台灣山區地形陡峭且年降雨量高，導致土石流事件發生頻繁。為降低土石流事件造成的損害，除工程減災設施外亦應考慮集水區降雨預警系統，及於高潛勢土石溪流現地設置土石流監測及警報系統等非工程做法，以利於保全對象的疏散避難。本研究利用室內地聲試驗與火炎山現地監測系統的地聲與影像資料，將室內撞擊產生地聲與現地土石流地聲互相比較取得兩者之相關性來估算現地傳感器安裝的安全距離。本文中現地資料為苗栗縣火炎山自然保留區一號坑內，2015年5月28日與2016年6月13日因梅雨造成之土石流事件。 地監測的結果得知，2015年5月28日事件中礫石型土石流一維地聲儀主頻率帶介於30-40Hz，三維地聲儀上主頻率帶X、Y、Z軸分別為12-45Hz、25-40Hz、0-3Hz；泥流型土石流一維地聲儀主頻率帶介於22-45Hz，三維地聲儀主頻率帶X、Y、Z軸分別為12-40Hz、25-40Hz、0-2Hz；在2016年6月13日事件中一維地聲儀主頻率帶介於27-40Hz之間。而在室內試驗中重物撞擊沙坑之主頻率帶為25-50Hz；而在撞擊點上設置墊片時將會改變主頻率帶的波形。;Debris flows often caused severe damages and casualties in Taiwan slopeland due to the intense rainstorms and fragile geological settings. Besides engineering countermeasures, non-engineering solutions such as rainfall warning system and the on-site debris flow monitoring system can be beneficial for evacuation and hazard mitigation. In this study, the geophone signals and the CCD image obtained from both the monitoring system at Houyenshan, Miao-Li and laboratory experiments are explored to estimate a safe distance for the field sensor installation. The rainfall-induced debris flow events in May 28, 2015 and June 13, 2016 in the Houyenshan Nature Reserve are examined in this study. The main frequency of ground vibration for the May 28,2015 debris-flow event is between 30 to 40 Hz and the 3-D ground vibration’s (X&Y&Z) are between 12 and 45Hz, 25 and 40Hz, 0 and 3Hz, respectively. The main frequency of ground vibration for the June 13, 2016 event is between 27 and 40Hz. In laboratory experiments, the main frequency of ground vibration by heavy impact on sandpit is between 25 and 50Hz.
