• Journal of the Korean Geotechnical Society
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• v.32 no.11
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• pp.61-72
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• 2016

For the construction of high-rise structures and the optimized foundation design, the use of the large-diameter PHC pile has increased. Especially, the use of the 600 mm diameter PHC pile has significantly increased. In this study, for the evaluation of the suitability of the current design practice, the 46 dynamic pile load tests, which were carried out in the 600 mm diameter preboring PHC pile, are analyzed. The end bearing capacity is obtained from the end of initial driving test and the shaft capacity is estimated from the restrike test. The allowable capacities estimated by the dynamic load test are compared with those based on the current design practice. The analyses show that the allowable end bearing capacity evaluated by the dynamic pile load test is greater than the design practice in most piles. The allowable shaft capacity, however, is smaller than the design practice in many piles. The higher end bearing capacity and the smaller shaft capacity may result from the improvement of the drilling equipment and the increase in the penetration depth. Thus, the portion of the end bearing capacity in the total capacity increases.

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.43-58
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• 2018

In this study, the load-transfer behavior along the shaft of the prebored and precast piles was investigated by pile loading tests. Special attention was given to quantifying the skin frictions developed between the pile-soil interfaces of the 14 instrumented test piles. Based on this detailed field tests, the load - settlement curves and axial load distributions of piles were obtained and the load-transfer curves (t-z curves) for the test piles were proposed. As such, it is found that the test results show two different load transfer behaviors; ductile and brittle behavior curves. The corresponding t-z curves are proposed based on the hyperbolic- and sawtooth-shape, respectively. By validating the accuracy of the proposed curves, it is also found that the prediction results based on the proposed load-transfer curve are in good agreement with the general trends observed by the field loading tests.

• Journal of the Korean Geotechnical Society
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• v.33 no.1
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• pp.31-38
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• 2017

Skin friction of prebored and precast pile may be one of the most critical factors affecting the bearing capacity and settlement. Special attention was given to the interface behavior of pile-cement milk-surrounding soil when the load is acting on the prebored and precast pile. The cases of single pile were analyzed through a three-dimensional finite element approach and pile loading tests. A series of numerical analyses of the interface of pile-cement milk-soil was conducted with the proposed t-z curve and field measurements. It is shown that the use of cement milk around the pile increases the skin friction and reduces the pile settlement. It is also known that the suggested t-z curve between the cement milk and the soil, enhances the accuracy of the numerical analysis results.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.189-197
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• 2002

The bearing capacity of open-ended piles is affected by the degree of soil plugging, which is quantified by the incremental filling ratio, IFR. There is not at present a design criterion for open-ended piles that explicitly considers the effect of IFR on pile load capacity. In order to investigate this effect, model pile load tests using a calibration chamber were conducted on instrumented open-ended piles. The results of these tests show that the IFR can be estimated from the plug length ratio PLR, which is defined as the ratio of soil plug length to pile penetration depth. The unit base and shaft resistances decrease with increasing IFR. Based on the results of the model pile tests, new design equations for calculating base load capacity and shaft load capacity of open-ended piles are proposed.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.131-136
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• 2006

일면전단시험은 전단면의 응력을 직접 측정하므로 평면변형시 강도를 파악할 수 있는 등의 많은 장점을 가지고 있으며, 시험조작이 간편하기 때문에 실용적으로도 우수한 것으로 판단된다. 그러나 사질토의 경우에 의한, Dilatancy에 의한 체적변화과정에서 공시체와 전단상자의 주면마찰력이 전단면의 수직 응력을 증감시키기 때문에 구해지는 강도가 과대 또는 과소하게 나타나는 것으로 알려져 있다. 그러나 반력판측에 장착한 하중계를 통해 전단면의 수직응력을 직접 측정 제어하는 형식으로 개선되어 주면마찰력의 영향을 해소하였다. 따라서 본 연구는 반력판측에 하중계를 장착한 개량형 다단식 단순전단시험기를 개발하여 사질토의 정압(CD)조건 전단시험을 수행하여 강도특성과 전단강도에 미치는 영향을 개량형 일면전단시험의 결과와 비교하였다. 그 결과 정압조건의 일면전단시험과 단순전단시험에 의한 강도정수는 조밀한 모래의 경우는 거의 비슷하게 나타나며, 느슨한 모래의 경우는 일면전단이 다소 크게 나타났다. 그리고 단순전단과 일면전단시험에서의 Dilatancy거동에는 큰 차이가 나타나지 않았다.

