Continuous mining-induced stress measurement method based on wrapped distributed optical fiber

Abstract

The application relates to the technical field of geotechnical engineering safety monitoring and engineering testing, and provides a continuous mining stress measurement method based on a winding distributed optical fiber. The continuous mining stress measurement method comprises the following steps: drilling a cylindrical monitoring drill hole in a to-be-monitored area affected by mining; implanting a cylindrical sensor into the monitoring drill hole, the surface of the cylindrical sensor being fixed with a distributed optical fiber wound along a preset spiral path to form a continuous distributed equivalent three-way strain roset array; filling a coupling material between the cylindrical sensor and the hole wall of the monitoring drill hole, so that the cylindrical sensor and the surrounding rock of the monitoring drill hole form a rigid coupling body; connecting the end of the distributed optical fiber to a distributed optical fiber demodulation system, collecting continuous strain data of the whole domain of the cylindrical sensor in a mining process; and based on the collected continuous strain data, combining the elastic mechanics parameters of a rock mass, and solving to obtain continuous mining stress data of the whole domain of the monitoring drill hole.

Description

Technical Field

[0001] This application relates to the field of geotechnical engineering safety monitoring and engineering testing technology, specifically to a method for measuring continuous mining stress based on wound distributed optical fibers. Background Technology

[0002] In geotechnical engineering projects such as deep mining, tunnel excavation, and dam foundation disturbance, mining activities trigger continuous dynamic evolution of the surrounding rock stress field. Accurate monitoring of mining stress is a core technology for ensuring the stability of engineering structures and the safety of construction and operation. Currently, the industry still relies primarily on traditional point-based monitoring equipment such as hollow inclusion stress gauges and oil bladder stress gauges for mining stress measurement. These monitoring methods have significant technical limitations in practical engineering applications and are difficult to adapt to the full-cycle monitoring needs under complex mining environments.

[0003] Traditional point-based stress monitoring equipment can only collect stress data at discrete points, failing to cover the stress field across the entire structural area of ​​the monitoring region. During the continuous dynamic migration of mining stress with engineering activities, this discrete monitoring mode is prone to missing key nodes of local stress concentration and dynamic stress abrupt changes, failing to fully capture the full-space evolution of the surrounding rock stress field under the influence of mining. Furthermore, the deployment cost of a single point-based monitoring device is high, and the number of devices that can be deployed on-site is extremely limited. It can only extrapolate the overall stress field distribution through data interpolation from a small number of discrete points, unable to form a continuous, high-density stress distribution characterization within the monitoring area, making it difficult to support refined surrounding rock stability analysis and engineering safety assessment. In addition, traditional point-based stress gauges have poor adaptability to the harsh environments of mining projects. The high stress, strong disturbances, and moisture corrosion of deep surrounding rock can easily cause damage and failure of individual monitoring devices. The failure of a single device will directly lead to the loss of data at the corresponding monitoring location, not only disrupting the integrity of the monitoring sequence but also significantly increasing the operation and maintenance costs and data reliability risks of the monitoring system. Summary of the Invention

[0004] This application provides a method for continuous mining stress measurement based on wound distributed optical fiber, which solves the problem that mining stress measurement data cannot cover the entire structure in the prior art, and realizes continuous measurement of mining stress.

[0005] A method for continuous sampling stress measurement based on wound distributed optical fiber according to an embodiment of the first aspect of this application includes the following steps: Drill cylindrical monitoring boreholes in the monitoring area affected by mining activities; A cylindrical sensor is implanted into the monitoring borehole. Distributed optical fibers wound along a preset spiral path are fixed on the surface of the cylindrical sensor. The distributed optical fibers wound along the preset spiral path form a continuously distributed equivalent triaxial strain rose array on the surface of the cylindrical sensor. Coupling material is filled between the cylindrical sensor and the borehole wall to form a rigid coupling body between the cylindrical sensor and the surrounding rock of the monitoring borehole. The end of the distributed optical fiber is connected to the distributed optical fiber demodulation system to collect continuous strain data of the entire area of ​​the cylindrical sensor during the sampling process. Based on the collected continuous strain data and combined with the elastic mechanical parameters of the rock mass, the continuous mining stress data of the entire monitoring borehole area is calculated.

[0006] According to one embodiment of this application, drilling a cylindrical monitoring borehole in the monitoring area affected by mining activities includes: According to the preset monitoring plan, monitoring boreholes are drilled in the top, bottom, side or target monitoring body of the surrounding rock in the area to be monitored, along the vertical, horizontal or inclined direction. After the monitoring borehole is completed, high-pressure air or clean water is used to remove rock powder and loose debris from the borehole. The inner diameter of the monitoring borehole is 5mm to 20mm larger than the outer diameter of the sensor, and the depth of the monitoring borehole covers the mining impact range of the area to be monitored.

[0007] According to one embodiment of this application, prior to implanting the cylindrical sensor into the monitoring borehole, the method further includes: A rigid cylindrical substrate adapted to the monitoring borehole was selected as the sensor substrate; Distributed optical fibers are wound along a preset spiral path on the outer surface of the sensor substrate; Distributed optical fibers are laid along a preset axial path on the outer surface of the sensor substrate; By using an adhesive bonding method, the wound optical fiber is fixed to the outer surface of the sensor substrate, forming a wound optical fiber sensor with full-range strain sensing capability.

[0008] According to one embodiment of this application, the step of winding distributed optical fibers along a preset spiral path on the outer surface of the sensor substrate includes: At least two independent distributed optical fibers are wound around the outer surface of the sensor substrate; Each distributed optical fiber is continuously wound along the axial direction of the sensor substrate with the same helix angle and pitch. The winding parameters of each distributed optical fiber are matched to form a continuously distributed equivalent triaxial strain flower array on the surface of the sensor substrate.

