Blasting works

BLASTING WORKS (EN: blasting, shotfiring; DE: Schießarbeiten, Schießen; FR: travaux à l'explosif; travaux dus au tir; ES: trabajos con explosivos; RU: взрывные работы) is the totality of the operations for the preparation and initiating of the charges of the explosive substance. They use the blasting works mainly within the mining craft, and within the construction (see the "Explosive technology" article). They conduct the blasting works under the condition of the provision of the safety for the workers, equipment, built structures, and environment.

The preparatory stage of the blasting works is the selection of the personnel, the registration of the documents for the right of the purchase, storage, and transportation of the explosive materials, and for the right of the conducting of the works. The blasting works proper include the composition of the project for the explosion, or of the passport for the drilling-blasting works, the preparation of the explosive materials for the consumption, the delivery of these explosive materials to the place of the explosion, the production of the live cartridges, the loading and tamping of the charges of the explosive substances, the installation of the explosive network, and the initiating of the charges. The concluding stage of the blasting works comprises the inspection of the place of the explosion, and, in case of the uncovering, the liquidation of the remaining parts of the unexploded explosive materials, and of the failed charges.

For the detonation of the charges of the industrial explosive substances, they use various methods for the initiating, which they categorize thusly: depending on the means, which are used for the detonation, namely, the fire detonation, the electric-fire detonation, and the electric detonation; depending on the magnitude of the interval of the delay between the explosions of the individual charges within the series, namely, the instantaneous blasting, the delayed blasting, and the short-delay blasting; depending on the peculiarities of the positioning of the charges, namely, the single row, and the multiple rows; depending on the purpose of the explosion, namely, the major (primary) blasting, as the result of which the part of the massif is separated by the explosion, and is crushed, the secondary blasting, namely, the blasting of the large (substandard) pieces of the rock, which have been formed after the major blasting, the blasting of the protrusions and canopies on the bench, and of the congestions of the ore during its release from the chambers; for the ejection, and for the dumping, during the construction of the dams, canals, and foundation pits.

The personnel, and the storage of the explosive materials. The blasting works may be performed by the persons (by the engineering-technical workers, and by the labourers), who have passed the special training for the blasters, and who are having the "Unified book of the blaster (of the master-blaster)". For the performance of the auxiliary operations (the carrying of the explosive substances, the loading of the explosive substances during the transportation, and so on) during the conducting of the blasting works, there may also be involved the labourers, who have the qualifications of the drillers, and of the auxiliary occupations (locksmiths, repairers, electricians, riggers, and others), who must be instructed and warned in writing about the peculiarities of the operations with the explosive substances. The preparation and performance of the explosion are performed under the governance of the persons of the technical supervision. There are admitted to the governance over the blasting works the persons, who have the completed higher or secondary education, or who have graduated from the special courses, which are providing the right for the governance over the mining and blasting works. The storage of the explosive materials is performed at the basis storage depots of the explosive substances, and at the stationary or movable consumption storage depots of the explosive materials.

The designing of the explosions. During the performance of the explosions at the open-pit mines and underground mines, there is composed the project, which is approved by the chief engineer, where are listed the properties of the block of the rock or ore, which should be blasted, the parameters of the positioning of the boreholes, and of the structures of the charges within these boreholes, the method and scheme for the initiating of the charges, the calculated results of the explosion, and is listed the consumption of the explosive materials. There are also listed within the project the plan of the block, which should be blasted, the result of the testing of the charges for the seismic safety, the radius of the dangerous zone because of the dispersion of the pieces, and because of the action of the aerial wave, the table for the calculation of the charges within each borehole, the procedure of the massive explosion, where are listed the persons, who are personally responsible for the event, and the time for the conducting of this event, and also the scheme and procedure for the guarding of the dangerous zone of the explosion. There is composed by the mine surveyor the document about the acceptance of the block for the explosion.

