# Method for seam damage of cracked rocks

FIELD: mining.

SUBSTANCE: method includes drilling of keyholes, popholes and cropper holes, placement of charges in them and blasting. The distance between cropper holes is defined mathematically depending on parameters of rock massif cracking, effect of friction between separate parts of the massif, rock pressure, physical and mechanical properties of rock massif, speed of detonation and density of explosive charging.

EFFECT: higher efficiency and level of rock safety.

The invention relates to the mining industry and railway construction, in particular when drilling and blasting drilling mining and railway tunnels.

The known method the contour of rock fracture and subsequent delineation of a rock during the sinking of the workings involving the sequential blasting electric, pneumatic, and then contouring blast hole explosive charge.

The distance between the contour of the bore-holes andtochoose

depending on the line of least resistance (LNS) charges in counting the holes [1] by the formula

where W is LNS, m

This LENS depends on the solidity of rocks and equal to W=0.5-0.6 m for monolithic rocks and W=0,7-0,8 m for silentresident rocks.

However, the formula is not considered rock pressure and the effect of friction, which reduces the radius of the zone of fracturing. Besides not considered basic physico-mechanical parameters of the rock mass and detonation characteristics of CENTURIES.

The closest technical solution is the way the contour of rock fracture and subsequent delineation (see [2], formula 198-199), in which the distance between the contour of the holes depends on the detonation characteristics of CENTURIES, the geometric parameters of the charge and of the hole, physico-mechanical SV is ist rocks, LNS overcontouring of the explosive charge.

However, the formulas are not taken into account the parameters of the fracturing of the rock mass, significantly affecting the radius of the radial crack formation, and hence on the optimal distance between the contour of the bore-holes. Also, do not take into account the effect of friction between the separateness of the array, and rock pressure is taken into account implicitly in the form factor (see [2], str)whose numerical value is not given.

In addition, in the formula (see [2], formula 198-199) ρBBdesignated as the density of CC (see p.35), but the deciding factor in the nature and parameters of the destruction of the array is the density of loading, which, depending on the location and degree of compaction of EXPLOSIVES in a drill hole may be 1.2 to 2 times less than the density of CENTURIES.

The method of contour destruction of fractured rocks with further delineation, including the drilling of electric, pneumatic, and then counting holes at a distance from each other, depending on the detonation characteristics of CENTURIES, the geometric parameters of the charge and of the hole, physico-mechanical properties of rocks, placement of the explosive charge with fighters and blasting electric, pneumatic and counting holes, characterized in that the parameters of the fracturing of the rock mass, effect of friction, rock pressure and density dawn the project for the distance between the contour of the bore-holes is determined from the expression

where

π=3,14

D - speed detonation of EXPLOSIVES, m/s;

d3- the diameter of the explosive charge, m;

l3- the total length of the charge in the borehole, m;

ρCC- density EXPLOSIVES in cartridge, kg/m3;

dWthe diameter of the hole, m;

lW- the length of the borehole, m;

C is the speed of longitudinal waves in the rock, m/s;

ν is the Poisson's ratio of rock;

µ - coefficient of friction between the separateness of the array;

σp- the tensile strength of rock, PA;

The p - value of rock pressure in the area of the contour of the bore-holes, PA;

F is the indicator of fracturing;

h is the effective width of the emission zone of the massif, depending on the number of interacting explosive charge, h=2W, m;

W - LNS charges counting holes, m

The proposed method will provide a delineation of production due to determine the optimal distance between the contour of the bore-holes taking into account the whole complex of factors: parameters of fracturing, the physical properties of the rock mass, detonation characteristics CENTURIES, the ground pressure, and taking into account the effect of friction.

The method consists in the following. It is known that the destruction of fractured rock then the d (especially for contour blasting) is caused by the operating of stress waves, so, basically, under the action of quasi-static pressure of detonation products. That is, for a time equal to the microsecond, 1 kg CENTURIES allocates about 1 m3gases. This is accompanied by the appearance in the rock mass compressive (radial) and tensile (tangential) stresses. Tensile stresses are creating around the charge of radial cracks.

While blasting two or more of the explosive charge by a distance sufficient for germination between adjacent charges 2 counter cracks, will be a distance equal to twice the radius of the radial cracks, multiplied by a factor that takes into account the interaction between adjacent explosive charge. Theoretical calculation to determine the distance between two contour of the holes in the Appendix.

