A continuous monitoring method for three-dimensional voids of overburden rock of a coal mine

Abstract

The application discloses a kind of continuous monitoring methods of coal mine mining overburden rock three-dimensional interstice, belong to coal mining technical field.Through coal mine overburden rock multi-position separation layer monitoring device measurement coal seam mining after the three-dimensional interstice of overburden rock: based on coal seam mining thickness and water conducting fractured zone development height, formulate mining overburden rock interstice monitoring scheme;Perpendicular monitoring borehole is arranged on the surface above the stoping working face, and coal mine overburden rock multi-position separation layer monitoring device is installed in the borehole;Real-time acquisition, storage and analysis monitoring data are acquired by data acquisition box and computer;Based on the advancing distance of coal mining face, the evolution law of single-hole interstice of mining overburden rock is analyzed;Kriging interpolation method is used to predict the unknown point interstice of working face according to the multi-hole monitoring data, and the spatial curved surface visualization model of mining overburden rock interstice is generated.The application can realize the continuous monitoring of the distribution characteristics of overburden rock three-dimensional interstice in the process of coal seam mining, and provide a scientific basis for determining the key parameters of grouting and filling.

Description

Technical Field

[0001] This invention belongs to the field of coal mining technology, and specifically relates to a method for continuous monitoring of three-dimensional voids in coal mine overburden. Background Technology

[0002] Coal seam mining inevitably causes the movement, deformation, and fracture of the overlying strata. Influenced by the lithology and fracture characteristics of the strata, the spaces formed by uneven settlement of the overlying strata, including delamination spaces, fissures, and under-compacted spaces in the caving zone, are collectively referred to as mining-induced overlying voids. Their size is closely related to the vertical distribution characteristics of the overlying strata. These voids provide free space for strata movement. Under the influence of surface building loads, groundwater, and mining disturbances, the overlying strata behind the working face undergo secondary movement and deformation, potentially leading to sudden surface collapse, sudden fracture of thick, hard roof layers, and rockbursts. Therefore, real-time monitoring of the size and distribution of mining-induced overlying voids is a prerequisite and crucial means of preventing mine disasters. Furthermore, grouting and filling technology utilizes these voids as storage space for gangue. To ensure the effectiveness of filling in controlling strata movement, it is essential to clarify the timing, volume, and location of grouting and filling, necessitating research into the distribution characteristics of mining-induced overlying voids.

[0003] Currently, rock mass internal displacement monitoring commonly employs multi-point displacement gauges and distributed fiber optic monitoring technology. Existing multi-point displacement gauges, including purely mechanical and electronic digital display types, can monitor baseline displacement and roof delamination, but suffer from drawbacks such as limited measurement range, relatively independent monitoring point equipment, and inability to perform long-term monitoring. Existing distributed fiber optic monitoring can achieve large-scale, distributed dynamic monitoring of surrounding rock stress and deformation at different scales, but it suffers from cumbersome calculation steps and high monitoring costs. Therefore, there is an urgent need to update rock mass internal displacement monitoring methods and propose a continuous monitoring method for the three-dimensional voids of mining-induced overburden. Summary of the Invention

[0004] To address the aforementioned problems and shortcomings of existing methods, a continuous monitoring method for three-dimensional voids in mining-induced overburden is provided. This method enables real-time, continuous, and long-term monitoring of mining-induced overburden voids during the working face mining process, obtaining the distribution characteristics and evolution patterns of mining-induced overburden voids, and guiding the field application of grouting and filling technology.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for continuous monitoring of three-dimensional voids in coal mine overburden, comprising the following steps:

[0006] S1. Collect information on the coal seam thickness and water-conducting fracture zone development height of the tested mining face, and then select the mining overburden above the tested mining face as the target monitoring area.

