• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1359-1364
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• 2008

It is well known that the standard penetration test (SPT) has been used in all over the world to get geotechnical properties of the ground. However, it is difficult to apply the SPT to the dense sand, gravel, weathered rock, etc. For the application of the SPT in these grounds, it is necessary to change in the diameter and the impact energy of the SPT. For the improvement of site investigation technology, Large Penetration Testing device (KICT-type LPT) was developed and applied to the in situ condition. The drop height and weight of the hammer in developed system were decided as 760mm and 150kg, respectively. And the developed sampler has the inner diameter of 63 mm and the length of 500 mm with the adjustment of energy ratio to the SPT of 1.5. In this study, the performance of KICT-type LPT was evaluated by using a calibration chamber system and pile driving analyzer (PDA)

• 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.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.09a
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• pp.3-9
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• 2005

In order to obtain more reliable data for the information on the ground, a new site Investigation method is proposed, in which seismic waves (S-waves) generated by the Swedish Ram Sounding Test (SRS) are used. It is indicated that the energy transferred from the hammer to the rod in SRS's is much more stable, compared to SPT's. A series of SRS with measurements of seismic waves at the ground surface were carried out to clarify the characteristics of seismic wave propagation in the ground. As the results of comparison between seismic S-wave amplitudes and $N_d$ (blow count for 20 cm penetration in SRS), it was found that amplitudes of S-waves generated by SRS correlate well with $N_d$. The amplitude of the S-wave is thought to be more adequate parameter for the soil strength and rigidity than $N_d$.

• Journal of the Korean GEO-environmental Society
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• v.12 no.10
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• pp.13-22
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• 2011

In this study, features of correlation between S-velocity and N value are derived from 9 suspension PS layers in Chungcheong Buk-do. S-velocity to be measured on Chungcheong Buk-do is classified into 5 as conditions of stratum that are ; cohesive soil layer, sandy soil layer, gravel layer, weathering soil layer, weathered rock layer. Each correlation formulas between N value by SPT and S-velocity is proposed from these classifications. And correlation formula for whole soil body except weathered rock layer also is proposed for reference. Corelation formulas developed this study formed square expression considering existing formulas produced internationally. Strength parameter converted to linear if N value is more than 50. Features of proposed formula which came up with comparative analysis of international result of cohesive soil layer and sandy soil layer and gravel layer show similar to existing ones. But there is deference that result of correlation formula for weathered rock layer is a little smaller than domestic formula's one. Because correlations of weathered rock layer above the N value of 50 is converted into a linear formation.

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.133-152
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• 1999

The cyclic triaxial test was carried out to research liquefaction characteristics and sample disturbance effects of silty sand soils at the west coast in Korea. First, liquefaction in silty sand was generated when axial strain approached to $\pm10%$ of strain and behavior of pore pressure was similar to the formula suggested by Seed, Martin, and Lysmer(1975). Also, it was found that dilatancy was generated at failure. Secondly, the liquefaction evaluation methods suggested by many researchers were carried out and the results were compared. In these methods the weak depth in liquefaction was similar and the method carried out by cyclic triaxial test on remolded sample showed the least safety factor. Thirdly the stress ratio by cyclic triaxial test was compared with that obtained from SPT N-value as a kind of empirical methods. It was found that the effect of sample disturbance was relatively small when SPT N-value was less than 20, but there were large differences in safety factor and resistance of liquefaction in soil by the effects of disturbance and remolding when SPT N-value was more than 20.

• Journal of the Korean Geotechnical Society
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• v.29 no.10
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• pp.39-48
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• 2013

This paper presents an equation to depict the penetration behavior during the standard penetration test (SPT) in sandy deposits. An energy balance approach is considered and the driving mechanism of the SPT sampler is conceptually modeled as that of a miniature open-ended steel pipe pile into sands. The equation consists of three sets of input parameters including hyperbolic parameters (m and ${\lambda}$) which are difficult to determine. An iterative technique is thus applied to determine the optimized values of m and ${\lambda}$ using three measured values from a routine SPT data. It is verified from a well-documented record that the simulated penetration curves are in good agreement with the measured ones. At a given depth, the increase in m results in the decrease in ${\lambda}$ and the increase in the curvature of the penetration curve as well as the simulated N-value. Generally, the predicted penetration curve becomes nearly straight for the portion of exceeding the seating drive zone, which is more pronounced as soil density increases. Thus, the simulation method can be applied to extrapolating a prematurely completed test data, i.e., to determining the N value equivalent to a 30 cm penetration. A simple linear equation is considered for obtaining similar results.

• Journal of the Korean Geotechnical Society
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• v.16 no.3
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• pp.119-129
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• 2000

국내에서 가장 많이 사용되는 현장조사방법인 표준관입시험의 결과로 얻어지는 N값에 대해 가장 큰 영향을 미치는 롯드 에너지 전단률(깽 Energy Ratio)을 지반조건이 상이한 3개 현장에서 항타분석기(Pile Driving Analyzer)를 이용하여 실측하였다. 에너지 전달률에 영향을 미치는 요인들 중엣 해머의 종류, 로프의 상태, 자아틀에 감은 횟수 등의 조건을 달리하여 롯드 에너지 전달률에 미치는 영향을 측정/분석하였다. 실험결과에 의하면 도넛해머, 안전해머, 개량형 도넛해머(Modified Automatic Donut Hammer)는 롯드에너지 전달률이 각각42%, 66%, 57% 정도로 측정되었으며 로프의 상태와 자아틀에 감은 횟수는 상대적으로 영향이 적은 것으로 측정되었다. 실험결과를 바탕으로 실측된 N값을 해머의 이론적 위치에너지의 60%에 해당하는 에너지가 롯드에 전달되었을 때의 N값(N60)으로 변환하기 위한 식을 제안하였다.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.477-484
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• 2001

In this paper shows the evaluation of the liquefaction potential of soils using in situ test. There are different types of in situ test used in the evaluation the liquefaction potential. In the particular study the Standard penetration test(SPT), Cone penetration test(CPT), ad Seismic cone penetration test (SCPT) were used. The SPT N value has been used all over for a very long time. The evaluation of the liquefaction of soil was preformed using the worldwide renowned CPT and SCPT. Shake 91 program was used to evaluate the results obtained by different in situ test and were later analyzed.

• 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.

• Geotechnical Engineering
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• v.8 no.2
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• pp.21-30
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• 1992

Though the pile skin friction can take substantial amount of load carrying capacity, it has often been ignored in the design. Even when the pile skin friction is taken into consideration, it is questionable about the reliability of estimating it. It has been even worse in Korea. since in most cases the available information is only the SPT N values and not much information has been known about the correlation between N value and the pile skin friction in residual soils. With SPLT (Simple Pile Loading Test) it is possible to measure the pile skin friction separately from the tip resistance. In this research, results of the measured pile skin friction in residual soils are analysed. And a new design correlation based on SPT N value is proposed.