• Geomechanics and Engineering
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• 제33권3호
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• pp.231-242
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• 2023

This paper represents a comparative study in which Gene Expression Programming (GEP), Group Method of Data Handling (GMDH), and multiple linear regressions (MLR) were utilized to derive new equations for the prediction of time-dependent bearing capacity of pile foundations driven in cohesive soil, technically called pile set-up. This term means that many piles which are installed in cohesive soil experience a noticeable increase in bearing capacity after a specific time. Results of researches indicate that side resistance encounters more increase than toe resistance. The main reason leading to pile setup in saturated soil has been found to be the dissipation of excess pore water pressure generated in the process of pile installation, while in unsaturated conditions aging is the major justification. In this study, a comprehensive dataset containing information about 169 test piles was obtained from literature reviews used to develop the models. to prepare the data for further developments using intelligent algorithms, Data mining techniques were performed as a fundamental stage of the study. To verify the models, the data were randomly divided into training and testing datasets. The most striking difference between this study and the previous researches is that the dataset used in this study includes different piles driven in soil with varied geotechnical characterization; therefore, the proposed equations are more generalizable. According to the evaluation criteria, GEP was found to be the most effective method to predict set-up among the other approaches developed earlier for the pertinent research.

• 한국지반공학회논문집
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• 제38권4호
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• pp.21-32
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• 2022

강재형 말뚝기초는 안정적인 지지력 확보와 높은 시공성으로 해양구조물 기초로 널리 활용되고 있다. 일반적으로 설계수명에 도달한 해양구조물은 해체수순을 밟게 되는데 말뚝기초는 높은 인발하중과 경제적인 이유로 예외적으로 현장에 존치되는 경우가 많다. 현장에 존치된 기초는 환경오염뿐만 아니라 신규구조물을 건설하는데 장애요인이 될 수 있으므로 말뚝기초 완전해체를 위한 연구가 필요한 실정이다. 본 연구에서는 인발하중을 획기적으로 저감시킬 수 있는 신형식 이중벽 말뚝기초를 제안하고 축소모형실험을 통해 인발하중 저감성능을 실험적으로 평가하였다. 이를 위해 축소된 이중벽 말뚝기초를 제작하고 건조된 모래지반에서 말뚝 설치 및 인발 거동을 모사하였으며, 측정된 인발하중을 동등한 단면의 일반말뚝과 비교하였다. 그 결과, 조밀한 모래지반에서 이중벽 말뚝의 최대 인발력이 일반말뚝에 비해 45% 감소되는 것을 확인하였다. 본 연구를 통해 이중벽 말뚝의 인발하중 저감 성능과 메커니즘을 검증하였으며, 설계수명에 도달한 기초를 완전히 회수할 수 있는 가능성을 확인하였다.

• Computers and Concrete
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• 제32권2호
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• pp.217-232
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• 2023

Numerous studies have been performed on the behavior of pile foundations in cold regions. This study first attempted to employ artificial neural networks (ANN) to predict pile-bearing capacity focusing on pile data recorded primarily on cold regions. As the ANN technique has disadvantages such as finding global minima or slower convergence rates, this study in the second phase deals with the development of an ANN-based predictive model improved with an Elephant herding optimizer (EHO), Dragonfly Algorithm (DA), Genetic Algorithm (GA), and Evolution Strategy (ES) methods for predicting the piles' bearing capacity. The network inputs included the pile geometrical features, pile area (m²), pile length (m), internal friction angle along the pile body and pile tip (Ø°), and effective vertical stress. The MLP model pile's output was the ultimate bearing capacity. A sensitivity analysis was performed to determine the optimum parameters to select the best predictive model. A trial-and-error technique was also used to find the optimum network architecture and the number of hidden nodes. According to the results, there is a good consistency between the pile-bearing DA-MLP-predicted capacities and the measured bearing capacities. Based on the R2 and determination coefficient as 0.90364 and 0.8643 for testing and training datasets, respectively, it is suggested that the DA-MLP model can be effectively implemented with higher reliability, efficiency, and practicability to predict the bearing capacity of piles.

• 국제초고층학회논문집
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• 제4권4호
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• pp.261-270
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• 2015

Hong Kong is a renowned small city with densely placed skyscrapers. It is no surprise that heavy duty or even mega foundations are built over the years to support these structures. To cope with the fast construction pace, several heavy deep foundation types have been widely adopted with some prescribed design rules. This Paper has selected two commonly adopted but distinctive foundation types, namely large diameter bored piles and percussive steel H-piles to illustrate the special design and construction considerations related to these pile types in related to local context. The supervision requirement in related to foundation works for which again may be unique in Hong Kong will also be highlighted. A case history is also discussed in the later part of the Paper to illustrate the application of one of these foundations and to highlight the importance of considering foundation design and basement excavation method in a holistic manner.

