Mine roof stress-rotation angle synchronous monitoring device and weighting prediction method

Abstract

The invention discloses a mine roof stress-rotation angle synchronous monitoring device and a weighting prediction method, and belongs to the technical field of mine roof rock stratum movement monitoring. The device comprises a plurality of monitoring sensors and connecting rods, the monitoring sensors are sequentially connected end to end, and every two adjacent monitoring sensors are connected through the corresponding connecting rod; the monitoring sensor comprises a pipe body, and a strain rosette used for collecting stress data is arranged on the outer surface of the pipe body. A three-way angle meter used for collecting angle data is arranged in the pipe body. Hole sealing rings are arranged in the circumferential directions of the head end and the tail end of the pipe body; a grouting module is further arranged on the pipe body, and grout in the grouting module can flow to the outer surface of the sensor pipe body, the inner wall of the monitoring drill hole and the closed space between the two hole sealing rings through the liquid drainage holes; and after the slurry is solidified, the device and the rock stratum are integrated. The goaf roof rock stratum stress and motion parameters and the like can be synchronously monitored, and accurate weighting prediction can be achieved based on the monitoring data.

Description

Technical Field

[0001] The present invention relates to the technical field of mine roof slab rock layer movement monitoring, and in particular to a mine roof slab stress-rotation angle synchronous monitoring device and a pressure prediction method. Background Art

[0002] The coal mining process disrupts the equilibrium of the original rock stress field, causing stress redistribution. The resulting advanced support pressure ahead of the working face significantly impacts the mine pressure in the haulage and return air lanes, manifesting as localized roof collapse, roadway spalling, and floor bulging. As the working face advances, the mined space increases, while the length of the overlying roof strata, unsupported and exposed, also increases. When the roof overhang reaches its limit, the roof strata fracture and rotate, causing the working face roof to sink rapidly, resulting in pressure. The initial pressure is quite strong and can easily lead to roof accidents. Both advanced support pressure and pressure from overburden movement and fracture are significant factors in inducing roof disasters and rock bursts. Therefore, mine pressure monitoring and early warning are crucial components of mine disaster prevention and control, and play a vital role in safe mining.

[0003] Currently, roof monitoring during mining primarily relies on static testing of in-situ rock stress, with relatively little monitoring of stress evolution caused by mining disturbances. However, dynamic stress changes are crucial for assessing mining safety. Currently, there are no effective methods for monitoring the movement of overburden in goaf areas. Most existing projects rely on monitoring the working resistance of hydraulic supports and roof subsidence to reflect roof status and infer incoming pressure. While monitoring the working resistance of hydraulic supports can provide some information, this method cannot directly capture rock formation deformation and fracture. While monitoring roof subsidence can reflect roof displacement changes, it also cannot accurately determine changes in the rock formation's internal structure. While these monitoring methods can provide some reference information, they still have significant limitations. Furthermore, current monitoring of roof strata in roadways and goafs is independent, lacking continuity and unable to fully capture the full range of roof pressure characteristics across the entire roadway and goaf area.

[0004] At the same time, due to a lack of effective monitoring data, the current theoretical estimates of pressure step distances differ significantly from the measured results. This uncertainty makes it difficult to accurately determine the time and location of pressure step distances during mining, increasing safety risks during the mining process. Summary of the Invention

[0005] The purpose of the present invention is to provide a mine roof stress-rotation angle synchronous monitoring device and a pressure prediction method to monitor the stress evolution and movement of the roof rock layer in real time, accurately and continuously, realize the whole process monitoring from the tunnel to the goaf, and accurately predict the pressure step distance of the roof rock layer.

[0006] In order to achieve the above objectives, the technical solutions adopted by the present invention are as follows:

[0007] A device for synchronously monitoring stress and rotation angle of a mine roof, comprising a plurality of monitoring sensors and connecting rods, wherein the plurality of monitoring sensors are connected end to end in sequence, and two adjacent monitoring sensors are connected via the connecting rods;

[0008] The monitoring sensor includes a tube body, a strain rosette for collecting stress data is provided on the outer surface of the tube body; a three-way goniometer for collecting angle data is provided inside the tube body;

[0009] Sealing rings are provided around the head and tail ends of the pipe body. When the pipe body is inserted into the inner wall of the monitoring borehole, the sealing rings fit tightly against the pipe body and the inner wall of the monitoring borehole, so that a sealed space is formed between the pipe body, the inner wall of the monitoring borehole, and the sealing rings at the head and tail ends of the pipe body.

