Capsule bag type coal seam roof displacement measuring device and measuring method

Abstract

The invention discloses a bag type coal seam roof displacement measuring device and method, and belongs to the technical field of mine engineering and underground engineering monitoring. The measuring method comprises the following steps: drilling a positioning hole below a coal seam roof in advance; liquid or gas is injected into the bag main body, so that the bag main body is expanded to a preset volume; the pressure sensor and the temperature compensation element are used for accurately recording pressure change data in the bag; inputting the acquired data to a preset pressure-displacement conversion model, and converting the acquired data into roof displacement data; and finally obtaining a relational expression between the pressure change value and the top plate displacement, and presetting an alarm function. According to the measuring method, the detected pressure data are converted into the roof displacement data through the pressure-displacement conversion model, and the roof displacement can be simply, conveniently and accurately measured in real time by constructing the function relation expression between the pressure change value and the roof displacement. The reliability and the efficiency of underground engineering roof monitoring are improved, and the engineering safety is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of mining engineering and underground engineering monitoring, and in particular relates to a bag-type coal seam roof displacement measuring device and a measuring method. Background Art

[0002] In underground projects such as mining and tunnel construction, roof displacement monitoring is crucial. Small changes in roof displacement may indicate changes in roof stability. If the roof displacement cannot be measured in a timely and accurate manner, serious safety accidents such as roof collapse may occur.

[0003] At present, existing roof monitoring technologies, such as the Chinese patent with authorization publication number CN222379060U, disclose supporting the roof through telescopic parts and triggering warning colors. Although it can respond to displacement exceeding the limit in real time, it relies on complex mechanical structures, has high installation and maintenance costs, and cannot achieve high-precision displacement quantitative analysis. The Chinese patent with authorization publication number CN222048955U discloses improving measurement accuracy by adjusting the installation position of the displacement sensor, but does not solve the problem of interference of underground temperature fluctuations on sensor output, resulting in long-term monitoring error accumulation. Another example is the guide tube device proposed in the Chinese patent with authorization publication number CN217235061U. Although it optimizes the threading operation, its mechanical structure is complex and difficult to adapt to different rock formation conditions. Another example is the Chinese patent application with publication number CN102174900A, which proposes a roof displacement monitoring device based on compressed gas or hydraulic oil, which uses preload force to maintain roof contact and measures displacement through magnetic induction. Although this solution can achieve high-precision measurement, it relies on a complex pneumatic / hydraulic system, has high maintenance costs, and is prone to failure in high temperature and high pressure environments, and cannot fully meet the measurement needs of underground coal mines.

[0004] Therefore, it is urgent to propose a method and device that can simply, accurately and real-time measure the displacement of the top plate to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to solve the problems existing in the prior art, such as complex mechanical structure, high installation and maintenance cost, great environmental influence, interference to sensors due to underground temperature changes, resulting in long-term monitoring error accumulation, etc., and to provide a bag-type coal seam roof displacement measuring device and measuring method, which converts the detected pressure data into roof displacement data through a pressure-displacement conversion model, and by constructing a functional relationship between the pressure change value and the roof displacement, can simply, accurately and real-time measure the roof displacement, thereby improving the reliability and efficiency of underground engineering roof monitoring, ensuring engineering safety, etc.

[0006] To achieve the above object, the present invention adopts the following technical solution: a bag-type coal seam roof displacement measurement method, comprising the following steps:

[0007] S1. Select the measurement location and pre-drill a positioning hole under the corresponding coal seam roof. The hole depth H is determined according to the coal seam characteristics: H = k × h + s, where k is the lithology coefficient, h is the coal seam thickness, and s is the safety margin;

[0008] S2, inserting the bladder body into the positioning hole, fixing the bladder body at the positioning hole with a support, and arranging a pressure sensor and a temperature compensation element inside the bladder body, and then injecting liquid or gas into the bladder body through an injection device to expand it to a predetermined volume, so as to ensure that the bladder is closely attached to the inner wall of the top plate and fixed;

