• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2343-2348
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• 2014

Main ground net of power plant is formed to protect human body from increase in potential gradient caused by grounding current during ground fault. Calculations during ground design are generally performed according to IEEE Std-80-2000 (Kepco Design Standard 2602). However, it is difficult to apply this Standard to water environment, and a grounding technology is required to secure grounding resistance of floating photovoltaic system. Therefore the aim of this paper is to investigate and analyze ground resistivity on the water surface and underwater of reservoir using Wenner 4-pin method, a general method of measuring ground resistivity. Also, grounding resistance of floating photovoltaic systems currently in operation was measured and analyzed using the voltage drop method suggested in the international standard (IEEE Std-81) to propose a grounding method for stable grounding of floating photovoltaic system. The resistivity at 1m below the surface of water ($126.3969[{\Omega}{\cdot}m]$) is mostly higher than resistivity at the river bed ($97.5713[{\Omega}{\cdot}m]$). Also the proposed grounding anchor method was determined as the most effective method of securing stable grounding resistance in floating photovoltaic systems and is expected to be utilized as a ground method for future floating photovoltaic generation systems.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.5
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• pp.453-467
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• 2012

Usage of underground space is increasing at metropolitan city. More than 90% of flood damages have occurred at downtown of metropolitan cities. In order to prevent and/or minimize the flood-induced damage, an underground rainwater detention cavern was proposed to be built underneath existing structures. As for underground caverns to be built for flood control, multi-caverns will be mostly adopted rather than one giant cavern because of stability problem. Because of the stress concentration occurring in the pillars between two adjacent caverns, the pillar-stability is the Achilles' heel in multi-caverns. So, a new pillar-reinforcing technology was proposed in this paper for securing the pillar-stability. In the new pillar-reinforcing technology, reinforced materials which are composed of a steel bar and PC strands are used by applying pressurized grouting, and then, by applying the pre-stress to the PC strands and anchor body. Therefore, this new technology has an advantage of utilizing most of the strength that the in-situ ground can exert, and not much relying on the pre-cast concrete structure. The main effect of the pressurized grouting is the increase of the ground strength and more importantly the decrease of stress concentration in the pillar; that of the pre-stress is the increase of the ground strength due to the increase of the internal pressure. In this paper, ground reinforcing effects were verified the stress change in pillar is obtained by numerical analysis at each construction stage. From these results, the effects of pressurized grouting and pre-stress are verified.