[0010] A grouting module is also provided on the pipe body, which includes a slurry chamber, the interior of which is filled with slurry; the slurry chamber is located inside the pipe body, and a drainage hole is provided on the pipe wall of the pipe body at a position corresponding to the slurry chamber; a sliding block is provided at one end of the slurry chamber, and the sliding block is connected to a pull rope that pulls it to squeeze the slurry in the slurry chamber; when the sliding block squeezes the slurry in the slurry chamber, the slurry enters the above-mentioned sealed space through the drainage hole.

[0011] The present invention also provides a method for predicting the incoming pressure of a mine roof, which uses the above-mentioned mine roof stress-rotation angle synchronous monitoring device, and includes the following steps:

[0012] Step 1: Drilling a monitoring borehole into the solid coal roof rock layer in the connecting tunnel of the working face transport tunnel or the return air tunnel;

[0013] Step 2: Assemble the pipe body and connecting rod according to the height of each rock layer in the roof, then inject slurry into the slurry chamber of the pipe body, and then push the connected pipe body and connecting rod into the monitoring borehole. The sealing ring fits the outer surface of the pipe body and the inner wall of the monitoring borehole;

[0014] Step 3: After pushing the pipe body to the predetermined position, pull the pull rope, which drives the sliding block to move through the first pulley, squeezing the slurry in the slurry chamber so that the slurry flows through the drainage hole to the outer surface of the pipe body, the inner wall of the monitoring borehole, and the sealed space between the two sealing rings;

[0015] Step 4: After the slurry solidifies, the data acquisition unit collects the angle data measured by the three-axis goniometer and the stress data measured by the strain gauge in real time, thereby obtaining the real-time horizontal and vertical position and stress state of the pipe body of any monitoring sensor;

[0016] When the coal seam below the installation location has not yet been mined, the roof stress state is monitored in real time to provide accurate data for the tunnel support plan; after mining, the real-time horizontal and vertical position and stress of the tube body of each monitoring sensor are used to predict the rotation angle and pressure step distance of the roof rock layer to complete the pressure prediction.

[0017] The beneficial technical effects of the present invention are as follows:

[0018] (1) The mine roof stress-rotation angle synchronous monitoring device of the present invention can monitor the stress evolution process of the tunnel roof, that is, as the coal seam working face advances, the stress and motion parameters of the rock strata in the goaf roof can be synchronously monitored; and the synchronous monitoring device of the present invention includes a number of monitoring sensors, which are distributed at different positions on the mine roof, so as to achieve comprehensive monitoring. Furthermore, based on the precise monitoring data obtained in real time by the synchronous monitoring device of the present invention, the pressure step distance calculation can be performed, and the error between the calculated result and the measured result is relatively small, which can achieve more accurate pressure prediction; for example, by using this method, the time and location of the pressure can be accurately judged during the mining process, thereby increasing the safety of the mining process.

[0019] (2) The device for synchronously monitoring the stress and rotation angle of the roof of a mine according to the present invention can monitor the rock layers of the roof of the mine at multiple points in real time, i.e., it can synchronously monitor the stress and rotation angle of each rock layer of the roof in real time, accurately and continuously, monitor the entire cycle and large range of the coal seam roof from the advanced area to the goaf area, and measure the pressure step distance, thereby providing more detailed rock layer information for the prevention and control of disasters such as mine pressure, rock layer control and rock burst.

[0020] (3) The synchronous monitoring device for stress and rotation angle of the mine roof of the present invention has a simple and quick assembly process when used on site. It can be assembled and used according to the actual length of the monitoring borehole in the mine roof monitoring. In addition, the synchronous monitoring device of the present invention has a simple structure, fewer parts and components, is easy to process and manufacture, and is relatively inexpensive, which can reduce the investment cost of mine monitoring.

