Determination of the seismic effect of a mass explosion on the earthquake resistance of ledges of block products

The publication examines the impact of seismic waves from the mass detonation of the gravel section of the quarry on solid areas suitable for extracting dimension stone in the conditions of the Leznikivsky quarry (Ukraine). Seismic measurements in the quarry were analyzed. Based on the obtained data, seismic-safe zones for mass detonations of gravel sections were identified, and the maximum allowable charges of explosive materials in a single borehole were calculated.


Introduction
From the analysis of seismic-safe methods of blasting operations, it is established that all of them are designed only for quarries with the same production profile of both ore and nonmetallic deposits.Due to the fact that parallel extraction of block and crushed stone products is carried out within the same granite deposit of Leznykivskyi quarry JSC , the study to determine the influence of the seismic effect of a mass explosion on the seismic stability of ledges of block products becomes of significant practical importance.
Therefore, ensuring the integrity of the massif requires conducting research in this direction, taking into account the requirements for parallel extraction of crushed stone products [1][2][3].
Scientific works were carried out to determine the influence of the parameters of blasting operations on the seismic state, on the levels of stress concentration, zones of location of block stone ledges during parallel extraction of block and crushed stone products within the same granite deposit of Leznykivskyi quarry JSC [4][5][6][7][8][9][10][11].

Work procedure
To study the effect of the seismic wave that occurred as a result of a mass explosion on the block section, the MiniMate Plus seismic station and the SM-3 and SM-3B seismic receivers were used, and the recorder was an analog-to-digital converter of the E-440 ADC.The vertical distance between the sites where crushed stone and natural stone blocks are mined was 195 m.The crushed stone section was at +158 m, and the block section was at +190 m (figure 1).58 well charges loaded with explosives "Anemiks-70" 17.5 kg/m were detonated, according to a diagonal scheme (13 groups of 4 wells and 1 in a group).The last well No. 58 was initiated at a deceleration interval of 200 ms after all 57 well charges were initiated.The mass of the explosive charge in one well ranged from 221.0 to 248.0 kg, and in the maximum group of the 4 well order with a total mass of 972 kg.The total mass of all charges is 13696 kg.When recording the parameters of seismic waves that arose from the action of a mass explosion, the SM-3 and SM-3B seismic receivers were installed on a granite base of high mark +190.36 ma site for the extraction of granite blocks, at distances of 295-195 m from the block that was blown up in an easterly direction.

