Development of Wetting Band on Unsaturated Soil Slopes Subjected to Rainfall

[[abstract]]依據傳統分析設計邊坡方式，常以飽和土壤力學行為模式進行分析設計。在降雨情況亦假設地下水位為滿水位狀態執行分析，但所獲得結果無法代表實際邊坡情況。因為在分析過程中，忽略了非飽和土壤邊坡存在基質吸力與氣候環境對邊坡穩定之影響。因此，為了能近似模擬實際邊坡狀況，則必須加以考慮土壤中基質吸力對邊坡穩定性之貢獻。 本研究為了能進一步瞭解自然邊坡於降雨作用下，整體邊坡土壤孔隙水壓力、飽和度分布變化情況，則藉由有限元素法PlaxFlow程式進行數值模擬分析，分別模擬邊坡土壤完全為殘留表土狀況及殘留土下存在岩盤狀況兩大部分。將以數值模擬不同坡度幾何條件(40°、60°、80°)，搭配不同降雨強度(5mm/hr、20mm/hr、60mm/hr、130mm/hr)及降雨延時條件分析計算，另外，再進一步探討降雨強度、降雨延時、風化土壤之厚度及坡度等因素，對殘留土坡之土壤浸潤帶深度發展之影響。[[abstract]]Based on the traditional analysis design slope, usually carries on the analysis design by the saturated soil mechanics behavior pattern. Is raining the situation also supposition groundwater level for the full water level state administration analysis, but obtains the result to be unable to represent the actual slope situation. Because in the analysis process, has neglected the unsaturated soil slope existence matrix suction and the climate environment to slope stability the influence. Therefore, in order to can approximately simulate the actual slope condition, then must perform to consider in the soil contribution the matrix suction on slope stability. This research in order to can further understand the nature slope to rains under the function, the slope soil pore-water pressure, degree of saturation distribution change situation, then the affiliation carries on the value simulation analysis by the finite element procedures PlaxFlow program, separately simulates slope the soil completely for the residual surface soil condition and the residual under existence rockband condition two major parts. By the numerical simulation different slope geometry condition (40°,60°,80°), will match the different rainfall intensity (5mm/hr, 20mm/hr, 60mm/hr, 130mm/hr) and rains duration condition analysis computation, moreover, further will discuss the rainfall intensity again, rains duration and thickness of residual soil, and slope gradient, will thickness of wetting band development to residual soil