Disclosure of Invention
The invention aims to provide a method for preventing and controlling hydraulic fracture and cutting off the roof for pressure relief of coal mine rock burst, which is applied to a rock burst mine to realize safe, efficient, convenient and low-consumption roof cutting and pressure relief.
In order to achieve the above purpose, the technical solution adopted by the invention is as follows:
a method for preventing and controlling hydraulic fracture and cutting top pressure relief of coal mine rock burst comprises the following steps:
step 1, determining the position and the top breaking thickness of a target top breaking rock stratum
Covering a rock stratum construction detection hole above a coal seam roof near a construction area, counting the layer position distribution and the thickness of a hard thick rock stratum in the detection hole, taking the hard thick rock stratum in the range of a fracture zone above the coal seam roof as a target top breaking rock stratum, and taking the thickness corresponding to the target top breaking rock stratum as the top breaking thickness;
step 2, determining hydraulic fracture and cut hole construction parameters
The aperture of the splitting hole is 70-110 mm;
the depth L of the fractured hole is determined by adopting the following formula:
L=KH/sinθ;
in the formula:
l is the depth of the cracked hole; k is a surplus coefficient and has a value range of 1.1 to 1.3; h is the maximum distance between the target broken top rock layer and the construction position of the fracture cut hole; theta is a fracture-cut hole angle, and the value range of theta is 60-80 degrees;
the crack hole spacing a is determined by the following formula:
in the formula:
a is the spacing between the split holes; q (t) is the expansion pressure over time during hydraulic fracturing; sigmacUniaxial compressive strength, MP, for a target fractured roof formationa;
Step 3, hydraulic fracturing construction arrangement
Performing fracture-cutting hole construction according to the hydraulic fracture-cutting hole construction parameters in the step 2, after the fracture-cutting hole construction is completed, sequentially connecting a plurality of expansion devices to form a chain structure, connecting the expansion device at the lowest end with a high-pressure water pump positioned outside a fracture-cutting hole through a supercharger, and pushing the plurality of expansion devices in the chain structure into the fracture-cutting hole and within the fracture thickness range of the target fracture-top rock stratum;
step 4, hydraulic fracture cutting of target top rock layer
Starting a high-pressure water pump, injecting high-pressure water into the spalling device in the fractured hole by the high-pressure water pump for construction, carrying out compression expansion on the spalling device, applying fracture pressure on the target fractured top rock layer, cutting off the target fractured top rock layer, and withdrawing the spalling device from the fractured hole after pressure reduction;
step 5, detecting the splitting effect
Constructing a plurality of detection holes around the fracture hole, connecting the fracture hole and plugging the fracture hole by a high-pressure water pump through a pipeline, injecting high-pressure water into the fracture hole by the high-pressure water pump, and judging the fracture effect by the water outlet condition of the detection holes.
Preferably, in step 1, the hard thick rock formation is a single-layer rock formation with a thickness of more than 10m and a uniaxial compressive strength of more than 60 MPa.
Preferably, in the step 2, inclined hydraulic fracture cutting hole groups and trend hydraulic fracture cutting hole groups are alternately arranged along the side roadway, the trend hydraulic fracture cutting hole groups are positioned between the two groups of inclined hydraulic fracture cutting hole groups, the spacing range of the inclined hydraulic fracture cutting hole groups is 15-20 m, and the spacing range of the trend hydraulic fracture cutting hole groups is 15-20 m;
each inclined hydraulic fracture hole group comprises 3 fracture holes and 2 guide holes, wherein the 3 fracture holes and the 2 guide holes are arranged along the inclination, the 3 fracture holes and the 2 guide holes are arranged in a fan shape along the production side towards the target broken top rock layer, the 3 fracture holes are sequentially far away from the production side, the fracture holes and the guide holes are alternately arranged, and the guide holes are positioned between the adjacent fracture holes;
every group trend water conservancy splits cuts hole group and includes 3 and splits the cut hole, and 3 are split the cut hole and arrange along the trend, and 3 are split the cut hole and incline to production group side and goaf side and arrange, and the hole interval that adjacent splits the cut hole is 0.3 to 0.5 m.
Preferably, in step 4, according to the direction gradually far away from the production side, high-pressure water is injected into the crack breaking device of each crack cutting hole from the bottom end to the top end of the crack cutting hole one by one.
Preferably, in step 3, the construction of the fracture-cut hole is not less than 200m beyond the advanced working face.
Preferably, a one-way stop valve and a pressure release valve are arranged between the adjacent expansion devices.
Preferably, in the step 4, the high-pressure water pump injects high-pressure water into the internal expanding and cracking device of the fracture-cut hole, so that the construction distance is not less than 150m beyond the advanced working face.
Preferably, in the step 4, the high-pressure water pump injects the dilatant into the fractured holeConstructing under high pressure water with pressure not greater than 70MPaAnd the high-pressure water injection time is not more than 10 min.
