砂質堤防越水時の浸透とすべり破壊を考慮した越流破壊解析法の検討

Abstract

本研究では，均一型砂質堤防の越水模型実験を実施し，砂質堤防の越流侵食現象が再現可能な数値解析モデルの構築を図った。実験では，堤防の越流破壊現象について粒径および浸透流の進行が越流侵食に与える影響について考察を行った。数値解析では，粒径および浸透の進行によって変化するせん断抵抗の影響を考慮した堤防の越流侵食モデルの構築を図った。流れの水深積分モデル，堤体内の浸透流解析，非平衡流砂モデルの枠組みによる土砂輸送，斜面安定解析の4つを結合し同時に解析することにより越流侵食破壊現象の再現を試み，一部の検証ケースにおいて計算モデルの結果は概ね良好な結果が得られ，堤防越水時の不飽和堤土の侵食評価において，浸透水によるせん断抵抗の変化を考慮することの重要性が示された。

In this study, experiments were conducted to clarify the mechanism of embankment erosion due to overtopping flow under saturated and unsaturated sediment, and a numerical model was developed to compute the erosion of river embankment by flow overtopping. An influence of saturation and sediment size in the erosion process was discussed using the results of experiments. In the computation of erosion process of embankment, the infiltration process and shear strength due to suction on the unsaturated sediment bed were considered as a new equation. In order to simulate a phenomenon of embankment erosion, the numerical model consists of four modules, two-dimensional shallow water flow, seepage flow, sediment transport using framework of non-equilibrium model and two-dimensional slope stability. The developed model was tested for erosion of embankment. The numerical results of embankment surface erosion and moisture movement in the embankment were agreeable with the results of experiments.