過栄養な内港域における再生資源を用いた底質改善手法の提案  [in Japanese] DEVELOPMENT OF THE TECHNIQUE USING RECYCLED RESOURCE FOR SEDIMENT REMEDIATION IN HYPERTROPHIC INNER HARBORS  [in Japanese]

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Abstract

スカムの発生や悪臭問題のある過栄養な内港域において,石炭灰造粒物による底質改善の有効性に関する実証試験を実施した.実証試験開始後,スカムの大量発生は認められず,一定の改善効果があることが確認された.一方で,経時的に石炭灰造粒物層の沈下が生じ,散布区境界外から堆積泥の流入が生じた.これに伴い被覆層上へ最大80cm程度の厚みで浮泥が堆積していた.水槽実験により,グラブバケット工法では,大粒径の石炭造粒物ほど早く沈降するため,間隙率の低い造粒物層が形成されることが示された.また,室内溶出試験により,20cm以上の浮泥の堆積があると浮泥に対する改善効果が明確に現れないことが示された.過栄養な内港域で有効な底質改善手法として,1層目に細粒分,2層目に粗粒分を散布し,圧密沈下が生じた後に3層目を散布する粒度調整 3度撒き工法を提案した.

 We carried out substantiative tests to investigate the effectiveness of the technique using granulated coal ash (GCA) for sediment remediation in the hypertrophic inner harbor that scum (floating sediment clusters) and malodors occur. After applying the technique, it was confirmed that large amounts of scum were decreased, indicating that the technique has effectiveness on the sediment remediation. However, the subsidence of GCA layer occurred temporally. As a result, up to 80 cm of sediment accumulated on the GCA layer. Based on laboratory experiments of the grab bucket method, GCA with larger grain size has faster setting velocity which caused a larger intrusion thickness of GCA into sediment layer, leading to the decrease of the effectiveness of the technique. It was found that the effectiveness decreased when more than 20 cm of sediment accumulated on the GCA layer. We have proposed the most effective method for construction of GCA layer by the following procedures: 1<sup>st</sup> layer of fine GCA, 2<sup>nd</sup> layer of coarse GCA, 3 times of sprinkling GCA to construct the 3<sup>rd</sup> layer of GCA after the end of the subsidence of the 2<sup>nd</sup> layer of GCA.

Journal

  • Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering)

    Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering) 71(2), I_880-I_885, 2015

    Japan Society of Civil Engineers

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