A surrounding rock stress field inversion method

Abstract

The present application relates to a kind of surrounding rock stress field inversion method, specific steps include: the construction of roadway fiber grating sensor network, the collection and preprocessing of surrounding rock strain data, the construction of surrounding rock zoning constitutive model, anchor support volume force model construction.The present application is characterized in that, the present application constructs high-density fixed-point distribution fiber grating three-dimensional monitoring network in roadway surrounding rock, sensor is laid along the axial direction of borehole with set interval, covers broken zone, plastic softening zone, elastic zone whole area, overcomes the defect of traditional micro-strain sensor, stress meter "point instead of surface", can obtain continuous strain data in the range of roadway meter-level displacement change, truly reflects the overall distribution characteristics and evolution law of roadway surrounding rock three-dimensional stress field, realizes the technical breakthrough from "discrete point monitoring" to "full stress field continuous monitoring".

Description

Technical Field

[0001] This invention belongs to the field of coal mine tunnel engineering technology, specifically relating to a method for inverting the stress field of surrounding rock. Background Technology

[0002] Throughout the entire process of tunneling and mining, underground coal mine roadways are constantly subjected to the superposition of original ground stress (static load) and mining dynamic pressure. This complex loading environment leads to progressive, nonlinear failure of the surrounding rock mass, forming a three-zone system: a fractured zone, a plastic softening zone, and an elastic zone (i.e., the "surrounding rock three zones"), which develop in concentric circles from the inside out, centered on the roadway outline. In the fractured zone, the rock mass integrity is severely compromised, and its strength decreases sharply; in the plastic softening zone, the rock mass undergoes plastic deformation and its mechanical parameters deteriorate; while in the elastic zone, the rock mass only undergoes elastic deformation, retaining its original mechanical properties. The extent, stress distribution, and evolution of the surrounding rock three zones directly determine the stability of the roadway and are the core basis for roadway support design, disaster early warning, and safety management.

[0003] In coal mine safety production, the importance of accurate and dynamic monitoring of the stress field of roadway surrounding rock is becoming increasingly prominent. It not only allows for real-time monitoring of the evolution of surrounding rock damage but also provides scientific feedback for optimizing and adjusting roadway surrounding rock control technologies, thereby effectively preventing safety accidents such as roof falls and spalling. However, currently, there are still many technical bottlenecks in the monitoring and inversion of the stress field in the three zones of roadway surrounding rock under mining influences (substituting static load and dynamic pressure). Existing technologies are insufficient to meet the high-precision, full-range monitoring requirements of actual engineering projects.

[0004] In the field of dynamic monitoring of surrounding rock stress in roadways, traditional technologies mostly employ discrete sensors such as micro-strain sensors and stress gauges. Their core shortcomings are: first, limited monitoring range, only able to acquire local stress data at a few discrete points around the roadway, unable to achieve full coverage monitoring of the three zones of the surrounding rock (fractured zone, plastic softening zone, and elastic zone), making it difficult to capture the spatial distribution characteristics and overall evolution of the stress field; second, insufficient coupling, lacking in-depth coupling analysis of the interaction between the mechanical state of the surrounding rock (elastic, plastic softening, fractured) and the support structure (anchor bolts, anchor cables, etc.), ignoring the differences in stress state of the anchor bearing body in different regions of the surrounding rock—the anchor bearing body exhibits a loose bearing state in the fractured zone, a plastic deformation bearing state in the plastic softening zone, and an elastic stability state in the elastic zone. First, the difference in bearing capacity directly affects the stress transmission law, but traditional monitoring methods do not take this into account, resulting in a significant decrease in the accuracy of stress inversion. Second, the reliability is poor. Traditional sensor equipment is complex to arrange, and the underground environment has extreme conditions such as high humidity, high dust, strong electromagnetic interference, and severe deformation of the surrounding rock, which can easily lead to sensor failure and data distortion. The anti-interference ability and long-term stability are difficult to meet the engineering requirements. Third, the data integrity is insufficient. It is impossible to obtain continuous, full-section stress-strain information of the surrounding rock in the three zones after mining disturbance. It is difficult to truly reflect the actual bearing capacity, damage evolution mechanism, and complex three-dimensional initial stress field of the surrounding rock in the entire roadway. It cannot provide comprehensive and reliable technical support for roadway support optimization and disaster early warning.

[0005] Patent CN121520024A discloses a stress monitoring and disaster early warning system and method for mine working faces. By constructing a stress field analysis system that includes uncertainty assessment, and combining fiber optic sensor network monitoring data with microseismic monitoring data, it analyzes the uncertainty transmission and amplification effects of the inversion process and calculates the confidence interval of stress values. This solves the problem of insufficient reliability of disaster early warning due to model uncertainty in existing stress field inversion methods, thereby achieving accurate early warning of dynamic disasters at mine working faces. However, it still has shortcomings: it does not construct zonal constitutive models for the differentiated mechanical properties of the fractured zone, plastic softening zone, and elastic zone of the surrounding rock in the roadway; it does not analyze the stress transmission laws of different anchoring support conditions such as full anchoring and end anchoring; it cannot achieve accurate zonal stress inversion of the three zones of the surrounding rock in the roadway; and the sensor network deployment is not adapted to the roof and sidewall structure of the roadway to form a three-dimensional monitoring system, making it difficult to cover the entire three zones of the surrounding rock in the roadway.

[0006] Patent CN117605536A discloses a method for inverting and analyzing the stress field of deep coal mine working faces. By deploying discrete stress measurement points and combining active / passive seismic CT complementary technology, the static three-dimensional stress field is calibrated using discrete point stress test results as constraints. The dynamic three-dimensional stress field is then corrected by incorporating microseismic signals from the working face advancement process. This solves the problems of traditional point measurement methods failing to comprehensively reflect the three-dimensional stress state of deep coal mine working faces and having low confidence levels in the inversion results. This achieves accurate inversion and real-time monitoring of the stress field in deep, high-stress working faces. However, it still relies on discrete stress measurement point data, cannot achieve continuous strain and stress perception across the entire surrounding rock area, does not consider the zonal mechanical characteristics of the three zones of the roadway surrounding rock, and does not conduct in-depth coupling analysis of the interaction between anchor support and surrounding rock. This makes it difficult to accurately match the stress evolution law of progressive failure of the roadway surrounding rock, resulting in deviations between the inversion results and the actual stress state of the roadway.

[0007] In addition, some existing stress inversion methods either rely solely on sensor measurement data and lack integration with the constitutive model of surrounding rock mechanics, making it impossible to infer the true distribution of stress inside the surrounding rock from the measurement data; or they rely solely on theoretical calculations based on mechanical analytical models without combining actual monitoring data for calibration, resulting in a large deviation between the theoretical calculation results and the actual stress state downhole, making it difficult to apply to engineering practice.

[0008] In summary, there is an urgent need in this field for a scientific and reasonable stress field inversion method to achieve accurate and dynamic perception and assessment of the stress state of the surrounding rock throughout the entire process and range, from the fractured zone to the plastic softening zone and then to the elastic zone. This would fill the gap in existing technologies for full-domain, continuous, and high-precision stress inversion, and provide reliable technical support for the safe and stable control of underground roadways in coal mines. Summary of the Invention

[0009] The present invention aims to solve the problem that existing methods for inverting the stress field of roadway surrounding rock are unable to accurately reflect the true stress state of the surrounding rock.

