Abstract: According to the geology of a gold deposit, rock quality evaluation was done on unstable tunnel by using fuzzy optimal classification method. The stability of surrounding rock mass of tunnel could divided into three zones: safety zone, dangerous zone and unstable zone. The RQD was 87%, 78% and 57%, respectively, Rc was 240.1、137.1 and 85.4MPa, respectively, Fuzzy optimal classification method confirmed that surrounding rock mass stability at safety zone was Ⅲ. And dangerous zone was between Ⅲ to Ⅳ and unstable zone was Ⅳ. On the basis of this, reinforcement scheme of dangerous and unstable zone were optimized by using fuzzy multiple objectives decision making, and it was verified by using numerical simulation method. The reinforcement effect was analyzed. It can provide a certain scientific basis for further field construction.

Key words: Optimal classification method, Rock mass quality, Fuzzy multi-objective decision making, Numerical simulation