• 헤리티지:역사와 과학
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• 제42권3호
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• pp.66-87
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• 2009

적석목곽묘는 목곽 외부에 석재를 쌓거나 채운 다음 목개 위에 일정한 두께로 적석하고 점토로 밀봉한 구조이다. 경주 중심부라는 한정된 공간 속에 거의 모든 지배자가 지속적으로 한 묘제를 사용하였다는 점, 타 지역에서 확인되는 적석 형태와 전혀 다르다는 점 등에서 경주식 적석목곽묘로 정의하고자 한다. 적석목곽묘는 경주 중심부에서 5C 전반대부터 축조되기 시작한다. 평면형태, 목곽, 이중곽, 석재충전, 석단, 순장 등은 이전시기의 목곽묘에서 계보를 잇고 있다. 이외에 석축과 목주, 적석, 성토분구는 적석목곽묘의 출현과 함께 새롭게 나타나는 요소이다. 특히 석축과 목주는 황남대총을 비롯한 지상식 초대형분에서만 확인된다. 석축과 목주, 적석은 모두 성토 분구 축조과정 속에서 하나의 공정을 이루고 있다. 석축은 지상에 설치된 목곽의 외벽을 견고하게 유지시켜 주면서 성토 분구의 하중을 분산 수용한다. 목주는 석축의 붕괴를 방지하기 위한 보조장치로서 횡가목, 버팀목 등과 함께 사용되었다. 적석은 일정 크기의 석재를 갖고 일정한 두께로 목개 상부에 덮었다. 그리고 그 위에 점토로 밀봉한 다음 분구를 성토하였다. 적석은 경주지역의 입지적 특성이 반영된 것으로 파악된다. 경주 중심부의 적석목곽묘는 하천부지가 넓고 평탄한 형산강 동안을 따라 분포한다. 기반층은 대부분 모래와 냇돌로 구성되어 있다. 따라서 성토분구는 모래성분을 많이 함유하고 있다. 목개를 횡가한 다음 바로 성토할 경우 유수에 의한 붕괴 가능성 또한 크다. 고분의 외형을 유지하면서 내부구조물의 파괴를 방지하기 위하여 적석과 점토밀봉이 이루어진 것으로 판단된다. 상부의 봉토가 유실되더라도 하부의 적석은 형태를 어느 정도 유지할 것이기 때문이다. 성토분구는 국가 혹은 단위정치체가 성장단계에 진입하면서 나타나는 하나의 특징이다. 국가 출현단계 이후 성장단계에 진입하면서 사회구조에 변화가 나타나고 이와 맞물려 새롭게 출현한 지배등급에서 전대의 목곽묘와는 다른 적석목곽묘를 축조하기 시작한 것으로 판단된다. 이 과정에서 분구를 함께 성토한 것으로 파악되며, 지배등급의 성격에 따라 규모와 구조에서 차이를 보인다. 평면형태, 곽과 석단, 순장자의 수, 유물의 양과 질 등은 지배등급의 사회적 지위를 반영하고 있다. 따라서 적석목곽묘는 신라가 성장단계에 접어든 시점에 전대의 묘제로부터 분화 발전된 양상을 보이면서 나타난것으로 생각된다.

• 한국지반공학회논문집
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• 제32권8호
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• pp.35-46
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• 2016

본 연구에서는 지반조건에 따른 실제 piled raft 기초의 거동을 실규모 시험을 통해 분석하기가 어려운 점을 감안하여 수치해석을 이용한 민감도분석을 수행하고자 하였다. 수치해석에 사용한 프로그램은 유한차분법 기반의 FLAC 3D이다. 말뚝의 수치해석 모델링은 FLAC의 구조요소 중 하나인 말뚝요소를 사용하여 모델링하였고, 지반과 래프트는 연속체 요소를 이용하여 모사하였다. 말뚝의 배열은 $3{\times}3$으로 고정하고 말뚝직경, 말뚝길이, 말뚝간격 그리고 지반조건을 민감도 매개변수로 선정하고 상관관계를 규명하였다. 그 결과, 말뚝직경이 크고 말뚝의 길이가 길수록, 그리고 말뚝의 간격이 넓을수록 piled raft 기초의 전체 지지력은 증가하는 것으로 나타났다. 그러나 지반조건에 따라 말뚝간격이 일정 간격 이상이 될 경우, piled raft 기초의 거동이 래프트만으로 지지되는 얕은기초와 유사한 거동을 보였다. 또한 지반조건이 좋아질수록, piled raft 기초의 전체 지지력은 증가함을 확인할 수 있었다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2003년도 춘계 학술발표회논문집
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• pp.193-199
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• 2003

