著者

三村 衛 吉村 貢 寺尾 庸孝 豊田 富士人

出版者

社団法人地盤工学会

雑誌

地盤工学ジャーナル (ISSN:18806341)

巻号頁・発行日

vol.6, no.2, pp.141-155, 2011-07

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本文データは地盤工学会の許諾に基づき登録したものである岐阜県最大の前方後円墳である昼飯大塚(ひるいおおつか)古墳の史跡整備の一環として実施された発掘調査に伴い,地盤工学の観点から墳丘盛土の調査を行った. 破壊的な調査・試験方法が適用できないことから,本質非破壊調査手法である表面型RI密度水分計と針貫入試験を適用した. 針貫入試験による力学的な特徴から墳丘盛土がほぼ水平の構造を持つことが明らかとなった. 部分的には斜めの層構造も確認され,古墳墳丘の築造材料の掘削・運搬・荷降ろしの過程を考察する資料を得た. また,強度の変動パターンを分析することにより,墳丘盛土が15~40cm程度の層厚で築造されたという痕跡が得られ,墳丘試料に対する締固め試験により,墳丘盛土の築造時の締固めエネルギーは,およそ人が足で踏み固めたものに相当する0.1XEcJIS程度であることがわかった. 墳丘復元に使用される候補材料についても室内地盤材料試験を行って,現墳丘の性状に近い材料を選定し,墳丘復元工事の施工方法を提案した.Geotechnical characteristics for the earth mound of historical tumuli are recently strongly required during the archeological investigation because the mechanical properties of mound soils have to be evaluated for conservation of those tumuli particularly in the case that they have to be restored or partly reconstructed. In the present paper, the procedure of the geotechnical investigation for geo-relics is introduced by exemplifying the achievement for the Hirui-Otsuka Tumulus, the largest keyhole shaped one in Gifu Prefecture. Needle penetration test is adopted as an almost non-destructive testing procedure to measure the equivalent uniaxial strength of the tumulus mound with little damage. On the basis of a series of in-situ experimental findings, the horizontally layered structures have been confirmed throughout the tumulus with different earth materials. The typical traces of compacted earth reflecting the procedure of construction of the tumuli mound as a variation of strengths have also been detected. A series of laboratory tests was conducted on the soils excavated from the tumulus as well as artificial ones selected for restoration of the tumulus. The properties of particle size distribution and retention have provided the useful suggestion for reconstruction of the lost tumulus mound that directly contacts the original tumulus mound. Compaction tests on the excavated tumulus mound soils shows that the tumulus mound was constructed with the energy of O.lEcjjs which is almost equivalent to the one with treading down. The investigated results have provided the effective proposal for restoration procedure of the tumulus.