Distributed optical fiber monitoring method for section coal pillar deformation

Abstract

The invention provides a section coal pillar deformation distributed optical fiber monitoring method, which comprises the following steps that a preset route for arranging optical fibers is planned on the side surface of a coal pillar, optical fiber grooves are formed in the side surface of the coal pillar along the preset route, the extension direction of the optical fiber grooves is consistent with the horizontal direction, and the number of the optical fiber grooves is multiple. The plurality of optical fiber grooves are arranged at intervals in the height direction of the coal pillar, a gap is formed between the optical fiber groove, adjacent to the top of the coal pillar, in the plurality of optical fiber grooves and the top of the coal pillar, a gap is formed between the optical fiber groove, adjacent to the bottom of the coal pillar, in the plurality of optical fiber grooves and the bottom of the coal pillar, optical fiber monitoring assemblies are arranged in the optical fiber grooves, and the optical fiber grooves are blocked; part of the monitoring optical fiber is reserved on the outer side of the optical fiber groove and connected with optical fiber demodulation equipment, and inversion is carried out according to the collected optical fiber monitoring data so as to obtain the strain change of the section coal pillar in the range of the strain sensing optical fiber. The section coal pillar deformation distributed optical fiber monitoring method has the advantages of being convenient to implement and high in accuracy.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber monitoring technology, and in particular to a distributed optical fiber monitoring method for segment coal pillar deformation. Background Art

[0002] The section coal pillar is a part of the coal body that is retained in order to divide different mining sections during the coal mining process. It mainly serves to isolate the mining activities in adjacent sections, isolate the adverse effects of roof subsidence and rock movement caused by the mining of adjacent working faces, and avoid damage to the adjacent sections that are being mined or prepared for mining. In the process of coal mining, there are risks of spontaneous combustion, gas accumulation and leakage, and local water outflow in the goaf. The section coal pillar can prevent oxygen from entering the goaf to a certain extent, and reduce the possibility of spontaneous combustion of coal blocks left in the goaf. At the same time, the section coal pillar is also required to prevent gas and water in the goaf from gushing into the working face being mined.

[0003] Among the related technologies, surface convergence deformation monitoring is greatly affected by human and environmental factors, laser ranging is greatly affected by dust and water mist, and tape measurement is greatly affected by human readings. It is impossible to continuously and long-term monitor the deformation of the coal pillar in a large range; the total station measurement operation is complicated and requires professional technicians to process the data. During measurement, it is greatly affected by the environment in the tunnel (such as light, dust, water mist, etc.), and long-term continuous monitoring is impossible; the installation process of the delamination meter has many steps. When the shallow and deep parts deform simultaneously, the deformation of the coal pillar cannot be calculated normally. In addition, it is easy to be affected by the environment in the borehole (such as coal and rock crushing) and fail. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0005] To this end, an embodiment of the present invention proposes a distributed optical fiber monitoring method for segmental coal pillar deformation. The distributed optical fiber monitoring method for segmental coal pillar deformation has the advantages of easy implementation and high accuracy.

[0006] The distributed optical fiber monitoring method for segment coal pillar deformation according to an embodiment of the present invention comprises the following steps:

[0007] S1. Plan and arrange the preset route of the optical fiber on the side of the coal pillar;

[0008] S2. On the side of the coal pillar, an optical fiber groove is opened along the preset route, the extension direction of the optical fiber groove is consistent with the horizontal direction, there are multiple optical fiber grooves, the multiple optical fiber grooves are arranged at intervals along the height direction of the coal pillar, and there is a gap between the optical fiber groove adjacent to the top of the coal pillar and the top of the coal pillar, and there is a gap between the optical fiber groove adjacent to the bottom of the coal pillar and the bottom of the coal pillar;

[0009] S3, arranging an optical fiber monitoring component in the optical fiber groove, and sealing the optical fiber groove to fix the optical fiber monitoring component in the optical fiber groove;

[0010] S4, reserving a portion of the monitoring optical fiber outside the optical fiber groove and connecting it to an optical fiber demodulation device so as to collect data from the monitoring optical fiber;

[0011] S5. Inversion is performed based on the collected optical fiber monitoring data to obtain the strain variation of the section coal pillar along the range of the strain sensing optical fiber.

