• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.574-579
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• 2004

In this study, finite difference method used in order to analyze influence on settlement of shallow foundation as a result of vegetation and environmental changes, On boundary conditions to analyze, divided the foundation to clayey silt, changed the amount of evaportanspiration to consider the influence of vegetation, and assumed that the duration of enviromental changes are 180 days to consider the influence of environmental changes. It is expected that this study will do to predicting settlement of shallow foundation as well as to preventing damage of shallow foundation.

• Geomechanics and Engineering
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• 제20권4호
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• pp.345-358
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• 2020

Numerous studies have repeatedly demonstrated the efficiency of using skirts to increase the bearing capacity and to reduce settlement of shallow foundations subjected to static loads. However, no efforts have been made to study the efficiency of using these skirts to reduce settlement produced by machine vibration, although machines are very sensitive to settlement and the foundations of these machines should be designed properly to ensure that the settlement produced due to machine vibration is very small. This research has been conducted to investigate the efficiency of using skirts as a technique to reduce the settlement of a strip foundation subjected to machine vibration. A two-dimensional finite element model has been developed, validated, and employed to achieve the aim of the study. The results of the analyses showed that the use of skirts reduces the settlement produced due to machine vibration. However, the percentage decrease of the settlement is remarkably influenced by the density of the soil and the frequency of vibration, where it rises as the frequency of vibration increases and declines as the soil density rises. It was also found that increasing skirt length increases the percentage decrease of the settlement. Importantly, the results obtained from the analyses have been utilized to derive new dynamic impedance values that implicitly consider the presence of skirts. Finally, novel design equations of dynamic impedance that implicitly account to the effect of the skirts have been derived and validated utilizing a new intelligent data driven method. These new equations can be used in future designs of skirted strip foundations subjected to machine vibration.

• 한국지반공학회논문집
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• 제28권7호
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• pp.67-75
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• 2012

교량기초의 지지층인 조밀한 화강풍화토 지반에서 얕은 기초의 침하에 대한 크기효과를 평가하고자 하였다. 이를 위해 지반조건이 유사한 2개 현장에서 재하판 크기를 다르게 하여 평판재하시험을 수행하였다. 시험결과 재하판 하부 및 주변 지반의 파괴는 관찰되지 않았으며 하중 증가에 따라 침하가 비례하여 증가하였다. 이러한 결과는 대상지반에 지지되는 기초의 안정성 또는 사용성은 침하가 지배하는 것을 의미한다. 침하에 대한 기초크기 효과는 압력-침하곡선의 기울기로 표현되는 지반반력계수와 기초폭의 관계로 표현하였다. 기존에 제안된 관계식과 비교해 볼 때 본 실험결과는 크기효과가 더 크게 나타나며, 이는 기존에 제안된 관계식은 조밀한 화강풍화토 지반에 지지된 기초의 침하를 과소평가할 수 있음을 나타낸다.

• 국제초고층학회논문집
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• 제6권1호
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• pp.83-89
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• 2017

Due to the time-dependent properties of materials, structures, and loads, accurate time-dependent effects analysis and precise construction controls are very significant for rational analysis and design and saving project cost. Elevation control is an important part of the time-dependent construction control in supertall structures. Since supertall structures have numerous floors, heavy loads, long construction times, demanding processes, and are typically located in the soft coastal soil areas, both the time-dependent features of superstructure and settlement are very obvious. By using the time-dependent coupling effect analysis method, this paper compares Shanghai Tower's vertical deformation calculation and elevation control scheme, considering foundation differential settlement. The results show that the foundation differential settlement cannot be ignored in vertical deformation calculations and elevation control for supertall structures. The impact of foundation differential settlement for elevation compensation and pre-adjustment length can be divided into direct and indirect effects. Meanwhile, in the engineering practice of elevation control for supertall structures, it is recommended to adopt the multi-level elevation control method with relative elevation control and design elevation control, without considering the overall settlement in the construction process.

• 한국철도학회논문집
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• 제2권4호
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• pp.20-31
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• 1999

When a foundation on the ground with tunnel is constructed, the ultimate bearing capacity of a footing is reduced by tunnel. In practice, structure may bate a considerable damage because of large settlement. This study shows that the settlement which is caused by variety of the ultimated bearing capacity leads fatal damages to the footing above tunnel. Therefore, it is necessary to study on the reduction both of the ultimate bearing capacity which leads a failure and of tolerable settlement which satisfies the safety of the building. For this reason, the variety of ultimated bearing capacity was analyzed using tub-dimensional elasto-plastic finite difference method in this paper. As a result, bearing capacity of the foundation above tunnel should be determined after establishing limit of allowable settlement and considering reduction-ratio of bearing capacity.

