RU2791609C1 - Method of conducting blasting operations on extended blocks, taking into account the pre-destruction zone - Google Patents

Abstract

FIELD: rock industry.

SUBSTANCE: explosive destruction of rocks using multi-row short-delayed blasting. The invention can be used in various industries that use blasting in rock masses. The method of conducting blasting operations on extended blocks, taking into account the pre-destruction zone, includes building a model for the development of a mass explosion in time and space for a specific blasting scheme, including cutting and breaking rows. The starting pulse for blasting is simultaneously applied to two cutting rows located in the second row of borehole charges from the edge of the block, to the boreholes from opposite ends from opposite corners of the block towards each other. Cutting rows are placed across an extended block. The number of breaking rows of wells between the cut rows is taken equal to twice the number of wells in the cut row. The deceleration interval along the breaking rows of wells is taken as 200 ms, and in the cutting rows it is twice as high.

EFFECT: increasing the intensity of the weakening of the rock mass in most of the blasted block by changing the location of the cutting rows and the slowdown intervals between the cutting and breaking rows.

1 cl, 11 dwg

Description

The invention relates to the field of explosive destruction of rocks using multi-row short-delayed blasting and can be used in various industries that use blasting in rock masses.

During multi-row short-delayed blasting (MSBB) with the initiation of mass explosions by the LSH + RP system, the blasted blocks were either isometric, when the number of rows of holes and holes in the rows differed slightly or the number of holes in the rows was a multiple of the number of rows of holes, which were located mainly along the ledge. [1, p. 256-263]. The main condition was the presence of at least 6-8 rows of wells to ensure the high-quality operation of the MCW [2]. With the advent of non-electric initiation systems and the transition to ledges 5 m high, the number of rows of wells began, as a rule, to be a multiple of the number of wells in rows. Thus, in [3], a mass explosion of a conventional industrial block with a volume of 129,015 m ³ and a length of more than half a kilometer is considered, on which 940 wells with a diameter of 215 mm and an average depth of 6.1 m (average ledge height of 5.5 m) were blown up perpendicular to the edge of the ledge with the number of holes in a row from 6 to 20 pcs.

By analogy with mine workings, called extended ones with a significant difference in diameter and length [4, p. 116], it is possible to consider exploding blocks as extended if the number of rows of wells exceeds the number of wells in them by 3-5 times.

It is known that the process of the crushing action of an explosion in the environment is an active component of the general destruction of rocks with discontinuity and separation (dispersion) of rocks as a result of the action of various physical factors of the explosion on them. The shock wave from the explosion of the explosive charge turns into a voltage wave in the form of an inelastic perturbation of the medium with a fairly smooth change in parameters and a propagation velocity equal to the speed of sound in the given medium, and the time for removing the substance from the state of rest is always less than the time it takes to return to this state. In the area of propagation of compression waves, covering a volume of 120-150 charge radii (R _c ), the medium behaves inelastically, residual deformations occur in it, leading to a discontinuity in the structure of the medium [1]. Thus, the process of destruction of a rock mass bounded by an open surface does not proceed instantly, but over a certain time, when the system of forces and stresses involved in the destruction changes significantly in space. From a physical point of view, the process of brittle destruction of rocks by an explosion is characterized by one type of destruction - separation under the action of tensile stresses from a stress wave in the rarefaction phase. This leads to the formation of crack systems that separate the rock mass into separate parts.

Qualitative indicators of explosions in open pits of Navoi Mining and Metallurgical Plant using non-electric initiation systems of the ISKRA type are characterized by a compact form of collapse of the exploded rock mass, which helps to reduce losses and impoverishment; a decrease in the output of large-sized fractions of the rock mass; improving the quality of working out the bottom of the ledge and reducing the seismic effect. The improvement of the listed indicators in work [5] is explained by multiple explosive loading of a rock mass when implementing the principle “one deceleration - one borehole charge”, which contributes to the formation of additional outcrop surfaces, and in work [6] the specific deceleration between wells in a row is taken from 29 ms /m, between rows of wells - from 33 ms/m. It is the combination of the "one deceleration - one downhole charge" principle with extended deceleration intervals that makes it possible to improve the quality of rock mass crushing.

