Method for monitoring a roof strata fracture zone

Abstract

The application discloses a roof stratum fracture zone monitoring method, which comprises the following steps: S1, according to the height of the overburden stratum, the overburden stratum is layered in the up-down direction to form a plurality of sub-layers; S2, drilling operation is performed on each sub-layer to form installation holes for installing optical fiber sensors, the optical fiber sensors are installed in the installation holes, the fracture development of each sub-layer is monitored in real time by using the optical fiber sensors, and the development height of the fracture zone is determined; S3, after the installation of the optical fiber sensors is completed, the installation holes are sealed by using concrete slurry to prevent the optical fiber sensors from being interfered by the external environment; and S4, the optical fiber sensors are connected with a monitoring station, the monitoring station can receive, process and analyze the transmission data from the optical fiber sensors, and the development height of the overburden stratum fracture zone is determined. The roof stratum fracture zone monitoring method has the advantages of simple steps and high monitoring efficiency.

Description

Technical Field

[0001] This invention relates to the field of mining technology, specifically to a fiber optic monitoring method for fracture zones in roof strata. Background Technology

[0002] The development height of the fracture zone in the roof of the working face is a key factor to consider in the management of mining pressure, fire prevention and extinguishing in the goaf, and the control of aquifers and surface water. Affected by the geological structure, mining activities and physical and mechanical properties of the rock mass, the harder the rock mass and the thicker the coal seam being mined, the higher the development height of the fracture zone, the more complex the fracture field, the larger the space volume that can accumulate gas, the more water channels, and the higher the degree of danger.

[0003] In related technologies, monitoring of roof fracture zones suffers from issues such as low accuracy, susceptibility to environmental interference, and inability to monitor deep rock strata. Summary of the Invention

[0004] This invention is based on the inventor's discoveries and understanding of the following facts and problems:

[0005] (1) The initial investment in a microseismic monitoring system is substantial, including high-quality sensors, data acquisition equipment, and software licenses. Subsequent operation and maintenance costs are relatively high. Due to factors such as environmental noise and instrument malfunctions, false alarms may occur, or actual microseismic events may fail to be detected. Its spatial resolution is limited, insufficient to clearly depict specific damage paths.

[0006] (2) The borehole inspection method has a limited monitoring range, mainly observing the internal conditions through boreholes, and its observation range is limited to the area around the borehole wall. For the entire monitoring body, the borehole represents only a point or line-shaped local area. In the monitoring of a large area of ​​mine goaf, borehole inspection can only obtain information such as cracks and fractures at the borehole location, and cannot directly reflect the actual state of the vast area between the boreholes. Image interpretation is subjective. Images obtained from the borehole inspection instrument need to be interpreted and analyzed manually. Different operators may interpret the same image differently due to differences in experience, professional knowledge, and other factors. This subjectivity will affect the accuracy and reliability of the monitoring results to a certain extent. Moreover, for images of complex crack networks or fracture zones, it is also difficult to accurately determine information such as the connectivity and development direction of cracks. The borehole inspection method has certain limitations in terms of depth. As the borehole depth increases, the signal transmission of the inspection equipment may be affected, and the image quality will decrease. When the borehole depth exceeds the effective transmission distance of the inspection instrument, it may be impossible to obtain a clear image or no image may be obtained at all.

[0007] (3) Water injection tests are usually conducted in boreholes or specific test wells. They are essentially local tests, and their results can only reflect the fracture situation within a limited range around the test point, and cannot represent the fracture state of the entire area. The pressure-flow data obtained from water injection tests often have multiple possible interpretations. The same pressure drop and flow rate change may be caused by different fracture distributions, fracture connectivity, and other factors.

[0008] The present invention aims to at least partially solve one of the technical problems in the related art.

[0009] Therefore, embodiments of the present invention propose an optical fiber monitoring method for the fracture zone of the top strata, which has high monitoring accuracy, is not easily affected by environmental interference, and is capable of monitoring deep rock strata.

