應用可靠度分析方法於加勁擋土牆之設計初探

近年來台灣地區地狹人稠，山坡地開發日益增加，山區濫墾濫伐導致許多災害發生，而加勁擋土結構不僅可以美觀、維護生態且能容許較大變形量，因此廣泛運用在擋土及邊坡工程。一般工程設計從工址調查、設計方案選擇到施工控制都會遇到許多不確定因素，大多工程師設計時都以安全係數概括所有發生的可能性，實際上以定值來設計結構物的安全性是保守的，設計結構物之安全係數與結構物的破壞機率並不一致，而使用不確定設計觀念探討安全係數與破壞機率之關係，以破壞機率取代安全係數是未來設計的趨勢。本研究將利用不確定分析中蒙地卡羅模擬法(Monte-Carlo simulation ,MCS)，針對加勁擋土牆設計之不同土壓力假設法及破壞面形式，改變背填土之參數及加勁材之參數等，探討參數之敏感度並討論參數變化對擋土牆穩定性之影響，採可靠度之方法設計加勁擋土牆之最佳配置，希以改進安全係數設計之不足，眾觀全世界先進國家已將此設計概念作為結構物規範設計，故本研究希可提供國內規範設計修正之參考與佐證。

關鍵字

加勁擋土牆；安全係數；破壞機率；可靠度設計

並列摘要

In recent years, the number of development projects on hill slopes increases significantly in Taiwan due to the fact that Taiwan is a small island compared to its vast population. Unplanned slope developments have been the cause of many disasters. Buttressed retaining walls not only are aesthetically and ecologically beneficial, but also allow greater displacements, therefore widely used in retaining constructions and slope stabilization. There are many uncertainties for a typical construction project from jobsite survey, design selection, and all the way to construction control. Engineers introduce factor of safety in their designs to cover all possibilities that they can think of. In reality, it is relatively conservative to ensure the safety of a structure with several fixed values, as there is no solid relationship between the factor of safety used in structure designs and the probability of failure in a structure, and uncertainty design concepts, as a result, are used in the investigation of the relationship between factor of safety and probability of failure. It has now become a trend of future to use probability of failure instead of factor of safety in structure designs. The study intended to investigate the sensitivity of parameters and discuss the impact of parametric changes to the stability of retaining walls with different assumptions of soil pressure and patterns of failure planes in stiffened retaining wall designs and by changing parameters in backfills and stiffeners. Reliability methods were employed for the optimized design of stiffened retaining walls in the hope to improve designs with safety factor. Looking at many advanced countries in the world, this design concept has been adopted as exemplary structure design. Therefore, it is hoped that the study may provide a reference and justification for revision of Taiwan’s design codes.

並列關鍵字

Mechanically Stabilized Earth Walls(MSEW) ； Factor of Safety ； Probability of Failure ； Reliability Analysis

參考文獻

【3】 John T. Christian(2004).〝Geotechnical Engineering Reliability：How Well Do We Know What We Are Doing？〞Journal of Geotechnical and Geoenvironmental Engineering ,Vol. 130, No. 10, P.985-1003

【4】 G. G. Meyerhof (1970).〝Safety Factors and in Soil Mechanics,〞Canadian Geotechnical Journal, Vol. 7, No.4, pp.67-71

【7】 Tanit Chalermyanont, Craig H. Benson(2005).〝Reliability-Based Design for External Stability of Mechanically Stabilized Earth Walls,〞International Journal of Geomechanics, Vol. 5, No. 3, pp. 196-205

【8】 Tanit Chalermyanont, Craig H. Benson(2004).〝Reliability-Based Design for Internal Stability of Mechanically Stabilized Earth Walls,〞Journal of Geotechnical and Geoenvironmental Engineering, Vol. 130, No. 2, pp. 163-173

【9】 Robert V. Whitman (1984).〝Evaluating Calculated Risk in Geotechnical Engineering,〞Journal of Geotechnical Engineering, Vol. 110, No. 2, pp. 145-188

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應用可靠度分析方法於加勁擋土牆之設計初探

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