• Journal of the Korean GEO-environmental Society
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• v.5 no.3
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• pp.61-70
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• 2004

N-value by the SPT is one of the key parameter for settlement evaluation. However, if the ground is firm, the usual N-value is not blow count of 30cm depth penetration. In such case, if N-value is more than 50 with 30cm penetration, the N-value 50 is applied for settlement analysis. Therefore, in this study, the modified method of N-value estimation is suggested and compared the settlement by Elastic Theory, and the measured field data by Plate Load Test. As the result of this study, it is shown that the settlement by Elastic Theory with the modified N-value is more accurate than settlement by usual N-value. The application of Elastic Theory for pure sand is also evaluated in this paper.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.10a
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• pp.241-264
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• 2001

Due to the variation of equipments and test procedure, level of energy transferred to split spoon sampler varies and thus measured N value. Since the properties and parameters are estimated from empirical correlations related to N value, the correction of N value with respect to specific energy level is essential. Factors affecting N value are discussed and the results of previous studies on energy correction of SPT N value is reviewed. Part of results from joint research works with KHC are presented and the range of energy levels for the hammer and release system typically used in Korea is suggested.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.10a
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• pp.293-298
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• 2001

N-value is usually used to assume the displacement depth of embankment on the soft marine clay. But N-value of the soft marine clay tend to underestimate unlike overestimating of general cases. In general case, if the length of rod is more long then N-value is more large because it is under the influence of energy loss of hammer blow. So it is reasonable to correct N-value down. But in the case of soft marine clay, N-value must not be correct down. Especially to assume the displacement depth of embankment on the soft marine clay, it must be used laboratory test results or CPT, Vane Test than N-value. In this study, it is compared with two field cases that design displacement method of embankment.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.784-791
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• 2008

This study is to evaluate the characteristics of bearing capacity for granite soils by N-value. The partial data is investigated for practical evaluation of weathering degree and bearing capacity on granite soils. The settlement is linearly decreased when the N-value is less than 50, but the settlement isn't constant when the N-value is more than 50. This is the affect of ground water. Therefore ground water is detailed evaluated. The bearing capacity is linearly increased when the N-value is less than 30, is inactively increased when the N-value is between 30 to 50, is constant when the value is more than 50.

• Journal of the Korean Institute of Telematics and Electronics
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• v.13 no.4
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• pp.18-23
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• 1976

We have obtained the solution of van der Pol's equation characterized by an arctangent nonlinearity, using the perturbation method by writing periodicity conditions: $$X^{(n)}(2{\pi})-X^{(n)}(0)=0$$ $$X^{(n)'}(2{\pi})-X^{(n)'}(0)=0 (n=0,1,2......)$$ together with the starting condition: $$X^{(n)}(\frac{\pi}{2})=0,\;X^{(n)}'(\frac{\pi}{2})=-R^{(n)}$$. Our results agree with Liapunov's theorem and our calculated value is more similar to Murata's measured value than Murata's calculated value.

• Journal of the Korean GEO-environmental Society
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• v.6 no.3
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• pp.25-34
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• 2005

The governing design point of shallow foundation is not its bearing capacity but its settlemen and N-value by the SPT is one of the key parameters for settlement estimation. However, if the N-value is more than 50/30, such as 50/10 or 50/20, the N-vlaues are not blow count of 30cm depth penetration. In these cases, the estimated settlements have big difference with the measured values because the applied maximum N value for the settlement estimation is 50. Therefore, in this study, the modified method for N-value estimation is suggested. The settlements by four methods, which are based on Elastic Theory with application of modified N-value, are compared with the Origina Plate Load Test data. The same comparision was carried out with another seven Empirical Methods. The result of this study showed that the error range of settlement is decreased from 260.4~2136.5% to 20.3~272.7%. Among four methods which are based on Elastic Theory, the original method by Elastic Theory is the most accurate with the application of modified N-value. Among Empirical Methods, Terzaghi-Peck's(1948, 1967) modified method 1 is the most accurate with the application of modified N-value. The differences between the original method by Elastic Theory and Terzaghi-Peck's(1948, 1967) modified method 1 are neglectable.

• Journal of applied mathematics & informatics
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• v.27 no.1_2
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• pp.205-215
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• 2009

Sufficient conditions for the existence of at least one solution of the boundary value problems for higher order nonlinear difference equations $\{{{{{\Delta^n}x(i-1)=f(i,x(i),{\Delta}x(i),{\cdots},\Delta^{n-2}x(i)),i{\in}[1,T+1],\atop%20{\Delta^m}x(0)=0,m{\in}[0,n-3],}\atop%20\Delta^{n-2}x(0)=\phi(\Delta^{n-1}(0)),}\atop%20\Delta^{n-1}x(T+1)=-\psi(\Delta^{n-2}x(T+1))}\$. are established.

• Journal of Environmental Science International
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• v.4 no.5
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• pp.469-479
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• 1995

The increase of population and industrial activities had brought into eutrophication in the Nakdong river. A remarkable acceleration of eutrophication brought about serious problems for water supply. Therefore, for the purpose of conservation of water quality in the Nakdong river it is necessary to control nutrients. MBOD method was use to evaluate algal growth limiting factor and algal growth potential in the Nakdong river from June to August 1994. The modified biochemical oxygen demand(MBOD) depends on the amount of available inorganic nutrient and organic substrate during 5 day incubation in the dark at 2$0^{\circ}C$. The MBOD assay depends on inorganic nutrients such as P and N as well as reduced carbon and called the MBOD, the MBOD-P, and the MBOD-N, respectively. The results of bioassay by MBOD(Modified BOD) method showed that the MBOD, MBOD-P and MBOD-N value were found to be in the ranges of 3.8~96.0 mg$O_2$/l, 5.6~94.0 mg$O_2$/l and 42.0~220 mg$O_2$/l, respectively. And the the bioassay value was found to be the highest in Koryong area and the lowest in Waekwan area throughout the Nakdong river. The variations of MBOD-P and MBOD-N value showed similar tendencies to the variations of phosphorus and nitrogen value, respectively. By MBOD method, the relationships of MBOD, MBOD-P and MBOD-N value were MBOD ≒ MBOD-P 《 MBOD-N. The MBOD value was nearly equal to the MBOD-P value, and the MBOD-N value was 3 to 20 times more than the MBOD-P value, approximately. Therefore, in the Nakdong river, phosphorus was the limiting factor for algal growth during summer season. The algal growth potential as the concentration of chlorophyll-a in the summer was maximum 5 times more than standing crop as it.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.385-386
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• 2023

In this application study, field pilot tests were performed to evaluate the validity of a proposed formula between the exerted electrical energy and SPT N-value based on the result of the basic study. Measurement sensors and recording system were developed to obtain exerted motor current and drilling depth in a field. By using the correlation formula proposed in the basic study, the measured motor current and boring speed were applied to predict SPT N-value and the predicted N-values were compared to SPT N-value of site exploration. From the comparisons it is verified that the exerted electrical energy to bore ground might be used to predict SPT N-value and pile tip location.

• Journal of the Korean Geosynthetics Society
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• v.11 no.4
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• pp.55-62
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• 2012

In this application study, field pilot tests were performed to evaluate the validity of a proposed formula between the exerted electrical energy and SPT N-value based on the result of the basic study. Measurement sensors and recording system were developed to obtain exerted motor current and drilling depth in a field. By using the correlation formula proposed in the basic study, the measured motor current and boring speed were applied to predict SPT N-value and the predicted N-values were compared to SPT N-value of site exploration. From the comparisons it is verified that the exerted electrical energy to bore ground might be used to predict SPT N-value and pile tip location.