[0010] The method for monitoring fracture zones in the overlying strata according to an embodiment of the present invention includes: S1: dividing the overlying strata into multiple sub-layers along the vertical direction according to the height of the overlying strata; S2: drilling holes in each sub-layer to form mounting holes for installing fiber optic sensors, and installing the fiber optic sensors in each mounting hole to monitor the fracture development of each sub-layer in real time to determine the development height of the fracture zone; S3: sealing the mounting holes with concrete grout after the fiber optic sensors are installed to prevent interference from the external environment; S4: connecting the fiber optic sensors to a monitoring station so that the monitoring station can receive, process, and analyze the transmitted data from the fiber optic sensors to determine the development height of the fracture zone in the overlying strata.

[0011] The method for monitoring the fracture zone of the overlying strata in this embodiment of the invention includes steps S1-S4, which enable real-time monitoring of the overlying strata, accurately determine the height of the fracture zone, ensure the reliability and stability of data acquisition, reduce the occurrence of false alarms, and provide accurate and reliable monitoring and processing results that can comprehensively reflect the fracture state of the overlying strata.

[0012] In some embodiments, in step S2, a PVC pipe is used as a carrier for the fiber optic sensor, and the fiber optic sensor is transported to the mounting hole through the PVC pipe.

[0013] In some embodiments, there are multiple PVC pipes arranged sequentially along their axial direction, and the fiber optic sensor is installed on the outer periphery of the multiple PVC pipes.

[0014] In some embodiments, the fiber optic sensor is bonded to the outer circumferential surface of the PVC pipe with epoxy resin adhesive, and the fiber optic sensor is secured to the outer circumferential side of the PVC pipe with nylon cable ties.

[0015] In some embodiments, the fiber optic sensor includes a first fiber optic sensor and a second fiber optic sensor, both of which are disposed on the outer periphery of the PVC pipe. The first fiber optic sensor is disposed above the second fiber optic sensor. The first fiber optic sensor is used to detect the compressive strain of the sublayer, and the second fiber optic sensor is used to detect the tensile strain of the same sublayer.

[0016] In some embodiments, in step S2, the mounting hole includes a first segment and a second segment in communication, the first segment extending upward from the top of the roadway and inclined toward the goaf, the second segment extending along the length direction of the goaf and at least a portion of the second segment being located above the goaf, at least one second segment being provided in each sub-layer, and the fiber optic sensor being disposed in the second segment.

[0017] In some embodiments, there are multiple mounting holes, which are arranged in multiple rows along the vertical direction, and each row includes several mounting holes spaced apart along the width direction of the goaf.

[0018] In some embodiments, in step S3, the parameters of the concrete grout are determined according to the rock properties of the sublayers at different strata, the concrete grout is proportioned according to the determined parameters, and the proportioned concrete grout is injected into the mounting hole of the corresponding sublayer to seal the mounting hole.

[0019] In some embodiments, in step S4, the monitoring station and the fiber optic sensor are connected by an optical cable, and a coolant is sprayed onto the outer periphery of the optical cable to cool it down.

[0020] In some embodiments, in step S4, the monitoring station plots the internal strain curve of the mounting hole based on the monitoring results of the fiber optic sensor, so that when the strain value exceeds 600 microstrain, the sublayer generates cracks. Attached Figure Description

[0021] Figure 1 This is a flowchart of a method for monitoring fracture zones in the roof strata according to an embodiment of the present invention.

[0022] Figure 2 This is the orientation profile of the monitoring system of the roof rock fracture zone monitoring method according to an embodiment of the present invention.

[0023] Figure 3 This is a top view of the monitoring system of the roof rock fracture zone monitoring method according to an embodiment of the present invention.

[0024] Figure 4 This is a schematic diagram of the installation of the fiber optic sensor and PVC pipe in the roof rock fracture zone monitoring method of this invention.

[0025] Figure 5 This is a right view of the fiber optic sensor and PVC pipe used in the roof rock fracture zone monitoring method according to an embodiment of the present invention.

[0026] Method for monitoring fracture zones in the top strata 100;

[0027] Overlying stratum 1; Sub-layer 11; Installation hole 12; First section 13; Second section 14; Goaf 15; Coal pillar 16; Fiber optic sensor 2; First fiber optic sensor 21; Second fiber optic sensor 22; PVC pipe 3; Roadway 4; Support structure 5; Longwall face 6; Nylon cable tie 7. Detailed Implementation

[0028] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0029] The following describes a method 100 for monitoring fracture zones in the top strata of the present invention with reference to the accompanying drawings.

