摘要：

本研究首先以二維顆粒流程式(PFC)模擬小林村崩塌,將垂直力量所記錄之震動(dòng)訊號(hào)利用Hilbert-Huang transform (HHT)加以分析,將四個(gè)監(jiān)測(cè)點(diǎn)所得到之震動(dòng)訊號(hào)繪製成時(shí)頻圖,可估算出崩塌持續(xù)時(shí)間,並與先前現(xiàn)地踏勘所得到的堰塞壩資訊及甲仙寬頻地震測(cè)站所記錄之完整震動(dòng)訊號(hào)做比較.本研究再以顆粒流程式(PFC)與連體程式(FLAC)耦合方法,建立山崩流動(dòng)過(guò)程之?dāng)?shù)值模型,以小林村山崩為案例.以離散元素方法(PFC)模擬山崩產(chǎn)生的巖塊散開(kāi)滑動(dòng)與流動(dòng)過(guò)程,當(dāng)巖塊撞擊有限差分?jǐn)?shù)值模型(FLAC)構(gòu)成的連體網(wǎng)格時(shí),兩程式在同一時(shí)步內(nèi)會(huì)相互交換力與速度,並設(shè)置監(jiān)測(cè)點(diǎn)偵測(cè)其震動(dòng)訊號(hào),再利用HHT分析所得震動(dòng)訊號(hào)之時(shí)頻圖,探討其震動(dòng)頻率特徵,並與距離小林村11.4公里之甲仙寬頻地震站之訊號(hào)記錄比較.進(jìn)行各項(xiàng)參數(shù)案例分析,更深入地探討各項(xiàng)參數(shù)對(duì)數(shù)值模型的影響,希望藉由此新的方法更進(jìn)一步貼近真實(shí)崩塌情況.本研究在相同邊坡上建立一場(chǎng)落石之案例,藉由模擬石塊自由墜落(free fall)至邊坡,並在邊坡設(shè)置多個(gè)監(jiān)測(cè)點(diǎn),分析單一巨石撞擊地面產(chǎn)生之震動(dòng)訊號(hào),可從時(shí)頻分析中得到震波傳遞之振幅速度,並探討其能量隨距離增加或地質(zhì)材料不同而產(chǎn)生衰減的情況.A two-dimensional numerical coupling approach using the Particle Flow Code (PFC) and Fast Lagrangian Analysis of Continua (FLAC) code was developed to simulate the flow process of landslides and rock avalanches. The Xiaolin rock avalanche was used as a case study. The sliding of the rock fragments was simulated by PFC. When the rock fragments impact on the top boundary of FLAC, forces and velocities of the boundary grids were transmitted between the two codes. Monitoring locations were assigned in the coupled numerical model to record the seismic signals induced by the simulated rock avalanche. The time-frequency spectrograms of the seismic signals were analyzed using Hilbert-Huang transform (HHT) for examining the seismic characteristics. The simulated results were compared with the seismic signals recorded during the landslide from a broadband seismic station, SGSB, which is 11.4 km away from the Xiaolin landslide site.A rock-fall case was established using the same slope to simulate the signal induced by a single free falling rock. Monitoring locations were assigned in the coupled numerical model to record the seismic signals. The time-frequency spectrograms of the seismic signals were analyzed using HHT to examine the amplitudes of the seismic wave and the propagated velocities. The energy attenuation of the seismic wave versus distance and for different geological materials were analyzed.

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