[0009] S3, using a pressure sensor and a temperature compensation element to accurately record the pressure change data inside the pouch body;

[0010] S4, connecting the bag body to the data acquisition device on the ground, and transmitting the acquired data to the data processing unit, which converts the received pressure data into top plate displacement data according to a preset pressure-displacement conversion model;

[0011] The calculation formula of the set pressure-displacement conversion model is as follows:

[0012] 1) Assuming that the coal seam roof is an isotropic linear elastic material, the pressure is evenly distributed, the displacement is small, and the material does not undergo plastic deformation during loading. Based on the above assumptions, the linear pressure-displacement model is expressed as:

[0013] Where D is the displacement of the top plate (unit / m), P is the pressure in the bladder (unit / Pa), E is the elastic modulus of the material (unit / Pa), and L is the effective thickness of the top plate (unit / m), which represents the effective working area from the bladder to the top plate;

[0014] 2) Assuming that the coal seam roof may have nonlinear material properties or other environmental influences, the pressure-displacement model is expressed as: D = k·P n ,

[0015] Where k is the material's pressure-displacement constant, which depends on the material's properties and the improved working environment, and n is an index that describes how the material responds to changes in pressure and needs to be calibrated using experimental data;

[0016] The specific process of converting pressure data into top plate displacement data is as follows:

[0017] Obtain the elastic modulus E of the coal seam roof; use pressure sensors and displacement sensors to record displacement data under different pressures; use the statistical method of least squares method to fit the k and n parameters of the material to obtain the best matching pressure-displacement relationship; and test it on an unused data set, and finally use the best matching pressure-displacement relationship to output the conversion result;

[0018] S5. Regularly record the pressure change or deformation in the bag body, calculate the top plate displacement by combining the time series analysis algorithm, and take into account the error that may be caused by temperature fluctuations. Use the temperature compensation mechanism to correct the measurement results, and finally obtain the functional relationship between the pressure change value and the top plate displacement;

[0019] The functional relationship between the pressure change value and the top plate displacement is: δ = f (ΔP) = A * (ΔP) ^ B + C,

[0020] In the formula, δ represents the amount of top plate subsidence (unit / mm), ΔP represents the pressure change value (unit / Pa), A, B, and C are all unknown coefficients obtained by fitting experimental data. The values ​​of coefficients A, B, and C depend on the material properties, geometry, properties of the filling medium, and mechanical properties of the top plate of the capsule. The value of B is usually greater than 1 to reflect the nonlinear relationship.

[0021] S6. Adjust the mine support strategy based on the obtained data, store and display the calculated roof displacement data, and set the safety threshold alarm function. When abnormal displacement is detected, the device automatically alarms to remind the staff to take corresponding measures.

[0022] Furthermore, in step S4, the data acquisition device is provided with a pressure sensor, a temperature sensor, an acceleration sensor, a strain gauge, a displacement sensor, a microprocessor, a memory and a data transmission module.

[0023] Furthermore, in step S5, the specific process of correcting the measurement results using the temperature compensation mechanism is as follows: performing a temperature calibration experiment to analyze the influence of temperature on the readings of the pressure sensor and the deformation sensor; establishing a temperature compensation model based on the results of the temperature calibration experiment; using the established temperature compensation model, performing temperature compensation on the collected pressure and deformation data to eliminate errors caused by temperature fluctuations;

[0024] The temperature calibration experiment and temperature compensation model establishment process are as follows:

[0025] After the bag expands to the working state, the device is placed in a temperature-controlled closed environment to simulate the temperature fluctuation range of 0℃ to 60℃ underground;

[0026] Measure the output values ​​of the pressure sensor and displacement sensor in the bladder at different temperatures, and simultaneously record the thermal expansion deformation of the contact surface between the outer wall of the bladder and the top plate;

[0027] Based on experimental data, the thermal expansion coefficient α of the fusion bag material is established m and roof lithology temperature sensitivity coefficient α r Compensation model:

[0028]

