• 제목/요약/키워드: piled raft

검색결과 96건 처리시간 0.023초

Analysis of load sharing characteristics for a piled raft foundation

  • Ko, Junyoung;Cho, Jaeyeon;Jeong, Sangseom
    • 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.

Effect of groundwater level change on piled raft foundation in Ho Chi Minh City, Viet Nam using 3D-FEM

  • Kamol Amornfa;Ha T. Quang;Tran V. Tuan
    • Geomechanics and Engineering
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    • 제32권4호
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    • pp.387-396
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    • 2023
  • Ground subsidence, which is a current concern that affects piled raft foundations, has occurred at a high rate in Ho Chi Minh City, Viet Nam, due primarily to groundwater pumping for water supply. In this study, the groundwater level (GWL) change affect on a piled raft foundation was investigated based on the three-dimensional finite element method (3D-FEM) using the PLAXIS 3D software. The GWL change due to global groundwater pumping and dewatering were simulated in PLAXIS 3D based on the GWL reduction and consolidation. Settlement and the pile axial force of the piled raft foundation in Ho Chi Minh subsoil were investigated based on the actual design and the proposed optimal case. The actual design used the piled foundation concept, while the optimal case applied a pile spacing of 6D using a piled raft concept to reduce the number of piles, with little increased settlement. The results indicated that the settlement increased with the GWL reduction, caused by groundwater pumping and dewatering. The subsidence started to affect the piled raft foundation 2.5 years after construction for the actual design and after 3.4 years for the optimal case due to global groundwater pumping. The pile's axial force, which was affected by negative skin friction, increased during that time.

느슨한 모래지반에서의 말뚝지지 전면기초에 대한 실험적 연구 (An Experimental Study of Piled Raft Footing on Loose Sands)

  • 권오균;이활;이승현;오세붕;장학성
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2003년도 봄 학술발표회 논문집
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    • pp.439-446
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    • 2003
  • In this paper the model tests have been conducted and the results are compared with those by the theoretical methods to study the behaviors of the piled raft. The size of model box is 2.2m${\times}$2m${\times}$2m. The raft is made of rigid steel plate and piles made of steel pipes. Generally the bearing capacity of group piles is designed with only the pile capacities, and the bearing capacity of raft is ignored. But the uncertainty of pile-raft-soil interaction leads to conservative design ignoring the bearing effects of raft. In the case of considering the bearing capacity of raft, the simple sum of bearing capacity of raft and that of each pile cannot be the bearing capacity of piled raft. Because the pile-raft-soil interaction affects the behavior of piled raft. Thus the effects of pile-raft-soil interaction are very important in the optimal design. In this paper, the behaviors of piled raft are studied through model tests of 2${\times}$2, 2${\times}$3, and 3${\times}$3 pile groups. The spacing between piles is changed in the model tests. And the behaviors of free standing and piled raft are also studied.

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원심모형실험을 통한 사질토 지반에서의 말뚝지지 전면기초 상호작용 분석 (Analysis of Piled Raft Interactions in Sand with Centrifuge Test)

  • 박동규;최규진;이준환
    • 한국지반공학회논문집
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    • 제28권10호
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    • pp.27-40
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    • 2012
  • 말뚝지지 전면기초는 무리말뚝과 전면기초의 지지력을 함께 설계에 적용할 수 있는 기초형식이다. 그러나 변위장 중첩과 구속응력의 증가 등으로 대변되는 무리말뚝 - 지반 - 전면기초 상호작용으로 인해 각각의 무리말뚝기초와 전면기초의 지지력 특성은 변화하게 되며, 이는 말뚝지지 전면기초의 설계에 있어 중요한 요소로써 작용한다. 본 연구에서는 말뚝지지 전면기초에서 발생하는 지지력요소들의 상호작용을 규명하기 위해 원심모형시험을 이용한 전면기초, 단독 말뚝기초, 무리말뚝(16본; $4{\times}4$), 말뚝지지 전면기초(16본; $4{\times}4$) 하중-재하 시험을 수행하였으며, 조밀하고 느슨한 사질토 지반에서의 무리말뚝-지반, 무리말뚝-지반-전면기초의 상호작용을 하중단계에 따른 지지력 특성변화를 기준으로 분석하였다. 실험결과 말뚝지지 전면기초의 상호작용에 의해 무리말뚝기초의 지지력은 증가하는 것으로 나타났으며, 전면기초의 경우 무리말뚝의 영향에 의해 지지력이 감소하는 것으로 확인되었다.