• Journal of the Korean Institute of Rural Architecture
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• v.23 no.3
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• pp.1-8
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• 2021

Rural multi-purpose buildings needs to ensure their safety against various disasters. Therefore, a pile foundation, which is a foundation type that can transmit the load of the structure to the bedrock layer, has been designed. The pile foundation method is largely divided into driving piles method and pre-bored pile method. Recently, in order to respond to the Noise and Vibration Control Act and related environmental complaints, construction of pile foundation adopts pre-bored pile method. The bearing capacity of the pre-bored pile method is calculated through a load test in situ. However, a disadvantage stems in that it is difficult to measure the ultimate bearing capacity due to field conditions. Therefore, in this study, the skin frictional force of pre-bored pile was measured through a model test in laboratory for each pile filling material. In result, the pile filling material with using circulating resources shows superior skin frictional force than ordinary portland cement. This study also judged that the result can be applied in place of ordinary Portland cement in the field.

• Journal of the Korean GEO-environmental Society
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• v.14 no.12
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• pp.23-30
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• 2013

Bearing capacity of pile is governed by only skin friction in frozen ground condition, while it is generally governed both by skin friction and end bearing capacity in typically unfrozen ground condition. Skin friction force, which arises from the interaction between pile and frozen soils, is defined as adfreeze bond strength, and adfreeze bond strength is one of the most important key parameters for design of pile in frozen soils. Many studies have been carried out in order to analyze adfreeze bond strength characteristics over the last fifty years. However, many studies for adfreeze bond strength have been conducted with limited circumstances, since adfreeze bond strength is sensitively affected by various influence factors such as intrinsic material properties, pile surface roughness, and externally imposed testing conditions. In this study, direct shear test is carried out inside of large-scaled freezing chamber in order to analyze the adfreeze bond strength characteristics with varying freezing temperature and normal stress. Also, the relationship between adfreeze bond strength and shear strength of the frozen soil obtained from previous study was analyzed. The coefficient of adfreeze bond strength was evaluated in order to predict adfreeze bond strength based on shear strength, and coefficients suggested from this and previous studies were compared.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.87-98
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• 2004

In this study reinforcing effect of soil nailed-drilled shafts subjected to axial and lateral loads was evaluated. Special attention was given to the reinforcing effects of soil nails placed from the drilled shafts to surrounding weathered- and soft-rocks based on model tests, numerical analyses and field tests. The model tests and numerical analyses are conducted to analyze the reinforcing effect of various conditions of number, inclination, position and length. The results of 1/40 scale model tests and numerical analyses show that as the number of reinforcing level increases, the incremental effect of reinforcement tends to increase, whereas the reinforcing effect on relative position is negligible. In addition there is a reinforcing effect as the inclination angle increase up to 30 degrees. Based on the results of tensile load tests, soil nailed-drilled shaft has a considerably smaller settlement to reach the ultimate level compared with the result of un-reinforced drilled shafts. For compression tests, there is a reinforcing effect of about 200% measured.

• Proceedings of the Korean Geotechical Society Conference
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• 1992.03a
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• pp.69-102
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• 1992

The estimation of pile bearing capacity is important since the design details are determined from the result. There are numerous ways of determining the pile design load, but only few of them are chosen in the actual design. According to the recent investigation in Korea, the formulae proposed by Meyerhof based on the SPT N values are most frequently chosen in the design stage. During construction pile driving formulae are used and sometimes the pile loading tests are performed. In this paper the three methods are studied and compared. It is concluded that except the estimation made by pile loading test, the reliability of estimation is very poor. And the analysis of pile loading test would involve serious errors unless the end bearing capacity is measured separatly from the skin friction capacity. It is thus suggested that the separate measurement of end bearing capacity and skin friction capacity is the most reliable way of determining the pile design load.

• Journal of the Korean Geotechnical Society
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• v.24 no.8
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• pp.89-97
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• 2008

A series of field tests were performed to investigate the behavior of jacket anchor and to evaluate the ultimate bond stress of jacket anchor. From twelve sets of field tests on the jacket anchor and general type ground anchor, it was observed that the pullout resistance of jacket anchor is significantly larger than that of the ground anchor and that the plastic deformation of jacket anchor is significantly smaller than that of general ground anchor at the same loading cycle. Especially in gravel layers, the jacket anchor provides more than 250% increase in ultimate resistance and more than 600% reduction in plastic deformation, compared with the general ground anchor. Finally, the relationship between the injection pressure and overburden pressure is proposed to determine the optimum injection pressure, based on additional field test results.