[0012] The distributed optical fiber monitoring method for segmented coal pillar deformation of an embodiment of the present invention can place an optical fiber monitoring component in an optical fiber groove opened on the side of the coal pillar, and seal the optical fiber monitoring component in the optical fiber groove, so that the sealing material in the optical fiber groove and the coal pillar form a whole, thereby being able to continuously and in real time monitor the deformation of the coal pillar, ensuring the measurement accuracy of the optical fiber monitoring component, and further being able to accurately capture the strain changes of the coal pillar.

[0013] In some embodiments, the optical fiber groove includes a first groove section, a second groove section, and a third groove section connected in sequence, the second groove section is arranged through the coal pillar along the width direction of the coal pillar, and the connection between the first groove section and the second groove section and between the second groove section and the third groove section are both arc sections, and the radius of the arc section is greater than 100 mm.

[0014] In some embodiments, the optical fiber monitoring assembly includes a first monitoring optical fiber and an optical fiber fixing piece, the first monitoring optical fiber is connected to the optical fiber fixing piece, and an extension direction of the optical fiber fixing piece is consistent with an extension direction of the optical fiber groove.

[0015] In some embodiments, the optical fiber monitoring assembly further comprises a first connector, a first end of the first connector is connected to the optical fiber fixing member, a second end of the first connector is connected to the first monitoring optical fiber, and the first monitoring optical fiber is spaced apart from the optical fiber fixing member.

[0016] In some embodiments, the fiber optic monitoring assembly also includes a second monitoring optical fiber and a second connecting member, the second monitoring optical fiber is consistent with the extension direction of the optical fiber groove, and is located between two adjacent optical fiber grooves in the height direction of the coal pillar, the second connecting member is used to connect the second monitoring optical fiber and the side of the coal pillar, there are multiple second connecting members, and the multiple second connecting members are arranged at intervals along the extension direction of the optical fiber fixing member, and the distance between two adjacent second connecting members is less than the length of the second monitoring optical fiber between the two connected second connecting members.

[0017] In some embodiments, in step S3, grouting and plugging are performed in the second trench section by segmented grouting.

[0018] In some embodiments, in step S4, before collecting data, a rebound tester is used to detect the plugging area of ​​the optical fiber groove to ensure that the plugging material in the optical fiber groove forms a whole with the coal pillar.

[0019] In some embodiments, in step S4, the portion of the optical fiber outside the optical fiber groove that is connected to the optical fiber demodulation device is wrapped with a plastic hose.

[0020] In some embodiments, the number of the first monitoring optical fiber is one, and the first monitoring optical fiber is connected in series with a plurality of the optical fiber grooves.

[0021] In some embodiments, there are a plurality of first monitoring optical fibers, and at least one of the first monitoring optical fibers is disposed in one of the optical fiber grooves. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a construction schematic diagram of a distributed optical fiber monitoring method for segment coal pillar deformation according to an embodiment of the present invention.

[0023] Figure 2 yes Figure 1 The AA direction schematic diagram is shown in .

[0024] Figure 3 It is a cross-sectional schematic diagram of the second slot section of the distributed optical fiber monitoring method for segment coal pillar deformation according to an embodiment of the present invention.

[0025] Figure 4 It is a schematic diagram of the first monitoring optical fiber arrangement of the distributed optical fiber monitoring method for segment coal pillar deformation according to an embodiment of the present invention.

[0026] Figure 5 It is a schematic diagram of the arrangement of monitoring optical fibers of a distributed optical fiber monitoring method for segment coal pillar deformation according to another embodiment of the present invention.