The closest in essence to the problem to be solved is the method of conducting blasting operations, taking into account the pre-destruction zone, which includes building a model for the development of a mass explosion in time and space for a specific blasting scheme, applying a starting impulse for blasting simultaneously to two cutting rows located in the second or third row of boreholes. charges from the edge of the block from opposite ends of the cutting rows towards each other. The starting impulse for blasting the starting impulse for blasting is given from opposite ends of the cutting rows towards each other, the deceleration interval in the cutting rows is taken not less than 100 ms, and in the perpendicular direction, along the rows of breaking wells, it is twice as high [7].

EFFECT: invention makes it possible to increase the intensity of weakening of the rock mass in the middle part of the blasted block due to the mutual imposition of pre-destruction zones from two cutting rows along its edges.

The disadvantage of this method, taken as a prototype of the claimed invention, is the increase in the intensity of the weakening of the rock mass due to the mutual imposition of pre-fracture zones from two cutting rows along its edges only in the middle part of the blasted block with a low multiplicity of stress waves passing through the areas of borehole charges at the edges of the block . The scheme is applicable on isometric blocks, with the number of wells in rows of wells close to the number of rows between cuts.

The technical problem to be solved by the proposed invention is to increase the intensity of the weakening of the rock mass in most of the blasted block by changing the location of the cutting rows and the slowdown intervals between the cutting and breaking rows.

The task is achieved by the fact that in the method of conducting blasting operations on extended blocks, taking into account the pre-destruction zone, including the construction of a model for the development of a mass explosion in time and space for a specific scheme of blasting operations, including cutting and breaking rows, the supply of a starting explosive pulse for blasting is carried out simultaneously at two cut rows located in the second row of borehole charges from the edge of the block, from opposite corners of the block towards each other, according to the invention, the cut rows are located across the extended block, the number of fender rows of wells between the cut rows is taken equal to twice the number of wells in the cut row, the deceleration interval 200 ms are taken along the breaking rows of wells, and twice as high in the cutting rows.

We will consider the implementation of the method of blasting operations on extended blocks, taking into account the pre-destruction zone, using the example of block blasting with borehole charges 215 mm in diameter, located on a grid of 5 × 5 m, using a non-electric waveguide initiation system, for example, RIONEL. The radius of the destruction zone can reach a limit value of 30-40 charge radii (R _c ), i.e. 3.2-4.3 m [8], and the radius of the pre-fracture zone - values in (200-250) R _z , i.e. 21.4-27.5 m [9]. For graphical construction of a model of the interaction of explosive stress waves in pre-fracture zones, the size of the destruction zone is assumed to be 8.5 m, and the pre-fracture zones - 55 m. Slowdown between the wells of the surface network can be performed by the RIONEL X-200 device, for cutting rows - by two RIONEL X- devices 200 connected in series, and the initiation of the downhole network - by the RIONEL LP-50 device with a delay of 5000 ms. The choice of such a scheme is explained by the spread of the deceleration intervals allowed by the manufacturer: for the Rionel X-200 it is 188-212 ms, for the Rionel LP-50 it is 4750-5240 ms, therefore, the calculated minimum deceleration between explosions of adjacent deceleration stages is possible 62 ms. The initiation of the surface network of downhole charges of the block is carried out from opposite ends of the cutting rows towards each other. When constructing a graphical model for analyzing the passage of stress waves through the areas where borehole charges are located, the following conditions are accepted [2]:

- the zone of destruction of each previous downhole charge, exploded with an actual delay of more than 75 ms, is a shielding medium that reflects from its surface about a third of the energy of stress waves back into the explosive volume with the absorption of the rest of the energy. Therefore, the pre-destruction zone in the region of previously exploded borehole charges is closed by rays emerging from the center of the explosive charge in relation to the nearest neighboring destruction zones [10];

- when applying pre-fracture zones formed by simultaneously explosive charges of each deceleration stage to the location area of any borehole charge, it is subject to the action of all incoming stress waves (in this case, up to five, taking into account the multiplicity of the size of the pre-fracture zone in the grid of wells), regardless of the direction of arrival waves - this causes the alternation and multidirectional influences.

Consider the features of the development of a mass explosion according to the proposed invention.

