RU2381369C1 - Method for prevention of rock bursts in rocks of mine soil - Google Patents

Method for prevention of rock bursts in rocks of mine soil Download PDF

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RU2381369C1
RU2381369C1 RU2008134738/03A RU2008134738A RU2381369C1 RU 2381369 C1 RU2381369 C1 RU 2381369C1 RU 2008134738/03 A RU2008134738/03 A RU 2008134738/03A RU 2008134738 A RU2008134738 A RU 2008134738A RU 2381369 C1 RU2381369 C1 RU 2381369C1
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wells
layer
mine
hard rock
soil
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RU2008134738/03A
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Сергей Вадимович Цирель (RU)
Сергей Вадимович Цирель
Дмитрий Владимирович Яковлев (RU)
Дмитрий Владимирович Яковлев
Николай Владимирович Кротов (RU)
Николай Владимирович Кротов
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Открытое акционерное общество "Научно-исследовательский институт горной геомеханики и маркшейдерского дела - Межотраслевой научный центр ВНИМИ"
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Abstract

FIELD: mining.
SUBSTANCE: invention is related to mining industry for maximum unloading of mine soil rocks, which are inclined to dynamic destructions. Method for prevention of rock bursts in rocks of mine soils, including drilling of wells into layer of hard rock, their charging and explosion of explosive charges. In lower part of layer, wells are charged with more powerful charges and exploded in tillage mode, and in upper part pf layer wells are charged with reduced charges, and controlled blasting is carried out. Wells in upper part of hard rock layer are charged in a row. Wells are arranged in rows symmetrically versus longitudinal axis of mine. Wells are drilled pairwise at the angle to mine soil in plane of mine cross section. Wells are drilled pairwise at the angle versus mine soil in planes arranged at the angle to plane of its cross section. Wells are drilled in such a manner so that they cross vertical plane, passing through longitudinal axis of mine, at the height of 0.15-0.25 m from lower limit of hard rock layer, where m is layer strength.
EFFECT: invention provides for increased efficiency of dynamic events prevention in mine soil and safety of mining works execution due to differential softening of some parts of hard rock layer, which lies near mine soil.
5 cl, 3 dwg