[0027] Reference numerals:

[0028] 100. Coal pillar,

[0029] 1. Optical fiber slot, 11. First slot section, 12. Second slot section, 13. Third slot section,

[0030] 2. Optical fiber monitoring assembly, 21. First monitoring optical fiber, 22. Optical fiber fixing member, 23. First connecting member, 24. Second monitoring optical fiber, 25. Second connecting member,

[0031] 3. Fiber optic demodulation equipment. DETAILED DESCRIPTION

[0032] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0033] like Figure 1-Figure 5 As shown, the distributed optical fiber monitoring method for deformation of a coal pillar 100 in a section according to an embodiment of the present invention comprises the following steps:

[0034] S1. Plan and arrange the preset route of the optical fiber on the side of the coal pillar 100. It is understandable that according to the distribution of the coal pillar 100 and the underground construction environment, surveying tools such as a total station, a measuring robot, etc. can be used to survey the coal pillar 100. Through accurate measurement and design software, the structural characteristics and monitoring requirements of the coal pillar 100 can be comprehensively considered, and the most suitable optical fiber monitoring route can be planned to improve the accuracy and efficiency of the optical fiber layout.

[0035] S2. On the side of the coal pillar 100, an optical fiber groove 1 is opened along a preset route. The extension direction of the optical fiber groove 1 is consistent with the horizontal direction. There are multiple optical fiber grooves 1. The multiple optical fiber grooves 1 are arranged at intervals along the height direction of the coal pillar 100. There is a gap between the optical fiber groove 1 adjacent to the top of the coal pillar 100 and the top of the coal pillar 100 among the multiple optical fiber grooves 1, and there is a gap between the optical fiber groove 1 adjacent to the bottom of the coal pillar 100 and the bottom of the coal pillar 100.

[0036] It is understandable that if Figure 1-Figure 3 As shown, the optical fiber groove 1 is opened on the side wall of the coal pillar 100, that is, the optical fiber groove 1 is opened on the left and right side walls of the coal pillar 100, and the optical fiber groove 1 is opened in the width direction of the coal pillar 100 (that is, Figure 1 A through hole is formed through the coal pillar 100 (in the left and right directions), and the two ends of the through hole are respectively connected to the left and right side walls of the coal pillar 100 and two optical fiber grooves 1 at the same level, thereby forming a complete optical fiber groove 1. A drilling machine, an electric drill, a groove cutting tool and safety protection equipment can be used to groove the coal pillar 100.

[0037] That is to say, the opening of the optical fiber slot 1 provides a fixed space for the optical fiber monitoring assembly 2, ensuring the accuracy of monitoring. The gap design between the top and bottom of the coal pillar 100 and the optical fiber slot 1 facilitates the opening of the optical fiber slot 1 and prevents the top and bottom of the coal pillar 100 from interfering with the construction equipment during the slotting process.

[0038] S3. Arrange the optical fiber monitoring assembly 2 in the optical fiber groove 1, and seal the optical fiber groove 1 to fix the optical fiber monitoring assembly 2 in the optical fiber groove 1. It can be understood that the optical fiber monitoring assembly 2 is placed in the optical fiber groove 1, and the optical fiber groove 1 is filled with sealing material to fix the optical fiber.

[0039] That is to say, the fixation of the optical fiber monitoring assembly 2 makes data collection more stable and reliable. The plugging material provides additional protection for the optical fiber, preventing the intrusion of dust and moisture, thereby affecting the monitoring results. Among them, the plugging material can be quick-setting high-strength mortar, resin, silica gel, etc.

[0040] S4, reserve part of the monitoring optical fiber outside the optical fiber slot 1 and connect it to the optical fiber demodulation device 3 to collect data on the monitoring optical fiber. It can be understood that one end of the monitoring optical fiber is connected to the demodulation device, and the other end is reserved outside the optical fiber slot 1 for data collection. Among them, the optical fiber adjustment device includes an optical time domain reflectometer (OTDR), a connecting line, and a data acquisition computer. Thus, the connection optical fiber demodulation device 3 can monitor the state of the optical fiber and the strain change of the coal pillar 100 in real time.

[0041] S5. Inversion is performed based on the collected optical fiber monitoring data to obtain the strain change within the strain sensing optical fiber of the section coal pillar 100. It can be understood that the strain distribution of the coal pillar 100 is obtained by processing and inverting the collected data through data analysis software. In other words, data inversion can provide detailed information on the strain of the coal pillar 100, which is helpful to judge the stability and safety of the coal pillar 100.