[0007] S2. Multiple vertical monitoring boreholes are arranged at intervals on the surface towards the working face being mined. The position, spacing, and number of vertical monitoring boreholes are set according to the area of ​​the working face and the monitoring accuracy. Each vertical monitoring borehole passes sequentially through the curved subsidence zone, the fracture zone, and up to the top of the collapse zone. Then, a continuous monitoring device is installed in the vertical monitoring borehole. The continuous monitoring device includes a sleeve with a hollow tube structure and a data acquisition box. The sleeve includes an upper external section and a lower internal section. Multiple horizontally arranged cross supports are provided on both sides of the external section. The ends of the cross supports are movably connected to a winding hub through a coupling and a nut plate. The internal section has a series of boreholes that pass through the sleeve sequentially and connect sequentially to different... Multiple anchor heads are fixed to the deep hole wall, each anchor head is connected to a measuring line, and the top of the sleeve is equipped with a counting hub matching the number of anchor heads. Each counting hub is connected to a speed sensor. The number of cross supports matches the number of anchor heads. The measuring line of each anchor head is changed in direction through a separately matched counting hub and then wound onto a separately matched winding hub. Each winding hub is equipped with a counterweight suspended by a counterweight line. All speed sensors are connected to the data acquisition box through sensor signal lines. A ring of inclined spring hooks is provided around the outer circumference of the anchor head. The spring hooks include hook grooves, and a remote control relay is provided at the bottom of the hook grooves. The hook grooves also contain hooks that are controlled to extend and retract by a spring.

[0008] S3. Within the height range of the water-conducting fracture zone determined in S1, anchor different anchor heads in each vertical monitoring borehole to the rock wall around the borehole. The side line connected to the anchor head is fixed to the top opening of the sleeve through the counting hub and the winding hub.

[0009] S4. Pull the speed sensor signal line on the side of the counting hub of the coal mine overburden multi-position delamination monitoring device to the borehole data acquisition box and connect it to the computer. Use each anchor head as a measuring point and record and store all measuring point delamination data in the computer in real time.

[0010] S5. In order to obtain the evolution diagram of the three-dimensional voids of the overlying rock as the working face advances, according to the vertical monitoring borehole layout scheme in S2, repeat steps S2-S4, monitor and record the measurement data of a single vertical monitoring borehole at different advance distances during the mining process of the working face under test in real time, analyze the delamination and surface subsidence monitoring values ​​of adjacent measuring points at the bottom and above the fracture zone, and obtain the variation law of voids at a certain point of the working face under test with the advance distance.

[0011] S6. Based on the vertical monitoring borehole layout scheme in S2, repeat step S5 to obtain all vertical monitoring borehole data above the working face under mining at different advance distances. Store all vertical monitoring borehole data in the computer as multi-hole monitoring data. Using the multi-hole monitoring data stored in the computer, use the Kriging interpolation method to predict the voids at unknown points in the mining working face, generate a three-dimensional visualization structure diagram of the void space surface of the mining overburden, obtain the void space distribution characteristics of the working face under mining, and provide guidance for the design of grouting filling location and filling volume.

[0012] Furthermore, the mining-induced overburden void space was selected as the target monitoring area, and a monitoring plan for the mining-induced overburden void was formulated, which specifically includes the following steps:

[0013] S101. The monitoring borehole is located in the rock strata at the bottom of the fracture zone. Based on numerical simulation and actual measurements of the three-zone height of the adjacent working face, the borehole depth is: h b =H d -H c In the formula, h b H represents the drilling depth. d H represents the depth of the coal seam at the working face. c The height of the landslide zone;

[0014] S102. Determine the spacing, location, and number of boreholes based on the area of ​​the mining face, geological conditions, and monitoring accuracy.

[0015] S103. Based on the vertical monitoring drill spacing, monitoring boreholes are arranged horizontally along the coal seam strike and vertically along the coal seam dip at the center point on the ground above the working face to form mining overburden void measurement lines.