In FIG. 1 shows the first block blasting scheme with 15 wells in a row; in fig. 2 - graphical model of the development of a mass explosion at the deceleration stage of 3600 ms, when the first superposition of stress waves from both cut rows occurred; in fig. 3 - graphical model of the development of a mass explosion at the deceleration stage of 4600 ms, when the block was completely covered by stress waves from both cutting rows; in fig. 4 - the total number of stress waves that passed through the areas of the location of the borehole charges of the block before they were blasted (the areas of borehole charges with the passage of 30 or more voltage waves are filled with color); in fig. 5 - the final number of stress waves that passed through the areas of location of borehole charges of the block before they were blasted for the second block blasting scheme with 10 wells in the cut row; in fig. 6 - the final number of stress waves that passed through the areas of location of the borehole charges of the block before they were blasted according to the third blasting scheme of the block with 8 wells in a row; in fig. 7 - a graphical model of the development of a mass explosion according to the third scheme of block blasting at the deceleration stage of 2400 ms, when the block was completely covered by stress waves from both cutting rows; in fig. 8 - comparison of the percentage distribution of the dynamics of the coverage of the block by stress waves for different blasting schemes.

On graphical models, the destruction zones are filled with gray, the pre-destruction zones formed by explosions of specific downhole charges are limited by rays emerging from their centers regarding the destruction zone of the previously exploded charge until they intersect with a circle with a radius of 250R.3. The number of stress waves that have passed through the areas of location of specific borehole charges at a certain stage are indicated by a number inside the geometric figure, and the multiplicity of the impact of stress waves on the area of specific borehole charges of a given deceleration stage is reflected by the shape of the geometric figure (placed under the graph in Fig. 2, 3 and 7) .

When using two cutting rows, all charges of the block are exploded by sets of holes - from 2 in the starting set to 30 at the deceleration stage of 5400 ms according to the first blasting scheme. But always between the wells of the set there are zones of destruction of previously triggered charges, excluding the direct interaction of neighboring charges of the set - each borehole charge explodes separately. However, stress waves in the pre-fracture zones of most of the closely spaced charges of the set interact with superposition. Multiple passage of stress waves in the compression-tension stage through the vicinity of borehole charges in the pre-fracture zone has a cumulative effect of increasing the fracturing of the rock mass [11], which significantly contributes to its division into smaller fractions.

Stress waves are absorbed in the fracture zone, producing additional rock crushing in it, which must be taken into account when constructing pre-fracture zones - they look like sectors of various configurations. The rock mass in the areas of borehole charges, falling on the overlap of the sectors of the pre-fracture zones, is repeatedly exposed to stress waves. At the deceleration interval of 3600 ms, the counter superposition of stress waves from both cut rows begins, covering the areas where 16 downhole charges are located. In this case, such an overlay covers the region of location of 2 downhole charges three times, four times - 5 charges and five times - 9 charges (Fig. 2).

The peculiarity of crack growth under the action of stress waves should be emphasized. In [12], it is proposed to take into account that under the action of a cyclic alternating load, an energy flow to the crack tip occurs. At the same time, tensile and compressive stresses that are identical in absolute value create equal energy flows, but their effect on crack growth is directly opposite: the energy of compressive stresses has a strengthening effect, and that of tensile stresses is aimed at breaking bonds at the crack tip. Crack growth cannot occur at the stage of compressive loading, despite the influx of energy into the crack tip. This feature corresponds to the physical nature of the bond breaking mechanism only under the action of tensile or shear stresses, and not all the energy of tensile stresses is spent on crack growth, but only its excess over the energy of medium deformations.

As examples of the implementation of the method, three schemes for the arrangement of downhole charges in rows are considered: 15 in the first example, 10 (one third less) in the second and 8 (twice less) in the third example.

In the first example, at the 4600 ms deceleration stage, the pre-fracture zones from the explosion of charges of well 361 from the side of the upper cut row and well 120 from the side of the lower cut row reached opposite cut rows, i.e. covered almost the entire block. The maximum number of stress waves simultaneously affecting the areas of wells 161 and 320 has reached 10, and the total number of stress waves that have passed through the area where these charges are located by this moment has reached 40.

In the third example of blasting, with 8 wells in a row, at the deceleration stage of 2400 ms, the pre-fracture zones from the explosion of the charges of well 105 from the side of the upper cut row and well 47 from the side of the lower cut row also reached opposite cut rows, i.e. covered almost the entire block. The maximum number of stress waves simultaneously affecting the areas of wells 54, 69, 84, and 99 reached 8, and the total number of stress waves that affected the area of these charges by this moment reached 49, 53, 32, and 49, respectively (see Fig. 8).

