Asymmetric high ground stress tunnel rock burst microseismic sensor arrangement method

Abstract

The application provides a non-symmetrical high ground stress tunnel rock burst microseismic sensor arrangement method and relates to the technical field of tunnel engineering. Based on tunnel surrounding rock geological data, according to non-symmetrical original rock ground stress distribution and tunnel section geometric characteristics, the non-symmetrical high stress tunnel stability is three-dimensionally numerically simulated, the non-symmetrical high stress tunnel energy is calculated, the rock burst risk area position is determined, the microseismic sensors are arranged in front and back of the stress concentration area, the area with higher risk and the nearby area are always contained in the two groups of microseismic sensor arrays arranged in front and back of the tunnel face, the microseismic sensors work cooperatively and are staggered in space, the installation and arrangement of the microseismic sensors follow the stress concentration area and move forward and backward and always keep a certain distance range from the stress area. The application can make more effective micro-fracture source signals in the tunnel stress concentration area and the nearby area be captured by the microseismic sensors, improve the microseismic source positioning precision and lay a foundation for the accurate prediction of deep buried hard rock tunnel disasters.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering technology, and in particular to a method for arranging microseismic sensors for rockburst in asymmetric high-stress tunnels. Background Technology

[0002] Deeply buried tunnels are characterized by asymmetric high ground stress, which can easily lead to stress concentration in certain areas of the tunnel, making them key control points for the stability of the surrounding rock. During tunnel excavation, intense stress adjustments will occur, and the use of drill-and-blast methods can cause catastrophic accidents such as rock bursts, collapses, or rockfalls in stress concentration areas, resulting in casualties, equipment damage, and project delays.

[0003] In the cross-section of tunnels under high ground stress, asymmetrical stress distribution often occurs. The surrounding rock in areas of stress concentration is prone to generating high energy and is prone to rock bursts, making it an important part of controlling tunnel stability.

[0004] As the tunnel is excavated, the tangential stress σ of the surrounding rock behind the high-stress tunnel face increases. θ Gradually increasing radial stress σ r As the stress decreases, the stress difference (σ1-σ3, σ2-σ3) increases, and the surrounding rock gradually enters an unfavorable stress state. To mitigate these risks, monitoring microseismic activity in these tunnels is crucial.

[0005] Microseismic monitoring technology is currently widely used in safety monitoring of mines, underground laboratories, slopes, tunnels, and other engineering projects in many countries, yielding a series of research results. Microseismic monitoring technology utilizes microseismic sensors deployed in different spatial locations to capture seismic wave information emitted during the micro-fracture process of rock masses. This information is then analyzed and processed to determine the time, location, magnitude, and energy release of microseismic events. Based on this, the internal stress state and failure status of the rock mass can be inferred, thereby enabling the assessment and early warning of rock mass stability.

[0006] Experience shows that stress concentration zones form in the surrounding rock perpendicular to the line connecting the maximum principal stresses on the tunnel cross-section behind the tunnel face, making these zones crucial for rockburst microseismic monitoring. The application of microseismic monitoring technology in asymmetric high-stress tunnels faces several challenges, including: 1) Traditional microseismic sensor placement methods generally employ geometric symmetry, failing to consider the characteristics of stress concentration zones in asymmetric high-stress tunnels. This often results in monitoring locations that do not align with the easily damaged areas within the stress concentration zones, hindering effective assessment of surrounding rock stability; 2) Existing sensor borehole locations and depths do not consider stress concentration zones caused by asymmetric high-stress, preventing effective continuous monitoring of microseismic events; 3) Research on how to systematically monitor potential microfractures in asymmetric high-stress tunnel rock masses in a timely, efficient, and accurate manner, evaluate the degree of surrounding rock damage, and identify potential instability zones in advance to correctly determine surrounding rock stability remains lacking both domestically and internationally. Therefore, regarding the application of microseismic monitoring technology in the construction process of asymmetric high-stress tunnels, it is necessary to study reasonable sensor layout methods and establish a microseismic monitoring scheme adapted to the excavation process and tunneling speed, so as to lay the foundation for the application of microseismic monitoring technology in the excavation process of asymmetric high-stress tunnels. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing an asymmetric high-stress tunnel rockburst microseismic sensor arrangement method. This method solves the problem that the microseismic monitoring sensor array is difficult to surround the stress concentration area and the surrounding rock mass during tunnel excavation, so that more effective micro-fracture source signals in the stress concentration area and its vicinity can be captured by the microseismic sensor, thereby improving the microseismic source positioning accuracy and laying the foundation for accurate prediction and forecasting of disasters in deeply buried hard rock tunnels.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] A method for arranging microseismic sensors for rockburst in asymmetric high-stress tunnels includes the following steps:

