• 한국해양공학회지
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• 제26권6호
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• pp.33-38
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• 2012

In our study, a closed-type penetration unit for standard penetration test (SPT) equipment was developed in order to operate in an underwater environment. This type causes energy dissipation, mainly due to the small gap between an airtight case and moving hammer. The dissipation was estimated through a CFD analysis. The computed dissipated energy was less than 1.2% compared to the potential energy of the hammer with the given gap. Subsequently, the impact energy of the underwater SPT equipment was within 1.2% of that for the SPT equipment on land.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 가을 학술논문 발표대회
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• pp.144-145
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• 2021

This study analyzed the cases of cracks in piles due to the use of followers under construction conditions where water exists inside the piles, and confirmed whether the piles were cracked through a field test simulating the construction conditions in which water pressure inside the piles was generated by a hammer. According to the construction case, under the construction condition where the pile length is 20% to 30% shorter than the drilled length, about 80% cracks occur, so there is a high possibility of cracking due to water inside the pile. A field test was conducted to confirm the type of pile failure due to hammer under the construction condition in which water exists inside the pile. The pile head was not destroyed by the compressive load, and one or more longitudinal cracks occurred along the PC steel wire. The closed end pile generates water pressure by hammer. the follower and cushion(compression plywood) must be drilled at least 0.4D. It is expected that improved quality control will be possible as the water pressure inside the pile is reduced.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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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)

• 한국지반공학회논문집
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• 제16권3호
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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.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2005년도 제7회 특별심포지움 논문집
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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 $N_d$.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 가을 학술발표회 논문집
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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.

• 한국지반공학회지:지반
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• 제8권1호
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• pp.59-66
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• 1992

표준관입시험 결과인 N값은 여러가지 요소들에 영향을 받으며 그 중 함마의 낙하에너지는 가장 큰 영향을 주는 것으로 알려져 있다. 에너지 수준이 상이한 상태에서 측정한 N값을 표준값을 기준으로 한 일반적인 해석에 적용할 경우에는 기초의 안전을 위협하거나 과잉설계를 유발할 수 있다. 본 연구에서는 SPT 함마의 낙하속도를 측정 함으로써 함마의 낙하에너 지를 간접적으로 계산하였다. 분석 결과 우리나라의 N값은 국제적 인 표준 값으로 인정되는 Nu과는 차이가 있는 것으로 나타나 해석 또는 설계시 필수적으로 고려되어야 할 것으로 판단된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.910-921
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• 2004

In this study, the pilot tests on the reclaimed land were performed in order to find the suitable construction method with dynamic compaction Type I, Type II at different dynamic energy and hydraulic hammer compaction. The estimation of the compaction through the various pilot tests was performed by the CPT-qc, SPT-N and field density tests. As the result of the pilot tests, it shows that the dynamic compaction method is better than the hydraulic hammer compaction method in the effect of the ground improvement, especially dynamic compaction Type I is much superior to others. When it comes to method for measuring the intensity of the ground, the value of the cone penetration test-resistance(qc) is much suitable for the ground. Besides, the standards for the compaction control, which showed that over 10Mpa at 0 through 5meters in the upper layer and 7Mpa at 5 through 8meters in the lower layer in the CPT-qc, could be found without discrimination of the upper road and lower road on the reclaimed land. And it also found that the intensity of the reclaimed land gets back to the original status in about 10 through 15 days.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 가을 학술발표회 논문집
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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.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2002년도 춘계학술대회논문집
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• pp.197-203
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• 2002

The estimation of pile bearing capacity is important since the design details are determined from the result. There are numerous ways of determining the pile design load, but only few of them are chosen in the actual design. According to the recent investigation in Korea, the formulas proposed by Meyerhof based on the SPT N values are most frequently chosen in the design stage. In the study, various static and dynamic formulas have been used in predicting the allowable bearing capacity of a pile. Further, the reliability of these formulas has been verified by comparing the perdicted values with the static and dynamic load test measurements. Also in cases, these methods of pile bearing capacity determination do not take the time effect consideration, the actual allowable load as determined from pile load test indicates severe deviation from the design value. The principle results of this study are summarized as follows : A a result of estimate the reliability in criterion of the Davisson method, in was showed that Terzaghi & Peck > Chin > Meyerhof > Modified Meyerhof method was the most reliable method for the prediction of bearing capacity. Comparisons of the various pile-driving formulas showed that Modified Engineering News was the most reliable method. However, a significant error happened between dynamic bearing capacity equation was judged that uncertainty of hammer efficiency, characteristics of variable , time effect etc... was not considered. As a result of considering time effect increased skin friction capacity higher than end bearing capacity. It was found out that it would be possible to increase the skin friction capacity 1.99 times higher than a driving. As a result of considering 7 day's time effect, it was obtained that Engineering News. Modified Engineering News. Hiley, Danish, Gates, CAPWAP(CAse Pile Wave Analysis Program ) analysis for relation, respectively, $Q_{u(Restrike)}$ $Q_{u(EOID)}$ = 0.971 $t_{0.1}$, 0.968 $t_{0.1}$, 1.192 $t_{0.1}$, 0.88 $t_{0.1}$, 0.889 $t_{0.1}$, 0.966 $t_{0.1}$, 0.889 $t_{0.1}$, 0.966 $t_{0.1}$