Determination method for pressure relief range of outburst coal seam protective layer mining area

Abstract

The invention relates to a method for measuring the pressure relief range of an outburst coal seam protective layer mining area, and belongs to the field of coal mining. The measuring method comprises the following steps: S1, constructing a directional long drill hole from a protective layer to a protected layer; s2, a sensing optical fiber and a grouting hose are installed in the drill hole; s3, after one end of the drill hole is blocked, grouting is conducted in the drill hole through a grouting hose, and the sensing optical fiber is made to be coupled with the rock stratum; s4, the steps S1 to S3 are repeated, and construction of one drill hole and laying of the sensing optical fibers of the drill hole are completed on the two sides of the protected layer respectively; and S5, according to measurement data obtained by the sensing optical fiber, carrying out strain and deformation rate analysis on the protected layer and the spacing layer, and further determining a pressure relief range and a pressure relief angle. The pressure relief range of the protected layer measured through the method is larger, the result is more accurate, simple and convenient, real-time dynamic measurement is achieved, manual well descending is not needed, the drilling track can be adjusted in time so that the drilling track can be kept at the target layer all the time, the number of drilled holes is small, the work amount is small, and construction is easy.

Description

Technical Field

[0001] The invention belongs to the field of coal mining and relates to a method for determining the pressure relief range of a mining area of ​​a protruding coal seam protective layer. Background Art

[0002] In areas with poor natural conditions for coal mines, the geological conditions of coal fields are complex, the gas content of coal seams is high, and the permeability is generally (0.1~1.0)×10 -6 μm 2 , which is generally low, and it is very difficult to extract gas from the original coal seams. However, mining practice shows that after coal seam mining causes deformation and movement of coal rock layers, even coal seams with very low permeability will increase their permeability by dozens to hundreds of times, or even more than a thousand times, creating conditions for gas migration and extraction. Therefore, coal mine gas extraction in these areas is mainly based on underground protective layer pressure relief extraction.

[0003] Protective layer mining is to first mine the coal seam (called the protective layer) adjacent to the protruding coal seam (called the protected layer), thereby improving the permeability of the protruding coal seam itself, reducing the gas pressure and gas content, and reducing the danger of outburst. According to the relative position relationship between the protective layer and the protected layer, it is divided into upper protective layer mining and lower protective layer mining. When the protective layer is located above the protruding coal seam, it is called the upper protective layer, and when it is located below the protruding coal seam, it is called the lower protective layer. Specifically, after the protective layer is mined, the adjacent protruding coal seam (protected layer) is displaced and expanded under the influence of mining, and the surrounding rock stress is also redistributed. The displacement and expansion deformation of the protruding coal seam causes a significant increase in the permeability and permeability of the protruding coal seam, that is, the protected layer has a pressure relief and permeability enhancement effect, and a large amount of gas stored in the protected layer is desorbed and released, which significantly reduces the gas pressure and gas content of the protected layer, thereby reducing or even eliminating its outburst danger. Therefore, protective layer mining is currently considered to be the most economical, safe and efficient technical method to eliminate the danger of coal seam outbursts. Measures to prevent outbursts in the mining protective layer area have the advantages of a large outburst elimination range, good outburst elimination effect and high economic benefits.

[0004] At present, the commonly used measurement methods are ground point measurement method and underground point measurement method. Both of these measurement methods have a small number of measuring points and can only reflect the changes in one point, and cannot fully reflect the stress changes in the rock formation. The measurement accuracy is not high, and only a single indicator can be measured. The pressure relief angle and the protective vertical distance cannot be measured, and thus a more accurate pressure relief range cannot be obtained. In addition, due to the limitations of terrain conditions, manual on-site collection is required underground, and the construction is more difficult. If you want to improve the measurement accuracy, you need to increase the number of drill holes, which increases the difficulty of construction. The convenience of construction and measurement accuracy cannot be achieved at the same time. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for determining the pressure relief range of the mining area of ​​the protruding coal seam protective layer, which can accurately measure the pressure relief range, has a large test coverage range, can realize online automatic collection, and is convenient for construction.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for determining the decompression range of the mining area of ​​the protective layer of a protruding coal seam, wherein both sides of the protective layer are protected layers;