[0030] like Figures 1-5 As shown, the roof rock fracture zone monitoring method 100 according to an embodiment of the present invention includes steps S1-S4.

[0031] S1: Based on the height of the overlying rock layer 1, the overlying rock layer 1 is layered vertically to form multiple sublayers 11. Specifically, as follows... Figure 1 and Figure 2 As shown, based on the height and distribution characteristics of the overlying rock layer 1 in the vertical direction (up and down direction), it is divided into multiple sub-layers 11.

[0032] S2: Drill holes in each sublayer 11 to form mounting holes 12 for installing fiber optic sensors 2. Install the fiber optic sensors 2 in each mounting hole 12 to monitor the fracture development of each sublayer 11 in real time, thereby determining the fracture zone development height. Specifically, as... Figures 1-3 As shown, for each sub-layer 11, a directional drilling rig is used to perform precise drilling operations on the overlying rock layer 1 of the tunnel 4 to form mounting holes 12 for installing fiber optic sensors 2. The position, depth, and inclination angle of the mounting holes 12 need to be designed according to the specific conditions of the sub-layer 11 to ensure that the fiber optic sensors 2 can accurately and stably monitor the development of fractures. Then, the fiber optic sensors 2 are installed in each mounting hole 12, and the development of fractures in each sub-layer 11 is monitored in real time using fiber optic sensing technology to determine the development height and trend of fracture zones.

[0033] S3: After the fiber optic sensor 2 is installed, the mounting hole 12 is sealed with concrete grout to prevent interference from the external environment. Specifically, after the fiber optic sensor 2 is installed, in order to prevent interference from the external environment (such as moisture, dust, temperature, etc.) and affect the accuracy and stability of the monitoring data, the mounting hole 12 is sealed with concrete grout, thereby ensuring the monitoring efficiency of the fiber optic sensor 2.

[0034] S4: Fiber optic sensor 2 is connected to the monitoring station, enabling the station to receive, process, and analyze the transmitted data from it to accurately determine the development height of the fracture zone in the overlying stratum 1. Specifically, by connecting fiber optic sensor 2 to the monitoring station and establishing a data transmission channel, the monitoring station can receive, process, and analyze the transmitted data in real time to determine the development height and trend of the fracture zone in the overlying stratum 1, providing a scientific basis for the management and maintenance of the overlying stratum 1. Simultaneously, the monitoring station can also store and back up the monitoring data for subsequent data analysis and research.

[0035] The roof rock strata fracture zone monitoring method 100 of this invention includes steps S1-S4. Through fiber optic sensor 2, continuous monitoring of the overlying rock stratum 1 is achieved. When the overlying rock stratum 1 collapses, the monitoring station processes the transmitted data from the fiber optic sensor 2 to generate a fiber optic strain curve. This curve clearly reflects the changes within the rock stratum, thus accurately determining the height of the fracture zone. Compared to microseismic monitoring systems, the fiber optic sensor 2 in the roof rock strata fracture zone monitoring method 100 of this invention is less susceptible to electromagnetic interference, temperature changes, and other environmental factors, improving the reliability and stability of data acquisition and reducing the incidence of false alarms. Furthermore, compared to borehole inspection monitoring, the processing results of the roof rock strata fracture zone monitoring method 100 of this invention are accurate and reliable, and the image quality does not decrease with increasing depth. Finally, the sensor setup within each sub-layer 11, compared to water injection tests, allows the roof rock strata fracture zone monitoring method 100 of this invention to comprehensively monitor the overlying rock stratum 1, fully reflecting the fracture state of the overlying rock stratum 1.

[0036] In some embodiments, in step S2, a PVC pipe 3 is used as a carrier for the fiber optic sensor 2, and the fiber optic sensor 2 is transported into the mounting hole 12 through the PVC pipe 3. Specifically, as shown... Figures 2-5 As shown, the fiber optic sensor 2 is installed on the outer periphery of the PVC pipe 3, and then the PVC pipe 3 containing the fiber optic sensor 2 is fed into the mounting hole 12 by a conveying tool, thereby providing a transportation basis for the fiber optic sensor 2, improving the installation efficiency of the fiber optic sensor 2, and reducing the transportation cost of the fiber optic sensor 2.