[0009] According to one embodiment of this application, the number of distributed optical fibers wound along a preset spiral path is 2, and the number of distributed optical fibers laid along a preset axial path is 3.

[0010] According to one embodiment of this application, the step of connecting the end of the distributed optical fiber to a distributed optical fiber demodulation system to collect continuous strain data of the entire domain of the cylindrical sensor during the sampling process includes: Set the spatial sampling interval, acquisition frequency, and measurement range parameters of the distributed optical fiber demodulation system; Throughout the entire mining process, strain data from all measuring points on each distributed optical fiber are simultaneously acquired through a demodulation system, resulting in a continuous strain dataset covering the entire sensor domain.

[0011] According to one embodiment of this application, before calculating the continuous mining stress data of the entire monitoring borehole area based on the collected continuous strain data and the elastic mechanical parameters of the rock mass, the method further includes: Perform a modulo operation on the helix angle parameters of all measuring points to uniformly map the circumferential angles of all measuring points to a numerical range of 0 to 2π.

[0012] According to one embodiment of this application, after performing a modulo operation on the helix angle parameters of all measuring points to uniformly map the circumferential angles of all measuring points to a numerical range of 0 to 2π, the method further includes: Based on the actual radius of the sensor substrate, the uniformly mapped circumferential angle is converted into the equivalent lateral arc length of the corresponding cylindrical surface; A planar unfolded coordinate system matching the geometric features of the sensor's cylindrical surface is established, with the equivalent transverse arc length as the transverse coordinate and the axial position of the measuring point as the longitudinal coordinate. Complete the coordinate transformation of all measuring points to obtain the unique planar unfolded coordinates corresponding to each measuring point.

[0013] According to one embodiment of this application, the calculation of continuous mining stress data across the entire monitoring borehole area based on the collected continuous strain data and the elastic mechanical parameters of the rock mass includes: Based on the planar unfolded coordinates of each measuring point, multiple sets of strain data corresponding to the measuring points are matched, and the three-dimensional strain tensor of each measuring point is obtained by solving the least squares method. By combining the elastic modulus and Poisson's ratio parameters of the surrounding rock to be monitored, a three-dimensional stress-strain constitutive relationship matrix of elasticity is constructed. Based on the three-dimensional stress-strain constitutive relation matrix of elasticity, the three-dimensional mining stress value of each measuring point is calculated.

[0014] According to one embodiment of this application, after calculating the three-dimensional mining stress values ​​at each measuring point, the method further includes: The three-dimensional mining stress values ​​obtained from each measuring point are correlated with the plane unfolded coordinates and spatial position coordinates of the corresponding measuring points to generate a continuous mining stress data set for monitoring the entire borehole area. Based on the continuous mining stress data set, a planar unfolded continuous mining stress distribution map of the monitoring borehole is generated with the planar unfolded coordinates as the reference, and a three-dimensional cylindrical surface mining stress cloud map of the monitoring borehole is generated with the spatial position coordinates as the reference; the distribution map and cloud map are used for stability analysis and safety assessment of mining projects.

[0015] The above-described one or more technical solutions in the embodiments of this application have at least one of the following technical effects: This application's method for continuous mining stress measurement based on wound distributed optical fibers utilizes a cylindrical sensor with distributed optical fibers fixed along a spiral path on its surface. Continuous strain data is acquired through the continuous optical fibers, and then continuous mining stress data is obtained through corresponding conversion and calculation. Utilizing the spatial angular distribution characteristics of the distributed optical fibers, a continuous equivalent three-dimensional strain flower network is constructed on the structural surface, enabling continuous measurement of mining stress across the entire borehole. This eliminates the need for discretely deployed multi-point stress gauges; a three-dimensional strain sensing system can be established solely through distributed optical fibers, directly demodulating continuous mining stress data. This solves the problems of insufficient coverage, discontinuous data, and poor adaptability associated with traditional point-based monitoring, providing accurate, real-time, and continuous stress data support for mining engineering safety assessment. This application breaks through the traditional monitoring mode of combining multiple sets of discrete point-based hollow inclusion stress gauges, achieving continuous mining stress sensing across the entire borehole area. It not only fundamentally solves the core pain points of insufficient coverage and discontinuous data in traditional point-based monitoring but also represents a fundamental upgrade in mining stress measurement from discrete single-point measurement to continuous distributed measurement across the entire borehole.

[0016] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating the continuous mining stress measurement method based on wound distributed optical fiber provided in this application.

[0019] Figure 2 This is a schematic diagram of the cylindrical sensor provided in this application being implanted to monitor the state inside the borehole. Figure 1.

[0020] Figure 3 This is a schematic diagram of the cylindrical sensor provided in this application being implanted to monitor the state inside the borehole. Figure 2 .

[0021] Figure 4 This is a schematic diagram of the cylindrical sensor provided in this application, which is equipped with distributed optical fibers.

[0022] Figure 5 This is a schematic diagram of the cylindrical sensor provided in this application after it has been unfolded (for mathematical calculations, the cylindrical sensor is imaginarily unfolded, and the black dots represent measuring points on a spiral optical fiber; only measuring points on a spiral optical fiber are shown).

[0023] Figure label: 1. Cylindrical sensor; 11. Distributed optical fiber; 2. Coupling material; 3. Surrounding rock; 31. Monitoring borehole. Detailed Implementation

[0024] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this application, but should not be used to limit the scope of this application.

