• 기술발표회
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• 통권2006호
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• pp.86-100
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• 2006

The single drilled shaft foundation has been used in the other countries, but has not used in South Korea at all This foundation is very effective and economic method in South Korea which is easy to meet a good rock mass within 50m depth from the ground We have many experiences to construct 1.52 5m drilled shaft foundations and ability to construct 30m drilled shaft foundation without special efforts The soil behavior is nonlinear, but it can be proposed in linear in practical purpose on bridges. The elastic modulus of soil can be rationally obtained by the method of Road Bridge Design Manual in South Korea using the Schmertmann(1970)'s proposal, and the elastic modulus of rock can be obtained by the field test. In seismic design the column and drilled shaft must be restricted to the elastic design because the behavior of this foundation is flexible and the arrangement of the rebars makes the various defect In this paper the design criteria is compared with FHWA design criteria, and the design criteria is proposed in consistent with Road Bridge Design Manual in South Korea. The single drilled shaft foundation of a test bridge was constructed in the Iksan-Jangsoo highway, and we checked its stability, workability and economy

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.58-65
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• 2004

Recently, the top & down method with drilled shafts as a foundation of high rise building is often adopted for the purpose of construction period reduction and construction cost effectiveness. It is common to omit the loading test as a Quality assurance on account of the high capacity of drilled shafts for the top & down method. It seems that the capacity of drilled shaft in recent top & down method is beyond that of conventional loading test method.However, the quality assurance for the drilled shaft as foundation of high rise building becomes much more important since the drilled shaft should bear much higher working load. It may be a small scale test pile could be an alternative as a quality assurance for the drilled shaft with high capacities. Through a case study, this paper gives an idea for solving the limitation of the conventional loading test method for the quality assurance of drilled shaft with high capacities. In particular, this paper analyzed the scale effect for a small drilled shaft installed into bedrock, which could be used for an alternative.

• Geomechanics and Engineering
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• 제24권5호
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• pp.431-441
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• 2021

Rock-socketed drilled shafts are widely used to transfer the heavy loads from the superstructure especially in mountainous area. Extensive research has been done on the behavior of rock-socketed drilled shafts under compressive load. However, little attention has been paid to uplift behavior of drilled shaft in rock, which govern the overall behavior of the foundation system. In this paper, a series of centrifuge tests have been performed to investigate the uplift response of rock-socketed drilled shafts. The pull-out tests of drilled shafts installed in layered rocks having various strengths were conducted. The load-displacement response, axial load distributions in the shaft and the unit skin friction distribution under pull-out loads were investigated. The effects of the strength of rock socket on the initial stiffness, ultimate capacity and mobilization of friction of the foundation, were also examined. The results indicated that characteristics of rock-socket has a significant influence on the uplift behavior of drilled shaft. Most of the applied uplift load were carried by socketed rock when the drilled shaft was installed in the sand over rock layer, whereas substantial load was carried by both upper and lower rock layers when the drilled shaft was completely socketed into layered rock. The pattern of mobilized shaft friction and point where the maximum unit shaft friction occurred were also found to be affected by the socket condition surrounding the drilled shaft.

• 한국지반공학회논문집
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• 제20권5호
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• pp.117-126
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• 2004

최근 건축구조물이 대형화됨에 따라 현장타설말뚝을 이용한 Top-Down공법이 공기단축 및 경제성 등의 이유로 자주 채택되고 있다. Top-Down 기초로 시공되는 현장타설말뚝의 경우 설계하중이 크다는 이유로 인해 품질확인용 재하시험을 생략하는 경우가 대부분이며, 대규모 설계하중을 검증하기 위한 전통적인 재하시험 방법 또한 적용하기 곤란한 경우가 많다. Top-Down 공법에 있어 건축구조물의 대형화에 의한 현장타설말뚝의 사용하중이 증대됨에 따라 현장타설말뚝에 대한 품질확인은 점차 중요시되고 있으며, 이에 대한 대안으로서 축소모형말뚝을 이용한 시험방법의 적용이 가능할 것으로 판단된다. 본 연구에서는 대구경 현장타설말뚝의 지지력 측정시 전통적인 재하시험 방법의 한계를 극복하기 위하여 축소모형말뚝을 이용하는 방안을 제시하였으며 특히, 시험결과의 해석을 위해 암반에 근입된 현장타설말뚝의 치수효과에 관한 분석 방법을 제안하고 평가해 보았다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 추계 학술발표회
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• pp.585-592
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• 2006

