Method and apparatus for controlled small-charge blasting of hard rock and concrete by explosive pressurization of the bottom of a drill hole

A device for fracturing a hard material, comprising:

• a cartridge;
• and
• a stemming means for holding the cartridge in a hole in the material, the cartridge being located adjacent to an end of the stemming means and including:
• a cartridge base positioned adjacent to the end of the stemming means;
• and
• an outer cartridge housing attached to the cartridge base, a first portion of the outer cartridge housing containing an explosive and a second portion a space for controlling the gas pressure in the hole, wherein at least a portion of the explosive is positioned at a distance, from the cartridge base to dissipate a detonation shock wave generated during detonation of the explosive, wherein the space has a space volume and the explosive an explosive volume and the space volume ranges from about 200 to about 500% of the explosive volume.

A device for fracturing a hard material, comprising:

• a cartridge;
• and
• a stemming means for holding the cartridge in a hole in the material, the cartridge being located adjacent to an end of the stemming means and including:
• a cartridge base positioned adjacent to the end of the stemming means;
• and
• an outer cartridge housing attached to the cartridge base, a first portion of the outer cartridge housing containing an explosive and a second portion a space for controlling the gas pressure in the hole, wherein at least a portion of the explosive is positioned at a distance from the cartridge base to dissipate a detonation shock wave generated during detonation of the explosive, wherein the stemming means includes a primary inductance coil and the cartridge base a secondary inductance coil, with the primary and secondary inductance coils being electrically coupled to one another for initiating detonation of the explosive.