[0025] In the description of the embodiments of this application, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0027] In the embodiments of this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0028] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the embodiments of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0029] According to an embodiment of the first aspect of this application, a method for continuous sampling stress measurement based on wound distributed optical fiber is provided, such as... Figure 1 As shown, the process includes the following steps: drilling a cylindrical monitoring borehole 31 in the area to be monitored by mining; implanting a cylindrical sensor 1 into the monitoring borehole 31, with a distributed optical fiber 11 wound along a preset spiral path fixed on the surface of the cylindrical sensor 1, forming a continuously distributed equivalent triaxial strain flower array on the surface of the cylindrical sensor 1; filling the space between the cylindrical sensor 1 and the borehole wall of the monitoring borehole 31 with coupling material 2, so that the cylindrical sensor 1 and the surrounding rock 3 of the monitoring borehole 31 form a rigid coupling body; connecting the end of the distributed optical fiber 11 to a distributed optical fiber demodulation system to collect continuous strain data of the entire area of ​​the cylindrical sensor 1 during mining; and calculating the continuous mining stress data of the entire area of ​​the monitoring borehole 31 based on the collected continuous strain data and the elastic mechanical parameters of the rock mass.

[0030] The traditional discrete single-point strain sensing is transformed into a continuous three-dimensional strain sensing system across the entire borehole by using a distributed optical fiber 11 spirally wound on the surface of a cylindrical sensor 1. The monitoring borehole 31 provides a space for the sensor to fit tightly against the surrounding rock 3, and the coupling material 2 eliminates the interface gap between the sensor and the surrounding rock 3, ensuring lossless stress transmission in the surrounding rock 3. The distributed optical fiber demodulation system synchronously acquires the strain signal of the entire distributed optical fiber 11, and the elastic mechanical parameters of the rock mass serve as the calculation medium for strain-to-stress conversion, ultimately achieving continuous calculation of mining-induced stress across the entire borehole range.

[0031] The aforementioned continuous mining stress measurement method overcomes the technical limitations of traditional point-based stress monitoring. It constructs a continuous equivalent triaxial strain rosette network using helically wound distributed optical fibers, enabling a leap from single-point discrete measurement to continuous measurement across the entire borehole. This eliminates the need for numerous discrete stress gauges; a single sensor can complete three-dimensional stress sensing across the entire borehole, significantly reducing monitoring deployment costs and avoiding data loss due to single-point failures. The method accurately captures the dynamic evolution and local concentration characteristics of stress during mining operations, providing real-time, continuous, and high-precision stress data support for mining engineering safety assessments.

[0032] According to one embodiment of this application, drilling a cylindrical monitoring borehole 31 in the area to be monitored by mining impact includes: drilling the monitoring borehole 31 in the top plate, bottom plate, sidewall or target monitoring body of the surrounding rock 3 in the area to be monitored in a vertical, horizontal or inclined direction according to a preset monitoring plan; after the monitoring borehole 31 is drilled, rock powder and loose debris in the borehole are removed by high pressure air or clean water; wherein, the inner diameter of the monitoring borehole 31 is 5mm to 20mm larger than the outer diameter of the sensor, and the depth of the monitoring borehole 31 covers the mining impact range of the area to be monitored.

[0033] Figure 2 and Figure 3 This is a schematic diagram showing the state of the cylindrical sensor 1 implanted in the monitoring borehole 31, where, Figure 2 The number 2 indicates the filling position of the coupling material.

[0034] The aforementioned drilling process for monitoring borehole 31 provides a dedicated installation space for the cylindrical sensor 1 to fit snugly against the surrounding rock 3. Multiple placement options in various locations and directions can adapt to the monitoring needs of different parts of the surrounding rock 3: vertical boreholes are used for monitoring the top and bottom plates, horizontal boreholes for monitoring the ribs or sidewalls, and inclined boreholes for specific stress field analysis. Hole cleaning eliminates any debris within the borehole that could negatively impact subsequent coupling. The design of the inner diameter and depth parameters ensures both successful sensor implantation and complete coverage of the core area affected by mining activities, laying a solid foundation for effective stress transmission and accurate monitoring.

[0035] The multi-scenario adaptable borehole layout can cover the monitoring needs of the entire surrounding rock area 3, and the depth design matches the mining impact range to ensure the relevance of monitoring data. Standardized borehole cleaning operations and size adaptation design eliminate the impact of borehole construction defects on sensor coupling effect, ensure the stable transmission of stress in the surrounding rock 3 to the sensing unit, improve the reliability of monitoring data from the construction source, and meet the core requirements of continuous mining stress monitoring.

[0036] In some embodiments, before drilling the monitoring borehole 31, the inner diameter, depth, orientation, and layout points of the monitoring borehole 31 are determined according to a preset monitoring plan. The borehole opening position is marked, and a matching drilling tool is selected to carry out the drilling operation. After the hole cleaning operation is completed, the integrity of the borehole wall and the axial deviation of the monitoring borehole 31 are checked to ensure that there are no problems such as borehole collapse or diameter reduction, and that the axial deviation meets the sensor installation requirements. The actual depth and inner diameter of the monitoring borehole 31 are verified to ensure that the drilling parameters are completely matched with the size of the cylindrical sensor 1 and the monitoring requirements.

[0037] According to one embodiment of this application, before implanting the cylindrical sensor 1 into the monitoring borehole 31, the method further includes: selecting a rigid cylindrical substrate adapted to the monitoring borehole 31 as the sensor substrate; winding a distributed optical fiber 11 along a preset spiral path on the outer surface of the sensor substrate; laying the distributed optical fiber 11 along a preset axial path on the outer surface of the sensor substrate; and fixing the wound distributed optical fiber 11 to the outer surface of the sensor substrate by adhesive bonding to form a wound distributed optical fiber 11 sensor with full-range strain sensing capability.

