| 講演要旨(和文) | | 不飽和砂試料の封圧の増加に伴うP波速度測定結果を説明できる速度モデルについて検討した.P波速度は,試料の初期飽和度に依存し,封圧の増加に伴って漸増する.P波速度の変化は封圧の増加に伴う間隙流体の飽和度の変化に起因する.DomenicoはGassmann式を間隙流体を飽和度に応じた体積弾性率で置き換えることによって不飽和状態に拡張した.しかし,各間隙の飽和度が一様であるとすると実験結果を説明できない.そこで,試料内の初期飽和度が不均一なモデルを考えた.不均一飽和モデルは,試料を分割し,各分割要素に乱数を用いて初期飽和度を与える.試料全体のP波速度は各要素の弾性率からHill平均で計算する.計算されたP波速度変化は,初期飽和度,分割数,飽和度の分布範囲に依存する.不均一飽和モデルによる不飽和状態のP波速度計算結果は,実測の速度変化をほぼ説明できた. |
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| | 講演要旨(英文) | | A series of P-wave propagation tests were conducted for saturated, imperfectly saturated and air-dried sand specimens. Measurements were conducted in a chamber under confining pressures ranging between 0 and 10 a.t.m. Under an imperfectly saturation condition, P-wave velocity in sand gradually increases with confining pressure because air bubbles are compressed or dissolved in water under the effect of pressure. The confining pressure-velocity curves of imperfectly saturated sand cannot be estimated by Gassmann-Domenico substitution equation assuming uniform saturation. The velocities depend not only on the degree of saturation but also on the types of saturation. We proposed a non-uniform saturation model based on the Hill average. We can explain the experimental results for imperfectly saturated sand with this model. |
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