CN112983419A - Working face coal pillar setting method - Google Patents
Working face coal pillar setting method Download PDFInfo
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- CN112983419A CN112983419A CN202110291643.6A CN202110291643A CN112983419A CN 112983419 A CN112983419 A CN 112983419A CN 202110291643 A CN202110291643 A CN 202110291643A CN 112983419 A CN112983419 A CN 112983419A
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- 239000003245 coal Substances 0.000 title claims abstract description 182
- 238000000034 method Methods 0.000 title claims abstract description 28
- 239000010410 layer Substances 0.000 claims abstract description 71
- 230000003014 reinforcing effect Effects 0.000 claims abstract description 32
- 239000002344 surface layer Substances 0.000 claims abstract description 6
- 229910000831 Steel Inorganic materials 0.000 claims description 94
- 239000010959 steel Substances 0.000 claims description 94
- 239000011435 rock Substances 0.000 claims description 21
- 238000005553 drilling Methods 0.000 claims description 13
- 238000005065 mining Methods 0.000 claims description 10
- 230000005641 tunneling Effects 0.000 description 10
- 230000003068 static effect Effects 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 238000004873 anchoring Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000005755 formation reaction Methods 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 230000002787 reinforcement Effects 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 238000004901 spalling Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
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- 230000004048 modification Effects 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C41/00—Methods of underground or surface mining; Layouts therefor
- E21C41/16—Methods of underground mining; Layouts therefor
- E21C41/18—Methods of underground mining; Layouts therefor for brown or hard coal
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Abstract
The application discloses a working face coal pillar setting method, which comprises the following steps: installing an anchor rod to reinforce the coal side surface layer of the coal pillar, and installing a reinforcing structure on the coal pillar; and when the transport lane of the upper working face and the return airway of the lower working face are tunneled simultaneously, a plurality of underground fracturing drill holes are drilled at intervals to the sub-key layer and underground fracturing operation is carried out, and a plurality of ground fracturing drill holes are drilled at intervals to the main key layer and ground fracturing operation is carried out. The invention can improve the stability of the coal pillar and ensure the safety of operators.
Description
Technical Field
The application relates to the technical field of coal mine support, in particular to a working face coal pillar setting method.
Background
At present, with the increase of mining height, equipment such as production, auxiliary transportation and the like tends to be large-sized and oversize, and the section of a stoping roadway is increased along with the increase of the mining height. In order to keep the roadway stable, the spacing coal pillars on the working face are generally reserved with larger width and supported by anchor rods, and anchor cables need to be additionally arranged on the roadway side close to the goaf to reinforce the support. However, after the coal pillars are pressed to be crisp, the stability of the coal pillars is poor, the anchoring force of the anchor cable is greatly reduced, the reinforcing effect is poor, and the roadway is seriously deformed, so that the anchor cable is often unlocked, and the personal safety of miners is endangered.
Therefore, the invention needs to invent a method for reserving coal pillars on a working face with extra-large mining height of a shallow coal seam, which can improve the stability of the coal pillars.
Disclosure of Invention
The utility model aims to overcome the defects of the prior art, and provides a working face coal pillar reserving method, which can improve the stability of the coal pillar and ensure the safety of operators.
The technical scheme of the application provides a working face coal pillar setting method, which comprises the following steps:
installing an anchor rod to reinforce the coal side surface layer of the coal pillar, and installing a reinforcing structure on the coal pillar;
and when the transport lane of the upper working face and the return airway of the lower working face are tunneled simultaneously, a plurality of underground fracturing drill holes are drilled at intervals to the sub-key layer and underground fracturing operation is carried out, and a plurality of ground fracturing drill holes are drilled at intervals to the main key layer and ground fracturing operation is carried out.
Preferably, a hole is drilled into the coal seam from the ground vertically downwards, cores are taken from each rock stratum, and the mechanical properties are tested to judge the positions of the sub-key layers and the main key layer.
Preferably, selecting a rock stratum with the ratio of the distance from the coal seam to the thickness of the coal seam within the range of 4-6 as a sub-key layer according to the mining height of a working face.
