A method for coordinating coal seam floor blasting roadway protection with efficient gas extraction

Abstract

A method for coordinating coal seam floor blasting roadway protection and efficient gas extraction includes the following steps: S1: Determine the lithology of the coal seam floor and the target decompression coal seam; S2: Prepare deep-hole pre-splitting blasting equipment for the coal seam; S3: Determine the blasting layer position and thickness of the coal seam floor; S4: Arrange drilling sites in the coal seam floor rock roadway: drill blasting holes and extraction holes; S5: Deliver explosives from the blasting holes to the designed blasting layer position of the coal seam floor; S6: Perform conventional stemming and sealing of the holes, and detonate after confirming safety; S7: Seal the blasting holes again; S8: Repeat the above steps, connecting the blasting holes and extraction holes of each drilling site, and begin gas extraction from the mined coal seam. This invention forms a coal seam floor blasting layer in the coal seam floor through the fracture guidance and compensation effect of the blasting holes and coal seam cross-layer drainage holes, thereby increasing the permeability of the coal seam and improving the gas extraction effect, while weakening the impact of rock pressure and high ground stress on the coal seam floor roadway.

Description

Technical Field

[0001] This invention relates to the field of coal seam permeability enhancement and rockburst prevention, specifically to a method for the coordinated construction of coal seam floor blasting protection and efficient gas extraction. Background Technology

[0002] The vast majority of coal mines in my country are high-gas mines, with high original coal seam gas content and poor permeability accounting for over 80% of the total. This situation severely affects gas drainage efficiency, hindering both the rate and volume of gas extraction. With increasing mining depth, high ground stress leads to more significant closure of fractures in the coal seam, making it difficult to maintain a complete drainage cycle. The increased depth of coal seams presents challenges such as significantly higher underground rockburst pressure, more complex geological structures, poor coal seam permeability, and low gas drainage efficiency, all of which urgently need to be addressed. Traditional permeability enhancement, gas drainage, or pressure relief technologies are no longer adequate for the high-stress underground environment where fractures are damaged.

[0003] Currently, the main coal seam permeability enhancement methods tested and applied in my country include hydraulic fracturing, hydraulic slotting, loosening blasting, deep-hole pre-splitting blasting, rotating water jet enlargement, high-pressure abrasive jet slotting, and composite perforation. These coal seam permeability enhancement technologies use specific processes to disrupt the original structure of the coal seam to generate cracks (gaps). However, the mechanical properties of coal determine that the cracks (gaps) generated in the coal seam are unstable and gradually close under the action of self-weight stress. The cracks are short and wide, with a small permeability enhancement range, and cannot alleviate the safety hazards caused by rockbursts in the rock strata, coal seam floor, and roadways. Therefore, there is still considerable room for improvement in existing coal seam permeability enhancement technologies and rockburst prevention technologies.

[0004] To address the issues of increased permeability and rock bursts in low-permeability, high-gas coal seams during deep mining, a prevention and control technology that can solve these comprehensive problems is urgently needed. To this end, we propose a collaborative construction method for coal seam floor blasting protection and efficient gas extraction. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the coordinated construction of coal seam floor blasting roadway protection and efficient gas extraction. This invention forms a coal seam floor blasting layer in the coal seam floor through the fracture guidance and compensation effect of blasting holes and coal seam cross-layer drainage holes, which loosens the coal and rock, increases the permeability of the coal seam, and improves the gas extraction effect. At the same time, the generation of the coal seam floor blasting layer in the coal seam floor below the target depressurized coal seam and above the coal seam floor rock roadway can weaken the impact of rock pressure and high ground stress on the coal seam floor rock roadway.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for coordinating coal seam floor blasting roadway protection with efficient gas extraction includes the following steps:

[0008] S1: Collect coal mine geological data, analyze the geological conditions of the coal seam floor above the coal seam floor roadway, and determine the lithology of the coal seam floor and the target unloading coal seam;

[0009] S2: Preparation of equipment for deep-hole pre-splitting blasting of coal seams;

