An apparatus and method for measuring mining stress, temperature, and water pressure.

Abstract

This application relates to the field of mine safety monitoring technology, and discloses a device and method for measuring mining stress, temperature, and water pressure. The device includes a high-strength metal shell, a hollow connecting rod, a water pressure measuring unit, a strain measuring unit, a temperature measuring unit, and a single through-fiber. The shell surface has a spiral resin grouting channel, and a mechanical interlocking structure is constructed using solid resin to equivalently transfer rock mass displacement to the shell. The temperature-compensated fiber optic grating is coated with a heat-insulating coating. In-situ rigid coupling is achieved by injecting liquid resin into the grouting channel. Wavelength division multiplexing (WDM) technology is used to obtain the center wavelength peak of each grating. Based on the temperature-compensated grating, the change in ambient temperature is extracted, thereby subtracting the thermal drift of the strain grating and obtaining the compensated strain value. The in-situ three-dimensional mining stress state is output by mapping the constitutive equations. This invention achieves synchronous high-fidelity acquisition of multiple physical field parameters and possesses intrinsic safety characteristics and electromagnetic immunity.

Description

Technical Field

[0001] This invention relates to the field of mine safety monitoring technology, specifically to a device and method for measuring mining stress, temperature, and water pressure. Background Technology

[0002] In the process of deep mineral resource mining, the redistribution of surrounding rock stress and the dynamic evolution of pore water pressure caused by mining activities are the core causes of mine disasters such as rockbursts and water inrushes. Currently, the monitoring of stress and water pressure in underground mines mainly relies on vibrating wire or piezoresistive electrical sensors. These sensors face multiple technical limitations in practical applications. On the one hand, the high-frequency alternating electromagnetic fields generated by large underground mining equipment and high-voltage power supply networks can easily penetrate the shielding layer of the sensors and their transmission cables, resulting in a large amount of nonlinear noise superimposed on the acquired signals, which seriously affects the signal-to-noise ratio of the data. On the other hand, electrical sensors and their signal processing units involve current transmission during operation, which poses a risk of generating electric sparks in explosive gas mixtures containing methane and coal dust, making it difficult to meet the high level of intrinsic safety requirements.

[0003] Furthermore, existing stress monitoring equipment often fails to effectively separate thermal strain caused by environmental temperature fluctuations from mechanical strain caused by mining activities. Thermal drift in optical materials such as silica or metal structural components due to temperature changes is frequently misinterpreted as a mechanical load response, leading to significant baseline drift in monitoring results. At the physical installation level, the coupling quality between the sensor housing and the borehole wall directly determines the efficiency of stress transmission. Traditional manual grouting methods struggle to ensure uniform distribution of grout within deep boreholes; residual air and gaps formed by grout contraction within the borehole can obstruct strain field transmission paths, causing measured data to fail to accurately reflect the in-situ stress state within the rock mass. Therefore, developing an integrated monitoring solution with anti-electromagnetic interference capabilities, all-optical transmission, adaptive temperature compensation, and high-rigidity physical coupling is crucial for ensuring the safety of deep mining operations. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a device and method for measuring mining stress, temperature, and water pressure. It solves the problems of mine underground monitoring equipment being susceptible to electromagnetic interference under complex working conditions, difficulty in effectively separating the sensitive components of temperature and mechanical field intersections, and data distortion caused by inadequate coupling between sensors and rock mass in deep boreholes.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The first aspect of the present invention provides an apparatus for measuring mining stress, temperature and water pressure.

[0007] The core components of the device include a high-strength metal shell, a hollow connecting rod positioned axially inside the high-strength metal shell, a water pressure measuring unit, a strain measuring unit, and a temperature measuring unit. The high-strength metal shell serves as the load-bearing body, and its outer surface is machined with a spiral resin grouting channel. This channel guides the multi-component liquid resin to undergo a chemical cross-linking reaction, forming a high-rigidity solid resin entity. Through the mechanical interlocking structure constructed by the solid resin entity and the spiral resin grouting channel, minute displacements of the surrounding rock in the mine are transmitted non-destructively to the high-strength metal shell, achieving efficient mechanical coupling between the sensor and the rock mass.

[0008] The water pressure measuring unit is integrated at the front end of the high-strength metal casing. Its structure includes a permeable cover plate, a permeable stone, a flexible diaphragm, a pressure transmitting rod, and a water pressure-sensitive fiber optic grating. Pore water from the external environment passes through the permeable cover plate and the permeable stone for physical filtration before entering the water pressure-sensitive chamber. Water pressure acts on the flexible diaphragm, causing deformation. This deformation is then transmitted mechanically to the water pressure-sensitive fiber optic grating via the pressure transmitting rod, resulting in a change in the grating period due to pressure.

[0009] The strain measurement unit is located in the middle of the high-strength metal shell and senses the geometric deformation of the shell through four sets of strain fiber Bragg gratings installed on the inner wall. The temperature measurement unit is fixed to the surface of the hollow connecting rod, and the temperature-compensating fiber Bragg grating is fully covered with a thermal insulation coating made of polymer material. The thermal insulation coating utilizes its physical shear and tensile properties to absorb the deformation of the hollow connecting rod caused by mechanical load, thereby blocking the transmission of mechanical stress to the fiber Bragg grating and keeping the temperature-compensating fiber Bragg grating in a pure temperature response state with zero axial additional stress.

[0010] The water pressure-sensitive fiber Bragg grating, the four sets of strain fiber Bragg gratings, and the temperature-compensated fiber Bragg grating are axially connected in series via a single through-fiber in the physical optical path and connected to an external fiber demodulation device. During the fabrication stage, each fiber Bragg grating is assigned a non-overlapping initial Bragg reflection wavelength operating range, and wavelength division multiplexing (WDM) technology is used to achieve co-cable transmission of multiple field signals.

[0011] A second aspect of the present invention provides a method for measuring mining stress, temperature, and water pressure.

[0012] This method, relying on the aforementioned device, achieves synchronous and accurate acquisition of multiphysics parameters through the following logic:

[0013] During the in-situ installation phase, liquid resin is injected into the spiral resin grouting channel using external grouting equipment. Utilizing the channel's helix angle and cross-sectional geometry, the resin is propelled in a spiral flow, simultaneously expelling air from the borehole and solidifying to form a solid resin entity, thus establishing a shear-resistant physical interface between the sensor and the coal and rock mass.

[0014] During the signal acquisition and demodulation stage, the fiber optic demodulation device emits a continuous broadband spectral signal. Each fiber grating reflects a narrowband center wavelength optical signal in a specific band, according to the grating period length under the current load condition. Multiple reflected signals are superimposed within the same physical optical path to form a composite reflected optical signal. The fiber optic demodulation device extracts the independent center wavelength peak data of each measurement point within a single time period through a spectral scanning module.