In case of the usage of the blasthole, external, and small-chamber charges, there is composed the passport of the drilling-blasting works (in case of the other methods, the projects of the works), within which there are listed the general facts about the place for the work, and the characteristic of the rock, which should be blasted, the facts about the drilling equipment, about the quantity and positioning of the blastholes, about the required quality of the explosion, about the method for the conducting of the blasting works, about the method for the detonation, about the parameters of the charges and their positioning, about the calculation and scheme of the blasting circuit, the calculated parameters of the explosion (the consumption of the explosive substances, of the means for the initiating, the yield of the rock, and so on), there are listed the measures for the safety (the calculation of the radiuses for the dangerous zones because of the seismicity, because of the dispersion of the pieces, the scheme for the cordoning, the procedure for the sending of the signals, and so on). There are attached to the passport the situative plan with the drawing of the places for the blasting works, of the positioning of the signaling masts, of the block-posts for the cordoning, of the barriers, dugouts, boundaries of the dangerous zone, and so on; the scheme for the positioning of the charges, and the scheme of the blasting circuit.

The technological cards, which are given to the immediate performers of the works, contain approximately the same facts, as within the passport, but unlike the passport, these cards are composed on the basis of the project, and are not the independent projecting document. After the explosion, and after the removal of the rock mass, they input the actual results into the project of the massive explosion.

The preparation of the explosive materials for the usage, and the production of the live detonators, are such, the verification of the suitability of the explosive substance, and of the means for the initiating. They slightly dry the free flowing and cartridged explosive substances, which have the increased humidity. They grind the caked explosive substances, up to the imparting to them the initial state. The blasting caps, safety fuses and detonating cords, and short-delay retardants for the detonating cord, are subjected to the external examination, while the electric detonators are verified using the instruments. The preparation of the explosive substances, which are produced at the mining enterprise of the components (igdanites, ifzanites, carbatoles, and so on), includes the delivery and preparation of the initial components (or of the explosive substances) at the points for the preparation of the explosive substances. In case of the fire detonation, they make the incendiary tubes within the special enclosed indoor space at the storage depot for the explosive materials. They produce the live detonators within the special enclosed indoor spaces at the consumption storage depots for the explosive materials, or within the places for the explosion before the start of the charging.

The process of the charging includes the preparatory stage, namely, the successive operations for the loading of the explosive substances, and for the delivery of these substances to the place for the charging, the operations for the preparation (unpacking, kneading, and others), and the charging proper, namely, the introduction of the determined quantity of the explosive substance into the charging cavity, and the introduction of the live detonator for the initiating of the charge of the explosive substance, which is performed manually or with the usage of the mechanisms (for the free flowing granulated and water-containing explosive substances). In case of the comprehensive mechanization of the charging, all the operations with the explosive substances for the loading-unloading works, from the railway wagons to the storage depot for the explosive materials and further, are performed with the help of the mechanisms. For the large open-pit mines and underground mines, there have been developed several schemes for the comprehensive mechanization of the blasting works, and there has been designed the necessary equipment: the loading and unpacking machines and mechanisms, the transporting-charging and mixing-charging machines, and the mixing devices. Under the underground conditions, for the mechanized charging of the blastholes and boreholes with the diameter of up to 100-150 millimetres with the granulated explosive substances, they use the chambered ejecting chargers and so on, and for the cartridged explosive substances, they use the pushing and throwing chargers. During the process of the charging, they place one (the blasthole and attached charges) or two (the borehole and chamber charges) live initiating detonators into each charge of the explosive substance. The live detonator is introduced into the charge as the last thing (the direct initiating), or as the first thing (the reverse initiating). In case of the blasting of the water-flooded boreholes, they dewater these boreholes preliminarily, and they use the water-resistant explosive substances, or they place the charge into the water-resistant shell. Without the preliminary dewatering of the water-flooded boreholes, they conduct the charging using the small portions of the explosive substances, in order to exclude the forming of the bung on the surface of the water, or they charge the explosive substances, while placing the charge into the polyethylene. Within the underground mines, which are dangerous because of gas and dust, there is sent simultaneously into the blasthole the complete calculated charge of the safety explosive substance, whic h is comprising several cartridges, in order to exclude the possibility for the forming of the intervals of coal or rock between the cartridges.