[0010] S3: Determine the position and thickness of the blasting layer at the bottom of the coal seam based on the thickness of the target decompression coal seam;

[0011] S4: Arrange drilling sites in coal seam floor rock roadways: drill blasting holes and drainage holes;

[0012] S5: Send the special explosive tube from the blast hole to the designed blasting layer of the coal seam floor;

[0013] S6: Perform routine stemming and sealing of the borehole, and detonate after confirming safety;

[0014] S7: Seal the blast hole again and perform conventional gas drainage through the drainage hole;

[0015] S8: Repeat the above steps to connect the blasting holes and drainage holes in each drilling site and begin gas extraction from the coal seam.

[0016] The lithology of the coal seam floor in step S1 is a necessary condition for determining whether the coal seam floor blasting roadway protection and efficient gas extraction co-construction method is suitable. The hardness of the coal seam floor has a significant impact on the deep-hole pre-splitting blasting effect: the higher the hardness of the coal seam floor, the more fully the fractures develop; conversely, the lower the hardness of the coal seam floor, the easier the rock mass is to break. Under the action of the blast stress wave, the crushed ring formed by the extremely fractured rock mass around the blast hole will reduce the blast impact in a buffering manner, thus affecting the further development of fractures. Therefore, the higher the hardness of the coal seam floor, the more suitable it is for the coal seam floor blasting roadway protection and efficient gas extraction co-construction method. The specific lithological characteristics of the coal seam floor are shown in the table below:

[0017]

[0018] As shown in the table above, if the coal seam floor is sandstone, which is stable and brittle, the radial cracks generated by the explosion stress wave and the cracks expanded by the wedge action of the gas are stable and not easily deformed. The cracks are characterized by being narrow and long, which is suitable for the co-construction method of blasting the coal seam floor for roadway protection and efficient gas extraction.

[0019] The equipment required for deep-hole pre-splitting blasting of coal seams in step S2 includes: special explosive tubes, blasting rubber wire, electric detonators, special blasting mud bags, one sealing device, one high-power blasting device, and blasting wire.

[0020] Among them, the special explosive tubes are made underground in the coal mine; the length of the blasting rubber line is at least 300 meters; each blasting hole is equipped with two millisecond delay electric detonators; the special blasting mud bag is filled with blasting mud with a particle size smaller than the moisture content and a certain degree of fluidity; the sealing device is equipped with one rubber tube and 30 probe tubes; the blasting main line is laid from the detonation point to the blasting point.

[0021] The technical performance indicators of the special medicine tubing are shown in the table below:

[0022]

[0023] The specific method for determining the thickness of the blasting layer at the bottom of the coal seam in step S3 is as follows: referring to the provision in the "Detailed Rules for the Prevention and Control of Coal and Gas Outbursts" that "the maximum expansion deformation after the protective layer is mined should be greater than 3‰", the thickness of the blasting layer at the bottom of the coal seam is designed, that is, the length of the charging section of the blasting hole, so that the expansion deformation of the top plate of the coal seam that is furthest from the blasting layer at the bottom of the coal seam is greater than 3‰. Since the self-weight of the top plate of the coal seam is the least compared to the coal body below it, and due to the attenuation of the blasting wave and the explosion stress wave during the propagation process, the minimum deformation occurs at the top plate of the coal seam. This ensures that the overall deformation of the coal seam meets the requirement that the deformation should be greater than 3‰.

[0024] Among them, a displacement monitoring instrument is installed on the coal seam roof to obtain the displacement of the coal seam roof, ensuring that the thickness design of the blasting layer of the coal seam floor can enable the expansion deformation displacement of the coal seam roof to reach 3‰ of the coal seam thickness.