[0021] (4) Based on the stress, rotation angle and other data measured in real time by the mine top plate stress-rotation angle synchronous monitoring device of the present invention, the pressure step distance and other data can be obtained without complex calculations, thereby realizing accurate prediction of the mine top plate pressure, and the method is simple and fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the structural principle of a device for synchronously monitoring stress and rotation angle of a mine roof according to an embodiment of the present invention;

[0023] Figure 2 Schematic diagram of the cross section of the construction layout of the device for synchronously monitoring the stress and rotation angle of the mine roof according to an embodiment of the present invention;

[0024] Figure 3 This is a schematic plan view of the construction layout of the device for synchronously monitoring the stress and rotation angle of the mine roof according to an embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram showing the projection angle calculation principle of the device for synchronously monitoring the stress and rotation angle of the mine roof according to an embodiment of the present invention;

[0026] Figure 5 This is a schematic diagram showing the rotation angle calculation principle of the device for synchronously monitoring the stress and rotation angle of a mine roof according to an embodiment of the present invention;

[0027] Figure 6 This is a diagram showing the calculation principle of the initial pressure step distance of the device for synchronously monitoring the stress and rotation angle of the mine roof according to an embodiment of the present invention;

[0028] Figure 7 This is a diagram showing the calculation principle of the periodic pressure step distance of the device for synchronously monitoring the stress and rotation angle of the mine roof according to an embodiment of the present invention.

[0029] In the figure: 1. Three-axis goniometer, 2. Pipe body, 3. Connecting rod, 4. Strain gauge, 5. Pulley block, 6. Sealing ring, 7. Sliding block, 8. Slurry chamber, 9. Drain hole, 10. Pull rope, 11. Return air tunnel, 12. Transport tunnel, 13. Connecting tunnel, 14. Monitoring borehole, 15. Goaf, 16. Monitoring sensor. DETAILED DESCRIPTION

[0030] The purpose of the present invention is to provide a mine roof stress-rotation angle synchronous monitoring device and a pressure prediction method to monitor the stress evolution and movement of the roof rock layer in real time, accurately and continuously, realize the whole process monitoring from the tunnel to the goaf, and predict the pressure step distance of the roof rock layer.

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0032] like Figure 1As shown, a device for synchronously monitoring roof stress and rotation angle in a mine is shown. The device includes several monitoring sensors 16 and connecting rods 3. The sensors 16 are connected end-to-end, with adjacent sensors 16 connected via the connecting rods 3. The monitoring sensors 16 include a tube 2, with a strain gauge 4 positioned on its outer surface to collect stress data. A three-dimensional goniometer 1 is located within the tube 2 to collect angle data. The three-dimensional goniometer 1 measures the relative angle of the tube within which it is located. This angle is used to calculate the rotation angle of the roof rock stratum where the monitoring sensor is located. The strain gauge 4 measures and calculates the three-dimensional stress state. Sealing rings 6 are circumferentially positioned at both the leading and trailing ends of the tube. When the tube 2 is inserted into the inner wall of a monitoring borehole 14, or a through-layer borehole, the sealing rings 6 tightly adhere to the tube 2 and the inner wall of the monitoring borehole 14, creating a sealed space between the tube 2, the inner wall of the monitoring borehole 14, and the sealing rings 6 at the leading and trailing ends of the tube 2.

[0033] The pipe body 2 is also provided with a grouting module, which includes a slurry chamber 8 filled with slurry. The slurry chamber 8 is located within the pipe body 2, and a drainage hole 9 is provided on the pipe wall of the pipe body 2 at a position corresponding to the slurry chamber. A sliding block 7 is provided at one end of the slurry chamber 8, and the sliding block 7 is connected to a pull rope 10 that is pulled to squeeze the slurry in the slurry chamber 8. When the sliding block 7 squeezes the slurry in the slurry chamber 8, the slurry enters the sealed space through the drainage hole 9.

[0034] The three-axis goniometer used in the present invention is also often called a three-dimensional motion attitude measurement system, or attitude sensor, which includes motion sensors such as a three-axis gyroscope, a three-axis accelerometer, and a three-axis electronic compass.

[0035] Since the synchronous monitoring device of the present invention includes multiple monitoring sensors 16, it can be placed at multiple points in one hole to monitor the movement of multiple overlying rock layers. During installation, several monitoring sensor tubes are connected end to end, and adjacent tubes are connected by connecting rods.