[0037] In some embodiments, there are multiple PVC pipes 3, which are arranged sequentially along their axial direction, and the fiber optic sensor 2 is mounted on the outer periphery of the multiple PVC pipes 3. Specifically, as shown in the figure... Figure 4 and Figure 5 As shown, there are multiple PVC pipes 3 arranged sequentially along the left-right direction, and the sum of the lengths of the multiple PVC pipes 3 is greater than the depth of the mounting hole 12 to ensure sufficient space for operation and adjustment during transportation. The fiber optic sensor 2 is installed and fixed on the outer periphery of the multiple PVC pipes 3, allowing the fiber optic sensor 2 to be transported through the multiple PVC pipes 3. The arrangement of the multiple PVC pipes 3 can be flexibly adjusted according to specific monitoring needs and the distribution of the overlying rock layer 1, so as to achieve accurate monitoring of the overlying rock layer 1 at different areas and depths.

[0038] In some embodiments, the fiber optic sensor 2 is bonded to the outer periphery of the PVC pipe 3 with epoxy resin adhesive, and is secured to the outer periphery of the PVC pipe 3 with nylon cable ties 7. Specifically, as shown... Figure 4 and Figure 5 As shown, epoxy resin adhesive is used as a bonding agent to bond the fiber optic sensor 2 to the outer circumferential surface of each PVC pipe 3. The epoxy resin adhesive not only has excellent bonding strength and durability, but also ensures a good seal between the fiber optic sensor 2 and the PVC pipe 3, preventing interference or damage to the sensor from the external environment. Furthermore, due to the high strength, wear resistance, and ease of operation of the nylon cable ties 7, the fiber optic sensor 2 is additionally secured using the nylon cable ties 7, effectively preventing the sensor from loosening or falling off during use, and enhancing the stability of the fiber optic sensor 2 on the PVC pipe 3. Therefore, the dual fixing method of epoxy resin adhesive and nylon cable ties 7 not only ensures the firm installation of the fiber optic sensor 2 on the PVC pipe 3, but also effectively prevents the sensor from loosening or falling off during use, improving the installation efficiency of the fiber optic sensor 2 on the PVC pipe 3.

[0039] In some embodiments, the fiber optic sensor 2 includes a first fiber optic sensor 21 and a second fiber optic sensor 22. Both the first fiber optic sensor 21 and the second fiber optic sensor 22 are disposed on the outer periphery of the PVC pipe 3. The first fiber optic sensor 21 is disposed above the second fiber optic sensor 22. The first fiber optic sensor 21 is used to detect the compressive strain of the sublayer 11, and the second fiber optic sensor 2 is used to detect the tensile strain of the same sublayer 11. Specifically, as shown... Figures 2-5As shown, the first fiber optic sensor 21 is installed above the PVC pipe 3. Since compressive strain usually occurs when the rock layer is subjected to compression from above or surrounding rock masses, the first fiber optic sensor 21 can detect the compressive strain of the sublayer 11, accurately monitoring the stress changes of the rock layer under pressure and providing crucial compression deformation data. The second fiber optic sensor 2 is installed below the PVC pipe 3. Since tensile strain usually occurs when the rock layer is subjected to tensile force or tensile stress generated by the movement of surrounding rock masses, the second fiber optic sensor 2 can detect the tensile strain of the sublayer 11. Thus, by setting the first fiber optic sensor 21 and the second fiber optic sensor 2, compressive and tensile strain data of the same sublayer 11 can be acquired simultaneously, accurately providing information on rock layer deformation and stress, and improving the accuracy of the detection results.

[0040] In some embodiments, in step S2, the mounting hole 12 includes a first segment 13 and a second segment 14 connected in a manner. The first segment 13 extends upward from the top plate of the roadway 4 and slopes towards the goaf 15. The second segment 14 extends along the length of the goaf 15, and at least a portion of the second segment 14 is located above the goaf 15. At least one second segment 14 is provided in each sub-layer 11, and the fiber optic sensor 2 is disposed within the second segment 14. Specifically, as shown... Figure 2 As shown, the first segment 13 extends upward from the roof of the mining roadway 4 and slopes towards the goaf 15, reducing the resistance during drilling, improving the drilling efficiency of the first segment 13, and reducing the drilling cost of the first segment 13. The second segment 14 extends in the left and right direction and is located above the goaf 15, so that the second segment 14 can cover the height range of the entire fracture zone, and there is at least one second segment 14 in each sub-layer 11, which ensures the continuity and comprehensiveness of monitoring and helps to detect the strain state of the rock strata at different depths and locations.

