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Slip Effect at the Pile-soil Interface on Dragload
Jeong, Sang-Seom,Lee, Cheol-Ju 한국지반공학회 2003 지반 : 한국지반공학회지 Vol.19 No.3
본 연구에서는 말뚝이 근입된 연약지반의 탄소성 해석을 수행하여 말뚝에 작용하는 하향력을 산정하였다. 이때 단독말뚝과 군말뚝(3$\times$3, 5$\times$5)을 대상으로 각각 2차원과 3차원 유한요소해석을, 말뚝주면에서 slip의 유무에 따라 수행하여 그 영향정도를 파악하였다. 하향력의 발생정도는 말뚝주면에서의 마찰계수, 지표면과 말뚝두부에 작용하는 상재하중에 큰 영향을 받는다. 이와 같은 영향인자를 토대로 수치해석 결과, 하향력은 no-slip의 경우가 slip의 경우에 비해서 상당히 과대하게 산정되었으며, 또한 말뚝두부에 하중이 증가함에 따라 하향력은 감소하는 것을 알 수 있었다. 한편 그룹효과가 있는 군말뚝의 하향력은 단독말뚝의 하향력에 비해서 크게 감소 하는 것으로 나타났으며, 수치 및 사례분석을 통해 slip 해석의 적절함을 확인하였다. The dragload on pile groups in consolidating ground was investigated based on a numerical analysis. The case of a single pile and subsequently the response of groups were analyzed by 2D and 3D finite element studies. Conventional continuum elements and special slip elements were used in the analyses for comparison. Based on a limited parametric study, it is shown that dragload for a single pile and group effect are normally overestimated by continuum analyses, compared with the predictions by the slip analyses. The group effect was examined from the slip analysis by considering various factors such as pile configurations, surface loading, interface friction coefficient, and axial loading on piles. An examplary analysis and one previous experimental observation of dragload and group effects were back-analysed. The case histories demonstrated that the slip analysis might predict a better estimate of dragload and group effect compared to the no-slip continuum analysis.
Three Dimensional Analysis of Piled Raft Foundation in Clay Soils
Sang Seom Jeong,Jae Yeon Cho 한국지반공학회 2012 international journal of geo-engineering Vol.4 No.1
The settlement behavior of a square piled raft in clay soil was investigated using numerical analysis. The emphasis was on quantifying the reduction of the average and differential settlements in soft and stiff clay soils. To obtain the detailed information on the piled raft, nonlinear three dimensional finite element analyses with pile-soil slip interface model were performed for various pile positions, pile numbers, pile lengths under the raft and different loading types. Based on the results obtained, design considerations concerning the settlement of piled rafts subjected to vertical loading are discussed. It is found that the variation of reduction ratio of soft clay was relatively greater than that of stiff clay, whereas the reduction ratio of soft clay was relatively smaller than that of stiff clays. It is also found that the required pile group-raft area ratio for minimizing differential settlement in soft clay was slightly larger than that of stiff clay in the same pile array.
The Settlement Behavior of Piled Raft Subjected to Vertical Load
Sang Seom Jeong,Jae Yeon Cho 한국지반공학회 2010 international journal of geo-engineering Vol.2 No.3
The settlement behavior of a square piled raft in clay soil was investigated using numerical analysis. The emphasis was on quantifying the reduction of the average and differential settlements in soft clay soils. To obtain the detailed information of piled raft, a nonlinear three dimensional finite element analysis with pile-soil slip interface model was performed for various pile positions, pile numbers and pile lengths under the raft. Based on the results obtained, the settlement aspects for an efficient design of piled rafts subjected to vertical loading are discussed in soft clay case.
Analysis of Piled Piers Considering Riverbed Scouring
Jeong, Sang-Seom,Suh, Jung-Ju,Won, Jin-Oh 한국지반공학회 2002 지반 : 한국지반공학회지 Vol.18 No.3
본 연구에서는 지반말뚝, 말뚝-말뚝캡, 그리고 말뚝-유체간의 상호작용 해석을 수행하여 교각세굴을 고려한 말뚝기초의 거동을 해석하였다. 지반-말뚝의 상호작용은 비선형 하중전이곡선(p-y, t-z, 그리고 q-z 곡선)을, 말뚝-말뚝캡의 상호작용에서는 군말뚝의 배열과 말뚝-말뚝캡 사이의 구속조건을 고려하였다. 말뚝유체의 상호작용은 세굴에 의한 지반의 강성 저하를 고려하여 지반-말뚝의 상호작용에 포함하여 해석하였다. 그 결과 세굴심이 깊어질수록 말뚝에 발생하는 최대 휨모멘트의 값이 증가함을 알 수 있었으며, 이를 바탕으로 세굴에 따른 군말뚝의 안정성 평가에서는 지반-말뚝 및 말뚝-말뚝캡의 상호작용을 고려한 해석을 수행하는 것이 바람직함을 알 수 있었다. This paper describes a simplified numerical procedure for analyzing the response of bridge pier foundations due to riverbed scouring. A computationally efficient algorithm to analyze the behavior of a pile group is proposed by considering soil-pile, pile-cap, and pile-fluid interactions. The complex phenomenon of the pile-soil interaction is modeled by discrete nonlinear soil springs (p-y, t-z and q-z curves). The pile-cap interaction is considered by geometric configuration of the piles in a group and connectivity conditions between piles and the cap. The pile-fluid interaction is incorporated into the procedure by reducing the stiffness of the soil-pile reactions as a result of nonlinearity and degradation of the soil stiffness with river bridge scouring. Through the numerical study, it is shown that the maximum bending moment increases with increasing scour depth. Thus it is desirable to check the stability elf pile groups based on soil-pile and pile-cap interactions by considering scouring depth in the riverbed.