This invention relates to blasting with explosives and more particularly to a blast-hole blasting method, employing a jet unit applying the shaped charge effect, to realize the ideal mechanism of the explosion and breakage analysis.
The history of blasting can be divided into the development of explosives and detonators, and the changes in their use. And so far, better blasting methods have been pursued with imagination based on observation of various phenomena.
Explosives have developed from black powder to dynamite, ANFO, slurry, emulsion, and so forth while similarly, the evolution of the electric detonator, non-electric detonator, and electronic detonator have continued since the invention of the blasting cap and detonator. Thus, the safety of explosives and the precision of the detonator have improved greatly. As for the technological progress of blasting, the blasting of the explosives charged in a blast-hole was established in the 17th century. Ensuing the observation of various phenomena, an air-deck method utilizing analytical detonation reactions was implemented, and research on a j et-powered shaped charge continued.
Of particular note, in 1893, when Knox discovered and patented that void space (air-deck) inside the blast-hole increased the efficiency of blasting charged with gunpowder. Regarding the detonator, in 1886, G. Bloem patented the formation of a hemispherical base of the detonator to increase the force of detonation.
According to the analysis of macroscopic mechanisms known to date, rocks are cracked up to 9 ms due to the dynamic and static effects of the explosion reaction. Movement of the crushed rock begins after 9 ms, and the crater production is completed in 15˜30 ms.
In addition, observation of the air-deck's microscopic mechanisms has been reported to show that shock waves within 4˜8 ms have a decisive effect on the fracturing of the rock. [Liu, L., Katsabanis P. D. (1996), Numerical modeling of the effects of air-decking/decoupling in production and controlled blasting. Rock Fragmentation by Blasting, Monhanty (ed.), Balkema, Rotterdam, pp. 319-330].
The development of the basic principle of the shaped charge began much earlier and took longer than that of the air-deck. The fundamental structure of the modern-day shaped charge (incorporating the stand-off distance starting with the observation of the cavity effect) took roughly 150 years to establish. [Kennedy, D. R. (1990), History of The Shaped Charge Effect: The First 100 Years, Defense Technical Information Center, pp. 3-14]. In the process, a number of invention patents have been proposed.
On the other hand, the detonating action of the detonator can be divided into fragments, heat, and shock waves. Regarding the detonation of cap sensitive explosives, fragments play the most important role in detonating explosives. It is reported that ammonium nitrate detonates at a distance of 1 m by the fragments in experiment.
In the jet of the shaped charge effect, a shock wave generated when the explosive is detonated and transmitted to the liner, and the collapsed liner forms the jet of high temperature and high pressure in the axial direction. The stand-off distance between the liner and the target further enhances the effect. For metal liners, the jet temperature is above 500 degrees and the speed reaches 12.5 km/s, more than twice the fragments velocity of the detonator.
In accordance with the analytical observation and practical application of drilling blasting to date, the most ideal mechanism is to complete at once, on a molecular basis, the detonation reaction of a charged explosive before the destruction of the blast-hole wall proceeds. Consequently, it is possible to complete the cracking and crushing of the blasting object by converting both the shock wave energy of the primary detonation reaction and the chemical energy of the secondary reaction product into kinetic energy. In other words, to reduce the completion time of the detonation reaction of the charged explosives, increase the degree of completeness, and induction of the shock wave emission of chemical products in accordance with the detonation reaction will lengthen the duration of the reverberation significantly.
However, concerning the current blast-hole blasting method, two factors hinder the progress of the ideal mechanism. These can be divided into the manufacturing and practical limitations of the explosives and detonators.
Regarding explosives, the explosion of slurry and emulsion explosives (which currently occupies most of the industrial explosives with superior stability compared to dynamite) have a manufacturing limitation based on the hot spot theory by adiabatic compression of bubbles. In terms of detonation, the precision and accuracy of the detonator have reached 1 ms, but its role is only fulfilled at the moment of detonation and propagation is conceptualized as being dependent on the sympathetic detonation of the loading charge.
