• 한국지반공학회논문집
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• 제16권4호
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• pp.171-181
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• 2000

성토지지말뚝 상부의 성토지반내에서 발생되는 지반아칭효과에 의하여 성토하중이 말뚝에 전달되는 효과를 조사하면서 제안된 이론해석의 신뢰성을 확인하기 위하여 일련의 모형실험을 수행하였다. 본 모형실험에서 말뚝은 성토 아래에 일렬로 수열의 줄말뚝으로 설치하였으며, 말뚝캡보는 성토의 길이방향에 직각방향으로 말뚝두부에 설치하였다. 성토재의 하중전달에 가장 큰 영향을 미치는 요인으로는 말뚝캡보사이의 간격과 성토고를 들 수 있다. 이전의 이론적인 연구에 의해 제안된 지반아치의 반경보다 약 33%정도 큰 최소소요성토고보다 높게 성토를 실시할 경우 지반아치는 완벽하게 발생될 뿐만 아니라, 실험치와 이론치는 잘 일치함을 모형실험결과 확인할 수 있다. 모형말뚝캡보에 작용하는 성토하중의 분담률은 말뚝캡보사이의 간격이 증가함에 따라 감소하는 반면, 성토고가 높아짐에 따라 증가하였다. 따라서, 설계시 말뚝의 성토하중지지효과를 극대화시키기 위해서는 성토고를 충분히 높게한 상태에서 말뚝캡보의 간격비를 감소시켜야 한다. 여기서 말뚝캡보의 간격비를 감소시키려면 말뚝캡보사이의 간격을 감소시키거나 말뚝캡보의 폭을 증가시켜야 한다.

• Earthquakes and Structures
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• 제20권1호
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• pp.87-96
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• 2021

Ground motions recorded in near-fault sites, where the rupture propagates toward the site, are significantly different from those observed in far-fault regions. In this research, finite element modeling is used to investigate the effect of pile cap stiffness on the seismic response of soil-pile-structure systems under near-fault ground motions. The Von Wolffersdorff hypoplastic model with the intergranular strain concept is applied for modeling of granular soil (sand) and the behavior of structure is considered to be non-linear. Eight fault-normal near-field ground motion records, recorded on rock, are applied to the model. The numerical method developed is verified by comparing the results with an experimental test (shaking table test) for a soil-pile-structure system. The results, obtained from finite element modeling under near-fault ground motions, show that when the value of cap stiffness increases, the drift ratio of the structure decreases, whereas the pile relative displacement increases. Also, the residual deformations in the piles are due to the non-linear behavior of soil around the piles.

• 한국지반환경공학회 논문집
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• 제20권10호
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• pp.39-46
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• 2019

상부구조물을 지지하는 무리말뚝의 내진설계 시 지반-구조물의 상호작용이 고려되어야 한다. 무리말뚝 설계 시 지반과 구조물의 비선형 관계는 p-y 곡선이 많이 사용되고 있으며 지진과 같은 동적하중조건에서 지반-구조물의 상호작용이 고려된 동적 p-y 곡선을 무리말뚝의 내진설계에 사용하기 위한 연구가 진행되고 있다. 그러나 이와 같은 연구는 말뚝 캡에 의한 지지효과 및 상부구조물의 관성거동에 의한 상호작용은 고려되지 않았다. 이에 본 연구에서는 사질토 지반에 근입된 상부구조물을 지지하는 무리말뚝에서 말뚝 캡의 변화가 무리말뚝에 미치는 영향을 확인하기 위해 말뚝의 배열 및 중심 간격은 고정하고 말뚝 캡 측면과 말뚝 중심 간격을 변화시켜 진동대 모형실험을 수행하였다. 그 결과 무리말뚝에서 말뚝 캡 측면과 말뚝 중심 간격의 변화가 말뚝의 동적 p-y 곡선 및 무리말뚝 효과에 영향을 미치는 것으로 나타났다.