Description

The invention relates to the mining industry and can be used to prevent rock blows in coal mines and mines, accompanied by dynamic destruction of the mine workings.
There are a number of ways to prevent rockfalls in mine workings using unloading of a layer of rocks using blasting, for example, a method of unloading a near-edge array of mine workings according to RF patent No. 2078927, IPC E21C 41/18, F42D 3/04, publ. 05/10/1997, including the drilling of wells in the zone of concentration of tensile stresses in the plane of natural collapse, the formation of initial cracks, the sealing of wells and injection of fluid in them in the hydraulic fracturing mode of the main roof. In this case, the initial cracks are formed by placing and blasting in each well a cumulative explosive charge of a special design, the cumulative recess of which is oriented along the axis of the mine.
There is also a method of preventing dynamic phenomena in the development of coal seams according to the patent of the Russian Federation No. 1798523, IPC E21F 5/00, publ. 02.28.1993, according to which wells are drilled into the host rocks, a water-containing liquid explosive substance (BB) is pumped through these wells to areas of weakened contacts of the host rock layers, and the wells themselves are filled with a thickened explosive mixture. The softening of the rocks is carried out by the explosion of a water-containing explosive, and the initiation of the explosion is carried out non-electric way.
However, all these methods do not provide a sufficient degree of unloading of the host rocks of the mine and do not completely eliminate the likelihood of rock impacts, especially in areas where the hard rock layer is located in close proximity to the mine soil.
The closest in technical essence is a method of preventing rock impacts in mine workings by unloading a layer of hard rock using camouflage blasting, including drilling wells, loading and blasting explosive charges using the technology of hydromicrotorpeding (see "Prevention of gas-dynamic phenomena in coal mines" / Coll Auth. - M.: Scientific and Technical Center for Safety in Industry of the Gosgortekhnadzor of Russia, 2004, pp. 117-118).
The disadvantages of this method are the low efficiency of the destruction of the hard rock layer, due to the fact that blasting is carried out with the same power parameters of camouflage charges along the entire length of the wells, which leads, on the one hand, to insufficient unloading of the hard layer and thereby increase the likelihood of rock impact, on the other hand, to an excessive consumption of explosives, and in workings hazardous for explosion of gas and dust, also to excessively intense outflow of gas and hot explosion products, which increases the risk of methane or dust flares.
The invention solves the problem of increasing the efficiency of preventing dynamic phenomena in the soil of mining and safety of mining due to the differentiated softening of individual parts of the layer of hard rock lying near the soil of the mine, from a dangerous concentration of stress.
To achieve the specified technical result, softening of the lower part of the hard rock layer is carried out with more powerful loosening charges, and the upper part - with blasting charges of lower power, while the wells in the upper part of the layer are charged through a series.
In addition, according to the method, the wells are arranged in rows symmetrically with respect to the longitudinal axis of the mine and are drilled at an angle to the soil of the mine so that they intersect the vertical plane passing through the longitudinal axis of the mine at a height h = 0.15-0.25 m from the bottom of the hard rock layer where m is the thickness of the layer of hard rock.
Each pair of wells is drilled at an angle to the mine soil in the plane of its transverse vertical section or in planes located at an angle to the plane of its cross section.
The method is illustrated by drawings, where Fig. 1 shows a vertical cross section of a mine, and Fig. 2 shows a planned position of a mine with drilled and charged wells; figure 3 is a diagram of the destruction in the soil of a mine.
The drawings indicate mining 1, in the rocks of which there is a layer 2 of hard rock, prone to dynamic fracture, in which wells 3 are drilled with enhanced loosening charges 4 in the lower part of layer 2, more powerful than reduced contour charges 5, located at the top of layer 2.
The physical essence of the claimed method proceeds from the features of the formation of hazardous conditions in the soil in a layer of hard rock, i.e. its potential for dynamic fracture in the form of a rock strike. According to the claimed method, directly in the process of blasting, create conditions conducive to the dynamic fracture of a layer of hard rock, which subsequently completely eliminates the risk of rock blows in the soil of development.
The tendency of the rocks to dynamic fracture shows that the rheological behavior of the layers of hard rock in the soil is close to elastic, and, accordingly, as a first approximation, we can consider the solution of the well-known problem of the net bending of a beam fixed at both ends. According to this decision, the beam section is divided by the neutral line 6 into two zones - extended 7 and compressed 8 (see figure 3). In this case, the stretched zone 7 is the upper part of the strong rock layer in the soil, and the compressed part 8 is the lower part.
Accordingly, the cracks 9 created by the explosion open in the upper part of the layer and close in the lower part, which is further facilitated by the pressure of the overlying rock. In contrast to the claimed method, when using the camouflage blasting method using the hydro-microtorpedo technology adopted as the prototype, softening is carried out with the same blasting parameters along the entire length of the wells, as a result of which the destruction in the upper part of the layer is excessive and insufficient in the lower part. Excessive destruction of the upper part leads to an excessive consumption of explosives, and in workings hazardous for explosion of gas and dust, also to excessively intense outflow of gas and hot explosion products, which increases the risk of methane or dust flashes.
Insufficient destruction of the lower part of the hard layer leads to a decrease in the efficiency of solving the main task of preventing rockfalls in the rocks of the working soil - eliminating the conditions for the dynamic fracture of the hard rock layer. This is due to the fact that closed cracks only distance the behavior of a hard rock layer from elastic and reduce the intensity of elastic energy accumulation, but it does not completely eliminate the probability of dynamic phenomena. In addition, the closure of cracks blocks the flow of gases, i.e. gases that did not escape at the time of the explosion and in the near future after it can remain under a layer of hard rock and create excessive pressure.
Therefore, according to the claimed method, contour blasting is used in the upper part of the hard rock layer, i.e. create one or more continuous cracks, and loosening charges are established at the bottom, i.e. completely destroy the hard rock. Tensile deformations in the upper part of the layer reveal cracks created by contour blasting. In the lower part of the layer due to the action of charges of loosening, a destroyed region is created. Strong crushing causes a decrease in the angle of internal friction of rocks (see Belyakov Yu.I., Rezunik A.V. Methods for determining the coefficient of loosening of hard rocks in the collapse // Mountain Journal, 1966, No. 12, p. 18-21) and, accordingly , creates the possibility of slipping sides of the "bridge" relative to each other. When slipping pieces of rock are displaced, and due to dilatancy significantly increases the volume of voids and channels, providing free flow of gases.
