A method for controlling deformation and hydraulic fracturing of surrounding rock in the large tunnel under the working face

Abstract

The present invention discloses a method for controlling the deformation of surrounding rock of the main tunnel of the underlying mining area during mining of the working face by hydraulic fracturing. First, drilling holes are constructed in the return air level tunnel and the transport level tunnel of the mining working face to the basic top rock layer and hydraulic fracturing is performed to weaken the thick hard rock layer of the basic top, and the pressure step distance of the basic top fracture is reduced; then drilling holes are constructed in the main tunnel of the underlying mining area and the upper mountain of the mining area to the basic bottom rock layer, and hydraulic slit directional hydraulic fracturing is performed to form a weak structural surface in the basic bottom rock layer above the main tunnel of the mining area and the upper mountain of the mining area, blocking the stress propagation path of the mining dynamic pressure to the main tunnel of the underlying mining area and the upper mountain, and reducing the deformation of the main tunnel of the underlying mining area and the upper mountain. The present invention reduces the influence of the mining dynamic pressure on the main tunnel of the underlying mining area and the upper mountain by fracturing the basic top to weaken the mining dynamic pressure stress source and fracturing the basic bottom to block the stress transmission path, thereby controlling the deformation of the main tunnel of the underlying mining area and the upper mountain, and has the characteristics of simple and efficient, convenient construction and low cost.

Description

Technical Field

[0001] The invention relates to the technical field of mineral mining, and in particular to a method for controlling deformation hydraulic fracturing of surrounding rocks of a large tunnel in an underlying mining area during mining of a working face. Background Art

[0002] For cross-mining of the large tunnel working face in the underlying mining area under great burial depth conditions, during the mining process of the working face, the overlying rock strata rotate and deform, the basic roof undergoes periodic fracture, and the strain energy accumulated in the roof rock strata is suddenly released, causing the mining stress to be transmitted to the large tunnel in the mining area below the working face through the basic bottom rock stratum with high strength, high stiffness and good integrity, changing the surrounding rock stress environment of the large tunnel in the underlying mining area, and easily causing large deformation of the surrounding rock, fracture and failure of supporting components, etc., resulting in the difficulty of surrounding rock control in the large tunnel in the mining area.

[0003] Affected by the great burial depth and mining disturbance, the main tunnel of the mining area below the working face is in a high ground stress environment. In order to reduce the impact of the dynamic pressure of the working face on the mining area, the traditional measure is to increase the width of the protective coal pillar of the main tunnel of the mining area. However, it is impossible to effectively release the high stress. The stress is concentrated at the coal pillar, causing the originally broken coal pillar to undergo greater deformation and damage, and at the same time, the effective amount of coal resources mined by the working face is reduced. Passive support methods such as U-shaped steel have the disadvantages of high cost, difficult maintenance and harsh construction conditions. Active support forms such as anchor cables and bolts are used. Most of the anchors are in the strength deterioration zone, making it difficult to play a supporting role. The anchor cables are subjected to excessive force, close to the ultimate breaking force, and have low safety. Under the above-mentioned active support conditions, the scope of surrounding rock loosening and deterioration is further expanded, the large deformation of the tunnel surrounding rock becomes more serious, and the roof control becomes more difficult.

[0004] Traditional methods of controlling surrounding rock in deep tunnels can only achieve the end-point prevention and control of deformation of tunnel surrounding rock, but cannot solve the high stress problem of deformation in deep mining tunnels from the source, and the surrounding rock control effect is limited. Artificial weakening of the roof is an effective method for weakening and blocking mining stress in deep tunnels. Traditional methods of weakening thick and hard roofs are forced roof caving or pre-cracking of the roof by artificial blasting, which has the disadvantages of large engineering and explosive quantities and pollution of the working environment. In addition, high-gas mines have great safety hazards for drilling and blasting. In recent years, hydraulic fracturing methods for treating thick and hard roofs have made rapid progress, and field practice has confirmed that hydraulic fracturing has a good effect on weakening the roof.

[0005] Hydraulic fracturing injects high-pressure water through a borehole. Under the action of fluid-solid coupling, the borehole wall breaks and expands. These cracks change the properties of the rock mass, weaken the mechanical properties of the rock mass, and reduce the overall strength of the roof rock. In recent years, hydraulic fracturing technology has been widely used in the coal mining industry, including hydraulic fracturing control of hard roof, handling of initial roof caving, end hanging roof problems, protection of empty tunnels, weakening of hard roof coal, handling of coal pillars left in overlying goafs, coal seam permeability enhancement, and rock burst prevention and control, and has achieved good application results. The core of hydraulic fracturing to weaken the roof is to design the fracturing drilling layout and fracturing layer according to the specific working face mining layout conditions.

[0006] However, there is no targeted hydraulic fracturing control idea for the deformation control problem of the large tunnel roof in the high-stress mining area under the working face. Therefore, there is an urgent need for a targeted hydraulic fracturing control idea that takes into account the characteristics of the large tunnel under the working face to solve the deformation control problem of the surrounding rock in the large tunnel under the working face. Summary of the invention

[0007] The technical purpose to be achieved by the present invention is to control the deformation of surrounding rock in the main tunnel of the underlying mining area during mining of the working face, reduce the impact of mining of the working face on the main tunnel of the underlying mining area, and thus ensure safe and efficient production of the working face of the main tunnel of the underlying mining area.

