• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.476-481
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• 2009

Bi-directional load test is one of O-cell tests. The O-cell test is a system which may be used for performing static load tests on cast in situ reinforced concrete bored piles. The technique was devised and developed by Osterberg of Northwestern University(USA) and has been in use around the world. The principle of the method is that an O-cell is installed in a cast in situ bored pile base. Once the pile concrete reaches its design strength the cell is connected to an hydraulic pump and pressured. Pressurization causes the cell to expand, developing an upward force on the section of pile above the cell loads, pile movements and strains within the pile then enable the capacity of the pile and its load settlement curves to be ascertained. The O-cell pile load test with variable end plate is operated on second steps - the first step is to confirming end bearing capacity with variable end plate and the second step is similar to the conventional O-cell test. In the study, To calculate ultimate capacity of bi-directional load test using model with the pile with variable end plate O-cell.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2007년 가을학술발표회
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• pp.90-104
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• 2007

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 and the preference of landmark. For this reason, it is definitely required to extend pile diameter and install the pilein deep foundation to support superstructure. The pile 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 Bored Pile method has applied to minimize those problems. As above shown, this article will be presented construction case study of Barrette Pile and R.C.D in order to make a counterproposal for the quality control of a large building foundation work.

• Geomechanics and Engineering
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• 제37권2호
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• pp.97-107
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• 2024

The accurate prediction of grouting upward diffusion height is crucial for estimating the bearing capacity of tip-grouted piles. Borehole construction during the installation of bored piles induces soil unloading, resulting in both radial stress loss in the surrounding soil and an impact on grouting fluid diffusion. In this study, a modified model is developed for predicting grout diffusion height. This model incorporates the classical rheological equation of power-law cement grout and the cavity reverse expansion model to account for different degrees of unloading. A series of single-pile tip grouting and static load tests are conducted with varying initial grouting pressures. The test results demonstrate a significant effect of vertical grout diffusion on improving pile lateral friction resistance and bearing capacity. Increasing the grouting pressure leads to an increase in the vertical height of the grout. A comparison between the predicted values using the proposed model and the actual measured results reveals a model error ranging from -12.3% to 8.0%. Parametric analysis shows that grout diffusion height increases with an increase in the degree of unloading, with a more pronounced effect observed at higher grouting pressures. Two case studies are presented to verify the applicability of the proposed model. Field measurements of grout diffusion height correspond to unloading ratios of 0.68 and 0.71, respectively, as predicted by the model. Neglecting the unloading effect would result in a conservative estimate.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.521-532
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• 2008

The SIP method developed by low noise-vibration from Japan is appropriate to the construction at urban area. However, this method has been misused as a pre-driiled driven pile method in Korea. Hence, Korea Expressway Corporation proposed 'Design & Construction Guideline for the SIP Method' following the original concept of the SIP method at 2004 and 2006. Also construction guideline of another auger-drilled piles were introduced.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1994년도 가을 학술발표회 논문집
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• pp.1-59
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• 1994

The design and construction of strutted and anchored sheet pile walls in soft clay are reviewed based on experience gained mainly in Singapore during the last 10years where mainly strutted sheet pile walls diaphragm walls, and contiguous bored piles are used. It is important to consider in the design the high lateral earth pressures acting on the sheet piles below the bottom of the excavation when the depth of the excavation is large compared with the shear strength of the clay. The strut loads and the maximum bending moment in the sheet piles can in that case be much higher than indicated by a conventional analysis. Different methods to increase the stability have been investigated. With jet grouting, embankment piles and excavation under water it is possible to reduce significantly the maximum bending moment, the strut loads, and the settlements outside the excavated area as well as the heave within the excavation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 추계 학술발표회
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• pp.539-550
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• 2006

