炭酸カルシウム結晶析出時の飽和度が改良砂の液状化強度特性に及ぼす影響  [in Japanese] LIQUEFACTION MITIGATION EFFICIENCY OF SAND IMPROVED WITH CALCIUM CARBONATE PRECIPITATED UNDER VARIOUS DEGREES OF SATURATION  [in Japanese]

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Abstract

炭酸カルシウム(CaCO<sub>3</sub>)の結晶をセメント物質とする固化土のせん断強度は,間隙での結晶析出時の飽和度が低いほど高まるとされている.本研究では,CaCO<sub>3</sub>析出時の飽和度をコントロールし砂の液状化抵抗の改善効率を高める試みを粒径が異なる砂に適用し,砂の粒径によるその改善効率の違いを調べた.実験ではCaCO<sub>3</sub>含有率を1%以下,その析出時の飽和度を20 ~ 100%の範囲でコントロールした豊浦砂および4号硅砂供試体を非排水繰返し三軸試験に使用した.CaCO<sub>3</sub>析出には,ウレアーゼの尿素分解作用を活用する方法を採用した.砂粒子表面に析出した結晶の観察とその同定はSEM-EDXで行った.その結果,飽和度をコントロールしたCaCO<sub>3</sub>析出による液状化抵抗の改善効果は,CaCO<sub>3</sub>結晶径に対し砂の粒径が相対的に小さいほど高いことが明らかとなった.

 It is pointed out that the shear strength of cemented soil improved with calcium carbonate (CaCO<sub>3</sub>) crystal is enhanced by decrease in saturation degree during precipitation. In this study, improvement efficiency of liquefaction resistance enhanced through controlling saturation degree (from 20 to 100%) and CaCO<sub>3</sub> content (from 0 to 1%) was investigated by undrained cyclic triaxial tests for coarse and fine sand specimens. Enzymatically Mediated Calcite Precipitation (EMCP) technique was employed to precipitate CaCO<sub>3</sub>. SEM-EDX was utilized to observe calcium carbonate crystal on the sand grain surface and to identify the crystal. It was found that, in EMCP with controlling saturation degree during precipitation, high efficiency in liquefaction mitigation was provided to finer sand including larger crystal.

Journal

  • Journal of Japan Society of Civil Engineers, Ser. C (Geosphere Engineering)

    Journal of Japan Society of Civil Engineers, Ser. C (Geosphere Engineering) 74(2), 164-176, 2018

    Japan Society of Civil Engineers

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