Since all wells intended for loosening the lower part of the layer pass through its upper part, it is advisable to use the method of loading through the well to perform blasting. This method ensures the achievement of good separation quality while reducing the specific consumption of explosives by 20-40% compared with the usual one (Brotanek I., Water J. Contour blasting in mining and construction. M: Nedra, 1983, p. 63). In this case, intensive crushing of the lower part of the layer is achieved through the use of more powerful charges and a more frequent arrangement of explosive charges, i.e. in each well.
There are various methods of placing wells for unloading rock mass, for example, by drilling a cluster of wells, either in a staggered manner, or in rows.
With single-row blasting, the only way to increase the power of the explosion is to increase the power of the charges, so it can only be used if a number of conditions are met, in particular the admissibility of using powerful explosives of lower safety classes, relatively low strength and low power of the hard rock layer. In other cases, as a rule, the use of two or three rows of wells is required (two- or three-row blasting).
In principle, in order to carry out the claimed method, as an option, it is possible to drill, for example, three rows of wells drilled vertically into the production soil, located symmetrically relative to its longitudinal axis, loading the wells with two types of charges, as mentioned above, and blasting them. More powerful loosening charges in the lower part of the hard rock layer will create local foci of destruction, partially overlapping, which is achieved by an appropriate calculation of the parameters of the wells. This will significantly reduce the greatest compressive stresses in the lower part of the “beam”, however, the effect of such an impact will still be insufficient to completely eliminate the likelihood of dynamic fractures of the hard rock layer in the working soil.
In a preferred embodiment of the method for creating the effect of the highest concentration of explosives in the most intense lower part of the hard rock layer, as well as in order to optimize the cost of drilling unloading wells, two rows of wells are laid in the production, located pairwise symmetrically relative to its longitudinal axis. Moreover, each pair of wells is drilled at an angle α to the mine soil in the plane of its cross section or in planes located at an angle β to the plane of its cross section.
For more complete destruction of the lower part of the layer of hard rock, the wells must be positioned so that they intersect the vertical plane passing through the longitudinal axis of the working, at a height of 0.15-0.25 m from the bottom of the layer, where m is the thickness of the layer of hard rock.
The choice of the height of the intersection point of the wells is due to the need for the concentration of explosive energy in the lower most stressed part of the hard rock layer and is based on the calculations of the propagation of stress waves, as well as the experience of blasting in explosive rocks (see Efremov E.I., Kharitonov V.N. , Semenyuk IA Explosive destruction of outburst hazardous rocks in deep mines. M: Nedra, 1979) and in open cast mining.
This condition is achieved by drilling wells in pairs at an angle to the soil of the mine, for example, in the plane of the cross section of the mine. The angle of the wells α is calculated by the formula:
Figure 00000001
where m is the thickness of the layer of hard rock; m 1 is the thickness of the overlying layer; d is the width of the output; b = 0.5-1.5 m - the distance from the working wall to a number of wells (determined by the design features of the drilling equipment used); k = 0.75-0.85.
The basis for obtaining this calculation formula is the principle of ensuring approximately equal degree of crushing of the entire lower part of the destructible layer. If the loads were distributed equally over the thickness of the layer, then the place of the highest concentration of explosive charges would have to be in the middle of the lower part of the formation, i.e. at a height of 0.2-0.3 m from its sole. However, since the stresses in the lower part of the formation are higher, to compensate for the increased loads, the optimal location of the zone of the highest concentration of explosives is shifted by 10% of the crushed part thickness of the layer down (see Efremov E.I., Kharitonov V.N., Semenyuk I.A. Explosive destruction of outburst hazardous rocks in deep mines. M: Nedra, 1979). Based on the experience of blasting in opencast mining, the maximum allowable limits for the deviation of the position of the level level of the highest concentration of explosives were determined - 0.15 ... 0.25 m. Based on these considerations and taking into account the design features of the drilling equipment used, the angle of inclination of the wells is determined.
In this case, the calculated total length L of the explosive charge (together with the uncharged gap) will be m / (2 cosα).
The step a between the wells in the plane of the soil, the workings are selected according to the standard method that takes into account the strength of the unloaded rock layer (see Efremov E.I., Kharitonov V.N., Semenyuk I.A. Explosive destruction of outburst hazardous rocks in deep mines. M: Nedra , 1979).
In another embodiment of the inventive method (Fig. 2), in order to achieve the most uniform distribution of explosives over the rock being destroyed, the wells are located not in the plane of the cross section of the mine, but in planes located at an angle to the plane of its cross section, that is, the wells are oriented not only at an angle α to the working soil, but also at an angle β to the plane of its cross section. In this case, the effect of interference of stress waves is provided, which contributes to an increase in the degree of crushing of the rocks of the hard layer.
The angle of inclination of the wells β is chosen in such a way as to ensure the intersection of the horizontal projections of each loosening charge with the horizontal projections of two adjacent loosening charges (as shown in FIG. 2), i.e. the angle β can be calculated from the expression β <arctan (2a cos α / m), while practice shows that β values in the range 40 ° -60 ° are preferred.
The method is as follows.
Wells 3 are drilled into a layer of hard rock 2 into the soil of the preparatory mine 1, placing them at an angle α to the soil of the mine 1 and at an angle β to the plane of the cross section of the mine, while the distance between the reinforced loosening charges 4 in the wells 3 in the lower part of the hard rock layer 2 is taken in half as much as the distance between the reduced contour charges 5 in the wells 3 in the upper part of the layer of hard rock 2, i.e. wells in the upper part of the hard rock layer are charged through a series.
The ratio of the power of loosening charges and contour charges is actually 3 to 10 times and is calculated on the basis of the volume of rocks that must be destroyed, from the conditions of occurrence and the properties of the layer of hard rock. In strong hard-to-explode rocks, this ratio can be 3-4.
In this case, for the wells 3 to intersect the vertical plane passing through the longitudinal axis of the mine 1 at a height of 0.15-0.25 m, where m is the thickness of the hard rock layer, the angle α of their inclination in the plane of the cross section of the mine should be calculated by the formula (1 ), where k = 0.75-0.85, and b = 0.5-1.5 m, depending on the width of the excavation d and the drilling equipment used. The destruction of the layer of hard rock produce simultaneous blasting of explosives in all wells.
Thus, in comparison with the known methods, the use of the claimed method allows to increase the efficiency of preventing rock shocks in the soil of the excavation due to the optimal destruction of individual parts of the layer of hard rock and the maximum displacement of the upper and lower parts of the layer relative to each other over its entire power, and also to increase safety of mining operations by dumping the accumulated elastic energy and the complete outflow of gases accumulated under a layer of hard rock.

