• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.57-64
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• 2005

Since the allowable bearing capacities of piles in weathered/fractured rock are mainly governed by settlement, the load-displacement behavior of the rock socketed pile should be well known. To predict pile head settlement at the design stage, the exact understanding of the load-transfer mechanisms is essential. Therefore, in this research, the load-transfer mechanisms of drilled shaft socketed into weathered rock was investigated. For that, 5 cast-in-place concrete piles with diameters of 1,000 mm were socketed into weathered gneiss. The static axial load tests and the load-transfer measurements were performed to examine the axial resistant behavior of the piles. A comprehensive field/laboratory testing program on weathered rock at the field test sites was also performed to describe the in situ rock mass conditions quantitatively. And then, the effect of rock mass condition on the load transfer mechanism was investigated. The side shear resistance of the pile in moderately weathered rock reached to yielding point at a few millimeter displacements, and after that, the rate of resistance increment dramatically decreased. However, that in the highly /completely weathered rock did not show the obvious yielding point, and gradually increased showing the hyperbolic pattern until with the relatively high displacement (>10 mm). The end bearing-displacement curves showed linear increase at least until with the base displacement of approximately 10 mm, regardless rock mass conditions.

• Journal of the Korean Geotechnical Society
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• v.33 no.2
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• pp.27-34
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• 2017

Various earth retaining wall methods were used on the domestic construction sites and a cast in place pile (C.I.P) method was mostly applied at deep excavation. Because of a lot of shortcomings in the C.I.P method, a new method using PHC-W earth retaining wall was developed. The earth retaining wall method using PHC-W piles has a lot of advantages including that it is safer than other earth retaining wall methods due to uniform quality and high rigidity. PHC-W was designed to effectively resist lateral earth pressure by alternating cross section of PHC pile. And increment of bending moment and shear strength were verified through KS F 4306 tests, and were increased by 42% and 98% more than KS standards.

• Journal of the Korean Geosynthetics Society
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• v.15 no.1
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• pp.21-35
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• 2016

It is a current trend that the concrete track is applied for high speed railway. In the case of the railway embankment constructed on soft ground, the damage to concrete track which is sensitive to settlement such as distortion and deflection could be caused by very small amount of long term settlement. Pile Supported Embankment method can be considered as the effective method to control the residual settlement of the railway embankment on soft ground. The Geosynthetics is used inside of the embankment to maximize the arching effect transmitting the load of the embankment to the top of the piles. But, PHC piles that are generally used for bridge structures are also applied as the pile supporting the load of embankment concentrated by the effect of the Geosynthetics. That is very low efficiency in respect of pile material. So, in this study, the cast in place concrete pile was selected as the most suitable pile type for supporting the embankment by a case study and the optimum mixing condition of concrete using a by-product of industry was induced by performing the mixing designs and the compressive strength designs. And it is shown that the cast in place pile with the optimum mixing condition using the by-product of industry is 2.8 times more efficient than the PHC pile for the purpose of Pile Supported Embankment by the finite element analysis method.

• Journal of the Korean Geotechnical Society
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• v.31 no.5
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• pp.5-21
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• 2015

An energy pile is a novel type of ground heat exchangers (GHEX's) which sets up heat exchange pipes inside a pile foundation, and allows to circulate a working fluid through the pipe for exchanging thermal energy with the surrounding ground stratum. Using existing foundation structure, the energy pile can function not only as a structural foundation but also as a GHEX. In this paper, six full-scale energy piles were constructed in a test bed with various configurations of the heat exchange pipe inside large-diameter cast-in-place piles, that is, three parallel U-type heat exchangers (5, 8 and 10 pairs), two coil type heat exchangers (with a 500 mm and 200 mm pitch), and one S-type heat exchanger. During constructing the energy piles, the constructability of each energy pile was evaluated with consideration of the installation time, the number of workers and any difficulty for installing. In order to evaluate the thermal performance of energy piles, the thermal performance tests were carried out by applying intermittent (8 hours operating-16 hours pause) artificial cooling operation to simulate a cooling load for commercial buildings. Through the thermal performance tests, the heat exchange rates of the six energy piles were evaluated in terms of the heat exchange amount normalized with the length of energy pile and/or the length of heat exchange pipe. Finally, the economic feasibility of energy pile was evaluated according to the various types of heat exchange pipe by calculating demanded expenses per 1 W/m based on the thermal performance test results along with the market value of heat exchange pipes and labor cost.

• Journal of the Korean Geotechnical Society
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• v.40 no.2
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• pp.41-53
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• 2024

Micropiles are small, cast-in-place piles with a diameter of 300 mm or less, primarily used to reinforce existing structures and support new constructions. As the application of these piles has expanded, extensive research has been conducted on their bearing characteristics, particularly in micropiled rafts. These studies have consistently demonstrated the positive impact of micropiles on foundation reinforcement. However, previous research often overlooked the potential variations in behavior between micropiled and conventional piled rafts based on different pile conditions. Furthermore, the influence of the cohesive characteristics of the soil layer beneath the foundation on the reinforcing effect of the micropiles has not been adequately addressed. This study, therefore, undertook 3D numerical analysis to assess the reinforcing effect of micropiles, considering both pile conditions and the cohesive characteristics of the soil layer beneath the foundation. The findings revealed that micropiles are significantly more effective in non-cohesive soil layers compared to cohesive ones, with the potential to increase the bearing capacity of the raft by up to 3.7 times.

