• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1994년도 가을 학술발표회 논문집
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• pp.87-93
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• 1994

Factors which affect the capacity and the soil plug condition of an open-ended pile can be broadly divided into three categories:i.e., pile conditions, soil conditions and penetration methods. It has been found that the relative density and the horizontal stress have much effects on the soil plug behavior than other soil conditions. Also, it has been found that the pile diameter is the most important factor among pile conditions. However, a few investigations have been performed to account for both soil conditions and pile conditions. In this paper, a number of calibration chamber tests have been conducted with three different sized open-ended model piles. The model pile was driven into siliceous sand, with varying soil conditions, to clarify coupled effects of pile diameter and soil conditions on the plug behavior, the capacity, and the load trasfer mechanixm of soil plug. The model piles are composed of two stainless steel pipes so as to measure the plug capacity, the tip resistance, and the outside skin friction. separately.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.81-88
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• 1998

During an earthquake, there are three main components of excitation : horizontal excitation of the ground, vertical excitation of the pile due to superstructure feedback produced by vertical excitation of the ground, and the seawater excitation induced by the vertical ground shaking, that is, "the seaquake." These excitations could have effects on the soil plugs in open-ended pipe piles installed at offshore sites. In this study, seaquake excitation induced by the vertical ground shaking was simulated by pulsing the water pressure at the seabed. During a seaquake, due to induced excess porewater pressure and pressure gradients in the soil, the capacity of open-ended pipe piles installed in a simulated sea depth of greater than 220 m was reduced serevely and the soil plugging resistance was degraded by more than 80%. The soil plug was failed because of the upward seepage forces that developed in the soil plug due to excess pore water pressure produced in the bottom of the soil plug during the seaquake. The compressive capacity of an open-ended pile in a simulated sea depth of less than 220m was reduced only by about 10%, and the soil plug resistance was degraded by less than 5%.s than 5%.

• 한국지반공학회지:지반
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• 제9권4호
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• pp.7-16
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• 1993

지반조건이 관내토의 지지력특성에 미치는 영향을 알아보기 위하여 여러가지 조건을 갖는 모래지반에 타입된 개단말뚝에 대하여 토조실험을 수행하였다. 실험에서 사용된 모형말뚝은 말뚝의 지지력을 외주면마찰력과 관내토지지력, 그리고 말뚝 단면부지지력의 세가지로 분리 측정할 수 있도록 제작하였다. 몇가지 가정하에 실험결과로부터 계산된 관내토 내부의 토압계수는 말뚝의 관입깊이와 지반의 상대밀도가 증가함에 따라 감소하고, 지반의 초기 압밀압력이 증가할수록 증가하는 경향을 나타낸다. 또한 토압계수는 관내토의 하단부에 접근할수록 증가한다. 관내토의 1차원 해석으로부터 계산된 관내토지지력과 실측치의 비교로부터 Randolph등과 O'Neill등에 의하여 제안된 P를 이용한 1차원 해석이나 API의 추천방법은 관내토지지력을 상당히 과소평가 함을 알 수 있다. 따라서 실험결과에 근거하여 관내토의 1차원 해석을 통한 관내토지지력의 예측 정도를 높이기 위하여 1차원 해석에 필요한 관내토의 토압계수를 산정할 수 있는 경험식이 제안되었으며, 제안된 식은 모든 지반조건에 대하여 적당한 관내토지지력을 산정한다.

• 한국지반공학회논문집
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• 제40권4호
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• pp.145-154
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• 2024

본 연구에서는 개단말뚝의 항타 과정을 이산요소해석법(DEM)으로 모델링하여 관내토의 거동을 분석하였다. DEM 모델 검증을 위해 모형말뚝시험과 수치해석 결과를 비교하였으며, 입자 간 회전 저항력을 고려한 접촉모델을 적용하여 흙 입자 간 상호작용을 검증하였다. 2차원 원형 입상재료의 상대밀도와 말뚝의 관입 속도를 조절하여 관내토의 압축 거동을 성공적으로 모사하였으며, 초기 관입 속도가 감소할수록 관내토가 더 압축되는 경향을 확인하였다. DEM 모델을 통해 관내토 길이와 관내토 길이 지표인 Plug Length Ratio(PLR), Incremental Filling Ratio(IFR)를 분석하였으며, 이를 모형시험 결과와 비교하여 개단말뚝의 관내토 거동을 검증하였다. 본 연구는 관내토의 폐색상태를 직접 반영하여 개단말뚝의 거동을 분석할 수 있는 이산요소해석법을 활용한 모델을 개발하였으며, 그 모델링 과정와 검증 방법을 상세히 소개하여 향후 연구의 시행착오를 줄이는 데 기여할 것으로 판단된다.

• Geomechanics and Engineering
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• 제15권1호
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• pp.695-710
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• 2018

Formation of a soil plug in an open-ended pile is a very important factor in determining the pile behavior both during driving and during static loading. The degree of soil plugging can be represented by the incremental filling ratio (IFR) which is defined as the change in the plug length to the change of the pile embedment length. The experimental tests carried out in this research contain 138 tests that are divided as follows: 36 tests for single pile, 36 tests for pile group ($2{\times}1$), 36 tests for pile group ($2{\times}2$) and 30 pile group ($2{\times}3$). All tubular piles were tested using the poorly graded sand from the city of Karbala in Iraq. The sand was prepared at three different densities using a raining technique. Different parameters are considered such as method of installation, relative density, removal of soil plug with respect to length of plug and pile length to diameter ratio. The soil plug is removed using a new device which is manufactured to remove the soil column inside open pipe piles group installed using driving and pressing device. The principle of soil plug removal depends on suction of sand inside the pile. It was concluded that the incremental filling ratio (IFR) is changed with the changing of soil state and method of installation. For driven pipe pile group, the average IFR for piles in loose is 18% and 19.5% for L/D=12 and 15, respectively, while the average of IFR for driven piles in dense sand is 30% and 20% for L/D=12 and L/D=15 respectively. For pressed method of pile installation, the average IFR for group is zero for loose and medium sand and about 5% for dense sand. The group capacity increases with the increase of IFR. For driven pile with length of 450 mm, the average IFR % is about 30.3% in dense sand, 14% in medium and 18.3% for loose sand while when the length of pile is 300 mm, the percentage equals to 20%, 17% and 19.5%, respectively.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1996년도 가을 학술발표회 논문집
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• pp.303-310
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• 1996