[0041] In some embodiments, there are multiple mounting holes 12, arranged in multiple rows along the vertical direction. Each row includes several mounting holes 12 spaced apart along the width direction of the goaf 15. Specifically, the second segments 14 of the multiple mounting holes 12 are arranged in multiple rows along the vertical direction, and each sub-layer 11 has at least one row of mounting holes 12, thereby ensuring that monitoring can be performed by the fiber optic sensor 2 on sub-layers 11 at different heights. Each row includes several second segments 14 spaced apart along the front-back direction, thereby ensuring that the monitoring range of the fiber optic sensor 2 can cover the entire width of the goaf 15, improving the accuracy and efficiency of monitoring.

[0042] In some embodiments, in step S3, the parameters of the concrete grout are determined according to the rock properties of different sub-layers 11. The concrete grout is then proportioned according to the determined parameters and injected into the mounting holes 12 corresponding to the sub-layers 11 to seal the mounting holes 12. Specifically, the parameters of the concrete grout are determined according to the rock properties of different layers on site. The parameters can be elastic modulus, Poisson's ratio, tensile strength, etc. Then, concrete grout with different proportions is injected in sections according to different layers on site. The proportioned concrete grout is injected into the opening of the mounting holes 12 corresponding to the sub-layers 11. After the grout has completely solidified, the opening of the mounting holes 12 is sealed to prevent external substances such as water and mud from entering the mounting holes 12, avoiding damage to the internal fiber optic sensor 2, reducing the influence of external factors on the monitoring results, ensuring that the monitoring equipment such as the fiber optic sensor 2 can accurately capture the stress changes inside the rock layer, and ensuring the accuracy of the monitoring results of the fiber optic sensor 2.

[0043] In some embodiments, in step S4, the monitoring station and the fiber optic sensor 2 are connected by an optical cable, and a coolant is sprayed onto the outer periphery of the optical cable to cool it down. Specifically, the fiber optic sensor 2 at the opening of the mounting hole 12 is thermally fused to a dedicated long-distance communication optical cable and protected with a junction box, and then led to the ground and connected to the monitoring station. A coolant is sprayed onto a localized area of ​​the optical cable, approximately 100 cm long, at the opening of the mounting hole 12 to cool it down. The coolant can quickly absorb the heat from the surface of the optical cable, thereby reducing the temperature of the optical cable, reducing the loss of optical signals within the optical cable, and improving the transmission efficiency of the optical cable.

[0044] In some embodiments, in step S4, the monitoring station plots the internal strain curve of the mounting hole 12 based on the monitoring results of the fiber optic sensor 2, so that when the strain value exceeds 600 microstrain, a fracture is generated in the sublayer 11. Specifically, the monitoring station can plot the internal strain curve of the borehole based on the monitoring results. When the rock strata collapse and fractures are generated within the rock strata, the strain generated by the fiber optic sensor 2 in the fracture zone is greater than 600 microstrain. Therefore, the value corresponding to 600 microstrain on the fiber optic strain curve can be used as the basis for judging the development height of the fracture zone in the roof.

[0045] The specific working process of the roof rock fracture zone monitoring method 100 in this embodiment of the invention is as follows:

[0046] (1) Analyze the borehole columnar section of the target area and statistically analyze the thickness of the overlying strata, lithology, degree of joint and fracture development, and physical and mechanical parameters of coal and rock.

[0047] (2) Based on the distribution characteristics of the overlying strata 1 and the construction conditions of the tunnel 4, avoid the damage of the collapse zone to the fiber optic sensor 2, reduce the impact of the collapse zone on the fiber optic monitoring results of the fracture zone, and determine the drilling inclination angle of the fiber optic monitoring borehole in the fracture zone.