• Geomechanics and Engineering
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• 제16권4호
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• pp.449-461
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• 2018

The load sharing ratio (${\alpha}_{pr}$) of piles is one of the most common problems in the preliminary design of piled raft foundations. A series of 3D numerical analysis are conducted so that special attentions are given to load sharing characteristics under varying conditions, such as pile configuration, pile diameter, pile length, raft thickness, and settlement level. Based on the 3D FE analysis, influencing factors on load sharing behavior of piled raft are investigated. As a result, it is shown that the load sharing ratio of piled raft decreases with increasing settlement level. The load sharing ratio is not only highly dependent on the system geometries of the foundation but also on the settlement level. Based on the results of parametric studies, the load sharing ratio is proposed as a function of the various influencing factors. In addition, the parametric analyses suggest that the load sharing ratios to minimize the differential settlement of piled raft are ranging from 15 to 48% for friction pile and from 15 to 54% for end-bearing pile. The recommendations can provide a basis for an optimum design that would be applicable to piled rafts taking into account the load sharing characteristics.

• 한국지진공학회논문집
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• 제21권1호
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• pp.69-76
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• 2017

Seismic analyses of a pile under a large rigid basement foundation embedded in the homogeneous soil layer were performed practically by a response displacement method assuming a sinusoidal wave form. However, it is hard to take into account the characteristics of a large mat foundation and a heterogeneous soil layer with the response displacement method. The response displacement method is relevant to the 2D problems for longitudinal structures such as tunnel, underground cave structure, etc., but might not be relevant with isolated foundations for building structures. In this study, seismic pile analysis by a pseudo 3D finite element method was carried out to compare numerical results with results of the response displacement method considering 3D characteristics of a foundation-soil system which is important for the building foundation analyses. Study results show that seismic analyses results of a response displacement method are similar to those of a pseudo 3D numerical method for stiff and dense soil layers, but they are too conservative for a soft soil layer inducing large soil pressures on the foundation wall and large pile displacements due to ignored foundation rigidity and resistance.

• 한국지반공학회논문집
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• 제24권8호
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• pp.149-160
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• 2008

1990년대 이후로 인천과 부산신항 등의 물류중심항구 및 송도 신도시와 같은 유비쿼터스 도시 개발에 발맞추어 인근해상연약지반 매립공사가 활발히 진행되면서 측방유동 해상말뚝기초의 거동특성에 폭넓은 관심이 집중되고 있다. 측방유동 말뚝기초 거동에 대한 연구 및 규명은 원심모형기 개발과 컴퓨터 기능의 향상으로 인하여 폭넓은 시도가 이루어져 왔으며, 특히 말뚝구조물에 작용하는 측방유동압의 특성이 가장 중요한 초점이 되고 있다. 이에 본 연구에서는 대변형 압밀연계 유한요소해석 기법(LDFE)을 바탕으로 배수조건(비배수 : 단기, 배수 : 장기)에 따른 측방유동 해상 말뚝기초의 거동특성을 분석하였으며 특히, 말뚝-지반 상호작용을 고려한 측방유동압에 중점을 두었다. 본 수치해석에서는 지층조건, 말뚝두부의 경계조건, 성토하중 크기, 평균압밀도 네 가지 중요변수에 따른 거동양상을 비교 분석하였으며, 이로부터 비배수 단계와 배수 단계에서의 측방유동압의 분포형태와 크기에 대한 정량적인 차이를 확인하였다.

• 국제초고층학회논문집
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• 제4권4호
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• pp.227-239
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• 2015

This paper discusses the design parameters that are required for the design of high-rise building foundations, and suggests that the method of assessment for these parameters should be consistent with the level of complexity involved for various stages in the design process. Requirements for effective ground investigation are discussed, together with relevant in-situ and laboratory test techniques for deriving the necessary strength and stiffness parameters. Some empirical correlations are also presented to assist in the early stages of design, and to act as a check for parameters that are deduced from more detailed testing. Pile load testing is then discussed and a method of interpreting bi-directional tests to obtain pile design parameters is outlined. Examples of the application of the assessment process are described, including high-rise projects in Dubai and Saudi Arabia.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.559-568
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• 2010

Recently, because of mega foundations and grand bridges, the foundations require significant bearing capacity. In this study, bearing capacity of high strength steel pipe pile with an extended head (HSP) is calculated on the basis of domestic criteria and Japanese criteria. And bearing capacity of HSP is investigated based on 3 field tests. In comparison with the results of analysis and tests, it is shown that the field test results are bigger than analysis results. Therefore, it is proposed to estimate bearing capacity of HSP.

• 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.