• 한국지반신소재학회논문집
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• 제22권3호
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• pp.97-103
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• 2023

최근 말뚝기초의 수평저항력에 대한 연구들이 활발히 이루어지고 있다. 말뚝기초의 수평저항력에 대한 실험연구들의 경우 변위제어법 또는 하중제어법을 사용하고 있다. 하지만 변위제어법의 경우 말뚝에 가해지는 하중의 속도에 따라 말뚝의 수평저항력이 달라진다. 따라서 본 연구에서는 모형실험을 통해 수평재하속도에 따른 말뚝기초의 수평저항력 변화를 파악하고자 한다. 실험결과 말뚝두부에 가해지낸 수평재하속도가 빠를수록 말뚝의 수평저항력이 감소하는 경향을 보였다. 이를 확인하기 위해 재하속도에 따른 지반과 말뚝의 측면변경 모형실험을 추가적으로 진행하였으며, 그 결과 재하속도가 빠를수록 말뚝의 회전절점의 깊이가 감소하였다. 역해석을 통해 수평재하 속도에 따른 회전절점의 깊이 변화를 파악하였다. 수평재하속도에 따른 말뚝기초의 수평저항력과 회전절점의 깊이 변화를 통해, 말뚝의 수평재하시험시 재하속도는 1.5mm/min 이내로 시험하는 것을 제안하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.185-192
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• 1999

It had found that, as a result of cross-hole tonic logging test, concrete was not filled partially within the bottom 2.0 m of the large diameter (Ø= 2,500mm) rock socketed pile, MP20-P11(socket diameter (Ø= 2,200mm), which was a pile among piles group supporting a pier of Kwangan Grand Bridge. The pile was repaired by the combined cement grout injected through the pipes for the cross-hole sonic logging test and the bore holes for core samples. A month after the cement grouting, repairing was checked by coring and cross-hole sonic logging then 3 times of grouting and 2 times of coring were, in turns, peformed, then repairing was completed successfully. The vertical compressive capacity of the repaired large diameter socketed pile was evaluated by several formulas and software ROCKET, and was more conservative than design load (1,882 ton) of MP20-P11. It is expected that, in the case of the battered socketed piles, it could be more reasonable to analyze the behaviors of a battered pile using 3-D model. A 3-D analysis will be peformed in the future study.

• Geomechanics and Engineering
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• 제38권5호
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• pp.487-495
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• 2024

In this study, a series of shaking table model tests were performed to evaluate the dynamic earth pressure acting on pile foundation during liquefaction. The dynamic earth pressure acting on piles were evaluated with depth and pile diameters comparing with excess pore water pressure, it means that the kinematic load effect plays a substantial role in dynamic pile behavior during liquefaction. The dynamic earth pressure acting on pile foundations with mass exhibited significant similarity to those without upper mass. Analyzing the non-fluctuating and fluctuating components of both excess pore water pressure and dynamic earth pressure revealed that the non-fluctuating component has a dominant influence. In case of non-fluctuating component, dynamic earth pressure is larger than excess porewater pressure at same depth, and the difference increased with depth and pile diameter. However, in the case of the fluctuating component, the earth pressure tended to be smaller than the excess pore water pressure as the depth increased. Based on the results of a series of studies, it can be concluded that the dynamic earth pressure acting on the pile foundation during liquefaction is applied up to 1.5 times the excess pore water pressure for the non-fluctuating component and 0.75 times the excess pore water pressure for the fluctuating component.

• 한국지반공학회지:지반
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• 제11권2호
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• pp.19-28
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• 1995

소형 압력 토조(small pressure chamber)를 이용하여 포화된 사질토에 타입된 폐단 강관 말뚝의 인발거동 특성을 연구하였다. 소형 압력 토조 시험에서는 인발 하중이 인발변위와 함께 증가하다가 급작스러운 미끄러짐 변위가 발생되는 현상이 2-3회 반복되다가 완전 인발파괴에 이르게 되는데, 이때 첫번째 미끄러짐 변위가 발생하는 하중의 크기를 극한 인발 지지력으로 정의할 수 있다. 또한, 소형 압력 토조 시험에서는 미세한 시험 조건에 의해서도 극한 인발 지지력의 크기가 50% 이상의 오차를 나타낼 수도 있으므로 모형 지반을 형성할 때마다 인발 재하 시험에 의하여 극한 인발 지지력을 결정하여 사용하는 것이 좋을 것으로 판단되며, 이때 1차 인발 시험에 의해 교란된 지반의 상태는 모형 말뚝의 크기에 적합한 타격에너지를 가해주어 회복시킬 수 있다.

• 국제초고층학회논문집
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• 제4권4호
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• pp.271-281
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• 2015

This paper introduces detailed three-dimensional numerical analyses on a bored pile foundation for a high-rise building. A static load test was performed on a test pile and a numerical model of a single pile, which was calibrated by comparing it with the test result. The detailed numerical analysis was then conducted on the entire high-rise building foundation. Further study focused on soil pressures under the base slab of a piled raft foundation. Total seven cases with different pile numbers and raft-soil contact conditions were investigated. The design criteria of a foundation, especially settlement requirement were satisfied even for the cases with fewer piles under considerable soil pressure beneath the base slab. The bending moment for the structural design of the base slab was reduced by incorporating soil pressures beneath the base slab along with bored piles. Through the comparative studies, it was found that a more efficient design can be achieved by considering the soil pressure beneath the slab.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 지반공학 공동 학술발표회
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• pp.517-520
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• 2005

The embedded suction anchor(ESA) is and anchor that is driven by a suction pile. The cross-sectional shape of the ESA anchor is circle. Its diameter is the same as that of the suction pile that is used to drive it into the seafloor. For the installation, the anchor is attached to the tip of the suction pile and then driven as a unit with the pile by and applied suction pressure. Once the ESA anchor reaches the desired depth, the pile is retrieved by applying a positive pressure. Finally, only the ESA anchor remains in the soil layer. This paper presents the results of centrifuge model tests to investigate ESA pullout capacity. The main parameters that have effects on the pullout capacity of ESA may include g-level, embedded depth, direction of loading, and loading point. The results of tests show that the pullout loading capacities increase as the loading point shift toward the tip of the anchors for a given loading direction. They also indicate that the loading point associated with the maximum pullout loading capacity is located at approximately 67 percent of the anchor length from the top for the horizontal load.