Preferably, the reinforcing structure comprises a constant-resistance large-deformation counter-pulling anchor cable and a limiting steel belt, the anchor cable is drilled on the coal pillar, the constant-resistance large-deformation counter-pulling anchor cable is installed in a drilled hole, and the limiting steel belt is tightly attached to the surface of the coal pillar and is compressed by the constant-resistance large-deformation counter-pulling anchor cable.
Preferably, the constant-resistance large-deformation counter-pulling anchor cable comprises a steel strand, a first lock, a first constant resistor, a first supporting plate, a second constant resistor and a second lock, wherein the steel strand sequentially runs through the first lock, the first constant resistor, the first supporting plate, the limiting steel belt, the coal pillar, the second supporting plate, the second constant resistor and the second lock, and the steel strand is right to the first lock and the second lock, and pretightening force is applied to the first constant resistor, the first supporting plate, the limiting steel belt, the second supporting plate and the second constant resistor are tightly pressed on the coal pillar.
Preferably, the limiting steel belt comprises a first W-shaped steel belt and a second W-shaped steel belt which are arranged in a staggered mode, and the limiting steel belt further comprises a reinforcing net which covers the surface of the coal pillar.
Preferably, the pre-tightening force f to be applied by each steel strand under the condition that the cross-sectional area of the coal pillar is unchanged before and after deformation is given by the following formula:
in the formula: f is the pre-tightening force (N) applied by each steel strand; h is the height (m) of the coal pillar; e is the elastic modulus (MPa) of the coal pillar; f is the load (N) borne by the coal pillar after fracturing; n is the number of each row of steel strands on the coal side; l is the coal pillar width (m); k is a safety coefficient and is 1.1-1.3.
Preferably, the angle between the downhole fracture borehole and the horizontal is 78-82 °. And the included angle between the ground fracturing drill hole and the horizontal direction is 82-86 degrees.
Preferably, the surface fracturing bore hole and the downhole fracturing bore hole are arranged above one side of the coal pillar adjacent to the coal seam to be mined;
and carrying out fracturing operation on the ground fracturing drill hole and the underground fracturing drill hole while mining the coal seam and forming a goaf.
Preferably, the downhole fracture boreholes are staggered from the surface fracture boreholes.
After adopting above-mentioned technical scheme, have following beneficial effect: according to the invention, the coal pillar is reinforced by installing the reinforcing structure on the coal pillar, and the fracturing operation is carried out on the sub-key layer in the tunneling process, so that the fractured sub-key layer is collapsed along with the propulsion of a working face, and the dynamic load damage of the coal pillar caused by the tunneling rotary motion of the sub-key layer is reduced; and the fracturing operation is carried out on the main key layer, so that most of load can be effectively transferred to a goaf, and the static load required to be borne by the coal pillar is reduced, thereby effectively ensuring the stability of the coal pillar and ensuring the safety of operators.
Drawings
The disclosure of the present application will become more readily understood by reference to the drawings. It should be understood that: these drawings are for illustrative purposes only and are not intended to limit the scope of the present application. In the figure:
FIG. 1 is a flow diagram of a method of the present invention in one embodiment;
FIG. 2 is a schematic illustration of the position of the upper and lower working surfaces in one embodiment of the invention;
FIG. 3 is a cross-sectional view taken at A-A of FIG. 2;
FIG. 4 is a schematic view of a constant resistance large deformation split anchor cable installed on a coal pillar according to one embodiment of the present invention;
FIG. 5 is a right side view of FIG. 4;
fig. 6 is a schematic illustration of the invention after face voiding in one embodiment.
Reference symbol comparison table:
the device comprises an upper working face 1, a lower working face 2, a transportation lane 3, an air return lane 4, a coal pillar 5, a goaf 6, a main key layer 7, a sub-key layer 8, a ground fracturing drill hole 9, an underground fracturing drill hole 10, a coal seam 11, a first lock 121, a second lock 122, a first constant resistor 131, a second constant resistor 132, a first supporting plate 141, a second supporting plate 142, a first W-shaped steel belt 15, a second W-shaped steel belt 16, a steel strand 17, an anchor rod 18, a bolt 19, a tray 20, a reinforcing net 21, the ground 22, an anchor cable drilling hole 23, an anchor rod drilling hole 24 and a resin anchoring agent 25.
