• 기술발표회
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• s.2006
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• pp.115-132
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• 2006

본 글은 부산-김해간 경량전찰 건설공사의 기초설계시 현장타설말뚝 기초의 지지층을 모래자갈층으로 적용한 사례이다. 낙동강 유역은 퇴적층이 발달하여 풍화암 이상의 기반암층이 지표하 60~80m 이후에서 출현하며, 40m 이상의 심도에서 매우 조밀한 상태의 모래자갈층이 10-20m 두께로 분포하고 있어, 모래자갈층을 관통하여 기반암에 말뚝기초를 지지할 경우 기초공사에 상당한 기간이 소요될 뿐만 아니라, 시공성과 경제적인 측면에서 매우 불리하다. 이에 대한 개선방안으로 대구경 현장타설말뚝을 N치 50 이상의 조밀한 상태의 모래자갈층에 지지하였으며, 인근현장의 적용사례, 기초 구조물 안전성 검토 및 현장재하시험 등의 비교분석을 통하여 모래자갈 지지층의 적정성을 확인하였다. 따라서, 풍화암 이상의 지지지반 출현심도가 60m 이상으로 매우 깊고, 지지지반 상부에 모래자갈층이 두껍게 분포하는 경우에는 모래자갈층을 말뚝기초의 지지층으로 활용하는 방안이 시공성 및 경제성 측면에서 합리적이라 판단된다.

• Journal of the Korean Geotechnical Society
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• v.27 no.1
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• pp.5-16
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• 2011

This paper presents the results of a three-dimensional finite element analysis on load supporting mechanism of pile constructed above underground cavity in limestone rock formation. Considering a wide range of cavity conditions, the behavior of pile was studied using the bearing capacity, rock yielding pattern, stress distribution and deformation of pile head and the cavity. The results indicate that the load transfer mechanism of pile, rock yielding pattern and the reduction of bearing capacity of pile significantly vary with the location, size and length of cavity. Based on the results, graphical solutions defining the reduction of the bearing capacity with specific cavity conditions were suggested.

• Geotechnical Engineering
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• v.7 no.2
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• pp.67-82
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• 1991

When bridge abutments are constructed on pile foundations in unstable slope, horizontal deflections may be developed in the piles and the abutments due to lateral soil movements arisen from backfills. In most of the above mentioned cases, the piles are situated in a soft layer where lateral earth pressures are developed between the piles and the soils. The undesirable lateral earth pressures decreases the stability of the piles. However, the piles may have a preventive effect against lateral soil movements and improve the stability of the slope. For the stability problem of such slope containing piles in a row, two kinds of analyses for the slope-stability and the pile-stability have to be performed. The whole stability of bridge abutments on pile foundation can be obtained only by the stabilization for both the slope and the piles. A reasonable analytical method for the bridge abutments on pile foundation was established in this study By use of the analytical method for an example, several factors which influence affect the stability of bridge abutment were investigated. Finally, for the bridge abutment subjected to lateral deflections damage, the fixity condition of pile head was investigated.

• 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.

• Journal of the Korean Geotechnical Society
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• v.35 no.1
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• pp.17-30
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• 2019

This study presents the application of the numerical and analytical technique to simulate the Load Distribution Ratio (LDR) and to define axial stiffness on reinforcing pile foundation ($K_{vr}$) in vertical extension remodeling structure. The main objective of this study was to investigate the LDR between existing piles and reinforcing piles. Therefore, to analyze the LDR, 3D FEM analysis was performed as variable for elastic modulus, pile end-bearing condition, raft contacts, and relative position of reinforcing pile in a group. Also, using the axial stiffness ($K_{ve}$) of existing piles, the axial stiffness of reinforcing pile was defined by 3D approximate computer-based method, YSPR (Yonsei Piled Raft). In addition $K_{vr}$ was defined by reducing the $K_{ve}$considering the degradation of the existing piles.

• Journal of the Korean GEO-environmental Society
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• v.11 no.2
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• pp.23-32
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• 2010

Demand on pile foundation is rapidly increasing, as an investment for the social overhead capital getting enlarged in Korea. Steel piles are in general use in construction due to their workability and superior durability. But the recent global rise in steel price led the engineers to seeking for an economical alternative that still has equivalent characteristics as compared with the steel pile. In this regard a composite pile, in which steel suitable to resist the tensile stress are used in the upper part of the pile, while less expensive PHC pile is adopted in the lower part of the pile where axial stress should prevail, was studied and both pile loading test and load transfer test were performed for the piles which have been constructed for the foundation of a bridge in Korea. These test results and some theories already issued were compared, and it was shown that p-y nonlinear analysis gave rise to similar results.

• Journal of the Korean Geotechnical Society
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• v.28 no.8
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• pp.31-41
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• 2012

Pile foundation for transmission tower constructed in weak ground can cause the damage of the tower due to the different settlement between the foundations. In Japan and USA, connected-pile foundations whose 4 foundations are connected each other by beams were used for transmission tower (TEPCO 1988, IEEE 2001). Resistance increasing factors for connected-pile foundation signify increasing amount of resistance due to the effect of connected-pile material. In this study, we performed model lateral load tests of connected-pile foundations for transmission tower and found the resistance increasing factors for connected-pile foundation. The tests were performed in silty clay, and the resistance increasing factors were founded in various conditions that lateral load directions and height, the stiffness of beams in the connected-pile foundations were changed. The resistance increasing factors from our research were presented as a function of normal lateral loading height and normal stiffness of the connected-pile material. The resistances which were estimated from the resistance increasing factors were similar to measured values.

• 지반과기술
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• v.5 no.3
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• pp.33-37
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• 2008

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.1
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• pp.83-91
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• 2017

In case of estimation of settlement for the piled-raft foundation, it is necessary to consider interaction among raft, piles and soil. But, simple analytic methods usually are not applicable to considering this complicated interaction. In this study, a computer-based approximate analytic method, HDPR, was developed in consideration of above mentioned interaction in order to analysis of settlement for the piled-raft foundation. The finite element method was applied to raft analysis by means of the Mindlin plate theory, and soil and piles were modeled as springs which were connected with their raft. The linear spring which can consider multi layered soil and the non-linear spring were applied to soil springs and pile springs, respectively. The raft-piles-soil interaction was reflected to each spring. In order to verify the developed analytic method, it was compared and analyzed with 3D FEM analysis, existing approximate analytic method and site monitoring data. As a result, the developed analytic method showed reasonable results of settlement estimations of raft and piles for each case. From a practical point of view, it is confirmed that this analytic method is able to apply for analysis and design of the piled-raft foundation.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.3
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• pp.1-8
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• 2001

Seismic design forces for bridge components may be determined by modifying elastic member forces of design earthquakes using appropriate response modification factors according to the national design code of bridges Modeling technique of pile foundation system is one of the important parameters which greatly affects the results in the process of the elastic seismic analysis of a bridge system with pile foundation. In this paper, a approximate and simplified modeling technique of a pile foundation system for the practical purposes is presented. The modeling technique is based on the stiffnesses of pile foundation during earthquake. The horizontal stiffnesses are determined from the resistance-deflection curves derived from the results of dynamic field tests using cyclic loads and the vertical stiffness includes the effects of the end bearing capacities and side friction of piles as well as the pile compliances under the expected vertical load level. The applicability of the proposed technique has been validated through the some example bridge analyses.