Fracturing stress control method for advance area of main roadway in coal mining area

Abstract

The invention relates to the technical field of coal mine roadway surrounding rock control, and provides a coal mine mining area main roadway advance area fracturing stress control method which comprises the steps that the whole mining area is divided into a plurality of working faces; arranging a plurality of drill sites on a main roadway of the working face; a horizontal long-drill-hole hydraulic fracturing rock stratum technology is adopted, and advanced hydraulic fracturing treatment is conducted on the whole mining area at the preset mining stopping line position; according to the method, a plurality of drill sites are arranged in a main roadway, so that the whole mining area can be fully covered, no missing area is ensured, the operation site of a retracement roadway can be effectively avoided, the risk of operation in a high-stress area is reduced, and effective stress release can be performed on a rock stratum before coal mining through advanced hydraulic fracturing treatment; according to the method, stress concentration and accidents are reduced, the recovery rate of coal resources is increased, large-area fracturing treatment can be completed within a short time through the horizontal long-drill-hole hydraulic fracturing technology, and the construction efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of surrounding rock control of coal mine tunnels, and in particular to a method for controlling fracturing stress in an advanced area of ​​a large tunnel in a coal mine mining area. Background Art

[0002] In order to protect the stability of the surrounding rock of the large tunnels in the mining area, the measures taken are nothing more than explosive blasting or hydraulic pre-fracture. Usually, blasting or hydraulic fracturing operations are carried out in pre-excavated tunnels or existing tunnels. From the perspective of the working environment, it is relatively narrow and not conducive to operation, and the construction workers face safety risks.

[0003] In addition, the mechanism of mining damage in the main tunnels in the mining area has been clarified, namely, the transmission disturbance of the supporting pressure in front of the final mining line of the working face; based on this, the current main tunnel maintenance is only for a single working face, and the blasting or hydraulic fracturing cutting method is used on the stopped mining face to reduce the concentration of the advance supporting pressure, which is based on the consideration of a single working face; and the mining area may deploy dozens of working faces for mining, so such operation for each working face is quite cumbersome, and the protective coal pillar area of ​​the reserved section has not been depressurized, which may cause local sections of the main tunnels in the mining area to still be affected by mining stress and cause deformation and damage.

[0004] In view of this, the present invention is based on the overall consideration of the entire mining area, based on the mining concept of first treatment and then recovery, and with the help of regional horizontal long borehole hydraulic fracturing technology, it can be carried out in advance after the mining area is deployed and formed, and then the working face can be recovered, without leaving any dead ends and blind spots, ensuring the safety and stability of the surrounding rock of the entire mining area's main tunnels. Summary of the invention

[0005] The present invention provides a method for controlling fracturing stress in the advance area of ​​the main tunnel in a coal mine mining area, which is used to solve the problem of low maintenance efficiency and poor effect of the main tunnel in the prior art. After the mining area is deployed and formed, fracturing treatment can be carried out in advance and then the working face can be mined again without leaving any dead angles and blind spots, thereby ensuring the safety and stability of the surrounding rock of the main tunnel in the entire mining area.

[0006] The present invention provides a method for controlling fracturing stress in an advanced area of ​​a large tunnel in a coal mining area, comprising: Divide the entire mining area into several working faces; A plurality of drilling sites are arranged in the main tunnel of the working face; The horizontal long-borehole hydraulic fracturing rock formation technology is used to carry out advanced hydraulic fracturing treatment at the preset stop-production line position in the entire mining area.

[0007] The method for controlling fracturing stress in the advanced area of ​​a main tunnel in a coal mining area provided by the present invention also includes: Determine the fracture layer; The drilling rig is used to drill into the predetermined borehole. After the drilling is completed, the horizontal long-hole hydraulic fracturing equipment is used to carry out fracturing operations to complete the fracturing construction operations in all drilling sites.

