台灣本島係由菲律賓板塊以及歐亞板塊相互擠壓形成,而山坡地面積約占全島面積的四分之三,因此探討邊坡失穩之行為,已成為一重要課題,降雨是誘發邊坡失穩的原因之一,每當雨季或颱風降雨豐沛時期會使地下水位升高或濕潤面達到不飽和區導致邊坡產生滑動。本研究以數值分析探討不飽和土壤邊坡因降雨入滲導致邊坡失穩之機制。首先將不飽和邊坡與降雨入滲的固體力學方程式及偏微分方程式建立,再利用一系列案例驗證其分析軟體之可行性。研究中藉由不飽和應力-滲流耦合分析,配合剪力強度折減法,模擬不飽和邊坡之穩定性,觀察邊坡內部孔隙水壓力、有效應力、位移以及安全係數等分布情形,並與前人分析結果進行比較。最後探討不同坡高、坡度、坡面降雨修正以及彈性模數等邊坡參數對於不飽和邊坡穩定性之影響。
Abundant rainfalls often resulted in the rapid rising of water table, and many shallow landslides were encountered during or after these abundant rainfall. In this study, the solid mechanics equations and seepage partial differential equation that representing the transient flow of water in unsaturated soil medium have been solved using a numerical tool. The study used shear strength reduction technique and coupled hydro-mechanical analysis to examine stability of model slope. The numerical result was compared in term of pore-water pressure, effective stress, displacement and factor of safety. The effects of slope height, slope angle, and elastic modulus on the stability patterns were also examined.