Blastability

BLASTABILITY of the rocks (EN: explosibility of rocks, blastability of rocks; DE: Sprengbarkeit von Gesteinen; FR: explosibilite des roches; ES: explosibilidad de las rocas; RU: взрываемость) is the resistance of the rocks against the destruction under the action from the explosion of the charge of the explosive substance.

The blastability is characterized by the quantity of the standard explosive substance in the kilograms per cubic metre units (the specific consumption of the standard explosive substance), and also by the amount of the energy from the explosive substance in the joules per cubic metre units (the specific consumption of the energy from the explosive substance), which are necessary for the forming of the rectangular crater of the explosion in case of the depth for the embedment of the charge of 1 metre, within the blasthole with the diameter of 40 millimetres, which is situated at the angle of 45 degrees to the free horizontal surface.

Another method for the evaluation of the blastability is the determining of the maximal line of the least resistance (l. n. s.; RU: линия наименьшего сопротивления), in case of which the explosion of the charge of the standard explosive substance produces yet the separation of the rock from the massif, with the constant length of the charge, which is parallel to the lateral surface of the bench. In case of this method, the blastability is characterized by the dimensionless value, which is expressing the relation of the maximal l. n. s. to the diameter of the blasthole, and to the amount of the explosive substance within this blasthole.

They also evaluate the blastability, using the specific consumption of the standard explosive substance (ammonite # 6 ZhV) in grams, which is necessary for the crushing of 1 cubic metre of the monolitic rock with the shape of the cube, which is having six exposed surfaces (the freely suspended state), to the pieces with the size of 0.25 metres, in case of the placement of the charge within the centre of the cube.

They evaluate the blastability during the massive explosions at the open-pit mines, according to the calculated specific consumption of the explosive substance (kilograms per cubic metre), in case of which there is achieved the required lumpiness of the blasted mining mass.

The blastability depends on the sturdiness, toughness, elastic and plastic properties, and density of the rock, and also on the graininess, lamination, and cleavage. Within the USSR, there exists the multitude of the classifications for the rocks according to the blastability. For the large-scale breaking by the borehole charges of the explosive substance, they categorise the massifs of the rocks according to the degree of the blastability into the easy, medium difficult, difficult, very difficult, and exclusively difficult to blast. The evaluation of the blastability is used for the normalization of the labour for the mining workers, for the designing of the explosions, for the calculation of the consumption of the explosive substances, for the technology of the blasting.