[0016] Furthermore, in S2, the arrangement scheme of vertical monitoring boreholes arranged at intervals along the working face advance direction includes: directional detection boreholes arranged at intervals along the working face direction and directional detection boreholes arranged perpendicularly to the directional monitoring boreholes at the middle position of the working face. The directional detection boreholes start at the working face cut and end at the main return passage. The starting point and ending point of the directional detection boreholes are the main haulage roadway and the auxiliary haulage roadway, respectively.

[0017] Furthermore, the specific monitoring steps in S4 include:

[0018] S401. The anchor head is connected to the borehole wall of the vertical monitoring borehole via a hook. When the rock stratum where multiple anchor heads are installed in the sleeve moves, the anchor head will move the measuring line downward with the rock stratum. At the same time, the winding hub releases measuring lines of equal length and passes through the counting hub. The speed sensor on the side of the counting hub senses the change in the length of the measuring line and sends an electrical signal to the data acquisition box. The data acquisition box interface obtains the real-time subsidence of the rock stratum at different anchor head positions.

[0019] S402. Subtract the subsidence of adjacent rock layers monitored by the rotation speed sensors corresponding to all adjacent anchor heads to obtain the amount of separation of adjacent rock layers within the vertical monitoring borehole range.

[0020] S403. Real-time dynamic measurement of the elevation change of the surface at the location of the vertical monitoring borehole using the Global Positioning System (RTK) to obtain the real-time surface subsidence.

[0021] S404. Calculate the single-hole voids in the mining-induced overburden using the monitoring results of rock strata subsidence, adjacent rock strata separation, and surface subsidence, and obtain the void distribution between different layers of the mining-induced overburden.

[0022] Furthermore, the voids in a single pore of the overburden rock affected by mining specifically include voids in the caving zone, fracture zone, and flexural subsidence zone. The voids in the flexural subsidence zone include voids below and above the key stratum. The void calculation method is as follows:

[0023] Based on the amount of delamination of adjacent rock strata, the void above the key stratum in the flexural subsidence zone is the total amount of delamination of the rock strata above the key stratum in the flexural subsidence zone; the void below the key stratum in the flexural subsidence zone is the total amount of delamination of the rock strata below the key stratum in the flexural subsidence zone; the void in the fracture zone is the total amount of delamination of the rock strata in the fracture zone; and the void in the caving zone is the coal seam mining thickness minus the void in the flexural subsidence zone, the void in the fracture zone, and the amount of surface subsidence.

[0024] Furthermore, the specific steps for generating a three-dimensional visualization structure diagram of the void space surface of the mining-induced overburden are as follows: Based on all vertical monitoring borehole data stored in the computer, the Kriging interpolation method is used, and MATLAB software is used to perform interpolation on the three-dimensional dataset of discrete point data to predict the voids at unknown points in the mining face, thereby generating the three-dimensional void surface of the mining-induced overburden and its equation.

[0025] The beneficial technical effects of this invention are as follows: This method can realize continuous monitoring of the three-dimensional voids in the overburden of mining operations. By using anchors at different depths to monitor the subsidence and delamination of different layers of the overburden, combined with the surface subsidence, the monitoring target of the voids in the "three zones" of the overburden throughout the entire process of coal mining face advancement is achieved. Non-contact measurement avoids the errors caused by manual measurement, and can store and analyze void data within the monitoring range in real time. It can present the dynamic change surface of the voids in the overburden of mining operations, analyze the distribution characteristics and evolution law of the voids in the overburden of mining operations, provide a solid foundation for studying the movement and fracture characteristics of the overburden in the mining area, and provide a more scientific basis for determining the key parameters of grouting and filling. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the implementation of the method for continuous monitoring of porosity in overburden during mining, as described in this invention.

[0027] Figure 2 This is a top view of the borehole arrangement for void monitoring in an embodiment of the present invention;

[0028] Figure 3 Here are schematic diagrams of a coal mine overburden multi-layer delamination monitoring device in an embodiment of the present invention; (a) front view; (b) top view; (c) anchor head cross-section view;

[0029] Figure 4 This is a cross-sectional view of the vertical monitoring borehole for porosity in an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of the porosity surface in an embodiment of the present invention.