[0036] As a further development of the present invention, three sets of strain gauge rosettes 4 are installed on each of the aforementioned tube bodies 2, spaced 120° apart and arranged circumferentially along the outer surface of the tube body 2. To ensure standardized installation of the device, one set of strain gauge rosettes 4 is positioned at the intersection of the plane containing the x- and z-axes of the triaxial goniometer and the tube body 2. When the synchronous monitoring device is installed in the monitoring borehole 14, this set of strain gauge rosettes is positioned at the top. One set of strain gauge rosettes 4 is positioned at one of the two intersections of the plane containing the x- and z-axes of the triaxial goniometer and the tube body 2, and when the synchronous monitoring device is installed in the monitoring borehole, this set of strain gauge rosettes faces upward and is positioned directly above the tube body 2. These three sets of strain gauge rosettes are used to measure the three-dimensional in-situ stress state of the rock formation in which the tube body is located.

[0037] Furthermore, a fixed block is provided inside the pipe body 2, and the sliding block 7, the fixed block and the pipe wall of the pipe body together form a slurry chamber 8. A pulley group 5 is also provided inside the pipe body 2. Specifically, the pulley group 5 includes a first pulley, a second pulley and a third pulley, wherein the first pulley is on one side of the fixed block, and the second pulley and the third pulley are respectively installed on the upper and lower sides of the end of the pipe body; the first pulley is connected to the sliding block 7 through a connecting rope. One end of the pull rope 10 is connected to the second pulley or the third pulley, and the other end of the pull rope 10 passes around the first pulley and the third pulley, or the first pulley and the second pulley and then extends outward from the monitoring borehole 14. The first pulley is a movable pulley, and the second pulley and the third pulley are both fixed pulleys. Each slurry chamber 8 of the pipe body 2 is equipped with a pull rope 10.

[0038] Multiple drainage holes 9 are provided, spaced circumferentially along the wall of the tube body 2. These holes are located at the end of the slurry chamber that first extends into the monitoring borehole. Because the slurry has a certain viscosity, and because the drainage holes 9 are located obliquely above the slurry chamber 8 when the tube body 2 is inserted upwardly into the monitoring borehole 14, the slurry does not flow out of the drainage holes 9 until the slurry chamber 8 is squeezed.

[0039] Furthermore, the connecting rod 3 includes a cylindrical rod body, and flared ends are provided at both ends of the cylindrical rod body, and the end of the tube body 2 is inserted into the flared ends. The connecting rod 3 and the tube body 2 are both made of hard materials, and several tube bodies 2 are connected end to end in this way. Two adjacent tube bodies 2 are connected via the connecting rod 3 to ensure that the device can be pushed to the specified position when installed at multiple points in one hole. Of course, the tube body 2 is made of hard material to protect the internal three-dimensional angle meter from being damaged during the monitoring process. Each of the monitoring sensor tube bodies is circumferentially provided with at least one sealing ring 6 at the head and tail ends. The sealing ring 6 is made of soft material such as rubber so that the sealing ring 6 fits tightly to the tube body 2 and the inner wall of the monitoring borehole. That is, the tube body 2 and the inner wall of the monitoring borehole are sealed and connected by the sealing ring 6, so that a sealed space is formed between the tube body 2, the inner wall of the monitoring borehole and the two sealing rings 6. When the grouting module is grouting and fixing, it is necessary to use a pulley to pull the pull rope 10 to drive the sliding block 7 to squeeze the slurry in the slurry chamber. The squeezed slurry enters the above-mentioned sealed space through the drainage hole 9. After the slurry solidifies, the slurry fixes the pipe body 2 and the rock layer roof as one. In this way, the pipe body 2 can migrate and rotate with the top rock layer. Among them, the sealing ring 6 is used to confine the slurry to the closed space outside the circumference of the pipe body 2 to prevent the slurry from flowing out. The pull rope 10 passes between the sealing ring 6 and the pipe body 2.

[0040] Furthermore, the synchronous monitoring device also includes a data acquisition unit located in the transport lane 12. The data acquisition unit is connected to the tri-directional goniometer 1 and the strain gauge rosette 4 via a signal cable. The unit is configured to collect angle data from the tri-directional goniometer 1 and stress data from the strain gauge rosette 4. The tube 2 is provided with threading holes at both ends, or is semi-enclosed. The connecting rod 3 is hollow, and the signal cable passes through the tube 2 and the connecting rod 3.