[0010] Step S1: Based on the geological data of the surrounding rock of the tunnel, and according to the asymmetric original rock stress distribution and the geometric characteristics of the tunnel cross section, a three-dimensional numerical simulation of the stability of the asymmetric high stress tunnel is carried out, and the energy of the asymmetric high stress tunnel is calculated. Combined with the construction information, the location of the stress concentration zone behind the tunnel face of the asymmetric high stress tunnel is determined.

[0011] Step S2: In the stress concentration zone behind the tunnel face of the asymmetric high-stress tunnel, multiple boreholes are set from the tunnel wall to the interior of the surrounding rock as microseismic monitoring holes. The microseismic monitoring holes are arranged in a staggered manner in space.

[0012] Step S3: Install microseismic sensors in different radial depth areas of the borehole. The microseismic sensors are all installed in the rock mass inside the tunnel wall by being embedded in the borehole. The embedment depth of the microseismic sensors must exceed the relaxation depth of the surrounding rock. The borehole depth must be greater than the placement depth of the microseismic sensors.

[0013] Step S4: Arrange N known microseismic sources in the tunnel space. The three-dimensional coordinates and occurrence time of the known microseismic sources are known. Analyze the positioning accuracy of the sensor arrangement scheme in Step S3. When the positioning accuracy of the microseismic sources reaches the set threshold, determine the arrangement scheme of the microseismic sensors and inject grout into the borehole to fix the microseismic sensors to the rock mass. If the positioning accuracy of the seismic sources does not reach the set threshold, fine-tune the borehole position and reposition the microseismic sensors until the positioning accuracy reaches the set threshold.

[0014] Step S5: When the stress concentration area is supported by secondary support, the regional microseismic energy and activity gradually decrease. Determine the next stress concentration area according to Step 1, and rearrange the microseismic sensors according to Steps 2 to 4 until the tunnel excavation is completed.

[0015] Step S6: During tunnel construction, a local area network is established between the microseismic monitoring center inside the tunnel and the microseismic monitoring project department outside the tunnel through the existing communication network. This allows monitoring personnel to collect and store microseismic activity at different depths within the stress concentration zone behind the tunnel face in a timely manner and analyze it. Based on the monitoring results, feedback on rockburst risk is provided in a timely manner.

[0016] Furthermore, in step S1, the specific method for calculating the energy of the asymmetric high-stress tunnel is as follows:

[0017] The total energy of the principal stress space rock mass, tracing the energy process of a unit, is specifically expressed as follows:

[0018]

[0019] Where U is the total work done by the principal stress in the direction of the principal strain; σ i The three principal stresses of the rock mass are ε. i The three principal strains of the rock mass are i = 1, 2, and 3.

[0020] Furthermore, the stress concentration zone is located in the surrounding rock of the tunnel behind the working face, perpendicular to the line connecting the maximum principal stresses of the asymmetric high-stress tunnel.

[0021] Furthermore, two monitoring sections are used before and after the stress concentration zone, with four microseismic sensors arranged on each monitoring section. The first row of microseismic sensors is 20m in front of the stress concentration zone, and the second row of microseismic sensors is 20m behind the stress concentration zone. Each microseismic sensor requires a hole to be drilled each time it is installed. The hole depth is 2-4m and the diameter is 75mm.

[0022] Furthermore, microseismic sensors are installed at three locations: the surface, the inward surface, and the deep layer, to receive information on rock fractures at different radial depths within the surrounding rock.

[0023] Furthermore, the microseismic sensor employs a combination of unidirectional and tridirectional velocity sensors, with a measurement range of 7–2000 Hz, to collect information on rock fractures within the surrounding rock.

[0024] Furthermore, in the stress concentration areas, triaxial velocity sensors are preferentially arranged around the corners and inflection points of the tunnel, while uniaxial and triaxial velocity sensors are alternately arranged in the remaining microseismic monitoring holes.