[0042] Therefore, the distributed optical fiber monitoring method for deformation of a segmented coal pillar 100 according to an embodiment of the present invention can place the optical fiber monitoring component 2 in the optical fiber groove 1 opened on the side of the coal pillar 100, and seal the optical fiber monitoring component 2 in the optical fiber groove 1, so that the sealing material in the optical fiber groove 1 forms a whole with the coal pillar 100, thereby being able to continuously and in real time monitor the deformation of the coal pillar 100, ensuring the measurement accuracy of the optical fiber monitoring component 2, and further being able to accurately capture the strain changes of the coal pillar 100.

[0043] In some embodiments, the optical fiber groove 1 includes a first groove section 11, a second groove section 12 and a third groove section 13 connected in sequence, the second groove section 12 is arranged to penetrate the coal pillar 100 along the width direction of the coal pillar 100, and the connection between the first groove section 11 and the second groove section 12 and between the second groove section 12 and the third groove section 13 are both arc sections, and the radius of the arc section is greater than 100 mm.

[0044] Specifically, Figure 1-Figure 3 As shown, the first slot section 11 is located on the left side wall of the coal pillar 100, the third slot section 13 is located on the right side wall of the coal pillar 100, the second slot section 12 penetrates the coal pillar 100 in the left-right direction, and the left and right ends of the second slot section 12 are respectively connected to the first slot section 11 and the third slot section 13. The center lines of the first slot section 11, the second slot section 12 and the third slot section 13 are located on the same horizontal plane to avoid unnecessary bending of the monitoring optical fiber in the optical fiber slot 1.

[0045] It is understandable that if Figure 1-Figure 3 As shown, the connection between the first slot segment 11 and the second slot segment 12 is an arc segment, and the connection between the second slot segment 12 and the third slot segment 13 is also an arc segment, and the radius of the arc segment is greater than 100 mm, which can reduce the bending degree of the monitoring optical fiber at the connection and reduce the risk of damage to the monitoring optical fiber due to excessive bending. In addition, the coherent optical fiber path (i.e., the optical fiber slot 1) and good protection measures help maintain the stability of the optical fiber monitoring assembly 2, thereby improving the quality and continuity of data collection.

[0046] In some embodiments, the optical fiber monitoring assembly 2 includes a first monitoring optical fiber 21 and an optical fiber fixing member 22 . The first monitoring optical fiber 21 is connected to the optical fiber fixing member 22 . The extending direction of the optical fiber fixing member 22 is consistent with the extending direction of the optical fiber groove 1 .

[0047] Specifically, Figure 1-Figure 3 As shown, the extension direction of the optical fiber fixture 22 is consistent with the extension direction of the optical fiber slot 1, so that the optical fiber fixture 22 can be easily adapted to the optical fiber slot 1. The first monitoring optical fiber 21 and the optical fiber fixture 22 can be connected by means of a binding band, a buckle, etc., so as to quickly fix the optical fiber fixture 22 and the first monitoring optical fiber 21 together.

[0048] It can be understood that the optical fiber is effectively fixed in the optical fiber groove 1 by the optical fiber fixing member 22, reducing the displacement of the optical fiber caused by rock formation movement or external interference, and improving the stability of the monitoring system. By connecting the optical fiber fixing member 22 with the first monitoring optical fiber 21, the reliability of the optical fiber monitoring assembly 2 can be improved and its service life in harsh environments can be extended.

[0049] In some embodiments, the optical fiber monitoring assembly 2 also includes a first connecting member 23, a first end of the first connecting member 23 is connected to the optical fiber fixing member 22, a second end of the first connecting member 23 is connected to the first monitoring optical fiber 21, and the first monitoring optical fiber 21 is spaced apart from the optical fiber fixing member 22.

[0050] It is understandable that if Figure 1-Figure 3 As shown, the function of the first connector 23 is to provide a certain interval between the optical fiber fixture 22 and the first monitoring optical fiber 21, so as to reduce the direct pressure of the optical fiber fixture 22 on the optical fiber and protect the optical fiber from damage. According to the size of the optical fiber groove 1 and the specification of the first monitoring optical fiber 21, the size and shape of the first connector 23 are designed to ensure that it is compatible with the optical fiber fixture 22 and the first monitoring optical fiber 21. In addition, the interval between the first monitoring optical fiber 21 and the optical fiber fixture 22 is set by the first connector 23, and this interval can be adjusted as needed to ensure that the optical fiber will not be damaged due to the movement of the rock formation.