[0010] The present invention solves the above-mentioned technical problems through the following technical means: A method for inverting the stress field of surrounding rock includes the following steps: constructing a fiber optic grating sensor network in the roadway, acquiring and preprocessing surrounding rock strain data, constructing a constitutive model of surrounding rock zoning, and constructing a volumetric force model of anchor bolt support; acquiring distributed strain data of surrounding rock through a high-density fixed-point distributed fiber optic grating sensor network, and constructing a coupled inversion model by combining the constitutive model of surrounding rock zoning and the volumetric force model of anchor bolt support, and inverting the continuous stress field of the fractured zone, plastic softening zone, and elastic zone of the surrounding rock in the roadway.

[0011] This invention, by employing fiber optic grating sensors, can acquire continuous strain data of the surrounding rock in tunnels, overcoming the limitations of traditional point-based measurements that "represent the surface" and truly reflecting the three-dimensional stress field distribution characteristics of the fractured zone, plastic softening zone, and elastic zone. It can monitor changes in the stress state of the surrounding rock in real time and, combined with an inversion model, achieve dynamic assessment of tunnel stability, providing a scientific basis for early warning of underground engineering disasters.

[0012] Preferably, the construction of the fiber optic grating sensor network includes the following steps: selecting tunnel measuring points and drilling holes vertically to the tunnel walls; selecting strain sensing optical cables, fixing them to the installation drill rod and inserting them into the drill holes, injecting cement mortar into the drill holes and compacting it, and completing the sensor deployment after the cement has solidified; setting up monitoring sections along the tunnel axis, drilling holes in the top plate and both sides of the section to deploy sensors, and connecting all the sensors in the drill holes in series along the axis at a preset interval to form a monitoring chain, thus forming a three-dimensional monitoring network covering the three zones of the surrounding rock.

[0013] The three-dimensional deployment rules of the fiber optic grating sensor network are precisely defined. Through the deployment method of "axial monitoring section + top and side drilling + preset spacing monitoring chain", full coverage monitoring of the surrounding rock fracture zone, plastic softening zone and elastic zone is achieved. This solves the problems of "regional missed detection and data dispersion" in traditional monitoring and ensures the spatial continuity of strain data.

[0014] Preferably, the specific process of installing the fiber optic grating sensor network in the well includes: transporting and verifying construction materials; accurately marking and verifying the drilling points according to the design; fusing the sensing optical cable and the conductor optical cable using a hot melt machine, inserting the splice into a stainless steel protective pipe, and wedge-grooving the PVC installation pipe; placing the protected splice and optical cable into the PVC installation pipe groove and fixing them, pushing them section by section to the designed drilling depth, and injecting cement grout to solidify the entire section; completing the splicing and protection of the communication optical cable and strain optical cable at the drilling site, laying the communication optical cable along the roadway wall and connecting it to the underground industrial ring network switch; matching the IP addresses of the ground monitoring center and the underground dense distributed explosion-proof fiber optic demodulator to complete the network connection debugging.

[0015] The standardized operational procedures for the underground installation of sensor networks have been refined, with precise limits set for key steps such as material transportation, borehole marking, fiber optic cable splicing and protection, grouting consolidation, and network connectivity. Each step is designed around "improving the coupling between the fiber optic cable and the surrounding rock and ensuring the stability of signal transmission," adapting to the complex construction environment of underground coal mines and ensuring the standardization and reliability of the monitoring system installation.

[0016] Preferably, the acquisition and preprocessing of the surrounding rock strain data includes: acquiring the center wavelength offset of the fiber optic grating sensor in real time using a densely distributed explosion-proof fiber optic demodulator, converting it into radial strain distribution data of the surrounding rock based on the fiber optic sensing principle; performing temperature compensation, outlier removal and data smoothing on the strain data; and automatically identifying the working condition of the anchor bolt support based on the strain distribution characteristics.

[0017] A standardized processing flow for strain data acquisition, conversion, preprocessing, and condition identification was established. Preprocessing techniques such as temperature compensation and outlier removal were used to eliminate monitoring errors. At the same time, automatic identification of anchor support conditions was achieved, laying a data foundation for accurate subsequent input into the corresponding stress analysis formula and improving the automation and accuracy of stress inversion.

[0018] Preferably, the working conditions of the anchor bolt support include: when fully anchored, the anchor bolt body penetrates the fractured zone and extends into the plastic softening zone; when fully anchored, the anchor bolt body is in the fractured zone; when end-anchored, the anchoring section is in the plastic softening zone; when end-anchored, the anchoring section is in both the plastic softening zone and the fractured zone; and when end-anchored, the anchoring section is in the fractured zone.

[0019] The study comprehensively sorts out and clarifies five typical working conditions of anchor bolt support, accurately covering the actual support scenarios of full anchor and end anchor in underground coal mines. Moreover, the working condition classification matches the depth distribution of the three zones of surrounding rock, providing a clear basis for selecting the corresponding stress analysis formula under different support conditions, and solving the problem of "disconnect between support working conditions and stress calculation" in traditional methods.

[0020] Preferably, the construction of the surrounding rock zonal constitutive model follows the following strength criterion: the boundary between the elastic zone and the plastic softening zone satisfies the Mohr-Coulomb criterion, i.e. The strength of the plastic softening zone decreases with the softening modulus, as shown in the formula: The fractured zone meets the residual strength criterion of the rock mass. In the formula This represents the tangential stress at the boundary. Indicates the radial stress at the boundary. This represents the tangential stress in the fracture zone. Indicates the radial stress in the fractured zone. Peak strength of the rock mass Indicates the residual strength of the rock mass. For the strength of the rock mass in the plastic softening zone, , The friction angle within the rock mass. To soften the modulus, , , These represent the tangential strains in the elastic region, the plastic softening region, and the fracture region, respectively. , These represent the peak zone of the rock mass and the residual cohesion, respectively.

[0021] A zone-differentiated constitutive model was constructed based on the characteristics of the three zones of the surrounding rock. The boundary between the elastic zone and the plastic softening zone follows the Mohr-Coulomb criterion, the plastic softening zone considers strength decay, and the fractured zone adopts the residual strength criterion. This model is consistent with the mechanical characteristics of the progressive failure of the surrounding rock in coal mine roadways, making the constitutive model more in line with engineering practice and improving the theoretical scientificity of stress inversion.

[0022] Preferably, the anchor bolt support volume force model is constructed by equating the anchor bolt preload force to the radial volume force acting on the surrounding rock, and the calculation formula is as follows: ,in For anchor bolt preload, The radius of the alleyway, , The spacing between anchor bolts. It is a radial volume force. The length of the anchor bolt. This represents the radial distance from any point in the surrounding rock to the center of the tunnel.

[0023] By equating the preload of the anchor bolt to the radial volume force of the surrounding rock and providing a clear calculation formula, the anchor bolt support force is transformed from a "point load" to a "distributed volume force". The support effect is successfully introduced into the stress balance equation of the surrounding rock, solving the problem of coupling calculation between the support structure and the stress field of the surrounding rock, and making the inversion results more consistent with the actual stress state of the surrounding rock under anchor support.

[0024] Preferably, it also includes stress field inversion calculation and visualization. The specific process of stress field inversion is as follows: input the roadway geometric parameters, surrounding rock mechanical parameters, and support parameters into the ground server, and configure the monitoring parameters; use the pre-processed strain data as boundary conditions and input parameters, substitute them into the stress analysis formulas corresponding to various anchor bolt support conditions, and iteratively solve to obtain the continuous distribution of radial stress and tangential stress in the fractured zone, plastic softening zone, and elastic zone of the surrounding rock, and complete the coupled analysis of static load and mining dynamic pressure superposition.

