RESEARCH AND ANALYSIS OF THE MODE OF DETONATION WAVES IN BOREHOLE CHARGES WITH AN AXIAL AIR CAVITY

ABSTRACT

In this article, the main purpose of presenting the methodology for studying the explosion of charges with axial air is the detonation of an explosive charge in a well with an axial air gap under the action of initial detonation and the production and application of high-speed propagating detonation waves. .

АННОТАЦИЯ

В данной статье основной целью изложения методики исследования взрыва зарядов с аксиальным воздухом является детонация заряда ВВ скважины с аксиальным воздушным зазором под действием начальной детонации и получение и применение высокоскоростных распространяющихся детонационных волн. .

Keywords: mine, mine service life, production capacity, gross excavation, ore bodies.

Ключевые слова: Скорость детонации ВВ, плотность, ударная волна, микро электродетонатором, перебур.

When describing the action of borehole explosive charges, the main attention is paid to the process of development of detonation waves, which is quite fully described in [1-5].

Based on the theoretical and experimental studies of N. Vanderberg, A.I. Golbinder, L.V. Dubnov, N.A. Deremin, V.P. Martynenko, V.F. Tyshevich, L.D. Khotin, A.R. Chernenko et al. [6-7,8] studied the mode of detonation waves in explosive charges with an axial air cavity.

Let us consider the detonation of borehole explosive charges with an axial air cavity, the scheme of which is shown in fig. 1.

Figure 1. Scheme of detonation of borehole explosive charges with an axial air cavity: dс – borehole diameter; d0 - diameter of the axial air cavity;Vd - detonation velocity; ώ - air wave speed

Under the influence of the initial pulse, the borehole explosive charge with an axial air cavity is detonated, forming detonation waves propagating at a speed D. As a result of the detonation wave products, a kind of gas piston is formed in the gap between the charge - the axial air cavity, with a speed ω. According to the general laws of gas dynamics, the shock wave arising in the channel should be characterized by a higher speed than the speed of the gas piston.

Due to the occurrence of a channel shock wave of a borehole charge ahead of the detonation front, the substance is compacted, especially from low-density explosives. As a result of the compression wave propagation through the substance from the surface of contact with the shock wave in the elongated charge, a conical compaction area arises, its base sticking to the detonation wave front, the degree of deformation of the borehole charge, in addition to the physical properties of the explosive, depends on the length and pressure of the shock wave, which is confirmed in the work authors [6].

The studies by the authors of [7, 8] of the channel effect using X-ray pulse photography also showed that the substance is compacted ahead of the detonation, and the cross section is reduced. Seals across the cross section and along the length of the charge is uneven. The X-ray pattern allows us to conclude that a shock-air wave propagates through the gap, and in all cases, in its initial section ω>D.

To confirm the hypothesis that not detonation products, but a shock wave move in the gap with a velocity ω, experiments were performed in a rarefied atmosphere. When the air pressure in the tube was reduced to 1.33 kPa in PZhV-20 ammonite, the detonation attenuated in a section approximately twice as large as in experiments at atmospheric pressure. This is a consequence of the decrease in pressure in the channel, which causes the compaction of explosives ahead of the detonation front, which is associated with a decrease in the amplitude of the wave propagating through the rarefied atmosphere.

Thus, in the axial air cavity of the borehole explosive charge, a shock air wave of a rectangular profile propagates, leading the detonation front, the scheme of which is shown in Fig.1.

By the time the formation of the shock front is completed, the velocity of propagation of the shock-air wave ω can be expressed as a function of the detonation velocity D, based on the general gas-dynamic dependences:

                                     (1)

where k is the air isentropic index; ρ, ρ₀ - respectively, the cross-sectional area of the borehole charge and the axial air cavity, m²; - speed of the gas piston, m/s.

In this case, the value of u_d is equal to the velocity of propagation of the detonation wave. The pressure at the PV-air interface can be taken approximately equal to the average PV pressure in the charging chamber, which is determined by the formula:

                                             (2)

where ρ_ch is the loading density in the tube; α - PV covolum.

Then:

                                                (3)

At high loading density, i.e. with a small ratio of the cross-sectional area of the borehole charge to the cross-sectional area of the axial air cavity , the maximum speed of the shock - air wave is:

Assuming that the air isentropic index for air equal to k=1.5, we obtain the formula for calculating the speed of the shock-air wave according to the formula:                          

ω=1,25D, m/s.                                                                  (4)

Conclusion

In summary, the main purpose of presenting the technique of studying the explosion of well charges with an axial air gap is to detonate the explosive charge of the well with an axial air gap under the influence of the initial impulse and generate detonation waves that propagate at high speed together with making, it is to increase the efficiency of the well during the blasting process.

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