RU2052104C1 - Process of rock breaking - Google Patents

Abstract

FIELD: mining industry. SUBSTANCE: process of rock breaking includes drilling of key vertical holes in block, their charging with explosive and row-by-row short-delay blasting. Then block is mapped by drilling of additional vertical and horizontal holes to form screening slits in block. After this simultaneous blasting of additional holes is conducted and rows of key vertical holes are blast in turn starting from row last from free surface of face of shoulder with calculated duration of compression phase of blast pulse. In this case forced vibrations in block coincide with its inherent oscillation frequency creating effect of resonance. EFFECT: increased efficiency of rock breaking thanks to use of energy saturation of block by effect of resonance. 2 cl, 2 dwg

Description

 The invention relates to mining and can be used for borehole rock breaking in open and underground mining of mineral deposits, mainly in monolithic rocks.

 There is a method of breaking rocks by explosion, in which vertical blocks of wells are drilled in a block, the latter is charged with explosive (BB) and sequential short-blast blasting is performed in wells [1] The disadvantage of this method is the insufficient efficiency of rock breaking due to the rigid connection of the block with the array rocks.

 There is also known a method of rock breaking, in which vertical rows of wells are drilled in a block, explosives are charged and followed by short-blasting [2] The disadvantage of this method of rock breaking is inefficient rock breaking, which is caused by increased explosive consumption on the one hand, and on the other incomplete use of the energy of the explosion of borehole charges. Since the block is rigidly connected with the rock mass, the explosion energy of each borehole charge is spent not only on crushing the block, but also on its separation from the mass. The distribution of the energy of the explosion for crushing the rock in the block and its separation from the massif is uncontrollable, therefore, there is an uneven crushing of the rock mass, leading to the formation of oversize.

 The rigid connection of the block with the rock mass also leads to the fact that the stress waves generated to the block during the explosion of borehole charges propagate deep into the mass, losing part of its energy to saturate the rock mass lying outside the block.

 The purpose of the invention is to increase the efficiency of crushing due to the energy saturation of the block by using the resonant effect while saving explosives.

 This is achieved by the fact that in the method of breaking rocks, including drilling in a block placed in rows parallel to the edge of the ledge of the main wells, loading them with explosives and orderly short-blasting, outline the block by drilling vertical and horizontal additional wells to create shielding slots in the block, and then simultaneous blasting of additional wells, and the rows of the main wells explode in turn, starting from the last row from the free surface of the escarpment of the ledge, with a certain length nostyu compression phase of the explosive pulse, the forced oscillations excited in block firings, the same as its natural frequency by creating a resonance effect.

 In addition, the rows of the main wells begin to explode with a retardation interval determined by the propagation time of the blast wave from the last n row to the free surface of the escarpment of the ledge, reflected from it and at the moment the reflected wave arrives at the penultimate (n-1) th row, it blows up, and subsequent rows explode similarly.

 In FIG. 1 shows a plan of a ledge with a layout of wells; in Fig.2 a section along aa in Fig.1 (arrows indicate the direction of motion of the longitudinal wave P).

 The method of breaking rocks is as follows.

 On the contour of the block to be blasted (Fig. 1), vertical 1 and horizontal 2 additional wells are drilled in four planes necessary for the formation of shielding slots, after which rows of the main vertical 3 wells parallel to the edge are drilled in the block (Fig. 2, nn-6) ledge. The depth of vertical 1.3 wells does not exceed the height of the ledge (figure 2).

, мс где f_o собственная частота колебания блока;
К средняя жесткость горной массы (порода или руда) блока;
М масса блока.First, explosive auxiliary charges are blasted in the contouring block of vertical and horizontal wells, and a destroyed and fragmented rock mass is formed, which separates the block from the rock mass from four sides and acts as shielding slots. The mass of explosive charge in contouring wells is calculated as for charges in contour blasting. Then, in the cut-off block, explosive charges are blown in the rows of the main wells with a duration of the compression phase t _{cj of the} explosive pulse, which ensures the efficiency of breaking and the corresponding dependence
t _cr =

, ms where f _{o is the} natural frequency of oscillation of the block;
K the average hardness of the rock mass (rock or ore) of the block;
M is the mass of the block.