[0008] In order to achieve the above technical objectives, the present invention adopts the following technical means:

[0009] A method for controlling deformation of surrounding rock of a large tunnel in a lower mining area during mining of a working face by hydraulic fracturing, which reduces the influence of mining dynamic pressure on the large tunnel in the lower mining area by fracturing the basic top to weaken the mining dynamic pressure stress source and fracturing the basic bottom to block the stress transmission path. First, drilling holes to the basic top rock layer and hydraulic fracturing are carried out in the return air level tunnel and the transport level tunnel of the mining working face to weaken the thick hard rock layer of the basic top, and by reducing the pressure step distance of the basic top fracture, the mining dynamic pressure of the working face is reduced from the source; then drilling holes to the basic bottom rock layer in the large tunnel and upper mountain of the lower mining area, hydraulic slit directional hydraulic fracturing is carried out, and a weak structural surface is formed in the basic bottom rock layer above the large tunnel and upper mountain of the mining area, so as to block the stress transmission path of the mining dynamic pressure to the large tunnel and upper mountain of the lower mining area, and reduce the deformation of the large tunnel and upper mountain of the lower mining area;

[0010] The specific steps include:

[0011] S1. Conduct geological exploration and core sampling: construct vertical upward coal seam top and bottom lithology detection holes in the bottom slab tunnel, bottom slab uphill tunnel, working face transport tunnel and return air tunnel, and conduct laboratory rock mechanical property tests, including: uniaxial compressive strength, tensile strength, Poisson's ratio, elastic modulus and shear modulus; determine the basic top rock layer and basic bottom rock layer as the target rock layer for subsequent fracturing according to the physical and mechanical properties of rocks in different layers; collect the basic top cycle pressure step;

[0012] S2. Arrange fracturing holes in the transport lane and return air lane of the working face in a fan-shaped arrangement: the final hole position of the fracturing hole is the basic top rock layer determined in step S1; the final hole spacing of each hole in the fan-shaped drilling group is 15-20 m, and the spacing between adjacent drilling sites is 10-15 m, which is less than the basic top cycle pressure step; a group of fan-shaped holes is a straight line connecting the final hole positions perpendicular to the advancing direction of the working face; a group of fan-shaped holes are all arranged in the transport lane or return air lane, or both the transport lane and the return air lane, and the specific hole opening position is determined according to the construction conditions;

[0013] S3. Arrange the fracturing system: the liquid supply pipeline continuously supplies fracturing fluid to the water tank, the fracturing fluid in the water tank enters the high-pressure pump through the static pressure head, a part of the fracturing fluid is pressurized by the high-pressure pump and enters the high-pressure hose to flow to the high-pressure sealed drill pipe, and the other part returns to the water tank through the return hose; the high-pressure hose is connected to a tee and a pressure relief valve for pressure relief; the high-pressure hose is connected to a water pressure and flow monitoring sensor for monitoring the water pressure and flow in the pipeline during the fracturing process;

[0014] S4. Fracturing the deepest target fracturing rock layer in the current borehole: Push the one-way valve into the target fracturing rock layer, start the high-pressure pump, and fractur the target rock layer for a certain period of time to weaken the thick and hard rock layer at the basic top, reduce the pressure step distance of the basic top fracture, and reduce the dynamic pressure of the working face from the source;

[0015] S5. The fracturing of the current borehole is finished, the pipeline is depressurized, and the second target rock layer is fractured: when the real-time water pressure of the water pressure monitoring sensor is continuously less than 5 MPa, or water is discharged from the adjacent borehole or roof for more than 8 minutes, the high-pressure pump is turned off, the pressure relief valve connected to the high-pressure hose is opened, and the pipeline is depressurized; if there are multiple target fracturing rock layers in the current borehole, the backward staged fracturing is adopted, and part of the drill pipe is withdrawn to make the one-way valve retreat to the position of the second target rock layer, and the second target rock layer of the current borehole is continued to be fractured. The above operation is repeated for single-hole fracturing until the fracturing of all target rock layers in the current borehole is completed;

[0016] S6. Drill holes vertically upwards in the base plate uphill to the basic bottom rock layer, and perform hydraulic slit directional hydraulic fracturing: send the slit drill bit to the target fracturing layer by a drilling rig, inject high-pressure water, rotate the drill pipe in situ for t minutes, maintain the water pressure of 20-30 MPa, and after forming radial hydraulic slits, withdraw the drill pipe, replace the hydraulic fracturing packer, perform fracturing at the target fracturing layer, and perform steps S3-S5 to form a horizontal weak structural surface, block the stress propagation path of mining dynamic pressure from the working face to the upper mountain of the underlying mining area, and reduce the deformation of the upper mountain of the mining area;

[0017] S7. Drill holes vertically upward in the bottom slab tunnel to the basic bottom rock layer, repeat step S6, and carry out hydraulic cutting and directional hydraulic fracturing to block the stress propagation path of mining dynamic pressure to the underlying tunnels in the mining area, reduce the deformation of the tunnels in the mining area, and extend their service life.

[0018] In step S1, a plurality of target rock formations are selected.

[0019] In step S2, for the fracturing boreholes arranged in the transport lane and the return air lane of the working face, a directional drilling rig is used to construct directional long boreholes instead of fan-shaped holes, thereby reducing the drilling construction workload.

[0020] In step S3, the fracturing fluid is clean water or a guar gum solution with a viscosity of 0.15% to 0.3%.

[0021] In step S4, the drilling and fracturing in the transport tunnel and the return air tunnel of the working face is carried out before the working face is 200 m away from the uphill position closest to the advancing direction.

