Harun SÖNMEZ, Candan GÖKÇEOĞLU, Murat ERCANOĞLU

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Bulanık mantık: Özellikleri ve süreksizlik denetimli bir şev duraysızlığına uygulanması

Bilgisayar destekli tasarım amaçlı mühendislik çalışmaları bir takım mantık sistemleri ve matematiksel modelleri gerektirir. Klasik sayısal analiz yöntemleri sadeleştirilmiş ve sınırları belirli sistemlerin çözümü için uygun olmasına karşın, karmaşık ve etkileşimli sistemlerin değerlendirilmesinde zaman zaman yetersiz kalabilmektedir. Özellikle mühendislik jeolojisinde kayaç ve zeminlerin dayanım parametrelerine bağlı sınıflandırılması ve bu parametreler kullanılarak bilgisayar ortamında gerçekleştirilecek bilgi temelli uzmanlık sistemi (knowledge-based expert systems) değerlendirmeleri için uygun nitelikte olan bulanık mantık yaklaşımı bu çalışma kapsamında incelenerek, süreksizlik denetimli bir şev duraysızlığı bulanık mantık yaklaşımı kullanılarak değerlendirilmiştir. Andezitler içerisinde gelişmiş olan kama türü şev duraysızlığnın analizi limit-denge yöntemiyle yapıldığında, güvenlik katsayısı 1.24 olarak elde edilmiş, duraysız bir şev için 1'den büyük olarak hesaplanan bu güvenlik katsayısının, şev geometrisi, süreksizlik konumları ve özellikle süreksizliklere ilişkin makaslama dayanım parametrelerinin kesin bir şekilde belirlenememesinden kaynaklandığı düşünülmüştür. Bulanık mantık yaklaşımı ile yapılan değerlendirmede ise duraylılık indeksi 0.31 olarak elde edilmiştir, Bu indeks değerine göre şevin duraylılığı "orta" derecede olup, kaymaya eğilimlidir. Bu iki sonuç karşılaştırıldığında, bulanık mantık yaklaşımının, yer yer olasılık yaklaşımlarının kullanımı gibi, klasik deterministik analiz yöntemlerini destekleyici biçimde kullanılmasının yararlı olacağı ortaya çıkmaktadır.

Fuzzy logic: Its attributes and application to a discontinuity controlled slope failure

This paper is concerned with the basic attributes of fuzzy logic, its possible application areas in engineering geology and a simple slope stability application. Some uncertainties are inherent to many engineering geological applications. In the literature, two types of uncertainty such as ignorance and variability are described. Some approaches such as fuzzy logic, probability theory etc. are used to minimize these uncertainties. The fuzzy logic, one of these techniques, is an effective tool to define some uncertainties sourced from ignorances and variabilities. Theoretically, fuzzy rules can be constructed based either on expert knowledge or on a set of observed or measured data. One of the most important stage of fuzzy logic approach is the construction of membership functions. The assumption underlying fuzzy logic theory is that the transition from membership to non-membership is seldom a step function. Rather, there is a gradual but specifiable change from membership to non-membership.In crisp set theory, a Membership function $(mu_a(x))$ has only two values (0 and 1). In this study, some membership functions defined in the literature were presented with their graphical illustrations. In order to demonstrate the strength and use of this approach, a conventional deterministic slope stability analysis incorporated with the fuzzy logic was performed and the results were discussed. A wedge failure occurred in the andesites was analyzed and the factor of safety was found as 1.24. However, it was concluded that this result did not reflect the actual condition. This was, most probably due to the uncertainties associated with the measurement of the shear strength parameters. Also, the stability index value was determined. According to the stability index value, the stability class of this slope is fair and the slope is prone to slide. When performing the fuzzy logic approach, the triangular membership functions were selected, because, a triangular membership function can be defined by a maximum, a minimum and a mode value. In classical geotechnical studies, if there is no statistically significant database, the use of fuzzy logic approach based on competent judgement can be accepted as an effective way to eliminate uncertainties. As a consequence, the fuzzy logic is attracting more and more attention in several research fields because it is able to tolerate a wide range of uncertainty.
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Jeoloji Mühendisliği Dergisi-Cover
  • ISSN: 1016-9172
  • Başlangıç: 1977
  • Yayıncı: TMMOB Jeoloji Mühendisleri Odası
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