[0051] That is, the first connector 23 provides additional protection for the optical fiber, reducing direct damage caused by rock formation movement or external interference. Through the spacing effect of the first connector 23, the stability of the optical fiber in the optical fiber groove 1 is improved, which helps to maintain the accuracy of the monitoring data.

[0052] It should be noted that the optical fiber fixing member 22 may be a strip-shaped member that can be flexibly deformed, such as a steel bar, and may also be other objects with a certain degree of rigidity, such as a PVC tube.

[0053] In some embodiments, the fiber optic monitoring assembly 2 also includes a second monitoring optical fiber 24 and a second connecting member 25. The second monitoring optical fiber 24 is consistent with the extension direction of the optical fiber groove 1 and is located between two adjacent optical fiber grooves 1 in the height direction of the coal pillar 100. The second connecting member 25 is used to connect the second monitoring optical fiber 24 and the side of the coal pillar 100. There are multiple second connecting members 25, and the multiple second connecting members 25 are arranged at intervals along the extension direction of the optical fiber fixing member 22. The distance between two adjacent second connecting members 25 is less than the length of the second monitoring optical fiber 24 between the two connected second connecting members 25.

[0054] Specifically, Figure 1-Figure 3 As shown, the second monitoring optical fiber 24 is fixed to the side wall of the coal pillar 100 through the second connector 25, and the extension direction of the second monitoring optical fiber 24 is consistent with the extension direction of the optical fiber slot 1. A second monitoring optical fiber 24 is arranged between two adjacent optical fiber slots 1. It should be noted that the second monitoring optical fiber 24 is a temperature compensation optical fiber, that is, in order to eliminate the influence of temperature changes on the strain monitoring results, the second monitoring optical fiber 24 is arranged on the side wall of the coal pillar 100 to improve the monitoring accuracy.

[0055] It is understandable that if Figure 1-Figure 3 As shown, between two adjacent second connectors 25, the second optical fiber monitoring is in a relaxed state, so that it is not affected by external forces and is only sensitive to temperature, thereby eliminating the influence of temperature changes on strain detection results. The first connector 23 and the second connector 25 can be a connector for easy connection.

[0056] Preferably, there are a plurality of second monitoring optical fibers 24, and the plurality of second monitoring optical fibers 24 are arranged at intervals in the up-and-down direction.

[0057] In some embodiments, in step S3, grouting and plugging are performed in the second trench section 12 by means of segmented grouting.

[0058] Optionally, the optical fiber fixing member 22 placed in the second slot section 12 is a PVC tube, and the monitoring optical fiber is fixed to the PVC tube through the first connector 23. When performing segmented grouting, firstly, the end of the PVC tube is blocked and fixed to the borehole to prevent the gap between the PVC tube and the wall of the borehole from changing during the grouting process. Secondly, the PVC tube is used as a grouting tube. After the gap between the PVC tube and the side wall of the second slot section 12 is grouted, the PVC tube is grouted, thereby completing the grouting of the entire borehole.

[0059] That is to say, segmented grouting can ensure that each gap is fully filled and improve the overall quality of the sealing. Segmented grouting can reduce the impact and pressure on the optical fiber during the grouting process and protect the optical fiber from damage. Of course, the position and number of grouting sections can also be adjusted according to the specific situation of the second groove section 12 to adapt to different geological conditions and monitoring requirements.

[0060] In some embodiments, in step S4, before collecting data, a rebound hammer is used to detect the plugging area of ​​the optical fiber trench 1 to ensure that the plugging material in the optical fiber trench 1 forms a whole with the coal pillar 100.

[0061] It is understandable that before collecting data, using a rebound tester to test the plugging area of ​​the optical fiber slot 1 can ensure that the plugging material is fully solidified and tightly bonded to the coal pillar 100 to form a solid whole. The rebound tester is an instrument used to detect the hardness of materials such as concrete or rock, and the hardness of the plugging material is evaluated by measuring its rebound value.

