Method for measuring stress change of surrounding rock during TBM (Tunnel Boring Machine) tunneling

Abstract

The invention relates to the technical field of surrounding rock stress change measurement, in particular to a method for measuring surrounding rock stress change during TBM tunneling. According to the technical scheme, the method comprises the following steps that stress sensors are arranged, specifically, a plurality of stress sensors are arranged in surrounding rock in front of a TBM cutterhead and surrounding rock on the periphery of a TBM body, and the stress sensors are evenly distributed in circular measurement areas with different radiuses in a polar coordinate system with the center of the TBM cutterhead as the original point; the stress sensors are reasonably arranged, various data transmission and processing technologies are adopted, visual result display and early warning are achieved, and the surrounding rock stress change during TBM tunneling is comprehensively and accurately measured. Complex geological environments and construction conditions can be effectively handled, guarantee is provided for construction safety, tunneling parameters are optimized, and engineering management efficiency and scientificity are improved.

Description

Technical Field

[0001] The invention relates to the technical field of surrounding rock stress change measurement, and in particular to a method for measuring surrounding rock stress change during TBM excavation. Background Art

[0002] With the continuous development of underground engineering construction, full-face rock tunnel boring machines (TBMs) have been widely used in tunnel construction due to their high efficiency and safety. However, the TBM excavation process will have a significant impact on the stress state of the surrounding rock, and the change in surrounding rock stress is directly related to the stability of the tunnel and construction safety. Accurately measuring the change in surrounding rock stress during TBM excavation is of vital importance for timely understanding the stability of the surrounding rock, optimizing excavation parameters, and taking reasonable support measures.

[0003] Traditional methods for measuring surrounding rock stress have many limitations. For example, some contact measurement methods require drilling holes in the surrounding rock to install sensors, which not only causes certain disturbances to the surrounding rock and affects the accuracy of the measurement, but also makes the installation and maintenance of sensors difficult in the complex environment of TBM excavation. In addition, traditional methods can often only obtain stress data at discrete points, and it is difficult to fully and accurately reflect the overall distribution and changes of surrounding rock stress. At the same time, there are strong adverse factors such as electromagnetic interference and vibration at the TBM excavation site, which also puts high demands on the stability and reliability of data transmission. The existing measurement technology has shortcomings in dealing with these problems, and it is difficult to meet the needs of real-time, accurate and comprehensive monitoring of surrounding rock stress changes during TBM excavation. Therefore, an innovative and more effective measurement method is needed to solve these problems.

[0004] In summary, the present application proposes a method for measuring surrounding rock stress changes during TBM excavation. Summary of the invention

[0005] The purpose of the present invention is to address the problem in the background technology that it is difficult to meet the demand for real-time, accurate and comprehensive monitoring of surrounding rock stress changes during TBM excavation, and to propose a method for measuring surrounding rock stress changes during TBM excavation.

[0006] The technical solution of the present invention is a method for measuring the stress change of surrounding rock during TBM excavation, comprising the following steps:

[0007] Arrange stress sensors: multiple stress sensors are arranged in the surrounding rock in front of the TBM cutterhead and in the surrounding rock around the TBM body. The stress sensors are evenly distributed on circular measurement areas of different radii in a polar coordinate system with the center of the TBM cutterhead as the origin, and the stress sensors on adjacent circular measurement areas are staggered in the circumferential direction; in the surrounding rock around the TBM body, annular measurement belts are arranged at regular intervals along the axial direction of the body, and stress sensors are evenly distributed on each annular measurement belt, and the stress sensors on adjacent annular measurement belts are staggered in both the axial and circumferential directions;

[0008] Data collection: During the TBM excavation process, the stress sensor collects surrounding rock stress data in real time;

[0009] Data transmission: The stress data collected by the stress sensor is transmitted to the data processing unit. The transmission methods include wireless transmission and wired transmission. For sensors close to the TBM body, wired transmission is used, and data transmission is carried out through shielded cables to resist electromagnetic interference; for sensors far away, wireless transmission is used, and data transmission is carried out using Bluetooth or ZigBee wireless communication technology, and automatic frequency hopping and error correction functions are provided to ensure stable and reliable data transmission;