Simplified Analysis of Three Dimensional Mega Foundations for High-Rise Buildings

  • Jeong, Sangseom;Lee, Jaehwan;Cho, Jaeyeon
    • 국제초고층학회논문집
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    • 제4권4호
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    • pp.241-247
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    • 2015
  • In this study, an approximate computer-based method was developed to analyze the behavior of raft and piled raft foundations. Special attention is given to the improved analytical method proposed by considering raft flexibility and soil nonlinearity. The overall objective of this study is to focus on the application of a simplified analysis method for predicting the behavior of sub-structures. Through the comparative studies, it is found that the computer programs (YS-MAT and YSPR), developed in this study, is in agreement with the general trends observed by field measurements. Therefore, YS-MAT (Yonsei-Mat) and YSPR (Yonsei Piled Raft) can be effectively used for the preliminary design of a raft or a piled raft foundation for high-rise buildings.

유전자 알고리즘을 이용한 Piled Raft 기초의 최적설계 (Optimum Design of Piled Raft Foundations using Genetic Algorithm)

  • 김홍택;강인규;황정순;전응진;고용일
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 1999년도 가을 학술발표회 논문집
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    • pp.415-422
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    • 1999
  • This paper describes a new optimum design approach for piled raft foundations using the genetic algorithm. The objective function considered is the cost-based total weight of raft and piles. The genetic algorithm is a search or optimization technique based on nature selection. Successive generation evolves more fit individuals on the basis of the Darwinism survival of the fittest. In formulating the genetic algorithm-based optimum design procedure, the analysis of piled raft foundations is peformed based on the 'hybrid'approach developed by Clancy(1993), and also the simple genetic algorithm proposed by the Goldberg(1989) is used. To evaluate a validity of the optimum design procedure proposed based on the genetic algorithm, comparisons regarding optimal pile placement for minimizing differential settlements by Kim et at.(1999) are made. In addition using proposed design procedure, design examples are presented.

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샌드쿠션을 고려한 말뚝지지 전면기초의 수치해석 (Numerical Analysis of Piled-Raft Foundations Considering the Effects of Sand Cushion)

  • 김남익;서영교
    • 한국해양공학회지
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    • 제21권5호
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    • pp.25-32
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    • 2007
  • The piled-raft foundation, a new design concept, is one of the most effective kinds of foundation for reducing settlement of structures. An alternative piled-raft system with disconnection cap and a sand cushion between the pile and raft was also investigated to compare the influence of ultimate bearing capacity and settlement. Load-settlement relation curves were used to evaluate the ultimate bearing capacity. In the numerical analyses, a plane strain elasto-plastic finite element model (Mohr-Coulomb model) was used to present the response of the piled-raft foundation.

말뚝지지 전면기초 (Piled Raft Foundations)

  • 권오균;이활
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2002년도 기초기술위원회 워크샵
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    • pp.102-117
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    • 2002
  • The general design practice for piled footings is based on the assumption that the piles are free-standing, and that all the external loads are carried by the piles, with any contribution of the footing being ignored. This approach is not reasonable, because the footing itself is actually in direct contact with the soil, and thus carries a significant fraction of the loads. In the case of not considering the bearing capacity of footing, the bearing capacity of group piles can be evaluated conservatively in the designing the group piles. There are a number of reasons why the idea of piled raft design with considering the capacity of footing has not become widely used. One of the reasons is the lack of reliable calculation methods for estimating the behavior of piled raft. In this study the bearing capacity, settlement, load distribution, etc. of piled raft footing are studied.

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연약지반에서 경량구조물 기초의 침하거동에 관한 연구 (A Study on The Settlement Behavior of Foundations for Light-weight Structures on Clay Deposits)

  • 이광열;정진교;윤성태
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2007년 가을학술발표회
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    • pp.692-700
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    • 2007
  • There are several types of foundations for light-weight structures, such as low story buildings, on soft clay deposits. Those foundations, such as piled raft, compensated foundation, mat foundation, floating foundation are commonly used rather then end-bearing piles to get more benefits on the construction and cost savings. In this study, settlement behaviors are computed and compared for several types of foundations on soft clay deposits. Also, theoretical expressions of parameters for piled raft system were provided with co-relations for design purposes. The predictions of settlements of piled rafts foundation are proposed based on the pile dimensions and design loads. From this study, the piled raft foundations is more benefits for reducing the settlement of clay deposits, and it is found that the piled raft system is applicable and effective on thick clay deposits, and that differential settlements of the foundation should be managed by designing the configuration of pile lengths.

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