Preferably, the length of the expander is set to 1 to 1.5 m.
Preferably, the detection hole is connected with a flow meter through a pipeline and is plugged, and the flow meter records the water outlet flow speed and flow rate so as to judge the crack cutting effect.
The beneficial technical effects of the invention are as follows:
the method for preventing and controlling hydraulic fracture and cutting off the top to relieve pressure in coal mine rock burst is applied to a rock burst mine, the top breaking and pressure relieving are safe and efficient, the construction operation is convenient, a bursting device and the like can be used repeatedly, and the cost is greatly reduced; the method has the advantages that the accurate pre-splitting of the broken top rock layer required by the top plate target is realized, the broken top rock layer is fully communicated under the action of overlying strata movement mine pressure, the falling is reduced, the dynamic load damage effect is reduced, the safety defect and the construction defect of explosive blasting roof cutting are avoided, and the method has extremely high application and popularization values in the coal mine rock burst prevention and control engineering practice.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings in combination with the specific embodiments. Certain embodiments of the invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, various embodiments of the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements.
In the description of the present invention, it should be noted that the terms "inside", "outside", "upper", "lower", "front", "rear", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The method for preventing and controlling hydraulic fracture and cutting top pressure relief of coal mine rock burst in the embodiment is shown in fig. 1 to 4.
A method for preventing and controlling hydraulic fracture and cutting off top pressure relief of coal mine rock burst comprises the following steps:
step 1, determining the position and the top breaking thickness of a target top breaking rock stratum
After the working face is mined, the rock stratum of the goaf begins to fall, and a fall zone, a fracture zone and a bent subsidence zone are gradually formed above the coal seam.
And (3) covering a rock stratum construction detection hole above the coal seam roof near the construction area, counting the layer position distribution and the thickness of the hard thick rock stratum in the detection hole, taking the hard thick rock stratum within the range of the fracture zone above the coal seam roof as a target top breaking rock stratum, and taking the thickness corresponding to the target top breaking rock stratum as the top breaking thickness.
Wherein the hard thick rock stratum is a rock stratum with a single-layer thickness of more than 10m and a uniaxial compressive strength of more than 60 MPa.
Step 2, determining hydraulic fracture and cut hole construction parameters
The aperture of the splitting hole is 70-110 mm;
the depth L of the fractured hole is determined by adopting the following formula:
L=KH/sinθ;
in the formula:
l is the depth of the cracked hole; k is a surplus coefficient and has a value range of 1.1 to 1.3; h is the maximum distance between the target broken top rock layer and the construction position of the fracture cut hole; theta is a fracture-cut hole angle, and the value range of theta is 60-80 degrees;
the crack hole spacing a is determined by the following formula:
in the formula:
a is the spacing between the split holes; q (t) is the expansion pressure over time during hydraulic fracturing; sigmacUniaxial compressive strength, MP, for a target fractured roof formationa。
In addition, inclined hydraulic fracture cutting hole groups and trend hydraulic fracture cutting hole groups are alternately arranged along the hollow side roadway, the trend hydraulic fracture cutting hole groups are positioned between the two groups of inclined hydraulic fracture cutting hole groups, the spacing range of the inclined hydraulic fracture cutting hole groups is 15-20 m, and the spacing range of the trend hydraulic fracture cutting hole groups is 15-20 m;
each inclined hydraulic fracture hole group comprises 3 fracture holes (marked by a, b and c in figure 3) and 2 guide holes (marked by d and e in figure 3), wherein the 3 fracture holes and the 2 guide holes are arranged along the inclination, the 3 fracture holes and the 2 guide holes are arranged in a fan shape towards a target fractured top rock layer along a production wall, the 3 fracture holes are sequentially far away from the production wall, the fracture holes and the guide holes are alternately arranged, and the guide holes are positioned between the adjacent fracture holes;
each group of strike hydraulic fracture hole group comprises 3 fracture holes (marked with a, b and c in figure 4), the 3 fracture holes are arranged along the strike, the 3 fracture holes are obliquely arranged towards the production side and the goaf side, and the hole distance between every two adjacent fracture holes is 0.3-0.5 m.
And (4) arranging the inclined hydraulic fracture cutting hole groups, and when the target fractured top rock layer is subjected to hydraulic fracture cutting in the step 4, cutting off the target fractured top rock layer along the position of the inclined hydraulic fracture cutting hole group, wherein a bursting device is not arranged in the guide hole, the bursting device is arranged in the fracture cutting hole, the bursting device is expanded under pressure to generate cracks at the position of the target fractured top rock layer fractured fracture cutting hole, and the guide hole is used for communicating the cracks at the position of the adjacent fracture cutting hole.
The hydraulic fracture cut hole groups are arranged in this way, and when the hydraulic fracture target breaks the top rock layer in the step 4, the pressure of the top plate on the side of the coal pillar in the section can be effectively reduced.