[0031] In the diagram: 1—Sleeve; 2—Horizontal support; 3—Winding hub; 4—Counterweight line; 5—Counterweight; 6—Counterweight hub; 7—Speed ​​sensor; 8—Measuring line; 9—Anchor head; 10—Hook; 11—Remote control relay; 12—Coupling; 13—Nut piece; 14—Spring; 15—Sensor signal line; 16—Data acquisition box; 17—Collapse zone; 18—Fissure zone; 19—Bending and sinking zone; 20—Key layer; 21—Vertical monitoring drill. Detailed Implementation

[0032] The following is a further description of a specific drilling example with reference to the accompanying drawings:

[0033] This invention discloses a method for continuous monitoring of three-dimensional voids in coal mine overburden, the implementation process of which is as follows: Figure 1 As shown, the monitoring method includes the following steps:

[0034] S1. Based on the coal seam thickness and the height of the water-conducting fracture zone, the mining-induced overburden void space is selected as the target monitoring area, and a monitoring scheme for the mining-induced overburden void space is formulated, which includes the following steps:

[0035] S101. Deploy vertical monitoring borehole 21 to determine that the final borehole of vertical monitoring borehole 21 is located in the rock stratum at the bottom of the fracture zone. Based on numerical simulation and actual measurements of the three-zone height of the adjacent working face, the depth of vertical monitoring borehole 21 is...

[0036] h b =H d -H c

[0037] In the formula, h b For vertical monitoring of borehole depth 21; H d H represents the depth of the coal seam at the working face. c This represents the height of the landslide zone.

[0038] S102. Based on the area of ​​the mining face, geological conditions, and monitoring accuracy, determine the spacing, location, and number of vertical monitoring boreholes 21.

[0039] S103. Based on the vertical monitoring drill spacing, monitoring boreholes are arranged horizontally along the coal seam strike and vertically along the coal seam dip at the center point on the ground above the working face to form mining overburden void measurement lines.

[0040] S2. Vertical monitoring boreholes 21 are arranged on the surface above the longwall face. A multi-site segregation monitoring device for coal mine overburden is installed in the vertical monitoring boreholes 21. The specific steps include:

[0041] S201. When the rock stratum where the anchor head 9 is located moves, it drives the measuring line 8 to move downward. At the same time, the winding hub 3 releases a measuring line of equal length and passes it through the counting hub 6. The rotation speed sensor 7 on the side of the counting hub 6 senses the change in the length of the measuring line 8 and sends an electrical signal to the ground, which is received by the borehole data acquisition box 16. After processing by the computer, the real-time rock stratum subsidence is obtained.

[0042] S202. Subtract the subsidence of adjacent rock layers monitored by the rotation speed sensor corresponding to each anchor head in step S201 above to obtain the amount of separation of adjacent rock layers within the monitoring hole range.

[0043] S203. Use the Global Positioning System (GPS) to measure and monitor the changes in surface elevation at monitoring points in real time to obtain the real-time surface subsidence.

[0044] S204. Calculate the monitoring results of rock strata subsidence, adjacent rock strata separation, and surface subsidence obtained in steps S201, S202, and S203 to obtain the void distribution between different layers of the mining overburden.

[0045] S3. Based on the advance distance of the coal mining face, analyze the delamination and surface subsidence monitoring values ​​of adjacent base points at the bottom and above of the fracture zone to obtain the evolution law of single-hole voids in the overburden caused by mining as the working face advances.

[0046] S301, the voids in the mining overburden specifically include voids in the caving zone, fracture zone, and flexural subsidence zone. Among them, the voids in the flexural subsidence zone include voids below the key layer and voids above the key layer.