[0022] In step S4, the fracturing time is determined according to the physical and mechanical properties of the rock formation. The fracturing time of the thick hard sandstone layer is 25-30 minutes, and the fracturing time of the thick hard mudstone layer is 10-15 minutes.

[0023] In step S6, the drill pipe rotates in situ for t minutes, where the value of t is in the range of 8 to 12 minutes.

[0024] In step S7, the drilling and fracturing of the bottom plate tunnel is carried out before the working face advances to a horizontal distance of 200 m from the borehole.

[0025] The beneficial effects of the present invention are:

[0026] In order to solve the engineering problem of large deformation and difficult-to-control surrounding rock of large tunnels in the underlying mining area during mining of the working face, the concept of "weakening the source and blocking the path" is adopted for hydraulic fracturing to control large deformation of surrounding rock of large tunnels in the underlying mining area. The thick and hard rock layer at the basic top is weakened by hydraulic fracturing, and the pressure step distance of the basic top fracture is reduced, so as to reduce the dynamic pressure of mining at the working face from the source. Drill holes are constructed in the large tunnels and upper hills of the underlying mining area to the basic bottom rock layer, and hydraulic cutting and directional hydraulic fracturing are carried out to form weak structural surfaces in the basic bottom rock layer above the large tunnels and upper hills of the mining area, so as to block the stress propagation path of mining dynamic pressure to the large tunnels and upper hills of the underlying mining area, and reduce the deformation of the large tunnels and upper hills of the underlying mining area.

[0027] Through the above two aspects, the deformation control of the surrounding rock of the large tunnel in the underlying mining area is achieved, which ensures the safe production of the large tunnel mining face in the underlying mining area. It has the characteristics of simplicity, high efficiency, convenient construction, low cost and no pollution.

[0028] At the same time, since there is no need to leave a large area of ​​protective coal pillars during the mining process of the working face, the waste of coal resources is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the plan arrangement of drilling holes for the method of controlling the deformation of surrounding rock by hydraulic fracturing of the main tunnel of the underlying mining area when the working face recovers the main tunnel of the underlying mining area when the main tunnel of the underlying mining area is oblique to the advancing direction of the working face;

[0030] Figure 2 yes Figure 1 The AA section is a schematic diagram of the drilling section in the working face advancement direction;

[0031] Figure 3 yes Figure 1 The BB section is a schematic diagram of the drilling section perpendicular to the advancing direction of the working face;

[0032] Figure 4 It is a schematic diagram of the plan arrangement of drilling holes of a method for controlling deformation of surrounding rock by hydraulic fracturing of a large tunnel in ...

[0033] Figure 5 yes Figure 4 The CC section is a schematic diagram of the drilling section in the working face advancement direction;

[0034] Figure 6 It is a schematic diagram of the plan arrangement of drilling holes of a method for controlling deformation of surrounding rock by hydraulic fracturing of a large tunnel in ...

[0035] Figure 7 yes Figure 6 The DD section is a schematic diagram of the drilling section in the working face advancement direction;

[0036] In the figure, 1-the main tunnel of the underlying mining area; 2-the transport tunnel of the working face; 3-the return air tunnel of the working face; 4-the goaf; 5-the designed stop mining line of the working face; 6-the working face; 7-the first hydraulic fracturing drilling group; 8-the second hydraulic fracturing drilling group; 9-the third hydraulic fracturing drilling; 10-the high basic top; 11-the low basic top; 12-the basic bottom rock layer; 13-the coal seam; 14-the direct top; 15-the hydraulic fracturing weakened zone of the low basic top; 16-the hydraulic fracturing weakened zone of the high basic top; 17-the basic bottom hydraulic fracturing weak structural surface of the main tunnel of the underlying mining area; 18-the mining area track going up the mountain; 19-the return air going up the mountain in the mining area; 20-the mining area transportation going up the mountain; 21-the fourth hydraulic fracturing drilling; 22-the basic bottom hydraulic fracturing weak structural surface of the going up the mountain in the underlying mining area. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0038] For cross-mining of the working face of the large tunnel in the underlying mining area under the condition of great burial depth, during the mining process of the working face, the overlying rock strata rotate and deform, the basic roof breaks periodically, and the strain energy accumulated in the roof rock strata is suddenly released, causing the mining stress to be transmitted to the large tunnel in the mining area below the working face through the basic bottom rock stratum with high strength, high rigidity and good integrity, changing the surrounding rock stress environment of the large tunnel in the underlying mining area, and easily causing large deformation of the surrounding rock, breaking and failure of the supporting components, etc., resulting in the difficulty of surrounding rock control in the large tunnel in the mining area. In view of the above problems, the present invention proposes a method for controlling the deformation of the surrounding rock of the large tunnel in the underlying mining area during the mining of the working face by hydraulic fracturing. Through three embodiments, respectively, the large tunnel in the underlying mining area is oblique, vertical and parallel to the advancing direction of the working face, and the method for controlling the deformation of the surrounding rock of the large tunnel in the underlying mining area during the mining of the working face is described in detail. Example

[0039] like Figure 1 , Figure 2 , Figure 3 As shown, for the case where the main tunnel in the underlying mining area is oblique to the advancing direction of the working face, the method for controlling the deformation of the surrounding rock hydraulic fracturing of the main tunnel in the underlying mining area during mining of the working face provided by the present invention has the following specific implementation steps:

[0040] Step S1, carry out geological exploration and core sampling: carry out laboratory rock mechanical property tests in the underground mining area main tunnel 1, working face transport tunnel 2, working face return air tunnel 3, mining area track uphill 18, mining area return air uphill 19, mining area transport uphill 20, and vertical upward coal seam top and bottom lithology detection holes in the middle construction, including: uniaxial compressive strength, tensile strength, Poisson's ratio, elastic modulus and shear modulus. Determine the basic top and basic bottom rock layers according to the physical and mechanical properties of rocks in different layers as the target rock layers for subsequent fracturing, and multiple target fracturing rock layers can be selected; collect the basic top cycle pressure step.

