Abstract: Hydraulic fracturing is a key preconditioning approach in block caving mining of hard-rock metal mines,however, natural fractures within the orebody tend to limit the oriented fracture propagation and spatial morphology of artificial fractures. To understand the influence of the natural fracture′s length and horizontal distance on the propagation path of oriented fracture within copper orebodies with natural fractures,a finite element numerical model embedded with pore pressure cohesive elements was established using ABAQUS,and hydraulic fracturing behaviors was simulated under variable natural fracture lengths and horizontal distance conditions. Results show that the length and horizontal distance of natural fractures lead to a positive effect on the propagation morphology and propagation law of fractures. The natural fracture length has an exponent relation to the propagation radius of artificial fractures,while the horizontal distance of natural fractures shows a linear relation with the propagation radius of hydraulic fractures. Regarding 0~1. 5 MPa low in-situ stress difference,with the decrease of natural fracture horizontal distance,or with the increase of natural fracture length,the propagation radius of hydraulic fracture is larger, and other response laws of hydraulic to natural fracture. The study results have a possitive guilding significance for the directional propagation and control of hydraulic fractures under the condition of hard rock natural fractures.

Key words: cohesive element,fracture propagation,natural fracture,hydraulic fracture,porosity evolution