[0015] During the cross-sensitivity elimination and temperature compensation stage, wavelength difference-based compensation calculations are performed. The absolute change in ambient temperature is extracted using the center wavelength drift of the temperature-compensated fiber grating. Based on this, the thermally induced drift caused by thermal expansion and thermo-optic effects is subtracted in real time from the total wavelength drift of the strained fiber grating. This process effectively separates the mechanical strain response from the thermal strain response, outputting the compensated strain value after eliminating temperature interference.

[0016] In the parameter inversion and result output stage, the water pressure wavelength drift is converted into a true pore water pressure value using a linear mapping relationship. Simultaneously, the four sets of compensated strain values ​​are used as known boundary parameters and substituted into a pre-stored set of mapping constitutive equations derived from the stress-deformation theory of thick-walled cylinders based on elasticity. Through numerical solving by a microprocessor, the maximum and minimum planar principal stresses and their orientation angles are obtained through inversion. Finally, spatial geometric tensor reconstruction is performed to output the in-situ three-dimensional mining stress state corresponding to the borehole coordinate system.

[0017] Furthermore, this method supports large-scale network monitoring. By performing global band segmentation on N devices connected in series on the backbone transmission fiber, the full spectrum frequency domain is divided into 6N independent intervals, enabling synchronous remote real-time monitoring of multiple measurement points and multiple parameters in a purely passive, electromagnetic interference-resistant environment.

[0018] This invention provides a device and method for measuring mining stress, temperature, and water pressure. It offers the following advantages:

[0019] 1. This invention sets a spiral resin grouting channel on the outer surface of a high-strength metal shell. During the grouting process, the liquid resin is pushed forward in a spiral shape under the constraint of the channel geometry, continuously expelling the air inside the test borehole. After the resin cross-links and cures, the solid resin entity formed forms a mechanical interlocking structure with the surface of the metal shell, establishing a shear-resistant physical interface between the sensor and the surrounding rock mass. This avoids local sliding or stress transmission loss between the sensor and the coal and rock mass, ensuring that the displacement of the surrounding rock can be equivalently transmitted to the metal shell, and improving the fidelity of in-situ mining stress acquisition.

[0020] 2. This invention utilizes a polymer thermal insulation coating to fully encapsulate the temperature-compensated fiber grating. The thermal insulation coating absorbs the mechanical load transmitted by the hollow connecting rod through its own shear and tensile deformation, so that the temperature-compensated fiber grating only produces an optical response to changes in ambient temperature. The fiber demodulation equipment uses this as a reference to calculate the absolute temperature change and simultaneously deducts the thermal drift from the total wavelength change of the strained fiber grating, thus cutting off the cross-interference of the ambient thermal field on the mechanical strain measurement and extracting the net relative optical change caused purely by mechanical deformation.

[0021] 3. This invention physically connects water pressure-sensitive fiber Bragg gratings, four sets of strain fiber Bragg gratings, and temperature-compensated fiber Bragg gratings sequentially on a single through-fiber, and allocates non-overlapping wavelength operating ranges for multiple devices. The entire monitoring link uses silica fiber medium to transmit optical signals. The underground measurement nodes do not contain any electrical components. By utilizing wavelength division multiplexing mechanism, synchronous calculation of multi-physical field and multi-spatial node parameters is achieved on a single trunk fiber. While realizing large-capacity long-distance networking, it avoids interference from high-frequency alternating electromagnetic fields in mines at the physical level, and has the inherent safety characteristics to meet the requirements of high-gas confined spaces. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the device structure of the present invention;

[0023] Figure 2 This is a flowchart of the method of the present invention;

[0024] Figure 3 This is a comparative curve of the evolution of mining principal stress and pore water pressure with the advancing distance of the working face according to the present invention;

[0025] Figure 4 This is a comparison chart of the measured microstrain time series before and after the temperature cross-sensitivity compensation of the present invention.

[0026] The components include: 1. Outer shell; 2. Water pressure measuring unit; 3. Temperature-compensated fiber optic grating; 4. Strain fiber optic grating; and 5. Hollow connecting rod. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] See attached document Figure 1The present invention provides a device for simultaneously measuring mining stress, temperature and water pressure, which may include: a high-strength metal shell 1, a hollow connecting rod 5, a water pressure measuring unit 2, a strain measuring unit, a temperature measuring unit and a single through optical fiber.

[0029] A hollow connecting rod 5 is axially inserted inside the high-strength metal shell 1. The internal space of the hollow connecting rod 5 forms an optical fiber guiding channel.

[0030] The outer surface of the high-strength metal shell 1 is machined with spiral resin grouting channels. These spiral resin grouting channels constitute the installation coupling structure of the device. The helix angle of the spiral resin grouting channels is between 10 and 45 degrees. The cross-sectional geometry of the spiral resin grouting channels is semi-circular or trapezoidal. After the device is inserted into the borehole, resin is injected into the gap between the device and the borehole wall through the spiral resin grouting channels. After the resin cures, a rigid mechanical connection is formed between the high-strength metal shell 1 and the borehole rock mass.

[0031] The strain measurement unit is integrated into the inner wall of the high-strength metal casing 1. The strain measurement unit comprises four sets of strain fiber Bragg gratings 4 orthogonally distributed circumferentially along the high-strength metal casing 1. The four sets of strain fiber Bragg gratings 4 are orthogonally symmetrically distributed at 90 degrees on the same cross-section of the inner wall of the high-strength metal casing 1. The axis of each set of strain fiber Bragg gratings 4 extends parallel to the axis of the high-strength metal casing 1. Each set of strain fiber Bragg gratings 4 is fixed to the inner wall of the high-strength metal casing 1 using adhesive.

[0032] The temperature measuring unit is mounted on the hollow connecting rod 5. The temperature measuring unit includes a temperature-compensated fiber Bragg grating 3 and a heat-insulating coating covering the outside of the temperature-compensated fiber Bragg grating 3. The heat-insulating coating is made of polymer material and is used to isolate the mechanical stress generated between the high-strength metal shell 1 and the hollow connecting rod 5 from the transmission to the temperature-compensated fiber Bragg grating 3.

[0033] The water pressure measuring unit 2 is integrated into the front end of the high-strength metal casing 1. The water pressure measuring unit 2 includes, arranged sequentially from front to back along the device, a permeable cover plate, a permeable stone, an annular sealing ring, a water pressure sensitive cavity, a flexible diaphragm, a pressure transmitting rod, and a water pressure sensitive fiber optic grating. The permeable stone is made of sintered metal or porous ceramic material. The pores of the permeable stone allow water molecules to pass through while blocking rock fragments. The water pressure sensitive cavity is sealed by the annular sealing ring. The flexible diaphragm is arranged at the rear edge of the water pressure sensitive cavity and seals it. The first end of the pressure transmitting rod is fixedly connected to the center of the flexible diaphragm. The second end of the pressure transmitting rod is connected to the water pressure sensitive fiber optic grating. The water pressure sensitive fiber optic grating is in a pre-tensioned fixed state.

