M Arabani - Associate Professor, Dept .of Civil Engineering, University of Guilan, Guilan, I.R. Iran
M Pirouz - MSc. Geotechnical Engineering, University of Guilan, Guilan, I.R. Iran
B Pirouz - MSc. Civil-hydraulics, Guilan, I.R. Iran

Geotechnical investigations are performed to evaluate geologic, seismologic, and soils conditions that affect the safety, cost effectiveness, design, and execution of a proposed engineering project. Currently, advanced methods have been developed for making the best decision in site selection to prevent unnecessary costs which are very important in large construction projects. In this paper a new approach has been developed based on the Rough Set theory that was presented by Pawlak (1991), a well-known mathematician. The results of practical studies indicate that using this method for projects can reduce costs, by preventing occurrence of hazard events due to geotechnical uncertainties. The rough set method is a method to deal with geotechnical uncertainties. The Results of Rough Set theory not only provide a baseline for decision making but also insights to the problem of concern. Using simple geotechnical problems we demonstrate that Rough set theory may supply a useful means for decision making under uncertainties

Site Investigations, Data Classification, Rough Sets, Decision making, Uncertainties