[0041] The present invention also provides a method for predicting the incoming pressure of a mine roof, which uses the above-mentioned mine roof stress-rotation angle synchronous monitoring device, and includes the following steps:

[0042] Step 1: Drill a hole 14 into the solid coal roof rock layer in the working face transport tunnel 12 or the connecting tunnel 13 of the return air tunnel 11, such as Figure 2 、 Figure 3 As shown in the figure, the drilling depth should reach the critical layer.

[0043] Step 2: Assemble the pipe body 2 and connecting rods 3 according to the height of each rock layer in the roof, ensuring that each rock layer has a monitoring sensor 16. A spatial coordinate system is established with the vertically upward direction as the positive z-axis and the axial direction of the horizontal tunnel as the y-axis. This coordinate system is used to determine the rotation angle after the rock layer breaks. A bonding slurry, which acts as a fixing device, is injected into the slurry chamber 8 of the pipe body 2. The connected pipe body 2 and connecting rod 3 are then pushed into the monitoring borehole 14. The sealing ring 6 is fitted to the outer surface of the pipe body and the inner wall of the monitoring borehole.

[0044] Step 3: Grouting and fixing by the grouting module. After pushing the device to the predetermined position, the pulley block 5 is pulled by the pull rope 10 to move the sliding block 7, squeezing the adhesive slurry in the slurry chamber 8, so that the slurry flows through the drainage hole 9 to the outer surface of the sensor tube, the inner wall of the monitoring borehole, and the sealed space between the two sealing rings.

[0045] Step 4: After the slurry solidifies, the device and the rock formation become one. The data acquisition unit collects real-time angle data measured by the three-axis goniometer 1 and stress data measured by the strain gauge rosette 4 in each monitoring sensor, thereby determining the real-time horizontal and vertical position and stress state of each monitoring sensor's tube.

[0046] When the measurement area is located in the tunnel area, the monitoring sensor mainly monitors the stress data of the roof in the advanced area of ​​the tunnel. As the working face is mined and the area to be measured enters the goaf, the rock formation stress-rotation angle will be monitored synchronously, and the rotation angle and stress measured in real time by each monitoring sensor tube will be used to predict the roof pressure step distance.

[0047] This means that when the coal seam beneath the installation location has not yet been mined, the roof stress state can be monitored in real time, providing accurate data for tunnel support planning. After mining, the real-time horizontal and vertical position and stress of each monitoring sensor tube are used to predict the rotation angle and pressure step distance of the roof rock layer, completing the pressure forecast.

[0048] In step 4, the stress and rotation angle of the mine roof are monitored simultaneously:

[0049] The three-dimensional stress (vertical stress, maximum horizontal principal stress, and minimum horizontal principal stress) can be calculated from the strain data measured by the strain rosette.

[0050] In order to facilitate the measurement and calculation of the rotation angle, it is stipulated that the vertical direction is the z-axis, the y-axis parallel to the roadway axis is the y-axis, and the x-axis perpendicular to the roadway axis is the x-axis to establish a spatial coordinate system, and the same direction is used as the zero angle of the three-way angle meter, such as Figure 4 、 Figure 5 For a monitoring sensor installed in a certain rock formation, when the rock formation breaks and rotates, the monitoring sensor rotates synchronously. The rotation angle θ of the rock formation is expressed as:

[0051] θ=|θ ′ t -θ ′ 0|

[0052] in,

[0053]

[0054] Where:

[0055] θ ′ t ,θ ′ 0: A certain time t and the initial installation time θ y The projection angle on the yz plane.

[0056] θ x0 ,θ z0 : Respectively represent the x-direction and z-direction angles measured by the trigonometric instrument during initial installation.

[0057] θ xt ,θ zt : They represent the x-direction and z-direction angles measured by the tri-directional goniometer at a certain time t.

[0058] Similarly, the rotation angles of other rock formations can be monitored.

[0059] Incoming pressure prediction method:

[0060] like Figure 6As shown in the figure, for the initial pressure step, since the length of the mining face along the inclination direction is much longer than the distance the roof rock stratum is exposed along the strike, the roof rock stratum can be regarded as a fixed-support beam supported by the coal wall of the working face at one end and the boundary coal pillar at the other end. When the maximum tensile stress at a certain point in the rock stratum reaches the tensile strength limit of the rock stratum, the rock stratum will crack at that point. For the fixed-support beam, the maximum bending moment occurs at both ends of the beam. From the mechanics of materials, we can obtain:

[0061]

[0062] Right now:

[0063]

[0064] Where:

[0065] R T : The ultimate tensile strength of the rock formation.