[0047] S302. The calculation method for single-hole voids in the overburden is as follows: Based on the amount of delamination of adjacent rock strata obtained in step S2, the void above the key stratum in the bending subsidence zone is the total amount of delamination of the rock strata above the key stratum in the bending subsidence zone; the void below the key stratum in the bending subsidence zone is the total amount of delamination of the rock strata below the key stratum in the bending subsidence zone; the void in the fracture zone is the total amount of delamination of the rock strata in the fracture zone; and the void in the caving zone is the coal seam mining thickness minus the void in the bending subsidence zone, the void in the fracture zone, and the amount of surface subsidence.

[0048] S4. Based on the multi-pore monitoring data stored in the computer, the Kriging interpolation method is used. The MATLAB software is used to perform interpolation on the three-dimensional dataset of discrete point data to predict the voids at unknown points in the longwall face and generate the three-dimensional void surface and its equation of the mining-induced overburden.

[0049] The following are specific embodiments in a certain mine, following the operating steps of the present invention:

[0050] This embodiment, using a specific mining engineering example, further illustrates the detailed implementation of the continuous monitoring method for the porosity of overburden in coal mines provided by this invention. The 42207 working face in a certain mine is a currently being mined face, 1050m long and 300m wide. It mines coal seam 4-2, with a thickness of 3.0m, a dip angle of 3°, a mining depth of 150m, a topsoil layer thickness of 30m, and a bedrock thickness of 120m. The specific implementation steps of the continuous monitoring method for the three-dimensional porosity of the overburden in the 42207 working face are as follows.

[0051] S1. Based on the coal seam thickness and the height of the water-conducting fracture zone, the mining-induced overburden above the coal seam of the 42207 working face with a strike length of 450m and extending to the surface is selected as the target monitoring area, and a monitoring scheme for the voids in the mining-induced overburden is formulated.

[0052] Based on the measured height of the water-conducting fracture zone in adjacent working faces, and combined with the height of the "three zones" of working face 42207 obtained using FLAC3D software, the height of the water-conducting fracture zone in working face 42207 is determined to be 50.05m, and the height of the collapse zone is 9.00m. Therefore, the depth of vertical monitoring borehole 21 is determined as follows:

[0053] h b =H d -H c =150m - 9m = 141m

[0054] Based on the working face area, geological conditions, and monitoring accuracy, the strike borehole spacing was determined to be 45m, and the dip borehole spacing to be 30m. The overburden void monitoring borehole layout scheme is as follows: 11 monitoring boreholes are arranged horizontally along the strike of the coal seam and vertically along the dip of the coal seam, passing through the center point on the surface above the working face. Figure 2 As shown.

[0055] S2. Vertical monitoring borehole 21 is arranged on the surface above the 42207 working face, and a multi-layer delamination monitoring device for coal mine overburden is installed in the borehole.

[0056] like Figure 3As shown in (a), (b) and (c), the coal mine overburden multi-layer delamination monitoring device mainly includes a sleeve 1, a horizontal support 2, a wire winding hub 3, a measuring line 8, a counterweight 5, a counting hub 6, a speed sensor 7, a measuring line 8, an anchor head 9, a hook 10, and a remote control relay 11. Specifically, it includes a sleeve 1 for insertion at the wellhead, multiple horizontally arranged cross supports 2 with included angles on the side walls of the sleeve 1, and a winding hub 3 with a connecting shaft 12 at the end of the cross supports 2. A counterweight 5 is vertically connected to the winding hub 3 with a counterweight line 4. Anchor heads 9 matching the number of winding hubs 3 are provided inside the sleeve 1. A counting hub 6 matching the number and position of the winding hubs 3 is provided at the top of the sleeve 1. Each anchor head 9 is connected to an individual measuring line 8. Each measuring line 8 is individually connected to the counting hub 6 and the winding hub 3. The measuring line 8 connected to each anchor head 9 is wound around the individually matched winding hub 3 after changing direction through the individually matched counting hub 6. All speed sensors 7 are connected to a computer through sensor signal lines. Anchor head 9 consists of two parts: the lower part is an inverted isosceles trapezoidal structure, and the upper part is a cylindrical structure. The upper part of anchor head 9 has a groove to reduce weight and ensure that the center will not flip. The lower part of anchor head 9 has a through hole at its center, which is connected to the groove in the upper part, so as to facilitate the passage of the measuring line 8 of other anchor heads 9.