[0008] The determination method comprises the following steps:

[0009] S1, construct a directional long borehole from the protective layer to the protected layer;

[0010] S2, installing the sensing optical fiber and grouting hose in the borehole;

[0011] S3, after plugging one end of the borehole, grouting is injected into the borehole through a grouting hose arranged in the plugging section to complete the coupling of the sensing optical fiber and the rock formation;

[0012] S4, repeating steps S1 to S3, adjusting the angle between the drilling direction and the axial direction of the protective layer, and completing the construction of several drilling holes with different angles and the laying of sensing optical fibers;

[0013] S5, performing strain and deformation rate analysis based on the measurement data obtained from the sensing optical fiber, and then determining the pressure relief range and pressure relief angle.

[0014] Optionally, in step S5, points on the sensing optical fiber where the deformation rate is greater than or equal to 3‰ are determined, and a range enclosed by connecting these points is the pressure relief range.

[0015] Optionally, in step S5, the angle formed by connecting the points on the sensing optical fibers of the two drilled holes on both sides of the protected layer with a deformation rate equal to 3‰ and closest to the drilling point with the axial direction of the protective layer is the pressure relief angle; the pressure relief angle also includes the angle formed by connecting the points on the sensing optical fibers of the two drilled holes on both sides of the protected layer with a deformation rate equal to 3‰ and closest to the drilling point with the axial direction of the protective layer.

[0016] Optionally, in step S2, when installing the sensing optical fiber and the grouting hose, the drill bit is connected to one end of the sensing optical fiber and the grouting hose, and when retracting the drill bit, the connecting end of the sensing optical fiber, the grouting hose and the drill bit is pulled back into the return air channel of the protective layer.

[0017] Optionally, in step S2, one end of the sensing optical fiber is connected to the optical cable junction cabinet, and then the measurement data measured by the sensing optical fiber is transmitted to the BOTDA demodulator to complete demodulation to achieve real-time dynamic measurement; before the formal measurement, the spatial resolution of the BOTDA demodulator is set to 0.2m, and the initial strain data of the sensing optical fibers in the four boreholes are measured respectively, and then the spatial position is matched with the actual trajectory of the borehole to determine the position of the point on the sensing optical fiber corresponding to the borehole.

[0018] Optionally, there is a spacer layer between the protected layer and the protective layer; the protected layer includes a first protected layer located at the upper part of the protective layer and a second protected layer located at the lower part; directional long drill holes are constructed on both sides of the first protected layer and the second protected layer.

[0019] Optionally, a first return air channel is provided on the protective layer, a second return air channel is provided on the first protected layer, and a third return air channel is provided on the second protected layer; the upper part of the first protected layer is a roof rock layer, and the lower part of the second protected layer is a floor rock layer;

[0020] There are four directional long boreholes, namely the first borehole, the second borehole, the third borehole and the fourth borehole; the first borehole starts from the first return air lane and penetrates the interval layer and the first protected layer in sequence, then drills into the top plate rock layer, and then connects to the second return air lane; the second borehole starts from the first return air lane and penetrates the interval layer and then connects to the second return air lane; the third borehole starts from the first return air lane and penetrates the interval layer and then connects to the third return air lane; the fourth borehole starts from the first return air lane and penetrates the interval layer and the second protected layer in sequence, then drills into the bottom plate rock layer, and then connects to the third return air lane.

[0021] Optionally, in step S3, when sealing the borehole, first insert a return slurry pipe into the borehole, and then use polyurethane to seal the inserted section of the return slurry pipe, and the sealing length is less than or equal to the length of the return slurry pipe; and install a valve at one end of the return slurry pipe facing the return air channel.

[0022] Optionally, in step S3, cement slurry is injected from the end of the grouting hose located at the protected layer. When the cement slurry flows out of the return grouting pipe located at the protective layer, the valve is closed and the grouting is continued for 5 minutes; then the grouting hose is gradually pulled out from the hole at one end of the borehole close to the protected layer until the cement slurry overflows from the hole.

[0023] Optionally, the sensing optical fiber is an armored multi-core single-mode optical cable.