• Geomechanics and Engineering
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• 제33권5호
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• pp.463-475
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• 2023

Tunnel construction activity, conducted mainly in mountains and within urban centres, causes soil settlement, thus requiring the relevant management of slopes and structures as well as evaluations of risk and stability. Accordingly, in this study we performed a three-dimensional finite element analysis to examine the behaviour of piles and pile cap stability when a tunnel passes near the bottom of the foundation of a pile group connected by a pile cap. We examined the results via numerical analysis considering different conditions for reinforcement of the ground between the tunnel and the pile foundation. The numerical analysis assessed the angular distortion of the pile cap, pile settlement, axial force, shear stress, relative displacement, and volume loss due to tunnel excavation, and pile cap stability was evaluated based on Son and Cording's evaluation criterion for damage to adjacent structures. The pile located closest to the tunnel under the condition of no ground reinforcement exhibited pile head settlement approximately 70% greater than that of the pile located farthest from the tunnel under the condition of greatest ground reinforcement. Additionally, pile head settlement was greatest when the largest volume loss occurred, being approximately 18% greater than pile head settlement under the condition having the smallest volume loss. This paper closely examines the main factors influencing the behaviour of a pile group connected by a pile cap for three ground reinforcement conditions and presents an evaluation of pile cap stability.

• Geomechanics and Engineering
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• 제10권5호
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• pp.577-598
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• 2016

This paper presents a numerical study of pile force distribution in a pile group foundation subjected to vertical load and large moment. The physical modeling of a pile foundation for a wind turbine is analyzed using 3D finite element software, PLAXIS 3D. The soil profile consists of several clay layers, which are modeled as Mohr-Coulomb material in an undrained condition. The piles in the pile group foundation are modeled as special elements called embedded pile elements. To model the problem of a pile group foundation, a small gap is created between the pile cap and underlying soil. The pile cap is modeled as a rigid plate element connected to each pile by a hinge. As a result, applied vertical load and large moment are transferred only to piles without any load sharing to underlying soil. Results of the study focus on pile load distribution for the square shape of a pile group foundation. Mathematical expression is proposed to describe pile force distribution for the cases of vertical load and large moment and purely vertical load.

• 한국지반환경공학회 논문집
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• 제20권8호
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• pp.5-12
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• 2019

상부구조물은 여러 개의 말뚝 기초를 말뚝 캡으로 연결한 무리말뚝이 사용되고 있다. 무리말뚝 설계 시 상부구조물의 연직 및 수평하중은 말뚝 기초가 지지할 뿐 말뚝 캡의 지지효과는 무시하였다. 그러나 최근 상부구조물의 연직하중에 대한 안정성 범위에서 말뚝 기초의 사용량을 줄이기 위해 말뚝 캡의 지지효과를 반영하기 위한 연구가 진행되고 있으나 수평하중에 대한 말뚝 캡의 지지효과에 관한 연구는 미비한 실정이다. 이에 본 연구에서는 수평 지진 하중을 받는 무리말뚝에서 말뚝 캡의 변화가 무리말뚝에 미치는 영향을 확인하기 위해 상부구조물을 지지하는 무리말뚝의 말뚝 캡 크기를 변화시켜 진동대 모형실험을 수행하였다. 그 결과 말뚝 캡의 크기가 상부구조물 및 무리말뚝의 동적 거동에 영향을 미치는 것으로 확인되었으며, 말뚝 캡의 크기가 증가할수록 지반 구속 효과로 인해 지반과 말뚝 기초가 일체 거동하는 것으로 나타났다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.369-378
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• 2010

In this study, a computer program to predict the behavior of laterally loaded single pile and pile groups was developed by using a beam-column analysis in which the soils are modeled as nonlinear springs by a family of p-y curves for subgrade modulus. The special attention was given to the lateral displacement of a single pile and pile groups due to the soil condition and the cap rigidity. The analysis considering group effect was carried out for $2{\times}2$ and $3{\times}3$ pile groups with the pile spacing 3.0B, 4.0B and 5.0B. Based on the results obtained, it is found that the overall distributions of deflection, slope, moment, and shear force in a single pile give a reasonable results irrespective of cap connectivity conditions. It is also found that even though there are some deviations in deflection prediction compared with the observed ones, the prediction by present analysis simulates much better the general trend observed by the centrifuge tests than the numerical solution predicted by PIGLET.