[0062] That is to say, the reliability of the plugging material directly affects the stability of the optical fiber monitoring component 2, and thus affects the accuracy of the monitoring data. Rebound test helps to improve the accuracy and reliability of the monitoring system. Through testing, insufficient plugging or defects can be discovered in time, and timely measures can be taken to repair them, avoiding damage to the optical fiber or distortion of the monitoring data caused by plugging failure. In addition, good plugging quality helps to protect the optical fiber monitoring component 2 from environmental factors and extend the service life of the monitoring system.

[0063] In some embodiments, in step S4, the portion connecting the first monitoring optical fiber outside the optical fiber slot 1 and the optical fiber demodulation device 3 is wrapped with a plastic hose.

[0064] It is understandable that the environment in coal mine tunnels is complex and harsh. During monitoring, the line connected to the detection optical fiber should be led out of the tunnel. When the first monitoring optical fiber 21 is laid, 5-10 meters of its end is reserved and coiled into a coil, which is fused with the communication optical cable. Before fusion, a 1-2 meter long plastic hose is inserted in advance to protect the fusion joint and prevent breakage. The reserved monitoring optical fiber is pulled out of the tunnel and connected to the optical fiber demodulation equipment 3.

[0065] In some embodiments, Figure 4 As shown, there is one first monitoring optical fiber 21, and one first monitoring optical fiber 21 is connected in series with multiple optical fiber slots 1. It can be understood that Figure 4 As shown, a first monitoring optical fiber 21 is used to sequentially penetrate multiple optical fiber grooves 1, so that the first monitoring optical fiber 21 runs through the entire monitoring area. In other words, according to the geological conditions of the working surface and the layout of the optical fiber grooves 1, a path of the first monitoring optical fiber 21 is designed to ensure that the optical fiber can pass through each optical fiber groove 1 in sequence.

[0066] That is, a first monitoring optical fiber 21 is connected in series with multiple optical fiber slots 1, which reduces the amount of optical fiber used and improves the installation efficiency of the monitoring system. Since the number of optical fibers and installation work are reduced, this design can significantly reduce the cost of the monitoring system. In addition, the continuity of the optical fiber ensures the continuity and consistency of the monitoring data, which helps to more accurately analyze the changes in rock formation stress.

[0067] Of course, multiple sections of first monitoring optical fibers 21 can also be connected in series to form a first monitoring optical fiber 21 that can be arranged in all optical fiber slots 1, so that the design of the first monitoring optical fibers 21 being connected in series can make the maintenance and troubleshooting of the monitoring system simpler, and problems can be quickly located and repaired.

[0068] In other embodiments, Figure 5 As shown, there are multiple first monitoring optical fibers 21, and at least one first monitoring optical fiber 21 is arranged in one optical fiber groove 1. It can be understood that at least one first monitoring optical fiber 21 is arranged in each optical fiber groove 1. These first monitoring optical fibers 21 can be individual optical fibers or optical fiber bundles, depending on the monitoring requirements and the size of the optical fiber groove 1. According to the monitoring objectives and geological conditions, the appropriate optical fiber type and quantity are selected. The layout of the optical fiber in the optical fiber groove 1 is designed to ensure that different areas of the rock formation can be covered.

[0069] That is to say, the arrangement of multiple first monitoring optical fibers 21 can provide multiple monitoring points in one optical fiber slot 1, thereby improving the spatial resolution of monitoring. Moreover, when one first monitoring optical fiber 21 fails, other first monitoring optical fibers 21 can still provide data, thereby increasing the reliability of monitoring. In addition, the data collected through multiple optical fibers is more comprehensive, which helps to more accurately analyze the stress state of the rock formation.

[0070] In addition, in step S5, performing inversion based on the collected optical fiber monitoring data further includes the following steps:

[0071] Taking Brillouin optical time domain reflectometry (BOTDR) as an example, the advantages of BOTDR strain monitoring are obvious. It is a single-ended measurement without the need to form a loop, and the actual coordinates of the strain position can be determined. The distance D from the position where the BOTDR scatters to the incident end of the pulse light, that is, the distance from the deformation position to the BOTDR transmitting end, can be calculated by the formula:

[0072]

[0073] Where: c is the speed of light in a vacuum; n is the refractive index of the light wave; T is the time interval between the emitted light wave and the received scattered light. The optical fiber position is calibrated before the test. The specific operation is to bend a point on the optical fiber. At this time, the demodulation instrument will display the position where the strain occurs, that is, this point can be matched with the actual bending point of the optical fiber. On this basis, the coordinate axis is established, and the length direction of the coal pillar is set as the x-axis, and the width direction of the coal pillar is set as the y-axis. Before the working face is excavated, the optical fiber coincides with the x-axis. As the working face is excavated, the strain range will continue to extend in the x-axis direction, and the strain size will increase along the y-axis direction.

