RU2078216C1 - Method for prevention of rock bursts and increase of roof cavability - Google Patents

Abstract

FIELD: mining; increasing safety of underground mining in instantaneous outburst mines with roofs difficult-to-cave. SUBSTANCE: method of prevention of rock bursts includes outlining the rock blocks with slots over closed contour. The method of prevention of rock bursts is distinguished by the fact rock blocks are established by successive slotting with slot depth equalling one half of the normal distance between stopping horizons and slot width of not in excess of block height. EFFECT: higher efficiency. 2 dwg

Description

 The invention relates to improving the safety of underground mining in mines hazardous for mountain impacts and with hard-to-collapse roofs.

The closest analogue is a method of controlling the deformation of an undermined massif of rocks in order to eliminate deformations of the earth's surface (a.s. N 372351 with a priority of 02.16.1971, author Yu.I. Martynov. Bull. N 13, publ. 01.03.1973). The disadvantage of the analogue is, according to the claims, a large depth of the cracks, and therefore, high complexity. The depth of the cracks does not depend on the deformation of the earth's surface. A known method of controlling the roof (ed. St. USSR N 1453025 priority from 12.15.86, authors: Chakvetadze F.A. Chakvetadze R.A. Erokhin V.L., Pristash V.V.). Its essence is as follows. Wells are drilled from the pumping and ventilation drifts at an angle, which explode and pump liquid (urea), but preferably water. As a result, there is an intensive swelling of the enclosing rocks from 5 to 30%. This should ensure, according to the authors, the convergence of soil and roof. The named copyright certificate may serve as the closest prototype of the alleged invention. The disadvantages are as follows:
1. It can be used only in the host rocks, which can significantly swell (clays, siltstones, mudstones), otherwise there will be no effect.

 2. On powerful strata, this does not have an effect, but rocks cannot give an increase in power by several meters to ensure the convergence of soil and roof.

 3. Eliminates its use when working in the fall, as the water will move behind the face and cause flooding of the treatment works.

 4. Since 60-70% of the coal deposits are waterlogged and the process of rock heaving has passed, additional wetting does not give the necessary effect.

 5. This method of controlling the roof takes time to “soak” the enclosing rocks, which is not always possible when processing systems with collapse and a continuous mining process.

 The range of use of this method is very narrow. We propose another method, free from the above disadvantages and more effective.

 The aim of the invention is to increase the safety of underground mining in mines, dangerous for mountain impacts and hard-to-collapse roofs. This goal is achieved by the fact that in advance of the cleaning operations on the upper horizon, in order to reduce the risk of mountain impacts and increase the collapse of the roof, a sequence of monolithic blocks, contoured by gaps, is created under which an enhanced concentrated induced energy field is created, equal to the destruction energy in the contoured rock block and realized in additional crack formation under blocks with parameters: height h equal to at least half the normal distance between the cleansing bubbled horizons and width l, equal to or less than the block height.

 Identified distinguishing features were not found in the known solutions, therefore, the proposed solution meets the criterion of "significant differences".

 The invention is implemented as follows. Blocks of rocks are cut so that the slots of one serve as slots of the other, as shown in FIG. 1. The technology for constructing cracks with the blasting method is widely known and described in detail (Yu.I. Martynov, "Management of the deformation of the undermined massif of rocks with deep gaps." M. Nedra, 1995, p. 116, ill.). The construction of slots by drilling wells without casing and core is carried out from the upper horizon to the lower (Fig. 2). For this, ventilation and haulage drifts, lava space or small-section faults specially carried out on coal are used. As a result of the creation of a monolithic block (at h≥l), the energy ΔE would be released when the crack propagated, if it were not accompanied by the costs of plastic deformations at the apex and breaking of bonds in the material, i.e.

ΔE = δA-δu,
where δA is the energy used to advance the crack;
δu released energy within the boundaries of the rock block.

(В.З. Партон, Е.М.Морозов. "Механика упругопластического разрушения", М. "Наука", 1985, с. 32). Равновесное состояние трещины наступает при δA = δu. В нашем случае силы, работающие на создание щелей, выступают как внешние силы относительно упругопластических деформаций высвобождаемой энергии, заключенной в объеме блока пород. Показано, что если тело находится в равновесии, то приращение работы внешних сил равно приращению работы деформации (С.Д. Демидов. "Теория упругости", М. "Высшая школа", 1979, с. 52).The energy spent on the construction of gaps can be easily determined directly (by energy consumption for drilling wells, flow rate of explosives and its operability), or according to Inglis's decision using the Griffiths theory, the change in energy in a plate of unit thickness is

(V.Z. Parton, E.M. Morozov. "Mechanics of Elastoplastic Destruction", M. "Science", 1985, p. 32). The equilibrium state of the crack occurs at δA = δu. In our case, the forces working to create gaps act as external forces relative to the elastoplastic deformations of the released energy contained in the volume of the rock block. It is shown that if the body is in equilibrium, then the increment of the work of external forces is equal to the increment of the work of deformation (SD Demidov. "Theory of elasticity", M. "Higher School", 1979, p. 52).

,
где
h глубина щелей,
σ- напряжение растяжения, создаваемое при растяжении,
dl- приращение трещин в блоке пород в пространстве,
E модуль линейной упругости.so

,
Where
h the depth of the cracks,
σ is the tensile stress created by stretching,
dl - increment of cracks in the block of rocks in space,
E is the modulus of linear elasticity.

 Since the block of rocks does not collapse and only weakly deforms (Pat. N 1656129 USSR, E21D5 / 00. Method for controlling the deformation of the underworked massif; Yu. I. Martynov (USSR), N 421010/03; Statement 18.08.87. Publ. 15.01.91 Bull. N 22), then the energy intended for the destruction of the rock block will go to the destruction of the rocks under the block, where according to the principle of superposition, an energy field enclosed within the boundaries S of the rock block is superimposed on the existing energy field (Fig. 2). Since the length of the cracks is equivalent to the energy of crack formation, the total length of the cracks (slots) that outline the block, in the planar problem, it is equal to 2h, should be equal to the total length of the cracks obtained as a result of an additional energy field induced by a monolithic, slightly deformable, block of rocks. We show this experimentally (see table).

 Thus, the larger the volume of rocks contoured by slits, the more energy goes under the block and the rock is crushed finer.

 Using this method of dealing with rock pressure is less labor intensive (2 times), and in terms of effectiveness it is equivalent to the method if the slits cut the entire thickness from the upper horizon to the treatment one.

Claims (1)

 A method of preventing rock bumps and increasing roof collapse, including contouring rock blocks with slots in a closed loop, characterized in that the rock blocks are constructed by successively cutting them with slots with a depth equal to half the normal distance between the treatment horizons and the width of not more than the height of the block.

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