[0066] h: thickness of the rock layer, m.

[0067] q: Uniformly distributed load applied to the rock beam, KN / m, obtained from the strain gauge data.

[0068] L b : The initial pressing step distance of the top plate.

[0069] Determine the critical rotation angle when the rock formation breaks:

[0070] For the critical rotation angle |θ| when the rock beam breaks, the rotation angle equation of any cross section of the clamped beam can be obtained from material mechanics:

[0071]

[0072] Where:

[0073] q: The uniformly distributed load on the rock beam, KN / m.

[0074] L b : The initial pressing step distance of the top plate.

[0075] x: The installation distance between the monitoring sensor and the cut hole, m.

[0076] EI: flexural rigidity. E is the elastic modulus and I is the area moment of inertia.

[0077] E can be measured, I and L b It can be calculated that q is measured by the strain rosette on this monitoring device.

[0078] The rock formation rotation angle θ is measured in real time by a three-way goniometer. When the rock formation rotation angle θ = |θ|, the rock beam breaks and rotates, causing the top plate to press down on the working face. Thus, the above steps can predict the top plate pressure.

[0079] like Figure 7 As shown in the figure, for the periodic pressure step, when the mining height is large and the basic roof is close to the coal seam, it is easy to cause the basic roof to move in the form of a cantilever beam structure.

[0080] Same as the first time pressing step, for the length L i , the cantilever beam is subjected to a uniform load q, the free end is at x = 0, and the fixed end is at x = L i , since the maximum bending moment of the cantilever beam occurs at the fixed end, it is Therefore, the ultimate span of the rock beam when it breaks is:

[0081]

[0082] Right now:

[0083]

[0084] Where:

[0085] L i : The i-th pressing step distance of the top plate, i≥2.

[0086] R T : The ultimate tensile strength of the rock formation.

[0087] h: thickness of the rock layer, m.

[0088] q: Uniformly distributed load applied to the rock beam, KN / m, can be measured by this device.

[0089] Determine the critical rotation angle when the rock formation breaks:

[0090] According to material mechanics, the critical rotation angle |θ| when the rock beam breaks is the rotation angle caused by the uniformly distributed load q at any position x:

[0091]

[0092] Where:

[0093] q: The uniformly distributed load on the rock beam, KN / m.

[0094] L i : The i-th pressing step distance of the top plate, i≥2.

[0095] x i : The distance between the monitoring sensor installation position and the sum of the previous pressure steps, m.

[0096] EI: flexural rigidity. E is the elastic modulus and I is the area moment of inertia.

[0097] In the above formula, the first time to press or the first time to press is Lb Indicates; L i The subscript i in represents the i-th pressure.

[0098] Similarly, the rock formation rotation angle θ is measured in real time by a three-way goniometer. When the rock formation rotation angle θ = |θ|, the rock beam breaks and rotates, causing the top plate to press down on the working face. Thus, the above steps can predict the top plate pressure.

[0099] So far, the present embodiment has been described in detail with reference to the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the mine roof stress-rotation angle synchronous monitoring device and the pressure step prediction method of the present invention. The mine roof stress-rotation angle synchronous monitoring device of the present invention has fewer components, and the assembly process is simple and quick when used on site. It can be assembled and used according to the actual height of the roof rock layer in the mine roof monitoring. The mine roof stress-rotation angle synchronous monitoring device of the present invention has a relatively simple structure and is easy to process and manufacture. It uses fewer precision instruments inside, and the relatively precise instruments are only a three-way angle meter 1 and a strain gauge 4. The entire device is relatively inexpensive, which can reduce the investment cost of mine monitoring. The beneficial technical effect of the application of the mine roof stress-rotation angle synchronous monitoring device of the present invention is that it can monitor the rock layers of the mine roof at multiple points in real time, and synchronously monitor the stress and rotation angle of each rock layer on the roof in real time, accurately and continuously, and monitor the full cycle and large range of the coal seam roof from the advanced area to the goaf area, as well as measure the pressure step distance, to provide more detailed rock layer information for disaster prevention and control such as mine pressure, rock layer control and impact ground pressure.