[0025] Step S4 is as follows: Determine the radius of the fracture zone of the surrounding rock of the blasting hole based on the actual lithology of the coal seam floor and the parameters of the explosives used. Set up the drilling site in the rock roadway of the coal seam floor. Drill multiple blasting holes and drainage holes alternately to the left and right on the roof of the rock roadway towards the target pressure-relief coal seam. The blasting holes and drainage holes are arranged radially. The diameter of the blasting holes is 50-100mm, and they are drilled to 1-2m below the coal seam. The diameter of the drainage holes is 75-120mm, and the drainage holes are drilled through the target pressure-relief coal seam to 1-3m inside the roof of the coal seam. The outermost sides of both sides of the drilling site are designed as drainage holes. Based on the range of the fracture zone caused by the impact of blasting on the rock strata, the fracture zone of the blasting layer of the coal seam floor is utilized to the maximum extent. The distance between adjacent blasting holes and drainage holes extending to the coal seam floor is set to 4-5m.

[0026] Step S5 is as follows: Before loading the explosive, a probe tube is used to probe the borehole. To avoid borehole collapse, the special explosive tubes are immediately inserted into the borehole one by one according to their own threads as soon as the probe tube is pulled out. For each borehole, two millisecond electric detonators and rubber wire for blasting are used to make two blast heads, which are fixed with tape to prevent friction between the tube and the borehole wall from causing the detonator lead wire to fall off the main wire, resulting in detonator open circuit and short circuit. After the special explosive tubes are sent from the blast hole to the designed layer of the coal seam floor blasting layer, it is ensured that the explosive loading section is aligned with the preset coal seam floor blasting layer to allow the coal body fractures to develop fully. Based on the coal seam floor blasting layer position and thickness determined in step S3, a sufficient coal seam floor blasting layer thickness is designed to determine the explosive loading length. The thicker the target depressurized coal seam, the longer the explosive loading section. The position and length of the explosive loading section can control the coal seam floor blasting layer position and thickness.

[0027] Step S6 is as follows: The special blasting mud bag is loaded from the inside of the blast hole outward from the end of the explosive loading section to the blast hole opening to form a sealing section. The blasting line is connected to the electric detonator and the high-power blasting device. After confirming safety, the blasting is initiated. After the blasting, it is checked whether there is rock debris ejected from the opening of the adjacent extraction hole to ensure that the blasting hole and the extraction hole are connected and form a stable gas transport channel.

[0028] Step S7 specifically involves: using a sealing device to seal the blasting hole again after the blasting is completed, to prevent gas from connecting to the coal seam floor rock roadway through the blasting hole after the drainage hole is connected to negative pressure, thus ensuring the airtightness of the subsequent gas drainage circuit. The drainage hole perforated pipe is used for conventional gas drainage through the coal seam pressure relief fracture and the coal seam floor blasting fracture.

[0029] This invention has outstanding substantive features and significant progress compared to the prior art. Specifically, this invention determines whether the coal seam floor blasting roadway protection and efficient gas extraction co-construction method is suitable based on the lithology of the coal seam floor: if the coal seam floor is sandstone, the lithology is stable and brittle, the radial cracks generated by the explosion stress wave and the cracks expanded by the wedge action of the gas are stable and not easily deformed, and the cracks are characterized by being narrow and long, making the coal seam floor blasting roadway protection and efficient gas extraction co-construction method suitable.

[0030] This invention selects the charging section of the blast hole in the coal seam floor, which not only ensures the integrity of the coal seam roof support, but also forms a coal seam floor blasting layer below the coal seam, which alleviates rock pressure and allows the coal seam and the coal seam floor to communicate vertically, increasing the migration channel of coal seam gas when it is extracted under negative pressure.

[0031] In order to ensure the full development of coal seam fractures, this invention requires selecting a sufficient thickness for the coal seam floor fracture based on the coal seam thickness; that is, the thicker the coal seam, the longer the explosive loading section. The position of the coal seam floor blasting layer is determined by the location of the explosive loading section of the blasting hole. This invention can generate a coal seam floor blasting layer in the coal seam floor below the target decompression coal seam and above the coal seam floor rock roadway, thereby reducing the impact of rock pressure and high ground stress on the coal seam floor rock roadway, improving the stability of the coal seam floor rock roadway, protecting the coal seam floor rock roadway, and ensuring mine production safety.