[0010] Data processing:

[0011] The collected raw stress data is filtered to remove noise interference. The median filter algorithm is used. The formula is:

[0012] y n =median{x n-k ,x n-k+1 ,…,x n+k-1 ,x n+k}

[0013] Among them, x n is the nth data point in the original stress data sequence, y n is the data point after filtering, k is the half width of the filtering window;

[0014] According to the position coordinates of the stress sensor in the surrounding rock, the filtered data is spatially interpolated to obtain the continuous distribution field of the surrounding rock stress. The Kriging interpolation algorithm is used, and the formula is:

[0015]

[0016] Where Z * (x0) is the estimated value at the interpolation point x0, z(x i ) is a known point x i The measured value at i is the weight coefficient of the i-th known point, by solving the Kriging equations:

[0017]

[0018] We get, where γ(x i ,x j ) is a known point x i and x j The semivariogram function between them, u is the Lagrange multiplier.

[0019] The surrounding rock stress distribution field at different times is compared and analyzed, and the change amount and change rate of surrounding rock stress are calculated. The formulas are:

[0020] Δσ(x,y,t)=σ(x,y,t2)-σ(x,y,t1) and

[0021] Wherein, Δσ(x,y,t) is the stress change at the position (x,y) at time t, σ(x,y,t1) and σ(x,y,t2) are the stress values ​​at the position (x,y) at time t1 and t2 respectively, and vΔσ(x,y,t) is the stress change rate at the position (x,y) at time t;

[0022] Result display and early warning: The processed surrounding rock stress distribution field, stress change and change rate information are visualized through the display unit, and the display methods include two-dimensional contour map, color cloud map or three-dimensional graph; when the surrounding rock stress change or change rate exceeds the preset threshold, an audible and visual alarm signal is automatically issued to remind the operator to pay attention to the surrounding rock stability. The threshold can be set and adjusted according to different geological conditions and engineering requirements.

[0023] Optionally, before arranging the stress sensors, the method further includes conducting geological survey and analysis on the measurement area, determining the arrangement plan of the stress sensors according to the geological conditions, and appropriately increasing the number and density of stress sensors in areas with poor geological conditions such as fractured zones and soft rock areas.

[0024] Optionally, the method further includes a step of verifying the accuracy of the measurement method, which is as follows:

[0025] Before TBM excavation, in addition to installing stress sensors, several high-precision strain gauges are arranged as reference measurement points in the selected measurement area. The measurement accuracy of the strain gauges is higher than that of the stress sensors, and their installation positions should be adjacent to or close to the stress sensors.

[0026] During the TBM excavation process, stress sensors and strain gauges simultaneously measure the surrounding rock stress and record the data collected separately.

[0027] After the excavation is completed, the stress data measured by the stress sensor is compared with the stress data measured by the strain gauge, and the relative error between the two is calculated. The formula is:

[0028]

[0029] Among them, δ is the relative error, σ s is the measured value of the stress sensor, σ c is the strain gauge measurement value;

[0030] The accuracy of the measurement method is judged according to the size of the relative error. If the relative error is within the allowable range, the measurement method is considered accurate and reliable. If the relative error exceeds the allowable range, the measurement system needs to be checked and optimized, and the accuracy needs to be re-verified until the requirements are met. The allowable range is determined based on the actual engineering needs and relevant standards.

[0031] Optionally, the method further includes measures for improving the adaptability of the measurement system, specifically including:

[0032] When TBM excavation encounters different geological conditions, the arrangement density and position of stress sensors are adjusted according to the geological conditions, and different arrangement strategies are adopted in different geological areas such as soft rock, hard rock and broken zone;

[0033] For the data transmission module, wireless transmission or wired transmission mode, or a hybrid transmission mode combining the two can be flexibly selected according to the electromagnetic environment and communication distance of the TBM excavation site;

[0034] The algorithm parameters in the data processing module are adaptively adjusted according to different geological conditions and engineering requirements, including appropriately reducing the filter window size in the filter algorithm in soft rock areas and appropriately increasing the search radius in the interpolation algorithm in hard rock areas;

[0035] The display interface and alarm threshold of the display unit are personalized according to the operator's habits and actual engineering conditions.