New Songdo city is currently developing on the reclaimed land on a marine deposit and among the development the four sixty-four(64) stories high rise buildings are under construction at block 125. The ground condition of the site is comprised of a deep seated weathered rock staratum under a soft marine deposit layer. As a foundation system, a bored pile was planned to transmit the applied load to the stable layer. In this study, the behavior of the weathered rock especially locating at a upper part having a weak strength(HWR, MWR) has been evaluated through series of hi-directional pile load test(BD PLT) carried out on the 3 drilled shafts socketed in a weathered rock layer in a design stage. It has been planned to increase the effect of the tests that the length of test piles was prepared short enough to perform the test under a high stress. The summary of the design reflecting the test results has been made up. In addition, the 4 hi-directional pile tests excuted on the working piles during the construction stage for the purpose of confirmation and the evaluation of the adequacy of the pile behaviors have been included in this study.

• 한국지반신소재학회논문집
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• 제18권3호
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• pp.45-53
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• 2019

본 연구에서는 건축기초에 적용된 매입 PHC말뚝의 설계사례를 분석하였다. 전반적인 말뚝길이는 최대 35m 이내에서 다양하나, 지지층 조건에 따른 평균 길이는 17.0~18.9m로 큰 차이가 없었다. 지지층 소켓길이는 전체의 약 58%가 시방기준 최소길이인 1m에 따라 설계되었고, 최대 5m까지 설계되었다. 설계효율은 그 편차가 매우 크나 평균 약 70%로서 통상 알려진 범위와 일치하였다. 설계효율이 낮은 용도는 주로 설계하중이 적은 저층건물이나 놀이기구 기초 등으로 나타났다. 풍화암 지지층에서 설계하중은 설계를 지배하는 지반 허용지지력의 65~97%, 허용지지력에 대한 말뚝 허용축하중의 비는 36~115%로 광범위하게 분포하므로 설계효율과 함께 최적화 노력이 요구된다. 반면, 연 경암 지지층의 허용지지력은 대부분 말뚝 허용축하중의 90% 내외로 매우 균등했다. 설계 허용지지력은 선단지지력이 평균 75% 이상을 차지하였으나, 현장재하시험 연구결과를 보면 초기항타 조건에서는 선단지지력이 지배적이며, 재항타 조건에서는 선단지지력이 최소 25%에 불과한 경우도 있었다. 따라서, 설계시 산정된 허용지지력은 시공 초기조건만을 반영하는 것이며, 시간이 경과할수록 말뚝 주면부로의 하중전이가 증가하고, 일부는 시험시 타격에너지 부족으로 선단지지력의 확인이 이루어지지 못한다고 볼 수 있다. 균질한 지반으로 가정했을 때 근입비가 증가할수록 허용축하중이 감소하는 경향이 있었고, 이와 유사하게 지반의 허용지지력도 감소하는 경향을 보여, 큰 설계하중으로 초고강도 말뚝을 적용할 경우 지반의 지지력을 최대한 활용할 수 있음을 알 수 있었다.

• 토지주택연구
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• 제4권3호
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• pp.279-286
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• 2013

기성 말뚝을 항타시공하는 방법은 시공비가 적게 들면서도 우수한 지지력을 얻을 수 있는 효율적인 시공방법이다. 하지만 국내와 같이 매립층이 많고 다양한 지반조건에서는 예상치 못한 문제로 인하여 기계적 굴착이 수반되는 매입공법으로 변경되기도 한다. 따라서, 항타공법이 매입말뚝에 비하여 불확실성이 더 높을 수 있다. 본 논문에서는 국내에서 건축물의 기초로 사용되고 있는 PHC 항타말뚝의 불확실성 요인을 줄여주고 보다 신뢰성 있는 설계가 가능하도록 하기 위하여 한계상태설계법의 일종인 하중저항계수법(LRFD) 설계정수를 산정하였다. PHC 항타말뚝의 LRFD 설계정수를 제안하기 위해 총 221회(초기동재하 : 93회, 재항타동재하 : 128회)의 동재하시험자료와 이들 말뚝에 대한 지지력 설계(Meyerhof 설계법, SPT-CPT 전환 설계법) 자료를 분석하고 목표 신뢰도 지수 2.33과 3.0에 대해 하중저항계수를 제시하였다. PHC 항타말뚝의 저항계수는 목표 신뢰도 지수에 따라 Meyerhof 방법, SPT-CPT 전환법은 각각 0.43~0.55 및 0.40~0.49를 나타내었다.

