• Geomechanics and Engineering
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• 제11권4호
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• pp.553-570
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• 2016

A series of three-dimensional (3D) parametric finite element analyses have been performed to study the influence of the relative locations of pile tips with regards to the tunnel position on the behaviour of single piles and pile groups to adjacent tunnelling in weathered soil. When the pile tips are inside the influence zone, which considers the relative pile tip location with respect to the tunnel position, tunnelling-induced pile head settlements are larger than those computed from the Greenfield condition. However, when the pile tips are outside the influence zone, a reverse trend is obtained. When the pile tips are inside the influence zone, the tunnelling-induced tensile pile forces mobilised, but when the pile tips are outside the influence zone, compressive pile forces are induced because of tunnelling, depending on the shear stress transfer mechanism at the pile-soil interface. For piles connected to a cap, tensile and compressive forces are mobilised at the top of the centre and side piles, respectively. It has been shown that the increases in the tunnelling-induced pile head settlements have resulted in reductions of the apparent factor of safety up to approximately 43% when the pile tips are inside the influence zone, therefore severely affecting the serviceability of the piles. The pile behaviour, when considering the location of the pile tips with regards to the tunnel, has been analysed in great detail by taking the tunnelling-induced pile head settlements, axial pile forces, apparent factor of safety of the piles and shear transfer mechanism into account.

• Computers and Concrete
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• 제20권3호
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• pp.329-338
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• 2017

A new simple and practical strut-and-tie model (STM) for predicting the shear strength of RC pile caps is proposed in this paper. Two approaches are adopted to take into account the concrete softening effect. In the first approach, a concrete efficiency factor based on compression field theory is employed to determine the effective strength of a concrete strut, assumed to control the shear strength of the whole member. The second adopted Kupfer and Gerstle's biaxial failure criterion of concrete to derive the simple nominal shear strength of pile caps containing the interaction between strut and tie capacity. The validation of these two methods is investigated using 110 RC pile cap test results and other STMs available in the literature. It was found that the failure criterion approach appears to provide more accurate and consistent predictions, and hence is chosen to be the proposed STM. Finally, the predictions of the proposed STM are also compared with those obtained by using seven other STMs from codes of practice and the literature, and were found to give better accuracy and consistency.

• 한국산학기술학회논문지
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• 제11권10호
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• pp.4012-4017
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• 2010

이 연구에서는 팩 말뚝과 모래다짐말뚝의 전단강도 특성을 비교하기 위해 모래-팩-점토 복합토 및 모래-점토 복합토를 인위적으로 치환율($a_s$) 10%, 20%로 재성형하여 구속압력을 변화시켜가며 삼축압축시험(CU Test)을 실시하였다. 시험결과 모래-점토 복합토에 비해 모래-팩-점토 복합토의 강도가 치환율 10% 및 20% 모두에서 훨씬 크게 측정되어 모래다짐말뚝보다 팩말뚝이 큰 지지력을 갖는다는 것을 확인하였다.

• Coupled systems mechanics
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• 제13권3호
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• pp.187-200
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• 2024

This paper presents a numerical model for buckling analysis of slender piles, such as micropiles. The model incorporates geometric nonlinearities to provide enhanced accuracy and a more comprehensive representation of pile buckling behavior. Specifically, the pile is represented using geometrically nonlinear beams with the von Karman deformation measure. The lateral support provided by the surrounding soil is modeled using the spring approach, with the spring stiffness determined according to the undrained shear strength of the soil. The numerical model is tested across a wide range of pile slenderness ratios and undrained shear strengths of the surrounding soil. The numerical results are validated against analytical solutions. Furthermore, the influence of various pile bottom end boundary conditions on the critical buckling force is investigated. The implications of the obtained results are thoroughly discussed.

• 한국지반환경공학회 논문집
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• 제15권2호
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• pp.59-66
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• 2014

본 논문에서는 석션파일의 인발거동을 조사하기 위해 유한차분법 상용 프로그램인 FLAC3D를 이용하여 수치해석을 수행하였다. 석션파일의 인발지지력을 전통적인 지지력 식을 이용하여 구하고, 이 값을 파일의 직경, 길이, 그리고 주변 점토의 비배수 전단강도를 변수로 하는 수치해석을 통한 해석 값과 비교하였다. 총 24개의 수치해석 결과를 바탕으로 석션파일의 인발파괴는 석션파일의 배수조건뿐만 아니라 파일의 제원과 주변 지반의 물성값에 의해 형태가 결정되는 것으로 밝혀졌다. 수치해석 결과로부터 석션파일 내부 주면에 발현되는 전단응력을 구하여 활동파괴와 인장파괴 중 어떤 파괴가 발생할 것인지를 결정하는데 사용하였다. 외부주면의 전단응력과 관계없이 높은 내부 전단응력을 얻은 경우 수치해석 내에서 활동파괴가 발생하는 경우가 많았으며, 이는 전통적인 지지력 공식으로부터 얻은 예측과 잘 맞았다.