[0024] The beneficial effects of the present invention are:

[0025] (1) The pressure relief range determined by the measuring method of the present invention is significantly increased, and the delineation of the pressure relief range is more accurate;

[0026] (2) The directional long drilling technology that has been popularized in recent years is adopted. Compared with the common drilling process used before, the drilling trajectory adjustment is more timely and convenient, and the number of drilling holes and construction costs can be reduced;

[0027] (3) The present invention adopts the BOTDA distributed optical fiber measurement technology, which can realize distributed measurement, greatly increase the test range and the number of measuring points, improve the test accuracy, and the distance between measuring points is only 0.1-2m. The shorter the sensing optical fiber, the denser the distance between measuring points. For example, the sensing optical fiber laid in a 1km long directional long borehole can achieve a distance between measuring points of 0.2m, that is, the measurement of 5000 measuring points, or even more.

[0028] (4) The selection of drilling sites is more flexible. As long as the borehole can cover the roof and floor areas of the coal mining face, it can be used. In addition, there are few auxiliary devices, only one sensing optical fiber at the hole mouth, the drilling workload is small, and the overall process is simple.

[0029] (5) The deformation data during the observation period are collected online automatically, without the need for manual on-site collection, which is more convenient.

[0030] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0032] Figure 1 It is a schematic diagram of the protective layer, the protected layer, the drilling hole and the measuring point of the present invention;

[0033] Figure 2 It is an enlarged schematic diagram of the plugging section of the directional long drilling;

[0034] Figure 3 The figure is a flow chart of the steps of the determination method of the present invention.

[0035] Reference numerals:

[0036] 1 protective layer, 11 first return air lane, 2 first protected layer, 21 second return air lane, 3 second protected layer, 31 third return air lane, 4 interval layer, 5 borehole, 51 first borehole, 52 second borehole, 53 third borehole, 54 fourth borehole, 6 sensing optical fiber, 7 grouting hose, 8 valve, 9 return slurry pipe, 10 coal mining working face, 12 pressure relief range envelope, 13 blocking section, 14 return air lane, 15 transport lane, 16 goaf. DETAILED DESCRIPTION

[0037] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0038] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0039] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0040] See also Figure 3, is a method for determining the decompression range of the mining area of ​​the protective layer of the outburst coal seam, because the mining of the protective layer has been listed as one of the two types of regional outburst prevention measures by relevant laws and regulations. Article 4 of the "Technical Specifications for Mining Protective Layers" stipulates the applicable conditions and selection principles of protective layer mining: (1) When mining coal seam groups in outburst mines, measures to prevent and control outbursts must be adopted to mine the protective layer. (2) Coal seams without outburst hazards should be selected as protective layers first; when there are several coal seams in a coal seam group that can be used as protective layers, they should be selected based on a comprehensive comparison and analysis of safety, technology, and economic rationality; when all coal seams in the mine have outburst hazards, coal seams with a smaller degree of outburst hazards can be selected as protective layers; if the mineable coal seam cannot be mined as a protective layer, the adjacent unmineable coal seam can be selected as a protective layer under economically reasonable conditions. (3) The upper protective layer should be selected first; when the lower protective layer is mined, the mining conditions of the protected layer must not be destroyed. Article 61 of the "Detailed Rules for Preventing and Controlling Coal and Gas Outbursts" stipulates: In outburst hazard areas with conditions for mining protective layers, protective layers must be mined. The following principles should be followed in selecting protective layers: (1) Coal seams without outburst hazards should be selected as protective layers first. When all coal seams in a mine have outburst hazards, coal seams with a lower degree of outburst hazards should be selected as protective layers; (2) When there are several coal seams in a coal seam group that can be used as protective layers, the coal seams with the best protection effect should be mined first; (3) The upper protective layer should be selected first. When mining the lower protective layer, the mining conditions of the protected layer shall not be damaged; (4) When mining a coal seam group, if there is a coal seam with a thickness of 0.5m or more without outburst hazards within the effective protection vertical distance, it should be mined first as a protective layer, except when the distance to the outburst coal seam is too close to threaten the safety of the protective layer working face or may damage the mining conditions of the outburst coal seam.

