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The authors address the problem connected with the determination of efficient rotary percussive drilling techniques with DTH hammers and present estimation criteria for their value ranges such that to ensure drilling at minimum energy content and wear of bits. The calculation formulas for drilling techniques are given, and the expediency of maximum destruction at minimum impacts per one complete turn of drill bit is proved. The upper limit of drill bit turn angle between impacts at the maximum drilling capacity and minimum energy content of fracture and wear of tungsten carbide inserts is found. The rotary percussive drilling technique with different DTH hammer models can be optimized suing the energy criterion of volumetric rock destruction and the energy content of fracture.

The interaction of an open pipe with an internal soil plug according to the Coulomb’s law of dry friction is investigated. Different soil and pipe models are considered. For all models, finite-difference solutions are obtained, for some—analytical solutions describing the process of elastic interaction of a pipe and a plug. Good agreement between numerical and analytical solutions is shown. The results of numerical calculations for different models are compared and the applicability limits of the models are determined. The effect of Coulomb dry friction on the process of pipe and plug movement is studied.

The article describes bench tests and calculations aimed to determining effect of parameters of ring-type elastic valve on variation of average pressure in the valve clearance. The results allow refinement of the design model of ring-type elastic valve and correction of the elastic ring cross-section based on the determined mechanisms.

The article describes computer modeling of three options of pneumatic percussion unit in a circular impact machine. All options have similar structure diagrams and mechanical linkage parameters but different control of energy-carrier feed in a working chamber: valveless; with one or two circular elastic valves. The obtained data allow quantitative evaluation of operation of such systems given the accepted constraints for mechanical block.