Detailed Description
Embodiments of the present application are further described below with reference to the accompanying drawings.
It is easily understood that according to the technical solutions of the present application, those skilled in the art can substitute various structures and implementations without changing the spirit of the present application. Therefore, the following detailed description and the accompanying drawings are merely illustrative of the technical solutions of the present application, and should not be construed as limiting or restricting the technical solutions of the present application in their entirety.
The terms of orientation of up, down, left, right, front, back, top, bottom, and the like referred to or may be referred to in this specification are defined relative to the configuration shown in the drawings, and are relative terms, and thus may be changed correspondingly according to the position and the use state of the device. Therefore, these and other directional terms should not be construed as limiting terms. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
Throughout the description of the present application, it is to be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "coupled" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; the two components can be directly connected or indirectly connected through an intermediate medium, and the two components can be communicated with each other. The foregoing is to be understood as belonging to the specific meanings in the present application as appropriate to the person of ordinary skill in the art.
In one embodiment of the invention, a working face coal pillar setting method is disclosed, which comprises the following steps:
installing an anchor rod 18 to reinforce the surface layer of the coal side of the coal pillar 5, and installing a reinforcing structure on the coal pillar 5;
when the transportation lane 3 of the upper working face 1 and the return airway 4 of the lower working face 2 are tunneled simultaneously, a plurality of underground fracturing drill holes 10 are drilled at intervals to the sub-key layer 8 and underground fracturing operation is carried out, and a plurality of ground fracturing drill holes 9 are drilled at intervals to the main key layer 7 and ground fracturing operation is carried out.
The main key layer 7 is located above the sub-key layer 8, the sub-key layer is located above the coal pillar 6, the anchor rod 18 mounted on the surface of the coal side of the coal pillar 5 can be used for limiting deformation of the coal pillar 5 in the initial tunneling stage, and a reinforcing structure is mounted on the coal pillar 5, so that the stability of the coal pillar 5 is improved, the main key layer 7 and the sub-key layer 8 are subjected to fracturing operation while tunneling, fracturing of the sub-key layer 8 is beneficial to damage of a suspended roof structure above the coal pillar 5 on the goaf 6 side, the fractured sub-key layer 8 falls along with the pushing of a working face, the dynamic load damage of the coal pillar 5 caused by the rotary motion of the sub-key layer 8 in the tunneling process can be reduced, and the stability of the coal pillar 5 is improved; in addition, because the primary key zone 7 controls the movement of all the rock formations above it to the surface 22, fracturing the primary key zone 7 helps to transfer a significant portion of the load efficiently to the gob 6, reducing the static load that the pillar 5 needs to bear. According to the method, the strength of the coal pillar 5 is improved by installing the reinforcing structure on the coal pillar 5, and the load of the coal pillar 5 is reduced by fracturing the main key layer 7 and the sub-key layer 8 during tunneling, so that the stability of the coal pillar 5 can be improved, and the operation safety can be improved.
In some embodiments of the invention, a borehole is drilled vertically down into coal seam 11 from surface 22, and cores are taken from the formations and mechanical properties are tested to determine the location of sub-critical zone 8 and main critical zone 7. Specifically, the positions of the main key layer 7 and the sub-key layer 8 are determined by drilling coring and according to the indexes of the thickness, volume weight, elastic modulus, tensile strength, and the like of each rock layer.
In some embodiments of the invention, rock strata with a ratio of distance from the coal seam 11 to thickness of the coal seam 11 in the range of 4-6 is selected as the sub-critical layer 8 according to the mining height of the working face.