[0041] Step S2, arrange the first hydraulic fracturing drilling group 7 in a fan-shaped hole arrangement in the working face transport tunnel 2, and arrange the second hydraulic fracturing drilling group 8 in a fan-shaped hole arrangement in the working face return air tunnel 3, and the final hole position of the drilling is the high basic top 10 determined in step S1.

[0042] The first hydraulic fracturing drilling group 7 arranged in the transport lane of the working face and the second hydraulic fracturing drilling group 8 arranged in the return air lane of the working face, the terminal hole spacing of each borehole in the fan-shaped drilling group is 15~20 m, and the spacing between adjacent drilling sites is 10~15 m, which should be smaller than the basic top cycle pressure step distance.

[0043] The fan-shaped hole arrangement reduces the time for drilling rigs to drill holes and move the drilling rigs, which is beneficial to improving the efficiency of drilling and fracturing construction.

[0044] Step S3, arranging the fracturing system: the liquid supply pipeline continuously supplies fracturing fluid to the water tank, the fracturing fluid in the water tank enters the high-pressure pump through the static pressure head, a part of the fracturing fluid is pressurized by the high-pressure pump, enters the high-pressure hose and flows to the high-pressure sealed drill pipe, and the other part returns to the water tank through the return hose; the high-pressure hose is connected to a tee and a pressure relief valve for pressure relief; the high-pressure hose is connected to a water pressure and flow monitoring sensor for monitoring the water pressure and flow in the pipeline during the fracturing process;

[0045] The fracturing system includes: a high-pressure pump, a water tank, a liquid supply hose, a high-pressure hose, a high-pressure sealing drill pipe, a pressure relief valve, a pressure monitor, a flow monitor, a hole mouth packer, a hole bottom packer, a one-way valve, a variable head, and a U-shaped card;

[0046] The fracturing fluid is clean water or a guar gum solution with a certain viscosity.

[0047] Step S4, fracturing the high basic top 10 of the target fracturing rock formation of the current borehole: push the one-way valve into the target fracturing rock formation, start the high-pressure pump, and fracture the target rock formation for a certain period of time to form a high basic top water pressure fracturing weakened zone 16 in the high basic top 10, reduce the pressure step distance of the basic top breaking, and reduce the dynamic pressure of the working face from the source.

[0048] The fracturing start time of the second hydraulic fracturing drilling group 8 in the working face transport tunnel 2 and the working face return air tunnel 3 must be 200 m before the working face is closest to the uphill in the advancing direction.

[0049] The fracturing time is determined according to the physical and mechanical properties of the rock formation. The fracturing time for thick hard sandstone layers is 25~30 minutes, and the fracturing time for thick hard mudstone layers is 10~15 minutes.

[0050] Step S5, the fracturing of the current borehole is completed, the pipeline is depressurized, and the second section of the target rock formation is fractured to form a low basic top hydraulic fracturing weakened zone 15 in the low basic top 11;

[0051] When the real-time water pressure of the water pressure monitoring sensor is continuously less than 5 MPa, or the adjacent borehole or roof has been producing water for more than 8 minutes, turn off the high-pressure pump, open the pressure relief valve connected to the high-pressure hose, and depressurize the pipeline; if there are multiple target fracturing rock layers in this borehole, adopt the backward staged fracturing, withdraw the drill pipe to make the one-way valve retreat, and continue to fracturing the second target rock layer in this borehole. Repeat the above operation for single-hole fracturing until all target rock layers in this borehole are fractured;

[0052] Step S6, constructing a third hydraulic fracturing borehole 9 vertically upward in the main tunnel 1 of the underlying mining area to the basic bottom rock layer 12, repeating step S6, performing hydraulic slit directional hydraulic fracturing, forming a basic bottom hydraulic fracturing weak structural surface 17 of the main tunnel of the underlying mining area, blocking the stress propagation path of the mining dynamic pressure to the main tunnel 1 of the underlying mining area, reducing the deformation of the main tunnel of the mining area, and extending its service life;

[0053] The fracturing start time of the third hydraulic fracturing borehole 9 arranged in the main tunnel 1 of the underlying mining area needs to be before the working face advances to a horizontal distance of 200 m from the borehole.

[0054] The third hydraulic fracturing borehole 9 arranged in the main tunnel 1 of the underlying mining area perpendicular to the advancing direction of the working face, the first hydraulic fracturing borehole group 7 arranged in the working face transport tunnel 2, and the second hydraulic fracturing borehole group 8 arranged in the working face return air tunnel 3 should be fractured synchronously.

