RU2442957C2 - Method for obtaining a preset crushing ratio of fissured mountain mass and the required coefficient of heading advance per round to shot holes length ratio - Google Patents

Abstract

FIELD: mining

SUBSTANCE: method comprises shot hole or bore-hole drilling, loading them with explosive material so that the bottom part of the shot hole the explosive material density or energy concentration would exceed the one in the wellhead of the shot hole. The mass of explosive material charge in the bottom part of the shot hole is calculated mathematically, depending on the line of least resistance value, the diameter of explosive material charge, fissure parameters and physical and technical mountain mass parameters, the rock pressure and detonation velocity of the explosive material.

EFFECT: enhanced efficiency and safety of drilling and blasting operations alongside with ore beneficiation efficiency.

1 dwg, 1 dwg

Description

The invention relates to the mining industry, in particular to a layered system for the development of mineral deposits using drilling and blasting operations.

There is a method of improving the quality of crushing of a rock mass by blasting in quarries, according to which explosives with the lowest specific energy are located at the wellhead, and explosives with high specific energy are used in the lower part of the well or by drilling boiler extensions in the lower part of the well [1].

However, the author does not indicate what is the diameter of the boiler in the expansion zone or what is the mass of explosives (explosive charge length) with high energy, which must be selected depending on the physical and technical properties of the rock mass, detonation and geometric parameters of the explosive.

The closest technical solution is the method of charging holes with a different concentration of explosion energy in the bottom and core parts of the hole [2]. Moreover, the length of the bottom of the borehole is 1/3 of the depth of the borehole, and the loading density is 0.85 g / cm ³ for ammonites, which is created by compaction of the explosives with the help of the bottomhole. The concentration of explosives in the core part is 0.5 kg / m, which is achieved by leaving the air gap and part of the hole for jamming.

However, the bore hole explosive charges used in underground ore mining, as a rule, charge 2/3 of the length of the hole. That is, half of the explosive charge will have a density of 0.85 g / cm ³ (high energy concentration), and the other half of 0.45-0.55 g / cm ³ (low energy concentration) due to the presence of an air gap.

In addition, when calculating the mass of the charge in the bottom, the line of least resistance (LNS), explosive charge diameter, fracture parameters and physicotechnical properties of the rock mass, detonation characteristics of explosives and rock pressure are not taken into account.

A method is proposed for obtaining a given degree of crushing of a fractured rock mass and the required coefficient of hole utilization (KIS) by blasting, including drilling holes or bore holes, loading the explosives so that the explosive density or energy concentration in the bottom of the hole is greater than in the wellhead , characterized in that the mass of the charge of the compacted or high-explosive explosive in the bottom of the hole is determined taking into account the magnitude of the LNS, the diameter of the charge, the parameters of fracturing and the physical and technical properties of the massif of the furnace rocks, rock pressure value and the velocity of detonation of expression

where π = 3.14,

W is the line of least resistance or the distance from the hole to the contour of the cutting cavity, m;

d _e is the average size of the array, m;

F - an indicator of fracturing of the array;

d ₃ - diameter of explosive charge, m;

µ is the coefficient of friction between the elements of the array;

P is the magnitude of the rock pressure between the bore holes and the logging cavity, Pa;

D — detonation velocity of explosives, m / s;

ν is the Poisson's ratio of the rock.

The proposed method allows to provide a high KISH due to compaction of explosives and determining the mass of the bottom of the explosive charge necessary to overcome the LNS. In addition, the non-compaction of explosives in the estuarine part allows to reduce the yield of fine fractions in the blasted rock mass, which leads to an increase in the concentration efficiency of, for example, uranium ores. The mass of explosives with a high concentration of energy (due to compaction or the use of a more powerful explosive) in the bottom is determined taking into account the magnitude of the LNS, the diameter of the charge, the fracturing parameters and the physical and technical properties of the rock mass, the rock pressure and the detonation velocity of the explosive. This allows you to increase the level of safety, the efficiency of drilling and blasting and ore dressing.

The essence of the method is as follows. The underestimated mass of the explosive charge in the bottom is not enough to break the rock mass away from the massif during layer excavation of ores. Therefore, “glasses” appear in the newly formed face, which reduces the efficiency of blasting. The overestimated mass of the explosive charge in the bottom part leads to overgrowing of the ore mass and a decrease in the efficiency of X-ray radiometric concentration, for example, of uranium ores.

The mass of the explosive charge in the bottom, necessary for breaking the array with the maximum KISH, can be determined based on their first Newton's law in voltage. The compressive stress arising in the rock mass at the time of the explosive charge explosion at a distance from the charge equal to the LPS should be equal to the sum of the friction forces created by the rock pressure and the lateral spread of the rock. The mathematical conclusion is given in Appendix 1.

