APPLICATION OF FUZZY GSI SYSTEM FOR ESTIMATING STRENGTH OF JOINTED ROCK MASSES - A CASE STUDY FROM EASTERN ALBORZ COALFIELD, IRAN

Characterization of rock masses is one of the fundamental aspects of rock engineering. Particularly, as a rock mass characteristic, determination of the strength of jointed rock masses is difficult since the size of representative specimens including discontinuities is too large for laboratory testing. This problem can be overcome by using the Hoek-Brown empirical failure criterion in conjunction with the Geological Strength Index (GSI) classification system. However, characterization of rock masses and determination of their strength may involve some uncertainties due to their complex nature. The fuzzy set theory is one of the tools which handle such uncertainties. In this study fuzzy GSI System used for estimation of peak strength of the eastern Alborz coal basin. For this purpose, joint sets condition has taken using field observation and Scanline method. Resulted data analyzed with Dips 2.0 and RocLab 1.0 software packages. The fuzzy GSI results have a good adaptation with laboratory test.