Ways towards optimization of washout components of rock cutting tools

Large Dzheroi-Sardara phosphorite deposit occupies vast intermountain area in the Central Kyzylkum and is developed using open pit mining method (Tashkura open pit mine, Central Mine Management, Navoi Mining and Metallurgical Company). The deposit is composed of phosphorite beds I and II mined with cutter-loaders. Overburden strata are sand clay, gravelite, clay and thin phosphatized clayey marl layer and are subjected to drilling-and-blasting together with marl parting. Clayey beds have nonuniform thickness and may be 25 m thick. The nonuniformity of the overburden in type, material constitution, hardness and other characteristics requires optimized mode of hole drilling and sustained performance of rock cutting tool. The prime influence on the efficiency and endurance of rock cutting tool during hole drilling belongs to: dynamic (impact and vibration) forces conditioned by both design of the tool and improper accommodation of drilling mode to changed properties of rocks; insufficient sealing of basic parts of bits against washwater and drilling mud; level and technological efficiency of maintenance service (selection of lubricants, cleaning and trial of bits, other scheduled operations). The author points at low performance of conventional methods of washout and removal of drilling mud and other preventive treatment under conditions of alternation of different type rocks and flimsy knowledge on packing, which is highly adversive for drilling quality, especially in weak clayey rocks. The article studies ways towards improvement of rock cutting tool in the specific conditions of blasthole drilling in overburden in Tashkura open pit mine. The algorithm (scheme) of theoretical research and laboratory and full-scale testing aimed at engineering, manufacture and use of efficient anti-packing assemblies to protect roller drill bits is proposed.

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