In some embodiments of the present invention, the reinforcing structure comprises a constant-resistance large-deformation split anchor cable and a limiting steel belt, the constant-resistance large-deformation split anchor cable is installed in the anchor cable drilling hole 23 drilled on the coal pillar 5, and the limiting steel belt is tightly attached to the surface of the coal pillar 5 and is tightly pressed by the constant-resistance large-deformation split anchor cable. When the surrounding rock is damaged by slow or instantaneous large deformation, the constant-resistance large-deformation opposite-pulling anchor cable can absorb the deformation energy of the rock body, so that the energy in the surrounding rock is released. In the structural deformation stage of the constant-resistance large-deformation opposite-pulling anchor cable, constant working resistance and stable deformation can still be kept, so that the stability of surrounding rocks of the roadway is realized, and potential safety hazards such as roof fall, collapse, rib spalling and floor heave are greatly reduced. In addition, the integral reinforcing performance of the constant-resistance large-deformation split anchor cable can be improved through the limiting steel belt.
In some embodiments of the present invention, the constant-resistance large-deformation split anchor cable includes a steel strand 17, a first lock 121, a first constant resistor 131, a first support plate 141, a second support plate 142, a second constant resistor 132, and a second lock 122, the steel strand 17 sequentially penetrates through the first lock 121, the first constant resistor 131, the first support plate 141, a limiting steel belt, the coal pillar 5, the second support plate 142, the second constant resistor 132, and the second lock 122, and the steel strand 17 applies a pre-tightening force to the first lock 121 and the second lock 122 to press the first constant resistor 131, the first support plate 141, the limiting steel belt, the second support plate 142, and the second constant resistor 132 against the coal pillar 5. The first lock 121 and the second lock 122 are disposed at two ends of the steel strand 17 and used for limiting the positions of the first constant resistor 131, the first supporting plate 141, the second supporting plate 142 and the second constant resistor 132, when the coal pillar 5 deforms, the coal pillar 5 pushes the first constant resistor 131 and the second constant resistor 132, and the first constant resistor 131 and the second constant resistor 132 slide along the steel strand 17, so that the deformation energy of the coal pillar 5 during deformation is absorbed, the steel strand 17 is prevented from being broken and failing due to the deformation of the coal pillar 5, and the stability of the coal pillar 5 is maintained.
In some embodiments of the present invention, the limiting steel belts include a first W-shaped steel belt 15 and a second W-shaped steel belt 16, the first W-shaped steel belt 15 and the second W-shaped steel belt 16 are arranged in a staggered manner, and a reinforcing mesh 21, and the reinforcing mesh 21 covers the coal slope surface of the coal pillar 5. A plurality of first W type steel strips 15 are parallel and the interval sets up, and a plurality of second W type steel strips 16 set up the below at first W type steel strip 15, and a plurality of second W type steel strips 16 are parallel and the interval sets up, and the mode of first W type steel strip 15 and 16 staggered arrangement of second W type steel strip can increase the area of contact with coal column 5, and can exert the whole reinforcement performance of constant resistance large deformation to drawing the anchor rope fully. In addition, the reinforcing net 21 is arranged below the second W-shaped steel belt 16 and is pressed on the surface of the coal pillar 5 by the second W-shaped steel belt 16, and the reinforcing performance of the constant-resistance large-deformation split anchor cable can be improved.
In some embodiments of the present invention, the pre-tightening force f to be applied to each steel strand 17 under the assumption that the cross-sectional area remains unchanged before and after the coal pillar 5 is deformed can be given by:
in the formula: f is the pre-tightening force (N) applied by each steel strand 17; h is the height (m) of the coal pillar 5; e is the modulus of elasticity (MPa) of the coal pillar 5; f is the load (N) borne by the coal pillar 5 after fracturing; n is the number of the steel strands 17 in each row on the coal side; l is the width (m) of the coal pillar 5; k is a safety coefficient and is 1.1-1.3.
In some embodiments of the invention, the angle between the downhole fractured borehole 10 and horizontal is between 78 ° and 82 °. After drilling of the underground fracturing drill hole 10 is completed, high-pressure water is injected into the underground fracturing drill hole 10 to perform fracturing operation, so that the sub-key layer 8 is fractured and can collapse along with the advance of a working face, and dynamic load damage of the coal pillar 5 is reduced.