[0055] Step S7, when the working face is advanced to a distance of 200 m from the mining area return air uphill 19, the fourth hydraulic fracturing borehole 21 is vertically constructed upwards in the mining area track uphill 18, the mining area return air uphill 19, and the mining area transportation uphill 20 to the basic bottom rock layer 12, and hydraulic slit directional hydraulic fracturing is performed. The slit drill bit is sent to the target fracturing layer by a drilling rig, and high-pressure water is injected. The drill pipe is rotated in situ for 10 minutes, and the water pressure is maintained at 20-30 MPa. After the radial hydraulic slit is formed, the drill pipe is withdrawn, the hydraulic fracturing packer is replaced, and fracturing is performed at the target fracturing. Steps S3-S5 are performed to form the basic bottom hydraulic fracturing weak structural surface 22 of the underlying mining area uphill, block the stress propagation path of the mining dynamic pressure from the working face to the underlying mining area uphill, and reduce the deformation of the mining area uphill;

[0056] Step S8, when the working face advances to cross the mining area track uphill 18, the mining area return air uphill 19, and the mining area transportation uphill 20, continue fracturing the third hydraulic fracturing drill hole 9 arranged in the underlying mining area main tunnel 1, the first hydraulic fracturing drill hole group 7 arranged in the working face transportation tunnel 2, and the second hydraulic fracturing drill hole group 8 arranged in the working face return air tunnel 3. Example

[0057] like Figure 4 , Figure 5 As shown, for the case where the main tunnel in the underlying mining area is perpendicular to the advancing direction of the working face, the method for controlling the deformation of the surrounding rock hydraulic fracturing of the main tunnel in the underlying mining area during mining of the working face provided by the present invention has the following specific implementation steps:

[0058] Step S1, carry out geological exploration and core sampling: carry out laboratory rock mechanical property tests in the underground mining area main tunnel 1, working face transport tunnel 2, working face return air tunnel 3, mining area track uphill 18, mining area return air uphill 19, mining area transport uphill 20, and vertical upward coal seam top and bottom lithology detection holes in the middle construction, including: uniaxial compressive strength, tensile strength, Poisson's ratio, elastic modulus and shear modulus. Determine the basic top and basic bottom rock layers according to the physical and mechanical properties of rocks in different layers as the target rock layers for subsequent fracturing, and multiple target fracturing rock layers can be selected; collect the basic top cycle pressure step.

[0059] Step S2, arrange the first hydraulic fracturing drilling group 7 in a fan-shaped hole arrangement in the working face transport tunnel 2, and arrange the second hydraulic fracturing drilling group 8 in a fan-shaped hole arrangement in the working face return air tunnel 3, and the final hole position of the drilling is the high basic top 10 determined in step S1.

[0060] A first hydraulic fracturing drilling group 7 is arranged in the transport level tunnel of the working face, and a second hydraulic fracturing drilling group 8 is arranged in the return air level tunnel of the working face. The final hole spacing of each borehole in the fan-shaped drilling group is 15~20 m, and the spacing between adjacent drilling sites is 10~15 m, which should be smaller than the basic top cycle pressure step distance.

[0061] The fan-shaped hole arrangement reduces the time for drilling rigs to drill holes and move the drilling rigs, which is beneficial to improving the efficiency of drilling and fracturing construction.

[0062] Step S3, arranging the fracturing system: the liquid supply pipeline continuously supplies fracturing fluid to the water tank, the fracturing fluid in the water tank enters the high-pressure pump through the static pressure head, a part of the fracturing fluid is pressurized by the high-pressure pump, enters the high-pressure hose and flows to the high-pressure sealed drill pipe, and the other part returns to the water tank through the return hose; the high-pressure hose is connected to a tee and a pressure relief valve for pressure relief; the high-pressure hose is connected to a water pressure and flow monitoring sensor for monitoring the water pressure and flow in the pipeline during the fracturing process;

[0063] The fracturing system includes: a high-pressure pump, a water tank, a liquid supply hose, a high-pressure hose, a high-pressure sealing drill pipe, a pressure relief valve, a pressure monitor, a flow monitor, a hole mouth packer, a hole bottom packer, a one-way valve, a variable head, and a U-shaped card; the fracturing fluid is clear water or a guar gum solution with a certain viscosity.

[0064] Step S4, fracturing the high basic top 10 of the target fracturing rock formation of the current borehole: push the one-way valve into the target fracturing rock formation, start the high-pressure pump, and fracture the target rock formation for a certain period of time to form a high basic top water pressure fracturing weakened zone 16 in the high basic top 10, reduce the pressure step distance of the basic top breaking, and reduce the dynamic pressure of the working face from the source.

[0065] When the working face is advanced to a distance of 200 m from the mining area return air uphill 19, the fourth hydraulic fracturing borehole 21 is vertically constructed upwards in the mining area track uphill 18, the mining area return air uphill 19, and the mining area transportation uphill 20 to the basic bottom rock layer 12, and hydraulic slit directional hydraulic fracturing is performed. The slit drill bit is sent to the target fracturing layer by a drilling rig, and high-pressure water is injected. The drill pipe is rotated in situ for 10 minutes, and the water pressure is maintained at 20-30 MPa. After the radial hydraulic slit is formed, the drill pipe is withdrawn, the hydraulic fracturing packer is replaced, and fracturing is performed at the target fracturing. Steps S3-S5 are performed to form the basic bottom hydraulic fracturing weak structural surface 22 of the underlying mining area uphill, block the stress propagation path of the mining dynamic pressure from the working face to the underlying mining area uphill, and reduce the deformation of the mining area uphill;

[0066] The fracturing time is determined according to the physical and mechanical properties of the rock formation. The fracturing time for thick hard sandstone layers is 25~30 minutes, and the fracturing time for thick hard mudstone layers is 10~15 minutes.

