IMPROVEMENT OF THE METHOD OF DRILLING AND BLASTING OPERATIONS AT THE USE OF EXPLOSIVE SUBSTANCE «UKRAINITE» IN UNDERGROUND MINING WORKS

The object of research is a rock massif of iron ore, which is destroyed by an explosive located in deep wells. One of the most problematic places is ensuring uniform grinding of the rock massif during underground mining of mineral deposits at great depths. In the Kryvyi Rih iron ore basin (Kryvyi Rih, Ukraine) in underground mining let’s use the Ukrainian-made Grammonite 79/21 explosive, which provided an opportunity to obtain high-quality grinding of the ore mass to a depth of 1200 m. With a decrease in mining, these indicators deteriorate significantly, due to the manifestations of rock pressure, which leads to the overcoming of wells and increased specific charge for blasting. A comprehensive method is used based on an analysis of existing methods that affect the specific charge of an explosive. According to practice data, it is found that when using an emulsion explosive in mining operations, the specific consumption of an explosive decreases, while the cost of extraction decreases and the quality of grinding of the massif improves. However, due to the lack of a methodology for calculating the parameters of drilling and blasting operations, the «Ukrainite PP-1» emulsion explosive is not widely used. The development of the methodology taking into account the characteristics of the «Ukrainite PP-1» emulsion explosive will improve the extraction of ore mass. It is shown that the use of «Ukrainite PP-1» emulsion explosive leads to a decrease in the total length of wells by 35 %, and a decrease in production costs. This is due to the fact that the proposed method of calculation has the peculiarity of taking into account the specific costs of emulsion explosives obtained by pilot tests, in particular, the efficiency coefficient of emulsion explosives. Due to this, the costs of drilling and blasting work are reduced and it is possible to obtain a calculated economic effect from the introduction of this technology at the level of 0.6 c. u./t. The proposed pattern of drilling the massif by the downward fans, compared with similar known, can reduce the time for drilling and improve the grinding of the rock massif without changing technology.


Introduction
Currently, the underground mining of the Kryvyi Rih iron ore basin (Kryvyi Rih, Ukraine), the extraction of minerals is carried out by traditional development systems using drilling and blasting operations [1,2]. Further de velopment of mineral deposits at greater depths of more than 1260-1350 m leads to an increase in the cost of production due to specific costs: transportation and enrich ment of the ore mass; on drilling and blasting [3,4]. The destruction of the rock massif is carried out by drilling fans of deep wells 35-50 m long, and their simultaneous detonation with deceleration. For drilling of a mountain massif, НКР100МПА or КБУ (Ukraine) drilling ma chines are used, which require considerable time to drill wells in the refining unit. This leads to the destruction of the drilled wells of the total volume according to the practice of 10-15 %.
In order to reduce the losses of drilling wells and the undermining of the massif is performed in two or more stages, this leads to an increase in time for the unit and the reduction of labor productivity in the system.
The solution to this problem is possible by reducing the volume of the cleaning unit, the use of selfpropelled drilling equipment and more efficient explosives.
Thus, in openpit mining, high rates are achieved when using an emulsion explosive (EE) «Ukrainite PP1» (Ukraine). In underground mining, when sinking workings instead of ammonite6ЖВ EE (Ukraine) is used in the form of «Ukrainite PP1» cartridges, which makes it possible to reduce the cost of sinking workings and improve the quality of ore grinding.
However, the method of determining the parameters of drilling and blasting operations when used in under ground mining works of «Ukrainite PP1» EE in the massif collapse.
Therefore, the improvement of the existing methodo logy [5] to determine the parameters of drilling and blasting operations for the emulsion explosive «Ukrainite PP1» is an actual problem. TECHNOLOGY AUDIT AND PRODUCTION RESERVES -№ 6/1(44), 2018 ISSN 2226-3780