The largest number of stress waves that passed through the areas of location of borehole charges in the pre-fracture zones, in the first example with the number of holes in the cut 15 (the length of the row is three times the size of the pre-fracture zone) reached 71; in the second example with the number of wells in the cut 10 (with a twofold excess of the row length over the pre-fracture zone) - 67, and with 8 wells in a row (the row length is 1.5 times higher than the pre-fracture zone) - 59.

Therefore, there is a regular decrease in the ratio of the passage of stress waves through the areas where the charges of the block are located as the multiplicity of coverage of rows of wells by the pre-fracture zone decreases. But in all well layouts in a row, there is an increase in the number of stress waves of more than 30 already from the second row after the cut. This indicates the presence of a direct relationship between the maximum number of stress waves that have passed through the areas of charges on the block and the multiplicity of overlapping of the pre-fracture zone by the length of a row of wells, and the degree of coverage of the block by increased effects of stress waves remains the same - already from the second row from the cut from both corners of the block .

In the embodiments of the claimed invention, the dynamics of the passage of voltage waves differs by 10-20% up to 15 passages of voltage waves, after 20 passages the curves of the 2nd and 3rd examples merge, and after 35 exposures and with the first example, the difference decreases to 5-7%.

Thus, the inventive method of conducting blasting operations on extended blocks, taking into account the pre-destruction zone, makes it possible to stably cover a significant part of the area of the block between the cut rows by the oncoming superposition of stress waves that have passed through the area of the borehole charges, increasing the weakening of rocks in the area of the blasted borehole charges, can be applied on blocks of various lengths with a different number of wells in a row and, thereby, solve the set technical problem.

Information sources

1. Handbook of explosives / B.N. Kutuzov [i dr.]. Under the general editorship of B.N. Kutuzova - M: Nedra, 1988. - 511 p.

2. Mosinets V.N. Crushing and seismic action of an explosion in rocks. - M., Nedra. - 1976. - 271 p.

3. Influence of blasting schemes on processes in the zone of preliminary destruction / E. B. Shevkun, A. Yu. Plotnikov // Mine surveying and subsoil use. - 2021. - №4. - S. 23-34.

4. Mining: Terminological dictionary /Under the scientific editorship of acad. RAS K.N. Trubetskoy, corresponding member. RAS D.R. Kaplunov. - 5th ed., Re-work. and additional - M.: Publishing house "Gornaya kniga", 2016. - 635 p.

5. Rubtsov S.K., Ershov V.P. The use of non-electric initiation systems in the open pits of the Navoi Mining and Metallurgical Plant // Physical problems of rock destruction: Sat. tr. Fourth International Scientific Conference, October 18-22, 2004. M. 2005. S. 387-391.

6. Patent of the Russian Federation No. 2593285, IPC E21C 41/26.

7. Patent of the Russian Federation No. 2744534, IPC F42D 1/08, F42D 3/04, E21C 41/26 (prototype).

8. Yurovskikh A.V. Development of a rock destruction model at the quasi-static stage of the explosion: Dis. … cand. tech. Sciences: 25.00.20: St. Petersburg, 2003. - 119 p.

9. Alexandrov B.E., Kochanov A.N., Levin B.V. On the relationship of strength and acoustic properties of rocks in the zone of pre-destructive action of an explosion // Physico-technical problems of mineral development. - 1987. - No. 4. - S. 24-32.

10. Shevkun E.B., Leshchinsky A.V., Shishkin E.A., Lysak Yu.A. Graphic-analytical method for determining the intensity of preliminary destruction of the vicinity of blast holes. // Explosive case. - 2018. - No. 121/78. - S. 33-47.

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12. Karkashadze G.G., Larionov P.V., Mishin P.N. Modeling of crack growth under the action of cyclic loading // Mining Information and Analytical Bulletin. 2011. №3. pp. 258-262.

Claims (1)

A method for conducting blasting operations on extended blocks, taking into account the pre-destruction zone, including building a model for the development of a mass explosion in time and space for a specific blasting scheme, including cutting and breaking rows, the starting impulse for blasting is carried out simultaneously on two cutting rows located in the second row borehole charges from the edge of the block, to wells from opposite ends from opposite corners of the block towards each other, characterized in that the cut rows are located across the extended block, the number of fender rows of wells between the cut rows is taken equal to twice the number of wells in the cut row, the deceleration interval along the fender rows rows of wells take 200 ms, and in cut rows - twice as high.

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