[0025] The parameter input and solution logic of stress field inversion calculation are clearly defined. By using the method of "multi-parameter configuration + preprocessed strain data as boundary conditions + iterative solution", coupled analysis under static load and mining dynamic pressure superposition conditions is realized. Furthermore, the radial / tangential continuous stress in the three zones is specifically solved, which breaks through the limitation of traditional methods that "can only calculate single-point stress and cannot consider dynamic pressure superposition".

[0026] Preferably, the stress analysis formula for each anchor support condition includes the radial stress calculation formula and the tangential stress calculation formula for the corresponding surrounding rock zone, specifically including: When the working condition is full anchoring, the anchor rod body penetrates the fractured zone and extends into the plastic softening zone. The radial stress in the plastic softening zone within the anchoring range is:

[0027] The tangential stress in the plastic softening zone within the anchorage range is: ; When the working condition is full anchoring, the entire length of the anchor rod is located in the fractured zone, and the radial stress of the surrounding rock in the fractured zone outside the anchoring range is: , The tangential stress of the surrounding rock in the fractured zone outside the anchorage range is: ; When the working condition is end anchor support and the anchorage section is located in the plastic softening zone, the radial stress in the plastic softening zone within the anchorage section is: , The tangential stress in the plastic softening zone within the anchorage section is: ; When the working condition is end anchor support and the anchorage section is located in the plastic softening zone and the fracture zone, the radial stress in the fracture zone within the anchorage section is: , The tangential stress in the fractured zone within the anchorage section is: ; When the working condition is end anchor support and the anchorage section is located in a fractured zone, the radial stress of the surrounding rock in the fractured zone within the anchorage section is: , The expression for the tangential stress of the surrounding rock in the fractured zone within the anchorage section is: ; In the formula: The radius of plastic failure; r p The radius of the plastic softening zone, r 0 represents the radius of the tunnel. This represents the radial distance from any point in the surrounding rock to the center of the tunnel. To soften the modulus, , The length of the free segment. The length of the anchorage section. The length of the anchor bolt. The dilatation coefficient of the rock mass in the plastic softening zone. For elastic modulus, Poisson's ratio, It is the internal friction angle. , , These represent the tangential strains in the elastic region, the plastic softening region, and the fracture region, respectively. , These represent the peak region of the rock mass and the residual cohesion, respectively. Indicates the residual strength of the rock mass. For the radial stress of the surrounding rock, For the tangential stress of the surrounding rock, All of these are coefficients related to the strength of the surrounding rock and the stress of the original rock. This is the correction factor for the anchoring coupling of the surrounding rock.

[0028] Five unique zone stress analysis formulas are matched for five support conditions, and each condition includes radial and tangential stress calculations. The formula parameters are highly compatible with the mechanical parameters of the three zones of the surrounding rock and the support parameters, realizing a one-to-one correspondence between "support condition - surrounding rock zone - stress calculation". This makes the stress inversion formula more targeted and practical for engineering, and greatly improves the inversion accuracy.

[0029] Preferably, the system also includes steps for surrounding rock stability assessment and early warning, result output, and system maintenance: based on the inverted stress field results, combined with the instability criterion of static load and mining-induced dynamic pressure disturbance superposition, the ultimate strength of the anchor bearing arch is calculated, surrounding rock stability assessment is carried out, and graded early warning signals are output; the inversion results are rendered in three dimensions to generate a three-dimensional stress cloud map and stress history change curve, and monitoring reports and early warning notices are automatically generated; the fiber optic grating monitoring network, demodulator, and other equipment are regularly calibrated and maintained to ensure the long-term stable operation of the monitoring system.

[0030] Based on stress inversion, the system extends to achieve full lifecycle management of surrounding rock stability assessment, early warning, result output, and system maintenance. Scientific early warning is achieved through instability criteria and ultimate strength of anchor bearing arch. The practicality of the results is improved by combining three-dimensional visualization and automatic report generation. At the same time, the system calibration and maintenance requirements are clarified to ensure the long-term stable operation of the monitoring and inversion system, making the technical solution both practical and sustainable.

[0031] The advantages of this invention are: (1) Breaking through the limitations of traditional point monitoring and realizing continuous monitoring of the entire stress field: This invention constructs a high-density fixed-point distributed fiber optic grating three-dimensional monitoring network in the surrounding rock of the roadway. The sensors are arranged along the borehole axis at a set interval, covering the entire area of ​​the fracture zone, plastic softening zone and elastic zone. This overcomes the defect of traditional micro-strain sensors and stress gauges that "substitute points for surfaces". It can obtain continuous strain data within the meter-level displacement range of the surrounding rock, and truly reflect the overall distribution characteristics and evolution law of the three-dimensional stress field of the surrounding rock of the roadway. This achieves a technological breakthrough from "discrete point monitoring" to "continuous monitoring of the entire stress field". (2) Deep coupling between sensing and surrounding rock, accurate monitoring data and strong anti-interference: The fiber optic cable is laid out with cement mortar grouting to ensure that the fiber optic cable is tightly coupled with the surrounding rock, ensuring the accuracy of strain data acquisition; at the same time, by using stainless steel protective pipes to protect the fusion joints and PVC pipe wedge-shaped grooves, combined with the characteristics of fiber optic sensing technology itself, electromagnetic and mechanical interference in the well is effectively avoided, solving the problems of weak anti-interference ability and poor long-term stability of traditional monitoring equipment, and ensuring that the data is accurate and reliable in the long term in complex well environments. (3) Deep integration of multiple models, high scientificity and accuracy of stress field inversion: This invention deeply integrates high-density fiber optic sensing measurement data with the constitutive model of surrounding rock zoning (elastic zone, plastic softening zone, and fracture zone follow the corresponding strength criteria respectively) and the volume force model of anchor support, and constructs a coupled inversion model; and establishes exclusive radial and tangential stress analytical formulas for various anchor support conditions, and substitutes real-time strain data as boundary conditions into the formula for iterative solution, realizing accurate and separate inversion of stress fields in different zones of surrounding rock, which greatly improves the theoretical scientificity and calculation accuracy of stress inversion; (4) Realize dynamic real-time monitoring and support accurate early warning of surrounding rock instability: Wavelength data is collected in real time through dense distributed explosion-proof fiber optic demodulators and transmitted synchronously to the ground server through the mining industrial ring network. The data acquisition frequency can be flexibly adjusted and rapid preprocessing such as temperature compensation and outlier removal is completed. Combined with the surrounding rock instability criterion of static load and mining dynamic pressure superposition, the ultimate strength of the anchor bearing arch is calculated to realize dynamic assessment and graded early warning of surrounding rock stability (such as normal, level 2 early warning, level 1 early warning). Compared with traditional static monitoring, it can capture stress field changes in a timely manner and provide direct and reliable data support for roadway disaster early warning. (5) Visual presentation of results, with good interpretability and operability in engineering applications: This invention performs three-dimensional visualization rendering of the radial and tangential stress distribution data obtained by inversion, generating three-dimensional stress cloud maps and stress history change curves, intuitively showing the evolution process of stress concentration areas; at the same time, the system can automatically generate monitoring reports and early warning notifications, and the ground monitoring center can remotely view the working status of underground equipment. Without the need for complex data analysis by professional personnel, on-site engineering technicians can quickly interpret the stress field characteristics, providing intuitive decision-making basis for roadway surrounding rock control and support scheme optimization; (6) Optimize monitoring costs and achieve cost reduction, efficiency improvement and long-term reliable operation: This invention significantly reduces the number of monitoring points through continuous monitoring, avoiding the high material and construction costs caused by the dense arrangement of sensors required by traditional point monitoring; at the same time, the fiber optic grating sensor and demodulator are both explosion-proof, wear-resistant and interference-resistant, and the system can operate continuously for a long time. Only simple calibration and maintenance are required periodically, which greatly reduces the later operation and maintenance costs of the equipment; in addition, the monitoring data and the surrounding rock control technology work together to provide timely feedback on the surrounding rock control effect, reduce the subsequent costs of roadway repair and disaster management caused by the instability of the surrounding rock, and achieve dual optimization of economic and engineering benefits. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the three zones of the surrounding rock in the tunnel after excavation disturbance according to the first embodiment of the present invention; Figure 2 This is a schematic diagram showing the positional relationship between the anchor body structure and the three zones of the surrounding rock in the roadway after disturbance, according to the first embodiment of the present invention. Figure 3 This is a flowchart of the stress field inversion method for surrounding rock based on high-density fixed-point distributed fiber optic gratings according to the first embodiment of the present invention. Figure 4 This is a flowchart of the practical operation of fiber optic monitoring downhole according to the first embodiment of the present invention; Figure 5 This is a schematic diagram of the fiber Bragg grating installation according to the first embodiment of the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0034] To make it easier to understand, let's first combine... Figure 1 A three-zone analysis of the surrounding rock is conducted. After tunnel excavation, the failure of the surrounding rock is not instantaneous, but rather begins in the fractured zone closest to the tunnel and gradually extends towards the deeper plastic softening and elastic zones. The formation of these three zones is essentially a self-adjustment process of the surrounding rock to adapt to the stress redistribution after excavation. Stress transfers from the tunnel surface to the depths, forming a stress gradient from high to low. Understanding the extent, thickness, and stress state of these three zones is crucial for tunnel support design. For example, the length of the anchor bolts needs to be sufficiently long to ensure that their anchoring section can penetrate into the plastic softening zone and even the elastic zone, thereby transferring the load from the fractured zone to the deeper, stable surrounding rock. Combined with... Figure 1As shown, the area closely following the contour of the tunnel is the surrounding rock closest to the tunnel, i.e., the innermost fractured zone. After the tunnel is excavated, this part of the surrounding rock loses its original support, and the stress is released instantly, causing the rock mass to be "crushed" or "cracked". Numerous internal fissures develop and connect, and the integrity and strength of the rock mass decrease sharply, even becoming loose and broken. The surrounding rock in this area has basically lost its bearing capacity and mainly relies on the later-implemented anchor bolts, anchor cables and other support structures to maintain stability. It is a high-risk area for tunnel instability.