[0029] D=D 0 -γ(TT 0 )-δ·α r (TT 0 ),

[0030] Where, P and D are the parameter values ​​of the pressure sensor and displacement sensor after temperature compensation respectively; P 0 , D 0 is the measured value; α m is the thermal expansion coefficient of the bag material; α r is the temperature sensitivity coefficient of the roof lithology; γ is the temperature expansion coefficient of the displacement sensor (unit: mm / ℃); β is the zero drift temperature coefficient (unit: Pa / ℃); δ is the system coupling error coefficient, that is, the displacement error ratio caused by thermal coupling of the bag-roof interface under unit temperature change; T 0 is the reference temperature.

[0031] Furthermore, in step S6, the safety threshold is set to 50 mm, and when the calculated displacement exceeds the set value, the device emits an alarm sound and a warning signal.

[0032] The present invention also discloses a bag-type coal seam roof displacement measuring device for the above-mentioned measuring method, characterized in that: the measuring device includes a bag assembly, an injection device, a data acquisition device, a support and a power supply unit; the bag assembly includes a bag body, a plurality of pressure sensors and a temperature compensation element uniformly arranged inside the bag body, the outer surface of the bag body is provided with an identification scale for convenient observation of the filling degree, and the top of the bag body is provided with a connection interface connected to the injection device through a pipeline and a data transmission line; the injection device includes a connecting pipeline, one or more micro pumps and a control valve; the data acquisition device is provided with a pressure sensor, a temperature sensor, an acceleration sensor, a strain gauge, a displacement sensor, a microprocessor, a memory and a data transmission module, and the data acquisition device is also connected to the data processing unit through the data transmission module and connected to the bag assembly through a cable or a wireless method; a rechargeable lithium battery pack and a low-power consumption circuit are arranged inside the power supply unit.

[0033] Furthermore, the bag body is made of a high-strength corrosion-resistant material, and the high-strength corrosion-resistant material is one of polyurethane or Teflon.

[0034] The beneficial effects of the present invention are:

[0035] 1) In the measurement method of the present invention, the detected pressure data is converted into roof displacement data through a pressure-displacement conversion model, and by constructing a functional relationship between the pressure change value and the roof displacement, the roof displacement can be measured simply, accurately and in real time, thereby improving the reliability and efficiency of underground engineering roof monitoring and ensuring engineering safety.

[0036] 2) In the measuring method of the present invention, the bag is inserted into the positioning hole of the roof for fixing, which realizes simple and quick installation, reduces the impact on normal mining operations, and the overall components used are low-cost and easy to promote and apply on a large scale. At the same time, long-term and continuous roof displacement monitoring is realized, and the temperature compensation mechanism is used to improve the measurement accuracy, adapt to the application requirements under different environmental conditions, and improve the degree of automation of the device; it can be integrated into the smart mine management system, thereby improving the overall management level. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic flow chart of the method for measuring the displacement of the coal seam roof of the present invention;

[0038] Figure 2 It is a structural schematic diagram of the coal seam roof displacement measuring device of the present invention.

[0039] In the figure, 1-bag assembly, 2-injection device, 3-data acquisition module, 4-support member, 5-power supply unit. DETAILED DESCRIPTION

[0040] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments.

[0041] Example 1: Figure 2 As shown, the present invention provides a bag-type coal seam roof displacement measuring device, which includes a bag assembly 1, an injection device 2, a data acquisition device 3, a support member 4 and a power supply unit 5.

[0042] The bladder assembly 1 includes a bladder body, a plurality of pressure sensors and temperature compensation elements uniformly arranged inside the bladder body; the bladder body is made of a high-strength corrosion-resistant material, which is one of polyurethane or Teflon; the outer surface of the bladder body is provided with marking scales for convenient observation of the filling degree, and the top of the bladder body is provided with a connection interface connected to the injection device 2 through a pipeline and a data transmission line.