Results and discussion
Parameters of seismic waves within the same granite deposit of Leznykivskyi quarry JSC, which occurred during a massive explosion in the quarry, obtained from sensors with analog-to-digital equipment (installed on the high mark +190) are shown in table 1 (spectrograms in figure 2).Using the values of the granite displacement rates obtained from a mass explosion in the quarry of Leznykivskyi quarry JSC, it became possible to express them as a dependence on the distance reduced to the charge in the following form: • along the profile line, which is located parallel to the extension of the opened cracks for the granite quarry of Leznykivskyi quarry JSC (from reduced to a charge of Q = 248 kg) 1,56 • along the profile line, which is located perpendicular to the extension of the opened cracks for the • along the profile line, which is located parallel to the extension of the opened cracks for the granite quarry of Leznykivskyi quarry JSC (from reduced to a charge of Q = 102,5 kg) • along the profile line, which is located perpendicular to the extension of the opened cracks for the granite quarry of Leznykivskyi quarry JSC (from reduced to a charge of Q = 102,5 kg) The dependence of the modules of the oscillation velocity vector on the reduced distance is shown in figure 2.
The maximum modulus of the oscillation velocity vector obtained from seismic receivers without filtering them (at Q = 102.5 kg) is described by the formula: The maximum modulus of the oscillation velocity vector obtained from seismic receivers without filtering them (at Q = 248 kg) is described by the formula: The maximum modulus of the oscillation velocity vector obtained from seismic receivers with filtering of 50 Hz (at Q = 102.5 kg) is described by the formula: The maximum modulus of the oscillation velocity vector obtained from seismic receivers along the profile, respectively, parallel and perpendicular to the extension of the opened cracks, is shown in figure 3.Although the amplitudes of the maximum time parameters of seismic waves obtained at the +158 m (the site of a mass explosion (0.028-0.037 s)) are also close to the natural vibrations of individual blocks, but as a result of the transformation of seismic waves through the extinguished ledges, the marks of +171 m, +184 m and +198 m to the high mark +190 m, where the seismic receivers were installed, the oscillation spectrum shifted to the high-frequency region figure 3.
The assessment of the seismic state of block stone ledges, which are characterized by the formation of radial cracks from the action of tangential stresses, is carried out according to the method given in [1].
In case of mass explosions [12,13], on the site of a quarry field for the development of granite for crushed stone, the effect of seismic waves on the speed of displacement of soil particles, which is transmitted to the granite array of block stone from the high mark +158 m (explosion site) through extinguished ledges of high mark +171 m, +184 m, and +198 m should not exceed the critical value of the quantity.We provided a seismic state with stress concentration levels acceptable for block stone ledges.
There are additional difficulties in calculating the critical velocity for rock in the surface layer.Firstly, here the rock is in a less favorable stress state, since the stress wave, in which radial compression stresses prevail, will be reflected from the open surface, turns into a stretching wave with the same amplitude, so that the critical velocity must be estimated by a different formula and be less in absolute value.
Secondly, in the surface layer, the rock's tensile strength is significantly lower than in the deep layer, since this layer is more susceptible to external influences (weathering, unloading phenomena, residual phenomena from previous explosions, especially in the overdrill zone, etc.).
Finally, the surface layer undergoes not only dynamic action from seismic waves, but also quasistatic piston action from compressed gases i.e. products of the explosion.This impact causes the formation of obvious and potential explosion craters that spread over the surface far enough away from the epicenter of the explosion.
The method of predicting seismic safety parameters of explosions on block stone ledges is based on the use of analytical and experimental studies of the effect of seismic waves caused by mass explosions in a granite quarry for crushed stone.
When conducting analytical studies of the seismic effect of mass explosions on the site of a quarry field for the development of granites for crushed stone, on the integrity of ledges of a granite massif of block stone, we first determine the speed of vibrations on these ledges by the formula: where х у U -speed of vibrations acting on granite ledges of block stone, cm / s; х s p U .-the speed of vibrations of granite in a volumetric seismic wave (P, S) on the bench-floor of granite ledges, cm / s; λseismic wave length, m; h-distance from the bench-floor of granite ledges to the ledge, m.The stress on the ledges of a block stone can be obtained using the well-known Landau-Lifshitz dependence: where  voltage on block stone ledges, Pa;  speed of propagation of seismic waves, m/s; volume weight of granite, kg / m 3 ;  = 9.81 m / s 2 .
Then the condition of equality of seismic forces due to the action of tangential stresses and the time resistance of the rock to break [ р ] is described by the formula: Here is an example of calculating seismic forces from the action of mass explosions that are carried out on the site of a quarry field for the development of granite for crushed stone, on the integrity of ledges of a granite massif of block stone: 1.The speed of vibrations on granite ledges of block stone caused by the action of a mass explosion on 15.08.18 in a quarry for the extraction of granite for crushed stone according to the formula:    =  .   −1,7ℎ/ = 1,24 −1,7•20/160 = 0,8 • 1,15 = 0,93, cm/s.
where   = 0,8 см/с is maximum value of the volume wave oscillation rate on the Earth's surface of the granite base of high mark + 190 of bench-floor of granite block ledges (distance 20 m to the ledge), obtained from the waveform of a mass explosion in a granite quarry for crushed stone.
Taking the ratio of dynamic forces to static ones as 1.8, it is possible to calculate the stress from seismic actions of waves on the bench-floor of ledges of granite blocks: 2. The condition of equality of seismic forces due to the action of tangential stresses and the time resistance of the rock to break [ р ] is described by the formula: Thus, it is possible to conclude that volumetric seismic waves at reduced distances of 12.6 -24.9 m / kg 1/3 act on the bench-floor of the ledges of the faces for the extraction of blocks with voltage   = 4,8 • 10 −3 МПа, which is 57 times (2.77MPa/0.048MPA = 57) less than the breaking resistance of rock ledges [ р ].These calculations based on the use of data from seismic measuring equipment showed that the mass explosion in the quarry for the extraction of granite on crushed stone of Leznykivskyi quarry 1319 (2024) 012005 IOP Publishing doi:10.1088/1755-1315/1319/1/0120057 JSC does not affect the stability of the ledges of granite blocks, and has a large margin of stability, which makes it possible to bring the site of blasting operations even closer to the quarry field for the extraction of granite blocks, as well as the ability to increase the scale of mass explosions at all sites.
It is established that the nature of the distribution of isolines around the explosion of explosive charges, the corresponding level of seismicity, for granite massifs of the Ukrainian crystal shield (UKCS) has an ellipsoid shape, which is why in quarries where these granites are being developed, the seismic-safe boundary is outlined in the form of an ellipse.The construction of the latter was based on conducting special scientific and experimental studies, as a result of which the following method of analytical and experimental calculation of the size of seismic-safe zones was developed for specific geological and tectonic conditions of blasting the quarry of Leznykivskyi quarry JSC.This method of constructing ellipsoid seismic safety boundaries includes steps related to analytical calculations of the radius of a large R1 and small R2 axes of the seismic safety zone according to the formulas: where Ky is the coefficient that takes into account the explosion conditions; K1, K2proportionality coefficients, respectively, of the parallel and perpendicular extension of the opened cracks m n+1 / s * kg n/3 ; [V]permissible displacement speed of rock particles, m / s; 1; 2indicators of attenuation degrees, respectively, parallel and perpendicular stretching of the opened cracks; Q is the mass of the explosive substance per deceleration, kg.
Experimental studies have determined the proportionality coefficients K1, K2 and indicators of attenuation degrees 1, 2.
And to determine the seismic-safe distance R, (m) in a fractured array in different azimuthal directions from the epicenter of the explosion is determined by the formula: where corresponding to the polar angle (degrees) between the radius of the isoseism zone and the profile that is parallel to the extension of the opened cracks.
Figure 4 shows isolines of seismic-safe charge masses on the 3rd horizon of the Leznykivskyi quarry JSC.When constructing the seismic safety limit, the above formulas were used, which made it possible to establish that earthquake-prone zones have elliptical boundaries around the explosion of the explosive charge in an anisotropic array.Moreover, the major axis of the ellipse coincides with the direction of the main fracturing system of the quarry.
Data for calculating the seismic safety distance R, radii of large R1 and small R2 the axes of the seismic safety zone for permissible [V] values and critical oscillation rates (crack formation zones) are shown in table 2, 3, respectively.The method for constructing an ellipsoid isoseism zone with the central epicenter of the explosion, i.e. when it coincides with the center of the ellipse, is discussed above.But in practice, most often, depending on the conditions under which, for example, the direction of initiation of borehole explosive charges in the block that is being blown up changes, the ellipse, delineating the seismic safety limit, can shift relative to the center of the block that is being blown up.At the same time, depending on the location of protected objects, the latter will be in conditions of seismic load on them, that is, they are exposed to earthquake danger or not.A map of the seismic protection zone of the eastern block section with isolines of the permissible maximum masses of the explosive charge per deceleration is shown in figure 5.The parameters of explosive loads, the degree of influence of which is estimated, include the values of amplitudes and durations of loads, which are determined by the amount of explosive substance detonated in the deceleration stages in each block, as well as the number of loads that depend on the number of deceleration stages and the number of blocks that are blown up.
Effective reduction of the intensity of the seismic and destructive impact of a mass explosion on the rock in the quarry field area, which is intended for the extraction of conditioned blocks, is achieved by: • compliance with the seismic-safe technology of mining blasting blocks on the site of a quarry field for the extraction of granite for crushed stone in the quarry of Leznykivskyi quarry JSC.• applying the direction of chipping granite onto crushed stone perpendicular to the main fracturing system, which will reduce the size of the protective rear sight between the sites;