[0041] The present invention proposes a method for determining the pressure relief range of the mining area of ​​the outburst coal seam protective layer, such as Figures 1-2 As shown, the two sides of the protective layer 1 are defined as protected layers; the protective layer 1 and the protected layer are defined as an interval layer 4, which is a rock layer formed by natural deposition; the protected layer includes a first protected layer 2 located on the upper part of the protective layer 1 and a second protected layer 3 located on the lower part, the upper rock layer of the first protected layer 2 is a roof rock layer, and the lower rock layer of the second protected layer 3 is a bottom rock layer; a first return air channel 11 is provided on the protective layer 1, a second return air channel 21 is provided on the first protected layer 2, and a third return air channel 31 is provided on the second protected layer 3.

[0042] The determination method comprises the following steps:

[0043] S1, before the protective layer 1 coal mining face 10 is mined, a directional long drill hole 5 is constructed from the protective layer 1 toward the protected layer; in some embodiments of the present invention, the drill hole 5 adopts a directional long drill hole technology, and the diameter of the drill hole 5 ranges from 94mm to 153mm.

[0044] Directional long drilling technology is a drilling technology that controls drilling by adjusting the direction of the drill string. Directional long drilling technology uses the drill bit on the adjustable drill rod to extend the borehole in different directions, so as to achieve drilling at a specific location. This technology is equipped with a remote control device, which receives remote control commands, and the operator can accurately control the drilling direction on the ground. Since the strength and stability of the drill rod affect the drilling direction, the drill rod adjustment process is often used to ensure the accuracy of the drilling direction. Directional long drilling technology has the advantages of high drilling accuracy, high construction efficiency and low cost. The drill bit is controlled to drill on a predetermined trajectory through a guide device to achieve long-distance, high-precision directional drilling. At the same time, this technology can reduce the risk of gas outburst and coal and gas outburst, and improve the safety level of mine production. In mine gas control, directional long drilling technology can effectively extract coal seam gas, reduce gas concentration, and prevent gas explosion accidents. This technology is particularly suitable for high-gas mines, coal and gas outburst mines, and mines with complex geological structures and unstable coal seams.

[0045] S2, installing the sensing optical fiber 6 and the grouting hose 7 in the borehole 5;

[0046] In step S2, when installing the sensing optical fiber 6 and the grouting hose 7, the drill bit is connected to one end of the sensing optical fiber 6 and the grouting hose 7, and when withdrawing the drill bit, the connection end of the sensing optical fiber 6, the grouting hose 7 and the drill bit is pulled back into the return air lane of the protective layer 1; after the installation is completed, the integrity of the sensing optical fiber 6 and the grouting hose 7 is retested in the return air lane;

[0047] Connect one end of the sensing optical fiber 6 to the optical cable junction cabinet, and then transmit the measurement data measured by the sensing optical fiber 6 to the BOTDA demodulator to complete demodulation to achieve real-time dynamic measurement; before the formal measurement, set the spatial resolution of the BOTDA demodulator to 0.2m, perform three initial strain data measurements on the sensing optical fibers 6 in the four boreholes 5, and then match the spatial position with the actual trajectory of the borehole 5 to determine the position of the point on the sensing optical fiber 6 corresponding to the borehole 5.

[0048] BOTDA demodulator is an important device used in the field of fiber optic sensing. It is mainly used for long-distance (up to tens of kilometers) distributed temperature and strain measurement. It can analyze the frequency shift of the Brillouin signal light reflected from each point of the optical fiber, so as to determine the strain distribution of the optical fiber along the line. It has many advantages such as continuous distributed detection, no blind spots, long monitoring distance, low power consumption, high reliability, embedded design, simple installation, easy maintenance, flexible expansion and online self-diagnosis.

[0049] Armored multi-core single-mode optical cable is a kind of optical signal transmission and sensor device, which is mainly used for optical signal transmission and the perception of changes in measured physical quantities. It is generally composed of optical fiber, casing, filler, reinforcing core, waterproof layer, armor layer, etc. Each section of the optical fiber is both a sensing unit and a transmission medium, realizing both "transmission" and "sensing".