In some embodiments of the invention the angle between the surface fracture borehole 9 and the horizontal is 82-86 °. After the ground fracturing drill hole 9 is drilled, high-pressure water is injected into the ground fracturing drill hole 9 for fracturing operation, so that the main key layer 7 is fractured, the load is effectively transferred to the goaf 6, and the static load born by the coal pillar 5 is reduced.
In some embodiments of the present invention, a surface fracturing borehole 9 and a downhole fracturing borehole 10 are disposed above the side of the coal pillar 5 adjacent the coal seam 11 to be mined, and the surface fracturing borehole 9 and the downhole fracturing borehole 10 are subjected to a fracturing operation while the coal seam 11 is mined and the gob 6 is formed. After the coal seam 11 is mined, when fracturing operation is carried out, a suspended roof structure formed above the goaf 6 can be damaged to the maximum extent, the load of the coal pillar 5 is reduced, and therefore a good pressure relief effect is achieved.
In some embodiments of the invention, the downhole fracture boreholes 10 are staggered with respect to the surface fracture boreholes 9. This can facilitate efficient transfer of the formation load carried by the primary key zone 7 to the gob 6.
Example 1:
the embodiment discloses a working face coal pillar setting method, as shown in fig. 1 and 2, which comprises the following steps:
s101: installing an anchor rod 18 to reinforce the surface layer of the coal side of the coal pillar 5, and installing a reinforcing structure on the coal pillar 5;
s102: when the transportation lane 3 of the upper working face 1 and the return airway 4 of the lower working face 2 are tunneled simultaneously, a plurality of underground fracturing drill holes 10 are drilled at intervals to the sub-key layer 8 and underground fracturing operation is carried out, and a plurality of ground fracturing drill holes 9 are drilled at intervals to the main key layer 7 and ground fracturing operation is carried out.
The main key layer 7 is located above the sub-key layer 8, the sub-key layer is located above the coal pillar 6, the main key layer 7 serves as a ground fracturing target layer, the sub-key layer 8 serves as an underground fracturing target layer, as shown in fig. 3, a hole is drilled vertically downwards from the ground 22 to the coal seam 11, cores are taken for each rock stratum and mechanical properties of each rock stratum are tested, the positions of the main key layer 7 and the sub-key layer 8 which are located on the coal seam 11 are judged according to indexes such as thickness, volume weight, elastic modulus and tensile strength of each rock stratum, and rock strata, with the ratio of the distance from the coal seam 11 to the thickness of the coal seam 11 being within the range of 4-6, are selected as the sub-key layer 8 according to the mining height of a working face. The fracturing of the sub-key layer 8 can help to destroy a suspended roof structure above the coal pillar 5 on the side of the goaf 6, the fractured sub-key layer 8 collapses along with the propulsion of the working face, and the dynamic load damage of the coal pillar 5 caused by the rotary motion of the sub-key layer 8 in the propulsion process of the working face is reduced. The primary key layer 7 controls the movement of all rock layers above the primary key layer 7 to the surface 22, and fracturing the primary key layer 7 helps to effectively transfer most of the load to the gob 6, reducing the static load that the pillar 5 needs to bear.
In step S101, as shown in fig. 4 and 5, the reinforcing mesh 21 is first covered on the coal side surface of the coal pillar 5, the anchor rod drilling hole 24 is drilled on the coal side surface of the coal pillar 5, the resin anchoring agent 25 is filled in the anchor rod drilling hole 24, the anchor rod 18 is filled in the anchor rod drilling hole 24, the tray 20 is filled in the end portion of the anchor rod 18, and finally the anchor rod 18 is fixed by the mounting bolt 19, so that the coal pillar 5 side surface layer can be reinforced by mounting the anchor rod 18 to limit the initial deformation of the coal pillar 5.
