• Title/Summary/Keyword: Design of pile group

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New Design Method for Pile Group under Vertical Load (연직하중을 받는 무리말뚝의 새로운 설계 방법)

  • 이수형;정충기
    • Proceedings of the Korean Geotechical Society Conference
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    • 2002.06a
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    • pp.11-29
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    • 2002
  • Current design of pile group is based on the estimation of the overall bearing capacity of a pile group from that of a single pile using a group efficiency. However, the behaviors of a pile group are influenced by various factors such as method of pile installation, pile-soil-pile interaction, cap-soil-pile interaction, etc. Thus it is practically impossible to take into account these factors reasonably with the only group efficiency, In this paper, a new method for the design of pile groups is proposed, where the significant factors affecting the behavior of a pile group are considered separately by adopting several efficiencies. Furthermore, in the proposed method, the load transfer characteristics of piles and the difference of pile behaviors with respect to the pile locations in group can be taken into account. The efficiencies for the method are determined using the settlement failure criterion, which is consistent with the concept of allowable settlement for structures. The efficiencies calculated from the results of existing model tests are presented, and the bearing capacity of a pile group in the other model test is calculated and compared with that from the test result, to verify the validity of the proposed method.

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New Design Method for Pile Group Under Vertical Load (연직하중을 받는 무리말뚝의 새로운 설계 방법)

  • 이수형;정충기
    • Journal of the Korean Geotechnical Society
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    • v.19 no.1
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    • pp.31-40
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    • 2003
  • Current design of pile group is based on the estimation of the overall bearing capacity of a pile group from that of a single pile using a group efficiency. However, the behaviors of a pile group are influenced by various factors such as the method of pile installation, pile-soil-pile interaction, cap-soil-pile interaction, etc. Thus, it is practically impossible to take into account these factors reasonably with the only group efficiency. In this paper, a new method for the design of pile groups is proposed, where the significant factors affecting the behavior of a pile group are considered separately by adopting several efficiencies. Furthermore, in the proposed method, the load transfer characteristics of piles and the difference of pile behaviors with respect to the pile locations in group can be taken into account. The efficiencies for the method are determined using the settlement failure criterion, which is consistent with the concept of allowable settlement fur structures. The efficiencies calculated from the results of existing model tests are presented, and the bearing capacity of a pile group in the other model test is calculated and compared with that from the test result to verify the validity of the proposed method.

A Study on the Negative Skin Friction Depending upon the Locations of Piles in a Group Using Model Test (모형시험을 통한 무리말뚝 내 말뚝의 위치별 부주면마찰력에 관한 연구)

  • Lim, Jong-Seok;Park, Jong-Hee;Sim, Jong-Sun
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.09a
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    • pp.923-932
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    • 2009
  • Generally most of pile foundations are constructed with group pile rather than single pile. The study on efficiency and bearing capacity which are major elements for rational design of this group pile has been actively progressed, whereas there are truly only a few studies of negative skin friction working on group pile due to the consolidation of ground. The purpose of this study is to determine, among the elements of negative skin friction applied to pile, the occurrence modality of negative skin friction at center, side, and corner of $3{\times}3$ group pile using model test and, based on those observations, to propose the effective design direction of group pile.

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A Group Pile Effect on Changing Size of Pile Cap in Group Pile under Sand Soil in Earthquake (지진 시 사질토 지반에 근입된 무리말뚝의 말뚝 캡 크기가 무리말뚝 효과에 미치는 영향)

  • Lee, Hyunkun;Ahn, Kwangkuk;Kang, Hongsig
    • Journal of the Korean GEO-environmental Society
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    • v.20 no.10
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    • pp.39-46
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    • 2019
  • The interaction between the ground and structures should be considered for seismic design of group piles supporting the superstructure. The p-y curve has been used widely for the analysis of nonlinear relationship between the ground and structures, and various researches have conducted to apply the dynamic p-y curve for seismic design of group piles. This curve considers the interaction between the ground and structures under the dynamic load such as an earthquake. However the supported effect by the pile cap and the interaction by inertia behavior of superstructures. Therefore, the shaking table test was conducted to verify the effect of the change of the pile cap in group piles supporting superstructures embedded in sandy soil. The test condition is that the arrangement and distance between centers of piles are fixed and the length of the pile cap is changed for various distances between the pile cap side and the pile center. The result shows that the distance between the pile cap side and the pile center have an effect on the dynamic p-y curve and the effect of group piles.

A Study on the Negative Skin Friction Depending upon the Locations of Piles in a Group Using Model Test (모형시험을 통한 무리말뚝 내 단독말뚝의 위치별 부주면마찰력에 관한 연구)

  • Lim, Jong-Seok;Park, Jong-Hee;Sim, Jong-Sun
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.03a
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    • pp.1077-1087
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    • 2010
  • Generally most of pile foundations are constructed with group pile rather than single pile. The study on efficiency and bearing capacity which are major elements for rational design of this group pile has been actively progressed, whereas there are truly only a few studies of negative skin friction working on group pile due to the consolidation of ground. The purpose of this study is to determine, among the elements of negative skin friction applied to pile, the occurrence modality of negative skin friction at center, side, and corner of $3{\times}3$ group pile using model test and, based on those observations, to propose the effective design direction of group pile.