The object of research and its technological audit
The object of research is a mountain massif, which is destroyed by an explosive located in deep wells. One of the most problematic places is ensuring uniform grinding of the rock massif during underground mining of mineral deposits at great depths.
In underground mining of ore deposits, the following methods of ore blasting are used: drill, borehole, mine or concentrated charges [6,7]. There are also other methods of blasting, which are used in the development of coal and polymetallic ores [8,9]: -underground combines and complexes; -jackhammers; -selfcrushing ore; -hydraulic breakage; -electrophysical methods (high frequency currents, ultrasound, laser); -nuclear explosions; -thermal blasting. Underground mining of a complex structural reservoir of the Kryvyi Rih iron ore basin, systems of surface or subsurface massive collapse of ore and overburden or sys tems with an open clearing space and subsequent collapse of the pillars are used [10,11]. Depending on the mining and geological conditions in the mines, the following breaking systems are used for these development systems, the main of which are: deep well fans, deep well bundles and paral lel wells. Also, the blasting can be carried out on the vertical, horizontal and inclined compensation space, as well as on the «clamped medium» [12,13].
At most mining enterprises of the Kryvyi Rih basin, massifs are used by vertical fans of deep wells on a vertical compensation chamber 10-15 m wide, located across the field strike [14,15]. Under conditions of significant rock pressure in weak unstable rocks, the blasting is carried out on a cutting gap 5-6 m wide and splitting the floor into two, three subfloors (Fig. 1).
The method of ore blasting by vertical fans of deep wells to the vertical compensation space has found the widest application ( Fig. 1). This blasting scheme in the develop ment of iron ore deposits is used by 40-50 % of the known.
The essence of this option is as follows: a cutting slot is formed in the center of the unit, a drilling drift with a crosssectional area of 9 m 2 , from which vertical fans of ascending wells are drilled, lie in the lying side.
The advantages of this option blasting include: a smaller amount of drilling workings; fewer permutations of the НКР100МПА drilling machine; additional grinding of ore due to collision of pieces of ore during blasting of opposite fans of deep wells.
Disadvantages: uneven crushing of the massif (remilling ore at the beginning of the wells and increased oversize at the ends of the wells) increases costs of deep wells.
It is possible to reduce the specific costs of deep wells by changing the parameters of the well breakdown, which include: -well diameter (d); -the shortest distance from the axis of charge to the exposed surface (least resistance line, W); -distance between the ends of the wells (a); -ore outburst from 1 m well (λ); -specific explosive charge (q), which depend on the blasting schemes. At the same time, weighty parameters that affect the quality of breaking are the least resistance line (LRL) and the distance between the ends of deep wells, which depend on the well diameter, the efficiency of the used explosive.
The well diameter can't be changed, since the НКР 100МПА drilling machine drills a well only 105 mm. There fore, the only active factor is the change in the explosive, which has the highest performance at the lowest cost. «Ukrainite PP1» explosive is included to such explosives However, the use of the «Ukrainite PP1» explosive in the collapse of the mountain massif in underground mining operations in the absence of a methodology for determining the parameters of drilling and blasting operations will in evitably lead to a deterioration in the conditions of release and delivery. This, in turn, will not reduce, but increase the cost of mining the ore mass. The existing method [5], developed for the Grammo nite 79/21 explosive, is not suitable for determining para meters when using the Ukrai nite PP1 emulsion explosive, which has other explosive cha racteristics.

The aim and objectives of research
The aim of research is im proving the methods of drilling and blasting operations by de termining the least resistance line when using the «Ukrai nite PP1» explosive substance in underground mining. To achieve this aim it is necessary to perform the fol lowing objectives: 1. To justify the value of least resistance line in un derground mining when using emulsion explosive.
2. To develop a scheme for breaking the mountain mas sif using the «Ukrainite PP1» emulsion explosive.

Research of existing solutions of the problem
The authors of [16,17] make a significant contribu tion to the development of the theory of destruction of a mountain massif by developing a methodology for deter mining the parameters of drilling and blasting operations. But the proposed schemes and methods of blasting, charge structures, methods of blasting wells take into account the deterioration of mining and geological conditions with the deepening of underground mining.
In the conditions of the Kryvyi Rih, Zaporizhzhia, Smolyn fields (Ukraine), a well is widely used. There are a large number of borehole blasting schemes, the main of which are: parallel wells, beams of parallelclose wells, fans of deep wells and beams of deep wells. Also, the blasting can be carried out on the vertical, horizontal and inclined compensation space, as well as on the «clamped medium» [11,18].
From the above analysis it is clear that most of the methods for determining the LRL value do not take into account the properties of the explosive or have a large number of coefficients that need to be refined by indus trial research [19,20].
At the Kiruna mine (Sweden), the parameters of drilling and blasting operations are determined and refined in the process of underground mining with industrial explosions of 2-3 fan wells [21,22]. But the disadvantage of this method is that it is impossible to destroy the cleaning unit by a massive explosion due to the use of end release. Thus, when developing unstable ore bodies, the cost of ore extraction will significantly increase due to additional measures to support mine workings.
An alternative option for mining ore is a development system that is implemented at the Kidd Creek mine (Ca nada). This development system after the formation of the camera provides for its bookmarks. This allows to reduce the pressure around the clearing workings, but 2-3 times increases the cost of production, and also requires control over mountain ranges [23,24].
However, due to the mining and geological and techno logical features of the underground mining of the Kryvyi Rih iron ore basin, the introduction of highperformance technologies will inevitably lead to a significant increase in production costs.