[0034] A single through-fiber is arranged within the fiber guiding channel formed by the hollow connecting rod 5. The water pressure sensitive fiber grating, four sets of strain fiber gratings 4, and temperature compensation fiber grating 3 are all connected in series to this single through-fiber.

[0035] The fiber optic demodulation equipment is connected to a single through-fiber. Within the same scanning cycle, the fiber optic demodulation equipment acquires the reflected center wavelength signals of the water pressure-sensitive fiber grating, each set of strain fiber gratings 4, and the temperature-compensated fiber grating 3 using wavelength division multiplexing technology.

[0036] The fiber optic demodulation equipment calculates the temperature change based on the center wavelength drift of the temperature-compensated fiber grating 3. Temperature change The calculation formula is:

[0037] ;

[0038] in, This indicates the center wavelength shift of temperature-compensated fiber grating 3; This indicates the initial center wavelength of temperature-compensated fiber grating 3; This represents the temperature sensitivity coefficient of the temperature-compensated fiber grating 3. The fiber optic demodulation equipment uses temperature changes to compensate for the wavelength shift of the four strain fiber gratings 4, thereby obtaining the strain signal caused by pure stress. Compensated strain values ​​of strain fiber grating 4 The calculation formula is:

[0039] ;

[0040] in, The value can be 1, 2, 3, or 4; Indicates the first The center wavelength shift of strained fiber grating 4; Indicates the first The initial center wavelength of the strain fiber grating 4; This represents the strain sensitivity coefficient of strain fiber grating 4; This represents the temperature sensitivity coefficient of the strain fiber grating 4. The fiber optic demodulation equipment substitutes the compensated strain values ​​of the four sets of strain fiber gratings 4, the elastic modulus of the high-strength metal shell 1, and the Poisson's ratio of the high-strength metal shell 1 into the elasticity equations to calculate the magnitude and direction of the two principal stresses in the plane perpendicular to the borehole axis.

[0041] The fiber optic demodulation equipment calculates the water pressure value based on the center wavelength drift of the water pressure-sensitive fiber Bragg grating. The calculation formula is:

[0042] ;

[0043] in, This indicates the center wavelength shift of the water pressure-sensitive fiber Bragg grating; This represents the overall pressure transmission calibration coefficient of water pressure sensitive unit 2. The center wavelength drift of the water pressure sensitive fiber grating is linearly related to the axial displacement of the pressure transmission rod.

[0044] The outer surface of the high-strength metal casing 1 is provided with a mounting coupling structure. This mounting coupling structure is a spiral resin grouting channel machined along the outer cylindrical surface of the high-strength metal casing 1. The spiral helix angle of the spiral resin grouting channel is between 10 degrees and 45 degrees.

[0045] The radial cross-sectional geometry of the spiral resin grouting channel is semi-circular or trapezoidal. When the cross-sectional shape is semi-circular, the continuous arc surface at the bottom of the channel reduces the concentration of mechanical deformation in that area. When the cross-sectional shape is trapezoidal, the inclined sidewalls of the trapezoid and the bottom surface of the channel form a multi-directional bearing surface, increasing the physical contact area between the high-strength metal shell 1 and the external filling medium.

[0046] During the initial installation phase of the device being inserted into the borehole, an unclosed annular gap exists between the outer surface of the high-strength metal casing 1 and the rock wall of the borehole. Liquid resin medium is injected into this annular gap. The spiral resin grouting channel, with a spiral angle structure between 10 and 45 degrees, restricts the direct flow velocity of the liquid resin medium, guiding it to flow spirally upwards along the surface of the high-strength metal casing 1. This spiral flow continuously discharges gas from the annular gap, ensuring a continuous distribution of the liquid resin medium within the annular gap and the spiral resin grouting channel.

[0047] After the liquid resin medium completes cross-linking and curing, it transforms into a solid resin layer. This solid resin layer fills the entire space between the borehole wall and the high-strength metal outer shell 1, and is completely embedded within the spiral resin grouting channel. The solid resin entity embedded within the spiral resin grouting channel forms a mechanical interlocking structure with the sidewall of the channel. This mechanical interlocking structure restricts axial relative displacement and circumferential relative rotation between the high-strength metal outer shell 1 and the solid resin layer.

[0048] The mechanical deformation of the borehole wall is transmitted to the high-strength metal shell 1 through the connected solid resin layer. The mechanical interlocking state formed by the solid resin layer and the spiral resin grouting channels on the surface of the high-strength metal shell 1 eliminates the deformation buffer interface outside the high-strength metal shell 1. The radial and tangential displacements of the borehole wall are converted into proportional strain parameters of the high-strength metal shell 1, and the three-dimensional mechanical changes of the borehole wall are synchronously transmitted to the inner wall of the high-strength metal shell 1.

[0049] The water pressure measuring unit 2 is integrated into the front end of the high-strength metal casing 1. The internal structure of the water pressure measuring unit 2, from front to back, includes a permeable cover plate, a permeable stone, an annular sealing ring, a water pressure sensitive cavity, a flexible diaphragm, a pressure transmitting rod, and a water pressure sensitive fiber optic grating.

[0050] A permeable cover plate is positioned at the foremost opening of the high-strength metal outer shell 1. Its main surface has multiple through-holes to prevent large rock fragments from entering. Permeable stones are positioned close to the rear surface of the permeable cover plate. These stones are made of sintered metal or porous ceramic materials and possess an interconnected network of micropores. The physical scale of the permeable stones' pores is larger than the diameter of a water molecule but smaller than the minimum particle size of common coal slime and rock cuttings found in drilling environments. Water flows through the inlet holes of the permeable cover plate and then enters the device through the micropore network of the permeable stones. Solid particles are trapped by the physical interference of the permeable stone's front surface and pore channels.

[0051] The rear side of the permeable stone is connected to the water pressure sensitive chamber. An annular sealing ring is arranged between the outer circumferential sidewall of the water pressure sensitive chamber and the front inner wall of the high-strength metal shell 1. The annular sealing ring is in a state of compression deformation, with its outer surface in contact with the inner wall of the high-strength metal shell 1 and its inner surface in contact with the sidewall of the water pressure sensitive chamber, sealing the axial flow channel of water to the rear region of the device.

[0052] A flexible diaphragm is positioned at the rear edge of the pressure-sensitive cavity. The periphery of the flexible diaphragm is physically fixed to the inner wall of the high-strength metal shell 1, forming the rearward boundary interface of the pressure-sensitive cavity. A pressure-transmitting rod is arranged along the axial geometric center line of the high-strength metal shell 1. The first end of the pressure-transmitting rod is fixedly connected to the surface geometric center of the flexible diaphragm. The second end of the pressure-transmitting rod is connected to the input end of the pressure-sensitive fiber optic grating.

[0053] Water flows through the permeable stone and enters the pressure-sensitive chamber, applying a normal distributed load to the front surface of the flexible diaphragm. Under this normal distributed load, the flexible diaphragm undergoes axial elastic deflection towards the rear of the device. The pressure-transmitting rod undergoes synchronous axial translational displacement with the displacement of the center point of the flexible diaphragm.