[0032] The invention designs drainage holes on the outermost sides of both the left and right sides of the drilling site, thereby ensuring that drainage holes on both sides of the blasting hole play a guiding role in the fracture.

[0033] This invention utilizes the energy of explosive explosions and the guiding and compensating effects of drainage holes to cause the fractures generated by the blasting of the coal seam floor to develop towards the drainage holes, forming a stable channel for gas migration. Moreover, after the pre-splitting blasting of the coal seam floor, a blasted coal seam floor layer is formed. The target depressurized coal seam is subjected to the disturbance of explosive stress and its own action, and breaks and settles downward to relieve pressure and generate fractures. Then, the drainage hole perforated pipe can extract gas through the depressurized fractures of the coal seam and the fractures of the rock strata. The gas migration path is increased, and the gas extraction effect is improved.

[0034] In summary, this invention forms a coal seam floor blasting layer in the coal seam floor through the fracture guidance and compensation effects of the coal seam floor blasting holes and coal seam cross-layer drainage holes. This loosens the coal and rock, increases the permeability of the coal seam, and improves the gas extraction effect. At the same time, the generation of the coal seam floor blasting layer in the coal seam floor below the target depressurized coal seam and above the coal seam floor rock roadway can weaken the impact of rock pressure and high ground stress on the coal seam floor rock roadway. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the deep-hole pre-splitting blasting construction of the coal seam floor according to the present invention.

[0036] Figure 2 This is a schematic diagram of the drilling layout for the coal seam floor rock tunnel of the present invention.

[0037] Figure 3 This is a schematic diagram of the fracture zone generated by adjacent blasting holes and extraction holes in this invention.

[0038] Figure 4 This is a schematic diagram of the explosive loading section of the blast hole in this invention. Detailed Implementation

[0039] The embodiments of the present invention are further described below with reference to the accompanying drawings.

[0040] like Figure 1-4 As shown, a method for coordinating coal seam floor blasting roadway protection with efficient gas extraction includes the following steps:

[0041] S1: Collect coal mine geological data, analyze the geological conditions of the coal seam floor above the coal seam floor roadway 1, and determine the lithology of the coal seam floor 2 and the target unloading coal seam 3.

[0042] S2: Preparation of equipment for deep-hole pre-splitting blasting of coal seams;

[0043] S3: Determine the position and thickness of the blasting layer 4 at the bottom of the coal seam based on the thickness of the target unloading coal seam 3.

[0044] S4: Arrange the drilling site in the coal seam bottom rock roadway 1: Drill blasting holes 5 and drainage holes 6;

[0045] S5: Send the explosive from the blasting hole 5 to the designed layer 4 of the coal seam floor blasting layer;

[0046] S6: Perform routine stemming and sealing of the borehole, and detonate after confirming safety;

[0047] S7: Seal the blast hole 5 again to prevent the gas extraction circuit from connecting with the coal seam floor rock roadway 1 through the blast hole 5, and perform conventional gas extraction through the extraction hole 6.

[0048] S8: Repeat the above steps to connect the blasting hole 5 and the drainage hole 6 in each drilling site to begin gas extraction from the coal seam.

[0049] The lithology of the coal seam floor 2 in step S1 is a necessary condition for determining whether the coal seam floor blasting roadway protection and efficient gas extraction co-construction method is suitable. The hardness of the coal seam floor 2 has a significant impact on the deep-hole pre-splitting blasting effect: the higher the hardness of the coal seam floor 2, the more fully the fractures develop; conversely, the lower the hardness of the coal seam floor 2, the easier the rock mass is to break. Under the action of the blast stress wave, the crushed ring formed by the extremely broken rock mass around the blast hole 5 will reduce the blasting impact in a buffering manner, thus affecting the further development of fractures. Therefore, the higher the hardness of the coal seam floor 2, the more suitable it is for the coal seam floor blasting roadway protection and efficient gas extraction co-construction method. The specific lithological characteristics of the coal seam floor 2 are shown in the table below:

[0050]

[0051] As shown in the table above, if the coal seam floor 2 is sandstone, which is stable and brittle, then the radial cracks generated by the explosion stress wave and the cracks expanded by the wedge action of the gas are stable and not easily deformed. The cracks are characterized by being narrow and long, which is suitable for the coal seam floor blasting roadway protection and efficient gas extraction co-construction method.