[0043] The bag assembly 1 is connected to the data acquisition device 3 on the ground via a cable or wireless connection. In addition, by setting up multiple bag assembly 1 monitoring points at different locations on a mine working face, a networked monitoring system is formed, and the data from all monitoring points are transmitted to the ground monitoring center via wireless or wired means for centralized management and analysis.

[0044] The injection device 2 includes a connecting pipe, one or more micro pumps and a control valve; the injection device 2 is used to accurately inject liquid or gas into the bag body to keep the bag in a proper expansion state without rupture.

[0045] The data acquisition device 3 is provided with a pressure sensor, a temperature sensor, an acceleration sensor, a strain gauge, a displacement sensor, a microprocessor, a memory and a data transmission module. The data acquisition device 3 is also connected to the data processing unit through the data transmission module; wherein the acceleration sensor is used to more comprehensively capture the dynamic change information of the top plate, and the data transmission module is a wireless communication module.

[0046] The power supply unit 5 is internally provided with a rechargeable lithium battery pack and a low power consumption circuit.

[0047] like Figure 1 As shown, it is a flow chart of the measuring method of the bag-type coal seam roof displacement measuring device. A bag-type coal seam roof displacement measuring method of the present invention comprises the following steps:

[0048] S1. Select a suitable measurement location and pre-drill a positioning hole under the corresponding coal seam roof. The hole depth H is determined according to the characteristics of the coal seam. The formula is as follows: H = k × h + s, where k is the lithology coefficient (1.5 to 2 for soft rock and 1 to 1.2 for hard rock), h is the coal seam thickness, and s is the safety margin (usually 3 to 5 m).

[0049] S2. Insert the bag body into the positioning hole, fix the bag body at the positioning hole with a support, set a pressure sensor and a temperature compensation element inside the bag body, and then inject liquid or gas into the bag body through an injection device to expand it to a predetermined volume to ensure that the bag is tightly attached to the inner wall of the top plate and fixed.

[0050] S3. Use a pressure sensor and a temperature compensation element to accurately record the pressure change data inside the bladder body.

[0051] S4, connecting the bag body to the data acquisition device on the ground, and transmitting the acquired data to the data processing unit, which converts the received pressure data into top plate displacement data according to a preset pressure-displacement conversion model.

[0052] The calculation formula of the set pressure-displacement conversion model is as follows:

[0053] 1) Assuming that the coal seam roof is an isotropic linear elastic material, the pressure is evenly distributed, the displacement is small, and the material does not undergo plastic deformation during loading. Based on the above assumptions, the linear pressure-displacement model is expressed as:

[0054] Where D is the displacement of the top plate (unit / m), P is the pressure in the bladder (unit / Pa), E is the elastic modulus of the material (unit / Pa), and L is the effective thickness of the top plate (unit / m), which represents the effective working area from the bladder to the top plate.

[0055] 2) Assuming that the coal seam roof may have nonlinear material properties or other environmental influences, the pressure-displacement model is expressed as: D = k·P n ,

[0056] Where k is the material’s pressure-displacement constant, which depends on the material’s properties and the improved working environment, and n is an exponent that describes how the material responds to changes in pressure and needs to be calibrated using experimental data.

[0057] Assuming the following parameters are obtained experimentally: elastic modulus E = 20 GPa, effective thickness L = 0.5 m, k = 0.01, n = 1.5, then the displacement can be calculated using a linear model: For nonlinear models use: D = 0.01·P 1.5 ; For the linear model, the top plate displacement D is proportional to the pressure P. For the nonlinear model, in the displacement-pressure relationship, a smaller pressure increase may result in a more significant displacement change.

[0058] The specific process of converting pressure data into top plate displacement data is as follows:

[0059] Obtain the elastic modulus E of the coal seam roof; use pressure sensors and displacement sensors to record displacement data under different pressures; use the statistical method of least squares to fit the material's k and n parameters to obtain the best matching pressure-displacement relationship; and test it on an unused data set, and finally use the best matching pressure-displacement relationship to output the conversion result.