After the anchor rod 18 is installed and preliminary reinforcement is performed, a reinforcing structure is installed, specifically, the reinforcing structure comprises a constant-resistance large-deformation split anchor cable, a second W-shaped steel belt 16 and a first W-shaped steel belt 15, and the constant-resistance large-deformation split anchor cable comprises a steel strand 17, a first lock 121, a first constant resistor 131, a first supporting plate 141, a second supporting plate 142, a second constant resistor 132 and a second lock 122. Wherein, when the constant-resistance large-deformation counter-pulling anchor cable is installed, firstly, an anchor cable drilling hole 23 is drilled on the coal pillar 5, the anchor cable drilling hole 23 penetrates through the coal pillar 5 along the width direction of the coal pillar 5, then hanging a first W-shaped steel belt 15 and a second W-shaped steel belt 16 on the surface of the coal side of the coal pillar 5, sequentially passing a steel strand 17 through a first lock 121, a first constant resistor 131, a first supporting plate 141, the first W-shaped steel belt 15, the second W-shaped steel belt 16, a reinforcing net 21, the coal pillar 5, the reinforcing net 21, the second W-shaped steel belt 16, the first W-shaped steel belt 15, a second supporting plate 142, a second constant resistor 132 and a second lock 122, wherein the first lock 121 and the second lock 122 are arranged at two ends of the steel strand, the first supporting plate 141, the second supporting plate 142, the first W-shaped steel strip 15, the second W-shaped steel strip 16 and the reinforcing net 21 are fixed through the first lock 121 and the second lock 122, and pretightening force is applied to the steel strands, so that each part can be tightly pressed on the coal pillar 5.
As shown in fig. 4, under the condition that the cross-sectional area of the B-plane remains unchanged before and after the coal pillar 5 is deformed, the pre-tightening force f required to be applied by each steel strand 17 can be given by the following formula:
in the formula: f is the pre-tightening force (N) applied by each steel strand 17; h is the height (m) of the coal pillar 5; e is the modulus of elasticity (MPa) of the coal pillar 5; f is the load (N) borne by the coal pillar 5 after fracturing; n is the number of the steel strands 17 in each row on the coal side; l is the width (m) of the coal pillar 5; k is a safety coefficient and is 1.1-1.3.
In the present embodiment, as shown in fig. 5, the first W-shaped steel strips 15 and the second W-shaped steel strips 16 are arranged in a staggered manner, specifically, the plurality of first W-shaped steel strips 15 are arranged in parallel and at intervals, the plurality of second W-shaped steel strips 16 are arranged below the first W-shaped steel strips 15, the plurality of second W-shaped steel strips 16 are arranged in parallel and at intervals, and the first W-shaped steel strips 15 and the second W-shaped steel strips 16 are arranged in a staggered manner, so that the contact area with the coal pillar 5 can be increased, and the overall reinforcing performance of the anchor cable by constant-resistance large-deformation can be fully exerted. Specifically, the first W-shaped steel strip 15 and the second W-shaped steel strip 16 are perpendicular to each other, the anchor 18 is disposed in a region surrounded by the first W-shaped steel strip 15 and the second W-shaped steel strip 16, and the anchor 18 is not disposed to overlap with the first W-shaped steel strip 15 and the second W-shaped steel strip 16.
In addition, the reinforcing net 21 is arranged below the second W-shaped steel belt 16 and is pressed on the coal side surface of the coal pillar 5 by the second W-shaped steel belt 16, and the reinforcing performance of the constant-resistance large-deformation split anchor cable can be improved. When the surrounding rock is damaged by slow or instantaneous large deformation, the constant-resistance large-deformation opposite-pulling anchor cable can absorb the deformation energy of the rock body, so that the energy in the surrounding rock is released. In the structural deformation stage of the constant-resistance large-deformation opposite-pulling anchor cable, constant working resistance and stable deformation can still be kept, so that the stability of surrounding rocks of the roadway is realized, and potential safety hazards such as roof fall, collapse, rib spalling and floor heave are greatly reduced. When the coal pillar 5 deforms, the coal pillar 5 pushes the first constant resistor 131 and the second constant resistor 132, and the first constant resistor 131 and the second constant resistor 132 slide along the steel strand 17, so that the deformation energy of the coal pillar 5 deformation is absorbed, the steel strand 17 is prevented from being broken and losing efficacy due to the deformation of the coal pillar 5, and the stability of the coal pillar 5 is maintained.