The proposed method is as follows. Physico-mechanical properties of the array σp, c, ν, ρ determined at the stage of exploration by known methods. Speed of detonation of EXPLOSIVES (D) and the diameter of the explosive charge in the electric hole (d3) is determined using the reference literature. The density of loading of EXPLOSIVES in counting the holes is determined from the expression (calculation see Annex)

dWthe diameter of the hole, l3- the total length of the charge in the hole, lW- the length of the hole is determined in accordance with the passport is m blasting. ρCC- density EXPLOSIVES in cartridge determined using reference books.

Rock pressure at the place of production determine or geophysical methods, or by the well-known formula P=ρgHK (where ρ is the bulk density of the rock mass, kg/m3; g - gravitational acceleration, m/s2; H is the depth from the ground surface, m; K is the coefficient of concentration of rock pressure in the area of the blow holes).

The values of f and µ are determined depending on the size of the individual dein the array on the table

 dem <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 of 0.2-0.3 0,3-0,45 0,45-0,6 ≥0,6

Next Buryats electric, pneumatic and counting the holes, the holes are charged and produce blasting.

Example. The sinking of capital mining excavations at 7 horizon mine "Central" OA is PIMCU arrays of trachydacite led to the rock excess due to intensive disturbance array explosion, basically counting holes. The distance between them was 0.65-0.75 m, while the length of the explosive charge equal to 2/3 of the length of the borehole and the explosive charge density of 0.8-0.9 g/cm3(ammo compacted by power). After blasting and measurements established that excess breeds range from 0.24 to 0.32 m on the sides and the roof framing, the number of stabbing 3-5 1 m excavation. This reduces the level of safety of mining operations due to the formation of stabbing. In addition, additional transportation of waste rock (section production increases by 25%on average) reduces the economic performance of the mine.

To reduce transportation costs of the breed and improve the safety of mining operations was determined to be a rational distance between the holes. The array presents trachydacite with de=0.15 to 0.65 m (0.4 m in average). Physico-mechanical properties of trachydacite: c=4,35·103m/s, ν=0,29, σp=1,39·107PA, ρ=2,5·103kg/m3. The loading produced by ammonal - 200 in boreholes with a diameter of dW=0.04 m without seal cartridges. Diameter of the cartridge d3=0,032 m, D=4,4·103m/s, ρCC=103kg/m3, lW=1.8 m, l3=1.2 m, ρIn=0,42·103kg/m3(defined by (2)). The value of rock pressure at a depth H=400 m, with g=9.8 m/s2, K=2, is equal to P=1,96·107PA. Numerical values of µ=0.45 and f=8 defined by t the blitz, the value of h≈2W. Substituting the numerical values of the parameters in the formulas (2) and (1), we obtain ato=0,53 m

Explosive blasting array with the calculated distance between the contour holes (only took 7 cycles blasting) showed that the sticking of species decreased to 0.12-0.15 m, the number of stabbing fell to 2-3 on 1 m excavation. That is, the proposed method can improve the efficiency and level of safety in the mine working.

Sources of information

1. Moines V.N., Pashkov A.D., Latyshev, VA the Destruction of rocks. - M.: Nedra. - 1975. - S.

2. Baron LI, I. Turchaninov, Klyuchnikov AV violation of the rocks in the contour blasting. - Leningrad: Izd. "Science". - 1975. - S-191.

The way the contour of the destruction of fractured rocks with further delineation, including the drilling of electric, pneumatic and counting holes at a distance from each other depending on the detonation characteristics of CENTURIES, the geometric parameters of the charge and of the hole, physico-mechanical properties of rocks, placement of the explosive charge with fighters and blasting electric, pneumatic and counting holes, characterized in that the parameters of the fracturing of the rock mass, effect of friction, rock pressure and density of loading, the distance between the contour of the bore-holes is determined from the expression

where π=3,14;
D - speed detonation of EXPLOSIVES, m/s;

d3- the diameter of the explosive charge, m;
l3- the total length of the charge in the borehole, m;
ρBB- density EXPLOSIVES in cartridge, kg/m3;
dWthe diameter of the hole, m;
lW- the length of the borehole, m;
C is the speed of longitudinal waves in the rock, m/s;
ν is the Poisson's ratio of rock;
µ - coefficient of friction between the separateness of the array;
σp- the tensile strength of rock, PA;
The p - value of rock pressure in the area of the contour of the bore-holes, PA;
F is the indicator of fracturing;
h is the effective width of the emission zone of the massif, depending on the number of interacting explosive charge, h=2W, m;
W - LNS charges counting holes, m

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