[0060] S5. Regularly record the pressure change or deformation in the bag body, calculate the top plate displacement using a time series analysis algorithm, and consider the possible errors caused by temperature fluctuations. Use a temperature compensation mechanism to correct the measurement results, and finally obtain the functional relationship between the pressure change value and the top plate displacement.

[0061] The functional relationship between the pressure change value and the top plate displacement is: δ = f (ΔP) = A * (ΔP) ^ B + C,

[0062] Wherein, δ represents the amount of top plate subsidence (unit / mm), ΔP represents the pressure change (unit / Pa), A, B, and C are all unknown coefficients obtained by fitting experimental data. The values ​​of coefficients A, B, and C depend on the material properties, geometry, properties of the filling medium, and mechanical properties of the top plate of the bladder. The value of B is usually greater than 1 to reflect the nonlinear relationship.

[0063] The specific process of correcting the measurement results using the temperature compensation mechanism is as follows: conduct a temperature calibration experiment to analyze the impact of temperature on the readings of the pressure sensor and deformation sensor; establish a temperature compensation model based on the results of the temperature calibration experiment; use the established temperature compensation model to perform temperature compensation on the collected pressure and deformation data to eliminate errors caused by temperature fluctuations.

[0064] The temperature calibration experiment and temperature compensation model establishment process are as follows:

[0065] After the bag expands to the working state, the device is placed in a temperature-controlled closed environment to simulate the temperature fluctuation range of 0℃ to 60℃ underground;

[0066] Measure the output values ​​of the pressure sensor and displacement sensor in the bladder at different temperatures, and simultaneously record the thermal expansion deformation of the contact surface between the outer wall of the bladder and the top plate;

[0067] Based on experimental data, the thermal expansion coefficient α of the fusion bag material is established m and roof lithology temperature sensitivity coefficient α r Compensation model:

[0068]

[0069] D=D 0 -γ(TT 0 )-δ·α r (TT 0 ),

[0070] Where, P and D are the parameter values ​​of the pressure sensor and displacement sensor after temperature compensation respectively; P 0 , D 0 is the measured value; α m is the thermal expansion coefficient of the bag material (obtained through material testing); α r is the temperature sensitivity coefficient of the roof lithology (obtained through core experiments); γ is the temperature expansion coefficient of the displacement sensor (unit: mm / ℃); β is the zero drift temperature coefficient (unit: Pa / ℃); δ is the system coupling error coefficient, that is, the displacement error ratio caused by thermal coupling of the bag-roof interface under unit temperature change; T 0 is the reference temperature (25°C).

[0071] S6. Adjust the mine support strategy based on the obtained data, store and display the calculated roof displacement data, and set the safety threshold alarm function. When abnormal displacement is detected, the device automatically alarms to remind the staff to take corresponding measures.

[0072] The pressure-displacement conversion model is a mathematical model established based on the elastic modulus, initial volume, physical properties of the filling medium, and the mechanical interaction relationship between the roof and the capsule. Through a large number of experiments and theoretical calculations, the functional relationship between the pressure change value and the roof displacement is obtained. For example, when the pressure sensor detects a pressure increase of X Pa, the model calculates that the roof has sunk by X mm. If the calculated displacement exceeds the set safety threshold of 50 mm, the system immediately issues an alarm and a warning signal to remind the miners to stop working and take measures such as reinforcing the roof. After a period of monitoring, the device can stably and accurately measure the roof displacement, effectively preventing the occurrence of roof accidents.

[0073] Example 1: In a typical thick coal seam working face, 3m below the roof was selected as the measuring point, and a positioning hole with a diameter of 80mm and a depth of 5m was drilled. After a bag with a volume of 5L was inserted into the hole, water was injected into the bag through the injection system to make the bag expand and come into close contact with the roof. The bag was connected to the data acquisition system on the ground and data collection began. By analyzing the data for one month, it was found that the roof in this area sank by an average of about 0.5mm per day, and the coal mining process parameters were optimized accordingly.

