• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2008년도 정기학술발표대회 논문집
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• pp.344-348
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• 2008

최근 구조물의 고층화, 대형화 등 여러 가지 사회적 요구에 따라 기존 PC 말뚝의 개선책으로 PHC말뚝이 실용화 되었다. 현재는 대부분의 현장에서 PHC말뚝이 사용되고 있으며, 국내 콘크리트 말뚝 총 생산량의 90%이상을 점유하고 있다. 기성콘크리트 파일 공사의 굴착 및 파일 매입 작업의 국내 시방기준에는 파일을 연직으로 시공해야한다는 것만이 명시되어 있을 뿐, 이에 대한 측정기준 및 시공기준이 제시되어있지 않으며, 대부분의 시공현장에서는 숙련노무자의 경험을 통한 육안측정에 의존하고 있는 실정이다. PHC 파일의 두부정리 작업은 노동집약적이며 단순 반복적인 작업으로 숙련된 노무자에게 많이 의존해왔으며, 파일의 종 방향 균열 및 두부파손 등의 문제점이 발생되고 있다. 본 논문은 PHC 파일 시공 전 과정에서 발생되는 문제점을 분석하고 그에 대한 개선방안을 도출하기 위해 설문조사 및 면담을 실시하였다. 설문조사 및 면담을 통해 파일적재, 현장 내 소운반, 파일위치표시, 연직체크, 굴착 및 항타, 그라인딩, 안전사고의 주요 문제점을 도출하였고, 그에 대한 개선방안을 제시하였다.

• 한국지반공학회지:지반
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• 제11권4호
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• pp.25-36
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• 1995

내관과 외관이 분리된, 특별하게 제작된 모형 개단 말뚝을 상이한 방법으로 압력토조내에 설치하여 정적 압축 재하 실험을 실시하였다. 개단 말뚝 각 지지부에서의 지지력을 분리.측정하여 개단 말뚝의 지지 메카니즘과 관내토의 폐색 거동 특성을 고찰하였다. 상대밀도 49%의 모형 지반에 타격 관입된 말뚝의 관내토폐색력은 관입도중 20%정도 발휘되고 압축재하시에 대부분이 발휘되며, 토조에 작용된 구속 압력은 관내토 폐색에 크게 영향을 미치지 않았다. 그러나, 진동 관입된 말뚝의 관내토 폐색력은 관입도중에는 전혀 발생하지 않으며, 압축재하시에 약하게 형성되고, 타격 관입말뚝의 그것의 0.5~0.7배 정도가 발휘되는데 토조에 작용된 구속 압력은 관내토 폐색에 크게 영향을 미쳤다. 단위 관내토 폐색력은 극한 상태에서 최대값에 도달하지 않았다. 즉, 극한 상태에서 관내토는 파괴상태에 도달되지 않았다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 말뚝기초 학술발표회
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• pp.51-63
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• 2000

Because of simplicity and easiness, dynamic pile driving formulae have long been used by most of the field engineers for pile quality control purposes. Yet their reliability have been repeatedly reported unsuitable and the results can lead to significant errors. According to the research results by the authors, the two most important sources of unreliability of dynamic pile driving formulae are uncertainty in the estimation of hammer efficiency and time dependent characteristics of pile bearing capacity. Based on this finding a new method is proposed. By using the actual value of hammer efficiency the pile bearing capacity at the time of driving could be reasonably estimated. By performing restrike test sometime after pile installation, time effect coefficient could be determined. The effectiveness of the proposed method was proven in the actual construction project.

• Geomechanics and Engineering
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• 제21권5호
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• pp.489-501
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• 2020

This paper conducts a complicated coupled effective stress analysis of X-section-in-place concrete (XCC) pile installation and consolidation processes using the dual-stage Eulerian-Lagrangian (DSEL) technique incorporating the modified Cam-clay model. The numerical model is verified by centrifuge data and field test results. The main objective of this study is to investigate the shape effect of XCC pile cross-section on radial total stress, excess pore pressure and time-dependent strength. The discrepancies of the penetration mechanism and set-up effects on pile shaft resistance between the XCC pile and circular pile are discussed. Particular attention is placed on the time-dependent strength around the XCC pile shaft. The results show that soil strength improved more significantly close to the flat side compared with the concave side. Additionally, the computed ultimate shaft resistance of XCC pile incorporating set-up effects is 1.45 times that of the circular pile. The present findings are likely helpful in facilitating the incorporation of set-up effects into XCC pile design practices.

