than $2{\mu}m$ by weight). Except for strength incremental ratios using $q_u/2$ values in the case of soils having a low plasticity, such as Incheon, Hwaseong and Gunsan soils, these values are in the range of 0.25 to 0.35, independently of the plasticity index, $I_p$.

• Korean Journal of Soil Science and Fertilizer
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• v.35 no.5
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• pp.290-295
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• 2002

Fertilizer granulation test was carried out by a small pan granulator. A premixture composed of SOP 60%, urea 22% and RP powder 18% was rolled in the pan granulator while 10% phosphoric acid solution(binder) was sprayed on the rolling powder bed. Granules were developed very fast along with a little amount of binder. Hardness, brittle ratio in water and hygroscopicity of granules were improved enough to evaluate physical properties of the fertilizer. Growth responses of tobacco plant to the fertilizer were investigated at seedling and flowering stage by pot experiment under plastic film roof. Seedlings showed poor growth at nursery pot cell. In virgin soil with deficient available phosphate tobacco plant showed poor growth until budding and flowering stage but good growth in tillage soil with high cumulative phosphate.

• Journal of Environmental Impact Assessment
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• v.16 no.5
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• pp.319-325
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• 2007

Recently, since the risk on natural disasters is increasing due to abnormal weather such as the global warming, a need for a system on prior review on the influence of disasters has emerged in order to establish a solution by analyzing elements of disaster in advance. However, since the inherently destroying business namely the quarrying business is excluded from the range of subject business of Prior Review System on the influence of disasters, a correction for this is required. In order to actually explore how much risk it contains, actual outflow of soil and flood in the quarrying block where quarrying is being currently carried out was examined and the required undercurrent facility capacity which is also used as a grit chamber was investigated. In addition, by comparing the soil outflow of industrial complexes and golf courses which are current subject businesses of Prior Review on the Influence of Disasters and that of rock mountains relative risk level was examined. After investigation, it was found that the risk on occurrence of disasters was increased due to increase in outflow of soil and flood because of the change of land condition during and after development thus an adequate solution to decrease is required. In addition, after comparison with other business groups it was found that a significantly higher amount of soil is outflown in case of rock mountains thus it was analyzed that a solution to decrease is required. Therefore, a correction is immediately required in order to include quarrying business in the subject business of Prior Review System on the Influence of Disasters.

• Tunnel and Underground Space
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• v.27 no.5
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• pp.312-323
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• 2017

In this study, an influence of mixing ratio among firing oyster shell, non-firing oyster shell, magnetic separated converter steel slag and fly ash used as admixtures on strength properties of soil cement was evaluated by correlation analysis among compressive strength, deformation modulus and mixing ratio of admixtures. As a result, the strength of the specimens containing non-firing oyster shells was found to be larger than that of firing oyster shells, and it was confirmed that firing oyster shells could negatively affect the strength of soil cement specimens unlike previous studies. In addtion, there was a positive correlation between the ratio of magnetic separated converter slag and strength properties, so it is confirmed that it can be used as an admixture.

• Tunnel and Underground Space
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• v.15 no.5 s.58
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• pp.359-368
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• 2005

In case the overburden of a tunnel is too low to adopt NATM, cut and cover method generally can be chosen as alternative. However, in tunneling some area with very low or no overburden between two mountains, the cut and cover method requires additional construction of a couple of tunnel portals and the maintenance of portal slopes until backfilling is completed. As a solution for this problem, increasing the tunnel overburden by raising the ground level can be effective. This paper presents the case study for tunneling at C240 site in Taiwan High Speed Railway(THSR) in which soil-cement filling method was used for pre-banking before tunnel excavation. Cement content of filling material was $2\~4\%$ and thickness of filling a round was $130\~250\;mm$. The stability evaluation for the soil-cement slope and concrete lining of low cover tunnel was conducted by numerical analysis.

• Economic and Environmental Geology
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• v.5 no.4
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• pp.221-229
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• 1972

