SU1712607A1 - Method for weakening difficult-to-cave roofs in mining gently sloping and inclined beds - Google Patents

Abstract

The invention relates to mining and m. used in the development of flat and inclined seams of coal and other minerals. The purpose of the invention is to reduce labor costs, increase the efficiency of the process of destruction of rocks and the safety of work on the management of rock pressure. The method consists in drilling wells into the roof of the reservoir from the haulage, ventilating wells and the split. chi, sealing and injection into the wells of workers well ”with tanks with reagents. In this case, as a reagent, reduced carbon dioxide in shells with a crushable membrane is used, which is placed in the wells before they are sealed. The membrane is tared at a pressure greater than the pressure of the working fluid in the well, but not less than the internal pressure in the shell of gaseous carbon dioxide at the temperature of the surrounding rocks. The softening of the hard-to-collapse roof is carried out due to the energy of the phase transition of the liquid to the solid state. At destruction of the envelope with liquefied carbon dioxide at the temperature of the host rocks, the working fluid is converted into a solid state and its rapid expansion with an overpressure of up to t13 MPa. which is many times greater than the compressive strength of the strongest sand and limestone. 4 ill. (The invention relates to mining and can be used in the development of flat and inclined bedding of coal and other minerals. Staring [of the walls is a way to weaken a hard-to-damage roof, including drilling a well, loading it with explosives, followed by torpedoing the roof for the purpose of its artificial collapse. The disadvantage of the known method of artificial landing of the roof is the possibility of flame escaping from the wells along the natural cracks of the roof into the developed space of methane gassed with methane, which is and leads to an explosion of methane-air mixture and coal dust. There is a known method of weakening a hard-to-damage roof by drilling wells and introducing liquid reagents into them, chemically interacting with the cementing material of the hard-to-get roof. hO o XI > &

Description

The disadvantage of this method is that the duration of the chemical reaction with the cementing substance of the roof rocks is long - at least one day. In addition, the use of such liquid chemicals (acids, alkalis) does not meet sanitary requirements for underground mining of minerals.

The purpose of the invention is to reduce labor costs, increase the efficiency of the process of rock destruction and the safety of work on the management of rock pressure.

The goal is achieved by the fact that in the method of softening a hard-to-collapse roof when developing flat and inclined seams, including drilling wells into the roof of a reservoir from a haulage, ventilation drift and splitting production, sealing and injecting working fluids with reagents into the wells, use liquefied carbon dioxide as a reagent in membranes with destructible membrane, which are placed in the wells before they are sealed. the membrane is calibrated to a pressure exceeding the pressure of the working fluid in the well, but not less than the internal pressure in the shell of carbon dioxide gas at the temperature of the surrounding rocks, while the softening of the hard-to-damage roof is softened by the influence of liquefied carbon dioxide on the working fluid and the energy of the phase transition of the fluid into the solid condition.

The proposed method differs from the known fundamentally new means of achieving the goal, i.e. softening of the hard-to-crush roof, which is based on the physical processes of converting liquefied carbon dioxide into gaseous state and water into ice, accompanied by a temperature drop to (-50-56) ° C. In this case, there is a rapid expansion of the formed ice, which at minus can create an overpressure of 113 MPa (ISO kgf / cm), many times exceeding the compressive strength of the strongest sandstones and limestones.

When the ice temperature decreases from (-10) to (-20) ° C, its overpressure instantly increases to 197 MPa (1970 kgf / cm), which guarantees rapid de-softening of the hard-to-crush roof, even consisting of strong sandstones or limes, having a strength factor f 10 on the scale of Prof. M.M.

Liquefied carbon dioxide shells placed in drilled wells before fluid is pumped into them through

sealing device (shutter), designed for excessive pressure, 2.5-Zg times the pressure of the injected fluid. In this case, the membrane in the throat of the shell, which, when it is triggered, accelerates the release of liquefied carbon dioxide from the shell into the well, which is pre-filled with water under a pressure of 0.3-0.5 MPa, and is activated under the condition PI P2 Pz (see Fig.4). where Рз 0.3-0.5 MPa pressure of fluid (water) in the well | 1х when the membrane is activated; Pa - pressure for which the membrane is designed; Pi is the pressure of liquefied carbon dioxide in the shells at the corresponding temperature of the host rocks.

Fig: 1 shows a well, a view in plan; in fig. 2 is a longitudinal section of one of a series of wells; in fig. 3 - overlapping contours influence wells; in fig. 4 is a scheme for implementing the method.

On these fmg. 1 through 4 denote ventilation 1 and drift 2 drifts, conducted with undermining of the roof at the border of the excavation section from slope 3 and its stroke 4 (figure 1). The boundary of the excavation area between the drifts 1 and 2 passes a slit 5 for intensive reworking of the lava.

For the primary and subsequent landing (Fig. 2) of the hard-to-damage roof 6 with the power of hl located above the Shu coal seam. in the roof of section 5 and drifts 1 and 2, the inclined wells 7 are drilled at a distance from each other equal to not more than 2R (FIG. 3), where R is the effective penetration radius of the fluid injected under pressure of RE (natural fractures of the rocks of the hard-to-get roof) The total natural (natural) cracks1 || constitute a Sho 8-11% of the effective volume of the rock cylinder, equal to 2 K gpn (Fig-4).

The fast softening effect develops ice expanding at a temperature of up to (-10) 0, creating an overpressure of 113 MPa (113-10 N / m}, many times exceeding the tensile strength of the strongest sandstones and limestones.