[0035] The central region surrounding the fractured zone is the plastic softening zone. While the stress on this part of the surrounding rock is not as extreme as in the fractured zone, it has exceeded the elastic limit of the rock mass, resulting in irreversible plastic deformation. Simultaneously, micro-fractures within the rock mass continue to expand, leading to a gradual deterioration of its strength and stiffness (softening modulus) and a decrease in its bearing capacity. This area is a critical zone for stress transmission and energy dissipation; it transfers the high stress of the fractured zone to the deeper surrounding rock while constantly adjusting and adapting to new stress states. The anchoring section of the anchor bolt typically extends into this area to provide effective support resistance.

[0036] Located outside the plastic softening zone, occupying most of the surrounding rock area, is the elastic zone. This part of the surrounding rock is far from the roadway and experiences less disturbance; the stress remains within the elastic limit of the rock mass. Therefore, it only undergoes recoverable elastic deformation, and the integrity and mechanical parameters (such as strength and elastic modulus) of the rock mass remain essentially unchanged. The elastic zone provides final support and constraint for the internal plastic softening and fractured zones, maintaining the stability of the entire roadway's surrounding rock.

[0037] Example 1: Based on the positional relationship between the anchorage structure and the three zones of the surrounding rock in the disturbed roadway, the stress field distribution of the anchorage bearing structure under different anchorage conditions in actual engineering can be subdivided into five typical working conditions. Figure 2 As shown, it specifically includes: Scenario ① Full-length anchoring (full anchoring), with the anchor rod extending through the fractured zone and into the plastic softening zone: In this case, the anchor rod extends from the roadway surface (fractured zone) through the fractured zone, with the anchored section extending into the plastic softening zone. The rod simultaneously spans both the fractured and plastic softening zones. The anchor rod is fully coupled with the surrounding rock, providing constraint in the fractured zone and anchoring force in the plastic softening zone, forming a continuous stress transfer path. This effectively limits the expansion of the fractured zone while transferring the load from the fractured zone to the plastic softening zone. Scenario ② Full-length anchoring (full anchor), with the anchor rod entirely within the fractured zone: In this case, the anchor rod is entirely within the fractured zone and does not extend into the plastic softening zone; the entire anchoring section is within the fractured zone. The anchor rod only provides constraint within the fractured zone, offering limited constraint on the plastic softening zone. Stress concentration is significant in the fractured zone, easily leading to localized stress peaks, requiring higher support density or strength.

[0038] Scenario ③ End anchoring (end anchor), anchorage section located in the plastic softening zone: In this case, the free section of the anchor rod is located in the fracture zone, and the anchorage section is entirely located in the plastic softening zone. The anchorage end extends deep into the plastic softening zone to provide anchoring force. The free section provides constraint in the fracture zone, and the anchorage section provides the main anchoring force in the plastic softening zone. Stress is concentrated at the anchorage end, which can effectively transfer the load from the fracture zone to the plastic softening zone, making it suitable for scenarios with a small fracture zone.

[0039] Case 4: End anchoring (end anchor), with the anchoring section spanning both the fractured and plastic softening zones: In this case, the free section of the anchor bolt is located in the fractured zone, while the anchoring section spans both the fractured and plastic softening zones, with the anchoring end located in the plastic softening zone. The anchoring section provides constraint in both the fractured and plastic softening zones, resulting in a more uniform stress distribution. It can simultaneously limit the expansion of the fractured zone and the deformation of the plastic softening zone, making it suitable for roadways with a large fractured zone and significant dynamic pressure effects.

[0040] Situation ⑤ End anchoring (end anchor), the anchoring section is entirely located in the fractured zone: Both the free section and the anchoring section of the anchor are located within the fractured zone, and the anchoring end does not extend into the plastic softening zone. The anchor only provides constraint within the fractured zone and has no direct constraint on the plastic softening zone. Stress concentration in the fractured zone is significant, which can easily lead to attenuation of the anchoring force. It is necessary to combine it with other support measures (such as anchor cables, shotcreting) to improve overall stability.

[0041] See Figure 3 This embodiment uses case ① as an example to introduce the application of the surrounding rock stress field inversion method of this application. In this embodiment, full anchor support is adopted—the anchor bolt penetrates the fractured zone and extends into the plastic softening zone (mining roadway). The anchor bolt body penetrates the fractured zone and extends into the plastic softening zone. At this time... ,in Indicates the radius of the tunnel excavation. Indicates the effective length of the anchor bolt. This represents the radial distance from any point in the surrounding rock to the center of the tunnel.