[0038] The sensor prefabrication process is the core foundation for realizing continuous stress monitoring across the entire area. A rigid cylindrical substrate adapted to the monitoring borehole 31 provides a stable deployment carrier for the distributed optical fibers 11, while also meeting the stress transmission requirements within the borehole. The distributed optical fibers 11, deployed along a helical path, can form a continuous equivalent triaxial strain rosette through spatial angular distribution. The bonding and fixing process eliminates relative slippage between the distributed optical fibers 11 and the substrate, ensuring accurate transmission of strain signals and providing a reliable sensing unit for subsequent data acquisition. The distributed optical fibers 11, deployed along a preset axial path, can be used to capture pure axial tension, compression, and bending deformations.

[0039] The prefabricated spiral-wound distributed optical fiber 11 sensor constructs a continuous equivalent three-dimensional strain rosette network through the spirally arranged distributed optical fibers 11. A single sensor can achieve full-span three-dimensional strain sensing, replacing the traditional discretely arranged multi-point stress gauges. The bonding and fixing process ensures the accuracy of stress transmission and avoids monitoring data distortion caused by the slippage of the distributed optical fibers 11. It realizes a technological leap from single-point measurement to continuous measurement of mining stress at the sensing source, greatly improving monitoring coverage and data reliability.

[0040] In some embodiments, before selecting the sensor substrate, the outer diameter, length, and material parameters of the sensor substrate are determined according to the inner diameter of the monitoring borehole 31 and the monitoring requirements. The elastic modulus of the substrate matches the elastic modulus of the surrounding rock 3 to be monitored. Before winding the distributed optical fiber 11, a preset spiral path is marked on the surface of the sensor substrate, and the pitch and spiral angle of the distributed optical fiber 11 are controlled to ensure that the distributed optical fiber 11 is laid continuously and without bending along the spiral path. After the distributed optical fiber 11 is fixed, the light transmission performance and bonding firmness of the distributed optical fiber 11 are tested to ensure that the sensing unit is undamaged and unloose.

[0041] According to one embodiment of this application, a distributed optical fiber 11 is wound along a preset spiral path on the outer surface of the sensor substrate, including: winding at least two independent distributed optical fibers 11 on the outer surface of the sensor substrate; each distributed optical fiber 11 is continuously wound along the axial direction of the sensor substrate with the same helical angle and pitch, and the winding parameters of each distributed optical fiber 11 are matched with each other to form a continuously distributed equivalent triaxial strain flower array on the surface of the sensor substrate.

[0042] For example, such as Figure 4 The diagram shows the helical path winding of the distributed optical fiber 11. Two independent distributed optical fibers 11 can be wound along a preset helical path on the outer surface of the sensor substrate (i.e., Figure 4 Three distributed optical fibers 11 (i.e., +45° distributed optical fiber 11 and -45° distributed optical fiber 11) are laid out along a preset axial path. Figure 4 Axially distributed optical fibers π / 2, axially distributed optical fibers π, and axially distributed optical fibers 7π / 4 (e.g.) Figure 4 As shown, the two independent distributed optical fibers 11 wound along a preset spiral path have a spiral angle of 45°. The two spirally extending distributed optical fibers and the three axially extending distributed optical fibers are all set on the outer surface of the sensor substrate. The arrangement method can be to open grooves on the surface of the sensor substrate that are adapted to the size of the optical fibers and embed the distributed optical fibers into the grooves for fixation, or to directly paste and fix the distributed optical fibers to the outer surface of the sensor substrate without opening grooves.

[0043] Multiple independent distributed optical fibers 11 form the core carrier for constructing a three-dimensional strain sensing system. Preset helix angles and pitches allow each distributed optical fiber 11 to correspond to a different spatial strain-sensitive direction. Matched winding parameters allow the measuring points of each distributed optical fiber 11 to form a corresponding dense array in the axial and circumferential directions of the sensor substrate, which is equivalent to a continuously distributed triaxial strain flower, providing multiple sets of independent basic data for the calculation of three-dimensional strain and mining stress.

[0044] Multiple independently deployed distributed optical fibers 11 can provide multiple sets of independent strain data, providing sufficient basic data support for three-dimensional strain calculation and improving the accuracy and reliability of stress calculation. The continuous equivalent triaxial strain flower array formed by the matched winding parameters can realize synchronous three-dimensional strain sensing of the entire sensor substrate, breaking through the limitation of traditional distributed optical fibers 11 that can only acquire one-dimensional strain data, and adapting to the core requirement of continuous monitoring of mining-induced stress.

[0045] In some embodiments, before winding the distributed optical fibers 11, the spiral paths corresponding to each distributed optical fiber 11 are marked on the outer surface of the sensor substrate to determine the circumferential starting position of each distributed optical fiber 11, ensuring that each distributed optical fiber 11 is uniformly distributed in the circumferential direction of the sensor substrate. During the winding process, the winding tension of the distributed optical fibers 11 is controlled to ensure that the distributed optical fibers 11 are without bending or twisting throughout the entire process, and smoothly conform to the outer surface of the sensor substrate along the spiral path. Both ends of each distributed optical fiber 11 extend to the end of the sensor substrate, reserving sufficient length of distributed optical fiber 11 for subsequent demodulation equipment connection.

[0046] According to one embodiment of this application, the end of the distributed optical fiber 11 is connected to a distributed optical fiber demodulation system to collect continuous strain data of the entire domain of the cylindrical sensor 1 during the mining process. This includes setting the spatial sampling interval, acquisition frequency and measurement range parameters of the distributed optical fiber demodulation system. During the entire mining process, the demodulation system synchronously collects the strain data of all measuring points on each distributed optical fiber 11 to obtain a continuous strain dataset covering the entire sensor domain.