[0052] The equipment required for deep-hole pre-splitting blasting of coal seams in step S2 includes: special explosive tubes, blasting rubber wire, electric detonators, special blasting mud bags, one sealing device, one high-power blasting device, and blasting wire.

[0053] Among them, the special explosive tube is made underground in the coal mine; the length of the blasting rubber line is at least 300 meters; each blasting hole is equipped with two millisecond delay electric detonators; the special blasting mud bag is filled with blasting mud with a particle size smaller than the moisture content and a certain degree of fluidity; the sealing device is equipped with one rubber tube and 30 probe tubes; the blasting main line is laid from the detonation point to the blasting point.

[0054] The technical performance indicators of the special medicine tubing are shown in the table below:

[0055]

[0056] The specific method for determining the thickness of the coal seam floor blasting layer 4 in step S3 is as follows: referring to the provision in the "Detailed Rules for the Prevention and Control of Coal and Gas Outbursts" that "the maximum expansion deformation after the protective layer is mined should be greater than 3‰", the thickness of the coal seam floor blasting layer is designed, that is, the length of the charging section of the blasting hole 5, so that the expansion deformation of the coal seam roof 9, which is vertically farthest from the coal seam floor blasting layer, is greater than 3‰. Since the coal seam roof 9 is subjected to the least self-weight effect compared to the coal body below it, and due to the attenuation of the blasting wave and the explosion stress wave during the propagation process, the minimum deformation occurs at the coal seam roof 9. This ensures that the overall deformation of the coal seam meets the requirement that the deformation should be greater than 3‰.

[0057] Among them, a displacement monitoring instrument is installed on the coal seam roof 9 to obtain the displacement of the coal seam roof 9, ensuring that the thickness design of the blasting layer of the coal seam floor can enable the expansion deformation displacement of the coal seam roof 9 to reach 3‰ of the coal seam thickness.

[0058] Step S4 is as follows: Determine the radius of the fracture zone of the surrounding rock of the blasting hole 5 based on the actual lithology of the coal seam floor and the parameters of the explosives used. Set up a drilling site in the rock roadway 1 of the coal seam floor. On the roof 10 of the rock roadway, drill multiple blasting holes 5 and drainage holes 6 alternately upwards and to the left and right towards the target pressure-relief coal seam 3. The blasting holes 5 and drainage holes 6 are arranged radially. The diameter of the blasting holes 5 is 50-100mm, and they are drilled to 1-2m below the coal seam. The diameter of the drainage holes 6 is 75-120mm, and they are drilled through the target pressure-relief coal seam 3 to 1-3m inside the roof 9 of the coal seam. The outermost sides of both sides of the drilling site are designed as drainage holes 6. Based on the radiation range of the fracture zone generated by the impact of blasting on the rock strata, the fracture zone of the blasting layer of the coal seam floor is utilized to the maximum extent. The distance between adjacent blasting holes 5 and drainage holes 6 extending to the coal seam floor is set to 4-5m.

[0059] Step S5 is as follows: Before loading the explosive, a probe tube is used to probe the hole. To avoid hole collapse, the special explosive tubes are immediately inserted into the blasting hole 5 one by one according to their own threads as soon as the probe tube is pulled out. For each blasting hole, two millisecond electric detonators and rubber wire for blasting are used to make two blast heads, and they are fixed with tape to prevent the friction between the tube and the hole wall from causing the detonator lead wire to fall off the main wire, resulting in a detonator open circuit or short circuit. After the special explosive tubes are sent from the blasting hole to the designed layer position of the coal seam bottom blasting layer 4, it is ensured that the explosive loading section 7 is aligned with the preset coal seam bottom blasting layer 4. In order to fully develop the coal body fractures, the thickness of the coal seam bottom blasting layer 4 is designed according to the layer position and thickness of the coal seam bottom blasting layer 4 determined in step S3, thereby determining the charging length. The thicker the target depressurized coal seam 3, the longer the explosive loading section 7. The position and length of the explosive loading section 7 can control the layer position and thickness of the coal seam bottom blasting layer 4.

