Abstract: When an underground engineering opening is excavated, a zone of disturbance in the surrounding rock mass will be formed due to the unloading effect, blasting vibration and other construction activities. Different zones might have different influence when the back analysis id performed and this different influence should be considered. Zoning back analysis method for the rock mass design parameters is proposed based on the different degrees of rock mass disturbance in underground caverns. A case of providing the rock mass parameters for Gongguoqiao Hydraulic Electricity project is presented in this paper. The cross sectional construction monitoring for the underground rock cavern was used for the back analysis. The back calculated rock parameters were used in the finite element analysis. It is concluded that the deformations of the calculated are within 7% of the observed values.

Key words: Underground Rock Caverns, Disturbed Zone, Parameters of Surrounding Sock Mass； Zoning Back Analysis