[0057] like Figure 4 As shown, the outer side of the upper part of the anchor head 9 is provided with a spring hook that is inclined up and down around the circumference. The spring hook includes a hook groove. A remote control relay 11 is provided at the bottom of the hook groove. The remote control relay 11 is connected to a spring 14 controlled by it. The spring 14 is connected to a hook 10 that is controlled by the spring 14 to extend and retract from the hook groove.

[0058] When the rock stratum where the anchor head 9 is located moves, it drives the measuring line 8 to move downward. At the same time, the winding hub 3 releases a measuring line of equal length and passes it through the counting hub 6. The rotation speed sensor 7 on the side of the counting hub 6 senses the change in the length of the measuring line 8 and sends an electrical signal to the ground, which is received by the borehole data acquisition box 16. After being processed by the computer, the real-time rock stratum subsidence is obtained.

[0059] Subtract the subsidence of the adjacent rock layer monitored by the rotation speed sensor 7 corresponding to each anchor head 9 in the above steps to obtain the separation amount of the adjacent rock layer within the monitoring hole range.

[0060] The surface elevation changes at monitoring points are measured in real time using the Global Positioning System (GPS) and the real-time surface subsidence is obtained.

[0061] The monitoring results of rock strata subsidence, adjacent rock strata separation, and surface subsidence obtained from the above steps are calculated to obtain the void distribution between different layers of the mining overburden.

[0062] S3. Based on the advance distance of the coal mining face, analyze the delamination and surface subsidence monitoring values ​​of adjacent base points at the bottom and above of the fracture zone to obtain the evolution law of single-hole voids in the mining overburden as the working face advances, i.e., the calculation results of the key layer.

[0063] Based on the calculation results of the key layer, the medium sandstone 50.5m away from the coal seam is identified as key layer 20. Based on the delamination amount of adjacent rock layers obtained in step S2, the void S above the key layer in the bending subsidence zone is determined. OA This represents the total amount of delamination between the key layer 20 and the surface, specifically, the total thickness of the rock strata is 87.45m.

[0064] Void S beneath the key layer within the curved subsidence zone AB The separation amount between the key layer 20 and the top rock layer of the fracture zone is 12.5m;

[0065] Void S in fracture zone BC This represents the total amount of delamination within the fracture zone, with a total rock layer thickness of 41.05 m.

[0066] Collapse zone void S CD The coal seam mining thickness M is calculated by subtracting the voids in the bending subsidence zone, the voids in the fracture zone, and the surface subsidence S. o The calculation formula is S CD =MS O -S OA -S AB -S BC .

[0067] S4. Based on the multi-pore monitoring data stored in the computer, the Kriging interpolation method is used. The MATLAB software is used to perform interpolation on the three-dimensional dataset of discrete point data to predict the voids at unknown points in the longwall face and generate the three-dimensional void surface and its equation of the mining-induced overburden.

[0068] Mining-induced overburden porosity surface Figure 5 As shown in (a), (b), (c), and (d), the void ratio in the caving zone reaches its maximum at the working face boundary, with a maximum of 3.00 m; the void ratio in the fracture zone reaches its maximum at the boundary of the fractured rock strata, with a maximum of 1.83 m; the void ratio in the bending subsidence zone reaches its maximum at the mining center, with a maximum void ratio of 0.78 m below the key stratum and a maximum void ratio of 0.20 m below the key stratum.