Conclusions
Based on the conducted research, seismic-safe technologies for conducting short-delayed explosions have been developed for designing mass explosions in a quarry, in which the optimal parameters of the maximum mass of the explosive charge, detonated simultaneously in a group, are determined, and which do not exceed the level of crack formation determined in the work on the slopes of the block stone.An algorithm for calculating and constructing isolines of permissible explosion scales with correction of their parameters is developed with an approach up to the rear-end development of each horizon of the site for the extraction of crushed stone products from the quarry of Leznykivskyi quarry JSC.
It is proved that the use in a certain combination of the developed seismic-safe methods of technological destruction of rock mass into crushed stone is possible to simultaneously preserve the integrity of the block mass for the associated extraction of blocks.

2 Figure 1 .
Figure 1.Mining plan of the granite deposit of Leznykivskyi quarry JSC and installation scheme of seismic equipment 1-4-numbers of seismic receivers SM-3.

Figure 2 .
Figure 2. Spectrograms of seismic vibrations (channels, ch. 1, 2, 3 from top to bottom) obtained from spectral analysis of seismograms during a mass explosion in the quarry of Leznykivskyi quarry JSC.

3 )Figure 3 .
Figure 3.The dependence of the modules of the oscillation velocity vector on the reduced distance 1 -the maximum modulus of the oscillation velocity vector obtained from seismic receivers without filtering them (at Qef = 102.5 kg), 2 -the maximum modulus of the oscillation velocity vector obtained from seismic receivers

Figure 4 .
Figure 4.The dependence of the modules of the oscillation velocity vector on the reduced distance 1, 2 -maximum modules of the oscillation velocity vector obtained from seismic receivers along the profile, respectively, parallel and perpendicular to the extension of the opened cracks for Leznykivskyi quarry JSC (at Qef = 102.5 kg).

Figure 5 .
Figure 5. Diagram of isolines of seismic-safe charge masses.

9 Figure 6 .
Figure 6.A map of the seismic protection zone of the eastern block section with isolines of the permissible maximum masses of the explosive charge per one deceleration .• application of short-delayed blasting schemes existing at the quarry, the explosion of charges of which is excited by volumetric seismic waves, at reduced distances of 12.6-24.9m/kg 1/3 , and which act on the bench-floor of the ledges of the faces from the extraction of blocks with voltage   = 4,8 • 10 −3 MPа, which is 57 times (2.77MPa/0.048MPa = 57) less than the breaking resistance of rock ledges [σ р ].This indicates a multiple reserve of seismic resistance of block stone granites.

Table 1 .
Maximum values of the rate of vibrations of particles of the granite bench-floor for the extraction of block products during an explosion (in modulus).Distances are determined taking into account the installation of sensors on the high mark +198 m. 3

Table 2 .
Data for calculating the seismic safety distance R, radii of large R1 and small R2 axes of the seismic safety zone for permissible values of oscillation velocities [V].

Table 3 .
Data for calculating the seismic safety distance R, radii of large R1 and small R2 axes of the seismic safety zone for permissible values of oscillation velocities [V].