[0042] In this embodiment, the tunnel is buried at a depth of 600m, and the original rock stress is... =15MPa, excavation radius =3.0m; using Φ22mm×2500mm high-strength threaded steel anchor bolts, anchor bolt preload force =100kN, anchor bolt spacing =800mm×800mm; Internal friction angle of surrounding rock =35°, peak cohesion =4.0MPa, residual cohesion =1.0MPa, elastic modulus =15GPa, Poisson's ratio μ=0.25, expansion factor m=1.2.

[0043] The specific steps of the surrounding rock stress field inversion method are as follows: See Figure 4 ① Material Transportation and Construction Preparation: Transport and verify construction materials: Transport materials and equipment such as metal-based cable strain gauge optical cables, stainless steel protective pipes, PVC installation pipes, early-strength cement mortar, and explosion-proof fiber optic demodulators to the underground drilling site via mine cars, and verify their model, quantity, and integrity. Accurately mark borehole locations according to the design: On the sidewall of the roadway, use a laser pointer to accurately mark three borehole locations with a spacing of 1.5m, a depth of 5.0m, and a drilling angle of -5° downwards. Verify that the borehole coordinates match the design drawings. In this embodiment, the number of boreholes, the spacing between boreholes, the depth of boreholes, and the drilling angle can be adjusted according to actual conditions.

[0044] ② Drilling and Fiber Optic Cable Laying: An anchor drilling rig is used for drilling, with a hole diameter of 42mm. This embodiment uses a 42mm hole diameter, but the actual hole diameter will be selected based on the actual conditions at the construction site. After cleaning the hole, the sensor fiber optic cable is bundled to the installation drill rod and inserted into the hole. The end of the sensor fiber optic cable is fused to the conductor fiber optic cable using a hot melt machine. The fusion joint is fitted into a stainless steel protective tube. A wedge-shaped groove is made in the PVC installation pipe, and the protected fusion joint and fiber optic cable are placed into the groove of the PVC installation pipe and fixed. The fiber optic cable is pushed section by section to the designed drilling depth, and cement mortar with a water-cement ratio of 0.4:1 is poured in. The entire section is compacted using a tamper to ensure tight coupling between the fiber optic cable and the surrounding rock. Curing is carried out for 72 hours. This embodiment uses cement mortar with a water-cement ratio of 0.4:1. The actual water-cement ratio will be adjusted according to the actual conditions at the construction site to ensure tight coupling between the fiber optic cable and the surrounding rock.

[0045] ③ Network connectivity debugging: At the drilling site, complete the splicing and protection of the communication optical cable and strain gauge optical cable. Lay the communication optical cable along the tunnel wall and connect it to the underground industrial ring network switch. Perform IP address matching between the surface monitoring center and the underground dense distributed explosion-proof fiber optic demodulator to complete network connectivity debugging. Set the sampling frequency to 1Hz and the data storage interval to 1min, and complete temperature compensation calibration. The sampling frequency and data storage interval can be adjusted according to actual conditions.

[0046] ④ Construction of the Coupled Inversion Model of Surrounding Rock Stress Field: As the core innovation of this application, the construction of the coupled inversion model of surrounding rock stress field includes the construction of the constitutive model of surrounding rock zoning and the construction of the volumetric force model of anchor bolt support, as detailed below: Construction of a Zonal Constitutive Model for Surrounding Rock: Traditional inversion models for three zones of surrounding rock rely solely on geometric data to determine the boundaries of the elastic, plastically softened, and fractured rock masses. This approach is flawed and uses a single mechanical model to calculate stresses in different zones, leading to significant discrepancies between actual and calculated stresses. This application constructs a zonal constitutive model for surrounding rock, establishing corresponding strength criteria and deformation formulas for linear elastic deformation in the elastic zone, plastic deformation plus strength softening in the plastically softened zone, and residual strength deformation plus loose fracture in the fractured zone (e.g., Hooke's Law for the elastic zone, Mohr-Coulomb criterion plus softening modulus for the plastically softened zone, and residual strength criterion for the fractured zone). This ensures that the strain-to-stress conversion aligns with the actual mechanical characteristics of the rock mass in each zone. Specifically, the fractured zone satisfies the residual strength criterion. The boundary between the elastic zone and the plastic softening zone satisfies the Mohr-Coulomb criterion. The strength decay in the plastic softening zone is expressed as: ;in , , Peak strength of the rock mass This represents the tangential stress at the boundary. Indicates the radial stress at the boundary. The friction angle within the rock mass. For the strength of the rock mass in the plastic softening zone, The softening modulus is calculated. =2.0GPa, , , These represent the tangential strains in the elastic region, the plastic softening region, and the fracture region, respectively. , These represent the peak region of the rock mass and the residual cohesion, respectively. This represents the tangential stress in the fracture zone. Indicates the radial stress in the fractured zone. This represents the residual strength of the rock mass. Through mechanical parameters in the constitutive model (such as peak cohesion, residual cohesion, and softening modulus), the boundary positions between the fractured zone and the plastic softening zone, as well as between the plastic softening zone and the elastic zone, can be quantitatively identified. This allows the zoning of stress inversion to no longer be a simple geometric judgment, but a precise definition based on the mechanical properties of the rock mass, providing accurate zoning stress data for subsequent stability assessments.

[0047] Construction of the Anchor Bolt Support Volumetric Force Model: After completing the constitutive model of the surrounding rock zone, the volumetric force model of the anchor bolt support is constructed. The purpose of constructing the anchor bolt support volumetric force model is to quantify the support effect of the anchor bolt into mechanical parameters that can be substituted into the stress balance equation, realize the deep coupling analysis of "surrounding rock-support", and solve the technical defect of traditional monitoring that "ignores the interaction between support and surrounding rock". The specific calculation formula is as follows: ,in For anchor bolt preload, The radius of the alleyway, , The spacing between anchor bolts. It is a radial volume force. The length of the anchor bolt. This represents the radial distance from any point in the surrounding rock to the center of the roadway. Through radial volume force calculations, the originally discrete rock bolt support effect is transformed into a continuously calculable mechanical quantity that can be directly substituted into the stress equilibrium differential equation of the surrounding rock. In this process, numerical coupling between the support function and the stress field of the surrounding rock is achieved.

[0048] The constitutive model of surrounding rock zoning solves the problem of how to calculate stress in accordance with the actual situation of surrounding rock, while the volumetric force model of anchor bolt support solves the problem of how to incorporate the support effect into the stress calculation in accordance with the actual situation of support. The combination of the two upgrades the stress field inversion from the traditional "simple sensor data calculation" to a precise inversion of "sensor measurement + mechanical coupling + engineering practice".

[0049] ⑤ Digital strain data acquisition and preprocessing: The axial center wavelength offset of the optical cable is acquired in real time by a demodulator and converted into radial strain distribution data of the surrounding rock based on the principle of optical fiber sensing. The ground server is used to process the data, removing outliers, smoothing with moving averages, and reducing noise with wavelets, generating a digital map of continuous strain curves corresponding to the borehole depth. Using the constitutive model of the surrounding rock zoning from step ④, the strain data is converted into stress (…). Substituting this into the constitutive model formula for the surrounding rock zoning, the maximum radial distance satisfying the residual strength criterion is the final value. The maximum radial distance that satisfies the peak intensity criterion is the final value. The radius of the plastic softening zone was obtained by combining the measurement results and calculations. =4.2m, calculate the plastic failure radius. =1.8m.