For this reason, the explosive energy cannot be efficiently used in blast-hole blasting. There have been disadvantage phenomena such as the channel effect and dead-pressing phenomenon or deceleration and detonation failure in the case of narrow drilling pattern or deep holes, in the use of various sites such as bench blasting, tunnel blasting, and underwater blasting. In particular, the air-deck charging method is more efficient at using 10-30% of the charged explosives in theory, however, in practice, the smaller the diameter and deeper the depth of the blast-holes, the more frequently the problems occur, thus making the result less efficient than the conventional method.
Concerning this circumstance, U.S. Pat. No. 6,330,860 still does not compromise the borrowed use of the early air-deck discovery and fails to account for the loss of detonation velocity and power in sympathetic detonation. Thus, it does not necessarily provide a practical alternative, which this invention addresses. U.S. Pat. No. 5,705,768 is borrowed without developing upon the basic form of the shaped charge consisting of the existing housing, explosives, detonator, and liner. There is no use of the stand-off distance; accounting for only the concept of direction and no concept of speed. The role of the liner is also limited to only the cavity effect and not the jet effect. The use of the hemispherical liner with half the speed of the jet compared to the cone, and the jet effect using a high speed of the conical liner is also negatively taught so that it is difficult to achieve the effect of sufficient jet detonation. Kennedy's report above is reminiscent of the WASAG (1910) patent, which applied the cavity effect only to direct fracturing, as it has been continuously used ineffectively so far in blast-hole blasting. In other words, it is not the principle of the shaped charge but only part of the shape from the shaped charge.
In this method, both patents apply special phenomena from the history of blasting, each with its own limitations, suggesting opposite directions for the application and implementation of the ideal concept of blast-hole blasting. Such methods are conditioned on the limitations of explosives manufacturing according to the hot spot theory and the conceptual limits of the detonator's function, which rely on the sympathetic detonation of blast-hole blasting. In addition, the explosive energy cannot be efficiently used and the application to various blasting environments or to other charging methods such as air-decks exposes many problems.
The present invention is to provide a blasting method using a jet unit in which the shaped charge effect is applied as a method of practicing the ideal mechanism of blast-hole blasting based on the analysis of the observations described above.
In the history of blast-hole blasting, many better methods have been proposed so far, but no technical solution has been provided for the concept of ideal blasting by analysis of observations. The reason for this is that the analysis was difficult at the time of discovery of both the two phenomena mentioned above. The use of black powder and dynamite may have been the reason for no apparent need for consideration of the dead-pressure phenomena of explosives produced on the basis of the hot-spot theory or for the widespread application of the air-deck phenomenon.
Liners, spacers, and fittings are provided to make a jet unit that acts as explosives and a detonator in blast-hole blasting. The liner can be made of materials such as metal, plastic, ceramic, or glass, etc., which are capable of emitting a jet during the detonation reaction. The shape of the liner is planar, spherical, conical, etc. which can vary the speed, length and width of the cross-section of the emitted jets, depending on the intended application. Primarily, cones with a vertex angle of 40 to 90 degrees which the generatrix is straight or curved, are sufficient to induce jet emission. The spacers and fittings can be made of plastic and materials similar to plastic or environmentally friendly materials. The spacers' end portion can be shaped like the liner to support the liner or other spacers and to induce the cavity effect in the charged explosives. One side of the fittings are designed to accommodate primers, boosters, or charged explosives, while also attaching the liner in close contact, while the other side can be further extended to form a stand-off distance, and/or to accommodate explosives or spacers.
According to the predetermined plan, drill the blast-hole(s) on the object of fracture such as rock or concrete. Regarding the methods of charging the jet unit for jet detonation, one or more primers, boosters, or column charges are loaded in the blast holes; mount at least one liner to the loaded explosives for jet ignition; form empty spaces between the explosives to be used as a stand-off distance and an air-deck. The length is adjusted with respect to the strength of the rock, drilling patterns, and types of explosives. In this case, attach or mount liners using a spacer or fitting to increase workability. Double check the charge, detonate the primer, and complete propagation as the jet is released by the liner for detonation.
The jet detonation proceeds faster than the detonation of the charged explosive, and exceeds the propagation speed of the shock wave (through the air gap) between the charge and blast-hole, and the released jet fragments and its energy detonate the charges in the blast-hole rapidly. In addition, the detonation reaction of the charged explosives propagates in all directions along the axis to maximize efficiency.
