• Water for future
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• v.15 no.2
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• pp.23-32
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• 1982

This study is to clarify the relation between the maximum 24 hour rainfall and the daily rainfall of a designated time 10 A.M., using the 506 rainfall datum from 32 rain-guage stations on the Han river basin covering a period of 7 years and trying to estimate the ratio of two data in accordance with the amount of rainfall respectively. The Mononobe's formula, which is widely used in this country, has the value of 2/3 power in it. The "n" was considered instead of 2/3 and derivated for each guaging station. The results make it possible to establish the Ison-n value map, and show that the n value is affected mainly by the topographical conditions. The daily rainfall of a designated time can be modified by the results of this study and expressed as Y(%)=218.25/R$$. But in the case of exceeding 200mm/day, it is recommended to use the 110% for safety. On the problems of intensity-duration concerned with the planning of public works, the formula can be expressed as r$$=fRday/24.(24/t)$$, where "f" is Y(%) divided by 100. As this study was done with the datum within shor period, it is necessary to study more about the "n" and "f" value so as to get previse value in the future.o as to get previse value in the future.

• Korean Journal of Soil Science and Fertilizer
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• v.7 no.3
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• pp.147-154
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• 1974

Relationship among grain yield (Y) nitrogen efficiency (E) and nitrogen uptake amount (N) was investigated using the data from Korea and Japan in order to find out the way of increase nitrogen efficiency. The relationship between E and N could be grouped in various classes. In each class the equation. Y=EN=(b-aN)N, is valid where b is a theoretical maximum of E and a is the E/N at theoretial maximum yield. Present technique for high yield in the rice research seems to achieve 56.8 of nitrogen efficiency with 15.5kg of nitrogen uptake. Future target appears to be 63 of efficiency with 17kg of nitrogen uptake at which some farmers in Japan might reach already. It seems that the increase of nitrogen uptake for high yield is restricted without increase of nitrogen efficiency. The increase of efficiency and uptake amount of soil nitrogen seems essential to increase total nitrogen efficiency.

• The Journal of Engineering Geology
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• v.5 no.2
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• pp.167-179
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• 1995

The only three elements such as RQD, N -value and Es were used as a quantitative standard for the design of supporr pattern determidetion on subway line 8th in Seoul. Because the support pattern that was obtained by these elements could not he determined on the basis of the quantitative of geology and the orientations and properties of discontinuity planes, there have been some problems in determining the economic support pattern and tunnel stability. Therefore, in an attempt to determine the stable and economic support pattern with more quantitative elements, more flerrible rock mass classification with geologic conditions was performed by using RMR at 1745 sections and Q-system at 374 sections within Seongnam block on subway line 8th. Then, rusults by these two methods were compared with standard support pattern of the subway line 8th. Moreover, relationships between geology, geologic structures and topography to rock mass grades were studied. According to the rusult of this study, it is judged that the standard support pattern designed with PD-4 or PS - 4 should have been subdivided into 4~6 support patterns. Some sections where geologic structures such as faults and joints are developed tend to have rock mass grades. And they also have low rock mass grades near valley. On thr other hand, they show intermediate grades at piedmont area and the greatest ones at high mountains.

• 기술발표회
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• s.2006
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• pp.261-269
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• 2006

Recently, piezocone penetration test is frequently used in order to estimate the characteristics of soft ground with standard penetration test; generally used in the past In this study, standard penetration test, piezocone penetration test, driving resistance of vertical drain were used in order to increase the confidence for determination of soft ground depth. And the compressible layer was determined by the comparison between the preconsolidation pressure and the designed increase pressure. As the results, the relation between standard penetration test and piezocone penetration test shows $q_c$=(1.09~1.63)N at the soft ground, determined by 5/30 N value. And $q_c$(1.21~1.98)N was shown at the point of compressible layer, evaluated by the preconsolidation pressure. And driving resistance of vertical drain is 70 f/$cm^2$ which is equal to 10kgf/$cm^2$ cone penetration resistance.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1472-1477
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• 2009

The landfill ground that consists of sandy soil or contains boulder or has waste ground such as waste landfill can be often applied by dynamic compaction method considering quick construction and economic advantages. In this study, the improvement efficiency of the dynamic compaction method that is used on the waste disposal ground of Tague Freight Terminal constrution site is analyzed. The results show that the N values are increased from 6.5/30 to 22.5/30, which is 3.5 times increase compared with the N value before dynamic compaction. The amount of settlement is in the range of 0.706~1.729m. the $\alpha$ vlues suggested by Leonards et al.(1980) was about 0.25~0.48, which are quite similar to to not only 0.3~0.5 of the findings of waste layer of the Society of Soil Engineering of Japan (1987) but also 0.35~0.4 of that of mine waste of Lukas (1986).