и D².The yield of over-crushed fractions in the mouth part of the borehole with a size of less than 40 mm (V _M ) substantially depends on the loading density (ρ _in ) and the detonation velocity of the explosive D. That is, V _{M is} directly proportional

and D ² .

An increase in the loading density of explosives from 600 to 850 kg / m ³ will lead to a 2-fold increase in the yield of fine fractions in the wellhead. The use of instead of ammonite 6GW with a value of D = 4.2 · 10 ³ m / s, detonite with D = 5.1 · 10 ³ m / s will lead to an increase in the yield of fine fractions by 1.47 times in the estuary part of the hole. The mathematical conclusion V _{M is} given in Appendix 2.

The proposed method is as follows. The Poisson's ratio of rocks is determined at the stage of exploration by known methods. The detonation velocity D and the explosive charge diameter d _{3 are} determined using reference books. The rock pressure in the area of the layered entry is determined either by geophysical methods, or by the well-known formula P = ρgH, where ρ is the bulk mass of the rock mass, kg / m ³ , g is the acceleration of gravity, m / s ² , N is the depth from the surface of the earth, m, K value is the concentration coefficient of rock pressure in the region of the blast hole being blasted, usually it is K = 2-3. The value of the values of f, µ is determined depending on d _e according to the table

d _e , m <0.05 0.05-0.15 0.15-0.40 0.40-1.0 > 1.0 F > 12 12-10 10-8 8-6 <6 µ <0.2 0.2-0.3 0.3-0.45 0.45-0.6 ≥0.6

The magnitude of the LNS W is determined by the passport BVR. For the cut hole, W is equal to the distance between them, for the drill hole, to the minimum distance from the hole to the surface of the cut hole. For contouring - the minimum distance from the hole to the exposed surface of the formed cavity.

The value of d _e is determined directly by the bottom of the mine. Substituting

the numerical values of the parameters in the formula (1), we obtain the value of Q. Next, in the lay-in drill, cut, bump and contouring holes are drilled. All bore holes charge. When using the same type of explosive, the cartridges in the bottom are sealed as much as possible with a downhole. Explosive cartridges in the mouth part are introduced into the holes without compaction. When using a different type of explosive, a more workable explosive is introduced into the bottom part (for example, detonite M, ammonal 200), and in the near mouth, a less workable explosive is ammonite 6ZHV.

Next, the network is installed and blown up in accordance with the BVR passport.

Example. At the Gluboky mine of JSC PIMCU, in an array of hard-to-explode granites with a size of 0.3-0.5 m, ore is mined using a top-down dredging system with a hardening tab. Drill bore holes and explode according to conventional technology, loading bore holes with 6ZHV ammonite and prepressing all cartridges. Measurements of the results were carried out by determining the KISH (along the length of the "glasses") and the yield of small fractions (-40 mm) by the photoplanimetric method. Results after five cycles of blasting: KISH amounted to 0.7-0.85, the yield of the fraction - 40 mm was 37-45%.

Next, it was decided to use the new method. The numerical values of the parameters in the formula (1): W = 0.7 m; d _e = 0.4 m; F = 8 (see table); d ₃ = 0.04 m; rock pressure at H = 500 m, ρ = 2.5 · 10 ³ kg / m ³ , g = 9.8 m / s ² , K = 2 is equal to P = 2.46 · 10 ⁷ Pa; D = 4.2 · 10 ³ m / s; ν = 0.25. Substituting the numerical values in the formula (1), we obtain Q = 0.24 kg.

Calculations by the formula (1) showed that the mass of the bottom sealed portion of the explosive charge should be equal to 0.24 kg - this is approximately one cartridge of 6GV ammonite. Subsequent experimental work in hard-to-explode granites with a mass of the bottom of the charge equal to 0.2-0.25 kg (1 cartridge), and the loading density of the mouth part of the charge (3-4 cartridges weighing 0.6-1.0 kg, diameter 32 mm ), equal to 0.64 · 10 ³ kg / m ³ , showed: KISh was 0.8-0.9, the fraction yield was 40 mm 28-35%.

Thus, the application of the new method allowed to increase the NIR and reduce the yield of fine fractions, which provided an increase in the efficiency and safety of drilling and blasting operations, as well as the effectiveness of X-ray radiometric enrichment.

Information sources

1. Efremov E.M. Preparation of rock mass in quarries. - M .: Subsoil. - 1980. - S.203 (Fig. 60e, m), p.206.

2. Technique and technology of blasting in mines // Avt. G.P. Demidyuk, L.V. Dubnov, V.V. Stoyanov, etc. - M .: Nedra. - 1978. - S.186-187.