[0025] Furthermore, using specialized data processing software, the source parameters of each microseismic event were calculated, including microseismic release energy, apparent volume, seismic moment, and moment magnitude; and the evolution curves of typical microseismic characteristic parameters over time in the stress concentration area, as well as the spatial distribution map of microseismic events, were plotted to analyze the spatiotemporal evolution characteristics of microseismic activity in the stress concentration area.

[0026] The beneficial effects of adopting the above technical solution are as follows: The asymmetric high-stress tunnel rockburst microseismic sensor arrangement method provided by this invention, based on the geological data of the tunnel surrounding rock, and according to the asymmetric original rock stress distribution and tunnel cross-sectional geometric characteristics, performs three-dimensional numerical simulation of the stability of the asymmetric high-stress tunnel, calculates the energy of the asymmetric high-stress tunnel, determines the location of the rockburst risk zone, and fully utilizes the space provided by the tunnel excavation. Microseismic sensors are arranged both in front of and behind the stress concentration zone, ensuring that the high-risk area and its vicinity are always included within the two sets of microseismic sensor arrays arranged in front of and behind the tunnel face. This facilitates the acquisition of micro-fracture signals, ensures the accuracy of microseismic positioning, and lays the foundation for accurate disaster prediction and forecasting. The microseismic sensors work together and are spatially staggered, which is beneficial for the microseismic sensors to receive signals and avoids the influence of microseismic source positioning caused by microseismic sensors being on the same plane. The installation and layout of the microseismic sensors closely follow the stress concentration zone, moving forward and backward while always maintaining a certain distance from the stress zone. This prevents damage to the microseismic sensors and wiring caused by excavation and blasting at the working face, rock mass failure, etc., and ensures the safety of the microseismic monitoring system installation personnel. Attached Figure Description

[0027] Figure 1 A flowchart of a method for arranging microseismic sensors for rockburst in an asymmetric high-stress tunnel according to an embodiment of the present invention;

[0028] Figure 2 This is a diagram showing the arrangement of microseismic monitoring sensors for asymmetric high ground stress tunnels provided in an embodiment of the present invention.

[0029] Figure 3A schematic diagram showing the potential rockburst location on the longitudinal section of an asymmetric high-stress tunnel, provided as an embodiment of the present invention, with the vertical direction of the line connecting the maximum principal stresses.

[0030] Figure 4 Figure 4a is a schematic diagram of the arrangement of microseismic monitoring sensors facing the tunnel face in an embodiment of the present invention. Figure 4b is a schematic diagram of the boreholes arranged facing the front of the stress concentration zone.

[0031] Figure 5 Distribution diagram of high-energy units around an asymmetric high-stress tunnel provided in an embodiment of the present invention;

[0032] Figure 6 A cross-sectional view of the arrangement method of microseismic monitoring sensors behind the tunnel face of an asymmetric high ground stress tunnel provided in an embodiment of the present invention.

[0033] In the diagram: 1. Tunnel; 2. Stress concentration zone; 3. Location of potential rock bursts; 4. Microseismic signal; 5. Unexcavated tunnel; 6. Excavated tunnel. Detailed Implementation

[0034] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0035] Existing microseismic monitoring methods do not consider stress concentration caused by asymmetric high ground stress in deeply buried tunnels. Excavation or other external disturbances can easily trigger rock instability and failure in these areas. This paper proposes a method for arranging microseismic sensors during the construction of asymmetric high ground stress tunnels by determining the location of stress concentration zones after excavation based on the direction of the principal stress within the cross-section and installing microseismic sensors. Specifically, this method studies suitable sensor arrangements to ensure that the sensor array always includes the stress concentration zone and its surrounding rock mass as much as possible, improving the accuracy of microseismic source location and laying the foundation for accurate disaster early warning and assessment. Figure 1 As shown, the method of this embodiment is described below.

[0036] Step S1: Based on the engineering geological conditions and underground structural characteristics of the asymmetric high-stress tunnel, establish a three-dimensional numerical simulation model of the stability of the tunnel group, including the main tunnel, the pilot tunnel, and the cross passages. Combined with monitoring information during construction, determine the location of the stress concentration zone behind the tunnel face. Figure 2 As shown, this area is designated as the key monitoring area for microseismic sensors. The stress concentration zone is located in the surrounding rock of the tunnel behind the working face, perpendicular to the line connecting the maximum principal stresses experienced by the asymmetric high-stress tunnel. Figure 3 As shown.

