降雨引致地下水位變化及邊坡變形分析

近年來氣候異常日趨嚴重使地質破碎之山坡地穩定性降低，為探討其降雨與邊坡之關係，本研究首先以彙整現地監測資料分析；以回歸方式歸納出降雨對邊坡之水位變化及變形量影響，考量橫向集水管之成效比對地下水位上升情形，並整理降雨導致地下水位抬升之時間差。最後以數值模擬廬山北坡地區，套入回歸累積雨量1200毫米之水位面，以地表、岩層及地下水位面高程建立二維及三維模型，並以極限平衡法與有限元素法分析主要滑動體及兩個次要滑動體，探討邊坡穩定性及變形量。研究結果顯示，以監測滑動資料之回歸公式可為預警系統參考之一，則地下水位之變化受橫向集水管之成效影響，其地下水位之變化為近年來抬升速度較快且時間平均縮短5小時，而數值模擬降雨達1200毫米之地下水位時，最大變位量為東側次要滑動體最為顯著，則以極限平衡分析為安全狀態，但依據現地調查中發現地表仍有破壞情形，因此以極限平衡分析至臨界狀態時於地表亦有開裂情形。

關鍵字

降雨；監測資料；地下水位；數值模擬

並列摘要

For the past few years, the increasing seriousness of the climate decreases the stability of the geologically broken hillsides. In order to discuss the relation between the rainfall and the slope, this research collects and analyzes the slope monitoring data for the first step. The study can figure out the equation of the relation between the raise of groundwater level and slope deformation. Secondarily, the situation of groundwater level rising caused by the rainfall in comparison with the effective of horizontal water collection pipes. Finally, the simulation of Lushan area will set into the water level of 1200 millimeter by accumulated rainfall, and build the 2D and the 3D model. And use the sliding surface of the study area and the two sliding surface are taken to do analysis of limit equilibrium method and finite element method to explore the stability and deformation of the slope area. From the result of experiment, regression formula of the slope monitoring data can be the one of reference of the early warning system. And, the groundwater variation is affected by the effectiveness of the horizontal water collection pipe, the velocity of lifting the groundwater level is faster and reduced by an average of 5 hours in recent years. When the numerically simulating of a rainfall reaches to 1200 mm, the maximum displacement is the most significant secondary slip in the east, and the limit equilibrium analysis is taken as a safe state. However, according to the local investigation is found that the surface is still damaged. Therefore, when the limit equilibrium is analyzed to the critical state, there is also a crack in the surface.