[0069] Once the grouting layer is determined, the grouting volume of the filling space can be calculated based on the aforementioned voids, providing a more scientific basis for determining key grouting parameters.

Claims

1. A method for continuously monitoring a three-dimensional void of a coal mining overburden, characterized in that, Comprise the following steps: S1, collect the coal seam mining thickness and water flowing fractured zone development height information of the measured mining working face, then select the mining overburden above the measured mining working face as the target monitoring area; S2, a plurality of vertical monitoring drill holes (21) are arranged between the surface and the measured working face being mined, the vertical monitoring drill holes (21) are arranged according to the area of the mining working face and the monitoring accuracy; each vertical monitoring drill hole (21) passes through the curved subsidence zone (19), the fractured zone (18) and the caving zone (17) top in turn; then a continuous monitoring device is installed in the vertical monitoring drill hole (21), the continuous monitoring device comprises a sleeve (1) of a hollow sleeve structure and a data acquisition box (16); the sleeve (1) comprises a drilling outer section in the upper half and a drilling inner section in the lower half, a plurality of horizontally arranged cross supports (2) are arranged on both sides of the drilling outer section, the end of the cross support (2) is movably connected with a winding hub (3) through a connecting shaft (12) and a nut piece (13); a plurality of anchor heads (9) are arranged in the drilling inner section and pass through the sleeve (1) in turn and are fixed to the hole wall at different depths in turn, each anchor head (9) is connected with a measuring line (8), a counting hub (6) matched with the number of anchor heads (9) is arranged at the top of the sleeve (1), each counting hub (6) is connected with a rotating speed sensor (7), the number of cross supports (2) is matched with the number of anchor heads (9), the measuring line (8) of each anchor head (9) is changed in direction through a separately matched counting hub (6) and is wound on a separately matched winding hub (3), a counterweight (5) is hung on each winding hub (3) through a counterweight line (4); all rotating speed sensors (7) are connected with the data acquisition box (16) through sensor signal lines (15); a circle of obliquely arranged spring hooks is arranged around the circumference outside the anchor head (9), the spring hook comprises a hook groove, a remote control relay (11) is arranged at the bottom of the hook groove, a hook (10) controlled to stretch and retract through a spring (14) is further arranged in the hook groove; S3, the different anchor heads (9) in each vertical monitoring drill hole (21) are anchored in the surrounding rock wall in the drill hole within the development height range of the water flowing fractured zone determined in S1, the side line connected with the anchor head (9) is fixed to the top opening of the sleeve (1) through the counting hub (6) and the winding hub (3); S4, the rotating speed sensor (7) signal line on the side of the counting hub (6) of the coal mine overburden multi-position separation layer monitoring device is pulled to the hole data data acquisition box (16) and is connected with a computer, each anchor head (9) is taken as a measuring point, and all the separation layer data of the measuring points are recorded and stored in real time in the computer; S5, in order to obtain the evolution diagram of the mining overburden three-dimensional gap with the working face advancing, according to the vertical monitoring drill hole (21) arrangement scheme in S2, steps S2-S4 are repeated, the measuring data of a single vertical monitoring drill hole (21) at different advancing distances in the mining process of the measured working face is monitored and recorded in real time, the separation layer of the adjacent measuring points at the bottom of the fractured zone and above and the surface subsidence monitoring value are analyzed, and the variation law of the gap of a point of the measured working face with the advancing distance is obtained. S6、According to the vertical monitoring borehole arrangement scheme in S2, repeat step S5 to obtain all vertical monitoring borehole data above the measured working face at different advancing distances, store all the vertical monitoring borehole data into the computer as multi-hole monitoring data, use the multi-hole monitoring data stored in the computer to predict the unknown point gap of the mining working face by using the Kriging interpolation method, generate a three-dimensional mining overburden gap space curved surface visualization structure diagram, and obtain the gap space distribution characteristics of the measured working face to provide guidance for grouting and filling position and filling amount design.