[0037] Step S2: Perform energy calculations for asymmetric high-stress tunnels to further determine the monitoring area for microseismic sensors, such as... Figure 4 As shown. Rock mass failure is a phenomenon of loss of equilibrium driven by energy. The stability of non-parallel tunnels in hard rock with high ground stress is directly related to the magnitude of the strain energy stored in the rock mass after excavation. If the total strain energy exceeds the ultimate stored energy, the structure may lose equilibrium. Tracing the energy process of a unit, the total energy of the rock mass in the principal stress space can be specifically expressed as:

[0038]

[0039] In the formula: U is the total work done by the principal stress in the direction of the principal strain; σ is the total work done by the principal stress in the direction of the principal strain. i (i = 1, 2, 3) represent the three principal stresses of the rock mass, σ1 is the asymmetric maximum principal stress; σ2 is the intermediate principal stress; σ3 is the minimum principal stress; ε i (i = 1, 2, 3) represent the three principal strains of the rock mass.

[0040] Step S3: Multiple boreholes are drilled from the tunnel wall to the interior of the surrounding rock in the stress concentration zone behind the tunnel face of the asymmetric high-stress tunnel to serve as microseismic monitoring holes. During tunnel blasting construction, if... Figure 2 As shown, a 1-meter section is set 20m in front of the stress concentration zone. # 2 # 3 # 4 # Four boreholes are arranged behind the stress concentration area at the working face. # 6 # 7 # 8 # Four holes.

[0041] Step S4: Install microseismic sensors at different radial depths within the borehole. All microseismic sensors are embedded in the tunnel wall rock mass via borehole embedding. The embedding depth of the microseismic sensors must exceed the relaxation depth of the surrounding rock to facilitate the reception of vibration signals. The borehole depth should be greater than the microseismic sensor placement depth to prevent debris from accumulating at the bottom of the borehole and blocking the installation space for the microseismic sensors. The microseismic source positioning employs a combination of deep and shallow boreholes, arranged alternately, such as... Figure 5 As shown, avoid arranging them on the same plane, which would affect the location of the microseismic source.

[0042] Microseismic sensors are placed at different radial depths in the borehole, a total of four sensors: three unidirectional and one tridirectional. These different types of sensors can work together, which is beneficial for locating the microseismic source. In stress concentration areas, tridirectional sensors are preferentially placed around the corners and inflection points of the tunnel. In other monitoring holes, a basic arrangement of alternating unidirectional and tridirectional sensors can be used. In this embodiment, borehole 1... # 2# 3 # 5 # 6 # 8 # The middle part is a unidirectional velocity sensor, with 4 holes drilled. # 7 # The middle one is a three-dimensional velocity sensor.

[0043] Step S5: Arrange N known microseismic sources (with known three-dimensional coordinates and seismic time) in the tunnel space, analyze the positioning accuracy of the sensor arrangement scheme, and determine the optimal arrangement scheme of the microseismic sensors.

[0044] Assuming that the propagation velocity V of the rock mass P-wave and the arrival error ξ both follow the same normal distribution with respect to the sensor, i.e., V ~ N(u v , σ v ), ξ~N(0, σ t As a result, the time it takes for the sensor to receive the micro-vibration source signal is:

[0045]

[0046] In the formula, t is the time it takes for the sensor to receive the micro-vibration source signal. i The time of origin of the microseismic source is represented by V, the propagation speed of the elastic wave in the medium is represented by ξ, the time error is represented by (x, y, z), the position coordinates of the sensor are represented by (x0, y0, z0), and the position coordinates of the microseismic source are represented by (x0, y0, z0).

[0047] Based on the probability distribution characteristics of P-wave propagation velocity V and arrival error ξ, M (generally greater than 1000) sets of samples (V, ξ) are randomly generated using the Monte Carlo method. Substituting these samples into equation (1) yields the sensor reception time t of a micro-source under the condition of P-wave propagation velocity V.

[0048] Based on the receiving time t, sensor location, and P-wave propagation velocity V of all or some (generally no less than 6) sensors, the microseismic source location (x′, y′, z′) and seismic origin time t′ are derived by using optimization methods (simplex method, genetic algorithm, etc.) with the minimum cumulative time residual as the optimization function.

[0049] Formula (3) is used to determine the microseismic source positioning error. S represents the expected value of the positioning error. The smaller S is, the smaller the positioning error and the better the positioning effect.