• 대한토목학회논문집
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• 제5권2호
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• pp.11-18
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• 1985

주열식(柱列式) 흙막이벽(壁)은 저진동(低振動), 저소음(低騷音)의 이점(利點)이 있고 주변지반(周邊地盤)이나 인접구조물(隣接構造物)에 미치는 악영향(惡影響)이 적은 이유로 인하여 굴착공사(工事)의 흙막이공(工)으로 많이 채택된다. 이러한 주열식(柱列式) 흙막이벽용(壁用) 말뚝의 합리적(合理的) 설계법(設計法)을 확립(確立)시킬 것을 목적(目的)으로 본논문(本論文)에서는 말뚝의 저항력(低抗力) 산정이론식(算定理論式)이 먼저 유도(誘導)된 후 말뚝설치간격비(設置間隔比)의 결정법(決定法)도 설정(設定)된다. 본(本) 저항력(抵抗力) 산정이론식(算定理論式)의 유도(誘導) 시(時)에는 말뚝 사이 지반(地盤) Arching 현상(現象)이 취급(取扱)되므로써, 지반(地盤) 특성(特性)과 말뚝의 설치상태(設置狀態)가 처음부터 합리적(合理的)으로 고려(考慮)된다. 한편, 본논문(本論文)에서 설정(設定)된 말뚝설치간격비(設置間隔比)의 결정법(決定法)에 의거하면, 말뚝의 설치간격(設置間隔)이 Peck의 안정수(安定數), 지반의 측압계수(側壓係數) 및 내부마찰각(內部摩擦角)으로부터 산정(算定)될 수 있다. 마지막으로 굴착깊이, 말뚝직경(直徑), 말뚝설치간격(設置間隔), 말뚝근입장(根入長) 및 말뚝강성(剛性)을 체계적(體系的)으로 선정(選定)할 수있는 설계법(設計法)이 제안(提案)된다.

• Geomechanics and Engineering
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• 제34권4호
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• pp.397-408
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• 2023

Pipe pile walls are commonly used as retaining structures for excavation projects, particularly in densely populated coastal cities such as Hong Kong. Pipe pile walls are preferred in reclaimed land due to their cost-effectiveness and convenience for installation. However, the pre-bored piling techniques used to install pipe piles can cause significant ground disturbance, posing risks to nearby sensitive structures. This study reports a well-documented case history in a reclamation site, and it was found that pipe piling could induce ground settlement of up to 100 mm. Statutory design submissions in Hong Kong typically specify a ground settlement alarm level of 10 mm, which is significantly lower than the actual settlement observed in this study. In addition, lateral soil movement of approximately 70 mm was detected in the marine deposit. The lateral soil displacement in the marine deposit was found to be up to 3.4 and 3.1 times that of sand fill and CDG, respectively, mainly due to the relatively low stiffness of the marine deposit. Based on the monitoring data and site-investigation data, a 3D numerical analysis was established to back-analyze soil movements due to the installation of the pipe pile wall. The comparison between measured and computed results indicates that the equivalent ground loss ratio is 20%, 40%, and 20% for the fill, marine deposit and CDG, respectively. The maximum ground settlement increases with an increase in the ground loss ratio of the marine deposit, whereas the associated influence radius remains stationary at 1.2 times the pipe pile wall depth (H). The maximum ground settlement increases rapidly when the thickness of marine deposit is less than 0.32H, particularly for the ground loss ratio of larger than 40%. This study provides new insights into the pipe piling construction in reclamation sites.