• Geomechanics and Engineering
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• 제5권6호
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• pp.519-540
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• 2013

This paper presents an optimal design method for determining pile lengths of piled raft foundations. The foundation settlement is evaluated by taking into account the raft-pile-soil interaction. The analysis of settlement is simplified by using Steinbrenner's equation. Then the total pile length is minimized under the settlement constraint. An extended sequential linear programming technique combined with an adaptive step-length algorithm of pile lengths is used to solve the optimal design problem. The accuracy of the simplified settlement analysis method and the validity of the obtained optimal solution are investigated through the comparison with the actual measurement result in existing piled raft foundations.

• 한국지반공학회논문집
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• 제27권2호
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• pp.5-15
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• 2011

일본에서 개발된 원추형 팽이기초(Top-Base Foundation)와 국내에서 개발된 부양형 팽이기초(Floating Top-Base Foundation)를 대상으로 대표 점토질 연약지반인 저압축성점토, 점토질 실트, 점토질 모래에 타설하여 실내모형실험을 수행하였다. 본 실험을 통해 하중-침하량, 기초측면 히빙량, 지중응력분포 등을 측정하여 두 가지 팽이기초의 성능을 비교 평가하였다. 또한, 단변길이 증가에 따른 침하량 변화를 분석하였다. 실내모형실험 결과 부양형 팽이기초가 지지력 증진, 침하량 저감, 응력분산효과, 측방구속력에 대해서 좀 더 우수한 성능을 발휘하는 것으로 나타났으며, 기초폭증가에 따른 침하량은 팽이기초 $5{\times}5$배열을 기점으로 수렴하였다.

• 한국해양공학회지
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• 제18권3호
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• pp.20-25
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• 2004

For the structural foundation above the soft clay layer conditions, the design charts are first presented for the evaluation of both bearing capacity and total settlement in the basic raft foundation system. wad settlement relationship curves are used to evaluate the ultimate soil bearing capacity. The total settlement is evaluated by applying various traditional factors into the ultimate bearing capacity. Then, the parametric studies are carried out for the piled-raft foundation system. In the numerical analysis, the elasto-pastic finite element model(Mohr-Coulomb model) is used to present the foundation response and design charts, which enable the determination of the raft size and pile length and spacing.

• Geomechanics and Engineering
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• 제34권6호
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• pp.649-664
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• 2023

Structural inertial interaction is a representative the effect of dynamic soil-foundation-structure interaction (SFSI), which leads to a relative displacement between soil and foundation, period lengthening, and damping increasing phenomena. However, for a system with a significantly heavy foundation, the dynamic inertia of the foundation influences and interacts with the structural seismic response. The structure-to-foundation mass ratio (MR) quantifies the distribution of mass between the structure and foundation for a structure on a shallow foundation. Although both systems exhibit the same vertical factor of safety (FS_v), the MR and corresponding seismic responses attributed to the structure and foundation masses may differ. This study explored the influence of MR on the permanent deformation and seismic response of soil-foundation-structure system considering SFSI via numerical simulations. Given that numerous dimensionless parameters of SFSI described its influence on the structural seismic response, the parameters, except for MR and FS_v, were fixed for the sensitivity analysis. The results demonstrated that the foundation inertia of heavier foundations induced more settlement due to sliding behavior of heavily-loaded systems. Moreover, the structural inertia of heavier structures evidently exhibited foundation rocking behavior, which results in a more elongated natural period of the structure for lightly-loaded systems.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.691-699
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• 2008

In the design of a foundation, settlement of the foundation may exceed allowable design criteria even with a competent bearing stratum. In such a case, a piled-raft foundation system may be adopted using piles as settlement reducing component. In this paper, Disconnected Piled Raft Foundation (DPRF) system, which installs disconnected piles underneath the raft and uses the piles as ground reinforcements, is studied as a cost effective design method against the classical piled-raft foundation system. To this end, large size loading tests were carried out on weathered ground changing area replacement ratio and length of piles. The results indicated that the settlement of the reinforced ground was reduced by 34~87% and the allowable bearing pressure increased by 70% on average from those of the unreinforced original ground, respectively. The correlating formula between the area replacement ratio and the load bearing ratio of piles were derived from the test results and numerical analysis. From the correlation, a design method determining the size and the quantity of the disconnected piles to enhance the bearing capacity of original ground to the desired value was proposed based on one inch settlement criteria.