[0036] Optionally, the stress sensor uses a piezoresistive strain gauge as a sensing element, the piezoresistive strain gauge is adhered to the surface of an elastic substrate with high strength and high elastic modulus, and is wrapped on the outside with a protective shell with good sealing and pressure resistance, and the protective shell is provided with a force transmission structure that is in close contact with the surrounding rock.

[0037] Optionally, the display unit displays information including surrounding rock stress-related information, tunneling speed, cutter head rotation speed, and displays the information in association with surrounding rock stress changes.

[0038] Optionally, when data is transmitted, the transmitted data is encrypted.

[0039] Optionally, the measurement system is regularly maintained and calibrated, including checking the working status of the stress sensor and calibrating the accuracy of the data acquisition equipment. The maintenance and calibration cycle is determined according to the working intensity and environmental conditions of the TBM excavation.

[0040] Optionally, the measured surrounding rock stress data are stored and recorded, and a database is established to further analyze and study the data. The analysis and research include analyzing the laws of surrounding rock stress changes under different geological conditions and evaluating the long-term impact of TBM excavation on surrounding rock stability. The database includes data query and statistical analysis.

[0041] Optionally, during the TBM excavation process, if special geological conditions or abnormal stress changes are encountered, the excavation operation is suspended, and detailed geological surveys and stress analysis of the surrounding rock are carried out. According to the analysis results, the measurement plan is adjusted or corresponding engineering measures are taken to adjust the measurement plan, further optimize the layout of stress sensors and adjust the data processing algorithm.

[0042] Compared with the prior art, the present invention has at least one of the following beneficial technical effects:

[0043] By properly arranging stress sensors in the surrounding rock in front of the TBM cutterhead and around the machine body, the key areas can be fully covered and rich stress data can be obtained. The circular measurement area and the annular measurement belt around the machine body are arranged in a polar coordinate system, combined with the staggered distribution of sensors, the spatial distribution characteristics of the surrounding rock stress can be captured more accurately, avoiding monitoring blind spots, and providing a basis for accurately analyzing the changes in surrounding rock stress.

[0044] The data transmission module adopts a combination of wireless and wired methods, which can be flexibly selected according to different situations. It not only ensures the stability of long-distance transmission, but also effectively resists electromagnetic interference near the fuselage. The median filtering algorithm is used to remove noise in data processing, and the Kriging interpolation algorithm is used to obtain the continuous stress distribution field, as well as accurately calculate the stress change amount and change rate, which improves the accuracy and reliability of the data and provides strong support for subsequent analysis and decision-making.

[0045] The display unit intuitively displays the surrounding rock stress distribution field in two-dimensional or three-dimensional graphics, and displays numerical information such as stress change and change rate in real time, so that operators can understand the surrounding rock stress state at a glance. When the stress change exceeds the threshold, the sound and light alarm function can promptly remind operators to pay attention to the surrounding rock stability problem so that they can take corresponding measures to effectively prevent accidents and ensure construction safety.

[0046] The accuracy verification method ensures the reliability and accuracy of the measurement method by comparing it with a high-precision strain gauge, providing confidence for engineering applications. Adaptability improvement measures can flexibly adjust sensor layout, data transmission methods, and algorithm parameters according to different geological conditions (such as soft rock, hard rock, and broken zone), so that the measurement system can better adapt to the complex and changing geological environment and improve measurement accuracy and monitoring capabilities of surrounding rock stability.

[0047] The linkage between the measurement system and the TBM excavation control system realizes automatic adjustment of excavation parameters according to changes in surrounding rock stress, achieves dynamic balance and adaptive control of TBM excavation and surrounding rock stress changes, optimizes the excavation process, and reduces disturbance to the surrounding rock.

