• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.206-210
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• 2012

Ground source heat pump is a central heating and cooling system that pumps heat to or from the ground. Building Integrated Geothermal system used in this experiment is one of the Ground Source Heat Pump Systems which utilize energy pile. The purpose of this study is to evaluate heating performance of the system. The building is a low-energy experiment apartment in Yonsei University Songdo Campus and the subject is one of the energy reduced houses in this apartment. In the experiment, indoor temperature, outdoor temperature and the inlet and outlet temperature of ground heat exchanger and subject model, were measured. Then the heat pump's Coefficient of performance(COP) of the heat pump was calculated. As a result, the COP of heat pump is 4-5. Although the depth of the ground heat exchanger in this experiment is shallower than usual heat exchanger, the result of heating performance of this system was good as well.

• Journal of the Korean Geosynthetics Society
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• v.10 no.3
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• pp.9-18
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• 2011

This paper presents shear characteristics of a ground improved by sand piles. The sand piles have different length and diameter depending on the depth of a clayey layer. A series of CU triaxial compression tests are carried out on specimens covered with/without soft material which is similar to geotextile. The results show that the shear strength and stress ration increase as the length and the diameter of the sand pile increase. In addition, covering the specimen with the soft material appears to affect those characteristics as well. The increase of cohesion seems to be more remarkable compared to internal frictional angle.

• Journal of the Korean Geophysical Society
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• v.8 no.2
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• pp.53-61
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• 2005

2-D and 3-D resistivity surveys were carried out at the Deok-In2 levee during the period of arid and rainy seasons to assess the waterproof effectiveness of sheet pile and routing sections and detect the location of pipings. Inverted resistivity sections clearly indicated the boundaries of sheet pile and grouting sections and the locations of pipings observed at the ground surface. It is necessary that proper survey parameters are determined considering inverted depth and resolution and contacting resistance is decreased to obtain favorable result.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.899-904
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• 2009

This paper presents the analysis result of load-transfer mechanism and pile movements associated with the development of frictional resistance to understand the engineering characteristics of micropile behavior. An field load tests were performed for two different types of micropiles and they are (i) thread bar reinforcement with D=50mm and (ii) hollow steel pipe reinforcement with $D_{out}$=82.5mm and $D_{in}$=60.5mm and wrapped with woven geotextile for post-grouting. The load test results indicated that micropiling with pressured grouting provided better load-transfer characteristics than micropiling with gravity grouting under both compressive and tensile loading conditions in that unit skin frictional resistance is well distributed along installation depth. The unit weight and unconfined compressive strength of cured grout were obtained for each piling method. The strength and unit weight of micropile with pressured grouting was higher than those with gravity grouting. The fact that load bearing quality with pressured grouting is better than that of gravity grouting could be attributed to the dense mutual adhesion between surrounding ground and pile due to pressurized grouting method and better grout quality.

• Journal of the Korean Society for Marine Environment & Energy
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• v.7 no.2
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• pp.82-88
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• 2004

To evaluate the tidal flow around the transmission type harbour structures, the numerical models considering hydraulic resistance are used. The traditional governing equations of depth-integratef hydrodynamics are modified by using of the drag force term. As a numerical model to evaluate the rate of tidal exchange, the Random-walk method is used. The models are applied in a design of the pile-supported pier structures in Busan harbour site, Korea, where the flow speed and the tidal exchange are more promotive than the case of non-transmission structure. The developed model will be applied usefully to design the transmission type structure in the ocean space.

• Journal of the Korean Geosynthetics Society
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• v.18 no.1
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• pp.1-9
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• 2019

This study investigated settlement and scouring characteristics of artificial reef reinforced with various reinforcement types to reduce settlement and scouring. Three reinforcement types were prepared: geogrid, geogrid-bamboo mat (GBM) and seaweed-pile mat (SPM). Various laboratory tests such as bearing capacity test, large size settlement test, two-dimensional flow scour test were performed according to different soil types (sand, silt, clay). Laboratory test results indicated that bearing capacity of seabed with a reinforced artificial reef increased and its settlement and scour depth reduced for all reinforcement types. Especially, reinforcement effect tends to be greater in clay soft ground rather than sand and silt grounds.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.1
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• pp.31-36
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• 2022

This paper presents the measuring process of dynamic properties of offshore wind power foundation and provides consideration of each step. This Guideline enables to maintain consistent measuring procedure and therefore increase the reliability of test results. Small scaled suction bucket foundation was fabricated to represent the commercial support structure installation mechanism and two cases(free-free, free-fixed) of dynamic tests were performed at workshop. From the tests, the importance of dynamic properties of connection part between suction bucket and tower was figured out. More over, types and configuration of measuring devices are recommended which can help find the natural frequency of wind turbine foundation correctly. In field test, it was found that the natural frequency of suction bucket foundation was increased linearly with the penetration depth due to the confining effect of ambient soil. Meanwhile, it was not easy to get an enough excitation force with normal impact hammer because the N.F of suction bucket model was in the lower range of 0 Hz ~ 5 Hz. Therefore, new excitation method which has enough force and can excite lower frequency range was devised. This study will help develop safety check procedure of suction bucket foundation in field at each installation stage using the N.F measurement.

• Structural Engineering and Mechanics
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• v.84 no.6
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• pp.743-765
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• 2022

Near-surface excavations may cause the tilting and destruction of the adjacent superstructures in big cities. The stability of a huge excavation and its nearby superstructures was studied in this paper. Some test instruments monitored the deformation and loads at the designed location. Then the numerical models of the excavation were made in FLAC3D (a three-dimensional finite difference code) and Plaxis-3D (a three-dimensional finite element code). The effects of different supporting and reinforcement tools such as nails, piles, and shotcretes on the stability and bearing capacity of the foundation were analyzed through different numerical models. The numerically approximated results were compared with the corresponding in-field monitored results and reasonable compatibility was obtained. It was concluded that the displacement in excavation and the settlement of the nearby superstructure increases gradually as the depth of excavation rises. The effects of support and reinforcements were also observed and modeled in this study. The settlement of the structure gradually decreased as the supports were installed. These analyses showed that the pile significantly increased the bearing capacity and decreased the settlement of the superstructure. As a whole, the monitoring and numerical simulation results were in good consistency with one another in this practically important project.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.361-375
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• 2015

An energy pile is one of the novel ground heat exchangers (GHEX's) that is a economical alternative to the conventional closed-loop vertical GHEX. The combined system of both a structural foundation and a GHEX contains a heat exchange pipe inside the pile foundation and allows a working fluid circulating through the pipe, inducing heat exchange with the ground formation. In this paper, a group of energy piles equipped with parallel U-type (5, 8 and 10 pairs) heat exchange pipes was constructed in a test-bed by fabricating in large-diameter cast-in-place concrete piles. In addition, a closed-loop vertical GHEX with 30m depth was constructed nearby to conduct in-situ thermal response tests (TRTs) and to compare with the thermal performance of the cast-in-place energy piles. A series of thermal performance tests was carried out with application of an artificial cooling and heating load to evaluate the heat exchange rate of energy piles. The applicability of cast-in-place energy piles was evaluated by comparing the relative heat exchange efficiency and heat exchange rate with preceding studies. Finally, it is concluded that the cast-in-place energy piles constructed in the test-bed demonstrate effective and stable thermal performance compared with the other types of GHEX.

• 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.