機率式邊坡穩定分析方法之研究

本文以山區崩積土層及風化岩層之邊坡為研究對象，首先基於可靠度指標，利用EXCEL工作表建立一邊坡破壞機率評估方法，並探討傳統基於最小安全係數所對應的極限滑動面(critical slip surface; CSS)，與機率式基於最小可靠度指標所對應的最可能破壞面(most possibility slip surface; MPSS)，兩者的特性與關係；最後以阿里山公路五彎仔山崩為實際案例，以本文方法進行破壞機率之案例評估。本文獲得主要結果為：①本文方法之結果與案例文獻結果相當，可見本文方法具正確及可行性。②在安全的邊坡情況下，MPSS與CSS位置明顯不同，且MPSS之深度較CSS者為淺，但當邊坡趨於不安全的情況下，二者會愈靠近，土層參數變異特性會影響安全邊坡的可靠度指標及MPSS的位置。在不安全的邊坡情形下，其MPSS與CSS重合；土層參數變異會影響安全邊坡的可靠度指標，但不影響MPSS的位置。③實際案例在最高水位、中水位及最低水位情況下，破壞機率分別為0.659、0.576及0.324，隨著地下位的上升，破壞機率增加。

關鍵字

邊坡；可靠度指標；破壞機率；滑動面

並列摘要

In this paper, the failure probability of slope of colluviums and decomposed rock stratum is discussed. Firstly, a probabilistic method for evaluating slope failure is developed based on the concept of reliability index. The proposed method is constructed by EXCEL Solver Tools and is verified by case studies of the literatures. The characteristics of the critical slip surface (CSS) corresponding to minimum safety factor, and most possibility slip surface (MPSS) corresponding to minimum reliability index, are also discussed. Finally, the practical case of slope failure in Woo-wanchai area, Mt. Ali Road is evaluated by the proposed method. The results show that (1) the proposed method by EXCEL Solver Tools is accurate and feasible; (2) in a safe slope, the MPSS differs from the CSS distinctly, and the MPSS is more shallower then the CSS. The failure probability and the MPSS are both affected by the coefficient of variation of parameters (COV) and the correlation between parameters (ρ). Nevertheless, the MPSS is same as the CSS in an unsafe slope, and only the failure probability is affected by the COV and ρ; (3) in Woo-wan-chai practical case, the value of the probability is equal to 0.324, 0.567 and 0.659 under low, medium and high groundwater condition, respectively. It is indicted that the failure of slope is significantly influenced by groundwater level.

並列關鍵字

slope ； reliability index ； failure probability ； slip surface

國際替代計量

機率式邊坡穩定分析方法之研究

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