[0048] The present invention can comprehensively and accurately measure the stress changes of surrounding rocks during TBM excavation by rationally arranging stress sensors, adopting a variety of data transmission and processing technologies, and realizing intuitive result display and early warning, etc. It can effectively cope with complex geological environments and construction conditions, provide guarantees for construction safety, optimize excavation parameters, and improve the efficiency and scientificity of engineering management. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 The figure is a flow chart of a method for measuring the stress change of surrounding rock during TBM excavation. DETAILED DESCRIPTION

[0050] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0051] Example

[0052] like Figure 1 As shown, the present invention proposes a method for measuring the stress change of surrounding rock during TBM excavation, which includes the construction and preparation of the measurement system, the implementation steps of the measurement method and the accuracy verification of the measurement method. The present invention is described in detail in three parts.

[0053] 1. Construction and preparation of measurement system

[0054] Selection and Installation of Strain Sensors

[0055] Selection of stress sensor: High-precision piezoresistive strain gauges are used as sensing elements, which have good sensitivity and stability. The elastic matrix is ​​made of high-strength, high-elastic modulus metal materials, such as aluminum alloy, to ensure that the surrounding rock stress can be effectively transmitted to the strain gauge. The protective shell is made of stainless steel, which has good sealing and pressure resistance.

[0056] Installation location determination:

[0057] In front of the TBM cutterhead, a polar coordinate system is established with the cutterhead center as the origin. Set up multiple circular measurement areas with different radii, such as 1m, 2m, and 3m (which can be adjusted according to the actual TBM size and geological conditions). At least three stress sensors are evenly distributed on each circular measurement area, and the sensors on adjacent circular measurement areas are staggered in the circumferential direction. A sensor is arranged every 120° on a circle with a radius of 1m, and a sensor is arranged every 120° at the corresponding position on a circle with a radius of 2m, but the position is staggered by 30° from the sensor with a radius of 1m, and so on.

[0058] Around the TBM fuselage, an annular measurement belt is set every 0.5m (adjustable according to actual conditions) along the axial direction of the fuselage. At least four stress sensors are evenly distributed on each annular measurement belt, and the sensors on adjacent annular measurement belts are staggered in the axial and circumferential directions. For example, a sensor is arranged every 90° on the first annular measurement belt, and a sensor is arranged every 90° at the corresponding position on the second annular measurement belt, but offset by 0.25m in the axial direction, so as to ensure comprehensive and uniform stress monitoring.

[0059] Sensor installation steps:

[0060] At the selected installation location, first use drilling equipment to drill a hole of appropriate size and depth in the surrounding rock. Insert the elastic matrix of the sensor into the hole to ensure that it is in close contact with the surrounding rock. Then paste the piezoresistive strain gauge on the surface of the elastic matrix, paying attention to the flatness and firmness of the paste to ensure that the strain gauge can accurately sense stress changes. After the paste is completed, put a protective shell on the outside of the sensor, and use materials such as sealant to ensure the sealing of the shell. The force transmission structure on the protective shell fits closely with the surrounding rock, such as using a serrated or raised design to increase the friction and contact area with the surrounding rock, ensuring that the surrounding rock stress can be accurately transmitted to the elastic matrix.

[0061] Data transfer module settings

[0062] Wireless transmission unit configuration: Select a transmission module with Bluetooth or ZigBee wireless communication technology. For Bluetooth transmission, set the appropriate communication frequency and transmission power. The general communication frequency is 2.4GHz. The transmission power can be adjusted according to the distance and obstacles at the TBM excavation site. It can be set to medium power in the absence of obstructions. If there are many obstacles, the power can be appropriately increased. At the same time, turn on the automatic frequency hopping and error correction functions. The automatic frequency hopping range can be set to multiple channels within the 2.4GHz frequency band to avoid interference with other wireless devices. The error correction function uses technologies such as forward error correction coding to ensure the accuracy of data transmission.

