砂質邊坡快速評估方法與安全指標之研究

A Study on the Rapid Assessment Method and Safety Index for Sandy Slopes

陳駿瑜(Chun-Yu Chen) ； 李咸亨(Hsien-Heng Lee)

《中華防災學刊》 5卷1期 (2013/02) Pp. 39-49

摘要

邊坡內地下水位之變化是邊坡安全的重要參數，但其對邊坡穩定安全係數之影響卻鮮少被人完整地探討。現今高科技監測儀器屢見不鮮，但是決定邊坡穩定安全與否的監測指標也缺乏理性客觀的討論，大多僅以經驗值、建議值作為邊坡潛在危險之管理值。因此，本研究結合數值分析法和極限平衡法的優點及特性，詳細分析砂質邊坡的型式、土質、地下水位、應力、應變與安全係數之關係，探討地下水位對砂質邊坡穩定性的影響。本研究中提出邊坡的正規化安全係數和正規化地下水位的，藉由警戒區間的定義，提出行動準則建議。本研究發現接近臨界地下水位時，安全係數急劇下降，且不論土壤Φ值大小都有類似趨勢，故值得作為安全監測時定義管理指標值之參考。所以，本研究建立之三相分析圖及正規化分析圖二種快速評估圖表，可用於缺乏詳細資料的現地邊坡之快速安全評估，以備不時之需。此外，本研究亦定義了安全指標，用以在現地判斷砂質邊坡之安全性。

關鍵字

臨界地下水位 ； 安全係數 ； 邊坡監測指標 ； 坡趾位移

並列摘要

The groundwater level change in the slope is an important parameter of slope safety, but its influence on the safety factor of slope stability was rarely explored completely. Today's high-tech monitoring instruments are common. However, there are fewer monitoring indicators to determine whether or not the slope is stable and safe, and a lack of rational and objective discussions on the matter. Most of them focus only on the value of experience and the recommended value is the management value of the latent danger of the slope. Therefore, this study combined with the advantages and features of the numerical analysis method and the limit equilibrium method to make a detailed analysis of the relationship of the type, soil, groundwater level, stress, and strain of the sandy slope with the safety factor and to explore the impact of groundwater level on the stability of the sandy slope. It was found that when close to the critical groundwater level, the safety factor declines sharply. And regardless of the size of Φ values of the soil, all have similar trends. It is worthy for reference to define the management indicator values in the safety monitoring. Therefore, this study established two kinds of rapid assessment charts, three phase charts and normalized charts, which can be used for fast safety assessment of the slope in situ, for which detailed information is lacking, in case of contingencies. Besides, this study also defined the safety index, which can be used for judging the safety of sandy slope in site.

並列關鍵字

critical groundwater level ； safety factor ； slope monitoring indices ； displacement of slope toe