[0050] S3, after plugging one end of the borehole 5, grouting is injected into the borehole 5 through a grouting hose 7 arranged in the plugging section to complete the coupling of the sensing optical fiber 6 and the rock formation;

[0051] Optionally, in step S3, when sealing the borehole 5, first insert a 5m long return pipe 9 into the borehole 5, and then use polyurethane to seal the inserted section of the return pipe 9 to form a sealing section 13. The sealing length is 4m. In actual operation, the sealing length needs to be less than or equal to the length of the return pipe 9 to ensure that both ends of the return pipe 9 are unobstructed; and install a valve 8 at the end of the return pipe 9 facing the return air channel.

[0052] Optionally, in step S3, cement slurry is injected from the end of the grouting hose 7 located in the second return air lane 21, and it is observed whether there is cement slurry flowing out from the valve 8 of the return pipe 9 in the first return air lane 11. When cement slurry flows out of the return pipe 9 in the first return air lane 11, the valve 8 is closed and the grouting is continued for 5 minutes; then the grouting hose 7 is gradually lifted up from the second return air lane 21, and the lifting speed is determined according to the grouting amount, but it should be ensured that the slurry outlet of the grouting hose 7 is always placed in the slurry until the cement slurry overflows from the orifice, until the cement slurry overflows from the orifice of the first borehole 51 close to one end of the second return air lane 21, and the grouting hose 7 is lifted up from the orifice to complete the laying of the sensing optical fiber 6 of the first borehole 51.

[0053] S4, repeat steps S1 to S3, adjust the angle between the direction of the drill hole 5 and the axial direction of the protective layer 1, complete the construction of several drill holes 5 with different angles and the laying of their sensing optical fibers 6; directional long drill holes 5 are constructed on both sides of the first protected layer 2 and the second protected layer 3, that is, four directional long drill holes 5 are provided.

[0054] The four bore holes 5 are respectively a first bore hole 51, a second bore hole 52, a third bore hole 53 and a fourth bore hole 54; the first bore hole 51 starts from the first return air lane 11 and penetrates through the interval layer 4 and the first protected layer 2 in sequence, then drills into the top rock layer, and then connects to the second return air lane 21; the second bore hole 52 starts from the first return air lane 11 and penetrates through the interval layer 4 and then connects to the second return air lane 21; the third bore hole 53 starts from the first return air lane 11 and penetrates through the interval layer 4 and then connects to the third return air lane 31; the fourth bore hole 54 starts from the first return air lane 11 and penetrates through the interval layer 4 and the second protected layer 3 in sequence, then drills into the bottom rock layer, and then connects to the third return air lane 31.

[0055] S5, performing strain and deformation rate analysis based on the measurement data obtained by the sensing optical fiber 6, and then determining the pressure relief range and pressure relief angle.

[0056] In step S5, before the coal mining working face 10 of the protective layer 1 is pushed to 100m from the borehole 5 area, the modem is set to continuous dynamic measurement, and the data is stored for strain and deformation rate analysis. This monitoring continues until the working face passes the borehole 5 area and is 100m away from the area. According to the strain and deformation rate analysis of the measured data, the points on the sensing optical fiber 6 with a deformation rate greater than or equal to 3‰ are determined, and the range enclosed by connecting these points is the pressure relief range; the angle formed by connecting the points on the sensing optical fiber 6 of two adjacent boreholes 5 with a deformation rate equal to 3‰ and the closest to the drilling point with the axial direction of the protective layer 1 is the pressure relief angle, and the pressure relief angle also includes the angle formed by connecting the points with a deformation rate equal to 3‰ and the closest to the drilling point with the axial direction of the protective layer. Since BOTDA only needs to measure at one end, when the sensing optical fiber 6 is broken due to rock formation movement, the two ends of the broken sensing optical fiber 6 can be measured in the first return air lane 11, the second return air lane 21, and the third return air lane 31, and the strain data can still be obtained.

