本研究針對一個實際邊坡案例進行位移、地下水位及基質吸力之實地監測，並進一步探討監測結果與降雨之關係。本研究也應用STABLE Win程式分析現地淺層土壤基質吸力變化對不飽和土壤邊坡穩定性之影響。監測結果顯示，降雨入滲易導致崩積土層與頁岩泡水軟化，剪力強度隨之降低而產生滑動面。整體而言，樁中傾斜管位移量遠小於土、岩層傾斜管，顯示目前擋土支撐系統應已發揮抑制變形之功能。地下水位觀測結果顯示，本區邊坡地下水位均低於潛在滑動面位置，因此滑動面目前並無長期浸水情形。邊坡淺層土壤一般位於地下水位之上，處於不飽和狀態。基質吸力監測結果顯示，地表連日乾旱之最大吸力達83kPa接近張力計量測上限值90kPa，而連續降雨後地表吸力迅速降為0kPa。現地邊坡常處於乾濕現象交互作用下，土壤吸力與飽和度成反比關係，吸力變化幅度由大到小依序為0m、0.3m、0.5m、1m。基值吸力會隨著降雨入滲而降低或消失，造成傾斜管最大位移量發生於孔口處，此監測結果與程式分析趨勢相當符合。

The purpose of this research is to monitor the slope displacement 、groundwater level, and matric suction. The results are then used to study the influence by rainfall infiltration. This study also uses program STABLE Win to analyze the effect on the unsaturated soil slope stability due to soil matric suction changes. The monitoring results illustrate that rainfall infiltration can soften the colluvium and shale when immersed in water, resulting in the reduction of shear strength and the development of potential slip surfaces. In general, displacements measured along the inclinometer installed inside the retaining pile are significantly less than displacements measured in soils and rocks behind the wall. This finding shows that the retailing wall system works well in controlling the deformation. The results of groundwater measurement show that the slide surface is free of long term soaking because the monitored groundwater level remains below the slide surface at all times. In general, shallow soil in the slope is unsaturated. The maximum matric suction of 83 kPa has been recorded near the surface when the region does not get any rainfall for a prolonged period. This value is close to the tensiometer limiting value 90 kPa. After heavy rainfall surface soil’s suction falls quickly to 0 kPa. The increase of matric suction is consistent with the decrease in the degree of saturation under drying condition. The decrease of matric suction is also consistent with the increase in the degree of saturation under wetting condition. The amount of suction changes exhibits a decreasing trend as the depth increases from 0 to 1m. Matric suction would vanish after consistent rainfall and cause the maximum displace to occur at the top of the inclinometer near the ground surface. The analytical results agrees with the behavior observed from field monitoring.

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