• Geomechanics and Engineering
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• 제11권3호
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• pp.385-400
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• 2016

Bearing capacity of open-ended piles depends largely on inner frictional resistance, which is influenced by the degree of soil plugging. While a fully-plugged open-ended pile produces a bearing capacity similar to a closed-ended pile, fully coring (or unplugged) pile produces a much smaller bearing capacity. In general, open-ended piles are driven under partially-plugged mode. The formation of soil plug may depend on many factors, including wall thickness at the pile tip (or inner pile diameter), sleeve height of the thickened wall at the pile tip and relative density. In this paper, we studied the effects of wall thickness at the pile base and sleeve height of the thickened wall at the pile tip on bearing capacity using laboratory model tests. The tests were conducted on a medium dense sandy ground. The model piles with different tip thicknesses and sleeve heights of thickened wall at the pile tip were tested. The results were also discussed using the incremental filling ratio and plug length ratio, which are generally used to describe the degree of soil plugging. The results showed that the bearing capacity increases with tip thickness. The bearing capacity of piles of smaller sleeve length (e.g., ${\leq}1D$; D is pile outer diameter) was found to be dependent on the sleeve length, while it is independent on the sleeve length of greater than a 1D length. We also found that the soil plug height is dependent on wall thickness at the pile base. The results on the incremental filling ratio revealed that the thinner walled piles produce higher degree of soil plugging at greater penetration depths. The results also revealed that the soil plug height is dependent on sleeve length of up to 2D length and independent beyond a 2D length. The piles of a smaller sleeve length (e.g., ${\leq}1D$) produce higher degree of soil plugging at shallow penetration depths while the piles of a larger sleeve length (e.g., ${\geq}2D$) produce higher degree of soil plugging at greater penetration depths.

• Journal of Forest and Environmental Science
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• 제36권1호
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• pp.55-61
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• 2020

In this study, basic data with respect to the introduction of Hipphophae rhamnoides L. and its cultivation in Korea could be obtained. According to the size of the plug cell tray, Chinese origin's rate of seed germination was relatively high in 128 plug cell tray, and growth was vibrant in 50 plug cell tray. The germination and growth of Russian origin seeds showed that they were relatively effective in 50 plug cell tray and with respect to soil environment, TKS-2 soil with untreated shading relatively promoted both germination and growth for Chinese origin, the rate of germination was high in bed soil for horticulture and growth result was good in TKS-2 in the case of Russian origin. It was confirmed that the germination rate of Chinese origin H. rahmnoides L. was highest in untreated shading and the shoot growth was vibrant in 70% shading while the growth in roots was vibrant in the untreated shading. In the Russian origin, H. rhamnoides L. the germination rate in 30% and 70% shading was about 50% which was higher than that in the untreated shading and general growth was vibrant in 30% shading.

• Journal of Biosystems Engineering
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• 제29권3호
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• pp.251-260
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• 2004

As a basic experiment for robot hand for transplanting plug seedling, the experimental robot hand system which moves up and downward vertically, and allows hand blade to open and close was made. The system was constructed with the robot hand mechanism, the tray, the plug seedling, and the measuring equipments. The penetrating force and holding efficiency were analyzed according to the soil moisture and the variation of hand blade angle. The highest holding efficiency could be obtained at the penetrating angle of approximately from 0 to 0.36 degree and at the moisture content of soil from 71% to 75%. The external force acted on the robot hand should maximum force when the robot hand was penetrated to soil, minimum of approximately 30.4 N when the penetrating angle was 0$^{\circ}$ and moisture content was 66-70%. It was increased with increasing or decreasing the Penetrating angle from 0 degree and also with increasing or decreasing the moisture content of soil from 66-70%. For optimal design of the robot hand and manipulator, the external force acted on robot hand had to be based on the returning force of soil, when the robot hand was penetrated to the soil. In consideration of safety ratio, the appropriate external force seemed to be 39-49 N.

• Geomechanics and Engineering
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• 제31권2호
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• pp.209-222
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• 2022

Finite element analyses using coupled Eulerian-Lagrangian technique are performed to investigate the effect of soil conditions on plugging of open-ended piles in sands. Results from numerical simulations are compared against the data from field load tests on three open-ended piles and show very good agreement. A parametric study focusing on determination of the coefficient of lateral earth pressure (K) in soil plug after pile driving are then performed for various soil densities, end-bearing conditions, and layering conditions. Results from the parametric study suggest that the K value in the soil plug - and hence the degree of soil plugging - increases with increasing soil densities. The analysis results further show that the K value within the soil plug can reach about 63 to 71% of the coefficient of passive earth pressure after pile driving. For layered soil profiles, the greater K values are achieved after pile driving when the denser soil layer is present near the pile base regardless of number of soil layers. This study provides comprehensive numerical and experimental data that can be used to develop advanced theory for analysis and design of open-ended pipe piles, especially for estimation of inner shaft resistance after pile driving.