[0054] The output end of the water pressure-sensitive fiber Bragg grating is fixed to a rigid structural component inside a high-strength metal casing 1. During installation, the water pressure-sensitive fiber Bragg grating is subjected to axial tensile force and is in a pre-tensioned state. The axial translational displacement of the pressure-transmitting rod compresses the water pressure-sensitive fiber Bragg grating, reducing its tensile length under pre-tension. This change in tensile length causes a change in the physical dimensions of the grating period inside the water pressure-sensitive fiber Bragg grating, resulting in a drift of its reflected center wavelength. The axial displacement of the pressure-transmitting rod is linearly related to the water pressure on the flexible diaphragm, and the center wavelength drift is linearly related to the change in the grating tensile length. The corresponding pore water pressure value can be calculated by combining the center wavelength drift of the water pressure-sensitive fiber Bragg grating with the calibration coefficients set by the system.

[0055] A strain measurement unit is arranged on the inner wall of the high-strength metal shell 1. The strain measurement unit includes four sets of strain fiber Bragg gratings 4. The four sets of strain fiber Bragg gratings 4 are arranged in the hollow cavity inside the high-strength metal shell 1.

[0056] On the same cross-section of the inner wall of the high-strength metal shell 1, four sets of strain fiber gratings 4 are orthogonally and symmetrically distributed along the circumference of the high-strength metal shell 1 at 90-degree intervals. The geometrical arrangement axis of each set of strain fiber gratings 4 is parallel to the geometrical central axis of the high-strength metal shell 1. This spatial distribution structure extracts linear deformation data in four mutually perpendicular directions on the same cross-sectional circumference, providing independent equation input variables for the inversion calculation of the magnitude and direction of the two principal stresses in the plane perpendicular to the borehole axis from the thick-walled cylinder theory.

[0057] An adhesive is applied between each set of strain fiber Bragg gratings 4 and the inner wall of the high-strength metal casing 1. After curing, the adhesive forms a rigid adhesive layer between the strain fiber Bragg gratings 4 and the inner wall surface. The outer surface of the strain fiber Bragg gratings 4 is physically bonded to the inner wall of the high-strength metal casing 1 through this rigid adhesive layer. The rigid adhesive layer restricts the relative slippage between the strain fiber Bragg gratings 4 and the inner wall of the high-strength metal casing 1 in the axial and tangential directions.

[0058] Under the three-dimensional stress of the borehole wall, the wall material of the high-strength metal shell 1 undergoes radial and circumferential deformation. The material displacement on the inner surface of the high-strength metal shell 1 is converted into axial tensile or compressive stress of the corresponding strain fiber grating 4 through the rigid adhesive layer. The tensile or compressive deformation of the strain fiber grating 4 directly changes the physical dimensions of the grating period of its internal fiber core structure. The change in the grating period causes a drift in the center wavelength reflected by the strain fiber grating 4. By acquiring four sets of center wavelength drift values ​​with a 90-degree phase difference using fiber demodulation equipment, the specific micro-strain values ​​of the high-strength metal shell 1 in these four orthogonal directions are calculated.

[0059] A hollow connecting rod 5 is arranged axially inside the high-strength metal casing 1. The temperature measuring unit is fixed to the outer surface of the hollow connecting rod 5. The temperature measuring unit includes a temperature-compensated fiber Bragg grating 3 and a heat-insulating coating covering the outside of the temperature-compensated fiber Bragg grating 3.

[0060] The thermal insulation coating is made of a polymer material with low thermal conductivity and high elasticity. This polymer material is fully coated along the outer cylindrical surface of the temperature-compensating fiber grating 3, sealing the outer surface of the temperature-compensating fiber grating 3. The outer surface of the hollow connecting rod 5 and the outer surface of the temperature-compensating fiber grating 3 are physically separated by the thermal insulation coating made of this polymer material.

[0061] The mechanical deformation of the high-strength metal outer shell 1 caused by the external rock wall is transmitted to the hollow connecting rod 5. The axial and radial displacements on the surface of the hollow connecting rod 5 act on its externally adhered thermal insulation coating. The high elasticity of the thermal insulation coating causes it to undergo internal shear and tensile deformation, thereby absorbing the mechanical displacement on the surface of the hollow connecting rod 5. This deformation absorption mechanism blocks the physical path for the hollow connecting rod 5 to apply mechanical tensile or compressive loads to the temperature-compensated fiber grating 3. The temperature-compensated fiber grating 3 maintains a state of zero additional mechanical stress in its axial direction.

[0062] The temperature field of the underground mine environment is transferred through the internal space of the high-strength metal shell 1 to the hollow connecting rod 5 and the outer surface of the heat-insulating coating. Ambient heat penetrates the heat-insulating coating through thermal conduction, bringing the area containing the temperature-compensated fiber grating 3 to thermal equilibrium. The silica fiber core of the temperature-compensated fiber grating 3 undergoes thermal expansion and contraction with changes in ambient temperature, altering the physical length of the grating period. Simultaneously, the fiber core material exhibits a thermo-optical effect, changing its internal refractive index parameters.

[0063] The change in the physical dimensions of the grating period, in tandem with the change in refractive index, drives a shift in the optical center wavelength reflected by the temperature-compensated fiber grating 3. This center wavelength shift corresponds only to changes in ambient temperature. A single through-fiber is arranged along the channel space inside the hollow connecting rod 5, sequentially connecting the temperature-compensated fiber grating 3 at the rear, the strain measurement unit in the middle, and the water pressure measurement unit 2 at the front, all within the same optical path guiding channel. This center wavelength shift is transmitted through the single through-fiber to the fiber demodulation device, serving as the reference input data for thermal drift compensation of other parameters.

[0064] See attached document Figure 1 and attached Figure 2 The method provided by this invention includes inserting a device for simultaneously measuring mining stress, temperature, and water pressure into a pre-drilled test borehole in the mine. The device moves along the borehole axis to a predetermined depth. At this predetermined depth, an unclosed annular physical gap exists between the outer surface of the high-strength metal casing 1 and the rock wall of the test borehole.

[0065] One end of the grouting pipeline is connected to external grouting equipment, and the other end extends into the test borehole, establishing a fluid communication path with the spiral resin grouting channel outside the high-strength metal shell 1. The external grouting equipment pumps liquid resin medium into this fluid communication path. Under the pumping pressure, the liquid resin medium enters the annular physical gap outside the high-strength metal shell 1.

[0066] The helix angle and cross-sectional geometry of the spiral resin grouting channel physically constrain the flow trajectory of the liquid resin medium. The liquid resin medium propels itself in a spiral motion along the spiral resin grouting channel. This spiral propulsion process continuously expels the air originally contained within the annular physical gap to the outside of the test borehole. The liquid resin medium completely occupies the annular physical gap and the internal space of the spiral resin grouting channel.