In step S102, as shown in fig. 6, while the transportation lane 3 of the upper working face 1 and the return airway 4 of the lower working face 2 are driving, drilling the underground fractured borehole 10 into the sub-critical layer 8 at intervals of 30m in the transportation lane 3 of the upper working face 1, taking into consideration that the underground roadway operation space limit and the crack position of the sub-critical layer 8 should be located above the coal seam 11, taking an included angle between the underground fractured borehole 10 and the horizontal direction to be 78-82 °, and performing high-pressure water injection fracturing operation immediately after the borehole is formed. The method is characterized in that ground fracturing drill holes 9 are drilled from the ground 22 to the main key layer 7 every 30m in the direction parallel to the coal pillars 5, the ground fracturing drill holes 9 are located above the coal seam 11, an included angle between each drill hole and the horizontal direction is 82-86 degrees, high-pressure water injection fracturing operation is carried out immediately after the drill holes are formed, the terminals of the ground fracturing drill holes 9 and the terminals of the underground fracturing drill holes 10 are arranged in a staggered mode, and therefore rock stratum loads borne by the main key layer 7 are effectively transferred to the goaf 6.
In the present embodiment, the surface fracturing borehole 9 and the downhole fracturing borehole 10 are provided above the side of the coal pillar 5 adjacent to the coal seam 11 to be mined, and fracturing operations are performed on the surface fracturing borehole 9 and the downhole fracturing borehole 10 while mining the coal seam 11 and forming the gob 6. When fracturing operation is carried out, a suspended roof structure formed above the goaf 6 can be damaged to the maximum extent, and the load of the coal pillar 5 is reduced, so that a good pressure relief effect is achieved. As shown in fig. 3, Y indicates the direction from inside to outside, and the plurality of surface fracturing boreholes 9 and the plurality of downhole fracturing boreholes 10 are spaced in the Y direction to ensure that the suspended roof structure can be broken as much as possible.
The anchor rods 18 are arranged on the coal side surface of the coal pillar 5 and can be used for limiting deformation of the coal pillar 5 in the initial tunneling stage, and a reinforcing structure is arranged on the coal pillar 5, so that the stability of the coal pillar 5 is improved, the fracturing operation is carried out on the main key layer 7 and the sub-key layer 8 during tunneling, the fracturing of the sub-key layer 8 is beneficial to damaging a suspended roof structure above the coal pillar 5 on the goaf 6 side, the fractured sub-key layer 8 collapses along with the pushing of a working face, the dynamic load damage of the coal pillar 5 caused by the rotary motion of the sub-key layer 8 in the tunneling process can be reduced, and the stability of the coal pillar 5 is improved; since the primary key zone 7 controls the movement of all the strata above it to the surface 22, fracturing the primary key zone 7 helps to transfer a significant portion of the load efficiently to the gob 6, reducing the static load that the pillar 5 needs to bear. As shown in fig. 6, when the solid coal area on the right side of the coal pillar 5 is excavated to form the gob 6, since the sub-key layer 8 and the main key layer 7 collapse by performing the fracturing operation on the sub-key layer 8 and the main key layer 7, at least a part of the main key layer 7 collapses to the gob 6, thereby destroying the suspended roof structure above the coal pillar 5 on the side of the gob 6. According to the method, the strength of the coal pillar 5 is improved by installing the reinforcing structure on the coal pillar 5, and the load of the coal pillar 5 is reduced by fracturing the main key layer 7 and the sub-key layer 8 during tunneling, so that the stability of the coal pillar 5 can be improved, and the operation safety can be improved.
What has been described above is merely the principles and preferred embodiments of the present application. It should be noted that, for a person skilled in the art, several other modifications can be made on the basis of the principle of the present application, and these should also be considered as the scope of protection of the present application.
