• Smart Structures and Systems
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• 제34권1호
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• pp.63-72
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• 2024

In-situ penetration tests using dynamic penetrometers are widely used for estimating soil resistance. Additionally, these dynamic penetrometers have been instrumented to improve tests accuracy. This paper introduces smart instrumented dynamic penetrometers and discusses experimental studies for various cases. An energy monitoring module was developed to enhance the dynamic penetration tests. The standard penetration test (SPT) and instrumented dynamic cone penetrometer (IDCP) tests were conducted using the energy monitoring module. Dynamic responses obtained by the energy monitoring module were used to calculate the transferred energies into the rod head and tip to correct the evaluation of ground strength. In addition, a crosshole-type dynamic penetrometer (CDP) was developed to measure the penetration index and shear wave velocity simultaneously to estimate the strength and stiffness of ground. The results of this study indicate that smart instrumented dynamic penetrometers may be effectively used to characterize the strength and stiffness of ground.

• 한국농공학회논문집
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• 제65권5호
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• pp.1-11
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• 2023

Due to climate change and aging of reservoirs, damage to embankment slopes is increasing. However, the safety diagnosis of the reservoir slope is mainly conducted by visual observation, and the time and economic cost are formidable to apply soil mechanical tests and slope stability analysis. Accordingly, this study presented a predicting method for the compaction and strength characteristics of the reservoir embankment soil using a portable static cone penetration test. The predicted items consisted of dry density, cohesion, and internal friction angle, which are the main factors of slope stability analysis. Portable static cone penetration tests were performed at 19 reservoir sites, and prediction equations were constructed from the correlation between penetration resistance data and test results of soil samples. The predicted dry density and strength parameters showed a correlation with test results between R² 0.40 and 0.93, and it was found to replace the test results well when used as input data for slope stability analysis (R² 0.8134 or more, RMSE 0.0320 or less). In addition, the prediction equations for the minimum safety factor of the slope were presented using the penetration resistance and gradient. As a result of comparing the predicted safety factor with the analysis results, R² 0.5125, RMSE 0.0382 in coarse-grained soil, R² 0.4182 and RMSE 0.0628 in fine-grained soil. The results of this study can be used as a way to improve the existing slope safety diagnosis method, and are expected to be used to predict the characteristics of various soils and inspect slopes.

• 한국지반신소재학회논문집
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• 제18권4호
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• pp.299-306
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• 2019

본 연구에서는 층 다짐으로 조성된 지반을 모사한 모형실험에서 지반 공동 발생 시 지반의 이완영역 범위를 추정하기 위해 제작된 이완영역탐지기를 통해 이완영역을 측정하고자 하였다. 세립분과 조립질 토사를 조성한 층상구조로 구성된 지반에 대해 콘 직경의 크기에 따라 영향을 받는 것을 확인하였으며, 이에 따른 적절한 콘을 선정하기 위해 크기효과 실험을 수행한 결과 적절한 초소형콘을 설정할 수 있었다. 또한, 본 연구에서 적용된 LAD를 이용하는 경우 실내모형실험 지반의 다짐정도에 따른 경계면 및 상대밀도 차에 의한 관입저항치의 급격한 변화에 따라 지반의 이완상태를 파악할 수 있었다. 지반내 관입저항특성을 통해 공동주변부에서 발생하는 이완영역의 범위를 추정하였으며, 이완영역에서 관입저항력의 감소율을 통해 파괴 발생 영역을 확인하였다.

• 한국지반신소재학회논문집
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• 제16권1호
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• pp.73-83
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• 2017

모래 및 실트 함유량이 우세한 서해안 저소성 지반(인천, 화성, 군산)에서 실시된 실내 및 현장시험으로부터 얻어진 비배수전단 강도를 이용하여 피에조콘계수(Nkt)를 분석한 후, 이에 대한 적용성을 평가하였다. 인천, 화성 및 군산지역에서 얻어진 일축압축 강도에 의한 콘계수(Nkt)는 19~23, 간이 CU 강도에 의한 값은 13~13.8, 현장베인강도에 의한 값은 11.6~13.1로 평가되었다. 이는 저소성 실트 지반조건에서 일축압축강도가 과소평가되는 원인에 의한 것으로 간이 CU 강도 적용조건과 비교했을 때 콘계수(Nkt)가 약 1.8배 전후로 커지며 분산되는 경향을 나타냈다. 저소성 실트 지반에서 수행된 CPTU 데이터를 이용하여 콘계수(Nkt)를 평가할 때에는 지반의 입도분포, 액소성한계 등의 물리적 특성, 지층 내의 sandseam 분포 등으로 인한 콘선단저항(qt) 및 주면마찰력(fs)의 불규칙한 분포, 간극수압계수(Bq)를 종합적으로 분석하여 수행하는 것이 바람직할 것으로 판단된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 연약지반처리위원회 학술세미나
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• pp.59-70
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• 2000

본 연구에서는 콘관입속도가 콘관입시험 결과에 미치는 영향을 연구하기 위하여 LSU/CALCHAS(Louisiana State University Calibration Chamber System)를 이용한 미니 Piezocone의 관입시험이 수행되었으며 그 결과를 비교 분석하였다. 10회의 미니 Piezocone 관입시험이 Ko 조건에서 수행되었으며 33% kaolin, 67% sand mixture가 시료로 사용되었고, 콘관입속도 0.3, 0.6cm/sec, U1(filter element at the cone tip), U2(filter element above the cone base), OCR=1, 10 의 조건이 다양하게 적용되었다. 시험결과 Cone Resistance, Excess Pore Water Pressure, Sleeve Friction 은 U1, U2 두 종류의 콘에 대해서 모두 관입속도가 커짐에 따라 증가하였으나 OCR의 증가에 따라서는 감소하였으며 U1의 Excess Pore Water Pressure가 U2 경우보다 크게 측정되었다.