где t_сж длительность фазы сжатия взрывного импульса, мс;
10 переводной коэффициент;
g ускорение силы тяжести, м/с²;
Е модуль Юнга, Па;
S площадь поперечного сечения блока, м²;
ρ плотность горной массы, кг/м³;
V объем блока, м³;
L длина блока, м.This dependence can be represented as:
t _cr =

where t _{cz the} duration of the compression phase of the explosive pulse, ms;
10 conversion factor;
g acceleration of gravity, m / s ² ;
E Young's modulus, Pa;
S cross-sectional area of the block, m ² ;
ρ density of the rock mass, kg / m ³ ;
V block volume, m ³ ;
L block length, m.

мс (2) где t_з время замедления, мс;
В_i расстояние от n ряда до свободной поверхности уступа забоя и обратно до (n-1) ряда, м;
V_ср средняя скорость распространения упругих волн в горном массиве, м/с.When charges are blown up in rows with the pulse duration indicated above, a dynamic periodic effect on the block cut off by shielding slots from the massif is ensured. After a short-blown explosion of the main borehole explosive charges in the last row (n) of the ledge, the stress wave reaches the free face of the ledge of the ledge, is reflected from it and reaches the well charges in the penultimate (n-1) row after a time interval determined from the expression
t ₃ =

ms (2) where t _is the deceleration time, ms;
In _{i, the} distance from the n row to the free surface of the ledge of the face and back to the (n-1) row, m;
V _{cf the} average speed of propagation of elastic waves in the rock mass, m / s.

At this moment, the blast hole charges of the explosive (n-1) series are blown with the duration of the blast pulse determined by formula (1), while the blast wave of stress reaches the free slope of the ledge and, reflected from it, reaches the borehole charges (n-2) of the series through the time interval t ₃ determined by the formula (2). The order of blasting the following rows is repeated in the same way.

 Thus, the block is affected by periodic impulse loads, which create the effect of rocking the block due to blasting of rows of wells with the estimated duration of the blast pulse and in a certain sequence. In the proposed method of rock breaking, a resonant effect is realized in which the natural vibrations of the block separated from the rock mass by shielding slots coincide with the forced vibrations generated during the explosion of explosive charges by selecting the duration of the explosive pulse.

 The resonant effect is also achieved by separating the block from the array by preliminary simultaneous blasting of auxiliary charges in the contouring vertical and horizontal wells.

 Creating a resonant effect contributes to a more uniform intensive crushing of rocks due to the interaction of direct and reflected blast waves, enhancing the energy potential of the explosion.

PRI me R. The block has the following dimensions: length 50 m, width 50 m, height 15 m. Young's modulus 6.2 · 10 ¹⁰ Pa, rock density 2.6 t / m ³ . The average velocity of longitudinal waves in the massif is 3600 m / s. The duration of the compression phase of the explosive pulse, determined by the formula (1), is 8.0 ms. The delay time interval between the explosion of the last n rows and (n-1) rows, determined by formula (2), is 21.1 ms.

Claims (2)

 1. METHOD OF BREAKING OUT ROCKS, including drilling in a block placed in rows parallel to the edge of the ledge of the main vertical wells, loading them with explosive and orderly short-blasting, characterized in that the block is contoured by drilling vertical and horizontal additional wells to create shielding gaps in the block, after which simultaneous blasting of additional wells is carried out, and the rows of the main vertical wells are blown alternately, starting from the last row from free slope ledge surface, with an estimated duration of explosion of the compression phase to create a resonance effect due to the coincidence of the block forced oscillations with its natural frequency.  2. The method according to claim 1, characterized in that the rows of the main wells begin to explode with a deceleration interval determined by the wave propagation time from the last nth row to the free surface of the slope of the ledge, reflection from it and at the time the reflected waves arrive at the penultimate (n -1) -th row make it explode, and subsequent rows explode similarly.

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