土石流是台灣山區最常致災的坡地災害之一，為降低災害損害，除了由事件發生前的降雨量提出預報，也能利用現地傳感器偵測土石流的流動高度、地表震動變化，以得知其發生強度與時間，進而進行相應對策與預警。本研究分別利用室內實驗與現地監測之地聲、超聲波與影像系統，將顆粒流與土石流之流動特性與地聲訊號相互比較驗證，以分析兩者之相關性。本文主要探討 2015/5/28 梅雨期間的鋒面降雨所引起之火炎山土石流事件。
在室內實驗中，由監測資料顯示顆粒流動特徵頻率約300 Hz，且其強度與流動高度有明顯的正相關性。在現地監測中，礫石型土石流主頻分佈比泥流型濃度土石流頻譜高；本次事件礫石型頻譜特性介於30 ~ 45Hz，泥流型土石流頻譜特性則在 20 ~ 30Hz 間。藉由影像系統驗證地聲與超聲波系統，得知地聲儀測得地聲數據特性與流動高度之間的相關性，以作為土石流預警系統之闕值訂定依據。

Debris flows are one of the most common and hazardous slope disasters in Taiwan. The warning system based on sensors detecting flow heights and ground vibrations of debris flows provide some lead time for evacuation. Both field monitoring and laboratory experiments are carried out by employing geophones, ultrasound sensor and camera/CCD-image systems. The flow characteristics and ground vibration signals of the granular flows in the laboratory and the rainfall-induced debris flows on May 28, 2015 at the Houyenshan are analyzed and compared with each other. The characteristics frequency of ground vibration by granular flows is about 300 Hz, and the geophone intensity are correlated with flow heights. The main frequency of ground vibrations by viscous debris flows is higher than the dilute debris flows. The former is between 30 and 45Hz and the latter is between 20 and 30Hz. With validation through CCD images, we further correlated ground vibrations and flow heights, which can be regarded as the basis of debris-flow warning system.

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