[0047] The distributed fiber optic demodulation system is the core device for converting optical signals from distributed optical fibers 11 into strain data. The parameter setting process can be matched to the dynamic characteristics of sampling activities, ensuring that the acquisition accuracy adapts to monitoring requirements. Synchronous acquisition guarantees that the measurement points on each distributed optical fiber 11 are accurately aligned in the time dimension, providing a continuous strain dataset covering the entire sensor domain. This provides a time-synchronized and spatially continuous fundamental data source for subsequent three-dimensional strain calculation and sampling stress conversion.

[0048] Customizable acquisition parameters can adapt to the monitoring needs of different mining scenarios. Synchronous acquisition ensures the time consistency of multiple sets of distributed fiber optic data, avoiding stress calculation errors caused by data timing deviations. The continuous strain dataset covering the entire sensor domain can completely capture the dynamic evolution of surrounding rock stress during mining, solving the problems of discontinuous and asynchronous data in traditional point monitoring, and providing a reliable data foundation for accurate calculation of continuous mining stress.

[0049] In some embodiments, before setting the acquisition parameters, the first and last ends of each distributed optical fiber 11 can be connected to the corresponding acquisition channel of the distributed optical fiber demodulation system to complete the optical path connection and optical transmission performance verification. Before officially starting the acquisition, the initial strain data of the distributed optical fiber 11 before the acquisition activity begins is acquired as the benchmark value for subsequent acquisition stress calculation. During the data acquisition process, the integrity of the data in each channel is verified in real time, and invalid data with abnormal jumps are removed to ensure the validity of the strain dataset.

[0050] According to one embodiment of this application, before calculating the continuous mining stress data of the entire monitoring borehole 31 based on the collected continuous strain data and the elastic mechanical parameters of the rock mass, the method further includes: performing a modulus operation on the helix angle parameters of all measuring points, and uniformly mapping the circumferential angles of all measuring points to a numerical range of 0 to 2π.

[0051] The circumferential angle model mapping process is a core preprocessing step before the strain data of the spirally wound distributed optical fiber 11 is calculated. It addresses the issues of circumferential angle reversal and numerical jumps that occur at measuring points in different turns after multiple turns of continuous winding of the distributed optical fiber 11. The model mapping operation can eliminate coordinate conflicts between measuring points in different turns, unify and standardize the circumferential positions of all measuring points to the same numerical range, and allow the measuring points to be arranged in an orderly manner according to the geometric characteristics of the cylindrical surface, providing standardized spatial position parameters for subsequent mining stress calculation.

[0052] The circumferential angle mapping process resolves the issues of circumferential angle reversal and coordinate conflicts caused by the multi-turn spiral winding of distributed optical fibers. This standardizes and unifies the spatial position parameters of all measuring points, preventing spatial misalignment due to angle value jumps. The unified circumferential angle parameters ensure accurate spatial coordinate matching for subsequent three-dimensional strain calculations, reduce stress calculation errors caused by inconsistent position parameters, and improve the accuracy and reliability of continuously sampled stress data.

[0053] In some embodiments, before performing the modulus calculation, the helix angle parameters of each measuring point are matched with the strain data and axial position parameters of the corresponding measuring points to establish a one-to-one correspondence between the parameters of a single measuring point, ensuring that the parameters are bound to the strain data after the calculation. After the modulus calculation is completed, the circumferential angle values ​​of all measuring points are verified to ensure that the circumferential position parameters of all measuring points fall within the value range of 0 to 2π. The uniformly mapped circumferential angle parameters are then associated with the axial position parameters of the corresponding measuring points to form a complete set of spatial position parameters for the measuring points.

[0054] According to one embodiment of this application, after performing a modulo operation on the helix angle parameters of all measuring points to uniformly map the circumferential angles of all measuring points to a numerical range of 0 to 2π, the method further includes: converting the uniformly mapped circumferential angles into the equivalent transverse arc length of the corresponding cylindrical surface based on the actual radius of the sensor substrate; establishing a planar unfolded coordinate system that matches the geometric features of the sensor cylindrical surface with the equivalent transverse arc length as the transverse coordinate and the axial position of the measuring point as the longitudinal coordinate; and completing the coordinate transformation of all measuring points to obtain the unique planar unfolded coordinates corresponding to each measuring point.

[0055] By establishing a continuous coordinate mapping system from the spirally wound distributed optical fiber 11 to the cylindrical surface and then to the two-dimensional plane, the spatial regularity problem of spiral measurement point data is solved, providing a unified coordinate reference for the calculation of continuous stress across the entire domain.

[0056] Figure 5 The coordinate system of the cylindrical sensor 1 after planar unfolding is shown.

[0057] The actual radius of the sensor substrate provides a calculation benchmark for the conversion of circumferential angle to arc length. The converted equivalent lateral arc length corresponds to the circumferential physical position of the cylindrical surface. Combined with the plane unfolded coordinate system constructed by the axial position of the measuring point, the three-dimensional cylindrical surface measuring point can be mapped to a unique coordinate point in a two-dimensional plane, providing a unified benchmark for subsequent data processing.

[0058] The standardized circumferential angle provides a unified input benchmark for coordinate transformation, avoiding coordinate misalignment caused by angle reversal. The planar unfolded coordinate system achieves distortion-free mapping from 3D cylindrical surface measurement points to a 2D plane, accurately matching multiple sets of distributed fiber optic strain data at the same location, improving the accuracy of 3D strain calculation, and providing a unified coordinate benchmark for subsequent stress visualization.