[0008] According to the method for controlling fracturing stress in the advanced area of ​​a large tunnel in a coal mining area provided by the present invention, the length L of the horizontal long borehole is less than 500 meters.

[0009] According to the method for controlling fracturing stress in the advanced area of ​​a large tunnel in a coal mine mining area provided by the present invention, the number n of drilling sites is determined according to the extension length B of the entire mining area and the length L of the horizontal long borehole, and the number n of drilling sites = B / L.

[0010] According to the method for controlling fracturing stress in the advanced area of ​​a large tunnel in a coal mining area provided by the present invention, the fracturing layer is mainly determined based on the key layer theory, m key layers are distributed in the fracture zone, and the number of horizontal fracturing holes is m.

[0011] According to the method for controlling fracturing stress in the advance area of ​​the main tunnel in a coal mine mining area provided by the present invention, the main tunnel includes a belt tunnel, a return air tunnel and a track tunnel. The belt tunnel, the return air tunnel and the track tunnel are arranged in sequence at the front end of the protective coal pillar, and two adjacent tunnels are separated by a coal pillar wall.

[0012] According to the method for controlling fracturing stress in the advanced area of ​​a main tunnel in a coal mining area provided by the present invention, gas blowout prevention treatment is adopted before drilling construction.

[0013] According to the method for controlling fracturing stress in the advanced area of ​​the main tunnel in a coal mining area provided by the present invention, a backward staged fracturing method is adopted, with a stage spacing of 9 to 15 m, and the hard rock formation in the bend section of the borehole is also fractured.

[0014] According to the method for controlling fracturing stress in the advanced area of ​​a large tunnel in a coal mining area provided by the present invention, a flow meter is used to monitor the flow rate and the amount of water injected during the fracturing process, and water discharge from long boreholes and surrounding roofs is observed at the same time, and the fracturing time is not less than 30 minutes.

[0015] According to the method for controlling fracturing stress in the advanced area of ​​a large tunnel in a coal mining area provided by the present invention, the distance between two adjacent working faces is 20-30m.

[0016] The present invention provides a method for controlling fracturing stress in an advanced area of ​​a large tunnel in a coal mining area, comprising: The entire mining area is divided into several working faces; multiple drilling sites are set up in the main lanes of the working faces; the horizontal long-bore hydraulic fracturing rock formation technology is used to perform advanced hydraulic fracturing treatment on the entire mining area at the preset stop line position; the present invention can achieve comprehensive coverage of the entire mining area by setting up multiple drilling sites in the main lanes, ensuring that there are no missed areas, and can effectively avoid the retreat tunnel operation site, reduce the risk of operating in high-stress areas, and through advanced hydraulic fracturing treatment, the rock formation can be effectively released from stress before coal mining, creating good geological conditions for subsequent coal mining operations, reducing stress concentration and accidents, and improving the recovery rate of coal resources; the horizontal long-bore hydraulic fracturing technology can complete large-area fracturing treatment in a relatively short time, thereby improving construction efficiency. Since the drilling site is set up in the main lane, continuous operation can be achieved, avoiding the time loss of frequent relocation of drilling rigs and equipment, and improving overall work efficiency.

[0017] The present invention is based on the concept of first treatment and then recovery, and with the help of horizontal long borehole hydraulic fracturing rock formation technology, it achieves a safer and more efficient way of avoiding the withdrawal tunnel operation site, and covers the entire extended length of the mining area without leaving any blind spots and dead ends, making the treatment more effective and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a layout diagram of a working surface provided by an embodiment of the present invention.

[0020] Figure 2 It is a schematic diagram of the overburden structure and stress distribution in front of the stop mining line of the working face before top cutting provided by an embodiment of the present invention.

[0021] Figure 3 It is a schematic diagram of the overburden structure and stress distribution in front of the stop-mining line of the working face after top cutting provided by an embodiment of the present invention.