Recently, many high rise buildings is planning and under construction over the world. The drilled shafts as a foundation of high rise buildings are often adopted fur the purpose of construction safety and construction cost effectiveness. It is common that the capacity of drilled shafts is beyond conventional conception. The reasonable design and quality assurance for the drilled shaft as foundation of high rise building become much more important since the drilled shafts should bear much higher working load. This paper reviews state of the art of the design and quality assurance for the drilled shafts as foundation of high rise buildings. And also some related suggestions are given in this paper.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.285-292
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• 2000

Though there has been increasing use of large diameter drilled shaft as a foundation structure of bridges, current practice for quality control is to confirm the minimum required load carrying capacity during construction stage. For economic and appropriate design of drilled shaft, it is necessary to evaluate the load transfer mechanism by pile load tests during initial stage of construction and to use the test results as a feedback to a revision of initial design. In this paper, results of load tests peformed at several domestic sites are presented to investigate the load transfer characteristics of large diameter drilled shaft. It was found that most of the load on piles is sustained by shaft friction and that only small portion of the load reaches the bottom of the drilled shaft. Some test results of drilled shaft by Pile Driving Analyzer performed at same sites are also presented to compare the load transfer characteristics interpreted from static pile load tests.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 기초기술위원회 워크샵
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• pp.140-167
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• 2002

A drilled shaft is a deep foundation that is constructed by placing fluid concrete in a drilled hole. Reinforcing steel can be installed in the excavation, if desired, prior to placing the concrete. Drilled shafts provide excellent foundation systems for civil structures. In order to utilize them effectively, it is essential that designers have a clear understanding for how drilled shafts are constructed and also understand the basis for design methods. This paper describes standard design methods for drilled shafts.

• 한국지반환경공학회 논문집
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• 제16권1호
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• pp.5-16
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• 2015

장대교량의 공사비에서 대형 해상기초가 차지하는 비중은 약 40% 수준이다(KICTEP, 2007). 본 연구에서는 가상의 초장대 사장교에서 대수심 대형 복합기초에 대하여 3가지 설계법(허용응력 설계, LRFD 설계, 유로코드 설계)으로 설계검토를 실시하였고, 3차원 유한요소 해석을 통하여 대구경 현장타설말뚝의 거동에 관한 연구를 수행하였다. 그 결과, 허용응력 설계에서 추정한 방법이 연암 소켓길이가 가장 길었다. LRFD와 유로코드 설계법 2에 의해 계산된 연암소켓 길이는 유사하였다. 대구경 현장타설말뚝의 연암소켓길이가 길어짐에 따라 대구경 현장타설말뚝 두부에 작용하는 축력은 작아졌으며 현장타설말뚝의 침하량도 작아졌다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.658-663
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• 2010

Recently the most of deep foundation were socketed into weathered rock or soft rock to carry large foundation loads. The end bearing behavior of piles socketed in rock is generally dependent on the rock mass conditions with discontinuities and rock strength. Therefore, it is very important that the estimating rock classification with relation of TCR, RQD and unpredicted rock condition. In this study, the construction failure example of drilled shaft due to mistaking to estimate the rock classification on penetration were analyzed in site, so we hope to discuss problems of determining the rock socketed length of drilled shaft on construction.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.554-563
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• 2009

The trend of current urban redevelopment and new city development project shows that the superstructure of building is getting larger and higher in consequence of a limited plottage condition. For this reason, it is definitely required to extend pile diameter and install more deep foundation(Mega foundation) to support superstructure. The existing precast pile construction method causes construction-related problems such as increasing quantities, difficulty of storage & transportation material and decreasing design load while construct pile in deep foundation. The drilled shaft method has applied to minimize those problems. This article will be presented construction case study of design & construction of R.C.D method for a large building foundation work on the inside and outside of the country.