2. The method according to claim 1, characterized in that, Select the overburden gap space of the mining area as the target monitoring area, and develop an overburden gap monitoring scheme, which specifically includes the following steps: S101、Determine that the layer where the monitoring borehole terminal hole is located is in the rock layer at the bottom of the fracture zone. According to the numerical simulation and the measured results of the three-zone height of the adjacent working face, the drilling depth is: h b = H d - H c , wherein h b is the drilling depth; H d is the coal seam depth of the working face; and H c is the caving zone height. S102、According to the area of the mining working face, the geological conditions and the monitoring accuracy, determine the spacing, position and number of the boreholes; S103、According to the spacing of the vertical monitoring boreholes (21), arrange the vertical monitoring boreholes (21) along the coal seam strike direction and the coal seam inclination direction through the center point on the surface above the working face.

3. The method according to claim 1, characterized in that, In S2, the arrangement scheme of the vertical monitoring boreholes arranged at intervals along the advancing direction of the working face includes: the strike detection boreholes arranged at intervals along the working face strike direction, and the inclination detection boreholes arranged perpendicularly to the strike monitoring boreholes at the middle position of the working face. The strike detection boreholes start at the working face cut, and end at the main return channel. The starting point and the ending point of the inclination detection boreholes are the main and auxiliary transport gangways, respectively.

4. The method according to claim 1, characterized in that, The specific monitoring steps in S4 include: S401、The anchor head (9) is connected to the wall of the vertical monitoring borehole (21) through the hook (10). When the rock layer where the multiple anchor heads (9) installed in the sleeve (1) moves, the anchor head (9) will move downward with the rock layer, and at the same time, the winding hub (3) releases an equal length of the measuring line and passes through the counting hub (6). The length change of the measuring line (8) is sensed by the rotation speed sensor (7) arranged on the side of the counting hub (6), and an electrical signal is sent to the data acquisition box (16). The interface of the data acquisition box (16) obtains the real-time subsidence amount of the rock layer positioned by different anchor heads (9); S402、Subtract the subsidence amounts of the adjacent rock layers monitored by the adjacent rotation speed sensors (7) of all adjacent anchor heads (9), and the separation amount of the adjacent rock layers in the range of the vertical monitoring borehole is obtained; S403、Obtain the real-time surface subsidence amount by measuring the elevation change of the surface above the vertical monitoring borehole (21) through the real-time dynamic RTK (Real-Time Kinematic) system; S404、Calculate the single-hole gap of the mining overburden rock by using the monitoring results of the rock layer subsidence amount, the adjacent rock layer separation amount and the surface subsidence amount, and obtain the gap distribution between each layer of the mining overburden rock.

5. The method according to claim 4, characterized in that, The single-hole gap of the mining overburden rock specifically includes the gap of the caving zone, the gap of the fractured zone and the gap of the curved subsidence zone. The gap of the curved subsidence zone includes the gap below the key layer and the gap above the key layer. The gap calculation method is: Based on the adjacent rock layer separation amount, the gap above the key layer in the bending subsidence zone is the total separation amount of the rock layer above the key layer in the bending subsidence zone; the gap below the key layer in the bending subsidence zone is the total separation amount of the rock layer below the key layer in the bending subsidence zone; the fracture zone gap is the total separation amount of the rock layer in the fracture zone; the caving zone gap is the mining thickness of the coal seam minus the bending subsidence zone gap, the fracture zone gap and the surface subsidence amount.

6. The method according to claim 1, wherein, The specific steps of generating the three-dimensional mining overburden rock gap space curved surface visual structure diagram are: based on all the computer stored vertical monitoring drill hole (21) data, using the Kriging interpolation method, using MATLAB software to perform interpolation on the three-dimensional data set of discrete point data, predicting the unknown point gap of the mining working face, generating the three-dimensional gap curved surface of the mining overburden rock and its equation.

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