[0022] Figure 4 It is a schematic diagram of the distribution of rock formations during drilling and fracturing provided by an embodiment of the present invention.

[0023] Reference numerals: 1. Drilling site; 2. Stop mining line; 3. Horizontal long borehole; 4. Working face; 5. Protective coal pillar; 6. Main tunnel; 7. Overlying rock strata; 8. Inclined section; 9. Stop mining face. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Combine the following Figure 1-Figure 4 The present invention describes a method for controlling fracturing stress in an advance area of ​​a large tunnel in a coal mining area.

[0026] The coal mining roadway in the mining area includes a protective coal pillar 5 and a plurality of roadways, each of which is arranged at the front end of the protective coal pillar 5, and a stop mining face 9 is provided at the rear end of the protective coal pillar 5. Figure 1 As shown, the large tunnel 6 described in this embodiment includes a belt tunnel, a return air tunnel and a track tunnel. The belt tunnel, the return air tunnel and the track tunnel are arranged in sequence at the front end of the protective coal pillar 5, and two adjacent tunnels are separated by a coal pillar wall. The coal pillar wall on the side of the tunnel and the supporting structure on the top together constitute the tunnel surrounding rock.

[0027] The large tunnel 6 of this embodiment is damaged by mining stress in the coal mining tunnel area, which leads to a significant reduction in the stability of the tunnel surrounding rock, resulting in a serious risk of roof collapse. It is preferred that the thickness of the protective coal pillar 5 is not less than the thickness of the coal pillar wall, so that the tunnel is as far away from the stop mining face 9 as possible, thereby helping to reduce the destructiveness of mining stress.

[0028] This embodiment provides a method for controlling fracturing stress in an advanced area of ​​a main tunnel in a coal mining area, comprising: Step 1: Divide the entire mining area into several working faces4.

[0029] Step 2: Set up multiple drilling sites 1 in the main tunnel 6 of the working face 4.

[0030] Step 3: Use the horizontal long borehole 3 hydraulic fracturing rock formation technology to perform advanced hydraulic fracturing treatment on the entire mining area at the preset stop production line 2 position.

[0031] The present invention is based on the concept of first governance and then recovery, and is based on the idea of ​​comprehensively considering the governance of the entire mining area. Therefore, the governance is more advanced. With the help of horizontal long drilling 3 hydraulic fracturing rock formation technology, it is safer and more efficient to avoid the withdrawal tunnel operation site, and it covers the entire extended length of the mining area without leaving any blind spots and dead ends, and the governance is more effective and efficient.

[0032] Preferably, the length L of the horizontal long borehole 3 is less than 500 meters.

[0033] The number n of the drilling sites 1 is determined according to the extension length B of the entire mining area and the length L of the horizontal long borehole 3 , and the number n of the drilling sites 1 = B / L.

[0034] This embodiment also includes: Step 4: Determine the fracturing layer. The fracturing layer is mainly determined based on the key layer theory. There are m key layers distributed in the fracture zone, and the number of horizontal fracturing holes is m.

[0035] The key layer refers to the rock layer that plays a decisive role in all or part of the rock mass movement when there are multiple hard rock layers in the overlying rock layer 7 of the mining area. These key layers play an important controlling role in the rock mass movement. Their fracture, deformation and movement laws have an important influence on the mining pressure, rock movement and surface subsidence in the mining area.

[0036] Step 5: Drill into the predetermined borehole through the drilling rig, and after the drilling is completed, use the horizontal long borehole 3 hydraulic fracturing equipment to perform fracturing operations to complete the fracturing construction operations of all drilling sites 1.

[0037] The horizontal long borehole 3 hydraulic fracturing rock formation technology in step 3 mainly includes the following steps: Step 31: A test borehole is formed by drilling a hole into the overlying rock 7 of the stop-production line 2 through a geological drill; the arrangement height of the horizontal long borehole 3 in the vertical direction is determined according to the lithology, thickness, strength and other parameters of the overlying rock 7 above the stop-production line 2. Therefore, before drilling, it is necessary to drill a test borehole into the overlying rock 7 of the stop-production line 2 to form a test borehole, and the angle between the test borehole and the top plate of the tunnel is determined according to actual needs.

