Modification of Hoek-Brown criterion and evaluation of rock mass quality in tunnel vibration damaged area

Abstract

When blasting is used for excavation, blasting and stress relaxation will seriously affect the mechanical properties of the rock mass around the tunnel and form an excavation damage zone (EDZ). This paper evaluates the rock mass properties in the EDZ based on important parameters (disturbance factor) in the Hoek-Brown criterion. The blasting vibration monitoring data is used to determine disturbance factor (D). The statistical analysis of the blasting monitoring data shows that as the depth behind the tunnel wall increases, the disturbance factor also decreases, showing an almost linear relationship. When the disturbance factor decreases linearly in the EDZ range, the deformation modulus, uniaxial compressive strength, uniaxial tensile strength, cohesion and internal friction angle of the rock mass increase linearly to the undamaged value. Based on Guangzhou metro line 22, the influence of the linear decline of EDZ rock mass properties on the stability evaluation of surrounding rock is analyzed. Therefore, the development of this method is of great significance to objectively and quickly evaluate the different rock mass properties in EDZ with similar site environment and rock types.