• 한국산학기술학회논문지
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• 제11권10호
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• pp.4018-4023
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• 2010

합성구조에서 강재와 콘크리트 사이의 경계면에 효과적인 응력전달과 합성거동을 유도하기 위하여 스터드, 채널, 유공강판 등이 사용된다. 많은 연구자들이 여러 종류의 전단연결재의 특성을 개선시키기 위해 많은 노력을 기울이고 있다. 본 연구에서는 말뚝구조물과 확대기초와의 합성을 위해 개방형 유공강판 전단연결재로 보강된 강관 말뚝머리의 휨거동을 분석하였다. 개방형 유공강판 전단연결재로 보강된 강관말뚝의 휨거동을 규명하고, 다양한 변수해석에서 요구되는 정보를 얻고자 유한요소해석 프로그램인 ABAQUS를 사용하여 비선형 유한요소 해석을 수행하였다.

• Geomechanics and Engineering
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• 제21권2호
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• pp.187-200
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• 2020

In the current work, a series of three-dimensional finite element analyses have been conducted to investigate the behaviour of pre-existing single piles in response to adjacent tunnelling by considering the tunnel face pressures and the relative locations of the pile tips with respect to the tunnel. Via numerical modelling, the effect of the face pressures on the pile behaviour has been analysed. In addition, the analyses have concentrated on the ground settlements, the pile head settlements and the shear stress transfer mechanism at the pile-soil interface. The settlements of the pile directly above the tunnel crown (with a vertical distance between the pile tip and the tunnel crown of 0.25D, where D is the tunnel diameter) with a face pressure of 50% of the in situ horizontal soil stress at the tunnel springline decreased by approximately 38% compared to the corresponding pile settlements with the minimum face pressure, namely, 25% of the in situ horizontal soil stress at the tunnel springline. Furthermore, the smaller the face pressure is, the larger the tunnelling-induced ground movements, the axial pile forces and the interface shear stresses. The ground settlements and the pile settlements were heavily affected by the face pressures and the positions of the pile tip with respect to the tunnel. When the piles were inside the tunnel influence zone, tensile forces were induced on piles, while compressive pile forces were expected to develop for piles that are outside the influence zone and on the boundary. In addition, the computed results have been compared with relevant previous studies that were reported in the literature. The behaviour of the piles that is triggered by adjacent tunnelling has been extensively examined and analysed by considering the several key features in substantial detail.

• Geomechanics and Engineering
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• 제32권5호
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• pp.523-540
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• 2023

The failure of slope can cause remarkable damage to either human life or infrastructures. Stabilizing piles are widely utilized to reinforce slope as a slip-resistance structure. The workability of pile-stabilized slopes is affected by various parameters. In this study, the performance of earth slope reinforced with piles and the behavior of piles under static load, by shear reduction strength method using the finite difference software (FLAC^3D) has been investigated. Parametric studies were conducted to investigate the role of pile length (L), different pile distances from each other (S/D), pile head conditions (free and fixed head condition), the effect of sand density (loose, medium, and high-density soil) on the pile behavior, and the performance of pile-stabilized slopes. The performance of the stabilized slopes was analyzed by evaluating the factor of safety, lateral displacement and bending moment of piles, and critical slip mechanism. The results depict that as L increased and S/D reduced, the performance of slopes stabilized with pile gets better by raising the soil density. The greater the amount of bending moment at the shallow depths of the pile in the fixed pile head indicates the effect of the inertial force due to the structure on the pile performance.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.77-80
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• 2008

본 연구에서는 현행 설계기준상의 강관말뚝머리 연결부의 결합방법이 갖고 있는 철근 배근 및 정착길이 확보, 전단키 용접 등의 문제점을 개선하기 위해 퍼포본드 전단연결재(Perforated Rib Shear Connector)를 활용한 강관말뚝머리 보강방법을 고안하고 이에 대한 압발저항성능을 실험적으로 검증하였다. 그 결과 퍼포본드를 활용한 보강방법은 연직하중에 대해 기존 방법을 대체할만한 동등 수준이상의 구조 안전성은 물론 시공성 및 경제성 측면에서도 우수한 성능을 갖는 구조 시스템인 것으로 나타남에 따라 상부구조의 작용하중을 강관말뚝으로 전달하기 위한 효율적인 강관말뚝머리 연결부 보강방법의 하나로 자리매김할 것으로 사료된다.

• 한국지반공학회논문집
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• 제26권9호
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• pp.5-13
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• 2010

최근 초고층 빌딩과 대형 교량의 사용 증가로 인하여 바렛말뚝에 대한 사용이 증가하고 있지만 바렛말뚝의 주면부 거동특성에 대한 연구는 미비한 실정이다. 이에 본 연구에서는 실물크기 시험말뚝에 대한 현장재하시험을 실시하여 표준관입시험 저항치와 바렛말뚝의 주면히중전이곡선을 산정하는 경험식을 제안하였다. 또한 3차원 유한요소해석을 실시하여 말뚝과 지반과의 경계면 효과를 살펴보았으며 이를 현장자료와 비교하여 평가하였다.