Methods of research
There are many methods for calculating the parameters of drilling and blasting operations, which are based on the principle of determining the necessary energy for the destruction of a certain volume of massif with specific physicomechanical properties.
With known (adopted according to the practice in similar conditions) specific charge of the explosive on the blasting -q (kg/m 3 ), the least resistance line is deter mined by the formula [1,7]: where d -the well diameters, m; Δ -EE loading density of BP, g/cm 3  . , m, where b -EE relative power factor; k f -the coefficient of the massif fracture (k f > 1 for large unit and k f < 1 for small unit structure of cracks in the massif); a s -size of the standard piece, m; H -the design output of oversize, %. The Research Mining Institute of the State Higher Educational Institution «Kryvyi Rih National University» (Ukraine) recommends determining the least resistance line, taking into account the blasting direction, type of explosive and its uniform distribution in the massif ac cording to the formula [13,18]: where k m -the coefficient taking into account the blasting direction (when blasting by horizontal and vertical layers and f < 10 k m = 1.0, and when blasting by vertical layers and f > 10 k m = 0.9); r -the coefficient of uniform distribution of the explosive in the massif. For the conditions of the Kryvyi Rih iron ore basin, the parameters of drilling and blasting operations are de termined by the strength of rocks, using the explosive ness index of the rocks and the reduced charge diameter according to the formula [5,16]: where k h = 0.9-1.0 -massif heterogeneity coefficient; С 0the indicator of rock explosiveness; D r -the reduced well diameter, m. Taking into account the stresses acting in the massif, the magnitude of the least resistance line is determined by the formula [20]: where W f -LRL, which is determined by the formula (4); K s -the coefficient of energy intensity of breaking of strained rocks, equal to the ratio of the specific charge of the explo sive, which are set taking into account the depth of mining works and the size of the clearing space q s to the EE specific charge, which are determined by the strength of the rocks q f .

