Slotting and fracturing method for roadway

Abstract

The invention relates to the field of coal mining, and discloses a roadway slotting and fracturing method which comprises the following steps: S1, arranging a plurality of groups of drill holes in two sides of a roadway; s2, cutting the surrounding rock in the drill hole to form a pre-crack; s3, injecting water into the pre-crack for fracturing to form a crack zone; wherein in the step S1, each set of drill holes comprises a plurality of drill holes which extend in the radial direction from a preset central axis and are spaced in the circumferential direction, the multiple drill holes in each set form a fan-shaped structure, and the preset central axis is parallel to the length direction of the roadway and located in the plane where the side portion is located. By means of the technical scheme, a high-stress concentration area which covers the top plate, the two sides and the bottom plate of the roadway and is of a gridding pressure relief structure is formed, and the surrounding rock stress peak value is greatly reduced; aligned and staggered drilling arrangement is combined, flexible adjustment can be achieved according to the property of surrounding rock, it is guaranteed that no blind area exists in crack network coverage, drilling, slotting and fracturing are completed synchronously, and operation efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of coal mining, and in particular to a tunnel slot fracturing method. Background Art

[0002] As coal mining continues to increase in depth, deep coal seams face increasingly prominent challenges such as high ground stress and strong mining disturbances. This leads to increased deformation of the surrounding rock and frequent rock bursts, seriously threatening safe and efficient mine production. Traditional tunnel protection technologies, such as bolting and grouting, can temporarily stabilize the surrounding rock but are unable to fundamentally alleviate the energy accumulation within the coal and rock masses. Furthermore, they require long construction cycles and are costly, making them unable to meet the long-term tunnel protection needs under complex geological conditions at depth.

[0003] Existing hydraulic fracturing technology is an active means of unloading pressure, which releases stress by generating cracks in coal rock. However, its application has significant limitations, such as single crack expansion, limited coverage of the crack network formed by unidirectional fracturing, uneven unloading effect, and easy residual local stress concentration areas, which can induce secondary dynamic disasters. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problem of insufficient pressure relief in the tunnel in the prior art.

[0005] In order to achieve the above-mentioned object, the present invention provides a slot fracturing method for a roadway, which comprises:

[0006] S1, arrange multiple groups of drill holes on the two sides of the tunnel;

[0007] S2, cutting surrounding rock in the borehole to form pre-cracks;

[0008] S3, injecting water into the pre-cracks for fracturing to form fracture zones;

[0009] In S1, each group of the drill holes includes a plurality of drill holes extending radially from a predetermined central axis and spaced circumferentially, and the plurality of the drill holes in each group form a fan-shaped structure, wherein the predetermined central axis is parallel to the length direction of the tunnel and is located in the plane where the side portion is located.

[0010] In some embodiments, in each group of the drill holes, the angle between adjacent drill holes is 30°-60°, and the angle of the fan-shaped structure is ≥120°.

[0011] In some embodiments, on the same side of the tunnel, the distance between two adjacent groups of drill holes is ≤8m, and in each group of drill holes, the distance between radial distal ends of adjacent drill holes is ≤5m.

[0012] In some embodiments, the multiple groups of drill holes on the two sides are aligned one by one along the width direction of the tunnel, the spacing between two adjacent groups of drill holes is ≤5m, and in each group of drill holes, the angle between adjacent drill holes is 30°-45°.

[0013] In some embodiments, each group of drill holes on one of the side parts is aligned with the midpoint between two groups of drill holes on the other side part along the width direction of the tunnel, and the spacing between two adjacent groups of drill holes is ≤8m. In each group of drill holes, the angle between adjacent drill holes is 45°-60°.

[0014] In some embodiments, in S1 , a drill rig is used to arrange a borehole, and low-pressure water injection is performed through the drill rig to cool the drill rig and discharge rock cuttings, wherein the water injection pressure is 4.5 MPa-5.5 MPa.

[0015] In some embodiments, in S2, the cutting blades on the drilling rig are deployed to cut the surrounding rock to form pre-cracks, and water is injected through the drilling rig at a water injection pressure of 20 to 30 MPa.