[0059] In some embodiments, before converting the equivalent transverse arc length, the circumferential angle parameters of all measuring points after unified mapping are verified to ensure the compliance of the input data. After the coordinate transformation is completed, the planar unfolded coordinates of each measuring point are bound to the corresponding strain data and circumferential angle parameters one by one. After the transformation of all measuring points is completed, the uniqueness of the planar unfolded coordinates is verified, and duplicate and invalid measuring point data are eliminated.

[0060] According to one embodiment of this application, based on the collected continuous strain data and combined with the elastic mechanical parameters of the rock mass, the continuous mining stress data of the entire monitoring borehole 31 is calculated, including: matching multiple sets of strain data corresponding to each measuring point based on the planar unfolded coordinates of each measuring point, and solving for the three-dimensional strain tensor of each measuring point using the least squares method; constructing an elastic mechanical three-dimensional stress-strain constitutive relationship matrix by combining the elastic modulus and Poisson's ratio parameters of the surrounding rock 3 to be monitored; and calculating the three-dimensional mining stress value of each measuring point based on the elastic mechanical three-dimensional stress-strain constitutive relationship matrix. The calculated three-dimensional mining stress value of each measuring point may include the magnitude and direction of the three principal stresses.

[0061] This process is the core calculation step for converting strain data from distributed optical fibers 11 into mining-induced stress. The planar unfolded coordinates provide a precise matching benchmark for strain data from multiple independent distributed optical fibers 11 at the same spatial location. The least squares method can obtain a reliable three-dimensional strain tensor by solving multiple sets of redundant strain data. The constitutive relation matrix constructed from the rock mass elastic parameters establishes a bridge between strain and stress, ultimately realizing the three-dimensional mining-induced stress calculation for each measuring point, providing core data for continuous stress field characterization.

[0062] Matching multiple sets of strain data based on planar unfolded coordinates ensures accurate correspondence of multi-source data at the same spatial location, avoiding calculation errors caused by misalignment of measurement points. The least squares method improves the accuracy of the three-dimensional strain tensor calculation through multiple sets of redundant data, and the constitutive matrix based on actual rock mass parameters enables reliable strain-to-stress conversion. This process allows for continuous three-dimensional mining stress calculation across the entire monitoring borehole 31, overcoming the coverage limitations of traditional point-based monitoring and providing continuous and accurate stress data support for mining safety assessment.

[0063] In some embodiments, before matching multiple sets of strain data for corresponding measuring points, abnormal jump values ​​in the strain data are removed, and valid strain data are selected for subsequent calculations. When calculating the three-dimensional mining-induced stress value, the obtained three-dimensional strain tensor is substituted into the three-dimensional stress-strain constitutive relation matrix to complete the stress value calculation. After the calculation is completed, the magnitude and direction of the three principal stresses contained in the three-dimensional mining-induced stress value of each measuring point are output, forming a complete stress calculation result.

[0064] According to one embodiment of this application, after calculating the three-dimensional mining stress value of each measuring point, the method further includes: associating the calculated three-dimensional mining stress value of each measuring point with the corresponding planar unfolded coordinates and spatial position coordinates to generate a continuous mining stress data set for the entire area of ​​the monitoring borehole 31; based on the continuous mining stress data set, generating a planar unfolded continuous mining stress distribution map of the monitoring borehole 31 with the planar unfolded coordinates as the reference, and generating a three-dimensional cylindrical surface mining stress cloud map of the monitoring borehole 31 with the spatial position coordinates as the reference; the distribution map and cloud map are used for stability analysis and safety assessment of the mining project.

[0065] The one-to-one correlation between three-dimensional stress values ​​and planar coordinates and spatial coordinates allows each set of stress data to accurately correspond to the actual physical location of the monitoring area, forming a complete and continuous stress dataset. The two types of visualization results generated based on the dual-coordinate system can transform abstract numerical data into an intuitive presentation of stress distribution, providing a directly applicable data carrier for engineering analysis.

[0066] The dual-coordinate correlated continuous mining stress dataset achieves precise binding between stress values ​​and monitoring spatial locations, solving the problem of poor correspondence between traditional point-based monitoring data and actual locations. Two types of visualization results generated from the dataset can intuitively present the continuous distribution characteristics of mining stress across the entire domain, accurately capturing localized stress concentration areas. This provides accurate and continuous support for stability analysis and safety assessment of mining projects, enhancing the engineering application value of monitoring results.

[0067] In some embodiments, before associating coordinates with stress values, the correspondence between the spatial coordinates of each measuring point and the actual engineering coordinates of the monitoring borehole 31 is clarified to ensure accurate matching between stress data and actual on-site locations. After generating the continuous mining stress data set, the integrity of the data set is verified, and invalid data groups with duplicate coordinates or abnormal stress values ​​are removed. When generating distribution maps and cloud maps, the location and values ​​of stress concentration areas are marked to provide intuitive key points for engineering stability analysis.

[0068] According to one embodiment of this application, the coupling material 2 is cement slurry or resin.

[0069] The coupling material 2 fills the annular gap between the sensor and the borehole wall 31, serving as the core medium for stress transmission between the surrounding rock 3 and the sensor. Both cement grout and resin possess excellent rigidity and adhesion properties, and after curing, they eliminate interfacial gaps, allowing the surrounding rock 3, coupling material 2, and sensor to form a continuous stress transmission path, ensuring the reliability of the monitoring data.

[0070] In some embodiments, the cement slurry is prepared using high-strength silicate cement, and the resin is selected from epoxy resin used for engineering anchoring. The elastic modulus of the cured material matches the elastic modulus of the sensor matrix and the surrounding rock 3 to be monitored. The coupling material 2 has good flow properties and can fully fill the annular gap between the sensor and the borehole wall without leaving any voids. After curing, the coupling material 2 has long-term structural stability, adapting to the monitoring needs of the entire mining project cycle.

