流砂，土石流

[II-188] Study on woody debris blocking on single-span bridges in mountainous rivers focusing on shape and specific gravity

〇Kana Nakatani¹, Yuji Hasegawa², Yoshifumi Satofuka³, Takuya Higashitani¹, Ken'ichiro Kosugi¹ (1.Kyoto University, 2.Hiroshima University, 3.Ritsumeikan University)

Keywords:woody debris, single-span bridges, blocking, laboratory experiments , shape, specific gravity

When bridges are blocked with accumulated woody debris (WD), a high flow depth leads to overflow and causes damage. In this study, we conducted laboratory experiments using bridge model without pier. We considered WD with log and shape with roots, and specific gravity 0.8 and 1.2. From results, in same specific gravity, shape with roots caused blocking in smaller WD. Considering shape with roots, the specific gravity influenced when bridge clearance was small. We also applied logistic regression analysis to experiment results and proposed an approximate expression for blocking possibility.