現今加勁擋土結構物(Geosynthetic-Reinforced Soil structures)之設計主要以評估安全係數的方式進行定量分析(deterministic approach)，然而以安全係數為主的設計方式並未能通盤考慮到設計參數與計算模式的不確定性。因此，本論文選用機率方式(probabilistic approach)並使用兩種加勁材張力預測模式(側向土壓法與K-stiffness法)進行加勁擋土牆內部穩定之可靠度分析。本論文首先評估各種可靠度分析方式(如蒙地卡羅模擬MCS、一階可靠度分析FORM與一階二次矩法FOSM)對破壞機率計算的影響。之後，進行參數靈敏度分析，找出對加勁擋土牆內部穩定影響較大(如破壞機率變化較大)的參數。進一步，本論文利用可靠度分析發展出一系列可靠度設計圖。本論文舉例說明可靠度設計圖之使用步驟與驗證其設計之準確性。最後，本論文也探討計算模式不確定性(如加勁材張力預測值與實測值之偏差)對可靠度設計之影響。本研究發現於未考慮模式不確定下，選用側向土壓法計算加勁材斷裂之破壞機率遠大於使用K-stiffness法所計算之破壞機率。而在拉出破壞模式下，選用側向土壓法與K-stiffness法計算之破壞機率較為接近。若考慮模式不確定，側向土壓法所計算之破壞機率與K-stiffness法計算值較未考慮模式不確定下為接近。本研究結果預期能對加勁擋土牆內部穩定之可靠度分析與設計提出實用的貢獻。

Geosynthetic-Reinforced Soil (GRS) structures are conventionally designed using the deterministic approach to calculate factor of safeties. This approach, however, is not able to consider variability and uncertainty from design variables and prediction models. On the other hand, the reliability approach considers the possible variations in the design parameters and gives more realistic estimates of the safety of the structure and the possible risk of failure. Therefore, this study presents reliability-based design (RBD) for internal stability of GRS structures. Two prediction methods (i.e., lateral earth pressure and K-stiffness methods) were used to predict reinforcement tensile loads and their model uncertainty on RBD results was investigated. This study first compared failure probabilities and reliability indices calculated by different reliability methods: Monte Carlo simulation (MCS), first-order reliability method (FORM), first-order second-moment method (FOSM). Afterward, a sensitivity study was conducted using MCS to identify design variables that affect the probability of internal failure of GRS structures. Based on the results of the sensitive study, a series of additional simulations were conducted where the significant variables were varied over a broad range. The results of these simulations were used to develop a series of RBD charts. A design example was provided to illustrate the RBD procedure and to validate the proposed RBD charts. Last, the effect of model uncertainty on RBD results was evaluated. The model uncertainty was statistically quantified using a model factor, defined as the measured reinforcement load divided by the predicted reinforcement load. The impact of the model factor and its potential correlation with the predicted reinforcement tensile loads on RBD results was discussed. This study demonstrates the RBD results using two prediction methods become more consistent when the model uncertainty is considered. The results obtained from this study provide insightful information for RBD for internal stability of GRS structures.

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