[0048] (3) Calculate the height of the fracture zone using empirical formulas to ensure that the height of the fiber optic sensor 2 can exceed the height of the completely covered fracture zone.

[0049] (4) In order to fully monitor the fracture zone, the fiber optic drilling slope section is perpendicular to the working face, and the horizontal section is parallel to the working face. Horizontal sections are arranged at different layers to measure the fracture development at different rock layer locations.

[0050] (5) Bury optical fibers and use PVC as a carrier to push the optical fibers into the hole.

[0051] (6) Apply epoxy resin glue to both sides of the single PVC pipe 3, place the optical fiber on the glue on the outside of the PVC pipe 3, and apply glue again. After the glue has cured, tie it to the outside of the PVC pipe 3 with nylon cable ties at certain intervals.

[0052] (7) The first fiber optic sensor 21 is located on the upper surface of the PVC pipe 3 to monitor compressive strain, and the second fiber optic sensor 2 is located on the lower surface of the PVC pipe 3 to monitor tensile strain. The tensile and compressive strains of the rock can be monitored simultaneously.

[0053] (8) Determine the parameters of the concrete grout, such as elastic modulus, Poisson's ratio, and tensile strength, according to the rock properties of different layers on site. Grout different proportions of concrete grout in sections according to the sub-layer 11 of different layers on site. After the grout solidifies, seal the opening.

[0054] (9) The fiber optic sensor 2 at the aperture is thermally fused with a dedicated long-distance communication optical cable and protected with a junction box, and then led to the ground to establish a monitoring station.

[0055] (10) Cool the optical cable by spraying a coolant at the borehole opening for a local area of ​​about 100cm. This will determine the monitoring distance of the optical fiber from the borehole opening to the bottom of the borehole.

[0056] (11) Draw the strain curve inside the borehole based on the monitoring results.

[0057] (12) Determination of the height of the fracture zone: When the overlying rock layer 1 collapses and fractures are generated in the rock layer, the fiber strain in the fracture zone is generally greater than 600 microstrain. Therefore, the value corresponding to 600 microstrain in the fiber strain curve is used as the basis for judging the development height of the fracture zone in the top plate.

[0058] In summary, the roof rock fracture zone monitoring method 100 of this invention has the following advantages:

[0059] (1) The designed fiber optic sensor 2 for the fracture zone of the top stratum can realize continuous monitoring of the strain of the fracture zone stratum and the development height of the fracture zone.

[0060] (2) By precisely arranging the fiber optic sensor 2 within the mounting hole 12 and using a combination of PVC pipe 3 and nylon cable ties 7 for fixation, the stability and accuracy of the fiber optic sensor 2 in different rock strata are ensured. When the overlying rock stratum 1 collapses, the fiber optic strain curve can clearly reflect the changes within the rock stratum, thereby accurately determining the height of the fracture zone with a resolution at the millimeter level. Compared to related technologies, the fiber optic sensor 2 is less susceptible to electromagnetic interference, temperature changes, and other environmental factors, greatly improving the reliability and stability of data acquisition and reducing the incidence of false alarms.

[0061] (3) This invention provides a method for identifying fracture zones in the roof strata, achieving a process flow that is simple to install sensors and has a wide monitoring range. Using a directional drilling rig for drilling, combined with segmented grouting technology, not only speeds up the construction progress but also ensures the installation quality of the fiber optic sensor 2. Throughout the process, no complex equipment or technical support is required, reducing the difficulty of construction.

