RU2500889C1 - Electrodischarge destruction method of solid materials - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: electrodischarge destruction method of solid materials involves formation of a bore pit in solid material, arrangement in it of a cartridge containing a substance that transmits an air blast and a blasting conductor, and initiation of a discharge with the blasting conductor. Cartridges are made from plastic material with acoustic stiffness close to acoustic stiffness of destructible material. Blasting conductor is pressed into cartridge material. Polyethylene or plasticine is used as plastic material.

EFFECT: improving destruction efficiency of mine rock and utilisation of concrete and reinforced-concrete units and structures.

3 cl, 1 tbl, 3 dwg

Description

The invention relates to the mining and construction industries, in particular to the destruction of rocks and artificial solid materials using high-voltage pulsed discharges, and can be used to destroy oversized fragments of strong rocks in stone quarries, for sinking vertical inclined mine workings of a relatively large diameter, for disposal of concrete and reinforced concrete blocks, structures, etc.

A known method of destruction of rocks by electric current [SU No. 878934, IPC E21C 37/18, publ. 11/07/1981], in which pulses destroying the rock are supplied from the electric pulse generator to electrodes brought into contact with the rock, while the space in which the electrodes are installed is hermetically isolated from the rest of the volume and filled with gas before the pulses are supplied, electric strength which is higher than the electric strength of air, for example, with SF6 gas. The main disadvantage of this method is its low productivity and technological complexity, because it requires tight insulation of the electrode space and destruction occurs only between the electrodes superimposed on the rock surface, to a depth of not more than 1/3 of the interelectrode gap.

Known electro-hydraulic method of destruction of rocks and other solid materials [US No. 4479680, IPC E21C 37/18, publ. 10.30.1984], including the formation of a borehole on the surface of a solid material, filling it with liquid and placing an exploding conductor in it in a circuit with a capacitor device. During an electric explosion of a conductor, the shock wave is transferred by the liquid into the solid material in the form of a compression strain pulse, which propagates through the solid material until it is reflected from the free surface in the form of a tensile strain pulse, the tensile strain pulse mentioned being consistent with the strength of the solid material on stretching causes its local destruction. The disadvantage of this method is the difficulty in placing the fluid in horizontal and ceiling holes.

Partially indicated disadvantage is eliminated in the method of destruction by electric discharge selected for the prototype [EP 0858874, IPC B28D 1/00; E21C 37/18, publ. 08/19/1998], including the formation of a hole in the solid material, the placement of a cartridge in it in the form of a vessel with a shock wave transmitting liquid and an exploding conductor placed in it, and initiating a discharge by an exploding conductor. As a shock wave transmitting fluid, for example, water is used.

A common drawback of the previous two methods is the low coefficient of transfer of discharge energy into a solid material, since a liquid with a relatively low acoustic stiffness (1.5 ... 1.8 · 10 ⁶ kg / m ² s, which reduces the efficiency of transmission of pressure waves, and ultimately the destruction efficiency.

The objective of the invention is to provide an effective method for the destruction of building structures and structures, oversized fragments of strong rocks and other solid materials.

The technical result achieved by the proposed method is to increase the efficiency of rock destruction and utilization of concrete and reinforced concrete blocks and structures, spallation onto a free surface during tunneling and tunnel expansion by increasing the amplitude and reducing the energy losses of the shock wave due to refraction and reflection.

The specified technical result is achieved by the fact that in the method of electric discharge destruction of solid materials, in accordance with the prototype comprising forming a hole in a solid material, placing a cartridge in it with a substance delivering a shock wave and an exploding conductor, and initiating a discharge by an exploding conductor, in contrast to the prototype, in quality the shock wave-transmitting substance uses a plastic material with acoustic stiffness close to the acoustic stiffness of the material being destroyed.

It is advisable to use polyethylene as a plastic material.

It is advisable to use plasticine as a plastic material.

The effectiveness of the transmission of a shock wave from the discharge channel to the material to be destroyed depends on the consistency of the acoustic stiffnesses of the substance transmitting the shock wave (transmission medium) and the material being destroyed.

The use of a plastic transmitting medium, for example, polyethylene, plasticine, allows to increase the amplitude of the shock wave by limiting the area of the discharge burning (capillary discharge) [Marshak IS, Doinikov AS Pulsed light sources. - M .: Energy, 1978. -478 p.].

The invention is illustrated in figure 1, which shows the design of an electric blast cartridge for rock destruction, figure 2, which shows a diagram of electric blast destruction and figure 3, which shows the dependence of the energy introduced into the discharge channel from time to time for different transmission media.

The table shows the efficiency of transmission of shock wave energy from a discharge channel to a solid material, depending on the properties of the transmission medium and destructible solid material. Efficiency was calculated by the formula of refraction:

$$T=\frac{\mathrm{four}\cdot {\rho }_{\mathrm{one}}\cdot c_{\mathrm{one}}\cdot {\mathrm{<figure-callout\; id="2"\; label="\rho "\; filenames="00000003.png,00000004.png"\; state="\{\{state\}\}">\rho </figure-callout>}}_2\cdot c_2}{{({\rho }_{\mathrm{one}}\cdot c_{\mathrm{one}}+{\mathrm{<figure-callout\; id="2"\; label="\rho "\; filenames="00000003.png,00000004.png"\; state="\{\{state\}\}">\rho </figure-callout>}}_2\cdot c_2)}^2},(\mathrm{one})$$

where T is the shock wave transmission coefficient;

ρ ₁ , s ₁ - density kg / m ³ and the speed of sound m / s transmission medium;

ρ ₂ , c ₂ - density kg / m ³ and the speed of sound m / s destructible material.