Step 3, hydraulic fracturing construction arrangement
And (3) according to the hydraulic fracturing hole construction parameters in the step (2), adopting a drilling machine with a positioning and guiding function to perform fracturing hole construction to the position of the target fractured top rock layer, and ensuring that the deflection error of the fracturing hole is not more than 10%. And the distance from the crack cut hole construction to the advanced working face is not less than 200 m.
After the fracturing hole construction is completed, the multiple expanding and fracturing devices are sequentially connected to form a chain structure, the expanding and fracturing device at the lowest end is connected with a high-pressure water pump located outside the fracturing hole through a supercharger, and the multiple expanding and fracturing devices in the chain structure are pushed into the fracturing hole and are within the fracture thickness range of the target fracture roof rock stratum.
And a one-way stop valve and a pressure release valve are arranged between the adjacent expanding devices. And a one-way stop valve is arranged to prevent high-pressure water in the spalling device from being guided. And a pressure relief valve is arranged to avoid the bursting device from being broken due to overlarge instantaneous pressure of high-pressure water.
The length of the bursting device is set to be 1-1.5 m, and the surface of the bursting device is provided with a protective shell to avoid abrasion of the bursting device when the bursting device moves in a splitting hole.
Step 4, hydraulic fracture cutting of target top rock layer
Starting a high-pressure water pump, adjusting a booster to set high-pressure water pressure, injecting high-pressure water into a fracturing device in a fracturing hole by the high-pressure water pump for construction, carrying out compression expansion on the fracturing device, applying fracturing pressure on a target fractured top rock layer, cutting off the target fractured top rock layer, and withdrawing the fracturing device from the fracturing hole after pressure reduction;
wherein, the high-pressure water pump injects high-pressure water into the cracking device in the cracking hole to construct the distance not less than 150m beyond the advanced working face.
According to the direction gradually far away from the production side, high-pressure water is injected into the crack breaking device of each crack cutting hole one by one from the bottom end to the top end of each crack cutting hole.
Injecting high-pressure water into the crack expander in the crack cutting hole by a high-pressure water pump for construction, wherein the pressure of the high-pressure water is not more than 70MPaHigh pressure waterThe injection time is not more than 10 min.
By the construction of the target broken top rock layer through hydraulic fracturing, in combination with the inclined hydraulic fracturing hole group arranged in the step 2, the aim of shortening the periodic pressure step distance is achieved in the inclined direction of the working face, the fractured holes are arranged to incline to the production side of the working face, the rock stratum of the target broken top rock layer naturally collapses after being stressed by the directional damage generated by hydraulic fracturing, the lower rock stratum is drawn and extruded to move, the mine pressure display law is fully utilized, after a cover rock top plate enters a goaf, the rock stratum in the target broken top rock layer naturally collapses, the direct top rock stratum in a lower caving zone is broken along with the pressure, so that the whole self collapse is realized, the target broken top rock stratum and the rock stratum in the lower caving zone collapse together collapse, the goaf can be filled, a more compact structure is formed to seal the goaf, the influence range of the leading and the lateral stress of the working face is reduced, and the influence of the cover rock is reduced, and double functions of top cutting and pressure relief are realized. And (3) combining the trend hydraulic fracturing and cutting hole group arranged in the step (2), the pressure of the top plate on the side of the sectional coal pillar can be effectively reduced.
Step 5, detecting the splitting effect
Constructing a plurality of detection holes around the fracture-cut hole, connecting the fracture-cut hole and plugging the fracture-cut hole by a high-pressure water pump through a pipeline, injecting high-pressure water into the fracture-cut hole by the high-pressure water pump, judging the fracture-cut effect by the water outlet condition of the detection holes, and judging whether to increase or decrease subsequent fracture-cut holes according to the fracture-cut effect.
Specifically, the inspection hole is connected with a flow meter through a pipeline and is plugged, the flow meter records the water outlet flow speed and flow, and the flow speed and flow of water flowing out of the inspection hole are used for judging the splitting effect.
Up to this point, the present embodiment has been described in detail with reference to the accompanying drawings. From the above description, those skilled in the art should clearly understand that the method for preventing hydraulic fracture and cutting off top pressure relief of coal mine rock burst according to the present invention. The method for preventing and controlling hydraulic fracture and cutting off the top to relieve pressure in coal mine rock burst is applied to a rock burst mine, the top breaking and pressure relieving are safe and efficient, the construction operation is convenient, a bursting device and the like can be used repeatedly, and the cost is greatly reduced; the method has the advantages that the accurate pre-splitting of the broken top rock layer required by the top plate target is realized, the broken top rock layer is fully communicated under the action of overlying strata movement mine pressure, the falling is reduced, the dynamic load damage effect is reduced, the safety defect and the construction defect of explosive blasting roof cutting are avoided, and the method has extremely high application and popularization values in the coal mine rock burst prevention and control engineering practice.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.