[0062] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0063] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0064] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0065] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0066] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0067] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for monitoring fracture zones in roof strata, characterized in that, include: S1: Based on the height of the overlying rock layer, the overlying rock layer is processed into multiple sub-layers along the vertical direction; S2: Drill holes in each sublayer to form mounting holes for installing fiber optic sensors. Install the fiber optic sensors in each mounting hole to monitor the fracture development of each sublayer in real time and determine the development height of the fracture zone. S3: After the fiber optic sensor is installed, use concrete grout to seal the mounting hole to prevent external environmental interference to the fiber optic sensor. S4: The fiber optic sensor is connected to the monitoring station, enabling the monitoring station to receive, process, and analyze the transmitted data from the fiber optic sensor in order to determine the development height of the fracture zone in the overlying strata. The specific working process of the method for monitoring fracture zones in the top strata is as follows: (1) Analyze the borehole columnar section of the target area and statistically analyze the layered distribution thickness, lithology, degree of joint and fracture development, and physical and mechanical parameters of coal and rock in the overlying strata. (2) Based on the distribution characteristics of the overlying strata and the tunnel construction conditions, avoid the damage of the collapse zone to the fiber optic sensor, reduce the impact of the collapse zone on the fiber optic monitoring results of the fracture zone, and determine the drilling inclination angle of the fiber optic monitoring borehole in the fracture zone. (3) Calculate the height of the fracture zone using empirical formulas to ensure that the fiber optic sensor can be placed at a height that covers the entire fracture zone; (4) In order to fully monitor the fracture zone, the fiber optic drilling slope section is perpendicular to the working face, and the horizontal section is parallel to the working face. Horizontal sections are arranged at different layers to measure the fracture development at different rock layer locations. (5) Bury optical fibers and use PVC pipes as carriers to push optical fibers into the holes; (6) Apply epoxy resin glue to both sides of the single PVC pipe, place the optical fiber on the glue on the outside of the PVC pipe, and apply glue again. After the glue has cured, tie it to the outside of the PVC pipe with nylon cable ties at certain intervals. (7) The fiber optic sensor includes a first fiber optic sensor and a second fiber optic sensor. The first fiber optic sensor is located on the upper surface of the PVC pipe to monitor compressive strain, and the second fiber optic sensor is located on the lower surface of the PVC pipe to monitor tensile strain. It can monitor the tensile and compressive strain of the rock at the same time. (8) Determine the parameters of the concrete grout, such as elastic modulus, Poisson's ratio, and tensile strength, according to the rock properties of different layers on site. Grout different proportions of concrete grout in sections according to the sub-layers of different layers on site. After the grout solidifies, seal the opening. (9) The fiber optic sensor at the aperture is thermally fused with a dedicated long-distance communication optical cable and protected with a junction box, and then led to the ground to establish a monitoring station; (10) Cool the optical cable by spraying a condenser at the borehole opening for a local area of ​​100cm to determine the monitoring distance of the optical fiber from the borehole opening to the bottom of the borehole. (11) Draw the strain curve inside the borehole based on the monitoring results; (12) Determination of the height of the fracture zone: When the overlying rock layer collapses and fractures are generated in the rock layer, the fiber strain in the fracture zone is greater than 600 microstrain. The value corresponding to 600 microstrain on the fiber strain curve is used as the basis for judging the development height of the fracture zone in the top plate.

2. The method for monitoring fracture zones in roof strata according to claim 1, characterized in that, The number of PVC pipes is multiple, and the multiple PVC pipes are arranged sequentially along their axial direction. The fiber optic sensor is installed on the outer periphery of the multiple PVC pipes.

3. The method for monitoring fracture zones in roof strata according to claim 1, characterized in that, Both the first fiber optic sensor and the second fiber optic sensor are located on the outer periphery of the PVC pipe, with the first fiber optic sensor positioned above the second fiber optic sensor. The first fiber optic sensor is used to detect the compressive strain of the sublayer, and the second fiber optic sensor is used to detect the tensile strain of the same sublayer.

4. The method for monitoring fracture zones in roof strata according to claim 1, characterized in that, In step S2, the mounting hole includes a first section and a second section connected in the ground. The first section extends upward from the top plate of the roadway and is inclined toward the goaf. The second section extends along the length direction of the goaf and at least a portion of the second section is located above the goaf. At least one second section is provided in each sub-layer, and the fiber optic sensor is located in the second section.

5. The method for monitoring fracture zones in roof strata according to claim 1, characterized in that, The mounting holes are multiple, and the multiple mounting holes are arranged in multiple rows along the vertical direction. Each row includes several mounting holes spaced apart along the width direction of the goaf.

6. The method for monitoring fracture zones in roof strata according to claim 1, characterized in that, In step S3, the parameters of the concrete grout are determined according to the rock properties of the sub-layers at different strata. The concrete grout is then proportioned according to the determined parameters, and the proportioned concrete grout is injected into the installation hole corresponding to the sub-layer to seal the installation hole.

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