Improvement of hole drilling technology for ore drawing intensification

Purpose. The improvement of hole drilling for increasing the mineral recovery ratio by ore drawing improvement through blasting. Methods. The drilling parameters were examined for rock dumps. The means of experimental drilling are drilling rig SKB-4; drill rods with a diameter of 42 mm and a length of 1.2 m; polyethylene pipes PND 63×8 and PND 70×8 with a length of 1.2 m; steel couplings for polyethylene pipes connecting; cone bits and RKS cutters. The criterion of drilling efficiency was the mechanical drilling speed. The drilling speed at different depths was measured with an axial force of 800 – 2000 kg and rotational speeds of 120, 200 and 280 rpm. Experimental drilling was carried out using the charges of two modifications. 18 experimental boreholes with a length of 300 m were drilled. Findings. The article confirms possibility and practicability of simultaneous hole drilling and pipe casing without transmitting torque loads on the pipes and offers a design of a drill string with hoses inside drill rods and their further pulling up, and piping with simultaneous drilling. The scheme of interaction of blastholes and pipe casing when hole boring in broken ores is made. The nature of the relationship between the speed of penetration of vertical and horizontal holes with the change in the axial force and their length for different modifications of the drilling tool is studied. Originality. The new laws of change in the hole drilling penetration speed depending on the complex of technological parameters of drilling are obtained. The authors offer a model describing the possibility of hole drilling in the broken massif as well as an optimized design of the string necessary for that. Practical implications. The obtained regularities determine mechanical and energy drilling indexes and which are necessary at the stage of designing when deciding upon practicability of extraction of in-situ left ores while enhan-cing mining technologies of ore drawing.