Appendix 1. Theoretical calculation of the mass of the explosive charge in the bottom of the hole to increase the NIR

The increase in the utilization rate of the borehole in a downward layer excavation of ores increases the efficiency of mining and the level of safety. To increase the NIR, it is recommended to compact explosives in the bottom of the borehole or use a more efficient explosive there. However, it is necessary to determine the mass of explosives sufficient for reliable breaking of the massif into the logging cavity. Underestimating the mass of explosives will not lead to a given KISh; overestimating it will not result in overmilling of the ore mass, which negatively affects the enrichment of, for example, uranium ores.

The explosive charge mass in the bottom part, sufficient for reliable breaking of the rock mass, can be determined on the basis of Newton's first law in stresses. The compressive stress σ _in (r) arising in the rock mass at a distance r (r = W, where W is the LNS) must be equal to or greater than the sum of the friction forces created by the rock pressure (σ _g ) and the lateral spread of the rock (σ _br ) on the contour of the cutting cavity

According to [1] for a spherical explosive charge

where ρ _in , D, d ₃ - respectively, the loading density, detonation velocity of the explosive, the diameter of the explosive charge; W - LNS; d _e , Ф - respectively, the average size of a piece of individuality in a mountain massif, the deformability index of a fractured mountain massif, π = 3.14.

According to [2]

where μ, ν are, respectively, the coefficient of friction between pieces of rock mass in the cut, the Poisson's ratio of the rock, and P is the rock pressure between the bore holes and the cutting cavity.

Substituting (2) and (3) in (1), we obtain

, получим формулу для определения массы заряда ВВ, необходимой для выброса горной массы из врубовой полостиMultiplying the right and left side of (4) by

, we obtain the formula for determining the mass of the explosive charge necessary to eject the rock mass from the logging cavity

The energy of a cylindrical explosive charge from the bottom part propagates as spherical when considering processes at large distances (15-30 diameters of the explosive charge) [1]. In this case, l ₃ = 4d ₃ [3]. Then (5) can be rewritten in

form

Appendix 2. Calculation of the yield of over-crushed fractions (-40 mm) when changing the detonation characteristics of explosives.

The yield of over-crushed fractions with a size of less than 40 mm can be determined from geometric considerations by the formula

Where

R _M is the radius of the zone of overgrown fractions near the explosive charge, defined in [2], m;

N is the number of holes in the face of a layover;

S is the cross-sectional area of the lay-in, m ² ;

ρ _in - loading density, kg / m ³ ;

s is the longitudinal wave velocity in the rock sample, m / s;

d _M - the maximum size of a piece in overgrown rock mass, d _M = 0.04 m;

σ _p is the tensile strength of the rock sample, Pa.

An analysis of formula (7) after substituting into it (8) shows that the yield of small fractions V _{M is} directly proportional to D ² and ρ ² .

Bibliographic list

1. Tyupin V.N. Geometrization of the crushing zone of a fractured massif parallel to the axis of the explosive charge. // Proceedings of universities. Mountain Journal. - 1985, No. 1, - P. 41-45.

2. Tyupin V.N. Improving the efficiency of geotechnology using the energy of the explosion during the deformation of fractured stressed massifs of rocks. // Thesis for the degree of Doctor of Technical Sciences - Moscow: VNIPI industrial technology. - 2002. - P.102, 104.

3. Pokrovsky G.I. Dependence of the shape of the explosion zone on the shape and location of charges. - In the book. Blasting business. - M .: Subsoil. - 1964. - No. 54/11. - S. 237.

Claims (1)

A method of obtaining a predetermined crushing degree of a fractured rock mass and the required hole utilization coefficient (KIS) by blasting, including drilling holes or bore holes to load explosives so that the explosive density or energy concentration in the bottom of the hole is greater than in the wellhead part, different the fact that the mass of the charge of a compacted or high-explosive explosive in the bottom of the hole is determined taking into account the magnitude of the LNS, the diameter of the charge, the parameters of fracturing and the physicotechnical properties of the rock mass, led causes of rock pressure and detonation velocity of explosives from the expression

,
where π = 3.14;
W is the line of least resistance or the distance from the hole to the contour of the cutting cavity, m;
d _e is the average size of the array, m;
F - an indicator of fracturing of the array;
d ₃ - diameter of explosive charge, m;
µ is the coefficient of friction between the elements of the array;
P is the magnitude of the rock pressure between the bore holes and the logging cavity, Pa;
D — detonation velocity of explosives, m / s;
ν - Poisson's ratio of rocks.