[0074] Example 2: In another thin coal seam working face, 1.5m below the roof was selected as the measuring point, and a positioning hole with a diameter of 60mm and a depth of 3m was drilled. A smaller bag with a volume of 3L was used and air was injected instead of water because the geological conditions here are more suitable for gaseous media. The bag was also connected to the ground data acquisition system to achieve effective monitoring of the roof displacement. After a period of monitoring, it was found that the roof displacement showed periodic changes, which helps to predict future displacement trends.

[0075] The bag-type coal seam roof displacement measuring method and device of the present invention pre-drills a positioning hole under the coal seam roof, inserts the bag into the positioning hole, and injects liquid or gas into the bag through an injection system to expand it to a predetermined volume, thereby ensuring that the bag is tightly attached to the inner wall of the roof and fixed, thereby achieving simple and quick installation and reducing the impact on normal mining operations. Moreover, the overall components used are low-cost and easy to promote and apply on a large scale. At the same time, long-term and continuous roof displacement monitoring is achieved, and the data is accurate and reliable, providing strong support for the scientific formulation of mine support plans. The temperature compensation mechanism is used to improve the measurement accuracy, adapt to application requirements under different environmental conditions, improve the degree of automation of the device, and can be integrated into a smart mine management system, thereby improving the overall management level, and solving the problems of complex mechanical structure, high installation and maintenance costs, great environmental impact, and interference to sensors due to underground temperature changes, resulting in long-term monitoring error accumulation in existing roof displacement measurement methods. In addition, some sensor monitoring methods also have defects such as inconvenient installation and high cost.

[0076] The above description is only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A bag-type coal seam roof displacement measurement method, characterized in that: The following steps are involved: S1. Select the measurement location and pre-drill a positioning hole under the corresponding coal seam roof. The hole depth H is determined according to the coal seam characteristics: H = k × h + s, where k is the lithology coefficient, h is the coal seam thickness, and s is the safety margin; S2, inserting the bladder body into the positioning hole, fixing the bladder body at the positioning hole with a support, and arranging a pressure sensor and a temperature compensation element inside the bladder body, and then injecting liquid or gas into the bladder body through an injection device to expand it to a predetermined volume, so as to ensure that the bladder is closely attached to the inner wall of the top plate and fixed; S3, using a pressure sensor and a temperature compensation element to accurately record the pressure change data inside the pouch body; S4, connecting the bag body to the data acquisition device on the ground, and transmitting the acquired data to the data processing unit, which converts the received pressure data into top plate displacement data according to a preset pressure-displacement conversion model; The calculation formula of the set pressure-displacement conversion model is as follows: 1) Assuming that the coal seam roof is an isotropic linear elastic material, the pressure is evenly distributed, the displacement is small, and the material does not undergo plastic deformation during loading. Based on the above assumptions, the linear pressure-displacement model is expressed as: Where D is the displacement of the top plate (unit / m), P is the pressure in the bladder (unit / Pa), E is the elastic modulus of the material (unit / Pa), and L is the effective thickness of the top plate (unit / m), which represents the effective working area from the bladder to the top plate; 2) Assuming that the coal seam roof may have nonlinear material properties or other environmental influences, the pressure-displacement model is expressed as: D = k·P n , Where k is the material's pressure-displacement constant, which depends on the material's properties and the improved working environment, and n is an index that describes how the material responds to changes in pressure and needs to be calibrated using experimental data; The specific process of converting pressure data into top plate displacement data is as follows: Obtain the elastic modulus E of the coal seam roof; use pressure sensors and displacement sensors to record displacement data under different pressures; use the statistical method of least squares method to fit the k and n parameters of the material to obtain the best matching pressure-displacement relationship; The test is then performed on an unused data set, and the conversion result is finally output using the best matching pressure-displacement relationship; S5. Regularly record the pressure change or deformation in the bag body, calculate the top plate displacement by combining the time series analysis algorithm, and take into account the error that may be caused by temperature fluctuations. Use the temperature compensation mechanism to correct the measurement results, and finally obtain the functional relationship between the pressure change value and the top plate displacement; The functional relationship between the pressure change value and the top plate displacement is: δ = f (ΔP) = A* (ΔP) ^ B + C, In the formula, δ represents the amount of top plate subsidence (unit / mm), ΔP represents the pressure change value (unit / Pa), A, B, and C are all unknown coefficients obtained by fitting experimental data. The values ​​of coefficients A, B, and C depend on the material properties, geometry, properties of the filling medium, and mechanical properties of the top plate of the capsule. The value of B is usually greater than 1 to reflect the nonlinear relationship. S6. Adjust the mine support strategy based on the obtained data, store and display the calculated roof displacement data, and set the safety threshold alarm function. When abnormal displacement is detected, the device automatically alarms to remind the staff to take corresponding measures.