[0038] Step 32: The overburden stratum 7 is measured for lithology, thickness and strength through test drilling to determine the vertical height of the horizontal long borehole 3; the fractures generated by the fracturing are distributed as evenly and well developed as possible to ensure that the overburden hard and stable stratum is effectively weakened. Of course, the content of the measurement is not limited to this, and other parameters can also be measured.

[0039] like Figure 4 As shown, m key layers are distributed in the fracture zone, and a directional drilling rig is used to drill holes in the overlying rock layer 7 to form m horizontal long boreholes 3.

[0040] Step 33: Use a directional drill to drill through the rock formation to the overburden stratum 7 to form at least one horizontal long borehole 3; the number of horizontal long boreholes 3 can be one, or two or more, which is estimated and determined based on the lithology, thickness, strength, etc. of the overburden stratum 7. Since the borehole is drilled from the drilling site 1 in the main tunnel 6 to the overburden stratum 7 above the stop-production line 2, the drilling process is divided into a deflection section 8 and a horizontal section of the horizontal long borehole 3. The deflection section 8 is located between the drilling site 1 and the overburden stratum, and is an arc-shaped trajectory that climbs upward. The deflection section 8 is used to adjust the orientation of the borehole so that the borehole enters the fracturing layer (i.e., the stable rock stratum) at a suitable angle, so that long-distance drilling and pressure relief can be achieved, and construction can be started before the working face 4 is mined to the stop-production line 2.

[0041] In this embodiment, step 33 includes: drilling a hole into the overlying rock stratum 7 through the rock stratum according to a predetermined trajectory using a directional drill to form an inclined section 8, the initial aperture of the inclined section 8 is 120 mm, and a smaller aperture can improve the drilling efficiency; expanding the hole in the inclined section 8 so that the aperture of the inclined section 8 reaches a predetermined size. The purpose of expanding the hole is to increase the aperture of the inclined section 8 so that it meets the requirements of the construction design and facilitates the subsequent installation of the casing. The predetermined size is 203 mm, which is specifically determined according to the construction design requirements; drilling a hole into the stable rock stratum of the overlying rock stratum 7 through the rock stratum using a directional drill from the bottom of the hole in the inclined section 8 in a horizontal direction to form a horizontal section. The aperture of the horizontal section is the same as the initial aperture of the inclined section 8, both of which are 120 mm.

[0042] It should be noted that gas blowout prevention treatment is carried out before drilling construction in order to prevent gas from blowing out, reduce the risk of gas explosion, and prevent gas and rock chips from entering the equipment, thereby extending the service life of the equipment.

[0043] Specifically, a wired measurement while drilling system with cable drill rod and drilling tools was used, and a pilot hole was constructed using directional drilling technology. The drilling tools used were Φ120mm drill bit + Φ89mm bottom hole motor with spiral groove + Φ89mm non-magnetic joint + Φ89mm measuring probe + Φ89mm upper non-magnetic drill rod with spiral groove + Φ89mm cable drill rod. Adjust the angle and fix the drilling rig according to the construction design requirements → Φ120mm drill bit to construct 18m → Φ153mm drill bit to expand the hole 18m → Φ203mm drill bit to expand the hole 18m → 6-inch sealing casing to seal the hole 18m → install the "drilling and pumping" anti-gas spray hole collection device → Φ120mm drill bit to construct to the designed depth → wash the hole / pull out the drill rod → seal the hole → connect to the centralized water discharger through the buried wire pipe with flange → clean up the site.

