全光纖邊坡穩定系統整合與現地應用測試(4/4)

Abstract

傳統邊坡安全監測大多採用傾斜管配合手動式傾斜儀監測地層內滑動面之所在位置及移動量，地下水位監測則多使用開口式水位計。這些監測儀器幾乎全部使用手工在現場紀錄讀數。此一安排不但費時，在雨季或邊坡發生滑動時，現場紀錄讀數可能無法進行或非常危險，而這些情況下也可能是最需要監測儀器讀數的時候。近年來雖有可做自動化監測之電子式監測儀器之研發，但電子式自動化監測系統具有價格昂貴、易受電磁波干擾、雷擊破壞、且儀器設備若長期處於潮濕環境容易短路故障等缺點。本計畫所研發之被動式光纖感測器相較於電子式儀器的優點在於地層內沒有任何電子裝置，訊號傳輸距離遠可達數十公里及在光纖傳輸線上可連接多點或分佈式之優點。本計畫以阿里山台18線公路五彎仔路段作為試驗場址，使用本研究團隊研發之光纖感測地層移動監測系統與分佈式光纖水壓計來監測該地區之地層滑動及水壓變化，以評估使用全光纖感測系統在邊坡穩定監測之實用性，並配合地下水文數值模型分析，以作為該地滑區日後穩定評估方法之依據。其中所安裝之光纖感測地層移動與分佈式光纖水壓監測系統已在2008之辛樂克颱風與2009年之莫拉克颱風期間發揮其功能，在颱風期間持續提供並紀錄重要之地層移動與水壓分佈之數據。

Conventional slope stability monitoring often involves the use of inclinometer casings and open end piezometers. A plastic or aluminum casing is installed in the ground. An electronic carriage referred to as the inclinometer probe (IP) is lowered into the pre-installed casing to measure the inclinations. The displacement profile of the casing is determined by accumulating relative movements from IP readings. Open end piezometers are used to monitor the ground water levels. Both sensors are read manually in the field. The procedure is time consuming and can be dangerous when conducted in rainy season or when the slope is unstable. The safety hazards may prevent the critical instrument readings be taken when they are needed the most. Many automated electronic devices have been developed recently. These devices can be costly and subject to electromagnetic interferences and lightning damage when deployed in the field. In comparison with electronic devices, the optic fiber sensors which are passive systems with no electronic circuitry installed underground can easily transmit signals by tens of kilometers through light. Multiple sensors can be connected to a single optic fiber. A test site has been set up at the Five Turn Point of Highway 18 near Alishan. The fiber optic ground displacement and ground water monitoring sensors developed by the research team have deployed at the test site. The main purpose of this research is to verify the feasibility of using an all fiber optic sensor system in slope stability monitoring. Coupled with field measurements, a ground water numerical model will be established as a basis to evaluate the slope failure mechanisms. The fiber optic ground displacement and pore water profile monitoring systems have demonstrated their effectiveness by continuously transmitting and recording valuable data during Typhoon Synlaku in 2008 and Morakot in 2009.