Estimation Of Blasting Disturbance Factor For Rock Mass Slope Stability Analyses

Research on the stability of open pit slope is significant in mine production activity.Blasting is the most common and effective way for production in open pit mining engineering.However,blasting can inevitably casuse damage and disturbance to the reserved rock mass.The blast-induced damage reduces rock mass mechanical characteristics,which inflences the stability of rock slope.In this research,the theoretical analysis and numerical simulations are used to study the relastionship between fractal dimension of the rock mass and the blasting damage factor of the Hoek-Brown(HB)failure criterion,and the effect of blasting damage on the stability of rock mass slopes are also investigated.The main conclusions are summerized as following:(1)A mathematical relationship between fractal dimension of the rock mass and blasting damage factor D is established.In order to build such relsationship,firstly,a digital image box Matlab program is coded to calculate the fractal dimension of blasting damaged rock mass.Then,numerical simulations are carried out to investigate the blasting damaged rock mass mechanical parameters under various using PFC2D program.(2)The parallel layer model(PLM),which adopts a linearly decreasing D for each layer in the blast damage zone,was used with the limit equilibrium method to explore the effects of blast damage zone thickness T on the stability of open pit slopes under production blast conditions.The proposed weighting factor fT was then used in conjunction with the existing stability charts to propose a stability model for estimating the FOS of slopes with various slope geometries and rock mass properties.(3)The determination of blasting damage factor and and the slope stability of the slope of the Hangjinyu Expressway were carried out.Based on the geometrical characteristics of the outcrops of rock mass before and after blasting,the blasting damage factor is estimated form fractal dimension of rock mass using the proposed mathematical model The factor of safety and the locatation of failure surface are compared between the tradional slope model in which a single D is assigned to the whole slope and the proposed PLM model in which a decreasing D is assigned to the damaged zone rock.