• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.299-306
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• 2001

Crushed Stone Pile(CSP) is one of the ground improvement methods available to loose sand and clayey ground by forming compacted CSP in the weak soil layer. The effects of this method are enhancement of ground bearing capacity, reduction of settlement and prevention of lateral ground movement in cohesive layer, reduction of liquefaction potential in sandy ground. This study performs model tests in 1.0m${\times}$1.0m${\times}$1.0m and 1.5m${\times}$1.5m${\times}$l.2m model tank to observe bearing capacity of CSP treated ground. The area replacement ratio of CSP composite ground varies 20%, 30% and 40% with square grid pattern. After the composite ground was consolidated under pressure of 0.5kg/$\textrm{cm}^2$ and 1.0kg/$\textrm{cm}^2$, load tests were carried out. The results show that ultimate bearing capacity increases with area replacement ratio and the preconsolidation pressure of ground.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.397-404
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• 2001

Sand pile is one of the widely used ground improvement methods. Sand pile improved ground will have composite ground effects, even though the primary purpose is the accelerated consolidation. However, the consolidation of sand pile improved ground as a composite ground is substantially under developed. This study investigate the effect of composite ground for relatively low volume displacement sand piles. Plate bearing tests and earth pressure cell measurements are performed. It turned out that the contribution of sand pile as a load bearing mechanism is not substantial. However the bearing capacity of the surrounding clayey soil is increased by sixty percent, and it cause the stiffness change during consolidation. Therefore it is expected that, the effect of increased stiffness of sand pile improved ground is influenced by change of ground stiffness.

• Journal of the Korean Geosynthetics Society
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• v.18 no.1
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• pp.91-101
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• 2019

Recently, small-scale excavation like ground cavity restoration and buried pipe replacement works are being carried out in urban area, in order to improve living convenience. This paper describes experiment results on the ground reinforcement method that can reduce the buried pipe damage, when the differential settlement occurred due to poor compaction of ground below the buried pipe. Plate load tests were conducted to evaluate a reinforcement effect of ground using concrete mat and expansion mat in the ground below the buried pipe. The results showed that the stress reduction ratio by concrete mat and expansion mat according to the surcharge load was about 46%~48% and 39%~42%, respectively. Therefore, the differential settlement of the buried pipe and the ground deformation below the buried pipes were reduced by the reinforcement effect of the concrete mat and expansion mat. This means that it is possible to prevent a buried pipe damage due to underground cavity and ground subsidence, if concrete mat and expansion mat are reinforced in the ground below the buried pipe or on the ground between the buried pipes.

• Journal of the Korean Geotechnical Society
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• v.32 no.12
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• pp.69-78
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• 2016

A suction bucket foundation has been considered to be a potential foundation type for offshore wind turbines. A suction bucket foundation is usually installed in soft soil, so the accumulated displacement of the foundation may occur under long-term cyclic loads. In this study, a series of 1-g model tests were performed to analyze the accumulated rotation of suction bucket foundations under long-term cyclic horizontal loads. The dry model ground was prepared to have two different soil densities by air-pluviation method. The model tests were performed varying the embedment depth of the suction bucket, the soil density, and the amplitude of cyclic load. A one-way horizontal cyclic load was applied over $10^4$ cycles. Test results showed that the accumulated rotation of the suction bucket foundation increased with the increase in the number of cycles and load magnitudes. Based on the model test results, a new equation was proposed to evaluate the accumulated rotation of the suction bucket foundations in dry sandy ground under long-term cyclic horizontal loads.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.83-89
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• 2018

In this study, the settlement of concrete rectangular pyramid foundation on soft ground is investigated based on a finite element analysis. considering the grounding load and the grounding area of square pyramid foundation, we compensate the insufficient design bearing capacity and investigated the effect of settlement by load. Based on this study, it is found that the rectangular pyramid foundation shows the smallest settlement of three different type of foundations. As a result of this study, it was resulted that the square pyramid foundations were more effective than the crushed stone foundations by 18%. These results show that the ground pressures of the square pyramid bases are divided into horizontal and vertical stresses, so it is analyzed that the horizontal stress builds up the rigid ground on the foundation of the structure and distributes the load widely to increase the resistance to the overhead load.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.5
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• pp.523-531
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• 2021

In general, the foundation refers to a group pile with several single piles connected by an upper structure. However, when a load is applied to pile groups, the range of stress applied to the ground is expanded and overlapped compared with the single pile, so the overall bearing capacity may decrease. This reduction ratio of bearing capacity is referred to as the efficiency of pile groups. Therefore, in this study, the soil composition, the arrangement and spacing of group piles, and the contact characteristics between the ground and piles were set as analysis variables, and the group pile efficiency and individual pile behavior were analyzed. As a result of the analysis, the efficiency of pile groups tends to converge or decrease when the friction coefficients are increased with ground type. Through this, the optimal efficiency of pile groups can be derived. In addition, through the analysis of individual piles, the load ratio of each pile was analyzed when an upper load was applied. In the case of piles located inside group piles, the load was relatively low, and this is considered to have an influence on the internal ground.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.586-589
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• 2009

This paper presents the performance of a water-to-refrigerant type ground source heat pump (GSHP) system installed in a school building in Korea. For analyzing the performance of the GSHP system, we monitored various operating conditions, including the outdoor temperature, the ground temperature, and the input power of the GSHP system. The average cooling coefficient of performance (COP) of the heat pump was found to be 8.5 at 60% partial load condition, while the overall system COP was found to be 5.9. The average heating COP of the heat pump was found to be 6.5 at 45% partial load condition, while the overall system COP was found to be 5.0.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.833-837
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• 2008

GSHP(Ground Source Heat Pump) has been extensively disseminated due to the recent increasing demand over new and renewable energy. In this study, the operating performance of rain water and ground source heat pump system (RW-GSHP) was compared with GSHP during the heating test. Leaving load temperature(LLT) was $50^{\circ}C$, $53^{\circ}C$, $56^{\circ}C$, respectively and rain water tank temperature(RWT) was $13^{\circ}C$, $15^{\circ}C$, $17^{\circ}C$ in this heating test. The experiment was focused on comparison of the system operating performance depending on leaving load temperature (LLT) and rain water tank temperature (RWT). The results showed that rain water and ground source heat pump system (RW-GSHP) was higher heating performance and COPh than those of GSHP.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.691-699
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• 2008

In the design of a foundation, settlement of the foundation may exceed allowable design criteria even with a competent bearing stratum. In such a case, a piled-raft foundation system may be adopted using piles as settlement reducing component. In this paper, Disconnected Piled Raft Foundation (DPRF) system, which installs disconnected piles underneath the raft and uses the piles as ground reinforcements, is studied as a cost effective design method against the classical piled-raft foundation system. To this end, large size loading tests were carried out on weathered ground changing area replacement ratio and length of piles. The results indicated that the settlement of the reinforced ground was reduced by 34~87% and the allowable bearing pressure increased by 70% on average from those of the unreinforced original ground, respectively. The correlating formula between the area replacement ratio and the load bearing ratio of piles were derived from the test results and numerical analysis. From the correlation, a design method determining the size and the quantity of the disconnected piles to enhance the bearing capacity of original ground to the desired value was proposed based on one inch settlement criteria.

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.35-36
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• 2012

Part load operation usually covers large periods of the total operation time on the economic ground and electricity demand in small-scale boilers. Performance analysis of part load behavior is very important for the purpose of boiler operation optimization. A simple thermal calculation approach is applied to predict performance of a pilot-scale circulating fluidized bed (CFB) boiler at part load operation. Verification has been carried out by comparing between calculation results an operation data of the boiler.