Yo Ito

Recent advancement of groundwater hydraulics in underground space technology

Various types of underground space have been developed to support human activities and civilization. The knowledge of groundwater hydraulics is indispensable in keeping excavation processes within safety limits and mitigating impacts on the groundwater environment. This review paper summarises history, categories, hydraulic problems and management in underground space technology. Some topics of mathematical modeling and characteristics in and around underground space structures are demonstrated to illuminate recent advancement in groundwater hydraulics. Attractive themes involving both hydraulics and underground space technology are suggested to boost a future progress.

FUNDAMENTAL STUDY ON REINFORCEMENT CORROSION IN CONCRETE CRACK UNDER SEAWATER SEEPAGE

海洋中空大型構造物では, その内外で水圧差を生じひびわれ中に海水が浸透することとなり, 水密性のみならず鉄筋の腐食促進が懸念される. 本研究では, こういった環境下にある鉄筋腐食に係わる基本的性質を明らかにすることを目的として, 割裂ひびわれに直行する鉄筋を設置した特殊な円柱供試体に人工海水を長期間連続通水し, その浸透特性および鉄筋の腐食性状について検討を加えた.

Fundamental study on migration of nuclides in underground disposal of low-level radioactive waste

In order to clarify the mechanism of solute migration in an unsaturated zone of soil stratum, the basic experiments on the upward and downward movements of water and solutes (NaCl, Sr, Co, Cs) under the artificial environment (rainfall-evaporation cycles) were carried out. The experimental apparatus used in this study consists of a large soil box, nozzles of rain-fall, infrared lamps, thermometer sensors, recorders and sampling tubes. The vertical profiles of solute concentration, temparature and water content in the unsaturated zone above the groundwater are measured for different groundwater depth. The analytical solutions of governing equations at the steady-state are derived. The comparison between solutions and experimental results shows a good agreement. The results describe that the solute migration depends upon not only vertical movement of moisture but also a depth of capillary fringe.