As such, the jet unit overcomes the performance limits of explosives manufacturing, and the conceptual limits of detonators' functionalities, and also improves the channel effect, and dead pressing, and prevents loss of power and halt of detonation, etc. The application of controlled blasting and air-decking can be carried out without restriction while maintaining the safety of slurry or emulsion explosives.
In particular, microscopic observation of rock breakage by the air-deck charging method has proven to have a decisive impact on shock waves within 4-8 ms. Prerequisites for this are to reduce the completion time of the detonation reaction of the explosives, increase their maturity, and induce and sustain the shock waves release of chemical products following the detonation reaction. The jet unit reduces the completion time of the detonation reaction and increases the degree of completion. The stand-off distance further accelerates the speed of the jet, and combined with the proper arrangement of the air-deck, also ensures that the chemical product of the detonation reaction releases its energy as a shock wave greatly improving its reverberation.
The jet unit improves the efficiency of explosives in blast-hole blasting, thereby reducing the influence on adjacent holes during tunnel blasting and increasing the rate of excavation and being advantageous for over-break management. It also increases the productivity and workability by overcoming the effects of the detonation due to water pressure in underwater blasting and can be an essential application during controlled blasting. When applied to all blast-hole blasting, explosive efficiency can be increased to improve productivity and prevent pollution and environmental issues such as vibration and noise.
In blast-hole blasting, the explosion using the jet unit could lead to the reconsideration and change of basic design elements such as sensitivity, pressure resistance, and detonation velocity, etc., in the manufacturing method of industrial explosives. In addition to the classification of industrial explosives (which are classified currently cap sensitive and booster sensitive), it will be possible to manufacture safer jet sensitive explosives by adapting the activation energy to the jet detonation. Furthermore, it will accelerate the methods of achieving said efficiency by detonating the loading explosive at once on the molecular basis.
The configuration, operation, and applications of the present invention will be described with reference to the accompanying Figures.
As described above, detonation by the jet unit of
For jet detonation in blast-hole blasting: Firstly, the liner 150 is attached to the explosives 110, primer 111, booster 112, or column charge 113, mainly by using a straight or curved line of the generatrix of the cone to sufficiently induce the emission of the jet 170. The method of attaching the liner 150 is as shown in
Secondly, after attaching the liner 150, it is possible to induce acceleration on the jet 170 released by the liner 150 by setting the stand-off distance 160. This amplifies the detonation force of the jet 170. In the case of long-hole blasting, this has the advantage of further accelerating the detonation. In the case of the conical liner 4, the stand-off distance 160 may be applied at 2 to 8 times the diameter depending on the material to be manufactured for the penetration or cutting of the steel. Shorter or longer alterations of the stand-off distance do not interfere with the detonation of the explosives. As a simple test blasting according to the situation of the site, it can account for various variables such as the material and shape of the liner 150.
Thirdly, in the above-mentioned bench blasting, tunnel blasting, controlled blasting, underwater blasting, etc., determines the loading amount according to the working situation, attach the liner 150, set the stand-off distance 160, and then use spacer (23˜25) between the charges. By doing this, the efficiency of various blasting methods can be improved, and in particular, the air-deck method can be widely applied. Various types of liners (1˜10), fittings (11˜22), and spacers (23˜25) shown in
The above description is intended to be illustrative, not restrictive. The scope of the invention should be determined with reference to the appended claims along with the full scope of equivalents. It is anticipated and intended that future developments will occur in the art, and that the disclosed devices, kits and methods will be incorporated into such future embodiments. Thus, the invention is capable of modification and variation and is limited only by the following claims.
Number | Date | Country | Kind |
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10-2018-0126506 | Oct 2018 | KR | national |
10-2019-0078427 | Jun 2019 | KR | national |
This application is a U.S. national stage application claiming priority to PCT Application No. PCT/IB2019/058930, filed on Oct. 20, 2019 which claims priority to Korean Application Nos. 10-2019-0078427, filed on Jun. 30, 2019 and 10-2018-0126506, filed on Oct. 23, 2018, all of which are incorporated herein by reference in their entireties.
Filing Document | Filing Date | Country | Kind |
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PCT/IB2019/058930 | 10/20/2019 | WO | 00 |