[0100] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A device for synchronously monitoring the stress and rotation angle of a mine roof, characterized by: It includes a plurality of monitoring sensors and connecting rods, wherein the plurality of monitoring sensors are connected end to end in sequence, and two adjacent monitoring sensors are connected via the connecting rods; The monitoring sensor includes a tube body, a strain rosette for collecting stress data is provided on the outer surface of the tube body; a three-way goniometer for collecting angle data is provided inside the tube body; Sealing rings are provided around the head and tail ends of the pipe body. When the pipe body is inserted into the inner wall of the monitoring borehole, the sealing rings fit tightly against the pipe body and the inner wall of the monitoring borehole, so that a sealed space is formed between the pipe body, the inner wall of the monitoring borehole, and the sealing rings at the head and tail ends of the pipe body. A grouting module is also provided on the pipe body, which includes a slurry chamber, the interior of which is filled with slurry; the slurry chamber is located inside the pipe body, and a drainage hole is provided on the pipe wall of the pipe body at a position corresponding to the slurry chamber; a sliding block is provided at one end of the slurry chamber, and the sliding block is connected to a pull rope that pulls it to squeeze the slurry in the slurry chamber; when the sliding block squeezes the slurry in the slurry chamber, the slurry enters the above-mentioned sealed space through the drainage hole.

2. The device for synchronously monitoring the stress and rotation angle of a mine roof according to claim 1, characterized in that: Three sets of strain rosettes are installed on each tube, spaced 120 degrees apart and arranged circumferentially along the outer surface of the tube. One set of strain rosettes is located at the intersection of the plane containing the x- and z-axes of the tri-axial goniometer and the tube. When the synchronous monitoring device is installed in the monitoring borehole, this set of strain rosettes is located at the top.

3. The device for synchronously monitoring the stress and rotation angle of a mine roof according to claim 1, characterized in that: A fixed block is provided inside the tube body, and the sliding block, the fixed block and the tube wall of the tube body together form a slurry chamber; A pulley set is further provided inside the tube body, comprising a first pulley, a second pulley and a third pulley, wherein the first pulley is located on one side of the fixed block, and the second pulley and the third pulley are respectively installed on the upper and lower sides of the end of the tube body; the first pulley is connected to the sliding block via a connecting rope; One end of the pull rope is connected to the second pulley or the third pulley, and the other end of the pull rope passes around the first pulley and the third pulley, or the first pulley and the second pulley and then extends out of the monitoring borehole.

4. The device for synchronously monitoring the stress and rotation angle of a mine roof according to claim 1, characterized in that: The drainage holes are arranged in plurality and are arranged at intervals along the pipe wall of the pipe body in the circumferential direction; the drainage holes are opened at the end of the slurry chamber that first extends into the monitoring borehole.

5. The device for synchronously monitoring the stress and rotation angle of a mine roof according to claim 1, characterized in that: The connecting rod includes a cylindrical rod body, with flared ends provided at both ends of the cylindrical rod body, and the end of the tube body is inserted into the flared ends; the connecting rod and the tube body are both made of hard materials; the sealing ring is made of soft materials, and the pull rope passes between the sealing ring and the tube body.

6. The device for synchronously monitoring the stress and rotation angle of a mine roof according to claim 1, characterized in that: The synchronous monitoring device also includes a data acquisition unit, which is connected to the three-axis goniometer and the strain rosette through a signal cable; both ends of the tube body are provided with threading holes, or are in a semi-closed state, and the signal cable passes through the tube body and the connecting rod.

7. A method for predicting the incoming pressure of a mine roof, using the device for synchronously monitoring the stress and rotation angle of a mine roof as claimed in any one of claims 1 to 6, characterized in that The following steps are involved: Step 1: Drilling a monitoring borehole into the solid coal roof rock layer in the connecting tunnel of the working face transport tunnel or the return air tunnel; Step 2: Assemble the pipe body and connecting rod according to the height of each rock layer in the roof, then inject slurry into the slurry chamber of the pipe body, and then push the connected pipe body and connecting rod into the monitoring borehole. The sealing ring fits the outer surface of the pipe body and the inner wall of the monitoring borehole; Step 3: After pushing the pipe body to the predetermined position, pull the pull rope, which drives the sliding block to move through the first pulley, squeezing the slurry in the slurry chamber so that the slurry flows through the drainage hole to the outer surface of the pipe body, the inner wall of the monitoring borehole, and the sealed space between the two sealing rings; Step 4: After the slurry solidifies, the data acquisition unit collects the angle data measured by the three-axis goniometer and the stress data measured by the strain gauge in real time, thereby obtaining the real-time horizontal and vertical position and stress state of the pipe body of any monitoring sensor; When the coal seam below the installation location has not yet been mined, the roof stress state is monitored in real time to provide accurate data for the tunnel support plan; after mining, the real-time horizontal and vertical position and stress of the tube body of each monitoring sensor are used to predict the rotation angle and pressure step distance of the roof rock layer to complete the pressure prediction.