Claims (10)
1. A working face coal pillar setting method is characterized by comprising the following steps:
installing an anchor rod (18) to reinforce the coal slope surface layer of the coal pillar (5), and installing a reinforcing structure on the coal pillar (5);
when the transport lane (3) of the upper working face (1) and the return airway (4) of the lower working face (2) are tunneled simultaneously, a plurality of underground fracturing drill holes (10) are drilled at intervals to the sub-key layer (8) and underground fracturing operation is carried out, and a plurality of ground fracturing drill holes (9) are drilled at intervals to the main key layer (7) and ground fracturing operation is carried out.
2. A face coal pillar setting method as claimed in claim 1, characterized by drilling a hole from the ground (22) vertically downwards to the coal seam (11), coring each rock layer and testing the mechanical properties to determine the position of the sub-critical layer (8) and the main critical layer (7).
3. The working face coal pillar setting method as claimed in claim 1, characterized in that rock strata with the ratio of the distance from the coal seam (11) to the thickness of the coal seam (11) in the range of 4-6 are selected as the sub-critical strata (8) according to the mining height of the working face.
4. The working face coal pillar setting method as claimed in claim 1, characterized in that the reinforcing structure comprises constant-resistance large-deformation split anchor cables and limiting steel belts, the constant-resistance large-deformation split anchor cables are installed by drilling anchor cable drill holes (23) on the coal pillars (5), and the limiting steel belts are tightly attached to the surfaces of the coal pillars (5) and are compressed by the constant-resistance large-deformation split anchor cables.
5. The working face coal pillar setting method as claimed in claim 4, wherein the constant-resistance large-deformation split anchor cable comprises a steel strand (17), a first lock (121), a first constant resistor (131), a first supporting plate (141), a second supporting plate (142), a second constant resistor (132) and a second lock (122), the steel strand (17) penetrates through the first lock (121), the first constant resistor (131), the first supporting plate (141), the limiting steel belt, the coal pillar (5), the second supporting plate (142), the second constant resistor (132) and the second lock (122) in sequence, the steel strand (17) exerts pretightening force on the first lock (121) and the second lock (122) to press the first constant resistor (131), the first supporting plate (141), the limiting steel belt, the second supporting plate (142) and the second constant resistor (132) on the coal pillar (5).
6. The working face coal pillar setting method as claimed in claim 5, characterized in that the limiting steel belts comprise a first W-shaped steel belt (15) and a second W-shaped steel belt (16), the first W-shaped steel belt (15) and the second W-shaped steel belt (16) are arranged in a staggered mode, and the method further comprises a reinforcing net (21), and the reinforcing net (21) covers the surface of the coal pillar (5).
7. The working face coal pillar setting method as claimed in claim 5, wherein the pre-tightening force f to be applied by each steel strand (17) is given by the following formula under the assumption that the cross-sectional area of the coal pillar (5) remains unchanged before and after deformation:
in the formula: f is a pre-tightening force (N) applied by each steel strand (17); h is the height (m) of the coal pillar (5); e is the elastic modulus (MPa) of the coal pillar (5); f is the load (N) borne by the coal pillar (5) after fracturing; n is the number of each row of steel stranded wires (17) on the coal side; l is the width (m) of the coal pillar (5); k is a safety coefficient and is 1.1-1.3.
8. The working face coal pillar setting method as claimed in claim 1, characterized in that the included angle between the downhole fracturing bore (10) and the horizontal direction is 78-82 °, and the included angle between the surface fracturing bore (9) and the horizontal direction is 82-86 °.
9. A face coal pillar setting method as claimed in claim 1, characterized in that the surface fracturing bore (9) and the downhole fracturing bore (10) are arranged above the side of the coal pillar (5) adjacent to the coal seam (11) to be mined;
and performing fracturing operation on the ground fracturing drill hole (9) and the underground fracturing drill hole (10) while mining the coal seam (11) and forming a goaf (6).
10. A face coal string setting method as claimed in claim 1, characterized in that the downhole fracturing boreholes (10) are staggered with respect to the surface fracturing boreholes (9).
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114704267A (en) * | 2021-12-23 | 2022-07-05 | 中国矿业大学 | Cooperative anchoring structure for enhancing stability of gob-side entry driving coal pillar and construction method |
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