• Advances in concrete construction
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• 제10권1호
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• pp.49-59
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• 2020

Precast concrete elements in accelerated bridge construction (ABC) extends from superstructure to substructure, precast pile foundation has proven a benefit for regions with fragile ecological environment and adverse geological condition. There is still a lack of knowledge of the seismic behavior and performance of the precast pile foundation. In this study, a 1/8 scaled model of precast pile foundation with elevated cap is fabricated for quasi-static test. The failure mechanism and responses of the precast pile-soil interaction system are analyzed. It is shown that damage occurs primarily in precast pile-soil interaction system and the bridge pier keeps elastic state because of its relatively large cross-section designed for railways. The vulnerable part of the precast pile with elevated cap is located at the embedded section, but no plastic hinge forms along the pile depth under cyclic loading. Hysteretic curves show no significant strength degradation but obvious stiffness degradation throughout the loading process. The energy dissipation capacity of the precast pile-soil interaction system is discussed by using index of the equivalent viscous damping ratio. It can be found that the energy dissipation capacity decreases with the increase of loading displacement due to the unyielding pile reinforcements and potential pile uplift. It is expected to promote the use of precast pile foundation in accelerated bridge construction (ABC) of railways designed in seismic regions.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.831-837
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• 2005

In this study, a computer program to predict the behavior of laterally loaded single pile and pile groups was developed by using a beam-column analysis in which the soils are modeled as nonlinear springs by a family of p-y curves for subgrade modulus. The special attention was given to the lateral displacement of a single pile and pile groups due to the soil condition and the cap rigidity. The analysis considering group effect was carried out for $2\;{\times}\;2\;and\;3\;{\times}\;3$ pile groups with the pile spacing 3.0B, 4.0B and 5.0B. Based on the results obtained, it is found that the overall distributions of deflection, slope, moment, and shear force in a single pile give a reasonable results irrespective of cap connectivity conditions. It is also found that even though there are some deviations in deflection prediction compared with the observed ones, the prediction by present analysis simulates much better the general trend observed by the centrifuge tests than the numerical solution predicted by PIGLET.

• Interaction and multiscale mechanics
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• 제3권1호
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• pp.55-79
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• 2010

The effect of soil-structure interaction on a single-storey, two-bay space frame resting on a pile group embedded in the cohesive soil (clay) with flexible cap is examined in this paper. For this purpose, a more rational approach is resorted to using the finite element analysis with realistic assumptions. Initially, a 3-D FEA is carried out independently for the frame on the premise of fixed column bases in which members of the superstructure are discretized using the 20-node isoparametric continuum elements. Later, a model is worked out separately for the pile foundation, by using the beam elements, plate elements and spring elements to model the pile, pile cap and soil, respectively. The stiffness obtained for the foundation is used in the interaction analysis of the frame to quantify the effect of soil-structure interaction on the response of the superstructure. In the parametric study using the substructure approach (uncoupled analysis), the effects of pile spacing, pile configuration, and pile diameter of the pile group on the response of superstructure are evaluated. The responses of the superstructure considered include the displacement at top of the frame and moments in the columns. The effect of soil-structure interaction is found to be quite significant for the type of foundation considered in the study. Fair agreement is observed between the results obtained herein using the simplified models for the pile foundation and those existing in the literature based on a complete three dimensional analysis of the building frame - pile foundation - soil system.