[0050]

[0051] The expected value of the positioning error of the same microseismic source under M samples (V, ξ) is used as the positioning accuracy of the microseismic monitoring scheme for that microseismic source. The expected value of the positioning accuracy of all microseismic sources is used as the evaluation index of the merits of the microseismic monitoring scheme, and the optimal monitoring scheme is determined accordingly.

[0052] When the microseismic source positioning accuracy reaches the set threshold, the arrangement scheme of the microseismic sensor is determined, and grout is injected into the borehole to fix the microseismic sensor to the rock mass.

[0053] If the seismic source positioning accuracy does not reach the set threshold, the borehole position is fine-tuned and the microseismic sensor is repositioned until the positioning accuracy reaches the set threshold.

[0054] Step S6: As the original stress concentration zone is reinforced and the risk of rockburst decreases, the installation and layout of the microseismic sensors always move in accordance with the changes in the stress concentration zone and maintain a certain distance from the stress concentration zone. Determine the next stress concentration zone according to Steps 1 and 2, and rearrange the microseismic sensors according to Steps 3 to 5 until the tunnel excavation is completed. This prevents rock mass failure from damaging the microseismic sensors and wiring, and ensures the safety of the microseismic monitoring system installation personnel.

[0055] Step S7: During tunnel construction, a local area network (LAN) is established between the tunnel's microseismic monitoring center and the external microseismic monitoring project team, utilizing the existing communication network. This allows monitoring personnel to promptly collect and analyze microseismic activity at different depths within the stress concentration zone behind the tunnel face, and to provide timely feedback on rockburst risk based on the monitoring results. Dedicated data processing software is used to calculate the source parameters of each microseismic event, including microseismic release energy, apparent volume, seismic moment, and moment magnitude. Evolution curves of typical microseismic characteristic parameters (number of events and microseismic release energy) over time within the stress concentration zone are plotted, along with a spatial distribution map of microseismic events, to analyze the spatiotemporal evolution characteristics of microseismic activity within the stress concentration zone.

[0056] To date, there have been no reports on the arrangement of microseismic monitoring sensors for non-confrontational high-stress tunnels. A reasonable arrangement of microseismic sensors can not only monitor more microseismic signals over a wider area, but also enable the positioning algorithm to quickly and accurately determine the location of the seismic source and the time of occurrence, which is beneficial for risk warning assessment of stress concentration areas in tunnels.

[0057] To address the aforementioned problems and considering the characteristics of non-aligned high-stress tunnel engineering, this invention proposes a suitable sensor distribution method for non-aligned high-stress tunnels. 1) It fully utilizes the space provided by the tunnel excavation, deploying microseismic sensors both in front of and behind the stress concentration area. This ensures that the high-risk stress concentration area and its vicinity are always included within the two sets of microseismic sensor arrays deployed before and after the stress concentration area, facilitating the acquisition of micro-fracture signals, ensuring the accuracy of microseismic positioning, and laying the foundation for accurate disaster prediction and forecasting. 2) Different types of microseismic sensors work collaboratively and are spatially staggered, which is beneficial for signal reception and avoids the influence of microseismic source positioning caused by sensors being on the same plane. 3) The installation and arrangement of microseismic sensors closely follows the tunnel face, moving forward and backward while always maintaining a certain distance from the stress concentration area. This prevents damage to the microseismic sensors and wiring caused by tunnel face excavation blasting, rock mass failure, etc., and ensures the safety of the microseismic monitoring system installation personnel.

[0058] Example 1

[0059] A tunnel project comprises a main tunnel and a pilot tunnel, spaced 28m apart. The main tunnel has an elliptical cross-section, while the pilot tunnel has a horseshoe-shaped cross-section. The full-face drill-and-blast method was used for excavation. The relaxation depth of the surrounding rock was within 1.5m. A three-dimensional numerical simulation model of the stability of the tunnel's main tunnel, pilot tunnel, and cross passages was established. Based on monitoring information during construction, the location of the stress concentration zone behind the tunnel face under asymmetric high ground stress was determined and identified as the key area for microseismic sensor monitoring. Considering the probability distribution characteristics of the longitudinal wave propagation velocity and the probability distribution characteristics of the arrival error, the expected positioning error values ​​for various preliminary schemes were calculated using the Monte Carlo stochastic simulation method. Based on this, the positioning accuracy of each scheme was evaluated, and the optimal sensor layout scheme was finally determined. The corresponding sensors were then embedded in the monitoring boreholes. The microseismic sensor layout method is as follows:

[0060] 1) The maximum monitoring range of the microseismic sensors in the monitored tunnel rock mass is 150m. The first group of microseismic sensors is positioned behind the stress concentration zone at the tunnel face. Three of these sensors are unidirectional, and the other is a triaxial sensor. Their natural frequency is 14Hz, and their response range is 7–2000Hz. Different types of sensors can work together, which is beneficial for microseismic source localization. The microseismic sensors are all installed by drilling into the tunnel wall rock mass. Grouting is injected into the boreholes to fix the sensors to the rock mass. The installation depth is 2-3m, exceeding the surrounding rock relaxation depth, which is beneficial for the sensors to receive vibration signals. The borehole depth is greater than the sensor installation depth to prevent debris from accumulating at the bottom of the borehole and blocking the sensor installation space. Microseismic sensors on the same cross-section are staggered by 2m along the tunnel axis to avoid being placed on the same plane and affecting microseismic source localization.

[0061] 2) The second set of microseismic sensors in front of the stress concentration zone of the tunnel face is arranged in the same way as above.

[0062] 3) When the stress concentration zone in the monitoring area is reinforced with secondary support, reducing the risk of rockburst, the first and second sets of microseismic sensors are moved 20m behind and 20m in front of the next stress concentration zone, respectively, while maintaining the same installation method. The installation arrangement of the microseismic sensors always closely follows the movement of the stress concentration zone and maintains a certain distance from it, avoiding damage to the microseismic sensors and wiring caused by rock mass failure, and ensuring the safety of the microseismic monitoring system installation personnel. Stability monitoring was conducted during tunnel excavation, and a series of monitoring data were collected.

[0063] 4) As the stress concentration zone 2 in the tunnel changes, repeat the above steps until the tunnel excavation is completed.

[0064] In this embodiment, triaxial sensors are preferentially arranged at the corners, turning points, or around key monitoring areas of the tunnel, while uniaxial and triaxial sensors can be arranged alternately in the remaining monitoring holes.

[0065] The test results were analyzed and processed promptly. The test results from September 2nd to September 3rd, 2022 are as follows: Figure 6 As shown. Figure 6 This is a spatial distribution map of microseismic signal 4 monitored during excavation from September 2nd to 3rd, 2022. The spheres represent microseismic signal 4, and the size of the spheres represents the energy released by the microfractures; the larger the sphere, the greater the energy. During this period, two sets of microseismic sensors, placed before and after the stress concentration zone, jointly monitored microseismic signal 4 generated within the surrounding rock of the stress concentration zone. Figure 6 It can be seen that the microseismic signal 4 is concentrated near the stress concentration zone, which is consistent with the stress concentration characteristics of deeply buried hard rock tunnels, indicating that stress concentration zone 2 has a high risk of rockburst. On September 4, 2022, a minor rockburst occurred at the stress concentration zone where the microseismic signal was concentrated, which is consistent with the monitoring results, indicating the accuracy of the microseismic signal monitoring. This invention makes full use of the space provided by the excavated tunnel, and always includes the stress concentration zone 4 with a high risk of damage and its surrounding area within the two sets of microseismic sensor arrays arranged before and after the stress concentration zone. This is beneficial for the acquisition of micro-fracture signal 4, ensures the accuracy of microseismic source positioning, and effectively captures the microseismic signal 4, which is a precursor to the damage of the high-risk stress concentration zone 2.

[0066] During the stability monitoring of the asymmetric high-stress tunnel using the technical solution of this invention, 18 precursor microseismic signals of rockbursts were captured in 21 instances of minor or higher-level rockbursts in the stress concentration area and nearby tunnel sections. This accurately predicted the risks associated with asymmetric high-stress tunnel excavation. After implementing the technical solution of this invention, no casualties were reported among construction workers during the on-site excavation of the asymmetric high-stress tunnel, ensuring construction safety.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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 or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the claims of the present invention.