[0060] Step S6 is as follows: The special blasting mud bag is loaded from the inside of the blasting hole 5 outward from the end of the explosive loading section 7 to the opening of the blasting hole 5 to form the sealing section 8. The blasting wire is connected to the electric detonator and the high-power blasting device. After confirming safety, the blasting is initiated. After the blasting, it is checked whether there are rock fragments ejected from the opening of the adjacent extraction hole 6 to ensure that the blasting hole 5 and the extraction hole 6 are connected to form a stable gas transport channel.

[0061] Step S7 specifically involves: using a sealing device to seal the blasting hole 5 again after the blasting is completed, to prevent gas from connecting to the coal seam floor rock roadway 1 through the blasting hole 5 after the gas extraction hole 6 is connected to negative pressure, thus ensuring the airtightness of the subsequent gas extraction circuit. The gas extraction hole 6 is then used for conventional gas extraction through the coal seam pressure relief fracture and the blasting fracture of the coal seam floor 2.

[0062] This invention determines whether a coal seam floor blasting roadway protection and efficient gas extraction co-construction method is suitable based on the lithology of the coal seam floor: if the coal seam floor is sandstone, the lithology is stable and brittle, the radial cracks generated by the explosion stress wave and the cracks expanded by the wedge action of the gas are stable and not easily deformed, and the cracks are characterized by being narrow and long, making this coal seam floor blasting roadway protection and efficient gas extraction co-construction method suitable;

[0063] The present invention selects the charging section of the blast hole 5 at the bottom plate 2 of the coal seam, which not only ensures the integrity of the support of the top plate 9 of the coal seam, but also forms a blasting layer 4 of the bottom plate of the coal seam below the coal seam. This not only alleviates the rock pressure, but also enables communication between the coal seam and the bottom plate 2, increasing the migration channel of coal seam gas when it is extracted under negative pressure.

[0064] In order to ensure the full development of coal seam fractures, this invention requires selecting a sufficient fracture thickness of the coal seam floor 2 based on the coal seam thickness. That is, the thicker the coal seam, the longer the explosive loading section 7. The position of the coal seam floor blasting layer 4 is determined by the position of the explosive loading section of the blasting hole 5 (explanation: wherever the explosive is placed, that section will detonate, producing the coal seam floor blasting layer, so the position of the coal seam floor blasting layer is determined by the position of the loading section). This invention can generate the coal seam floor blasting layer 4 in the coal seam floor 2 below the target depressurized coal seam 3 and above the coal seam floor rock roadway 1, thereby reducing the impact of rock pressure and high ground stress on the coal seam floor rock roadway 1, improving the stability of the coal seam floor rock roadway 1, protecting the coal seam floor rock roadway 1, and ensuring mine production safety.

[0065] The present invention designs extraction holes 6 on the outermost sides of both the left and right sides of the drilling site, thereby ensuring that extraction holes 6 on both sides of the blasting hole 5 play a guiding role in the fracture.

[0066] This invention utilizes the energy of the explosive explosion and the guiding and compensating effect of the drainage hole 6 to cause the cracks generated by the blasting of the coal seam floor 2 to develop towards the drainage hole 6, forming a stable channel for gas migration. Moreover, after the pre-splitting blasting of the coal seam floor, a coal seam floor blasting layer 4 is formed. The target depressurized coal seam 3 is subjected to the disturbance of explosive stress and its own action, and breaks and settles downward to relieve pressure and generate cracks. Then, the drainage hole 6 can be used to extract gas through the depressurized cracks in the coal seam and the cracks in the rock strata. The gas migration path is increased, and the gas extraction effect is improved.

