不同型態土石流地聲特性之實驗研究

Experimental Study of Ground Vibrations Produced by Different Types of Debris Flows

黃清哲(Ching-Jer Huang) ； 孫坤池(Kun-Chih Sun) ； 陳潮億(Chao-Yi Chen) ； 尹孝元(Hsiao-Yuan Yin)

《中華水土保持學報》 38卷4期 (2007/12) Pp. 417-430

https://doi.org/10.29417/JCSWC.200712_38(4).0008

摘要

本研究以地聲檢知器(geophone)量測人工模擬不同型態土石流流動時所產生之地聲，實驗量測所得之地聲時域訊號經由快速傅立葉轉換(FFT)及Gabor轉換分析，以求得地聲之頻域特性。實驗依照水土保持手冊(1992)將土石流的類型區分為礫石型、一般型及泥流型。實驗結果顯示礫石型土石流地聲頻率主要介於10到300Hz之間；而泥流型土石流的地聲頻率介於5到20Hz之間。一般型土石流的地聲頻率則介於兩者之間，當其土石材料中之礫石成份增加時，頻率在20到300Hz之地聲振幅會明顯增大。由此可知20到300Hz之地聲主要是由於礫石摩擦、撞擊實驗渠道底床所產生。本研究還利用每單位時間之地聲累積能量與互相關(cross-correlation)的方法來推算土石流之平均流速。結果顯示地聲累積能量方法較容易推算出土石流之流速。然而，當地聲檢知器所測得土石流之地聲訊號微弱時，如泥流型土石流，便不容易以上述兩種方法推算出土石流之流速。

關鍵字

地聲檢知器 ； 土石流 ； 地表振動地聲 ； 頻率 ； 互相關

並列摘要

The purpose of this study is to examine the ground vibrations produced by different types of debris flow in the laboratory. Ground vibration was recorded by geophones. Ground-vibration signals in the time domain were transformed into the frequency domain using the Fast Fourier Transform and into the Time-Frequency domain using the Gabor Transform. According to the handbook of soil and water conservation (Soil and Water Conservation Bureau, 1992), debris flows can be classified into three types; the boulder type, the cobble-gravel type, and the muddy type. Experimental results show frequency range of ground vibrations associated with boulder-type debris flows is between 10 to 300Hz, while muddy-type debris flows is between 5 to 20 Hz. The frequency range of the cobble-gravel type debris flows includes both ranges. Ground vibrations of 20 to 300 Hz become notable as larger grains were added to the experimental materials. In addition, both the accumulative energy method and the cross-correlation method were used to calculate the average speed of the debris flows.

並列關鍵字

geophone ； debris flows ； ground vibration underground sound ； frequency ； cross-correlation