[0074] The principle of strain monitoring by optical fiber is that the optical fiber is stretched, resulting in a frequency shift change, and then the optical fiber tensile strain is inferred from the frequency shift. However, in the present invention, the optical fiber is laid along the length of the coal pillar, and the lateral deformation of the coal pillar needs to be monitored on site. Therefore, it is necessary to invert the horizontal deformation of the coal pillar from the optical fiber tensile strain. The change in the horizontal strain of the coal pillar is caused by the change in vertical stress. When the vertical stress increases, the horizontal strain increases. The optical fiber deforms together with the coal pillar rock mass. As the working face is mined, the vertical stress on the coal pillar increases. When the coal pillar expands outward, the optical fiber is stretched accordingly. The overall deformation shape is assumed to be parabolic. The parabola equation is:

[0075] y=ax 2 +bx+s

[0076] Where a is the quadratic coefficient, and s is the maximum value of the lateral expansion deformation of the coal pillar.

[0077] When the coal pillar is strained, the optical fiber changes from a horizontal straight line state to a parabola state. The optical fiber will have a certain length increment in the strain area, and the length increment is the arc length of the parabola minus the horizontal straight line length. Assume that the straight length of the optical fiber L = x2-x1, and the length increment is ΔL. Through this relationship, a relationship can be obtained. Solving the relationship can obtain the coefficient of the parabola and determine the shape of the parabola, which is the lateral deformation shape of the coal pillar.

[0078]

[0079] By using mathematical tools such as MATLAB, the a in the formula can be solved based on the measured data.

[0080] As the working face continues to be mined, the area reaching the maximum horizontal strain continues to increase, and the new deformation area close to the working face is still in the form of a parabola. At this time, the increment in the length of the middle straight line deformation part is the advancement distance of the working face, and the parabolic equations and deformation shapes at both ends will not change.

[0081] The optical fiber is laid in three layers, where the strain at the top and bottom is small and the strain in the middle is the largest. According to the above parabola model, three deformation curves along the height direction of the coal pillar can be obtained, and as the working face advances, the deformation curve can be updated in real time. According to the three parabolas, MATLAB can be used to fit them into a surface. The specific steps are:

[0082] First determine the equation of the parabola. The equation of the parabola can be determined by the above method and the fitting method can be selected.

[0083] Secondly, the iterative optimization method (genetic algorithm) is selected to obtain more accurate fitting results. The genetic algorithm can be used to find the optimal or approximately optimal surface parameters so that the surface can best fit the given parabola data points under a certain error metric. The specific steps are: a. Determine the equation and data points of the parabola. Select a quadratic or cubic surface model, and use the mean square error MSE to evaluate the degree of fit between the surface and the parabola data points. b. Randomly generate a set of surface model parameters (i.e., individuals in the genetic algorithm), which constitute the initial population. c. For each individual in the population (i.e., each set of parameters), calculate its fitness value (i.e., the fitting error between the surface and the parabola data points). d. Select excellent individuals as parents according to the fitness value to generate the next generation. e. Perform a crossover operation on the selected parent individuals to generate new offspring individuals. f. Perform a mutation operation on the offspring individuals to increase the diversity of the population. g. Replace some or all of the parent individuals in the population with offspring individuals to form a new generation of population. h. Repeat steps c to g until the predetermined number of iterations is reached or the fitness value no longer increases significantly. i. Output the optimal solution: Select the individual with the highest fitness value from the final population as the optimal solution, that is, the best parameters for fitting the surface.

[0084] Finally, the fitted surface equation is obtained through the obtained parameters, and the surface and the original parabola data points are visualized using the MATLAB drawing function. The quality of the fit can be verified by comparing the fitted surface and the original data points, and adjustments can be made as needed.