Through the series of study on the above subjects, the following were founded. 1. Soluble silica in paddy top-soil (xppm) and maxium possible yield (y) is expressed as following equatic $y=63.97+0.425x-0.00114x^2$ It is known that soluble silica in paddy top-soil in South Korea is limited as 130ppm. 2. Gnder the present Korean condition 90% of paddy-top-soil is estimated to be short in available silica content and the country average to only 78ppm. 3. The total area of Korean paddy-top-soil is about 1,036,710 ha. All requirements of wollastonite in South Korea estimated from the equation $Y=0.94-0.033{\times}$are about 2 million M/T 4. Silicates fertilizer minerals are Bentonite, Zeolite, Wollastonite, Serpentine, and Chlorite. But Wollastonite is most economic and can be supplied to using Korea. 5. Wollastonite is formed in contact metomorphic deposits. Limestone is the country rock of wollastonite. Limestone in Korea is in Ryunchcon system, (Pre-cambrian) Okcheon system, (unknown), Great limestone series (paleozoic), Hongjum series (Paleozoic) and Kyungsang system (mesozoic) so that the zones of these limestone and igneous rock are the possible area which wollastonite can be produced. 6. According to the published geologic map (scale 1/5000), about 25 provinces will be possible area which wollastonite can be produced. In future, I believe that many possible area will be increased. 7. According to this survey at Danyang, total wollastonite resources are about 179,000 M/T and average of soluble $SiO_2$ is 29.84%. 8. According to this survey at Daijeon, total resources are about 57,600 M/T and average of soluble $SiO_2$ is 21.53%. 9. Total wollastonite resources including Danyang, Yangduk, and Daijeon are about 1,172,200 M/T. Considering possible resources, it will be over 20 million M/T and I can say that it is possible to be supply for a score.

• Journal of Korean Society of Forest Science
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• v.111 no.2
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• pp.263-275
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• 2022

We conducted this study to provide essential data for implementing restoration measures on the physical properties of the geology, topography, and soil of the landcreep areas in Yangpyeong-gun, Gyeonggi-do. The strata of the survey area comprised topsoil, weathered soil, weathered rock, and soft rock layers. The landcreep area, caused by colluvial debris, was located in a convex topography shape distributed as bedrock with shales and incorporated with sandstone. According to the measurement of the displacement meter, the surveyed area has crept from 1.1 mm to 6.5 mm during the recurrent landcreep between 1 July and 27 August, 2020. The landcreep had progressed over two directions (S65° W, E45° S, and E70° S) which were similar to the groundwater flow direction (E82.5° S and S16.8° W). The average slope of the landcreep area occurred on a gentle slope (19.3°), lower than the average slope of the mountain area (25°) in Korea. The bulk density in the groundwater areas was lower than that in other surveyed areas.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3C
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• pp.167-178
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• 2008

Rainfall-induced slope failures were simulated by seepage and stability analyses for actual slopes of weathered soils. After undisturbed sampling and testing on a specimen of unsaturated conditions, a seepage analysis was performed under actual rainfall and it was found that the pore water pressure increased at the boundary of soil and rock layers. The safety factor of slope stability decreased below 1.0 and the failure of actual slope could be simulated. Under design rainfall intensity, the seepage analysis could not include the effects of the antecedent rainfall and the rainfall duration. Due to these limitations, the safety factor of slope stability resulted in above 1.0, since the hydraulic head of soil layers had not be affected significantly. In the analysis of another slope failure, the parameters of unsaturated conditions were evaluated using artificial neural network (ANN). In the analysis of seepage, the boundary of soil and rock was saturated sufficiently and then the safety factor could be calculated below 1.0. It was found that the failure of actual slope can be simulated by ANN-based estimation.

• Tunnel and Underground Space
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• v.33 no.5
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• pp.373-387
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• 2023

Scientific exploration of extraterrestrial planets has gripped human imagination since the advent of space travel. Human missions to Mars could produce insight into the essential questions of how, when and where life began on Earth. Such missions would only be feasible using local space resources materials, a concept called in situ-resource utilization (ISRU). The purpose of this paper is to provide a thorough review of the currently available Mars soil simulants and to determine those with geotechnical properties most appropriate for vehicle mobility studies. Sourcing and processing are considered since full-scale studies require bulk quantities of material on the order of tens of tons. This review identifies the simulants with the highest fidelity to Mars wind drift soils. In addition, recommendation guide for mars soil simulant development made.

• Korean Journal of Soil Science and Fertilizer
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• v.27 no.4
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• pp.247-254
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• 1994

This study was conducted to characterize the chemical and mineralogical properties of representative phosphate rocks from North Carolina and Florida, and to find out the method for increasing the citric acid (two percent) solublility of phosphate rock. The the results are summerized as follows : 1. Major composition of phosphate rock was carbonate apatite containing small amounts of calcite and quartz. The differential thermal analysis(DTA) did not show endothermic or exothermic peak till $1,000^{\circ}C$. 2. Two percent citric acid solublility of phosphate rock was increased with the finess of particle size, but the water solublility was not affected by the particle size. Long time calcinated under high temperature had negative effect, while the incubation with 2% citric acid under low temperature had positive effect on solubility. 3. To increase the solubility of phosphate rock it was mixed with farmyard and barnyard manure and acidulated. Citrate solubility by treatment with sulfuric acid was more effective than nitric acid. Acidulation with thirty percent sulfuric acid increased both citric acid solubility and water solublility. Treatment with glutamic acid had little effect on the solubility of phosphate rock.