• Korean journal of applied entomology
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• v.24 no.4 s.65
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• pp.173-177
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• 1986

This study was carried out to see what makes the 'dark grey cutworm', Agrotis tokionis Butler, inflict less damage in P.E. film-mulched tobacco fields than in nonmulched ones. In field plot experiment, the damage ratio of tobacco seed lings in mulched plots(m) was reduced by 63% compared with that in non mulched ones(n). The altered environments did not affect the cutworm in mortality, which was confirmed by recovery ratio, location of larvae in soil, and developmental age. But the m/n value and damage ratio in plots of different mulching methods strongly suggest that the P.E. film itself prevent larvae from cutting the plants. Larval mortality was rapidly increased between the end of July and the end of August.

• Geophysics and Geophysical Exploration
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• v.21 no.3
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• pp.162-170
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• 2018

The purpose of this study is to understand the ground change of large scale mountainous region and to estimate the active weak zone using geophysical exploration (electrical resistivity and refraction seismic explorations) in large scale deep landslide area located in Wanjugun, Jeollabukdo. We also analyzed the characteristics of deep landslides occurred in metamorphic rocks region and confirmed the approximate scale. As a result of comparative analysis of N-value by standard penetration test (SPT), low resistivity anomaly, and tension crack identified from field investigation, a discontinuity in soil layer was estimated at 10 ~ 15 m below the surface. Based on this results, the distribution pattern of active weak zone was confirmed between the discontinuity in soil layer and estimation line of bedrock.

• Journal of the Korean Geotechnical Society
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• v.31 no.12
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• pp.5-15
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• 2015

The GCP (Granular Compaction Pile) for the improvement objective of soft ground has been frequently studied. However, these studies were the results deduced on the basis of the numerical analysis and the laboratory model tests, and there was no study method to apply the effects of the bulging failure of a flexible pile. In this study, the sensitivity of the load-settlement curves of the uniform and the tapered GCP dependant on the geotechnical parameters estimated from N value of standard penetration test (SPT) was analyzed. It was estimated reasonably that, in the very soft clay soil (N=3 or less), elastic modulus was 700~2000 kPa and Poisson's ratio was 0.40~0.48.

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.43-58
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• 2018

In this study, the load-transfer behavior along the shaft of the prebored and precast piles was investigated by pile loading tests. Special attention was given to quantifying the skin frictions developed between the pile-soil interfaces of the 14 instrumented test piles. Based on this detailed field tests, the load - settlement curves and axial load distributions of piles were obtained and the load-transfer curves (t-z curves) for the test piles were proposed. As such, it is found that the test results show two different load transfer behaviors; ductile and brittle behavior curves. The corresponding t-z curves are proposed based on the hyperbolic- and sawtooth-shape, respectively. By validating the accuracy of the proposed curves, it is also found that the prediction results based on the proposed load-transfer curve are in good agreement with the general trends observed by the field loading tests.

• Journal of the Korean Geotechnical Society
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• v.36 no.12
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• pp.35-43
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• 2020

Currently, cofferdams of circular cross section are widely applied as temporary facilities for the installation of bridge foundations in river/sea bridge construction in Korea. Existing caisson, sheet pile, and cell type cofferdam are widely used, but these methods take a lot of time and cost for installation and dismantling. In the case of the existing sheet pile construction method, attention is needed to secure internal and external stability because of the damage to the sheet pile due to ground penetration and difficulty in connecting element members. In this study, penetration design of circular steel pipes using suction pressure was performed on the soft ground of the west coast, and it was confirmed that penetration construction using suction pressure was possible through field tests. It was confirmed that applying the ground analysis results using the cone penetration test (CPT) to the design rather than the standard penetration test (N value) results more similar to the field test results. In addition, it was confirmed that local failure of the inside of the cofferdam was induced when a suction pressure higher than the upper limit suction pressure was applied in the silty sand.