The choice of plastic material as a shock-wave-transmitting medium is due to its high acoustic rigidity and ductility. This avoids significant energy losses due to overgrinding due to the formation of cracks in the near-channel region and increases the wave energy transmitted from the discharge channel to the material to be destroyed by ~ 20 ... 25%. The table shows that polyethylene most effectively transfers wave energy.

The figure 1 shows the design of an electric explosive cartridge for the destruction of rocks, where 1 is the transmission medium, 2 is the exploding conductor, 3 are the electrodes.

The figure 2 presents a diagram of an electric explosion. In the electric energy storage device, the resistance r _z and inductance L are made up, respectively, of the resistance and inductance of the capacitor bank C, switch S, connecting busbars and supply cable 4. In the material to be destroyed 5, a cartridge 6 is placed in the form of a cylinder made of transmission medium 1 (for example , polyethylene, plasticine), the axis of which is placed exploding copper conductor 2. Conductor 2 through the electrodes 3, the inlet cable 4 and the switch is connected to a capacitor bank. At the moment the switch operates, the capacitor battery begins to discharge through the conductor, which leads to its explosion and the formation of a metal low-temperature plasma with a particle concentration of 10 ¹⁹ ... 10 ²¹ cm ^-3 and a temperature of 10 ³ ... 10 ⁴ K. After the formation of the discharge channel, the accumulated in the capacitor bank energy is released into the plasma. Power, in this case, can reach hundreds of MW [Krivitsky E.V. The dynamics of electric explosion in a liquid. - Kiev: Naukova Dumka, 1986. - 208 p.]. The rapid release of energy in a small volume leads to an increase in pressure in the channel to several GPa. As a result, the plasma channel of the discharge expands with the formation of a shock wave, which forms elastic and plastic waves propagating through the transfer medium 1 to the material 5 being destroyed. Under the influence of the elastic wave, a stress-strain state 7 is formed in the material 5, varying from tens to hundreds MPa, causing formation, growth of cracks and ultimately destruction of the material 5.

Figure 3 shows the dependence of the energy introduced into the discharge channel on time for different transmission media: 8 - plastic material, 9 - water. The energy introduced into the discharge channel was calculated by integrating instantaneous power:

$$W={\displaystyle \underset{0}{\overset{T_0}{\int }}U(t)\cdot i(t)dt,(2)}$$

where U is the voltage;

i is the current;

W - released energy;

T ₀ - time of energy release;

t is time.

The study of energy release in the discharge channel in water (according to the prototype) and in plastic materials (according to the proposed invention) was carried out on an electric energy storage device with a charging voltage of 10 kV, a capacity of 12 μF, an inductance of 1.067 μH, and an active resistance r _z = 0.0197 Ohm. An exploding copper conductor 2 with a diameter of 0.15 mm and a length of 50 mm was placed along the axis of the cartridge 6, made in the form of a cylinder of plastic material with a diameter of 24 mm. Plasticine (OST 6-15-152525-86) and polyethylene (GOST 16338-85) were used as plastic materials. Figure 3 shows that the power of energy release in the channel of a capillary discharge in a plastic material in the first half wave of current is ~ 15% higher than when discharged in water. This shows the efficiency of using the properties of a capillary discharge to increase the amplitude and steepness of the front of a shock wave propagated through a transmission medium 1 into destructible material 5.

The implementation of the method is presented on the example of a specific implementation. A hole was formed with a depth of 30 cm on the surface of a concrete block measuring 100 × 60 × 60 cm and grade B40, a cartridge 6 was made of plastic material 1 with a 10 cm long blasting conductor 2 placed inside the hole and connected with tires to an electric energy storage device with a capacity of C = 168 uF and charging voltage U = 20 kV. After the operation of the gas discharge switch and the beginning of the discharge of the storage ring, the explosion of conductor 2 and the initiation of the discharge channel occurred. A further discharge of the storage ring with a current of 200 kA occurred on the formed discharge channel filled with metal vapor of the exploded conductor 2. The rapid release of energy in a small volume led to an increase in pressure in the discharge channel. As a result, the plasma channel of the discharge expanded with the formation of a shock wave, which formed elastic and plastic waves propagating into the concrete blocks through plastic material 1. Under the influence of the elastic wave, a stress-strain state was formed in the concrete, which caused the destruction of the block. Plasticine (OST 6-15-152525-86) and polyethylene (GOST 16338-85) were used as a plastic material.

An advantage of the claimed method is to increase the efficiency of rock destruction by increasing the amplitude and reducing the energy loss of the shock wave, which is achieved by using a plastic material with acoustic stiffness close to the acoustic stiffness of the material being destroyed as a transmission medium.

Table Transmission medium Energy of a shock wave transferred to a solid,% concrete granite marble sandstone Water 69.7 32.9 29.1 73.5 Paraffin 64.7 thirty 26.3 68.9 Polyethylene 90.5 46.8 42 89.1 Plasticine 89 46 41.3 87.6

Claims (3)

1. The method of electric-discharge destruction of solid materials, including forming a hole in a solid material, placing a cartridge in it with a substance betraying a shock wave and an exploding conductor, and initiating a discharge with an exploding conductor, characterized in that a plastic material with acoustic material is used as the substance transmitting the shock wave stiffness close to the acoustic stiffness of the material being destroyed. 2. The method according to claim 1, characterized in that the plastic material is polyethylene. 3. The method according to claim 1, characterized in that plasticine is used as a plastic material.

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