• Geomechanics and Engineering
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• 제23권6호
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• pp.523-533
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• 2020

The current study focuses on the effect of the end shape of steel pipe piles on installation effort and bearing resistance using the pressing method of installation under dense ground conditions. The effect of pile rotation on the installation effort and bearing resistance is also investigated. The model steel piles with a flat end, cone end and cutting-edge end were used in this study. The test results indicated that cone end pile with the pressing method of installation required the least installation effort (load) and showed higher ultimate resistance than flat and cutting-edge end piles. However, pressing and rotation during cutting-edge end pile installation considerably reduces the installation effort (load and torque) if pile penetration in one rotation equal to the cutting-edge depth. Inclusion of rotation during pile installation reduces the ultimate bearing resistance. However, if penetration of the cutting-edge end pile equal to the cutting-edge depth in one rotation, the reduction in ultimate resistance can be minimized. In comparing the cone and cutting-edge end piles installed with pressing and rotation, the least installation effort is observed in the cutting-edge end pile installed with penetration rate equal to the cutting-edge depth per rotation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.1303-1311
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• 2006

Most of the piles are designed as group piles. In certain geotechnical environments, the installation of group piles causes heaving of the already installed piles. The unfavorable effects of pile heaving on pile bearing capacity have been well known to field engineers. However not many engineers pay enough attention to this subject. According to our recent researches, not only the bearing capacity but also the pile material could be seriously damaged due to the installation of nearby piles, especially with the cases of precast concrete piles. When the pull-out force due to installation of neighboring piles acting on the already installed precast concrete pile exceeds the shaft friction, pile heaving occurs. At the same time, if the pull-out force exceeds the allowable tensile strength of the precast concrete pile, tensile failure is inevitable, which is critical for the pile integrity. In other cases the pile material was not damaged but serious relaxation occurred as the results of pile heaving. In this paper, the pull-out mechanism due to the installation of group piles is explained.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.922-927
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• 2004

The bending moment and settlement of the slab track can be reduced by the installation of small numbers of micro piles beneath the track. This paper presents the effect of micro pile installation on the reduction of bending moment and settlement of slab track, estimated by a numerical method. The slab track is modeled as a plate based on the Mindlin's plate theory, and soil and piles are modeled as Winkler and coupled springs, respectively. The stiffness of piles is obtained by the approximate analytical method proposed by Randolph and Wroth. and the modulus of subgrade reaction is adopted to evaluate Winkler spring constant. From the analysis results, the effect of the micro pile installation is significant to considerably reduce the settlement of slab track. However, for the proper reduction of bending moments in a slab track, the pile arrangement should be reasonably taken into account to prevent the stress concentration at pile location.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 가을 학술발표회 논문집
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• pp.381-388
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• 1999

The existing methods for installation of long steel pipe pile have some uneconomical problems such as increase of installation cost and period due to the welding of two piles and removal of soil plug, and decrease of driving efficiency due to the increase of driving resistance by time effect during the welding of piles and removal of soil plug, etc. Thus, in this study, new installation method for long steel pipe pile is suggested to work out the existing problems, and calibration chamber tests are peformed to investigate both driving and economical efficiency for the suggested method. The test results showed that the new installation method has increase bearing capacity as well as reduce installation cost and period for long steel pipe piles as compared with existing methods.

• 한국지반공학회논문집
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• 제32권3호
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• pp.39-47
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• 2016

본 연구에서는 말뚝 설치 방법에 따른 동적 p-y 곡선의 차이를 분석하기 위하여, 1g 상태에서 지반 조성 전 설치한 말뚝과 지반 조성이 완료된 후에 1g 상태에서 압입하여 설치한 말뚝, 그리고 40g의 원심 가속도 조건에서 압입시킨 말뚝에 대해 동적 원심모형 실험을 수행하였다. 실험 결과로부터 얻은 각 모형 말뚝의 동적 p-y 곡선의 최대지반반력을 이용하여 동적 p-y 중추곡선(Backbone curve)을 쌍곡선 함수로 나타내었다. 말뚝 설치 방법에 따른 동적 p-y 중추곡선 분석 결과, 40g 조건에서 압입한 말뚝이 1g 상태에서 압입한 말뚝 및 지반 조성 전 설치 말뚝에 비해 말뚝에 작용하는 지반반력이 크게 평가되었으며, 이러한 지반반력의 차이는 깊이가 깊어질수록 작아지는 것으로 나타났다. 일련의 p-y 곡선 결과를 바탕으로 기존에 제안된 현장타설말뚝에 대한 동적 p-y 중추곡선의 적용성을 평가하고, 이를 수정한 압입 및 항타 말뚝에 대한 동적 p-y 곡선 산정식을 개발하였다.