[0067] Step S5, the fracturing of the current borehole is completed, the pipeline is depressurized, and the second section of the target rock formation is fractured to form a low basic top hydraulic fracturing weakened zone 15 in the low basic top 11;

[0068] When the real-time water pressure of the water pressure monitoring sensor is continuously less than 5 MPa, or the adjacent borehole or roof has been producing water for more than 8 minutes, turn off the high-pressure pump, open the pressure relief valve connected to the high-pressure hose, and depressurize the pipeline; if there are multiple target fracturing rock layers in this borehole, adopt the backward staged fracturing, withdraw the drill pipe to make the one-way valve retreat, and continue to fracturing the second target rock layer in this borehole. Repeat the above operation for single-hole fracturing until all target rock layers in this borehole are fractured;

[0069] Step S6, constructing a borehole 9 vertically upward in the main tunnel 1 of the underlying mining area to the basic bottom rock layer 12, repeating step S6, performing hydraulic slitting and directional hydraulic fracturing, forming a basic bottom hydraulic fracturing weak structural surface 17 of the main tunnel of the underlying mining area, blocking the stress propagation path of the mining dynamic pressure to the main tunnel 1 of the underlying mining area, reducing the deformation of the main tunnel of the mining area, and extending its service life;

[0070] The fracturing start time of the third hydraulic fracturing borehole 9 arranged in the main tunnel 1 of the underlying mining area needs to be before the working face advances to a horizontal distance of 200 m from the borehole.

[0071] Step S7, when the working face is advanced to a distance of 200 m from the mining area return air uphill 19, the fourth hydraulic fracturing borehole 21 is vertically constructed upwards in the mining area track uphill 18, the mining area return air uphill 19, and the mining area transportation uphill 20 to the basic bottom rock layer 12, and hydraulic slit directional hydraulic fracturing is performed. The slit drill bit is sent to the target fracturing layer by a drilling rig, and high-pressure water is injected. The drill pipe is rotated in situ for 10 minutes, and the water pressure is maintained at 20-30 MPa. After the radial hydraulic slit is formed, the drill pipe is withdrawn, the hydraulic fracturing packer is replaced, and fracturing is performed at the target fracturing. Steps S3-S5 are performed to form the basic bottom hydraulic fracturing weak structural surface 22 of the underlying mining area uphill, block the stress propagation path of the mining dynamic pressure from the working face to the underlying mining area uphill, and reduce the deformation of the mining area uphill;

[0072] Step S8, when the working face advances to cross the mining area track uphill 18, the mining area return air uphill 19, and the mining area transportation uphill 20, continue to fracturing the third hydraulic fracturing drill hole 9 arranged in the underlying mining area main tunnel 1, the first hydraulic fracturing drill hole group 7 arranged in the working face transportation horizontal tunnel 2, and the second hydraulic fracturing drill hole group 8 arranged in the working face return air horizontal tunnel 3. Example

[0073] like Figure 6 , Figure 7 As shown, for the case where the main tunnel in the underlying mining area is parallel to the advancing direction of the working face, the method for controlling the deformation of surrounding rock hydraulic fracturing of the main tunnel in the underlying mining area during mining of the working face provided by the present invention has the following specific implementation steps:

[0074] Step S1, carry out geological exploration and core sampling: carry out laboratory rock mechanical property tests in the underground mining area main tunnel 1, working face transport tunnel 2, working face return air tunnel 3, mining area track uphill 18, mining area return air uphill 19, mining area transport uphill 20, and vertical upward coal seam top and bottom lithology detection holes in the middle construction, including: uniaxial compressive strength, tensile strength, Poisson's ratio, elastic modulus and shear modulus. Determine the basic top and basic bottom rock layers according to the physical and mechanical properties of rocks in different layers as the target rock layers for subsequent fracturing, and multiple target fracturing rock layers can be selected; collect the basic top cycle pressure step.

[0075] Step S2, arrange the first hydraulic fracturing drilling group 7 in a fan-shaped hole arrangement in the working face transport tunnel 2, and arrange the second hydraulic fracturing drilling group 8 in a fan-shaped hole arrangement in the working face return air tunnel 3, and the final hole position of the drilling is the high basic top 10 determined in step S1.

[0076] A first hydraulic fracturing drilling group 7 is arranged in the transport level tunnel of the working face, and a second hydraulic fracturing drilling group 8 is arranged in the return air level tunnel of the working face. The final hole spacing of each borehole in the fan-shaped drilling group is 15~20 m, and the spacing between adjacent drilling sites is 10~15 m, which should be smaller than the basic top cycle pressure step distance.

[0077] The fan-shaped hole arrangement reduces the time for drilling rigs to drill holes and move the drilling rigs, which is beneficial to improving the efficiency of drilling and fracturing construction.

[0078] Step S3, arranging the fracturing system: the liquid supply pipeline continuously supplies fracturing fluid to the water tank, the fracturing fluid in the water tank enters the high-pressure pump through the static pressure head, a part of the fracturing fluid is pressurized by the high-pressure pump, enters the high-pressure hose and flows to the high-pressure sealed drill pipe, and the other part returns to the water tank through the return hose; the high-pressure hose is connected to a tee and a pressure relief valve for pressure relief; the high-pressure hose is connected to a water pressure and flow monitoring sensor for monitoring the water pressure and flow in the pipeline during the fracturing process;

[0079] The fracturing system includes: a high-pressure pump, a water tank, a liquid supply hose, a high-pressure hose, a high-pressure sealing drill pipe, a pressure relief valve, a pressure monitor, a flow monitor, a hole mouth packer, a hole bottom packer, a one-way valve, a variable head, and a U-shaped card; the fracturing fluid is clear water or a guar gum solution with a certain viscosity.

