降雨引發坡地淺崩塌模式之建立與探討

Abstract

本研究利用理查氏方程式(Richards equation)配合無限邊坡穩定理論(infinite slope stability theory)，探討降雨引發之坡地淺崩塌。研究中，首先探討降雨引發陡坡及緩坡淺崩塌之類型與機制，並依據其結果，推導地下水位上升引發坡地淺崩塌之充分條件，再進一步探討降雨特性，包括雨量、延時及雨型，對坡地淺崩塌之影響。結果顯示，陡坡之淺崩塌可能發生於土壤未飽和或飽和處，然而緩坡似乎僅可能發生於土壤飽和處。降雨導致土壤虹吸(soil suction)減小與地下水位上升，皆可能引發坡地崩塌。地下水位上升引發坡地淺崩塌之充分條件，可作為工程實務上，判別坡地發生崩塌之簡易方法。此外，降雨雨量、延時與雨型對坡地是否發生淺崩塌，以及破壞深度及時間皆有重大的影響。

In this study, based on Richards equation and infinite slope stability theory, a rainfall-triggered shallow landslide model is developed and examined. After the developed model is verified, the type and mechanism of failure in steep and mild slopes are investigated first. The influences of rainfall characters including intensity, duration, and pattern on shallow landslide are then examined. The results show that the failure of steep slope could happen when the soils are unsaturated or saturated. However, the failure of mild slope seems to occur in saturated soils only. Both the decrease of soil suction and the rise of groundwater table caused by rainfall could trigger landslide. The intensity, duration, and pattern of rainfall have significantly influence not only on the occurrence of shallow landslide but also on the depth and time of soil failure. In addition, the sufficient condition of landslide caused by the rise of groundwater table is derived and it could be used in engineering practices.