8. The method for predicting mine roof pressure according to claim 7, characterized in that: In order to facilitate the measurement and calculation of the rotation angle, a spatial coordinate system is established with the vertical direction as the z-axis, the y-axis parallel to the roadway axis as the y-axis, and the x-axis perpendicular to the roadway axis. The same direction is used as the zero angle of the three-axis angle meter. For a monitoring sensor installed in a certain rock layer, when the rock layer breaks and rotates, the monitoring sensor rotates synchronously. The rotation angle θ of the rock layer is expressed as: θ=|θ ′ t -θ ′ 0| in, Where: θ ′ t ,θ ′ 0: A certain time t and the initial installation time θ y Projection angle on the yz plane; θ x0 ,θ z0 : represent the x-direction and z-direction angles measured by the trigonometric instrument during initial installation; θ xt ,θ zt : represent the x-direction and z-direction angles measured by the tri-directional goniometer at a certain time t; Similarly, the rotation angles of other rock formations can be monitored.

9. A mine roof pressure prediction method according to claim 8, characterized in that: The following steps are also included: a1. For the initial pressure step, since the length of the mining face along the inclination direction is much longer than the distance of the roof rock layer exposed along the strike, the roof rock layer can be regarded as a fixed-support beam supported by the coal wall of the working face at one end and the boundary coal pillar at the other end. When the maximum tensile stress at a certain point in the rock layer reaches the tensile strength limit of the rock layer, the rock layer will crack at that point. For the fixed-support beam, the maximum bending moment occurs at both ends of the beam. According to material mechanics, Right now: Where: R T : The ultimate tensile strength of the rock formation; h: thickness of the rock layer, m; q: uniformly distributed load applied to the rock beam, KN / m, obtained from the strain gauge data; L b : The initial pressing step distance of the top plate; b1. Determine the critical rotation angle when the rock formation breaks: For the critical rotation angle |θ| when the rock beam breaks, the rotation angle equation of any section of the clamped beam is obtained from material mechanics: Where: q: uniformly distributed load on the rock beam, KN / m; L b : The initial pressing step distance of the top plate; x: The installation distance between the monitoring sensor and the cut hole, m; EI: flexural rigidity; where E is the elastic modulus and I is the moment of inertia of the area; c1. Use a three-axis goniometer to measure the rock formation rotation angle θ in real time. When the rock formation rotation angle θ = |θ|, the rock beam breaks and rotates, causing the top plate to press down on the working face. Thus, the above steps can predict the top plate pressure.

10. A mine roof pressure prediction method according to claim 8, characterized in that: The following steps are also included: a2. For periodic pressure steps, the basic top moves in the form of a cantilever beam structure; The free end of the cantilever beam is at x = 0 and the fixed end is at x = L i , since the maximum bending moment of the cantilever beam occurs at the fixed end, it is Therefore, the ultimate span of the rock beam when it breaks is: Right now: Where: L i : The i-th pressing step distance of the top plate, i≥2; R T : The ultimate tensile strength of the rock formation; h: thickness of the rock layer, m; q: uniformly distributed load applied to the rock beam, KN / m; b2. Determine the critical rotation angle when the rock formation breaks: For the critical rotation angle |θ| when the rock beam breaks, the rotation angle caused by the uniformly distributed load q at any position x is: Where: q: uniformly distributed load on the rock beam, KN / m; L i : The i-th pressing step distance of the top plate, i≥2; x i : The distance between the monitoring sensor installation position and the sum of the previous pressure steps, m; EI: flexural rigidity; where E is the elastic modulus and I is the moment of inertia of the area; c2. Use a three-axis goniometer to measure the rock formation rotation angle θ in real time. When the rock formation rotation angle θ = |θ|, the rock beam breaks and rotates, causing the top plate to press down on the working face. Thus, the above steps can predict the top plate pressure.

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