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Effect on Dynamic Behavior of Group Piles with Changing Thickness of Pile Cap

  • Jeong, Kusic;Ahn, Sangro;Kim, Seongho;Ahn, Kwangkuk
    • Journal of the Korean GEO-environmental Society
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    • v.19 no.7
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    • pp.5-11
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    • 2018
  • Instead of a single pile, group piles are usually used for the pile foundation. If the earthquake occurs in the ground where group piles are installed, dynamic behavior of group piles are affected not only by interaction of piles and the ground movement but also by the pile cap. However, in Korea, the pile cap influence is not taken account into the design of group piles. Research on dynamic behavior of group piles has been performed only to verify interaction of piles and the ground and has not considered the pile cap as a factor. In this research, 1g shaking table model tests were performed to verify the thickness of the pile cap affects dynamic behavior of group piles that were installed in the ground where the earthquake would occur. The test results show that, as thickness of the pile cap increased, acceleration and horizontal displacement of the pile cap decreasd while vertical displacement of the pile cap increased. The results also showed that, among the group files tested, acceleration, horizontal displacement, and vertical displacement of the bearing pile are smaller than those of the friction pile.

An Experimental Study of the Effect of Pile Cap on Behaviors of Group Piles (모형실험을 통한 사질토 지반에서의 무리말뚝 거동에 대한 상부기초 접촉 효과 연구)

  • 이수형;진봉근;정충기
    • Proceedings of the Korean Geotechical Society Conference
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    • 1999.03a
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    • pp.259-266
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    • 1999
  • In case that pile cap is in direct contact with underlying soil, the bearing mechanism for pile groups, including direct bearing effect of cap and its induced influence on pile-soil-cap interaction, should be properly considered. In this paper, the effects of pile caps on behaviors of pile groups in sandy soils were investigated by model tests, which consist of tests on 3 by 3 pile groups with/without contact on subsoil, single pile with/without contact and cap as a shallow foundation. Also, the influences of pile spacing in group piles on contact effects were investigated. The test results showed that the load carrying capacity of pile cap was large enough not to be ignored. However, the interaction effects due to contact between cap and subsoils were not revealed obviously in working load range. And in the design of pile groups, the bearing effect of pile cap when contacted with subsoils, can be reflected by simply summing up load settlement behaviors of each cap and group piles without contact.

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말뚝기초의 연적 방향 극한하중

  • 김명모
    • Proceedings of the Korean Geotechical Society Conference
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    • 2002.11a
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    • pp.209-236
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    • 2002
  • Ultimate pile capacity - Point resistance - Frictional resistance - Determination of point and frictional resistances from field tests - Summary of recommendations from design Group effects Settlement analysis.

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The Effect of Dynamic Behavior on Changing Pile Cap Size of Pile Group in Sandy Soil (사질토 지반에서 말뚝 캡 크기가 무리말뚝의 동적거동에 미치는 영향)

  • Lee, Hyunkun;Ahn, Kwangkuk;Kang, Hongsig
    • Journal of the Korean GEO-environmental Society
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    • v.20 no.8
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    • pp.5-12
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    • 2019
  • A pile group, that consists of several piles connected by a pile cap, is used as the superstructure. The pile supports vertical and horizontal load to design the pile group, but the effect of bearing capacity of the pile cap has not considered. Various researches have been conducted to reflect the effect of bearing capacity of the pile cap in order to reduce the amount of piles in the range of the stability under the vertical load of the superstructure. However, the effect of bearing capacity under the horizontal seismic load has not been studied adequately. Therefore, a shaking table test was carried out with different-sized pile caps that support the superstructure in this study. This test was to verify the influence of the size of the pile cap in the group pile under the horizontal load. The result shows that the size of the pile cap affects to the dynamic behavior of the superstructure and the pile group. Also, the bigger size of the pile group makes the larger constraint effect of ground, and it results that both the ground and the pile moves as a whole.

An Experimental Study on Behavior for the Piled Raft (Piled Raft 거동특성에 관한 실험적 연구)

  • Kwon, Oh-Kyun;Lee, Seung-Hyun;Oh, Se-Boong;Lim, Jong-Seok;Lee, Whoal
    • Proceedings of the Korean Geotechical Society Conference
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    • 2002.06a
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    • pp.77-89
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    • 2002
  • To analyze a bearing capacity for pile groups, a number of model tests have been done and theoretical methods studied. In the case of design of group pile bearing capacity is calculated with only pile capacity. But uncertainty of bearing capacity and behavior of foundation cap(raft) leads to conservative design ignoring bearing effects of foundation cap. In the case of considering bearing capacity of foundation cap, the simple sum of bearing capacity of foundation cap and pile groups cannot be the bearing capacity of total foundation system. Since cap-pile-soil interaction affects the behavior of pile groups. Thus, understanding cap-pile-soil interaction is very important in optimal design. In this paper, the piled raft behavior is studied through model tests of 2$\times$2, 2$\times$3, 3$\times$3 pile group. Changes of behavior of pile group foundation by touching effects of foundation cap with soil are studied. Also changes of spacing between piles. Foundation cap is made of rigid steel plate and piles are made steel pipes. From this model tests, the changes of behavior changes of pile groups by touching effects of foundation cap with soil are studied.

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