[0063] Wired transmission unit wiring: For stress sensors that are close to the TBM body, shielded cables are used for data transmission. The cables are laid along the preset cable ducts of the TBM body to avoid crossing with other electrical equipment to reduce electromagnetic interference. At the connection of the cable, waterproof and dustproof connectors are used for connection, and the connection is ensured to be firm to prevent the connector from loosening due to vibration and other reasons during the TBM excavation process.

[0064] Connection between the data transmission module and the stress sensor: Install the receiver of the wireless transmission unit at a suitable position on the TBM body to ensure that it can stably receive the signal from the stress sensor. For sensors with wireless transmission, pair and set them with the corresponding wireless transmission module during installation. For sensors with wired transmission, connect them to the input port of the data transmission module via a cable. When connecting, pay attention to the correct connection of the positive and negative poles to avoid reverse connection, which may cause data transmission errors or sensor damage.

[0065] Configuration of data processing module

[0066] Hardware selection: Choose a high-performance microprocessor or industrial computer as the core component for data processing. The hardware should have sufficient computing speed and storage capacity to meet the needs of real-time data processing and storage. For example, choose an industrial computer with a main frequency of more than 2GHz and a memory of more than 8GB.

[0067] Software programming: Develop specialized data processing software to implement median filtering algorithm, Kriging interpolation algorithm, and calculation functions of stress change and change rate. In the software, set the initial value of the filter window half width k to 3 (which can be adjusted according to the actual data situation). For the calculation of the semivariance function and weight coefficient in the Kriging interpolation algorithm, program it according to the principles and methods of geostatistics. At the same time, the software should have a data receiving interface that can communicate stably with the data transmission module and receive data collected by the stress sensor.

[0068] Installation and debugging of display module

[0069] Screen selection and installation: Use a high-definition LCD screen. The size is determined according to the space in the TBM control room and the observation needs of the operator. Generally, a 15-inch to 20-inch screen can be selected. Install the screen in the TBM control room in a position that is convenient for the operator to observe. Fix it with a bracket or wall mount to ensure that it is firmly and stably installed and will not loosen or shift due to vibration during the TBM excavation process.

[0070] Display drive circuit connection and debugging: Connect the display drive circuit to the display screen and data processing module. After the connection is completed, debug to ensure that the display screen can normally display the surrounding rock stress distribution field, stress change and change rate output by the data processing module. During the debugging process, check the display clarity, brightness, contrast and other parameters, and adjust them to a suitable state so that the operator can clearly and intuitively observe the display content. At the same time, set the layout of the display interface, reasonably divide the display areas such as two-dimensional contour maps, color cloud maps or three-dimensional graphics, and display the relevant numerical information and alarm prompt information in a prominent position.

[0071] Power module settings

[0072] Selection and installation of rechargeable battery packs: Use large-capacity lithium-ion battery packs as power sources, which have the advantages of high energy density and good charging and discharging performance. Determine the capacity and voltage of the battery pack according to the power consumption requirements of each module of the measurement system and the time requirements of the TBM excavation operation. For example, a lithium-ion battery pack with a total voltage of 24V and a capacity of 50Ah can meet the continuous operation of the measurement system for more than 8 hours (adjustable according to actual conditions). Install the battery pack in a dedicated battery compartment on the TBM body, and take measures such as shock absorption, waterproofing, and dustproofing to protect it, to ensure that it can work normally in harsh excavation environments.

[0073] Charging management circuit setting: Install an intelligent charging management circuit to monitor and manage the charging process of the battery pack. Set the charging voltage to 28.8V (determined according to the characteristics of the lithium-ion battery pack), and the charging current can be adjusted according to the capacity of the battery pack and the charging time requirements, generally set to 5A to 10A. The charging management circuit should have functions such as overcharge protection, over-discharge protection, and short-circuit protection. When the battery pack has an abnormal situation, it can cut off the charging or discharging circuit in time to protect the safety and service life of the battery pack.