[0080] Step S4, fracturing the high basic top 10 of the target fracturing rock formation of the current borehole: push the one-way valve into the target fracturing rock formation, start the high-pressure pump, and fracture the target rock formation for a certain period of time to form a high basic top water pressure fracturing weakened zone 16 in the high basic top 10, reduce the pressure step distance of the basic top breaking, and reduce the dynamic pressure of the working face from the source.

[0081] The fracturing of borehole 8 in the working face transport tunnel 2 and return air tunnel 3 must start 200 m before the working face is closest to the uphill direction.

[0082] The fracturing time is determined according to the physical and mechanical properties of the rock formation. The fracturing time for thick hard sandstone layers is 25~30 minutes, and the fracturing time for thick hard mudstone layers is 10~15 minutes.

[0083] Step S5, the fracturing of the current borehole is completed, the pipeline is depressurized, and the second section of the target rock formation is fractured to form a low basic top hydraulic fracturing weakened zone 15 in the low basic top 11;

[0084] When the real-time water pressure of the water pressure monitoring sensor is continuously less than 5 MPa, or the adjacent borehole or roof has been producing water for more than 8 minutes, turn off the high-pressure pump, open the pressure relief valve connected to the high-pressure hose, and depressurize the pipeline; if there are multiple target fracturing rock layers in this borehole, adopt the backward staged fracturing, withdraw the drill pipe to make the one-way valve retreat, and continue to fracturing the second target rock layer in this borehole. Repeat the above operation for single-hole fracturing until all target rock layers in this borehole are fractured;

[0085] Step S6, constructing a third hydraulic fracturing borehole 9 vertically upward in the main tunnel 1 of the underlying mining area to the basic bottom rock layer 12, repeating step S6, performing hydraulic slit directional hydraulic fracturing, forming a basic bottom hydraulic fracturing weak structural surface 17 of the main tunnel of the underlying mining area, blocking the stress propagation path of the mining dynamic pressure to the main tunnel 1 of the underlying mining area, reducing the deformation of the main tunnel of the mining area, and extending its service life;

[0086] The fracturing start time of the third hydraulic fracturing borehole 9 arranged in the main tunnel 1 of the underlying mining area needs to be before the working face advances to a horizontal distance of 200 m from the borehole.

[0087] The third hydraulic fracturing borehole 9 arranged in the main tunnel 1 of the underlying mining area perpendicular to the advancing direction of the working face, the first hydraulic fracturing borehole group 7 arranged in the working face transport tunnel 2, and the second hydraulic fracturing borehole group 8 arranged in the working face return air tunnel 3 should be fractured synchronously.

[0088] Step S7, when the working face is advanced to a distance of 200 m from the mining area return air uphill 19, the fourth hydraulic fracturing borehole 21 is vertically constructed upwards in the mining area track uphill 18, the mining area return air uphill 19, and the mining area transportation uphill 20 to the basic bottom rock layer 12, and hydraulic slit directional hydraulic fracturing is performed. The slit drill bit is sent to the target fracturing layer by a drilling rig, and high-pressure water is injected. The drill pipe is rotated in situ for 10 minutes, and the water pressure is maintained at 20-30 MPa. After the radial hydraulic slit is formed, the drill pipe is withdrawn, the hydraulic fracturing packer is replaced, and fracturing is performed at the target fracturing. Steps S3-S5 are performed to form the basic bottom hydraulic fracturing weak structural surface 22 of the underlying mining area uphill, block the stress propagation path of the mining dynamic pressure from the working face to the underlying mining area uphill, and reduce the deformation of the mining area uphill;

[0089] Step S8, when the working face advances to cross the mining area track uphill 18, the mining area return air uphill 19, and the mining area transportation uphill 20, continue to fracturing the third hydraulic fracturing drill hole 9 arranged in the underlying mining area main tunnel 1, the first hydraulic fracturing drill hole group 7 arranged in the working face transportation horizontal tunnel 2, and the second hydraulic fracturing drill hole group 8 arranged in the working face return air horizontal tunnel 3.

[0090] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited thereto. Various changes that can be made within the knowledge scope of technicians in the relevant technical field without departing from the spirit of the present invention are all within the protection scope of the claims of the present invention.