The most cultural heritages are composed of piled multi-block systems which are vulnerable to earthquakes. The stone of low height tends to slide when the excitation such as earthquake is applied and this sliding motion has effects on the whole response of the structure. In this study, analytical method of sliding motion of the piled multi-block systems considering horizontal rotation is developed and compared with shaking table test results. It is shown that the nonlinear analysis of sliding motion of multi-block system leads to satisfactory results.

• Geomechanics and Engineering
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• 제14권1호
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• pp.43-50
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• 2018

Applicability of constructing piled raft foundations on soft clay has been given attention in recent years. Lack of sufficient stiffness for soil and thus excessive settlements to allow higher contribution of piles is the major concern in this regard. This paper presents a numerical investigation of performance of piled-raft foundations on soft clay with focusing on a case study. A 3D FEM numerical model is developed using ABAQUS. The model was calibrated by comparing physical and numerical modeling results of other researchers. Then the possibility of using piled-raft system in construction of foundation for a water storage tank in Sarbandar, Iran is assessed. Soil strength parameters in the numerical model were calibrated using the instrumentation data of a heavily instrumented preloading project at the construction site. The results indicate that choosing the proper combination of length and spacing for piles can lead to acceptable differential and total settlements while a high percentage of total bearing capacity of piles can be mobilized, which is an efficient solution for the project. Overall, the construction of piled-rafts on soft clays is promising as long as the total settlement of the structure is not imposing restrictions such as the common 25 mm allowable settlement. But instead, if higher allowable settlements are adopted, for example in the case of rigid steel tanks, the method shall be applicable with considerable cost savings.

• Structural Engineering and Mechanics
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• 제55권1호
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• pp.161-189
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• 2015

Soil-pile raft-structure interaction is recognized as a significant phenomenon which influences the seismic behaviour of structures. Soil structure interaction (SSI) has been extensively used to analyze the response of superstructure and piled raft through various modelling and analysis techniques. Major drawback of previous study is that overall interaction among entire soil-pile raft-superstructure system considering highlighting the change in design forces of various components in structure has not been explicitly addressed. A recent study addressed this issue in a broad sense, exhibiting the possibility of increase in pile shear due to SSI. However, in this context, relative stiffness of raft and that of pile with respect to soil and length of pile plays an important role in regulating this effect. In this paper, effect of relative stiffness of piled raft and soil along with other parameters is studied using a simplified model incorporating pile-soil raft and superstructure interaction in very soft, soft and moderately stiff soil. It is observed that pile head shear may significantly increase if the relative stiffness of raft and pile increases and furthermore stiffer pile group has a stronger effect. Outcome of this study may provide insight towards the rational seismic design of piles.

• Coupled systems mechanics
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• 제5권1호
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• pp.41-58
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• 2016

The study deals with physical modeling of a typical building frame resting on pile raft foundation and embedded in cohesive soil mass using finite element based software ETABS. Both- the elements of superstructure and substructure (i.e., foundation) including soil is assumed to remain in elastic state at all the time. The raft is modelled as a thin plate and the pile and soils are treated as interactive springs. Both- the resistance of the piles as well as that of raft base - are incorporated into the model. Interactions between raft-soil-pile are computed. The proposed method makes it possible to solve the problems of uniformly and large non-uniformly arranged piled rafts in a time saving way using finite element based software ETABS. The effect of the various parameters of the pile raft foundation such as thickness of raft and pile diameter is evaluated on the response of superstructure. The response included the displacement at the top of the frame and bending moment in columns. The soil-structure interaction effect is found to increase displacement and increase the absolute maximum positive and negative moments. The effect of the soil- structure interaction is observed to be significant for the type of foundation and soil considered in the present study.