[0067] The external grouting equipment stops pumping. The liquid resin medium filling the annular physical gap undergoes a chemical cross-linking reaction within a specified time period, transforming from a liquid phase to a solid phase, forming a solid resin entity. The outer peripheral surface of the solid resin entity forms a tightly fitted physical interface with the rock borehole wall of the test borehole. The inner peripheral surface of the solid resin entity adheres to the outer surface of the high-strength metal shell 1 and is completely embedded inside the spiral resin grouting channel.

[0068] The solid resin entity embedded within the spiral resin grouting channel forms a shear-resistant mechanical interlocking structure with the surface of the high-strength metal shell 1. Displacement changes in the surrounding rock mass caused by mining directly affect the solid resin entity. The mechanical interlocking structure restricts relative slippage or peeling between the solid resin entity and the high-strength metal shell 1. Rock mass displacement is converted into equivalent geometric deformation on the outer surface of the high-strength metal shell 1 through the solid resin entity, and the external three-dimensional stress load of the rock mass is transmitted to the various measuring units inside the high-strength metal shell 1 via this physical path.

[0069] The input end of the single through-fiber is connected to an optical fiber demodulation device located in the external environment. The extension of the single through-fiber passes through the hollow connecting rod 5 inside the high-strength metal shell 1. The water pressure-sensitive fiber grating inside the water pressure measurement unit 2, the four sets of strain fiber gratings 4 inside the strain measurement unit, and the temperature compensation fiber grating 3 inside the temperature measurement unit are arranged in series along the axis of the single through-fiber. All of the above grating assemblies are connected in series in the same continuous physical optical path.

[0070] To meet the wavelength division multiplexing (WDM) requirements, the water pressure-sensitive fiber grating, the four strain fiber gratings 4, and the temperature-compensated fiber grating 3 are configured during fabrication to have non-overlapping initial Bragg reflection wavelengths. The wavelength operating ranges of these six fiber gratings remain independent within the range of physical stretching or compression drift caused by the maximum environmental physical range, with no wavelength range overlap.

[0071] The broadband light source module inside the fiber optic demodulation device emits a continuous broadband spectral signal. This signal enters a single through-fiber through a physical interface and is sequentially transmitted to various fiber gratings located inside a high-strength metal casing 1. Temperature-compensated fiber gratings 3, four sets of strained fiber gratings 4, and water-pressure-sensitive fiber gratings respectively perform optical interference on this continuous broadband spectral signal. Each fiber grating reflects a narrowband center wavelength light signal from the continuous broadband spectral signal that matches the physical length of its current grating period. Other wavelength light signals that do not meet the reflection conditions are transmitted through the current fiber grating and transmitted to the next fiber grating.

[0072] The six narrowband center wavelength optical signals generated by the reflection of the six fiber gratings are physically superimposed within a single through-fiber, forming a composite reflected optical signal. The composite reflected optical signal is transmitted in reverse along the same single through-fiber and returns to the internal input port of the fiber demodulation device.

[0073] The spectral scanning module inside the fiber optic demodulation equipment performs wavelength scanning. Within a single wavelength scanning time period, the spectral scanning module performs wavelength decoding on the returned composite reflected light signal. Following six preset wavelength operating intervals, the spectral scanning module sequentially extracts the six independent center wavelength peak data for the corresponding temperature-compensated fiber grating 3, the four sets of strain fiber gratings 4, and the water pressure-sensitive fiber grating.

[0074] The aforementioned six independent center wavelength peak data are centrally output by a single fiber optic demodulation device within the same wavelength scanning time period. These six independent center wavelength peak data originate from the same high-strength metal casing 1 located at the same borehole geometric depth. The output six center wavelength peak data have a one-to-one physical correlation in both the time and spatial coordinate systems, providing original fundamental physical field data without time delay differences or spatial misalignment.

[0075] Four sets of strained fiber optic gratings 4, installed on the inner wall of the high-strength metal casing 1, are subjected to the combined physical effects of the surrounding rock mechanical stress and the downhole ambient temperature field. The center wavelength shift of these four sets of strained fiber optic gratings 4... It includes the mechanical strain response component caused by the mechanical deformation of the high-strength metal shell 1, and the thermal strain response component caused by the thermal expansion and contraction of the grating core material and the thermo-optic effect due to changes in ambient temperature.

[0076] To separate the two physical response components mentioned above, the fiber demodulation device extracts the center wavelength shift of the temperature-compensated fiber grating 3. The temperature-compensated fiber grating 3 is mechanically isolated by an external polymer thermal insulation coating; therefore, changes in the physical dimensions of its internal grating period and refractive index are driven only by changes in ambient temperature. The fiber optic demodulation equipment measures this center wavelength shift. Divide by the initial center wavelength of temperature-compensated fiber grating 3 With temperature sensitivity coefficient The product of these factors is used to calculate the absolute temperature change at the current measurement point. The temperature change obtained by the fiber optic demodulation equipment. Using the reference input parameters, a synchronous subtraction operation for thermally induced drift is performed on the wavelength scan data of the four sets of strained fiber Bragg gratings 4. For the first... The strained fiber grating 4 is used to extract the center wavelength shift using fiber demodulation equipment. Divide it by the initial center wavelength of the grating. The overall relative wavelength change, including thermophysical effects and mechanical strain effects, was calculated.

[0077] The fiber optic demodulation equipment will acquire the temperature change. With the inherent temperature sensitivity coefficient of strained fiber grating 4 Multiply by the above to calculate the thermally induced relative wavelength shift caused by the change in current ambient temperature on this strained fiber grating 4.

[0078] The fiber optic demodulation equipment subtracts the aforementioned thermally induced relative wavelength shift from the overall relative wavelength change. This subtraction operation eliminates the cross-interference of the ambient thermal field on the reflection spectrum of the strained fiber grating 4 from the data dimension, extracting the net relative optical change caused solely by the axial tension or compression of the high-strength metal casing 1.

[0079] The fiber optic demodulation equipment divides the extracted net relative optical change by the strain sensitivity coefficient of the strain fiber grating 4. This division operation converts the relative drift in the optical domain into the geometric deformation rate in the mechanical domain, ultimately outputting the first... Compensated strain values ​​of strain fiber grating 4 The strain values ​​after compensation in this group These constitute the basic mechanical boundary input conditions for subsequent three-dimensional mining stress inversion calculations.

[0080] See attached document Figure 2 The fiber optic demodulation equipment obtains the pre-calculated output of the absolute change in ambient temperature. The fiber optic demodulation equipment will measure this temperature change. An algebraic addition operation is performed with the initial reference temperature value at the borehole measuring point location. The output value of this addition operation is directly used as the actual ambient temperature physical quantity at the current measuring point location.

