Rock-quality designation(RQD) plays a significant role in rock mass analysis and is an important parameter in geotechnical and geological engineering.However,the RQD variation with scanline length has not yet been comprehensively considered in RQD.In this study,three-dimensional fracture network modeling was used to simulate actual rock mass,and numerous scanlines were set in the fracture network for investigation on RQD variation.Models and equations(i.e.,models A-A,N-N,and A-A-S,as well as the Priest-Hudson and Sen-Kazi equations) were summarized for the study.A corrected equation was proposed to eliminate the errors from using the Priest-Hudson and Sen-Kazi equations.In addition,inhomogeneous and anisotropic features were investigated,and the optimal thresholds for RQD calculation were determined,which varied with the study orientation and rock mass feature.When the inhomogeneity was studied in the x direction,the optimal threshold was found to be 4 m.When anisotropy was studied,the optimal threshold was found to be 3 m.
The critical slip surface of a fractured rock slope tends to extend along the fractures.Thus,fracture orientation plays a critical role in determining the critical slip surface.Based on fracture orientation data,this paper examines the critical slip surfaces of fractured rock slopes.Given that the surface of a fractured rock slope extends along the fracture surfaces,or the wedges,with each composed of two arbitrary fractures,the critical slip surface is determined via stochastic dynamics.In addition,a fracture frequency method is proposed as a means of analyzing the critical slip surface.According to this method,the critical slip surface slips in whichever direction has the lowest fracture frequency.Based on the stochastic dynamics method and the fracture frequency method,the critical slip surface of the slope is finally determined,that is,the critical slip surface takes the form of a plane passing the slope toe with a dip of 120° and a dip angle of 45°.