• 한국지반공학회논문집
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• 제24권8호
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• pp.53-60
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• 2008

본 연구에서는 균질 지반에 매설된 단독말뚝에 수평하중이 작용할 경우 말뚝 배면지반에서 발생되는 여러 가지 거동 특성, 즉 말뚝 배면지반의 변형영역, 파괴면의 경사각, 그리고 회전절점과 같은 거동 특성을 모형실험을 통하여 규명하고자 모형실험을 수행하였다. 이는 말뚝의 휨력에 대한 저항력 산정에 매우 중요한 사항이다. 그 결과 다음과 같은 결과를 얻을 수 있었다. 수평하중이 작용하는 단독말뚝 배면지반에서 쐐기 파괴면은 거의 선형적인 거동 특성을 나타내고, 말뚝과 파괴면이 이루는 경사각은 말뚝 길이, 말뚝 두부의 변위에 상관없이 지반의 상대밀도 증가에 따라 조금씩 증가하다 일정한 값으로 수렴하는 경향을 나타낸다.

• Geomechanics and Engineering
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• 제35권6호
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• pp.603-615
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• 2023

Population growth and urbanization prompted engineers to propose more sophisticated and efficient transportation methods, such as underground transit systems. However, due to limited urban space, it is necessary to construct these tunnels in close proximity to existing infrastructure like high-rise buildings and bridges. Battered piles have been widely used for their higher stiffness and bearing capacity compared to vertical piles, making them effective in resisting lateral loads from winds, soil pressures, and impacts. Considerable prior research has been concerned with understanding the vertical pile response to tunnel excavation. However, the three-dimensional effects of tunnelling on adjacent battered piled foundations are still not investigated. This study investigates the response of a single battered pile to tunnelling at three critical depths along the pile: near the pile shaft (S), next to the pile (T), and below the pile toe (B). An advanced hypoplastic model capable of capturing small strain stiffness is used to simulate clay behaviour. The computed results reveal that settlement and load transfer mechanisms along the battered pile, resulting from tunnelling, depend significantly on the tunnel's location relative the length of the pile. The largest settlement of the battered pile occurs in the case of T. Conversely, the greatest pile head deflection is caused by tunnelling near the pile shaft. The battered pile experiences "dragload" due to negative skin friction mobilization resulting from tunnel excavation in the case of S. The battered pile is susceptible to induced bending moments when tunnelling occurs near the pile shaft S whereas the magnitude of induced bending moment is minimal in the case of B.

• Geomechanics and Engineering
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• 제37권2호
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• pp.97-107
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• 2024

The accurate prediction of grouting upward diffusion height is crucial for estimating the bearing capacity of tip-grouted piles. Borehole construction during the installation of bored piles induces soil unloading, resulting in both radial stress loss in the surrounding soil and an impact on grouting fluid diffusion. In this study, a modified model is developed for predicting grout diffusion height. This model incorporates the classical rheological equation of power-law cement grout and the cavity reverse expansion model to account for different degrees of unloading. A series of single-pile tip grouting and static load tests are conducted with varying initial grouting pressures. The test results demonstrate a significant effect of vertical grout diffusion on improving pile lateral friction resistance and bearing capacity. Increasing the grouting pressure leads to an increase in the vertical height of the grout. A comparison between the predicted values using the proposed model and the actual measured results reveals a model error ranging from -12.3% to 8.0%. Parametric analysis shows that grout diffusion height increases with an increase in the degree of unloading, with a more pronounced effect observed at higher grouting pressures. Two case studies are presented to verify the applicability of the proposed model. Field measurements of grout diffusion height correspond to unloading ratios of 0.68 and 0.71, respectively, as predicted by the model. Neglecting the unloading effect would result in a conservative estimate.

• 한국지반공학회논문집
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• 제19권3호
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• pp.93-104
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• 2003

간단한 제하/재재하 구성방정식을 이용하여 기존의 교란상태개념(DSC)모델을 수정하였고, 그 수정된 DSC모델을 비선형 동역학적 유한요소 프로그램인 DSC_DYN2D에 수치해석적으로 접목(implementation)하였다. 본 연구에서 이용한 구성방정식 DSC 모델은 상대적으로 손상받지 않은 상태(RI)를 정의하기 위하여 HiSS모델을 이용하였고, 완전파괴상태(FA)는 한계상태모델을 이용하였다. 이렇게 수정된 DSC_DYN2D 프로그램을 이용하여 동하중을 받는 현장파일 및 그 주변 지반의 거동을 수치해석적으로 모사 하였다. 해석 결과를 기존의 HiSS모델을 이용한 해석결과와 비교, 분석하였다. 비교결과, DSC모델을 이용하여 해석한 결과가 HiSS모델로 해석한 결과보다 현장계측과 유사하였다. 이를 통해 DSC모델을 이용한 수치해석이 복잡한 점토-파일 접촉면 상호작용 거동을 실제적으로 잘 모사할 수 있다고 판단된다.