• Structural Engineering and Mechanics
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• 제16권1호
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• pp.47-62
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• 2003

The nonlinear dependence aspect of various conical tool indentation parameters leading to an optimum tool semi angle value for easiest perforation is plotted and discussed explicitly in this work with the conclusion that tool angle has an optimum response towards most of the indentation parameters. Around this optimum angle, the aluminium sheets showed minimum fracture toughness as well as minimum work input to overcome the offered resistance. At the end, the mechanism leading to this phenomenon is presented with the conclusion that plastic flow dominates as the dimple semi cone angle reaches 35 and both pre and post plastic flow perforations lead the tool semi cone angle value towards this dimple cone semi angle of plastic flow initiation for its optimum performance. It is also concluded that specimen material failure is solely under tensile hoop stress and hence results into radial cracks initiation and propagation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.44-49
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• 2004

The settlements of footings in send are often estimated based on the results of in-situ tests, particularly the standard penetration test (SPT) and the cone penetration test (CPT). In this paper, we analyze the load-settlement response of vertically loaded footings placed in sands using both the finite element method with a non-linear stress-strain model and the conventional elastic approach. Calculations are made for both normally consolidated and heavily overconsolidated sands with various relative densities. For each case, the cone penetration resistance qc is calculated using CONPOINT, a widely tested program that allows computation of qc based on cavity expansion analysis. Based on these analyses, we propose a procedure for the estimation of footing settlement in sands based on CPT results.

• 한국지반공학회지:지반
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• 제14권1호
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• pp.71-80
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• 1998

서해안에 위치한 서산지역에서 연구용 prestressed concrete 말뚝을 3본을 설치하고 주변에서 콘관입시험을 수행하여 말뚝의 주면마찰력을 추정하는 연구를 수행했다. 본 연구에서 이용한 말뚝 지지력 산정식은 세계적으로 많이 이용하고 있는 Schmertmann방법, Tumay & Fakroo방법 및 프랑스의 LCPC방법을 이용하였다. 콘관입시험의 측정결과를 이용하여 3가지 방법으로 예측한 말뚝 의 주면마찰력과 현장에서 수행한 정역학적 재하시험 및 동재하시험에서 산정된 주면마찰력과의 비교하여 3가지 예측방법들에 대한 신뢰성을 평가했다. CPT를 이용한 3가지 예측식으로 산정한 말뚝의 주면마찰력은 전체적으로 25일과 42일이 지난후 수행한 정재하시험에 의한 주면마찰력을 상당히 과소평가했으나, 항타시좌 말뚝설치후 2주가 지난 시점에 수행한 동재하시험결과와는 유사한 말뚝의 주면마찰력을 예측했다.

• 음성과학
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• 제10권4호
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• pp.181-187
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• 2003

This paper introduces a new zinc coated copper wire electrode with coiled cone shape which has low surface resistance and tolerance to the motion artifact for promontory stimulation electrically auditory brainstem responses (PSEABR). Auditory brainstem responses (ABR) can be used to predict hearing threshold level with a great deal of accuracy particularly for a young child who cannot cooperate mechanically and some hearing impaired who are exaggerating a hearing loss for economic compensation. While severe profound sensorineural hearing losses may not be implemented by auditory potentials, PSEABR is proven as a useful tool even for some sensorineural related hearing impaired. It was shown that PSEABR gives the electrical stimuli to promontory of the cochlear instead of giving acoustic stimuli. For this reason, PSEABR can be used as an alternative for cochlear implantation, and can also be used as an optimal device selection and neural information for MAP. It was found that the role of electrode is very important in PSEABR. Even though this cone-shaped electrode was applied in animal experiments, waveforms are well produced by PSEABR. Thus, it was concluded that cone-shaped electrode turned out to be a useful preoperative audiological evaluation tool in deciding time for cochlear implantation surgery.

• 산업기술연구
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• 제25권B호
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• pp.63-71
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• 2005

This paper is an experimental result of investigating lateral soil movements at piled bridge abutments by using the centrifuge model facility. Three different centrifuge model experiments, changing the methods of ground improvement at bridge abutment on the soft clayey soil (no improvement, preconsolidation and plastic board drains (PBD), sand compaction pile (SCP) + PBD), were carried out to figure out which method is the most appropriate for resisting against the lateral soil movements. In the centrifuge modelling, construction process in field was reconstructed as close as possible. Displacements of abutment model, ground movement, vertical earth pressure, cone resistance after soil improvement and distribution of water content were monitored during and after centrifuge model tests. As results of centrifuge model experiments, preconsolidation method with PBD was found to be the most effective against the lateral soil movement by analyzing results about displacements of abutment model, ground movement and cone resistance. Increase of shear strength by preconsolidation method resulted in increasing the resistance against lateral soil movement effectively although SCP could mobilize the resistance against lateral soil movement. It was also found that installment with PBD beneath the backfill of bridge abutment induced effective drainage of excess pore water pressure during the consolidation by embanking at the back of the abutment and resulted in increasing the shear strength of clay soil foundation and eventually increasing the resistance of lateral soil movement against piles of bridge abutment.