[0044] Among them, the sealing length is 18m, and it is connected by a steel pipe with an inner diameter of Φ153mm and the female buckle faces outward. A 5-inch flange is put on, and it is inserted into the hole in turn and tied with a grouting bag. 150-200mm is reserved for the hole opening. Two plugs and one injection are used to seal the hole with pressure grouting. Special cement-based grouting sealing materials are used to seal the hole with pneumatic pressure grouting. The sealing pressure is not less than 1.6MPa.

[0045] The normal drilling hole diameter is Φ120mm. Gas blowout prevention measures must be taken before drilling construction. Before construction, the negative pressure port of the four-way is connected to the 4-inch flange on the top of the first gas-water-slag separator with a 4-inch buried wire pipe, and the four-way drainage and slag discharge port is connected to the 4-inch flange on the side of the first gas-water-slag separator with a 4-inch buried wire pipe; the first gas-water-slag separator must be connected in series with two gas-water-slag separators, and the three gas-water-slag separators are connected to the gas pipeline with a negative pressure trip respectively. The 4-inch flanges on the top of the first and third gas-water-slag separators are connected to the buffer bag, and the bag specifications are: 3m long and 1m in diameter. The gas-water-slag and negative pressure are connected by 4-inch buried wire pipes, and all connections must be padded and tightened with screws; the three gas-water-slag separators must be placed from high to low in sequence, and the slag discharge at the water outlet must be normal.

[0046] Step 34: Fracturing is performed in the directional long borehole by means of a fracturing device; the purpose of fracturing the horizontal long borehole 3 is to form many cracks in the overburden stratum 7, so that the hard and stable overburden stratum 7 near the stop production line 2 is weakened.

[0047] Furthermore, the reverse staged fracturing method is adopted, and the stage spacing of 9 to 15m is adjusted according to the sealing conditions in the hole. The hard rock formations in the bend section of the borehole are also fractured.

[0048] It should be noted that the backward staged fracturing method starts from the end of the horizontal section of the horizontal long borehole 3, and performs fracturing operations section by section towards the hole mouth. After each small section is fractured, it moves to the next small section for fracturing. This method ensures that each small section can be fully fractured and transformed while avoiding the impact on the already fractured section.

[0049] Specifically, step 34 includes: pushing the sealer of the fracturing equipment into the bottom of the hole of the horizontal section. Since the hole wall of the horizontal section is damaged after fracturing, fracturing is started from the bottom of the hole of the horizontal section. After one section of fracturing is completed, it moves a distance toward the hole mouth and then performs the next section of fracturing. This fracturing method effectively avoids the risk of the fracturing equipment being stuck and improves the safety of construction.

[0050] By injecting high-pressure water into the sealer, the sealer expands in the radial direction after the injection of high-pressure water, forming a sealing section in the horizontal section, and the sealing section is separated from other sections of the horizontal section to form a closed area; injecting high-pressure water into the sealing section through the water outlet of the sealer, the high-pressure water will generate huge pressure on the hole wall, causing a large number of cracks in the hole wall of the sealing section. The greater the water pressure, the wider the cracks are, and the farther they extend to the surroundings; the sealer is depressurized. After the sealer is depressurized, the outer diameter of the sealer is reduced, and the sealer is moved toward the hole mouth by a predetermined distance so as to perform fracturing on the next sealing section. The specific length of the predetermined distance is determined according to the length of the sealing section.