[0016] In some embodiments, the extension direction of the pre-crack is perpendicular to the central axis of the borehole, the cross-section of the pre-crack is wedge-shaped, and the maximum width of the pre-crack is ≥100 mm.

[0017] In some embodiments, in S3, after the sealer is installed, high-pressure water injection is performed to expand the pre-crack. The water injection pressure is 35 MPa-40 MPa, and the water injection lasts for 10 to 15 minutes, so that the crack expands to a width of ≥10 cm.

[0018] In some embodiments, the method further includes S4, monitoring the crack extension path in real time through an optical fiber sensor, and recording the stress release of the surrounding rock through a microseismic monitoring system.

[0019] Through the above technical solution, the grid-type pressure relief structure formed covers the high stress concentration areas of the tunnel roof, two sides and bottom plate, greatly reducing the peak stress of the surrounding rock; the combination of aligned and staggered drilling arrangements can be flexibly adjusted according to the properties of the surrounding rock, ensuring that the crack network covers no blind spots, and drilling, cutting and fracturing are completed simultaneously, thereby improving work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a plan view of the distribution of tunnels and boreholes according to one embodiment of the present invention;

[0021] Figure 2 is a plan view of the distribution of tunnels and boreholes according to another embodiment of the present invention;

[0022] Figure 3 This is a cross-sectional view of a tunnel according to an embodiment of the present scheme.

[0023] Description of Reference Numerals

[0024] 1-tunnel, 2-drilling, 3-pre-crack DETAILED DESCRIPTION

[0025] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0026] This solution provides a tunnel slot fracturing method, which includes:

[0027] S1, arrange multiple groups of drill holes 2 on the two sides of tunnel 1;

[0028] S2, cutting surrounding rock in the borehole 2 to form pre-cracks 3;

[0029] S3, injecting water into the pre-crack 3 for fracturing to form a fracture zone;

[0030] In S1, each group of the boreholes 2 includes a plurality of boreholes 2 radially extending from a predetermined central axis and circumferentially spaced, and the plurality of boreholes 2 in each group form a fan-shaped structure, wherein the predetermined central axis is parallel to the length direction of the tunnel 1 and is located in the plane where the side portion is located.

[0031] Among them, multiple groups of drill holes 2 are arranged on the two sides of the tunnel 1, referring to Figure 3 As shown, each group of boreholes 2 is distributed in a fan-shaped structure, i.e., multiple boreholes 2 are circumferentially spaced about a predetermined central axis, and adjacent boreholes 2 may have the same included angle. The predetermined central axis extends along the length of the tunnel 1 and is located in the plane of its sidewall. In particular, the predetermined central axis may be located above the sidewall, for example, at the junction of the sidewall and the roof, so that the boreholes 2 can partially extend to the top of the tunnel 1.

[0032] Pre-cracks 3 are formed by cutting the surrounding rock on the inner wall of the borehole 2, and further fracturing is performed to form a fracture zone. The fracture zones of the two adjacent fan-shaped boreholes 2 cross and overlap with each other to form a gridded pressure relief structure, covering the high stress concentration areas of the roadway roof, two sides and floor, and significantly reducing the peak stress of the surrounding rock.

[0033] In some embodiments, within each group of boreholes 2, the angle between adjacent boreholes 2 is 30°-60°, and the angle of the fan-shaped structure is ≥120°. The fan-shaped structure has a sufficiently large angular range so that the boreholes 2 and the resulting fracture zones can cover a larger area. Generally, the angles between adjacent boreholes 2 can be substantially the same, but can also be set to different angles as needed. The direction of the boreholes 2 can be substantially parallel to the coal seam bedding, with an angle deviation of ≤1°.

[0034] In some embodiments, the spacing between two adjacent groups of drill holes 2 on the same side of the tunnel 1 is ≤8 m. Within each group of drill holes 2, the spacing between the radially distal ends of adjacent drill holes 2 is ≤5 m. Along the length of the tunnel 1, adjacent groups of drill holes 2 are spaced at an appropriate distance, for example, 4-8 m, to ensure that the drill holes and the resulting fracture zones overlap. The radially distal end of a drill hole 2 is defined as the end that is distal to a predetermined central axis, with the predetermined central axis being the starting position of the drill hole 2.