[0050] ⑥ Stress field inversion calculation and visualization evaluation: After completion and processing, the preprocessed strain data... Substituting the surrounding rock and support parameters into the stress analysis formula for the anchor bolt penetrating the fractured zone and extending into the plastic softening zone under full anchoring conditions: When anchoring in the fractured zone (i.e.) The radial stress in the anchorage fracture zone is: ; The tangential stress in the fracture zone within the anchorage range is:

[0051] in , , , , It is a coefficient related to the strength of the surrounding rock and the stress of the original rock. The specific value varies with the engineering environment and must be determined experimentally.

[0052] When anchoring in the plastic softening zone (i.e.) The radial stress in the plastic softening zone within the anchorage range is:

[0053] The tangential stress in the plastic softening zone within the anchorage range is:

[0054] After substituting the parameters into the calculation, the radial stress in the fracture zone is 2.5~6.8MPa and the tangential stress is 7.2~15.6MPa, while the radial stress in the plastic softening zone is 6.8~12.3MPa and the tangential stress is 15.6~22.5MPa.

[0055] Based on the instability criterion: In this embodiment, the graded early warning adopts a three-level early warning system, namely, if... If it is in a normal and stable state, then it indicates that the state is stable. This indicates that the surrounding rock stress is approaching its limit, posing a certain risk. At this point, a level two warning is triggered. This indicates that the surrounding rock stress exceeds the limit, posing a risk of instability and triggering a Level 1 warning. The specific graded warning mechanism can be adjusted according to actual needs. In the formula... , Indicates the ultimate strength of the anchorage bearing arch. For safety reasons, a factor of 1.2 is selected in this embodiment. The risk amplification factor is 1.1 in this embodiment. The specific safety factor and risk amplification factor can be adjusted according to actual needs. After substituting the relevant parameters, the ultimate strength of the anchorage bearing arch in this embodiment is... =28MPa, fracture zone Similarly, the plastic softening zone Therefore, in this embodiment Therefore, it was determined that the surrounding rock was in a normal and stable state. Since the surrounding rock was in a normal and stable state, the system issued no warning, generated a digital monitoring report, and synchronized it to the mine's industrial ring network.

[0056] Example 2: See Figure 3 This embodiment focuses on scenario ②. In this embodiment, full anchor support is used—the anchor bolt is completely within the fractured zone (tunneling roadway), and the anchor bolt body is completely within the fractured zone. .

[0057] In this embodiment, the tunnel is buried at a depth of 450m, and the original rock stress is... =12MPa, excavation radius =2.8m; using Φ20mm×2000mm threaded steel anchor bolts, anchor bolt preload force =80kN, anchor bolt spacing =900mm×900mm; Internal friction angle of surrounding rock =32°, peak cohesion =3.5MPa, residual cohesion =0.8MPa, elastic modulus =12GPa, Poisson's ratio μ=0.28, expansion coefficient m =1.15, softening modulus The calculated value is 1.8 GPa.

[0058] The other steps are consistent with those in Example 1, and the radius of the plastic softening zone is obtained by combining the measurement results and calculations. Calculate the plastic failure radius .

[0059] Preprocessed strain data Substituting the surrounding rock and support parameters into the stress analysis formula for full-anchor support—where the anchor bolt is completely in the fractured zone: When the fracture zone is within the anchorage range (i.e.) The radial stress in the fractured zone within the anchorage range is:

[0060] The tangential stress in the fracture zone within the anchorage range is:

[0061] When the fracture zone is outside the anchorage range (i.e. The radial stress of the surrounding rock in the fractured zone outside the anchorage range is:

[0062] The tangential stress of the surrounding rock in the fractured zone outside the anchorage range is:

[0063] in , , , , , , , This is a coefficient related to the strength of the surrounding rock and the stress of the original rock, which will not be specifically described in subsequent embodiments. The specific value varies with the engineering environment and must be determined experimentally.

[0064] Inversion revealed radial stress of 3.1–7.5 MPa and tangential stress of 8.2–16.3 MPa within the anchorage range of the fractured zone, and radial stress of 2.0–3.1 MPa and tangential stress of 5.8–8.2 MPa outside the anchorage range. Based on the instability criterion, the maximum superimposed stress of the surrounding rock was calculated to be 21.5 MPa. =25MPa), at this time The system automatically triggers a level-two digital early warning, which pops up on the monitoring center interface along with relevant suggestions.

[0065] Example 3: See Figure 3 This embodiment focuses on scenario ③. In this embodiment, end anchor support is used—the anchoring section is located in the plastic softening zone (development roadway), and the anchor bolt body is completely within the plastic softening zone. .

[0066] In this embodiment, the tunnel is buried at a depth of 800m, and the original rock stress is... =20MPa, excavation radius =3.5m; using Φ25mm×3000mm fiberglass anchor bolts, free section =1000mm, anchorage section =2000mm, anchor bolt preload =120kN, anchor bolt spacing =700mm×700mm; Internal friction angle of surrounding rock =38°, peak cohesion =5MPa, residual cohesion =1.2MPa, elastic modulus =18GPa, Poisson's ratio μ=0.23, expansion coefficient m =1.3, softening modulus The calculated value is 2.5 GPa.

[0067] The other steps are consistent with those in Example 1, and the radius of the plastic softening zone is obtained by combining the measurement results and calculations. Calculate the plastic failure radius .

[0068] Preprocessed strain data Substituting the surrounding rock and support parameters into the stress analysis formula for the end anchor support—anchoring section located in the plastic softening zone: End anchoring is used and the anchorage section is located in the plastic softening zone (i.e. The radial stress in the plastic softening zone within the anchorage section is:

[0069] The tangential stress in the plastic softening zone within the anchorage section is:

[0070] Solve for the range within the anchorage section (i.e.) The stress in the surrounding rock of the plastic softening zone, and the radial stress in the plastic softening zone inside the anchorage section are:

[0071] The tangential stress in the plastic softening zone inside the anchorage section is:

[0072] Inside the anchorage section (i.e.) The radial stress in the fracture zone is:

[0073] The tangential stress of the surrounding rock in the fractured zone is:

[0074] The inversion yielded radial strength of 4.2–8.8 MPa and tangential strength of 9.5–19.2 MPa in the fractured zone, and radial strength of 12.3–18.6 MPa and tangential strength of 24.5–32.1 MPa in the plastic softening zone within the anchorage section. The ultimate strength of the anchorage bearing arch was then calculated. =30MPa, the maximum superimposed stress of the surrounding rock is 28MPa. When the intensity exceeds the limit, the system triggers a Level 1 digital early warning and simultaneously sends an early warning notification to the on-site operation terminal and the ground monitoring center.

[0075] Example 4: See Figure 3 This embodiment focuses on scenario ④. In this embodiment, end-anchor support is used—the anchoring section spans both the fractured zone and the plastic softening zone (deep mining roadway). The anchoring section simultaneously crosses both the fractured zone and the plastic softening zone. .

[0076] In this embodiment, the tunnel is buried at a depth of 900m, and the original rock stress is... =22MPa, excavation radius =3.2m; using Φ22mm×3500mm high-strength anchor bolts, free section =1200mm, anchorage section =2300mm, anchor bolt preload =130kN, anchor bolt spacing =750mm×750mm; Internal friction angle of surrounding rock =36°, peak cohesion =4.8MPa, residual cohesion =1.1MPa, elastic modulus =16GPa, Poisson's ratio μ=0.24, expansion coefficient m =1.25, softening modulus The calculated value is 2.2 GPa.

[0077] The other steps are consistent with those in Example 1, and the radius of the plastic softening zone is obtained by combining the measurement results and calculations. Calculate the plastic failure radius .

