AN AGGREGATED FUZZY RELIABILITY INDEX FOR SLOPE STABILITY ANALYSIS

Abstract

While sophisticated analytical methods like Morgenstern-Price or finite element<br />methods are available for more realistic analysis of stability of slopes, assessment of the exact<br />values of soil parameters is practically impossible. Uncertainty in the soil parameters arises<br />from two different sources: scatter in data and systematic error inherent in the estimate of soil<br />properties. Hence, stability of a slope should be expressed using a factor of safety<br />accompanied by a reliability index.<br />In this paper, the theory of fuzzy sets is used to deal simultaneously with the uncertain nature<br />of soil parameters and the inaccuracy involved in the analysis. Soil parameters are defined<br />using suitable fuzzy sets and the uncertainty inherent in the value of factor of safety is<br />assessed accordingly. It is believed that this approach accounts for the uncertainty in soil<br />parameters more realistically compared to the conventional probabilistic approaches reported<br />in the literature. A computer program is developed that carries out the large amount of<br />calculations required for evaluating the fuzzy factor of safety based on the concept of domain<br />interval analysis. An aggregated fuzzy reliability index (AFRI) is defined and assigned to the<br />calculated factor of safety. The proposed method is applied to a case study and the results are<br />discussed in details. Results from sensitivity analysis describe where the exploration effort or<br />quality control should be concentrated. The advantage of the proposed method lies in its fast<br />calculation speed as well as its ease of data acquisition from experts' opinion through fuzzy<br />sets.