Claims

1. A method for arranging microseismic sensors for rockburst in asymmetric high-stress tunnels, characterized in that: Includes the following steps: Step S1: Based on the geological data of the surrounding rock of the tunnel, and according to the asymmetric original rock stress distribution and the geometric characteristics of the tunnel cross section, a three-dimensional numerical simulation of the stability of the asymmetric high stress tunnel is carried out, and the energy of the asymmetric high stress tunnel is calculated. Combined with the construction information, the location of the stress concentration zone behind the tunnel face of the asymmetric high stress tunnel is determined. Step S2: In the stress concentration zone behind the tunnel face of the asymmetric high-stress tunnel, multiple boreholes are set from the tunnel wall to the interior of the surrounding rock as microseismic monitoring holes. The microseismic monitoring holes are arranged in a staggered manner in space. Step S3: Install microseismic sensors in different radial depth areas of the borehole. The microseismic sensors are all installed in the rock mass inside the tunnel wall by being embedded in the borehole. The embedment depth of the microseismic sensors must exceed the relaxation depth of the surrounding rock. The borehole depth must be greater than the placement depth of the microseismic sensors. Step S4: Arrange N known microseismic sources in the tunnel space. The three-dimensional coordinates and occurrence time of the known microseismic sources are known. Analyze the positioning accuracy of the sensor arrangement scheme in Step S3. When the positioning accuracy of the microseismic sources reaches the set threshold, determine the arrangement scheme of the microseismic sensors and inject grout into the borehole to fix the microseismic sensors to the rock mass. If the positioning accuracy of the seismic sources does not reach the set threshold, fine-tune the borehole position and reposition the microseismic sensors until the positioning accuracy reaches the set threshold. Step S5: When the stress concentration area is supported by secondary support, the regional microseismic energy and activity gradually decrease. Determine the next stress concentration area according to step S1, and rearrange the microseismic sensors according to steps S2 to S4 until the tunnel excavation is completed. Step S6: During tunnel construction, a local area network is established between the microseismic monitoring center inside the tunnel and the microseismic monitoring project department outside the tunnel through the existing communication network. This allows monitoring personnel to collect and store microseismic activity at different depths within the stress concentration zone behind the tunnel face in a timely manner and analyze it. Based on the monitoring results, feedback on rockburst risk is provided in a timely manner.

2. The method for arranging microseismic sensors for rockburst in asymmetric high-stress tunnels according to claim 1, characterized in that: In step S1, the specific method for calculating the energy of the asymmetric high-stress tunnel is as follows: The total energy of the principal stress space rock mass, tracing the energy process of a unit, is specifically expressed as follows: Where U is the total work done by the principal stress in the direction of the principal strain; σ i The three principal stresses of the rock mass are ε. i The three principal strains of the rock mass are i = 1, 2, and 3.

3. The method for arranging microseismic sensors for rockburst in asymmetric high-stress tunnels according to claim 1, characterized in that: The stress concentration zone is located in the surrounding rock of the tunnel behind the working face, perpendicular to the line connecting the maximum principal stresses of the asymmetric high-stress tunnel.

4. The method for arranging microseismic sensors for rockburst in asymmetric high-stress tunnels according to claim 1, characterized in that: Two monitoring sections are used before and after the stress concentration zone. Four microseismic sensors are arranged in each monitoring section. The first row of microseismic sensors is 20m in front of the stress concentration zone, and the second row of microseismic sensors is 20m behind the stress concentration zone. Each microseismic sensor requires a hole to be drilled each time it is installed. The hole depth is 2-4m and the hole diameter is 75mm.

5. The method for arranging microseismic sensors for rockburst in asymmetric high-stress tunnels according to claim 4, characterized in that: Microseismic sensors are installed at three locations: the surface, the surface inward, and the deep layer, to receive information on rock fractures at different radial depths within the surrounding rock.

6. The method for arranging microseismic sensors for rockburst in asymmetric high-stress tunnels according to claim 1, characterized in that: The microseismic sensor uses a combination of unidirectional and tridirectional velocity sensors to work together, with a measurement range of 7–2000 Hz, to collect information on rock fractures inside the surrounding rock.

7. The method for arranging microseismic sensors for rockburst in asymmetric high-stress tunnels according to claim 6, characterized in that: In stress concentration areas, triaxial velocity sensors are preferentially deployed around the corners and inflection points of the tunnel, while uniaxial and triaxial velocity sensors are alternately deployed in the remaining microseismic monitoring holes.

8. The method for arranging microseismic sensors for rockburst in asymmetric high-stress tunnels according to claim 1, characterized in that: Using specialized data processing software, the source parameters of each microseismic event are calculated, including microseismic release energy, apparent volume, seismic moment, and moment magnitude. The evolution curves of typical microseismic characteristic parameters over time in the stress concentration area, as well as the spatial distribution map of microseismic events, were plotted to analyze the spatiotemporal evolution characteristics of microseismic activity in the stress concentration area.

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