• 한국지반공학회논문집
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• 제21권10호
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• pp.73-83
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• 2005

최근 사용이 증대되고 있는 말뚝지지 전면기초(piled raft foundation) 개념의 기초 설계에서는 지지력을 증대시키기 위한 목적 보다는 주로 침하를 감소시킬 목적으로 말뚝이 사용된다. 콘크리트궤도가 연약한 지반에 설치되는 경우에는 일반적으로 지지력 측면에서의 문제는 없으나, 과도한 침하가 발생할 수 있다. 이 경우 소수의 소구경 말뚝을 궤도하부에 적절히 배치하여 설치하면 침하를 효과적으로 감소시킬 수 있을 것으로 예측된다. 본 논문에서는 말뚝 설치로 인한 콘크리트궤도의 침하감소 효과를 수치해석을 통해 평가하였다. 3차원 유한차분해석법을 이용하여 말뚝이 설치된 콘크리트궤도를 모델링 하였으며, 지반 강성과 말뚝 배치의 변화에 따른 침하량 감소 효과의 차이를 분석하였다. 해석 결과로 부터 말뚝설치를 통해 콘크리트궤도의 침하를 효과적으로 감소시킬 수 있는 것을 확인하였으며, 경제적인 설계를 위한 지반조건에 따른 합리적인 말뚝 열수와 간격을 제시하였다. 또한, 지반 조건과 말뚝 배치의 변화에 따른 말뚝의 하중분담 특성을 분석함으로써, 콘크리트궤도 하부에 설치된 말뚝의 지지 메커니즘을 파악하였다.

• Geomechanics and Engineering
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• 제33권1호
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• pp.91-99
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• 2023

To test the effect of various pile tip shape series of model scale loading tests were carried out on test piles with special pile tips. Special pile tips were made using the 3D printer and were attached to the bottom end of the test pile for loading tests. The pile tips were made to have 30°, 45°, 60° inclined tips, as well as a rounded tip. The main objective of the test was to observe the effect of various pile tip shapes on settlement and penetrability of the pile. Moreover, a numerical model simulating the pile loading test carried out in this study was established and verified based on the loading test results. From this, the stress concentration around the pile tip was investigated. This will allow us to analyze the decrease of stress concentration around the pile tip which is the main cause of the pile tip damage during pile installation. However, modifying the pile tip shape will eventually increase the settlement of the pile. By estimating the degree of increase in pile settlement, the viability and the efficiency of the pile shape modification was judged. In addition, case studies on the effect of different pile tip shape and ground conditions on pile settlement and stress dispersion was conducted.

• 한국지반공학회논문집
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• 제16권1호
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• pp.235-241
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• 2000

기존의 장대강관말뚝 공법들은 말뚝의 용접이음이나 관내토의 제거 작업으로 인하여 공비와 공기가 증가하고 이들 작업이 진행되는 동안 시간효과에 의하여 말뚝의 관입 저항이 증가하여 타입이 어려워지는 등 각종 비경제적인 문제점들을 갖고 있다. 이러한 문제들을 해결하기 위하여 본 연구에서는 새로운 장대강관말뚝 공법을 제안하였으며, 제안된 공법의 시공성과 경제성을 분석하기 위하여 모형말뚝시험을 행하였다. 시험결과 새로 제안된 장대말뚝공법은 기존 공법에 비해 공기와 공비는 절감되고 지지력은 증가시키는 것으로 나타났다.

• Geomechanics and Engineering
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• 제33권4호
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• pp.415-425
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• 2023

Pile-supported wharves, port structures that support the upper deck, are installed on sloping ground. The sloping ground should be covered with a rubble mound or artificial blocks to protect the interior material from erosion caused by wave force. The behavior of the pile may vary during an earthquake if a rubble mound is installed on the slope. However, studies evaluating the effect of rubble mound on the pile during an earthquake are limited. Here, we performed dynamic centrifuge model tests to evaluate the dynamic behavior of piles installed in a slope reinforced with rubble mound. In the structure, some sections (single-pile, 2×2 group-pile) were selected for the experiment. The moment of the group-pile decreased by up to 26% upon installation of the rubble mound, whereas the moment of the single-pile increased by up to 41%, thus demonstrating conflicting results.

• Geomechanics and Engineering
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• 제23권2호
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• pp.139-149
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• 2020

Piles are widely used in structural foundations of engineering projects. However, the deformation of the soil around the pile caused by driving process has an adverse effect on adjacent existing underground buildings. Many previous studies have addressed related problems in sand and saturated clay. Nevertheless, the failure mechanism of pile driving in unsaturated soil remains scarcely reported, and this issue needs to be studied. In this study, a modeling test system based on particle image velocimetry (PIV) was developed for studying deformation characteristics of pile driving in unsaturated silt with different water contents. Meanwhile, a series of direct shear tests and soil-water characteristic curve (SWCC) tests also were conducted. The test results show that the displacement field shows an apparent squeezing effect under the pile end. The installation pressure and displacement field characteristics are sensitive to the water content. The installation pressure is the largest and the total displacement field is the smallest, for specimens compacted at water content of 11.5%. These observations can be reasonably interpreted according to the relevant unsaturated silt theory derived from SWCC tests and direct shear tests. The variation characteristics of the soil displacement field reflect the macroscopic mechanical properties of the soil around the pile.