The tamping is the labour-consuming operation, and, in case of the significant quantities of the blasting works, they mechanize this operation (in case of the small quantities, the tamping is usually performed manually). At the open-pit mines, they perform the tamping using the special tamping machines. Within the underground coal mines (especially within the mines, which are dangerous because of gas and dust), the usage of the tamping is obligatory, and its length is regulated with the character of the stope, and with the depth of the blastholes.

The installation of the blasting circuit, and the initiating of the charges. In case of the electric detonation, the terminal wires from the electric detonator, with the help of the local and trunk wires, are connected together into the blasting circuit, later they verify the validity of the blasting circuit using the instrument, they connect the ends of the trunk wires to the source of the electric current, they send the alarm signal, and they activate the electric current. In case of the detonation using the detonating cord, they attach its ends, which are extending from the charges, to the trunk cords. After the visual inspection of the circuit, there are connected to the end of the trunk two blasting caps or two electric detonators, the circuit is verified, there is sent the alarm signal, and the safety fuse is ignited, or the electric current is switched into the blasting circuit. Within the USSR, in case of the fire detonation, the installation of the circuit is not performe d, and each segment of the safety fuse, which is coming from the charges, is ignited and exploded separately. In case of the electric-fire detonation, the ignition of the segments of the safety fuse, which are going to the charges, is performed using the electric igniters, which are installed into the electric circuit. The simultaneous ignition of several segments of the safety fuse (5 and more) is performed using the small cartridges for the grouped ignition.

The inspection of the place of the explosion is performed after the interval of time, which has been specified according to the rules, but not earlier, than the completion of the airing. The blaster (the master of the explosion) visually determines the possibility for the admission of the workers and mechanisms for the work, removes the dangerously hanging pieces within the stope, verifies the absence of the failed charges, and of the remained parts of the unexploded explosive materials. In case of the absence of the failures, there is sent the all-clear signal. In case of the uncovering of the failures, they perform the works for the elimination of these failures, during which there is prohibited the performance of other works, and the admission of the workers into the stope. They eliminate the charges, using the method for the repeated detonation of the failed charge; using the penetration of the parallel blastholes, boreholes, or chambers, and using the blasting of these workin gs for the unsealing, and subsequent destroying of the charges; using the extraction of the charge.

The occupational safety during the blasting works includes the system of the organizational and technical measures, which are aimed at the prevention of the impacts of the harmful and dangerous productive factors onto the workers. There belong to the organizational measures the education of the workers about the safe methods and techniques for the works; the usage of the protective means; the development and introduction of the instructions, and means for the propaganda, the strict compliance with the technology for the works, with the regulations for the labour, and so on. The technical measures comprise the development of the safe technology for the processes, and of the implements, which have been created on the basis of the norms and rules, which are specifying the safe and harmless conditions for the labour during the operating and repairing. The blasting works are distinguished with the increased danger, therefore, within the USSR, these works are performed in the strict acc ordance with the "Unified safety rules during the blasting works" (the first "Temporary rules about the usage of the explosive materials during the mining works" have been published within Russia within the 1st volume of the "Mining Journal" during the 1880), with the technical rules for the conducting of the blasting works under the different conditions, and with the departmental instructions, which have been coordinated with the organizations of the Gosgortechnadzor of the USSR (RU: Госгортехнадзора СССР; the Governmental Mining Technical Supervision of the USSR). These rules are perfected and supplemented in association with the complication of the conditions during the extraction, with the development of the new explosive materials and techniques for the blasting, and these rules are regularly re-published as the codex of the laws, which are obligatory for the ministries and departments within the USSR, which are conducting the blasting works.

The permissive documentation. For the conducting of the blasting works, within the organizations of the Gosgortechnadzor of the USSR, and of the Ministry for the Interior Affairs of the USSR, they register the permissions for the storage, purchase, and transportation of the explosive materials, and also for the conducting of the blasting works. The obtainment of the permissions is performed in accordance with the "Instruction about the procedure for the storage, usage, and accounting of the explosive materials", and with the "Instructions about the procedure for the obtainment of the permissions for the right of the performance of the blasting works, and also of the certificates for the purchase or transportation of the explosive materials", which are published within the annexes of the active "Unified safety rules during the blasting works".