[0081] The fiber optic demodulation device extracts the optical center wavelength shift of the water pressure-sensitive fiber optic grating inside the water pressure measurement unit 2. The fiber optic demodulation equipment will determine the center wavelength shift. The integrated pressure transmission calibration coefficient set inside the water pressure measurement unit 2 Perform a product operation. This product operation linearly converts the optical wavelength drift scale into a hydrodynamic pressure scale. The product result output by the operation is the actual pore water pressure value inside the borehole environment at the current moment.

[0082] The fiber optic demodulation equipment acquires the compensated strain values ​​output from the four strain fiber gratings inside the strain measurement unit after prior calculation. The high-strength metal casing 1 has definite material elastic modulus and Poisson's ratio parameters. The storage medium inside the fiber optic demodulation device is pre-loaded with a set of mapping constitutive equations derived from the stress-deformation theory of thick-walled cylinders in elastic mechanics.

[0083] The above four post-compensation strain values These correspond to the actual tensile or compressive micro-strains of the inner wall of the high-strength metal casing 1 at four geometric orientations: 0 degrees, 90 degrees, 180 degrees, and 270 degrees. The fiber optic demodulation equipment will then convert these four compensated strain values. The elastic modulus and Poisson's ratio of the high-strength metal shell 1 are used as known boundary conditions and are simultaneously substituted into the system of mapping constitutive equations.

[0084] The microprocessor inside the fiber optic demodulation device performs numerical solutions to the mapping constitutive equations. The output variables of the solution include the maximum and minimum plane principal stress values, as well as the direction angle of the principal stresses, on the plane perpendicular to the axis of the high-strength metal shell 1. The maximum and minimum plane principal stress values ​​reflect the two-dimensional stress state on the section perpendicular to the borehole axis.

[0085] The fiber optic demodulation equipment, based on the acquired two-dimensional stress state parameters, superimposes the stress response state settings along the borehole axial direction and performs a spatial geometric tensor reconstruction operation. This spatial geometric tensor reconstruction operation combines the force scalars in different directions with the angular directions to form a spatial stress matrix. Each element of the spatial stress matrix corresponds to the three-dimensional mining stress components of the surrounding rock mass in a spatial rectangular coordinate system, thus outputting a complete in-situ three-dimensional mining stress state.

[0086] The aforementioned devices for simultaneously measuring mining stress, temperature, and water pressure are deployed at multiple different borehole locations within the underground physical space of the mine. These devices form a physical measurement node array in spatial distribution. A main transmission optical fiber extends in the physical space, and the individual through-fibers within these multiple devices are physically connected in series sequentially.

[0087] Inside the device located at the previous spatial geometric position, the output end of its single through-fiber is connected via fiber optic fusion splicing or a physical fiber optic connector to establish a continuous optical transmission physical path with the input end of a single through-fiber located inside the device at the next spatial geometric position. This continuous optical transmission physical path constitutes a pure optical transmission channel covering multiple distributed nodes. The physical layout length of this optical transmission channel is extended according to the actual spatial orientation of the mine roadway, and its continuous physical span is set to be over 1000 meters.

[0088] The physical interface of the fiber optic demodulation device is connected to the starting input end of the backbone transmission fiber. To achieve data multiplexing of multiple spatially distributed nodes within the same physical optical path, the fiber Bragg grating assemblies within the multiple devices perform global band splitting configuration based on the initial center wavelength parameters. The backbone transmission fiber is set to have a physical series connection of [number missing]. The device, an optical fiber demodulation equipment, outputs broadband light with a fixed physical spectral bandwidth from its light source module. This fixed physical spectral bandwidth is divided into [a specific range] within the frequency domain. Each wavelength operating range is independent and does not overlap.

[0089] In the first Inside the device at each spatial geometric location, the water pressure-sensitive fiber grating in the water pressure measurement unit 2, the four sets of strain fiber gratings 4 in the strain measurement unit, and the temperature-compensating fiber grating 3 in the temperature measurement unit are physically fabricated to correspond to the respective... The broadband optical signal is generated by an optical fiber demodulation device, propagates forward along the trunk transmission fiber, and sequentially penetrates all devices along the physical transmission path. It consists of six independent bands within the operating wavelength range.

[0090] The devices at each node reflect narrowband center wavelength optical signals that match their pre-assigned six independent bands. A total of six signals are generated by all nodes. Narrowband center-wavelength optical signals, carrying spatial location markers and physical deformation variables, are superimposed within the same trunk transmission fiber and transmitted back to the input port of the fiber optic demodulation equipment. The spectral scanning module of the fiber optic demodulation equipment analyzes the returned composite optical signal within a fixed wavelength scanning time period, extracting the 6... Individual wavelength peak data.

[0091] The processor inside the fiber optic demodulation device binds the extracted wavelength peak data to the three-dimensional coordinate system of the borehole based on a pre-stored wavelength allocation mapping table. Based on the aforementioned wavelength drift calculation rules, the processor synchronously calculates and outputs the pore water pressure, three-dimensional mining stress spatial geometric tensor, and absolute ambient temperature values ​​at all node locations along the optical transmission channel. This serial network topology and its internal measurement units do not contain any electrical components requiring external current; the entire sensing and data transmission process of the monitoring physical link is completed using purely optical media.

[0092] A single through-fiber or backbone transmission fiber extends from the test borehole underground in the mine to the mine's surface monitoring center. Fiber optic demodulation equipment is located within the surface monitoring center. Multiple devices located underground simultaneously measuring mining stress, temperature, and water pressure establish physical transmission links with the fiber optic demodulation equipment at the surface monitoring center via the single through-fiber or backbone transmission fiber. This physical transmission link is made solely of silica fiber optic media. Broadband optical signals and composite reflected optical signals are transmitted bidirectionally within this physical transmission link, forming a closed-loop long-distance optical communication from the in-situ physical measurement points underground to the surface equipment.

[0093] The high-strength metal casing 1, water pressure measurement unit 2, strain measurement unit, and temperature measurement unit, deployed inside the test borehole in the mine, are all assembled from mechanical structural components and optical elements. The flexible diaphragm and pressure-transmitting rod inside the water pressure measurement unit 2, the strain fiber grating 4 inside the strain measurement unit, and the temperature-compensated fiber grating 3 inside the temperature measurement unit rely on the mechanical linkage between physical deformation and the grating period when sensing changes in the external physical field. Throughout the entire operating cycle of acquiring physical field parameters and transmitting the center wavelength drift signal, none of these components are connected to any power cables or energetic electrical circuits, and the entire device operates in a purely passive physical state.

[0094] The purely passive physical state eliminates the physical conditions for electrical short circuits, electrostatic discharges, or the generation of electric sparks within the underground device. In the confined space of a mine containing methane gas and coal dust, the device and its connected fiber optic network do not possess the physical energy output mechanism to ignite an explosive mixture during operation.