• 한국지반공학회논문집
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• 제28권4호
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• pp.67-78
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• 2012

철지반의 비선형성을 고려한 말뚝지지 전면기초의 3차원 해석기법(YSPR)을 개발하였다. 전면기초는 6개의 자유도를 가진 평면쉘 요소로, 말뚝은 보-기둥 요소로 모델링하여 전면기초와 결합하였다. 또한 말뚝두부 및 지반의 강성은 $6{\times}6$ 강성행렬로 모델링 하였으며, 전면기초-말뚝-지반의 상호작용은 비선형 하중전이함수를 이용하여 선형/비선형거동의 모사가 가능하도록 하였다. 기존의 단순해석기법, 유한요소해석 및 현장계측값과의 비교 분석 결과, 본 해석기법이 대단면 말뚝지지전면기초에서 말뚝의 축하중 분포와 침하량을 비교적 정확히 산정하는 것으로 판단되며, 이러한 검증을 토대로 실제 대단면 기초설계에 대한 적용 가능함을 확인할 수 있었다.

• Geomechanics and Engineering
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• 제14권5호
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• pp.479-489
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• 2018

In this paper, a comparative study of the effects of soil modelling on the interaction between tunnelling in soft soil and adjacent piled structure is presented. Several three-dimensional finite element analyses are performed to study the deformation of pile caps and piles as well as tunnel internal forces during the construction of an underground tunnel. The soil is modelled by two material models: the simple, yet approximate Mohr Coulomb (MC) yield criterion; and the complex, but reasonable hardening soil (HS) model with hyperbolic relation between stress and strain. For the former model, two different values of the soil stiffness modulus ($E_{50}$ or $E_{ur}$) as well as two profiles of stiffness variation with depth (constant and linearly increasing) were used in attempts to improve its prediction. As these four attempts did not succeed, a hybrid representation in which the hardening soil is used for soil located at the highly-strained zones while the Mohr Coulomb model is utilized elsewhere was investigated. This hybrid representation, which is a compromise between rigorous and simple solutions yielded results that compare well with those of the hardening soil model. The compared results include pile cap movements, pile deformation, and tunnel internal forces. Problem symmetry is utilized and, therefore, one symmetric half of the soil medium, the tunnel boring machine, the face pressure, the final tunnel lining, the pile caps, and the piles are modelled in several construction phases.

• Geomechanics and Engineering
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• 제5권1호
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• pp.17-36
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• 2013

Settlement of the piled raft can be estimated even after years of completing the construction of any structure over the foundation. This study is devoted to carry out numerical analysis by the finite element method of the consolidation settlement of piled rafts over clayey soils and detecting the dissipation of excess pore water pressure and its effect on bearing capacity of piled raft foundations. The ABAQUS computer program is used as a finite element tool and the soil is represented by the modified Drucker-Prager/cap model. Five different configurations of pile groups are simulated in the finite element analysis. It was found that the settlement beneath the piled raft foundation resulted from the dissipation of excess pore water pressure considerably affects the final settlement of the foundation, and enough attention should be paid to settlement variation with time. The settlement behavior of unpiled raft shows bowl shaped settlement profile with maximum at the center. The degree of curvature of the raft under vertical load increases with the decrease of the raft thickness. For the same vertical load, the differential settlement of raft of ($10{\times}10m$) size decreases by more than 90% when the raft thickness increased from 0.75 m to 1.5 m. The average load carried by piles depends on the number of piles in the group. The groups of ($2{\times}1$, $3{\times}1$, $2{\times}2$, $3{\times}2$, and $3{\times}3$) piles were found to carry about 24%, 32%, 42%, 58%, and 79% of the total vertical load. The distribution of load between piles becomes more uniform with the increase of raft thickness.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.967-975
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• 2009

In order to control differential settlement and to secure the safety of super structure on a high rock embankment the designed static compaction is changed with dynamic compaction and piled raft method. The parameters for dynamic compaction design are obtained from a pilot test. In addition, numerical analyses are also carried out to figure out the length and quantity of piled raft that can restraint the differential settlement within allowance range.