Research results
After performing the calculations of the least resistance line according to the formula (4), the LRL dependences on TECHNOLOGY AUDIT AND PRODUCTION RESERVES -№ 6/1(44), 2018 ISSN 2226-3780 the well diameter and the coefficient of strength of rocks using M. M. Protodyakonov's scale are constructed (Fig. 2).
From the above dependences it is possible to see that with increasing ore strength, the least resistance line de creases, which corresponds to the experience of mining iron ores of the Kryvyi Rih iron ore basin when using the Grammonite79/21 explosive.
Specific explosive charge is determined by the formula: where k f = 0.65...0.95 -the fill factor of the wells with an explosive; U -explosive capacity in 1 m well, kg; а -the distance between the ends of the wells, m; g -volume weight of ore, t/m 3 . However, increasingly, mining companies with an un derground mining method are trying to reduce the cost of ore mining due to various factors. One of such is the introduction into the production of emulsion explosive «Ukrainite PP1» [19,25].
This explosive in the implementa tion in open pit mining shows high performance. Due to the high energy of the explosion, the least resistance line and the distance between the ends of the wells are increased.
Indicators of specific charge from the implementation of the emulsion explosive «Ukrainite PP1» are shown in Fig. 3. From Fig. 3, it can be seen that the specific charge of emulsion ex plosives across enterprises vary from 0.771 to 1.427 kg/t and on average amount to 1.008.
Let's determine the specific charge of explosive according to the formu la (6) with a well diameter of 250 mm. The calculation results are shown in Fig. 4. From Fig. 4 it is possible to see that according to the calculation data according to the method of [5], the well diameter does not significantly affect the specific explosive consumption. At the same time, specific charge increases from 0.5 to 0.8 kg/t, which is 0.4 kg/ton less than during blas ting in opencast mining, therefore, the method of drilling and blasting [5] requires improvement. Considering the fact that during the breaking of the ore mass of the «Ukrainite PP1» emulsion explosive the specific expenditure is much less than with a granulated explosive. There fore, it is necessary to take into ac count in the formula (4) the efficiency coefficient of the emulsion explosive, the least resistance line is determined by the expression: where K EE -coefficient of performance of the emulsion explosive.  The coefficient of performance of the emulsion explosive is determined by the formulas: -at q f < q ee : -at q f > q ee : where q f -EE specific charge are determined by the for mula (6), kg/t; q EE -the specific charge of explosives, kg/t (taken according to the practice of open mining (Fig. 3), or 1.008 is taken.
Having performed the calculations using formula (7), taking into account (8) or (9), the dependences of the least resistance line on the well diameter and the strength coefficient of the ore (Fig. 5) are constructed.
From the graphs shown in Fig. 5, it is possible to see that the value of the least resistance line decreases with increasing rock strength, and increases with increasing well diameter. Comparing the dependen cies shown in Fig. 2 and Fig. 5 it can be seen that when using the «Ukrainite PP1» emulsion explosive, the least resistance line increases by 0.3-0.5 m with a well diame ter of 105 mm.
At the same time, the specific charge of explosives from the well diameter and the strength of the massif using the Pro todyakonov's scale, are shown in Fig. 6. The height of the unit is taken from practical expe rience -80 m, in the unit under the floor of 35 m each. The system for developing the sublevel chamber collapse of ores and country rocks from blasting deep wells to the vertical compensation space is shown in Fig. 7.
The parameters of drilling and blasting operations are calculated using an improved method without taking into account the stressstrain state of the rock massif. According to the characteristics of the massif and the efficiency of the «Ukrainite PP1» emulsion explosive, the least resistance line is 3.4 m, the distance between the ends of the wells is 3.1 m, and the radii of undercharging around the drill drift are W = 3.4 m and 1·5·W = 5.1 m.
The results of the calculations of drilling and blas ting operations when applying the methodology [5] for Grammonite 79/21 and Ukrainite PP1 explosives and the improved technique for applying the Ukrainite PP1 emulsion explosive are given in Table 1.
It has been established that when using the «Ukrai nite PP1» emulsion explosive in underground mining ope rations with the parameters of drilling and blasting opera tions [5], it will lead to ore overbreaking. This will reduce the productivity of labor on delivery, especially in the flooded units.

SWOT analysis of research results
Strengths. Improving the methods of drilling and blas ting operations by applying the efficiency coefficient of the emulsion explosive will increase the least resistance line and the distance between the ends of the wells. It should be noted that the unit costs of the «Ukrai nite PP1» emulsion explosive will be equal as in the case of using the Grammonite 79/21 EE with the same oversize output.
Weaknesses. The use of «Uk rainite PP1» emulsion explo sive in underground mining will inevitably lead to the following negative consequences: -increase in energy con sumption and labor re sources in the drilling of downhole deep wells with the НКР100МПА ma chine; -increase in labor re sources and the number of electric detonators that need to be placed in the wells.
Opportunities. According to the results of the calcula tions, the approximate eco nomic effect of the use of the «Ukrainite PP1» explosive will be 0.12 c. u./t compa red to Grammonite 79/21, or 126 c. u. in the calculated unit. With an annual mine output of 2.4 million t/year, the an nual economic effect will be 203333 c. u.
The estimated specific eco nomic effect from the intro duction of an improved me thod of drilling and blasting operations into production for the «Ukrainite PP1» explo sive will be 0.6 c. u./t, and the annual 1.44 million c. u.
It should be noted that the «Ukrainite PP1» emul sion explosive compared with Western counterparts is much cheaper with the same techni cal characteristics.
Threats. When using emul sion explosives in underground mining in highly fractured mas sifs, there is a possibility of its spreading over cracks, which will lead to oversaturation of the massif with an explosive substance. This will lead to an increase in the cost of ore mining by 5-20 %.

Conclusions
1. As a result of research, it has been established that when using «Ukrainite PP1» emulsion explosive in underground mining, the least resistance line increa ses 1.1-1.4 times compared to the Grammonite 79/21 explosive.  Note: * -when calculating the parameters of drilling and blasting operations according to the method [5] ISSN 2226-3780 2. A scheme has been developed for breaking the moun tain massif into descending fans of deep wells, which makes it possible to use the «Ukrainite PP1» emulsion explosive and obtain a calculated economic effect of 0.6 c. u./t.