[0071] The following is an example illustrating a calculation method: Real-time acquisition of continuous strain data during the mining process. Utilizing the triaxial strain rose sensing characteristics formed by the distributed 11-fiber spiral arrangement, three sets of strain parameters are acquired synchronously at each measuring point: ① Helix angle θ, which is the angle between the helix and the axis (the helix angle is the same for multiple measuring points). The parameter s obtained after subsequent calculation can characterize the circumferential position of the measuring point; ② Height z, which characterizes the axial position of the measuring point, i.e., the Z-axis position; ③ Strain.

[0072] First, to address the issue of circumferential angle reversal caused by multiple turns of the spiral path, angle unification processing is performed to eliminate coordinate conflicts in the multi-turn data: The circumferential angles of all measuring points are uniformly mapped to the 0-2π interval, so that the circumferential position coordinates of measuring points in different cycles are consistent, and the data can be arranged in an orderly manner according to the geometric features of the cylindrical surface.

[0073] Then, a continuous coordinate mapping system is constructed. Based on the actual radius R of the sensor, the unified circumferential angle is converted into an equivalent lateral arc length, and a planar unfolded coordinate system that perfectly matches the geometric features of the cylindrical surface is established to realize the mapping of continuous data of the spiral path to the entire cylindrical surface: The unfolded plane coordinates (s, z) of each continuous measurement point are obtained, where s∈[0, 2πR] corresponds to the circumferential domain of the cylindrical surface, and z∈[z_min, z_max] corresponds to the axial (i.e., Z-axis) domain of the cylindrical surface, ensuring that each set of coordinates (s, z) uniquely corresponds to a position point on the surface of the cylindrical sensor.

[0074] Then, the planar coordinates (s, z) are correlated one-to-one with the mining stress σ of strain transformation, and the continuous mining stress data set {(s, z, σ)} of the entire borehole is directly output. At the same time, based on the coordinate mapping relationship, a continuous mining stress distribution map of the planar coordinates and a three-dimensional mining stress visualization map of the borehole are generated, which intuitively presents the continuous distribution state of mining stress and can be directly used for engineering analysis and safety assessment.

[0075] The specific methods for converting strain into stress are as follows: Strain data based on 5 distributed optical fibers 11 Establish the following relationship: Where i = 1~5 (corresponding to 5 distributed optical fibers 11), and A is a coefficient matrix consisting of the helix angle and the direction of the distributed optical fibers 11. Solved using the least squares method: By combining material parameters such as the rock mass's elastic modulus and Poisson's ratio, and based on the three-dimensional stress-strain constitutive relationship of elasticity, the three-dimensional strain data is used to inversely derive three-dimensional in-situ stress values ​​(including the magnitude and direction of the three principal stresses), achieving a three-dimensional stress measurement function equivalent to that of hollow inclusions. The specific formula is as follows: in, Let D be the stress at which the stress is generated, and let D be the elastic matrix, which is determined by the elastic modulus E and Poisson's ratio ν.

[0076] The continuous sampling stress measurement method based on wound distributed optical fiber provided in this application has the following advantages: 1. Forming a dense, equivalent triaxial strain rosette array across the entire domain: By spirally winding distributed optical fibers 11 around the surface of a cylindrical sensor, a continuously distributed equivalent triaxial strain rosette array is constructed, enabling synchronous sensing of three-dimensional strain across the entire domain. The sensing dimensions are comprehensively superior to traditional single-point measurement methods.

[0077] 2. Replacement for traditional discretely deployed hollow inclusion stress gauges: There is no need to deploy discrete hollow inclusion stress gauges. The entire range of dynamic stress measurement can be completed by a cylindrical sensor with a spirally wound distributed optical fiber 11, which reduces the cost of monitoring deployment and reduces the problem of monitoring data interruption caused by single-point equipment failure.

[0078] 3. Achieving a technological breakthrough from single-point measurement to continuous measurement of mining stress: Overcoming the limitations of traditional point measurement of mining stress, achieving continuous monitoring of mining stress across the entire borehole, and accurately capturing the dynamic evolution and local concentration characteristics of surrounding rock stress during mining.

[0079] 4. Direct data calculation and high real-time monitoring: The strain data collected by the equivalent triaxial strain rosette array is directly calculated to solve the mining-induced stress, which simplifies the data processing flow, has a fast response speed, and is suitable for the real-time monitoring needs of dynamic changes in mining-induced stress.

[0080] 5. Good environmental adaptability and versatility: The distributed optical fiber 11 has the characteristics of anti-electromagnetic interference, moisture resistance and pressure resistance, and can be adapted to harsh mining environments such as deep mining and tunnel excavation. It is also suitable for cylindrical sensors of various specifications and can be widely used in various rock and soil mining engineering monitoring scenarios.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate this application and are not intended to limit this application. Although this application has been described in detail with reference to the embodiments, those skilled in the art should understand that various combinations, modifications, or equivalent substitutions of the technical solutions of this application do not depart from the spirit and scope of the technical solutions of this application and should be covered within the scope of the claims of this application.

Claims

1. A method for continuous mining stress measurement based on wound distributed optical fiber, characterized in that, Includes the following steps: Drill cylindrical monitoring boreholes in the monitoring area affected by mining activities; A cylindrical sensor is implanted into the monitoring borehole. Distributed optical fibers wound along a preset spiral path are fixed on the surface of the cylindrical sensor. The distributed optical fibers wound along the preset spiral path form a continuously distributed equivalent triaxial strain rose array on the surface of the cylindrical sensor. Coupling material is filled between the cylindrical sensor and the borehole wall to form a rigid coupling body between the cylindrical sensor and the surrounding rock of the monitoring borehole. The end of the distributed optical fiber is connected to the distributed optical fiber demodulation system to collect continuous strain data of the entire area of ​​the cylindrical sensor during the sampling process. Based on the collected continuous strain data and combined with the elastic mechanical parameters of the rock mass, the continuous mining stress data of the entire monitoring borehole area is calculated.