[0078] Preprocessed strain data Substituting the surrounding rock and support parameters into the stress analysis formula for the end anchor support-anchoring section spanning the fractured zone and the plastic softening zone: When the anchorage section is located in the plastic softening zone and the fracture zone, the radial stress in the fracture zone within the anchorage section is:

[0079] The tangential stress in the fractured zone within the anchorage section is:

[0080] Inside the anchorage section (i.e.) That is, the radial stress in the fracture zone of the free segment is:

[0081] The tangential stress in the fractured zone inside the anchorage section is:

[0082] A three-dimensional digital model of the roadway stress field was generated. The stress peak of the anchorage section across the region was found to be at the boundary between the fractured zone and the plastic softening zone (tangential stress 35.2 MPa). Other steps were consistent with the early warning operation in Example 1.

[0083] Example 5: See Figure 3 This embodiment focuses on scenario ⑤. In this embodiment, the end anchor support-anchoring section is entirely located in the fractured zone (soft rock tunnel), and the anchoring section is entirely in the fractured zone. .

[0084] In this embodiment, the tunnel is buried at a depth of 500m, and the original rock stress is... =13MPa, excavation radius =3m; using Φ20mm×2500mm resin anchor bolts, free section =800mm, anchorage section =1700mm, anchor bolt preload =70kN, anchor bolt spacing =800mm×800mm; Internal friction angle of surrounding rock =30°, peak cohesion =2.5MPa, residual cohesion =0.6MPa, elastic modulus =10GPa, Poisson's ratio μ=0.3, expansion coefficient m =1.4, softening modulus The calculated value is 1.5 GPa.

[0085] The other steps are consistent with those in Example 1. The plastic failure radius is calculated by combining the measurement results and the calculated radius of the plastic softening zone. .

[0086] Preprocessed strain data Substituting the surrounding rock and support parameters into the stress analysis formula for end anchor support—anchor section entirely located in the fractured zone: The stress expression for the surrounding rock in the fractured zone within the anchorage section is as follows:

[0087] The expression for the tangential stress of the surrounding rock in the fractured zone within the anchorage section is:

[0088] Solve for the range within the anchorage section (i.e.) The radial stress in the fracture zone is:

[0089] The tangential stress in the fractured zone inside the anchorage section is:

[0090] The inversion revealed radial stress of 2.0–5.5 MPa and tangential stress of 4.5–10.2 MPa within the anchorage section, with a stress attenuation rate of 0.12 MPa / d. The system triggers a secondary digital early warning based on the attenuation rate and automatically calculates the remaining anchorage force, providing a digital quantitative basis for anchor bolt replacement and resin cartridge reinforcement.

[0091] Example 6: See Figure 3 In this embodiment, multi-section joint monitoring—whole-area stress field inversion of three zones of surrounding rock (composite roadway) is used as an example.

[0092] In this embodiment, the tunnel is buried at a depth of 700m, and the original rock stress is... =18MPa, excavation radius =3.3m; A combination of full anchor and end anchor support is used, with Φ22mm×2800mm full anchor bolts on the top slab and Φ22mm×3000mm end anchor bolts on both sides; Internal friction angle of the surrounding rock. =35°, peak cohesion =4.2MPa, residual cohesion =1.0MPa, elastic modulus =14GPa, Poisson's ratio μ=0.25, expansion coefficient m =1.2, softening modulus The calculated value is 2.1 GPa.

[0093] The other steps are consistent with those in Example 1. Grating strain data from 18 boreholes in 6 cross sections are collected. The multi-source data are integrated through a spatiotemporal fusion algorithm to generate a digital strain grid model of the entire tunnel area. The support conditions (full anchor / end anchor) of different cross sections are automatically identified and the corresponding stress analysis formulas are matched.

[0094] Based on a fiber optic monitoring cloud platform, the fused strain data is substituted into the stress analysis formulas for five working conditions in this application. A coupled inversion algorithm is used to achieve continuous stress field inversion across the entire range—from the fractured zone to the plastic softening zone and the elastic zone—while simultaneously calculating the dynamic boundary changes of each region. A digital three-dimensional stress field model of the surrounding rock in the three zones of the roadway is generated on the fiber optic monitoring cloud platform, enabling real-time visualization of the dynamic evolution of the stress field, changes in regional boundaries, and the movement of stress concentration zones. Combined with instability criteria, a comprehensive stability assessment of the entire surrounding rock is conducted, generating digital surrounding rock control reports for different sections and regions. For full-anchor sections, it is recommended to strengthen the preload; for end-anchor sections, it is recommended to install additional anchor cables; and for the elastic zone, the evolution of stress concentration zones is monitored closely.

[0095] This application uses a high-density, fixed-point distributed fiber optic grating sensor network as its core. Through precise underground construction and data acquisition, it obtains continuous strain data of the surrounding rock in the roadway from the fractured zone, the plastic softening zone to the elastic zone. Then, combined with the constitutive model of the surrounding rock zoning and the volumetric force model of the anchor support, it constructs a stress inversion system of "measured strain + mechanical coupling", transforming the strain data into a precise three-dimensional stress field. Finally, it conducts stability assessment and graded early warning through the instability criterion of the anchor bearing arch, and outputs the results in a digital visualization manner, forming a set of roadway surrounding rock safety management methods that integrate "monitoring-inversion-assessment-early warning". This solves the technical bottleneck of traditional monitoring, which is "point-to-surface, insufficient inaccuracy, and lack of deep coupling between support and surrounding rock mechanical characteristics", and provides a scientific basis for the precise control of roadway surrounding rock under the influence of mining.

[0096] The method described in this application has been successfully implemented in the tunneling and mining engineering of the Pansan Mine. Addressing the complex working conditions of superimposed static and dynamic pressures under mining influence, it has achieved full-process monitoring and inversion of the stress field of the surrounding rock in key roadways. Field application data shows that this method solves the industry pain points of traditional monitoring methods, such as "point-to-surface" and "discrete data." The fiber optic grating sensor network can stably collect high-density fixed-point strain data of the surrounding rock at a depth of 0.5~1.0m. The stress inversion accuracy is significantly improved compared to traditional methods, accurately identifying the stress distribution characteristics and evolution patterns of the three zones of the surrounding rock. Based on the inversion results, the surrounding rock instability early warning system can predict the risk of deformation and failure of the surrounding rock in advance, with an on-site early warning accuracy rate of over 95%, providing scientific data support for timely adjustment of support parameters and implementation of reinforcement measures. After applying this method, the deformation of the surrounding rock in the target roadway was effectively controlled within the design allowable range, and no engineering accidents such as surrounding rock instability, roof collapse, or sidewall collapse occurred. The roadway support and maintenance costs were significantly reduced, and the construction efficiency was greatly improved. It performed excellently in terms of engineering practicality, stability, and economy, and fully met the actual application needs of coal mine roadway engineering sites.

[0097] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Terms such as "upper," "lower," "left," "right," "front," and "rear" used in the invention are merely for clarity of description and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0098] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for inverting a stress field of a surrounding rock, characterized by, The specific steps include: constructing a fiber optic grating sensor network in the roadway, acquiring and preprocessing surrounding rock strain data, constructing a constitutive model of the surrounding rock zoning, and constructing a volumetric force model of the anchor bolt support; acquiring distributed strain data of the surrounding rock through a high-density fixed-point distributed fiber optic grating sensor network, and constructing a coupled inversion model by combining the constitutive model of the surrounding rock zoning and the volumetric force model of the anchor bolt support to invert the continuous stress field of the fractured zone, plastic softening zone, and elastic zone of the surrounding rock in the roadway.

