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Title: 大気中二酸化炭素の溶解によるアルカリ性トンネル排水のpH低減
Other Titles: Reduction in pH of Alkaline Groundwater Seepage from Tunnel by Dissolving Atmospheric Carbon Dioxide
Authors: 青木, 卓也1 Browse this author
五十嵐, 敏文2 Browse this author →KAKEN DB
飯尾, 佳浩3 Browse this author
西尾, 英明4 Browse this author
Authors(alt): Aoki, Takuya1
Igarashi, Toshifumi2
Iio, Yoshihiro3
Nishio, Hideaki4
Keywords: アルカリ性トンネル排水
alkaline seepage from a tunnel
gas-liquid reaction
geochemical calculation
dissolution of atmospheric carbon dioxide
Issue Date: 10-Dec-2010
Publisher: 日本応用地質学会
Journal Title: 応用地質
Volume: 51
Issue: 5
Start Page: 220
End Page: 228
Abstract: pH10~11のアルカリ性を呈するトンネル湧水に対して, 大気中の二酸化炭素の溶解を促進することによる中和の過程を評価するために, 室内および現地で気液接触試験を実施した. 室内試験の結果, トンネル排水を空気で曝気する方法がpHを低下させる速度が最も速く効果的であり, さらに, 気液接触時間を増加させることによってpHをより低減できることが明らかになった. このことは, 気液接触面積を増加させ, かつ気液接触時間を長くすることが大気中の二酸化炭素の溶解促進につながることを示唆する. さらに, 溶存二酸化炭素の関数としてpHを表現するモデルを構築し, 大気中二酸化炭素の溶解速度を評価した. その結果, 二酸化炭素の溶解は, 大気と平衡にある溶存二酸化炭素濃度とトンネル排水の溶存二酸化炭素との差に関する一次反応で評価できることがわかった. このモデルによる評価結果とトンネル現場の地形条件から多段の越流堰からなる水路方式が簡単かつ有効なpH低減対策であると判断される. さらに, 実トンネル排水を用いた現地試験から得られたpH低減結果と本溶解モデルを用いた評価結果とがおおむね一致したことから, 本溶解モデルを実際の水路設計に反映できると考えられる.
Gas-liquid mixing experiments under both laboratory and in situ conditions were conducted lo evaluate the process of neutralizing alkaline seepage from a tunnel (pH 10 to 11) by facilitating the dissolution of atmospheric carbon dioxide. The results showed that air bubbling of the tunnel seepage was the fastest and most effective method in reducing the pH of the seepage, and that a longer mixing period was also effective in reducing the pH. This indicates that increasing the gas-liquid contact area and contact time effectively induced the dissolution of atmospheric carbon dioxide. Kinetics of the dissolution of atmospheric carbon dioxide was evaluated by constructing a model that expresses the change in pH as a function of the dissolved carbon dioxide concentration. The dissolution was found to be a first-order reaction with respect to the difference in concentration between the saturated aqueous carbon dioxide with the air and actual aqueous carbon dioxide of the tunnel seepage. Based on the above results and topographical conditions at the tunnel site, we are proposing the use of a channel with a series of weirs as a simple but effective remediation method. The model also successfully simulated pH reduction during the in situ experiments, which makes it useful in the design of an actual channel that will be used at the site.
Type: article
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 五十嵐 敏文

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