[0067] In summary, this invention forms a coal seam floor blasting layer 4 in the coal seam floor 2 through the fracture guidance and compensation effects of the blasting holes 5 and the coal seam cross-layer drainage holes 6. This loosens the coal and rock, increases the permeability of the coal seam, and improves the gas extraction effect. At the same time, the generation of the coal seam floor blasting layer 4 in the coal seam floor 2 below the target depressurized coal seam 3 and above the coal seam floor rock roadway 1 can weaken the impact of rock pressure and high ground stress on the coal seam floor rock roadway 1.

[0068] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A coal seam floor burst roadway protection and gas efficient extraction collaborative construction method, characterized in that: Specifically comprising the following steps: S1: collecting coal mine geological data, analyzing the geological conditions of the coal seam floor above the rock roadway of the coal seam floor, determining the lithology of the coal seam floor and the target pressure-relief coal seam; S2: coal seam deep hole pre-splitting blasting work equipment preparation; S3: determining the coal seam floor blasting layer position and the thickness of the coal seam floor blasting layer according to the thickness of the target pressure-relief coal seam; S4: arranging a drilling site in the coal seam floor rock roadway: drilling blasting holes and drainage holes; S5: sending special explosive pipes from the blasting holes to the designed position of the coal seam floor blasting layer; S6: performing conventional stemming hole sealing, and detonating after confirming safety; S7: sealing the blasting holes again to avoid the gas drainage circuit connecting the blasting holes and the coal seam floor rock roadway through the blasting holes, and performing conventional gas drainage in the drainage holes; S8: repeating the above steps to connect the blasting holes and the drainage holes of each drilling site, and starting to drain gas from the mining coal seam; Step S4 specifically comprises: determining the crack circle radius of the surrounding rock of the blasting hole according to the actual coal seam floor lithology and the parameters of the used explosive pipe, arranging a drilling site in the coal seam floor rock roadway, drilling multiple blasting holes and drainage holes alternately left and right on the roof of the rock roadway towards the target pressure-relief coal seam, and arranging the blasting holes and the drainage holes in a radial pattern, wherein the diameter of the blasting hole is 50-100 mm, the blasting hole is drilled 1-2 m below the coal seam, the diameter of the drainage hole is 75-120 mm, the drainage hole is drilled 1-3 m into the coal seam roof through the target pressure-relief coal seam, the outermost sides of the left and right sides of the drilling site are designed as drainage holes, and the distance between the adjacent blasting holes and the drainage holes extending to the coal seam floor is set to 4-5 m according to the crack zone range affected by the blasting impact of the rock stratum, so as to maximize the use of the crack zone of the coal seam floor blasting layer; Step S5 specifically comprises: before charging, a hole-probing pipe is used to probe the hole, and to avoid hole collapse, the special explosive pipe is immediately loaded into the blast hole one pipe after another according to its own threads when the hole-probing pipe is just probed out, two millisecond electric detonators and a gelatinous wire for blasting are used to make two heads for each blast hole, and adhesive tape is used to fix them to prevent the friction between the pipe and the hole wall from causing the detonator foot wire to fall off the bus, resulting in open circuit and short circuit of the detonator; after the special explosive pipe is sent from the blasting hole to the designed position of the coal seam floor blasting layer, the explosive charging section is aligned with the pre-set coal seam floor blasting layer to make the coal body cracks fully developed, the charging length is determined according to the coal seam floor blasting layer position and thickness determined in step S3, so that the thicker the target pressure-relief coal seam is, the longer the explosive charging section is, and the position and length of the explosive charging section can control the coal seam floor blasting layer position and thickness.

