Abstract The paper presents a probabilistic study aimed at investigating the role of the soil hydraulic response on the stability of existing river embankments, for which the uncertainty and the inherent variability of geotechnical and hydraulic properties are typically greater when compared to new flood defence structures. The study has been carried out with reference to a specific, thoroughly investigated 20 m-long segment of the river Secchia banks (northern Italy), which experienced a catastrophic sudden failure after a period of intense rainfall, in January 2014. By taking such well-documented case as a base, the proposed probabilistic analyses consider three key aspects, typically disregarded in routine risk assessment procedures: i) transient seepage flow through earth structures due to time dependent hydraulic loads, ii) unsaturated conditions of soils forming the river embankment, iii) uncertainty of the soil model parameters, with special emphasis placed on the impact of intrinsic variability of unsaturated soil parameters. The numerical results, obtained from the application of the Point Estimate Method, allow identifying the crucial role of suction distribution on the probability of failure of the riverbank slopes and clearly show that such probability can be significantly underestimated when the variability of hydraulic parameters is neglected.

中文翻译：

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考虑非饱和土参数固有变异性的河岸稳定性可靠性分析

摘要 本文提出了一项概率研究，旨在研究土壤水力响应对现有河堤稳定性的作用，与新的防洪结构相比，其岩土和水力特性的不确定性和固有可变性通常更大。该研究参照了 2014 年 1 月在经历了一段时间的强降雨后突然发生灾难性的突然断流的 Secchia 河岸（意大利北部）的 20 米长的具体而彻底的调查。 - 以记录在案的案例为基础，建议的概率分析考虑了三个关键方面，通常在常规风险评估程序中被忽略：i) 由于时间相关的水力载荷，通过土体结构的瞬时渗流，ii) 形成河堤的土壤的非饱和条件， iii) 土壤模型参数的不确定性，特别强调非饱和土壤参数的内在可变性的影响。应用点估计法获得的数值结果可以确定吸力分布对河岸边坡破坏概率的关键作用，并清楚地表明，当忽略水力参数的可变性时，这种概率会被显着低估。