FIG. 4 depicts one of a series of boreholes 7n drilled before the beginning of the reverse mining of lava, the distance between which should not exceed 2R in order to artificially create a U-shaped contour of weakening through the drifts 1.2 and section 5 (Fig. 1-2) hard-to-crush roof with gpn capacity for primary and subsequent landings, excluding dangerous hanging of roof rocks.

The method of softening a hard-to-damage roof is carried out as follows. Before water is pumped into wells 7, one or several shells 8 (Fig. 4) with liquefied carbon dioxide (C02), which is at 0-5 ° C under pressure PI, are sent through. The shells 8 in the neck have a membrane 9 capable of withstanding a pressure of less than Pa liquefied COA and operate with an excess pressure of C02 more than P2.

After pumping into the wells 7 shells 8 prior to the injection of water, the wells 7 are closed with valves 10, having a check valve 11, a pressure fitting 12 with a sealing washer 13 and a discharge hose 14 connected to a pressure pump (not shown). After the series of drilled wells have been sealed, and the working face moved away from section 5 (Fig. 1) by 5-10 m, the arch support (conditionally not shown) is removed from the lines 5 on the haulage 2 and the ventilation 1 drift. to line 5 (figure 1). After this, in the well 7 (Fig. 1), a simultaneous injection is performed, water is supplied by means of a pressure pump (conventionally not shown). The action of excess pressure of water from the wellbore 7 within the radius R penetrates into natural cracks 7 (4g 4), the total volume of which is 8-11% of the volume 2jrR shn N, where N is the number of wells simultaneously participating in the softening of the roof that is difficult to break. Shells with liquefied CO2 are permanently stored in a special portable container with a minus temperature (..

From the moment of sending the shells into the wells, the temperature of the shell rises to the temperature of lateral rocks +20 -25С. In this case, the overpressure in the envelopes increases, which leads to rupture of the membrane and release of CO2 into the wells.

Liquefied C02, the exit from the shells 7 during adiabatic expansion, quickly turns liquefied into a gaseous state, absorbing heat from the water filling the well 7 and natural fractures 7 within radius R (Fig. 4). Due to the adiabatic expansion of C02, there is a sharp decrease in the temperature of the water in the wells and natural cracks in radius I (Fig. 2). At this, the temperature rapidly decreases to minus 10 ° С of the formed ice with its expansion, capable even at minus 10 ° С to create an overpressure of 113 MPa, many times exceeding the tensile strength of the strongest sandstones and limestones.

The amount of liquefied carbon dioxide required is determined by the formula

. (TI to) + A + C (T2 -TO)

1PS02 Q: o2 (Ta - tg) + Lco2 + cfco2 (T2 - tz)

where mt is the mass of water; Ci is the specific heat of water; TI is the initial water temperature; L-specific heat of ice melting; That is the ice formation temperature; Ta- Ice temperature; Cco2 is the specific heat of the liquid phase of carbon dioxide;

Tz is the transition temperature from the liquid phase of COa to the gaseous one;

tco2 heat of the COA transition from the liquid phase a. gaseous;

Cso2 specific heat raia

COA;

mcoa mass of carbon dioxide in the liquid phase.

The amount of liquefied carbon dioxide is determined depending on the amount of aode injected into the well.

As the lava recedes in the direction from 5 to 5 (Fig. 1), these operations repeat

With the removal of the arch support on the plugs 1 and

2, which ensures a uniform (after 2030 m) collapse to {yuvli after intensive lava mining in reverse, eliminating the dangerous consequences associated with the hang of hard-to-break rocks

roofing

The invention provides the following benefits; the absence of complex and expensive machines and mechanisms; safety of technical equipment used, except

TOGO, the proposed method eliminates the forced delay in the descent of workers into the mine, associated with the torpedoing of the hard-to-collapse roof or its chemical softening.

The expected economic effect is achieved by eliminating regressive lawsuits related to gas and coal dust explosions that have taken place and the death of miners as a result of flame penetration.

on natural cracks in the lava space developed by carbonated with methane during torpedoing of a roof that is hard to break: a 10% increase in daily production of complex-mechanized lava

(the average daily plan is 700 tons) as a result of the lava downtime during the implementation of the proposed method. This will ensure a monthly increase in coal output of 70 x 25 days "1,750 tons. With an average cost of coal of 25 rubles for 1 T, the annual economic effect of one

mine from the introduction of the proposed method will be 26 x 1750 x 12 months - 546 thousand rubles. Of the 600 coal mines in the USSR, with hard-to-damage roofs, 75 work. With the implementation of the proposed method, in 75 USSR mines, the total annual economic affect will be within 546 x 75-40.95 Million rubles. with a general increase in the level of safety of work on the management of a hard-to-damage roof.

Claims (1)

Claims The method of softening a hard-to-collapse roof when developing flat and inclined seams, includes drilling wells into the roof of the formation from haulage, ventilation drifts and development, sealing and injecting e wells of working fluids with reagents, characterized in that, in order to reduce labor costs , increase the efficiency of the process of destruction of rocks and the safety of work on the management of rock pressure. as a reagent, liquefied carbon dioxide in membranes with a crushable membrane is used, which are placed in the wells before they are sealed, taring the membrane at a pressure exceeding the pressure of the working fluid in the well, but not less than the internal pressure in the shell of gaseous carbon dioxide at the temperature of the surrounding rocks, The softening of the hard-to-collapse roofs of the oles ||| is caused by the influence of the liquefied carbon dioxide on the working fluid and the energy of the phase transition of the liquid to the solid state. 17  -iiiiNiia " T 3 V 5