• Geomechanics and Engineering
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• 제5권3호
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• pp.195-221
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• 2013

A centrifuge model study is carried out to investigate the behavior of pile subject to negative skin friction induced by pile installation, ground water drawdown and surcharge loading. A single end-bearing pile is examined as the induced negative skin friction would induce the most severe stress on the pile structural material as compared to friction piles. In addition, the behavior of the pile under simultaneous negative skin friction and dead/live loads is examined. To facilitate detailed interpretations of the test results, the model setup is extensively instrumented and involves elaborate test control schemes. To further examine the phenomenon of negative skin friction on an end-bearing pile, finite element analyses were conducted. The numerical analysis is first validated against the centrifuge test data and subsequently extended to examine the effects of pile slenderness ratio, surcharge intensity and pile-soil stiffness ratio on the degree of mobilization of negative skin friction induced on the pile. Finally experimental and numerical studies are conducted to examine the effect of applied transient live load on pile subject to negative skin friction.

• Geomechanics and Engineering
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• 제5권3호
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• pp.241-261
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• 2013

The bearing mechanism of pile during installation and loading process which controls the deformation and distribution of strain and stress in the soil surrounding pile tip is complex and full of much uncertainty. It is pointed out that particle crushing occurs in significant stress concentrated region such as the area surrounding pile tip. The solution to this problem requires the understanding and modeling of the mechanical behavior of granular soil under high pressures. This study aims to investigate the sand behavior around pile tip considering the characteristics of sand crushing. The numerical analysis of model pile loading test under different surcharge pressure with constitutive model for sand crushing is presented. This constitutive model is capable of predicting the dilatancy of soil from negative to positive under low confining pressure and only negative dilatancy under high confining pressure. The predicted relationships between the normalized bearing stress and normalized displacement are agreeable with the experimental results during the entire loading process. It is estimated from numerical results that the vertical stress beneath pile tip is up to 20 MPa which is large enough to cause sand to be crushed. The predicted distribution area of volumetric strain represents that the distributed area shaped wedge for volumetric contraction is beneath pile tip and distributed area for volumetric expansion is near the pile shaft. It is demonstrated that the finite element formulation incorporating a constitutive model for sand with crushing is capable of producing reasonable results for the pile loading problem.

• 한국해안·해양공학회논문집
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• 제27권1호
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• pp.9-13
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• 2015

본 연구에서는 일본 히로시마시 텐마강 하구에 위치한 점토질 갯벌을 대상으로 투수성이 높은 다공질 파일을 설치하여 갯벌 내부에서의 지하수 흐름 형성여부를 확인하고 그에 따른 저질의 성상변화를 조사하였다. 하천의 수위가 변할 때 하천수가 다공질 파일의 하부 및 상부를 통해 공급되면서 갯벌 내부에서 지하수의 흐름이 형성되는 것이 확인되었다. 지하수의 흐름을 통해 다공질 파일내의 DO 농도가 최대 4 mg/L까지 증가하였다. 다공질 파일 내부의 DO 농도의 증가는 저질내의 환원물질과 유기물량을 감소시키는데 효과적이었으며, 지하수의 흐름은 퇴적된 점토질 입자의 재부상을 촉진시키는 것으로 조사되었다. 이상의 결과로부터 점토질 갯벌 내에 다공질 파일을 설치함으로써 점토질 갯벌의 저질 환경을 효과적으로 개선할 수 있음을 확인하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1992년도 봄 학술발표회 논문집 깊은 기초의 연구와 실무(RESEARCH AND PRACTICE OF DEEP FOUNDATIONS)
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• pp.103-114
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• 1992

The jointing method of PC pile installation, which utilizes steel sleeve, is most popular for the deep bearing stratum( deeper than 15m ) or the irregular bearing stratum depths. However, this method has some difficulties in safety because there is no optimum standards of steel sleeve. This research attempts to determine the optimum standard of steel sleeve for 350mm PC pile, which is most widely used, through bending moment test designated by KS and numerical analysis using finite element method. According to the results, the optimum length of steel sleeve is three times longer than diameter of pile, and the thickness of steel sleeve is more than 2.5mm.

• 한국해양공학회지
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• 제18권1호
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• pp.47-52
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• 2004

Greater holding force of an anchor is required for maintaining the position of a larger floating structure. According to the series of model tests of pile anchors with movable fluke, the square type pile anchor, with fluke, showed more than 6 times of the uplift pulling force, compared to the same type pile anchor, without fluke. This uplift force is 100 times its weight. When the water depth is more than 40m, It is difficult to install the pile anchor. For a convenient installation method, a type of manipulator is proposed for the separation of a weight and buoyancy controller, using TRIZ.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 춘계 학술논문 발표대회
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• pp.155-157
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• 2013

Ground source heat pump(GSHP) systems have been attracted as high-efficient energy-saving technology, but the building clients and designers have hesitated to use GSHP systems which is a expensive initial installation and a uncertain economic feasibility. Therefore In order to reduce the initial cost, many researchers have focused on the energy-pile system using the structure of the building as a heat exchanger. Even though many of experimental studies for energy pile system have been conducted, there was not enough data of a quantitative evaluation with the economic analysis and comprehensive analysis for energy-pile. In this study, the feasibility study for the energy pile system with a barrette pile was conducted by the performance analysis and LCC assessment.