[0035] In some embodiments, reference Figure 1 As shown, the multiple groups of drill holes 2 on the two sides are aligned one by one along the width direction of the tunnel 1, and the spacing between two adjacent groups of drill holes 2 is ≤5m. In each group of drill holes 2, the angle between adjacent drill holes 2 is 30°-45°.

[0036] In other embodiments, reference Figure 2 As shown, each group of drill holes 2 on one of the sides is aligned with the midpoint between two groups of drill holes 2 on the other side along the width direction of the tunnel 1, and the spacing between two adjacent groups of drill holes 2 is ≤8m. In each group of drill holes 2, the angle between adjacent drill holes 2 is 45°-60°.

[0037] In the above two different arrangements of the drill holes 2, when the drill holes 2 on the two sides are aligned, the spacing between the two adjacent groups of drill holes 2 is relatively small, while when the drill holes 2 on the two sides are staggered, the spacing between the two adjacent groups of drill holes 2 is relatively large.

[0038] In some embodiments, in S1, a drilling rig is used to arrange a borehole 2, and low-pressure water injection is performed by the drilling rig to cool the drill rig and remove rock cuttings. The water injection pressure is 4.5 MPa-5.5 MPa. When the drilling rig is drilling, the injected water can cool the drill bit and remove rock cuttings. The water injection pressure is relatively low, 4.5 MPa-5.5 MPa.

[0039] In some embodiments, in S2, a cutting blade on the drilling rig is deployed to cut the surrounding rock to form the pre-crack 3, and water is injected through the drilling rig at a pressure of 20 to 30 MPa. The drilling rig can also have a slitting function, and is provided with a retractable and deployable blade. The blade can cut the surrounding rock of the borehole 2 to form the pre-crack 3. In addition, the water injected by the drilling rig can be sprayed into the pre-crack 3 to remove rock cuttings.

[0040] In some embodiments, the pre-crack 3 extends perpendicular to the central axis of the borehole 2, has a wedge-shaped cross-section, and has a maximum width of ≥100 mm. The pre-crack 3 is generally strip-shaped, with its width gradually decreasing along its length, forming a wedge shape. The width of the larger end of the pre-crack 3 is greater than 100 mm.

[0041] In some embodiments, in S3, after the sealer is installed, high-pressure water injection is performed to expand the pre-crack 3, the water injection pressure is 35MPa-40Mpa, and the water injection lasts for 10 to 15 minutes, so that the crack expands to a width of ≥10cm.

[0042] In addition, some embodiments further include S4, which monitors the crack extension path in real time using fiber optic sensors and records the stress release of the surrounding rock using a microseismic monitoring system. Fiber optic sensors are installed on both sides and the roof of tunnel 1 to monitor the location of crack formation; the microseismic monitoring system can verify the pressure relief effect.

[0043] The following is an implementation method of the slot fracturing method in the tunnel:

[0044] The first step is to drill holes perpendicular to the direction of the tunnel on both sides and the roof and floor of the tunnel, with the holes arranged in a fan shape;

[0045] The second step is to start the drilling rig and inject low-pressure water (5MPa) to cool the drill bit and discharge the cuttings; after drilling to the target depth, stop drilling and keep the drill rod stationary.

[0046] The third step is cutting crack generation: start the hydraulic system, expand the blade and slowly rotate the drill pipe to form a wedge-shaped pre-crack perpendicular to the central axis of the drill hole.

[0047] Step 4: Retract the drill rod to the previous cutting position, adjust the blade angle and repeat the cutting.

[0048] Step 5: Install the sealer: Install the sealer 0.5-1.0m away from the nearest crack. High-pressure water injection: Inject 35-40MPa high-pressure water for 10-15 minutes to expand the crack to a width of ≥10cm.

