The use of high-energy shocks is most effective when working hard rocks where the scale factor is expressed more fully and a blunt rock-destructive tool (bit) can be used [i]. The crushing effect is then greater with single strokes, as compared with the total power of highfrequency shock machines [2].Using a well-drilling hydraulic hammer to drill strong rocks with a blunt bit reduces the number of trips of the drilling string and thus reduces the time of well drilling. The design of a hammer has specific features due to the limitations of well diameter and the stringent requirements for reliable operation of equipment used at a great depth.At the M. A. Lavrent'ev Institute of Hydrodynamics, Siberian Branch of the Academy of Sciences of the USSR a well-drilling hydraulic hammer with a stroke energy of 60 kJ and stroke frequency of 2-4 Hz has been designed and tested on drilling rocks of hardness category VII in a well with a diameter of 400 mm.The main features of the hammer design are the following: a hydraulic volume drive for accelerating a long and heavy striker, hydroaccumulator placed near the hydraulic drive, and control of work cycle by the kinetic energy of a resilient free-moving body.With the long striker, a long shock pulse can be produced, resulting in a uniform supply of energy to the face [3]. During the course of drilling, a rarefaction wave arises in the drilling mud simultaneously with impacts hitting the rock. When a longer striker is used, the wave exists sufficiently long to briefly reduce the hydrostatic pressure in the well, with a positive effect on the mechanical speed of drilling [4, 5].The design of the hydraulic hammer includes features for damping the face response forces, braking the striker in the absence of an obstacle to the stroke, and hydraulic brakes which prevent the destruction of colliding parts. The ratio of the weight of the hydraulic hammer to the stroke energy of 0.07 kg/J is smaller by an order of magnitude than for hydraulic hammers used to drill geologic prospecting wells [3].
