改良された袋詰玉石工の洪水時の安定性評価技術の開発とこれを活用した袋詰玉石工の構造・配置の技術的検討

抄録

In the Tamagawa River, gravel bags were installed for the erosion protection of the river bank at the end of a groundsill where mudstone was exposed. However some gravel bags were flushed out by flood flows. In this study, a new numerical simulation method was developed which is capable of predicting motions of gravel bags using the Lagrangian approach and fluid motions using the Eulerian approach. Improvements of the structure and the arrangement of gravel bags were examined by a field survey and numerical investigations on stability of gravel bags in flows. From these investigations, it was shown that the structure in which a gravel bag divided into small bags was wrapped in a large bag was effective as the structure for enhancing the stability of the gravel bags. In addition, it is emphasized to install gravel bags integrally downstream from the groundsill to the region where the high flow velocity exerting on gravel bags decelerates.