Theoretical and experimental studies on relationship between working parameters of cone drill and rock strengths

The relationship between operating parameters of cone drill (drilling speed, drill pipe axial force, rotational speed) and rock mass strengths (cohesion, internal friction angle) is established by means of theoretical analysis and field tests based on the single-tooth impact and pressure rock fragmentation mechanisms. The geometrical morphology of broken area by single-tooth is obtained, and the relationship among single-tooth rock fragmentation volume, drill pipe axial force, cohesion and internal friction angle is established based on the Boussinesq elasticity solution and D-P plastic criterion in theoretical analysis. The relationship among single-tooth rock fragmentation volume, drilling speed and rotational speed established by the relationship that the accumulation of single-tooth rock-breaking volume and the macro rock volume is equal when the drill pipe rotates a circle. The results of theoretical analysis show that the fractured area basically exbibits ellipsoid and a thin layer in the surface layer under the single-tooth pressure. The relationship between drilling speed and rotational speed is linear, that between drilling speed and drill pipe axial force is 3/2 power, and that between drilling speed and cohesion is -3/2 power. The influence of internal friction angle on the penetration rate can be ignored. Field tests on the drilling law of conedrill are conducted in the south mining area of Anqian Mine, and the relationship among drilling speed, drill pipe axial force, rotational speed and cohesion is obtained. The theoretical analysis and the actual measurements coincide fairly well. The research achievements may provide a basis for the optimization design of working parameter of conedrill and dynamic tests on rock mass strengths.