[0095] In a single through-fiber, photons are the carriers of light, and the optical signal propagates physically within the silica core following the law of total internal reflection. The high-intensity alternating electromagnetic fields generated by large mining equipment or high-voltage power grids in underground mines cannot electromagnetically couple with the photons propagating within the fiber core. Therefore, these high-intensity alternating electromagnetic fields do not physically interfere with the optical transmission trajectory, intensity, or frequency characteristics within the single through-fiber. The center wavelength drift data reflected by each fiber Bragg grating distributed underground is independent of external electromagnetic environment parameters, preventing electromagnetic noise from being superimposed on the fundamental physical field data.

[0096] The fiber optic demodulation equipment deployed at the ground monitoring center continuously receives composite reflected light signals from various physical measurement nodes underground. The processor inside the demodulation equipment performs wavelength decoding, cross-sensitivity cancellation calculations, and multi-physics parameter numerical calculations. The calculated output values ​​for pore water pressure, three-dimensional mining stress space geometry tensor, and absolute ambient temperature at each node are directly written and recorded in the storage medium at the ground monitoring center. This topology completely isolates the signal processing modules, which contain electronic components and require external power, from the underground mining environment.

[0097] Specific application examples:

[0098] See attached document Figure 3 In a high-gas mine, the method and apparatus provided by this invention were applied and compared in a field test in the transport roadway of the 8102 high-extraction longwall face. The test borehole was drilled perpendicular to the roadway sidewall into the solid coal seam, with a drilling depth of 20 meters and a diameter of 75 millimeters. Simultaneously, devices for measuring mining-induced stress, temperature, and water pressure were inserted into the bottom of the borehole via a pusher. External grouting equipment injected two-component polyurethane resin into a spiral resin grouting channel at a pumping pressure of 1.5 MPa. The resin completed polymerization and cross-linking within 25 minutes, forming a solid resin entity with a Shore hardness of D80, achieving high-rigidity mechanical coupling between the high-strength metal shell 1 and the coal seam borehole wall.

[0099] To establish a rigorous experimental control group, a parallel borehole with identical geometric parameters was drilled 2 meters laterally from the test borehole. A conventional vibrating wire borehole stress gauge and a piezoresistive permeable piezometer were installed in this borehole. All these conventional electrical sensors were connected to an explosion-proof data acquisition substation within the tunnel via shielded cables. The device of this invention is connected to a fiber optic demodulation device located in the surface control room via a single through-fiber optic cable. The broadband light source configured in the fiber optic demodulation device has a wavelength coverage range of 1510 nm to 1590 nm. The initial center wavelengths of the pressure-sensitive fiber grating, the four sets of strain fiber gratings 4, and the temperature-compensated fiber grating 3 are discretely calibrated to approximately 1530, 1540, 1545, 1550, 1555, and 1565 nm, respectively, to ensure that the physical addressing space for wavelength drift does not overlap.

[0100] As the longwall mining face continues to advance, the original rock stress field inside the rock strata is disturbed and redistributed. Figure 3 The horizontal axis represents the advance physical distance between the working face and the test borehole, while the vertical axis represents the maximum plane principal stress value calculated from the mapping constitutive equations and the pore water pressure value converted from the comprehensive pressure transmission calibration coefficient, respectively. When the working face advances to 40 meters from the measuring point, the mining-induced stress begins to show a nonlinear growth trend. Traditional vibrating wire sensors produce numerous discrete abrupt noise points in their data curves. This phenomenon is caused by the high-frequency alternating electromagnetic field generated during the cutting operation of the 3300-volt high-pressure coal mining machine penetrating the cable shielding layer and inducing electromotive force interference in the analog-to-digital conversion circuit. In contrast, this invention, based on a wavelength encoding mechanism using pure silica optical fiber, possesses natural physical immunity to spatial electromagnetic fields. The calculated maximum plane principal stress curve and pore water pressure curve exhibit extremely high smoothness and signal-to-noise ratio, accurately capturing the peak advance support pressure (32.6 MPa) located 14.5 meters ahead of the working face, and simultaneously recording the step drop in water pressure caused by the penetration of mining-induced fractures.

[0101] See attached document Figure 4 Throughout the 60-day monitoring period, due to the frequency conversion start and stop of the underground local ventilation fan and the release of the geothermal gradient, the ambient temperature at the monitoring point fluctuated irregularly between 18.5 degrees Celsius and 26.2 degrees Celsius. Figure 4 Uncompensated strain curves were extracted from one set of strain fiber gratings 4, directly converted from the original center wavelength drift. Due to the physical superposition of thermal expansion and contraction of silica material and thermo-optical effects, the uncompensated strain curves exhibited baseline drift highly correlated with temperature fluctuations, with the maximum thermally induced virtual strain error reaching 145 microstrains, severely masking the true slow rheological signal of the coal body.

[0102] By introducing the wavelength drift of temperature-compensated fiber grating 3 for synchronous algebraic calculation, the microprocessor inside the fiber demodulation device performs real-time subtraction of the thermally induced drift. Figure 4 The post-compensation strain curve, processed by the cross-sensitivity elimination algorithm, completely filters out low-frequency baseline fluctuations caused by the environmental thermal field. During the resting period when the solid resin entity outside the high-strength metal shell 1 does not experience significant shear failure, the variance of the post-compensation strain curve converges to within 2.1 microstrain, fully verifying the physical isolation mechanism provided by the polymer thermal insulation coating and the extremely high robustness of the wavelength differential compensation algorithm in multi-field coupling environments. These experimental data not only confirm the high fidelity of the present invention in synchronous sensing of multiple physics fields under complex working conditions, but also demonstrate its absolute engineering and technical advantages in replacing traditional electronic state monitoring equipment that is susceptible to both electromagnetic and temperature interference.

Claims

1. A method for measuring mining stress, temperature, and water pressure, characterized in that, Includes the following steps: The device for measuring mining stress, temperature and water pressure is sent into the test borehole in the mine. Liquid resin medium is injected into the outside of the high-strength metal shell (1). The liquid resin medium solidifies to form a solid resin entity to achieve in-situ installation and rigid coupling in the mine. The device for measuring mining stress, temperature and water pressure includes: a high-strength metal shell (1) with a hollow connecting rod (5) arranged axially inside. Water pressure measuring unit (2) is located at the front end of the high-strength metal shell (1) and is equipped with a water pressure sensitive fiber optic grating inside; The strain measurement unit is located in the middle of the high-strength metal shell (1) and includes four sets of strain fiber gratings (4) installed on the inner wall of the middle of the high-strength metal shell (1). The temperature measuring unit is fixed to the outer surface of the hollow connecting rod (5) and includes a temperature-compensated fiber optic grating (3) and a heat-insulating coating covering the outside of the temperature-compensated fiber optic grating (3). A single through-fiber passes through the hollow connecting rod (5), and the water pressure sensitive fiber grating, the four sets of strain fiber gratings (4) and the temperature compensation fiber grating (3) are arranged in series along the axis of the single through-fiber. An optical fiber demodulation device that establishes a continuous physical path for optical transmission with the input end of the single through-fiber. The fiber demodulation device emits a continuous broadband spectral signal, which is transmitted sequentially through the single through-fiber to the water pressure sensitive fiber grating, the four sets of strain fiber gratings (4) and the temperature compensation fiber grating (3), and receives the back-transmitted composite reflected light signal to extract the center wavelength peak data of each grating. The absolute temperature change of the environment is calculated based on the center wavelength peak data of the temperature-compensated fiber grating (3), and the thermally induced relative wavelength drift of the four strain fiber gratings (4) is deducted based on the absolute temperature change of the environment, and the corresponding compensated strain value is extracted. The true pore water pressure value is calculated and output based on the center wavelength peak data of the water pressure sensitive fiber grating and the comprehensive pressure transmission calibration coefficient. Substituting the four compensated strain values ​​into the mapping constitutive equations derived from the stress-deformation theory of thick-walled cylinders based on elasticity, the in-situ three-dimensional mining stress state is inverted and output.