• Journal of the Korea Institute of Building Construction
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• v.12 no.2
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• pp.230-242
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• 2012

Recently the Permanent Uni-wall System (PUS) has been developed which improved the disadvantage of the Cast-In-Place Concrete Pile (CIP) and could be used as permanent retaining wall. In this study, joints between PUS and floor systems were developed. From analyses of the characteristics of design and construction of PUS, shear friction reinforcements with couplers were adopted for shear design of the joints. Twelve types of joints were developed which were classified according to the types of floor structures, wale, and piles of PUS. Two typical joints were tested and the joints showed satisfactory behaviors on the points of shear strength, stiffness, and serviceability. Especially the shear strengths were much higher than the design strengths due to the shear keys which were by-products in splicing shear reinforcements. However, the shear strength of the joint is recommended to be designed by only shear friction reinforcement because shear key is not reliable and too brittle.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.2
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• pp.120-127
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• 2013

Vam Cong Cable Stayed Bridge which has 450m main span length is one of the Central Mekong Delta Region Connectivity Project and is located in Cuu Long Delta Region. It has steel-concrete composite girder with 4 lane and the type of cable is multi strand cable. The improved H-shape pylon and cast-in-place bored piles were applied. High strength concrete is applied for pylon, precast concrete slab and Cast-in-Situ concrete pile to ensure the structural safety. The present paper describe the design specifications and main features of Vam Cong Cable Stayed Bridge design.

• Journal of the Korean Geotechnical Society
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• v.21 no.5
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• pp.187-196
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• 2005

Since the allowable bearing capacities of piles in weathered/fractured rock are mainly governed by settlement, the load-displacement behavior of pile should be known accurately. To predict pile head settlement at the design stage, the exact understanding of the load-transfer mechanisms is essential. Therefore, in this research, the load-transfer mechanism of drilled shaft socketed into weathered rock was investigated. For the investigation, five cast-in-place concrete piles with diameters of 1,000 mm were socketed into weathered gneiss. The static axial load tests and the load-transfer measurements were performed to examine the axial resistant behavior of the piles. A comprehensive field/laboratory testing program on weathered rock at the Held test sites was also performed to describe the in situ rock mass conditions quantitatively. And then, the effect of rock mass condition on the load transfer mechanism was investigated. The f-w (side shear resistance-displacement) curve of the pile in moderately weathered rock reached to yielding point at a for millimeter displacements, and after yielding point, the rate of resistance increment dramatically decreased. However, the f-w curve in the highly/completely weathered rock did not show the obvious yielding point, and the resistance gradually increased showing the hyperbolic pattern until relatively high displacement (>15 mm). The q-w (end bearing resistance-displacement) curves showed linear response at least until the base displacement of approximately 10 mm, regardless of rock mass conditions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4C
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• pp.205-212
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• 2008

In this research, the effect of rock mass weathering on the side shear resistance of drilled shaft socketed into igneous-metamorphic rock was investigated. For that, 23 cast-in-place concrete piles with diameters varying from 400mm to 1,500mm were constructed at four different sites, and the static axial load tests were performed to examine the resistant behavior of the piles. A comprehensive field/laboratory testing program at the field test site was also performed to describe the in situ rock mass conditions quantitatively. The side shear resistance of rock socketed piles was found to have no intimate correlation with the compressive strength of the intact rock. However, the global rock mass strength, which was calculated by the Hoek and Brown criteria, was found to closely correlate to the side shear resistance. The ground investigation data regarding the rock mass conditions (e.g. $E_m$, $E_{ur}$, $p_{lm}$, RMR, RQD, j) were also found to be highly correlated with the side shear resistance, showing the coefficients of correlation greater than 0.75 in most cases. Additionally, the applicability of existing methods for the side shear resistance of weathered granite-gneiss was verified by comparison with the field test data. The existing methods which consider the effect of rock mass condition were modified and/or extended for weathered rock mass where mass factor j is lower than 0.15, and RQD is below 50%.

• Journal of the Korean Geosynthetics Society
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• v.19 no.1
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• pp.83-91
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• 2020

In this study, the characteristics of support behavior according to the change of ground condition of the cast-in-place pile and the large Caisson foundation, which are increasingly used as foundations of large structures and bridges. the allowable bearing capacity calculated using the yield load analysis method was analyzed to calculate similar allowable bearing capacity for each method. In addition, the allowable bearing capacity calculated by the ultimate load analysis method was found to have a large difference in bearing capacity for each method. Through this point, it can be usefully used as an empirical formula for evaluating the settlement characteristics of piles in future design and construction. In addition, as a result of examining the ground force distribution during sedimentation of large caissons, the section of the weathered rock layer showed almost constant ground force distribution as ground forces decreased after yield occurred at the base corner. And in the bed rock layer section, the foundation's center was transformed into a ground force in the form of a convex downward due to an increase in the ground resistance of the central part. Using these results, the theory previously presented by Fang (1991) and Kőgler (1936) was proved.