[0074] Power supply voltage stabilization circuit configuration: A power supply voltage stabilization circuit is configured at the output end of the power module to stabilize the voltage output by the battery pack within the operating voltage range required by each module. For example, a stable DC voltage of 5V is provided for the data processing module and the display module; for the stress sensor and the data transmission module, a stable voltage such as 3.3V or 12V is provided according to their specific requirements. The power supply voltage stabilization circuit is designed with a linear voltage stabilization chip or a switching voltage stabilization chip to ensure that the stability of the output voltage and the ripple factor meet the working requirements of each module.

[0075] 2. Implementation steps of the measurement method

[0076] System debugging and calibration before tunneling

[0077] System connection check: Before TBM excavation, carefully check whether the connection between the stress sensor, data transmission module, data processing module, display module and power module is correct and firm. Check whether the cable is damaged, whether the joint is loose, whether the signal of the wireless transmission module is normal, etc. Perform a power-on test on the entire measurement system to ensure that each module can start and work normally.

[0078] Sensor calibration: Use a standard pressure source to calibrate the stress sensor. Apply the standard pressure source to the sensor, gradually increase the pressure according to a certain pressure gradient (such as 0MPa, 5MPa, 10MPa, 15MPa, etc.), and record the output data of the sensor. According to the calibration curve of the sensor, compare the difference between the actual output data and the theoretical value, adjust the calibration coefficient of the sensor to ensure that the measurement accuracy of the sensor is within the allowable range. For example, for a sensor with a measurement accuracy requirement of ±0.5% FS (full scale), during the calibration process, ensure that the measurement error at each pressure point does not exceed the accuracy requirement.

[0079] Data transmission test: Test the stability and reliability of the data transmission module by simulating the sending and receiving of stress data. Send simulated stress data at the stress sensor end to observe whether the data processing module can receive the data accurately and timely, and check whether there are any losses or errors during the data transmission process. At the same time, test the distance and stability of wireless transmission, and test the wireless signal strength at different locations of the TBM excavation site (including in front of the cutterhead, around the body, etc.) to ensure that wireless transmission can work normally within the entire excavation range.

[0080] Display module function test: Input simulated surrounding rock stress data into the data processing module and observe whether the display module can correctly display information such as stress distribution field, stress change amount and change rate. Check whether the graphic display of the display interface is clear and accurate, whether the numerical display is normal, and whether the alarm function can be triggered normally. Adjust the color setting and font size of the display module to make it conform to the operator's observation habits and engineering requirements.

[0081] Threshold setting: According to the geological conditions and design requirements of the project, as well as relevant engineering experience and specifications, set the alarm thresholds for the change amount and change rate of surrounding rock stress. For example, for general rock tunnel projects, when the change amount of surrounding rock stress exceeds 5MPa or the stress change rate exceeds 1MPa / h, an alarm signal is issued. However, in projects with complex geological conditions or special conditions, the threshold can be adjusted appropriately according to the actual situation. The setting of the threshold should be tested and verified multiple times during the system debugging process to ensure its rationality and effectiveness.

[0082] Data collection and transmission during tunneling

[0083] Stress data acquisition: During the TBM excavation process, the stress sensor senses the changes in surrounding rock stress in real time and converts it into electrical signals. The resistance value of the piezoresistive strain gauge changes with the changes in surrounding rock stress, and the change in resistance value is converted into a change in voltage or current signal through the measurement circuit. The signal conditioning circuit inside the sensor amplifies and filters these signals and outputs them as standard analog signals (such as 0-5V or 4-20mA) for collection by the data transmission module.

[0084] Data transmission:

[0085] Wireless transmission: For stress sensors that are far away from the TBM body, the data collected is sent to the receiver on the TBM body through the wireless transmission unit. The sensor sends the data at a preset time interval (for example, once per second). After receiving the data, the wireless transmission module performs data verification and error correction to ensure the integrity of the data. The data is then transmitted to the data processing module through a serial port or USB interface.

[0086] Wired transmission: For stress sensors that are close to the TBM body, their data is directly transmitted to the data processing module through shielded cables. During the transmission process, the shielded cable effectively resists the electromagnetic interference at the TBM excavation site, ensuring the accuracy of the data. The data processing module receives the wired data in real time through its input port, and performs corresponding processing and storage.