2. The stress field inversion method of surrounding rock according to claim 1, characterized in that, The construction of the fiber optic grating sensor network includes the following steps: selecting roadway measuring points and drilling holes vertically to the roadway sidewalls; selecting strain sensing optical cables, fixing them to the installation drill rods and inserting them into the holes; injecting cement mortar into the holes and compacting it; and completing the sensor deployment after the cement has solidified; setting up monitoring sections along the roadway axis; drilling holes in the top plate and sidewalls of the sections to deploy sensors; and connecting all the sensors in the holes in series along the axis at a preset interval to form a monitoring chain, thus constituting a three-dimensional monitoring network covering the three zones of the surrounding rock.

3. The method for inverting the stress field of surrounding rock according to claim 2, characterized in that, The specific process of installing the fiber optic grating sensor network in the well includes: transporting and verifying construction materials; accurately marking and verifying the drilling points according to the design; fusing the sensing optical cable and the conductor optical cable using a hot melt machine, inserting the splice into a stainless steel protective tube, and wedge-grooving the PVC installation pipe; placing the protected splice and optical cable into the PVC installation pipe groove and fixing them, pushing them section by section to the designed drilling depth, and injecting cement grout to solidify the entire section; completing the splicing and protection of the communication optical cable and strain optical cable at the drilling site, laying the communication optical cable along the roadway wall and connecting it to the underground industrial ring network switch; matching the IP addresses of the ground monitoring center and the underground dense distributed explosion-proof fiber optic demodulator to complete the network connection debugging.

4. The method for inverting the stress field of surrounding rock according to claim 1, characterized in that, The acquisition and preprocessing of the surrounding rock strain data includes: acquiring the center wavelength offset of the fiber optic grating sensor in real time through a densely distributed explosion-proof fiber optic demodulator, converting it into radial strain distribution data of the surrounding rock according to the fiber optic sensing principle; performing temperature compensation, outlier removal and data smoothing on the strain data; and automatically identifying the working condition of the anchor bolt support based on the strain distribution characteristics.

5. The method for inverting the stress field of surrounding rock according to claim 4, characterized in that, The working conditions of the anchor bolt support include: when fully anchored, the anchor bolt body penetrates the fractured zone and extends into the plastic softening zone; when fully anchored, the anchor bolt body is in the fractured zone; when end-anchored, the anchorage section is in the plastic softening zone; when end-anchored, the anchorage section is in both the plastic softening zone and the fractured zone; and when end-anchored, the anchorage section is in the fractured zone.

6. The method for inverting the stress field of surrounding rock according to claim 1, characterized in that, The construction of the surrounding rock zonal constitutive model follows the following strength criterion: the boundary between the elastic zone and the plastic softening zone satisfies the Mohr-Coulomb criterion, i.e. The strength of the plastic softening zone decreases with the softening modulus, as shown in the formula: The fractured zone meets the residual strength criterion of the rock mass. In the formula This represents the tangential stress at the boundary. Indicates the radial stress at the boundary. This represents the tangential stress in the fracture zone. Indicates the radial stress in the fractured zone. Peak strength of the rock mass Indicates the residual strength of the rock mass. For the strength of the rock mass in the plastic softening zone, , The friction angle within the rock mass. To soften the modulus, , , These represent the tangential strains in the elastic region, the plastic softening region, and the fracture region, respectively. , These represent the peak zone of the rock mass and the residual cohesion, respectively.

7. The method for inverting the stress field of surrounding rock according to claim 1, characterized in that, The anchor bolt support volume force model is constructed as follows: the anchor bolt preload is equivalent to the radial volume force acting on the surrounding rock, and the calculation formula is as follows: ,in For anchor bolt preload, The radius of the alleyway, , The spacing between anchor bolts. It is a radial volume force. The length of the anchor bolt. This represents the radial distance from any point in the surrounding rock to the center of the tunnel.

8. The method for inverting the stress field of surrounding rock according to claim 1, characterized in that, It also includes stress field inversion calculation and visualization. The specific process of stress field inversion is as follows: input the roadway geometric parameters, surrounding rock mechanical parameters, and support parameters into the ground server, and configure the monitoring parameters; use the pre-processed strain data as boundary conditions and input parameters, substitute them into the stress analysis formulas corresponding to various anchor support conditions, and iteratively solve to obtain the continuous distribution of radial stress and tangential stress in the fractured zone, plastic softening zone, and elastic zone of the surrounding rock, and complete the coupled analysis of static load and mining dynamic pressure superposition.

9. The method for inverting the stress field of surrounding rock according to claim 5, characterized in that, The stress analysis formulas for each type of anchor support condition include formulas for calculating radial stress and tangential stress in the corresponding surrounding rock zone, specifically including: When the working condition is full anchoring, the anchor rod body penetrates the fractured zone and extends into the plastic softening zone. The radial stress in the plastic softening zone within the anchoring range is: The tangential stress in the plastic softening zone within the anchorage range is: ； When the working condition is full anchoring, the entire length of the anchor rod is located in the fractured zone, and the radial stress of the surrounding rock in the fractured zone outside the anchoring range is: ， The tangential stress of the surrounding rock in the fractured zone outside the anchorage range is: ； When the working condition is end anchor support and the anchorage section is located in the plastic softening zone, the radial stress in the plastic softening zone within the anchorage section is: ， The tangential stress in the plastic softening zone within the anchorage section is: ； When the working condition is end anchor support and the anchorage section is located in the plastic softening zone and the fracture zone, the radial stress in the fracture zone within the anchorage section is: ， The tangential stress in the fractured zone within the anchorage section is: ； When the working condition is end anchor support and the anchorage section is located in a fractured zone, the radial stress of the surrounding rock in the fractured zone within the anchorage section is: ， The expression for the tangential stress of the surrounding rock in the fractured zone within the anchorage section is: ； In the formula: The radius of plastic failure; r p The radius of the plastic softening zone, r 0 represents the radius of the tunnel. This represents the radial distance from any point in the surrounding rock to the center of the tunnel. To soften the modulus, , The length of the free segment. The length of the anchorage section. The length of the anchor bolt. The dilatation coefficient of the rock mass in the plastic softening zone. For elastic modulus, Poisson's ratio, It is the internal friction angle. , , These represent the tangential strains in the elastic region, the plastic softening region, and the fracture region, respectively. , These represent the peak region of the rock mass and the residual cohesion, respectively. Indicates the residual strength of the rock mass. For the radial stress of the surrounding rock, For the tangential stress of the surrounding rock, All of these are coefficients related to the strength of the surrounding rock and the stress of the original rock. This is the correction factor for the anchoring coupling of the surrounding rock.

10. The method for inverting the stress field of surrounding rock according to claim 1, characterized in that, It also includes steps for surrounding rock stability assessment and early warning, result output, and system maintenance: Based on the inverted stress field results, combined with the instability criterion of static load and mining-induced dynamic pressure disturbance superposition, the ultimate strength of the anchor bearing arch is calculated, surrounding rock stability assessment is carried out, and graded early warning signals are output; the inversion results are rendered in three dimensions to generate three-dimensional stress cloud maps and stress history change curves, and monitoring reports and early warning notices are automatically generated; the fiber optic grating monitoring network, demodulator, and other equipment are regularly calibrated and maintained to ensure the long-term stable operation of the monitoring system.

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