[0057] like Figure 1 As shown, the areas where the deformation rate of the sensing optical fiber 6 in the first borehole 51 is greater than 3‰ are the A1A3 section, the A4A5 section, and the A6A7 section, the area where the deformation rate of the sensing optical fiber 6 in the second borehole 52 is greater than 3‰ is the B1B2 section, the area where the deformation rate of the sensing optical fiber 6 in the third borehole 53 is greater than 3‰ is the C1C2 section, and the areas where the deformation rate of the sensing optical fiber 6 in the fourth borehole 54 is greater than 3‰ are the D1D3 section, the D4D5 section, and the D6D7 section; the points on the sensing optical fiber 6 where the deformation rate is equal to 3‰ are A1, A2, B1, B2, C1, C2, D1, and D2 respectively, the angle between the A1B1 line and the protective layer 1 is the pressure relief angle δ1, the angle between the A2B2 line and the protective layer 1 is the pressure relief angle δ2, the angle between the C1D1 line and the protective layer 1 is the pressure relief angle δ3, and the angle between the C2D2 line and the protective layer 1 is the pressure relief angle δ4. The envelope line obtained by connecting points B0, B1, A1, A3, A4, A5, A6, A7, A2, B2, B3, C2, D2, D7, D6, D5, D4, D3, D2, D1, and C1 in sequence is the pressure relief range; among them, B0 and B3 are the two ends of the coal mining working face 10 in the protective layer 1, respectively.

[0058] In the present invention, in addition to the above-mentioned return air lanes, a number of return air lanes 14 and transport lanes 15 are also connected and arranged. The return air lane 14 refers to the lane through which the return air flows, which is mainly used to discharge the dirty gas generated in the coal mine (such as gas, exhaust gas generated by diesel rubber-wheeled vehicles, and dirty air exhaled by workers) out of the mine to ensure the cleanliness and safety of the air underground in the coal mine. The transport lane 15, especially the main transport lane, is the main lane in coal mine production, which is used to transport coal uninterruptedly. According to the specific conditions of the coal mine, the transport lane 15 may be equipped with a belt conveyor (inclined shaft) or a skip (vertical shaft) to transport coal. In addition, the transport lane 15 also undertakes the ventilation task to provide fresh air for the entire coal mine.

[0059] The goaf 16 is the space left after the coal mining face is mined. The coal and rock layers above and below the goaf will move and deform to produce a certain pressure relief range, causing a large amount of gas to flow into the coal mining face.

[0060] In some embodiments of the present invention, the sensing optical fiber 6 is an armored sensing optical fiber 6. The present invention adopts directional long drilling, and the trajectory of the drilling hole 5 can be adjusted in real time as needed, and the drilling is constructed to the most favorable layer and position for investigating the pressure relief range, which can cover the entire coal and rock mass of the top and bottom plates of the coal mining working face 10 of the rectification protective layer 1, with a large test coverage range and more test data, and the pressure relief range analyzed based on this is more accurate.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for determining the pressure relief range of a mining area of ​​a protruding coal seam protective layer, characterized in that: The two sides of the protective layer (1) are protected layers; The determination method comprises the following steps: S1, constructing a directional long drill hole (5) from the protective layer (1) toward the protected layer; S2, installing a sensing optical fiber (6) and a grouting hose (7) in the borehole (5); S3, after plugging one end of the borehole (5), grouting is injected into the borehole (5) through a grouting hose (7) arranged at the plugging section to complete the coupling between the sensing optical fiber (6) and the rock formation; S4, repeating steps S1 to S3, adjusting the angle between the direction of the drilling hole (5) and the axial direction of the protective layer (1), completing the construction of several drilling holes (5) with different angles and the laying of the sensing optical fiber (6); S5, performing strain and deformation rate analysis based on the measurement data obtained by the sensing optical fiber (6), and then determining the pressure relief range and pressure relief angle.

2. The method for determining the pressure relief range of the mining area of ​​the protruding coal seam protective layer according to claim 1 is characterized in that: In step S5, points on the sensing optical fiber (6) with a deformation rate greater than or equal to 3‰ are determined, and the range enclosed by connecting these points is the pressure relief range.

3. The method for determining the pressure relief range of the mining area of ​​the protruding coal seam protective layer according to claim 1 or 2, characterized in that: In step S5, the angle formed by connecting the points with a deformation rate of 3‰ and closest to the drilling point on the sensing optical fiber (6) of the two drill holes (5) respectively located on both sides of the protected layer with the axial direction of the protective layer (1) is the pressure relief angle; the pressure relief angle also includes the angle formed by connecting the points with a deformation rate of 3‰ and closest to the drilling point with the axial direction of the protective layer (1).