[0085] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0086] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0087] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0088] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0089] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0090] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A distributed optical fiber monitoring method for segment coal pillar deformation, characterized in that: The following steps are involved: S1. Plan and arrange the preset route of the optical fiber on the side of the coal pillar; S2. On the side of the coal pillar, an optical fiber groove is opened along the preset route, the extension direction of the optical fiber groove is consistent with the horizontal direction, there are multiple optical fiber grooves, the multiple optical fiber grooves are arranged at intervals along the height direction of the coal pillar, and there is a gap between the optical fiber groove adjacent to the top of the coal pillar and the top of the coal pillar, and there is a gap between the optical fiber groove adjacent to the bottom of the coal pillar and the bottom of the coal pillar; S3, arranging an optical fiber monitoring component in the optical fiber groove, and blocking the optical fiber groove to fix the optical fiber monitoring component in the optical fiber groove; S4, reserving a portion of the monitoring optical fiber outside the optical fiber groove and connecting it to an optical fiber demodulation device so as to collect data from the monitoring optical fiber; S5. Inversion is performed based on the collected optical fiber monitoring data to obtain the strain variation of the section coal pillar along the range of the strain sensing optical fiber.

2. The distributed optical fiber monitoring method for segment coal pillar deformation according to claim 1 is characterized in that: The optical fiber groove includes a first groove section, a second groove section and a third groove section connected in sequence, the second groove section is arranged to penetrate the coal pillar along the width direction of the coal pillar, and the connection between the first groove section and the second groove section and between the second groove section and the third groove section are both arc sections, and the radius of the arc section is greater than 100 mm.

3. The distributed optical fiber monitoring method for segment coal pillar deformation according to claim 2 is characterized in that: The optical fiber monitoring assembly includes a first monitoring optical fiber and an optical fiber fixing piece. The first monitoring optical fiber is connected to the optical fiber fixing piece. The extending direction of the optical fiber fixing piece is consistent with the extending direction of the optical fiber groove.

4. The distributed optical fiber monitoring method for segment coal pillar deformation according to claim 3 is characterized in that: The optical fiber monitoring assembly further comprises a first connector, a first end of which is connected to the optical fiber fixing member, a second end of which is connected to the first monitoring optical fiber, and the first monitoring optical fiber is spaced apart from the optical fiber fixing member.

5. The distributed optical fiber monitoring method for segment coal pillar deformation according to claim 4 is characterized in that: The optical fiber monitoring assembly also includes a second monitoring optical fiber and a second connecting piece. The second monitoring optical fiber is consistent with the extension direction of the optical fiber groove and is located between two adjacent optical fiber grooves in the height direction of the coal pillar. The second connecting piece is used to connect the second monitoring optical fiber and the side of the coal pillar. There are multiple second connecting pieces, and the multiple second connecting pieces are arranged at intervals along the extension direction of the optical fiber fixing piece. The distance between two adjacent second connecting pieces is less than the length of the second monitoring optical fiber between the two connected second connecting pieces.

6. The distributed optical fiber monitoring method for segment coal pillar deformation according to claim 5 is characterized in that: In step S3, grouting and plugging are performed in the second trench section by using a segmented grouting method.

7. The distributed optical fiber monitoring method for segment coal pillar deformation according to claim 6 is characterized in that: In step S4, before collecting data, a rebound tester is used to detect the plugging area of ​​the optical fiber groove to ensure that the plugging material in the optical fiber groove forms a whole with the coal pillar.

8. The distributed optical fiber monitoring method for segment coal pillar deformation according to claim 7, characterized in that: In step S4, the portion of the optical fiber outside the optical fiber groove that is connected to the optical fiber demodulation device is wrapped with a plastic hose.

9. The distributed optical fiber monitoring method for segment coal pillar deformation according to claim 8, characterized in that: The number of the first monitoring optical fiber is one, and the first monitoring optical fiber is connected in series with a plurality of the optical fiber grooves.

10. The distributed optical fiber monitoring method for segment coal pillar deformation according to claim 8, characterized in that: There are a plurality of the first monitoring optical fibers, and at least one of the first monitoring optical fibers is arranged in one of the optical fiber grooves.

Images