APPLICATION OF FUZZY SET THEORY IN EVALUATION OF SOIL COLLAPSE POTENTIAL

• Published in: Iranian journal of science and technology. Transactions of civil engineering 2011-08, Vol.35 (C2), p.271-271
• Main Authors: Momeni, M, Shafiee, A, Heidari, M, Jafari, M K, Mahdavifar, M R
• Format: Article
• Language: English
• Subjects: Assessments; Categories; Civil engineering; Criteria; Decision trees; Fuzzy logic; Fuzzy set theory; Fuzzy sets; Geological engineering; Geology; Geotechnics; Laboratories; Linguistics; Set theory; Soil (material); Soil erosion; Studies
• ISSN: 2228-6160

Abstract- Collapsible soils have considerable strength and stiffness in their dry natural state but settle dramatically when they become wet. This paper documents a low-cost, qualitative evaluation scheme using fuzzy set analysis to determine regional collapsibility based on subjective knowledge of the geological and geotechnical conditions and their uncertainty. The geological and geotechnical factors and their category were defined based on relevant literature. Each factor and category was then weighted or rated using linguistic terms developed from expert assessment. The linguistic data or information obtained from the assessments was represented and processed using fuzzy sets. To assess the criteria, 87 collapse potential tests were performed on undisturbed soil samples gathered from 27 different locations throughout Iran. It is shown that the geotechnical criteria predict soil collapsibility much better than the geological criteria. Collapsible soils are generally characterized by the sudden and substantial decrease in volume that occurs when subjected to inundation under constant stress [1-2]. Collapsible soils are found throughout the world, particularly in semi-arid and arid environments [3]. Geological environments where collapsible soils can be found are colluviums, mudflows, alluvial fans, residual soil and Aeolians [4]. The identification of collapsible soil involves laboratory and/or field response-to-wetting testing [1-3]. Owens and Rollins [4] also used geological criteria to prepare a collapsible soil hazard map. However, there are no standard or unique geological criteria by which one can distinguish collapse susceptibility on a regional scale. There is abundant literature on the determination of soil collapse potential; however, it is rare to find references that directly address all factors contributing to it. The present paper categorizes geological and geotechnical factors contributing to soil collapsibility on a regional scale. For each factor, subcategories were defined based on literature. Each factor and category was then weighted or rated using linguistic terms developed from expert assessment. The linguistic data or information obtained from the assessments was represented and processed using fuzzy sets. To evaluate the criteria, 87 collapse potential tests were performed on undisturbed soil samples gathered from 27 different locations throughout Iran. It is shown that the geotechnical criteria predict soil collapsibility much be