2. The coal seam floor burst for protecting the roadway and efficient gas extraction collaborative construction method according to claim 1, characterized in that: The coal seam floor lithology in step S1 is a necessary condition for deciding whether the coal seam floor burst for protecting the roadway and the gas efficient extraction collaborative construction method is suitable; the hardness of the coal seam floor has a significant influence on the deep hole pre-splitting blasting effect: the higher the hardness of the coal seam floor, the more fully developed the fissures are; on the contrary, the lower the hardness of the coal seam floor, the easier the rock mass is broken, and under the action of the blasting stress wave, the crushing circle formed by the rock mass around the blasting hole due to extreme crushing will reduce the blasting impact in a buffering manner, thereby affecting the further development of the fissures; therefore, the higher the hardness of the coal seam floor, the more suitable it is to use the coal seam floor burst for protecting the roadway and the gas efficient extraction collaborative construction method, and the lithological characteristics of the coal seam floor are shown in the following table: As shown in the above table, if the coal seam floor is sandstone, the lithology is stable and the brittleness is large, the radial fissures generated by the blasting stress wave and the fissures expanded by the gas wedge effect are stable and not easy to deform, the fissure characteristics are narrow and long, and the coal seam floor burst for protecting the roadway and the gas efficient extraction collaborative construction method is suitable.

3. The coal seam floor burst for protecting the roadway and gas efficient extraction collaborative construction method according to claim 2, characterized in that: The coal seam deep hole pre-splitting blasting work equipment needed in step S2 includes: a special explosive tube, a blasting rubber line, an electric detonator, a special stemming bag, a hole sealer, a high-power blasting device, and a blasting main line; The special explosive tube is made in the coal mine; the length of the blasting rubber line is at least 300 meters; each blasting hole is equipped with a millisecond delay electric detonator; the special stemming bag is filled with stemming with a particle size less than the moisture content and a certain fluidity; the hole sealer is equipped with a rubber tube and 30 hole detection tubes; and the blasting main line is arranged from the detonation point to the blasting point. The technical performance indexes of the special explosive tube are shown in the following table: 。 4. The coal seam floor burst for protecting the roadway and gas efficient extraction collaborative construction method according to claim 3, characterized in that: The specific method for determining the thickness of the coal seam floor blasting layer in step S3 is: referring to the provision "the maximum swelling deformation after the protection layer is mined should be greater than 3%" in the "Coal and Gas Outburst Prevention and Control Regulations", the thickness of the coal seam floor blasting layer is designed, that is, the length of the explosive charging section of the blasting hole, so that the swelling deformation of the coal seam roof farthest from the coal seam floor blasting layer is greater than 3%, and since the coal seam roof is subjected to the smallest self-weight action compared with the coal body below, and the blasting wave and the blasting stress wave are attenuated during propagation, the minimum deformation occurs at the coal seam roof, thereby ensuring that the coal seam as a whole meets the provision that the deformation should be greater than 3%. The displacement monitor is installed on the coal seam roof to obtain the displacement of the coal seam roof, and to ensure that the thickness design of the coal seam floor blasting layer can make the swelling deformation displacement of the coal seam roof reach 3% of the coal seam thickness.

5. The coal seam floor burst for protecting the roadway and gas efficient extraction collaborative construction method according to claim 4, characterized in that: Step S6 is specifically: the special stemming bag is filled from the end of the explosive charging section in the blasting hole to the blasting hole orifice to form a hole sealing section, the blasting main line is connected with the electric detonator and the high-power blasting device, the safety is confirmed, the blasting is initiated, it is checked whether there is rock debris spouted from the orifice of the adjacent drainage hole after blasting, the blast hole and the drainage hole are ensured to be connected, and a stable gas migration channel is formed.

6. The coal seam floor burst for protecting the roadway and gas efficient extraction collaborative construction method according to claim 5, characterized in that: Step S7 is specifically: the hole sealer is used to seal the blasting hole again after the blasting is completed, the gas is prevented from connecting the coal seam floor rock roadway through the blasting hole after the drainage hole is connected to the negative pressure, the gas extraction circuit is ensured to be airtight, and the drainage hole flower tube is used for conventional gas extraction through the coal seam pressure relief fissures and the coal seam floor blasting fissures.

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