• The Journal of Engineering Geology
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• v.20 no.1
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• pp.25-33
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• 2010

Most of contaminated groundwater in the study area was contaminated by $NO_3-N$ due to inflow of contaminated shallow surface groundwater inflow into groundwater well. Poor grouting and teared screen have increased contaminated shallow surface groundwater inflow into groundwater well. Contaminated shallow surface groundwater was inflowed into groundwater well throughout faults, joints and fracture zone of ESE-WNW, NNW, NW-SE and NS direction. The objective of this paper is to evaluate an improvement of water quality for contaminated groundwater by $NO_3-N$ using compression packer. For this study groundwater samples collected from 46 groundwater wells were analyzed to clarify $NO_3-N$ contents. Groundwater wells over 10 mg/L in $NO_3-N$ content is 9 wells showing 20% among total samples. $NO_3-N$ contents after compression packer installation showed 26~81% low value compared with before compression packer.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.4
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• pp.205-212
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• 2021

Offshore jacket structures generally comprise steel members, and the safety standard for jacket structures typically focuses on the steel components. However, large amounts of concrete grouting is filled in the legs of the Gageocho jacket structure to aid in the recovery from typhoon damage. This paper proposes a safe and lightweight design for the Gageocho ocean research station comprising steel members instead of large amounts of concrete reinforcement in the legs. Based on the actual design, the structural members are grouped according to their functional roles, and the inner diameter of the cross-section in each design group is defined as a design variable. Structural optimization is carried out using a genetic algorithm to minimize the total weight of the structure. To satisfy the conservative safety standards in the offshore field, both the maximum stress and the unity check criteria are considered as design constraints during optimization. For enhanced safety confidence, extreme environmental conditions are assumed. The maximum marine attachment thickness and the section erosion in the splash zone are applied. Additionally, the design load is defined as the force induced by extreme waves, winds, and currents aligned in the same direction. All the loading directions surrounding the structure are considered to design the structure in a balanced and safe manner. As a result, compared with the current structure, the proposed structure features a 45% lighter design, satisfying the strict offshore safety criteria.