[0051] like Figure 2 As shown in the figure, according to the stress change of the overburden strata at the top of the mining area, the mining area is divided into stress change zone I in front of the working face 4, top control zone II of the working face 4, loose zone III of the caving rock, gradual compression zone IV of the caving rock and compaction zone V of the caving rock from front to back, where rh represents the original rock stress, krh represents the leading vertical stress in front of the working face 4, and p represents the pressure of the overburden strata; the coal mining roadway area is located in the stress change zone I in front of the working face 4 as a whole, the stop mining face 9 and the support area are located in the top control zone II of the working face 4, and the goaf area is located in the loose zone III of the caving rock, the gradual compression zone IV of the caving rock and the compaction zone V of the caving rock from front to back; according to Figure 2 From the stress changes shown, we can see that Figure 2 The front end of the middle coal mining roadway is in the original stress zone A, the rear end of the coal mining roadway is in the stress increase zone B, the stop mining face 9, the support area, and the front and middle ends of the goaf are all in the stress reduction zone C, and the rear end of the goaf is in the stress stability zone D. It can be seen that the autonomous fall of the overburden stratum 7 on the stop mining face 9 will produce stress effects on the rear end of the coal mining roadway and the front and even middle ends of the goaf on both sides of the stop mining face 9. After the hydraulic support, coal mining machine and scraper conveyor are evacuated, the overburden stratum above the stop mining face 9 sinks due to the absence of any support in the support area, and produces stress on the overburden stratum 7 on the coal mining roadway, so that the rear end of the stress change zone I in front of the working face 4 where the coal mining roadway is located produces a stress increase zone B, and the stress change of the stress increase zone B increases sharply, which will have a great destructive force on the protective coal pillar 5 and have a great adverse effect on the stability of the roadway surrounding rock near the protective coal pillar 5.

[0052] like Figure 3As shown, after the hydraulic supports, coal mining machines and scraper conveyors are evacuated from the stop mining face 9, there is a vacant area at the rear end of the stop mining face 9, which is the support area where the original hydraulic supports, coal mining machines and scraper conveyors are located; at this time, there is no supporting force at the bottom of the overlying rock stratum 7 on the stop mining face 9, so the overlying rock stratum 7 on the stop mining face 9 falls autonomously under the action of gravity to the support area between the stop mining face and the goaf; the overlying rock stratum is covered with a rock wall top, and when the overlying rock stratum 7 on the stop mining face 9 falls under the action of its own weight, the overlying rock stratum 7 on the stop mining face 9 is separated from the rock wall top, and the vacant area is provided for the overlying rock stratum. It provides falling space. At the same time, the overlying rock stratum 7 in the stopped mining area is completely disconnected from the overlying rock stratum 7 in the coal mining roadway. During and after its autonomous falling, the overlying rock stratum will not cause mining pressure to the coal mining roadway area and goaf area on both sides and the overlying rock stratum 7 in these two areas, thereby effectively reducing the stress concentration value of the protective coal pillar in the coal mining roadway area, thereby playing a very good protective role in the structural stability of the roadway surrounding rock, i.e., the coal pillar wall and the supporting structure at the top of the roadway, effectively avoiding repeated deformation and damage of the roadway, ensuring the long-term safe use of the permanent roadway of the coal mine, and ensuring safe and efficient production of the coal mine.

[0053] Figure 3 The front end of the middle coal mining roadway is in the original stress zone A, the rear end of the coal mining roadway is in the stress increase zone B, the stop mining face 9, the support area, and the front and middle ends of the goaf are all in the stress reduction zone C, and the rear end of the goaf is in the stress stability zone D, rh represents the original rock stress, krh represents the leading vertical stress in front of the working face 4, and p represents the pressure of the overburden. It can be seen that the autonomous fall of the overburden 7 on the stop mining face 9 will have a stress impact on the rear end of the coal mining roadway and the front and even the middle end of the goaf on both sides of the stop mining face 9. According to Figure 3 From the stress changes in the figure, it can be seen that since the overlying rock stratum 7 above the stopped mining face 9 is disconnected from the overlying rock stratum above the coal mining roadway area, when the overlying rock stratum 7 falls autonomously in the empty top area of ​​the working face 4 where the stopped mining face 9 is located, the stress change zone I in front of the working face 4 is not affected by too much stress.

