Evaluation of surrounding rock stability by optimizing Hoek-Brown criterion parameters under blasting loads

Dynamic loads due to blasting will affect the mechanical properties of rock masses and form an excavation damage zone (EDZ). The rock mass properties within the EDZ are obtained by the geological strength index (GSI) and disturbance factor (D) in the Hoek-Brown criterion. In order to avoid the subjectivity of GSI evaluation, a stochastic-deterministic 3D discrete fracture network (DFN) is constructed to quantify the GSI. The D value is considered to be a value that varies with depth within the EDZ, rather than a fixed value. Quantitative blasting vibration data is used to determine the disturbance factor rather than qualitatively estimated values. When the disturbance factor decreases linearly within the EDZ, the mechanical properties of the rock mass increase linearly to the undamaged value. Numerical simulation is used to analyze the influence of linear decrease of the rock mass properties on the stability evaluation of the tunnel. The results show that different rock mass parameters have a great influence on tunnel convergence and settlement values. The method described in this paper helps to evaluate the stability of surrounding rock more objectively and accurately.