2. The method for continuous mining stress measurement based on wound distributed optical fiber according to claim 1, characterized in that, Drilling cylindrical monitoring boreholes in the monitoring area affected by mining activities includes: According to the preset monitoring plan, monitoring boreholes are drilled in the top, bottom, side or target monitoring body of the surrounding rock in the area to be monitored, along the vertical, horizontal or inclined direction. After the monitoring borehole is completed, high-pressure air or clean water is used to remove rock powder and loose debris from the borehole. The inner diameter of the monitoring borehole is 5mm to 20mm larger than the outer diameter of the sensor, and the depth of the monitoring borehole covers the mining impact range of the area to be monitored.

3. The method for continuous sampling stress measurement based on wound distributed optical fiber according to claim 1, characterized in that, Prior to implanting the cylindrical sensor into the monitoring borehole, the method further includes: A rigid cylindrical substrate adapted to the monitoring borehole was selected as the sensor substrate; Distributed optical fibers are wound along a preset spiral path on the outer surface of the sensor substrate; Distributed optical fibers are laid along a preset axial path on the outer surface of the sensor substrate; By using an adhesive bonding method, the wound optical fiber is fixed to the outer surface of the sensor substrate, forming a wound optical fiber sensor with full-range strain sensing capability.

4. The method for continuous mining stress measurement based on wound distributed optical fiber according to claim 3, characterized in that, The method of winding distributed optical fibers along a preset helical path on the outer surface of the sensor substrate includes: At least two independent distributed optical fibers are wound around the outer surface of the sensor substrate; Each distributed optical fiber is continuously wound along the axial direction of the sensor substrate with the same helix angle and pitch. The winding parameters of each distributed optical fiber are matched to form a continuously distributed equivalent triaxial strain flower array on the surface of the sensor substrate.

5. The method for continuous mining stress measurement based on wound distributed optical fiber according to claim 3, characterized in that, The number of distributed optical fibers wound along the preset spiral path is 2, and the number of distributed optical fibers laid along the preset axial path is 3.

6. The method for continuous mining stress measurement based on wound distributed optical fiber according to claim 3, characterized in that, The step of connecting the end of the distributed optical fiber to the distributed optical fiber demodulation system to collect continuous strain data of the entire range of the cylindrical sensor during the sampling process includes: Set the spatial sampling interval, acquisition frequency, and measurement range parameters of the distributed optical fiber demodulation system; Throughout the entire mining process, strain data from all measuring points on each distributed optical fiber are simultaneously acquired through a demodulation system, resulting in a continuous strain dataset covering the entire sensor domain.

7. The method for continuous mining stress measurement based on wound distributed optical fiber according to claim 6, characterized in that, Before calculating the continuous mining stress data for the entire monitoring borehole area based on the collected continuous strain data and the elastic mechanical parameters of the rock mass, the following steps are also included: Perform a modulo operation on the helix angle parameters of all measuring points to uniformly map the circumferential angles of all measuring points to a numerical range of 0 to 2π.

8. The method for continuous mining stress measurement based on wound distributed optical fiber according to claim 7, characterized in that, After performing a modulo operation on the helix angle parameters of all measuring points to uniformly map the circumferential angles of all measuring points to a numerical range of 0 to 2π, the following steps are also included: Based on the actual radius of the sensor substrate, the uniformly mapped circumferential angle is converted into the equivalent lateral arc length of the corresponding cylindrical surface; A planar unfolded coordinate system matching the geometric features of the sensor's cylindrical surface is established, with the equivalent transverse arc length as the transverse coordinate and the axial position of the measuring point as the longitudinal coordinate. Complete the coordinate transformation of all measuring points to obtain the unique planar unfolded coordinates corresponding to each measuring point.

9. The method for continuous mining stress measurement based on wound distributed optical fiber according to claim 8, characterized in that, Based on the collected continuous strain data and combined with the elastic mechanical parameters of the rock mass, the continuous mining stress data of the entire monitoring borehole area is calculated, including: Based on the planar unfolded coordinates of each measuring point, multiple sets of strain data corresponding to the measuring points are matched, and the three-dimensional strain tensor of each measuring point is obtained by solving the least squares method. By combining the elastic modulus and Poisson's ratio parameters of the surrounding rock to be monitored, a three-dimensional stress-strain constitutive relationship matrix of elasticity is constructed. Based on the three-dimensional stress-strain constitutive relation matrix of elasticity, the three-dimensional mining stress value of each measuring point is calculated.

10. The method for continuous mining stress measurement based on wound distributed optical fiber according to claim 9, characterized in that, After calculating the three-dimensional mining stress values ​​at each measuring point, the method further includes: The three-dimensional mining stress values ​​obtained from each measuring point are correlated with the plane unfolded coordinates and spatial position coordinates of the corresponding measuring points to generate a continuous mining stress data set for monitoring the entire borehole area. Based on the continuous mining stress data set, a planar unfolded continuous mining stress distribution map of the monitoring borehole is generated with the planar unfolded coordinates as the reference, and a three-dimensional cylindrical surface mining stress cloud map of the monitoring borehole is generated with the spatial position coordinates as the reference; the distribution map and cloud map are used for stability analysis and safety assessment of mining projects.

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