2. The method for measuring mining stress, temperature, and water pressure according to claim 1, characterized in that, The outer surface of the high-strength metal shell (1) is provided with a spiral resin injection channel; The spiral resin grouting channel is embedded with a solid resin entity generated by a multi-component chemical cross-linking reaction. The inner circumferential surface of the solid resin entity and the surface of the high-strength metal shell (1) form a mechanical interlocking structure, which is used to convert the external rock mass displacement into the same geometric deformation of the outer surface of the high-strength metal shell (1).

3. The method for measuring mining stress, temperature, and water pressure according to claim 1, characterized in that, The water pressure measuring unit (2) also includes a permeable cover plate, permeable stone, flexible diaphragm and pressure transmission rod; The permeable cover plate and the permeable stone are arranged on the front water-facing side. External pore water sequentially penetrates the permeable cover plate and the permeable stone and enters the water pressure sensitive cavity to act on the flexible membrane. The mechanical deformation of the flexible diaphragm is transmitted to the water pressure-sensitive fiber grating through the pressure transmission rod, driving the grating period of the water pressure-sensitive fiber grating to undergo physical deformation.

4. The method for measuring mining stress, temperature, and water pressure according to claim 1, characterized in that, The heat insulation coating is made of polymer material and is formed by fully covering the outer cylindrical surface of the temperature-compensated fiber grating (3); The heat-insulating coating is used to absorb the axial and radial displacement of the surface of the hollow connecting rod (5) by undergoing internal shear and tensile deformation, blocking the physical path of the hollow connecting rod (5) to apply mechanical tensile or compressive loads to the temperature-compensating fiber grating (3), and maintaining the temperature-compensating fiber grating (3) in a state of zero additional mechanical stress in the axial direction.

5. The method for measuring mining stress, temperature, and water pressure according to claim 1, characterized in that, Injecting liquid resin medium into the exterior of the high-strength metal casing (1) to achieve in-situ installation and rigid coupling specifically includes: The external grouting equipment pumps the liquid resin medium into the spiral resin grouting channel outside the high-strength metal shell (1); The liquid resin medium is physically constrained by the helix angle and cross-sectional geometry of the spiral resin grouting channel, resulting in a spiral propulsion flow that continuously discharges air from inside the test borehole to the outside. The liquid resin medium undergoes a chemical cross-linking reaction to transform into the solid resin entity, and the inner circumferential surface of the solid resin entity is completely embedded inside the spiral resin grouting channel to construct a physical interface with shear resistance.

6. The method for measuring mining stress, temperature, and water pressure according to claim 1, characterized in that, Extracting the center wavelength peak data of each grating specifically includes: The water pressure sensitive fiber grating, the four sets of strain fiber gratings (4) and the temperature compensation fiber grating (3) are configured to have non-overlapping initial Bragg reflection wavelength operating ranges; Each fiber grating reflects a narrowband center wavelength optical signal from the continuous broadband spectral signal that matches the physical length of the current grating period of each fiber grating; Multiple narrowband center wavelength optical signals are physically superimposed within the same single through-fiber to form the composite reflected optical signal; The spectral scanning module of the fiber demodulation device performs wavelength decoding on the composite reflected light signal and extracts the independent center wavelength peak data of each fiber grating in sequence according to the preset wavelength working range.

7. The method for measuring mining stress, temperature, and water pressure according to claim 1, characterized in that, After deducting the thermally induced relative wavelength shift of the four sets of strained fiber gratings (4), the corresponding compensated strain values ​​are extracted, specifically including: Divide the center wavelength drift of the temperature-compensated fiber grating (3) by the product of the initial center wavelength of the temperature-compensated fiber grating (3) and the temperature sensitivity coefficient to obtain the absolute temperature change of the current measurement point environment. Extract the center wavelength drift of the strained fiber grating (4) and divide the center wavelength drift by the initial center wavelength of the strained fiber grating (4) to obtain the overall relative wavelength change. The thermally induced wavelength relative shift is calculated by multiplying the absolute temperature change of the environment by the temperature sensitivity coefficient of the strained fiber grating (4). The net optical relative change is obtained by subtracting the thermally induced wavelength relative drift from the total relative wavelength change. The net optical relative change is divided by the strain sensitivity coefficient of the strained fiber grating (4) to convert the optical domain relative drift into the mechanical domain geometric deformation rate, and the compensated strain value is output.

8. The method for measuring mining stress, temperature, and water pressure according to claim 1, characterized in that, The in-situ three-dimensional mining stress state output by inversion specifically includes: The four post-compensation strain values, the elastic modulus parameter of the high-strength metal shell (1), and the Poisson's ratio parameter are used as known boundary conditions and simultaneously substituted into the mapping constitutive equation system. Numerical solution operations are performed on the mapping constitutive equations to obtain the maximum plane principal stress, the minimum plane principal stress, and the direction angle of the principal stress in the plane perpendicular to the axis of the high-strength metal shell (1). Based on the acquired two-dimensional stress state parameters, the stress response state settings in the borehole axial direction are superimposed, and a spatial geometric tensor reconstruction operation is performed to generate a three-dimensional stress matrix in the corresponding spatial rectangular coordinate system, and the in-situ three-dimensional mining stress state is output.

9. The method for measuring mining stress, temperature, and water pressure according to claim 1, characterized in that, It also includes the data acquisition steps for constructing a high-capacity fiber optic multiplexing network topology: Multiple sets of the aforementioned devices for measuring mining stress, temperature, and water pressure are deployed at different test borehole locations underground in the mine to form a physical measurement node array; The single through-fibers inside the multiple sets of devices are physically connected in series sequentially through a main transmission fiber. The backbone transmission fiber is physically connected with N devices. The fiber demodulation device emits broadband light with a fixed physical spectral bandwidth. The fixed physical spectral bandwidth is divided into 6N non-overlapping independent wavelength working intervals in the frequency domain by a global band. The devices at each node reflect optical signals that match the pre-allocated wavelength bands and superimpose them on the same backbone transmission fiber for back transmission, thereby achieving synchronous calculation of multi-node parameters under the pure optical transmission mechanism of the entire link.

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