Claims

1. A method for controlling deformation of surrounding rock by hydraulic fracturing in a large tunnel in a working face mining area, characterized in that: By fracturing the basic top to weaken the source of mining dynamic pressure stress and fracturing the basic bottom to block the stress transmission path, the impact of mining dynamic pressure on the main tunnels in the underlying mining area can be reduced. First, drill holes to the basic top rock layer in the return air level tunnel and the transportation level tunnel of the mining working face and perform hydraulic fracturing to weaken the thick and hard rock layer of the basic top. By reducing the pressure step distance of the basic top fracture, the mining dynamic pressure of the working face can be reduced from the source; then drill holes to the basic bottom rock layer in the main tunnel and upper mountain of the underlying mining area, and perform hydraulic slit directional hydraulic fracturing to form a weak structural surface in the basic bottom rock layer above the main tunnel and upper mountain of the mining area, so as to block the stress transmission path of mining dynamic pressure to the main tunnel and upper mountain of the underlying mining area, and reduce the deformation of the main tunnel and upper mountain of the underlying mining area; The specific steps include: S1. Conduct geological exploration and core sampling: construct vertical upward coal seam top and bottom lithology detection holes in the bottom slab tunnel, bottom slab uphill tunnel, working face transport tunnel and return air tunnel, and conduct laboratory rock mechanical property tests, including: uniaxial compressive strength, tensile strength, Poisson's ratio, elastic modulus and shear modulus; determine the basic top rock layer and basic bottom rock layer as the target rock layer for subsequent fracturing according to the physical and mechanical properties of rocks in different layers; collect the basic top cycle pressure step; S2. Arrange fracturing holes in the transport lane and return air lane of the working face in a fan-shaped arrangement: the final hole position of the fracturing hole is the basic top rock layer determined in step S1; the final hole spacing of each hole in the fan-shaped drilling group is 15-20 m, and the spacing between adjacent drilling sites is 10-15 m, which is less than the basic top cycle pressure step; a group of fan-shaped holes is a straight line connecting the final hole positions perpendicular to the advancing direction of the working face; a group of fan-shaped holes are all arranged in the transport lane or return air lane, or both the transport lane and the return air lane, and the specific hole opening position is determined according to the construction conditions; S3. Arrange the fracturing system: the liquid supply pipeline continuously supplies fracturing fluid to the water tank, the fracturing fluid in the water tank enters the high-pressure pump through the static pressure head, a part of the fracturing fluid is pressurized by the high-pressure pump and enters the high-pressure hose to flow to the high-pressure sealed drill pipe, and the other part returns to the water tank through the return hose; the high-pressure hose is connected to a tee and a pressure relief valve for pressure relief; the high-pressure hose is connected to a water pressure and flow monitoring sensor for monitoring the water pressure and flow in the pipeline during the fracturing process; S4. Fracturing the deepest target fracturing rock layer in the current borehole: Push the one-way valve into the target fracturing rock layer, start the high-pressure pump, and fractur the target rock layer for a certain period of time to weaken the thick and hard rock layer at the basic top, reduce the pressure step distance of the basic top fracture, and reduce the dynamic pressure of the working face from the source; S5. The fracturing of the current borehole is finished, the pipeline is depressurized, and the second target rock layer is fractured: when the real-time water pressure of the water pressure monitoring sensor is continuously less than 5 MPa, or water is discharged from the adjacent borehole or roof for more than 8 minutes, the high-pressure pump is turned off, the pressure relief valve connected to the high-pressure hose is opened, and the pipeline is depressurized; if there are multiple target fracturing rock layers in the current borehole, the backward staged fracturing is adopted, and part of the drill pipe is withdrawn to make the one-way valve retreat to the position of the second target rock layer, and the second target rock layer of the current borehole is continued to be fractured. The above operation is repeated for single-hole fracturing until the fracturing of all target rock layers in the current borehole is completed; S6. Drill holes vertically upwards in the base plate uphill to the basic bottom rock layer, and perform hydraulic slit directional hydraulic fracturing: send the slit drill bit to the target fracturing layer by a drilling rig, inject sand-carrying fluid, rotate the drill pipe in situ for t minutes, maintain the water pressure of 20-30 MPa, and after forming radial hydraulic slits, withdraw the drill pipe, replace the hydraulic fracturing packer, perform fracturing in the target fracturing layer, and perform steps S3-S5 to form a horizontal weak structural surface, block the stress propagation path of mining dynamic pressure from the working face to the upper mountain of the underlying mining area, and reduce the deformation of the upper mountain of the mining area; S7. Drill holes vertically upward in the bottom slab tunnel to the basic bottom rock layer, repeat step S6, and carry out hydraulic cutting and directional hydraulic fracturing to block the stress propagation path of mining dynamic pressure to the underlying tunnels in the mining area, reduce the deformation of the tunnels in the mining area, and extend their service life.

2. The method for controlling deformation of surrounding rock by hydraulic fracturing in the large tunnel of the underlying mining area under the working face according to claim 1 is characterized in that: In step S1, a plurality of target rock formations are selected.

3. The method for controlling deformation of surrounding rock by hydraulic fracturing in the large tunnel of the underlying mining area under the working face according to claim 1 is characterized in that: In step S2, for the fracturing boreholes arranged in the transport lane and the return air lane of the working face, a directional drilling rig is used to construct directional long boreholes instead of fan-shaped holes, thereby reducing the drilling construction workload.

4. The method for controlling deformation of surrounding rock by hydraulic fracturing in the large tunnel of the underlying mining area under the working face according to claim 1 is characterized in that: In step S3, the fracturing fluid is clean water or a guar gum solution with a viscosity of 0.15% to 0.3%.

5. The method for controlling deformation of surrounding rock by hydraulic fracturing in the large tunnel of the underlying mining area of ​​the working face according to claim 1, characterized in that: In step S4, the drilling and fracturing in the transport tunnel and the return air tunnel of the working face is carried out before the working face is 200 m away from the uphill position closest to the advancing direction.

6. The method for controlling deformation of surrounding rock by hydraulic fracturing in a large tunnel in a working face mining area below the working face according to claim 1, characterized in that: In step S4, the fracturing time is determined according to the physical and mechanical properties of the rock formation. The fracturing time of the thick hard sandstone layer is 25-30 minutes, and the fracturing time of the thick hard mudstone layer is 10-15 minutes.

7. The method for controlling deformation of surrounding rock by hydraulic fracturing in the large tunnel of the underlying mining area under the working face according to claim 1 is characterized in that: In step S6, the drill pipe rotates in situ for t minutes, where the value of t is in the range of 8 to 12 minutes.

8. The method for controlling deformation of surrounding rock by hydraulic fracturing in a large tunnel in a working face mining area below the working face according to claim 1, characterized in that: In step S7, the drilling and fracturing of the bottom plate tunnel is carried out before the working face advances to a horizontal distance of 200 m from the borehole.

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