[0049] Step 6: Monitoring and verification: Fiber optic sensors monitor the direction of crack extension in real time to ensure that the longitudinal crack zone is continuous.

[0050] Furthermore, in the first step, the distance between two adjacent groups of drill holes is 5 to 8 m, the depth is ≥ 12 m, and the diameter of the drill holes is 45 to 50 mm;

[0051] Furthermore, the drilling arrangement described in the second step can be arranged in the following two ways: the two sides of the drill holes are arranged symmetrically, with a spacing of ≤5m, and the angle of the single-side fan-shaped drill holes is 30°~45°; the two sides of the drill holes are staggered, with a staggered distance of 1 / 2 of the drilling spacing (2.5~4m), and the angle of the single-side fan-shaped drill holes is 45°~60°.

[0052] This solution uses an integrated drilling and cutting rig with carbide cutting teeth at the front end and a built-in high-pressure water channel. Drilling, slitting, and fracturing can be completed simultaneously, reducing the number of equipment switches and rod withdrawals.

[0053] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, the technical solution of the present invention may be subjected to a variety of simple modifications, including combining the various specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple modifications and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A tunnel slit fracturing method, characterized in that: include: S1, arrange multiple groups of drill holes on the two sides of the tunnel; S2, cutting surrounding rock in the borehole to form pre-cracks; S3, injecting water into the pre-cracks for fracturing to form fracture zones; In S1, each group of the drill holes includes a plurality of drill holes extending radially from a predetermined central axis and spaced circumferentially, and the plurality of the drill holes in each group form a fan-shaped structure, wherein the predetermined central axis is parallel to the length direction of the tunnel and is located in the plane where the side portion is located.

2. The slot fracturing method for a roadway according to claim 1, characterized in that: In each group of the drill holes, the angle between adjacent drill holes is 30°-60°, and the angle of the fan-shaped structure is ≥120°.

3. The slot fracturing method for a roadway according to claim 2, characterized in that: On the same side of the tunnel, the distance between two adjacent groups of drill holes is ≤8m, and in each group of drill holes, the distance between the radial distal ends of adjacent drill holes is ≤5m.

4. The tunnel slit fracturing method according to claim 3, characterized in that: The multiple groups of drill holes on the two sides are aligned one by one along the width direction of the tunnel, the spacing between two adjacent groups of drill holes is ≤5m, and in each group of drill holes, the angle between adjacent drill holes is 30°-45°.

5. The slot fracturing method for a roadway according to claim 4, characterized in that: Each group of drill holes on one of the sides is aligned with the midpoint between two groups of drill holes on the other side along the width direction of the tunnel, and the spacing between two adjacent groups of drill holes is ≤8m. In each group of drill holes, the angle between adjacent drill holes is 45°-60°.

6. The slot fracturing method for a roadway according to claim 1, characterized in that: In S1 , a drill rig is used to arrange a borehole, and low-pressure water injection is performed through the drill rig to cool the drill rig and discharge rock cuttings, wherein the water injection pressure is 4.5 MPa-5.5 MPa.

7. The slot fracturing method for a roadway according to claim 1, characterized in that: In S2, the cutting blades on the drilling rig are deployed to cut the surrounding rock to form pre-cracks, and water is injected through the drilling rig at a water injection pressure of 20 to 30 MPa.

8. The slot fracturing method for a roadway according to claim 7, characterized in that: The extension direction of the pre-crack is perpendicular to the central axis of the drill hole, the cross section of the pre-crack is wedge-shaped, and the maximum width of the pre-crack is ≥100 mm.

9. The tunnel slit fracturing method according to claim 1, characterized in that: In S3, after the sealer is installed, high-pressure water injection is performed to expand the pre-cracks. The water injection pressure is 35 MPa-40 MPa, and the water injection is continued for 10 to 15 minutes, so that the cracks expand to a width of ≥10 cm.

10. The slot fracturing method for a roadway according to claim 1, characterized in that: It also includes S4, which monitors the crack extension path in real time through fiber optic sensors and records the stress release of the surrounding rock through a microseismic monitoring system.

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