4. The method for determining the pressure relief range of the mining area of ​​the protruding coal seam protective layer according to claim 1 is characterized in that: In step S2, when installing the sensing optical fiber (6) and the grouting hose (7), the drill bit is connected to one end of the sensing optical fiber (6) and the grouting hose (7), and when retracting the drill bit, the connection ends of the sensing optical fiber (6), the grouting hose (7) and the drill bit are pulled back into the return air channel of the protective layer (1).

5. The method for determining the pressure relief range of the mining area of ​​the protruding coal seam protective layer according to claim 4 is characterized in that: In step S2, one end of the sensing optical fiber (6) is connected to the optical cable junction cabinet, and then the measurement data measured by the sensing optical fiber (6) is transmitted to the BOTDA demodulator to complete demodulation to achieve real-time dynamic measurement; before the formal measurement, the spatial resolution of the BOTDA demodulator is set to 0.2m, and the initial strain data of the sensing optical fibers (6) in the four boreholes (5) are measured respectively, and then the spatial position is matched with the actual trajectory of the borehole (5), so as to determine the position of the point on the sensing optical fiber (6) corresponding to the borehole (5).

6. The method for determining the pressure relief range of the mining area of ​​the protruding coal seam protective layer according to claim 1 is characterized by: A spacer layer (4) is provided between the protected layer and the protective layer (1); the protected layer comprises a first protected layer (2) located at the upper part of the protective layer (1) and a second protected layer (3) located at the lower part; and directional long drill holes (5) are constructed on both sides of the first protected layer (2) and the second protected layer (3).

7. The method for determining the pressure relief range of the mining area of ​​the protruding coal seam protective layer according to claim 6 is characterized by: A first return air channel (11) is provided on the protective layer (1), a second return air channel (21) is provided on the first protected layer (2), and a third return air channel (31) is provided on the second protected layer (3); the upper part of the first protected layer (2) is a roof rock layer, and the lower part of the second protected layer (3) is a floor rock layer; The directional long boreholes (5) are provided with four, namely a first borehole (51), a second borehole (52), a third borehole (53) and a fourth borehole (54); the first borehole (51) starts from the first return air channel (11) and penetrates through the spacing layer (4) and the first protected layer (2) in sequence, then drills into the top rock layer, and then connects to the second return air channel (21); the second borehole (52) starts from the first return air channel (11) and penetrates through the spacing layer (4) and then connects to the second return air channel (21); the third borehole (53) starts from the first return air channel (11) and penetrates through the spacing layer (4) and then connects to the third return air channel (31); the fourth borehole (54) starts from the first return air channel (11) and penetrates through the spacing layer (4) and the second protected layer (3) in sequence, then drills into the bottom rock layer, and then connects to the third return air channel (31).

8. The method for determining the pressure relief range of the mining area of ​​the protruding coal seam protective layer according to claim 1 is characterized by: In step S3, when the borehole (5) is blocked, a return slurry pipe (9) is first inserted into the borehole (5), and then the inserted section of the return slurry pipe (9) is blocked with polyurethane, wherein the blocking length is less than or equal to the length of the return slurry pipe (9); and a valve (8) is installed at one end of the return slurry pipe (9) facing the return air channel.

9. The method for determining the pressure relief range of the mining area of ​​the protruding coal seam protective layer according to claim 1, characterized in that: In step S3, cement slurry is injected from the end of the grouting hose (7) located at the protected layer. When the cement slurry flows out of the return grouting pipe (9) located at the protective layer (1), the valve (8) is closed and the grouting is continued for 5 minutes; then the grouting hose (7) is gradually pulled out from the hole at one end of the drill hole (5) close to the protected layer until the cement slurry overflows from the hole.

10. The method for determining the pressure relief range of the mining area of ​​the protruding coal seam protective layer according to claim 1, characterized in that: The sensing optical fiber (6) is an armored multi-core single-mode optical cable.

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