AN AGGREGATED FUZZY RELIABILITY INDEX FOR SLOPE STABILITY ANALYSIS

Document Type: Research Paper

Authors

1 MEHRASHK MEIDANI, PHD STUDENT, CIVIL ENGINEERING DEPARTMENT, SCHOOL OF ENGINEERING, SHIRAZ UNIVERSITY, SHIRAZ, IRAN

2 ASSOCIATE PROF., CIVIL ENGINEERING DEPARTMENT, SCHOOL OF ENGINEERING, SHIRAZ UNIVERSITY, SHIRAZ, IRAN

3 DEPARTMENT OF COMPUTER SCIENCE, SCHOOL OF ENGINEERING, SHIRAZ UNIVERSITY, SHIRAZ, IRAN

Abstract

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

Keywords


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