土石流之次聲監測乃運用顆粒在運動時所散發聲音之特性，因此本研 究經由實驗找出顆粒撞擊時之音頻特性，有益於了解顆粒運動時之發聲機制。本研究運用二維漏斗內填置細磨石，使細磨石由下方流出後墜落於二維與三維兩種不同邊界條件之渠槽。底床之材質分別為棉布、鬆散顆粒、堅硬顆粒、壓克力等四種，分析顆粒撞擊時之特徵頻率以及流動過程。研究發現顆粒於漏斗中之流動型態可分成主要流動區、表面流動區、蠕動區與靜止區等四個區域，而漏斗中顆粒出流量則有周期性之高低變化。顆粒撞擊於柔軟材質時所散發之特徵頻率與音壓強度皆為較低之情況；當撞擊於堅硬材質之音頻與音壓強度則為較高之情況，顯示顆粒撞擊之頻率與撞擊面之性質及速度有密不可分之關係。 The acoustic monitoring system of debris flows was usually carried out by means of detecting the sound during the particle movements. This study investigated the characteristic of emitted sound while the particle collisions in the laboratory, and it may help understanding the mechanism of sound generation for particle motions. In this work, the spherical mill stones were filled in a quasi-2D silo. Then, particles flow out from the bottom outlet and fall down to the lower 2D and 3D rectangular box, respectively. Four different bed material such as cotton cloth, loose packing particles, dense packing particles and acrylic plate were set up at the box and the sound characteristics and flow behavior with each other. The flow pattern in the silo were classified as core flow zone, surface flow layer, creeping zone and stationary zone. The flow rate at the orifice shown a significant periodic variation due to the arching effect. The dominant frequency and the sound pressure level resulted from particles impact on the soft bed material is lower than that on the hard one. The result demonstrates that both the impact surface and the velocity play important roles on the dominant frequency of particle collisions.