Claims (6)

1. A method of preventing rock blows in the rocks of the production soil, including drilling wells in a hard rock layer, loading and blasting explosive charges, characterized in that in the lower part of the layer the wells are charged with more powerful charges and explode in the loosening mode, and in the upper part the layer of the well is charged with reduced charges and contour blasting is carried out.
2. The method according to claim 1, characterized in that the wells in the upper part of the hard rock layer are charged through a series.
3. The method according to claim 1, characterized in that the wells are arranged in rows symmetrically with respect to the longitudinal axis of the production.
4. The method according to claim 3, characterized in that the wells are drilled in pairs at an angle to the mine soil in the plane of the cross section of the mine.
5. The method according to claim 3, characterized in that the wells are drilled in pairs at an angle to the mine soil in planes located at an angle to the plane of its cross section.
6. The method according to claim 3, characterized in that the wells are drilled so that they intersect the vertical plane passing through the longitudinal axis of the excavation, at a height of 0.15-0.25 m from the lower boundary of the hard rock layer, where m is the thickness layer.
RU2008134738/03A 2008-08-28 2008-08-28 Method for prevention of rock bursts in rocks of mine soil RU2381369C1 (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102865080A (en) * 2012-10-08 2013-01-09 中南大学 Induced fracture engineering arrangement and non-blasting mining process for high-geostress hard rock
CN103743302A (en) * 2014-01-13 2014-04-23 中国科学院武汉岩土力学研究所 Deep-tunnel time-space delay type rock burst prevention method
CN103821516A (en) * 2014-03-10 2014-05-28 平顶山天安煤业股份有限公司 Method for preventing rock burst through secondary pressure relief
RU2709848C1 (en) * 2019-04-24 2019-12-23 Федеральное Государственное Бюджетное Учреждение Науки Институт Проблем Комплексного Освоения Недр Им. Академика Н.В. Мельникова Российской Академии Наук (Ипкон Ран) Method for blasting of ores and rocks
RU2740630C1 (en) * 2020-06-02 2021-01-18 Федеральное государственное бюджетное учреждение науки Институт земной коры Сибирского отделения Российской академии наук (ИЗК СО РАН) Method for reduction of excessive elastic energy in deep seismic dangerous segments of fractures

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102865080A (en) * 2012-10-08 2013-01-09 中南大学 Induced fracture engineering arrangement and non-blasting mining process for high-geostress hard rock
CN103743302A (en) * 2014-01-13 2014-04-23 中国科学院武汉岩土力学研究所 Deep-tunnel time-space delay type rock burst prevention method
CN103743302B (en) * 2014-01-13 2015-02-25 中国科学院武汉岩土力学研究所 Deep-tunnel time-space delay type rock burst prevention method
CN103821516A (en) * 2014-03-10 2014-05-28 平顶山天安煤业股份有限公司 Method for preventing rock burst through secondary pressure relief
CN103821516B (en) * 2014-03-10 2016-09-21 平顶山天安煤业股份有限公司 The method of secondary release preventing and treating bump
RU2709848C1 (en) * 2019-04-24 2019-12-23 Федеральное Государственное Бюджетное Учреждение Науки Институт Проблем Комплексного Освоения Недр Им. Академика Н.В. Мельникова Российской Академии Наук (Ипкон Ран) Method for blasting of ores and rocks
RU2740630C1 (en) * 2020-06-02 2021-01-18 Федеральное государственное бюджетное учреждение науки Институт земной коры Сибирского отделения Российской академии наук (ИЗК СО РАН) Method for reduction of excessive elastic energy in deep seismic dangerous segments of fractures

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