2. The assay method according to claim 1, characterized in that: In step S4, the data acquisition device is provided with a pressure sensor, a temperature sensor, an acceleration sensor, a strain gauge, a displacement sensor, a microprocessor, a memory and a data transmission module.

3. The measuring method according to claim 1, characterized in that: In step S5, the specific process of correcting the measurement results using the temperature compensation mechanism is as follows: performing a temperature calibration experiment to analyze the influence of temperature on the readings of the pressure sensor and the deformation sensor; establishing a temperature compensation model based on the results of the temperature calibration experiment; using the established temperature compensation model to perform temperature compensation on the collected pressure and deformation data to eliminate errors caused by temperature fluctuations; The temperature calibration experiment and temperature compensation model establishment process are as follows: After the bag expands to the working state, the device is placed in a temperature-controlled closed environment to simulate the temperature fluctuation range of 0℃ to 60℃ underground; Measure the output values ​​of the pressure sensor and displacement sensor in the bladder at different temperatures, and simultaneously record the thermal expansion deformation of the contact surface between the outer wall of the bladder and the top plate; Based on experimental data, the thermal expansion coefficient α of the fusion bag material is established m and roof lithology temperature sensitivity coefficient α r Compensation model: D=D0-γ(T-T0)-δ·α r (T-T0), Where P and D are the parameter values ​​of the pressure sensor and displacement sensor after temperature compensation; P0 and D0 are the measured values; α m is the thermal expansion coefficient of the bag material; α r is the temperature sensitivity coefficient of the roof lithology; γ is the temperature expansion coefficient of the displacement sensor (unit: mm / ℃); β is the zero drift temperature coefficient (unit: Pa / ℃); δ is the system coupling error coefficient, that is, the displacement error ratio caused by thermal coupling of the bag-roof interface under unit temperature change; T0 is the reference temperature.

4. The measuring method according to claim 1, characterized in that: In step S6, the safety threshold is set to 50 mm, and when the calculated displacement exceeds the set value, the device emits an alarm sound and a warning signal.

5. A bag-type coal seam roof displacement measuring device used in the measuring method according to any one of claims 1 to 4, characterized in that: The measuring device comprises a bladder assembly (1), an injection device (2), a data acquisition device (3), a support (4) and a power supply unit (5); the bladder assembly (1) comprises a bladder body, a plurality of pressure sensors and a temperature compensation element uniformly arranged inside the bladder body, the outer surface of the bladder body is provided with a marking scale for conveniently observing the filling degree, and the top of the bladder body is provided with a connection interface connected to the injection device (2) through a pipeline and a data transmission line; the injection device (2) comprises a connecting pipeline, one or more micro pumps and a control valve; the data acquisition device (3) is provided with a pressure sensor, a temperature sensor, an acceleration sensor, a strain gauge, a displacement sensor, a microprocessor, a memory and a data transmission module, and the data acquisition device (3) is also connected to the data processing unit through the data transmission module and connected to the bladder assembly (1) through a cable or a wireless connection; the power supply unit (5) is provided with a rechargeable lithium battery pack and a low-power consumption circuit.

6. The measuring device according to claim 5, characterized in that: The bag body is made of a high-strength corrosion-resistant material, and the high-strength corrosion-resistant material is one of polyurethane or Teflon.

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