[0054] Although Figure 3 As shown in FIG. 4 , there is also a stress increase area B at the rear end of the stress change area Ⅰ in front of the working face 4, but it is relatively Figure 2 and Figure 3 It can be seen that due to Figure 3 The protection method described in this embodiment is adopted. Figure 3 The peak stress change in the stress-increased area B shown in FIG is significantly lower than Figure 2 The peak stress change in the stress-increased region B shown in FIG. Figure 3 The stress variation trend in the stress-increased area B is shown in Figure 2. Figure 2 The stress variation trend in the stress increased area B shown is more gentle.

[0055] Therefore, the use of this protection method can effectively reduce the stress concentration in the overburden above the coal mining area, alleviate the problem of increased stress in front of the working face, and especially can significantly alleviate the pressure on the top of the protective coal pillar 5, slow down and prevent the protective coal pillar from being damaged by falling rocks, and can further play a positive protective role in the structural stability of the surrounding rock of each tunnel in the coal mining area.

[0056] In this embodiment, the water pressure will drop after the initial cracks are initiated during the fracturing process, and then enter the pressure maintenance stage. In this stage, the cracks expand while new cracks are generated. A flow meter is used to monitor the flow rate and the amount of water injected to ensure that the roof rock formation is fully cracked and softened. The water output of the long borehole and the surrounding roof is observed during the fracturing process. The fracturing time is generally not less than 30 minutes.

[0057] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling fracturing stress in the advanced area of ​​a large tunnel in a coal mining area, characterized in that: include: Divide the entire mining area into several working faces (4); A plurality of drilling sites (1) are arranged in the main tunnel (6) of the working face (4); The hydraulic fracturing rock formation technology of a horizontal long borehole (3) is used to perform an advanced hydraulic fracturing treatment on the entire mining area at a preset stop-production line (2); wherein the length L of the horizontal long borehole (3) is less than 500 meters; the number n of the drilling sites (1) is determined according to the extension length B of the entire mining area and the length L of the horizontal long borehole (3), and the number n of the drilling sites (1) = B / L.

2. The method for controlling fracturing stress in the advanced area of ​​a large tunnel in a coal mining area according to claim 1 is characterized in that: Also includes: Determine the fracture layer; The predetermined borehole is drilled by a drilling rig, and after the drilling is completed, a hydraulic fracturing operation is performed using a horizontal long borehole (3) hydraulic fracturing equipment set to complete the fracturing operation of all drilling sites (1).

3. The method for controlling fracturing stress in the advanced area of ​​a large tunnel in a coal mining area according to claim 2, characterized in that: The fracturing layer position is mainly determined based on the key layer theory. There are m key layers distributed in the fracture zone, and the number of horizontal long boreholes (3) is m.

4. The method for controlling fracturing stress in the advanced area of ​​a large tunnel in a coal mining area according to claim 1, characterized in that: The large tunnel (6) comprises a belt tunnel, a return air tunnel and a track tunnel. The belt tunnel, the return air tunnel and the track tunnel are arranged in sequence at the front end of the protective coal pillar (5), and two adjacent tunnels are separated by a coal pillar wall.

5. The method for controlling fracturing stress in the advanced area of ​​a large tunnel in a coal mining area according to claim 2, characterized in that: Gas blowout prevention treatment should be carried out before drilling construction.

6. The method for controlling fracturing stress in the advanced area of ​​a large tunnel in a coal mining area according to claim 1, characterized in that: The reverse staged fracturing method is adopted, with the stage spacing of 9 to 15m, and the hard rock formations in the bend section of the borehole are also fractured.

7. The method for controlling fracturing stress in the advanced area of ​​a large tunnel in a coal mining area according to claim 6, characterized in that: During the fracturing process, flow meters are used to monitor the flow rate and the amount of water injected, and the water output from the long boreholes and the surrounding roof is observed. The fracturing time is no less than 30 minutes.

8. The method for controlling fracturing stress in the advanced area of ​​a large tunnel in a coal mining area according to claim 6, characterized in that: The distance between two adjacent working surfaces (4) is 20-30 m.

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