Design and application of experimental apparatus for rock breaking by rotary percussion

Rotary percussion drilling technology is one of the ways to increase drilling rate in deep wells and super-deep wells. Practice shows that bit pressure, bit speed, impact force and frequency are the critical parameters which affect the rock breaking efficiency of rotary percussion drilling. Optimization of rotary percussion drilling parameter can help improve rock breaking efficiency of percusson impactor. A new type of rotary percussion rock-breaking experimental apparatus was designed, which uses the impact of tooth-like vibrating sleeve to produce impact load and drive the bit to break rocks using geological drilling rig. Measuring experiment shows that the impact load of this apparatus is affected by the amount of spring compression, the impact frequecy is the product of the number of sleeve teeth and rig rotating speed, the percussion process is stable and effective and that the percussion parameters correspond well with various rotary percussion drilling conditions on site. Rotary percussion rock-breakig experiment shows that the rotary percussion drilling technology can remarkaly increase the rock-breaking rate, improve the amplitude of impact load and increase the rock-breaking rate of the bit. There is a optimum bit pressure for rotary percussion drilling technology, so bit pressure should be optimized when different types of inpactors are used to drill different formations. Studying the effect law of rotary percussion drilling parameters on rock breaking rate using this experimental apparatus helps design and optimize the performance parameters of rotary percussion tools.