Abstract:

Basing on rock scouring of nozzle jet, this paper analyzes the rock- breaking way of rock bit, the mechanism of main and auxiliary hydraulic rock breaking and the basic action and effective factors relating rock breaking. The result shows, under the conditions of current pump unit, rock bit nozzle jet has a direct rock- breaking action on mudstone,shale and coarse grain sandstone, and an auxiliary one on limestone and fine grain sandstone. The impulsive pressure of nozzle jet, the jet pulse property, the rock porosity and the developing condition of fracture are three effective factors of main and auxiliaty hydraulic rock breaking.

Key words: Bit nozzle, Hydraulic jetting, Rock breaking, Rock breaking mechanism, Jet drilling