[0087] Data processing and analysis

[0088] Filtering: After the data processing module receives the raw stress data collected by the stress sensor, it first performs median filtering. Taking the filter window half width k=3 as an example, for each data point, take the 3 data points before and after it (7 data points in total), sort these 7 data points, and then take the middle value as the filtered data point. This can effectively remove the noise interference in the data and retain the true trend of the data. For example, for a set of original stress data sequence [10.2, 10.5, 9.8, 10.1, 10.3, 10.0, 9.9, 10.4, 10.2], when filtering the middle data point 10.1, take the 3 data points before and after it (i.e. [9.8, 10.5, 10.1, 10.3, 10.0, 9.9, 10.4]), and after sorting, it is [9.8, 9.9, 10.0, 10.1, 10.3, 10.4, 10.5], and take the middle value 10.1 as the filtered data point. By performing such processing on the entire data sequence, the filtered stress data sequence is obtained.

[0089] Interpolation processing: After filtering, the data is spatially interpolated according to the position coordinates of the stress sensor in the surrounding rock. The Kriging interpolation algorithm is used to first calculate the semivariogram function γ(x i ,x j ). For example, for two known points with position coordinates (x1,x1) and (x2,x2), based on their stress measurements Z(x1) and Z(x2), and the distance between them:

[0090]

[0091] The semivariance value is calculated through the semivariance function model (such as Gaussian model, exponential model, etc.). Then, the Kriging equation system is solved

[0092]

[0093] Get the weight coefficient λ i and Lagrange multiplier μ. Where n is the number of known points, x0 is the position coordinate of the point to be interpolated. Finally, according to the formula

[0094]

[0095] Calculate the stress estimate Z at the interpolation point x0 * (x0), thus obtaining the continuous distribution field of surrounding rock stress.

[0096] Calculation of stress change and change rate: Compare and analyze the surrounding rock stress distribution field at different times, and calculate the stress change and change rate. Assume that the surrounding rock stress distribution field at time t1 is σ(x,y,t1), and the surrounding rock stress distribution field at time t2 is σ(x,y,t2), then the stress change at position (x,y) is Δσ(x,y,t)=σ(x,y,t2)-σ(x,y,t1). The stress change rate is For example, at a certain position (x=10m, y=5m), the stress value at time t1 is 20MPa, the stress value at time t2 is 22MPa, and the time interval t2-t1=1h. Then the stress change at this position is 2MPa, and the stress change rate is 2MPa / h.

[0097] Result display and warning

[0098] Display content: The display module visualizes the surrounding rock stress distribution field, stress change and change rate information obtained by the data processing module.

[0099] Two-dimensional graphic display: Display the surrounding rock stress distribution field in the form of contour map or color cloud map. In the contour map, points with equal stress values ​​are connected into contour lines. Different contour lines represent different stress levels. The change trend of stress can be intuitively seen through the density of the contour lines. For example, areas with dense contour lines indicate large stress changes, which may be places where TBM excavation has a greater impact on the surrounding rock in this area. In the color cloud map, different colors are assigned according to the size of the stress value. For example, areas with smaller stress values ​​are represented by blue, areas with larger stress values ​​are represented by red, and intermediate transitional stress values ​​are represented by green, yellow and other colors, so that operators can see the overall distribution of surrounding rock stress at a glance.

[0100] 3D graphics display: By building a 3D model, the surrounding rock stress distribution field is displayed in a three-dimensional form. The distribution of stress in space and the relationship between TBM excavation and surrounding rock stress changes can be observed more intuitively. For example, in the 3D model, the TBM cutterhead and body are displayed in actual shape, the surrounding rock is displayed in a semi-transparent way, and the stress value is marked on the surface or inside of the surrounding rock by color or contour lines. The operator can observe and analyze the distribution characteristics of the surrounding rock stress from different angles.

[0101] Numerical information display: In a specific area of ​​the display screen, the numerical information of stress change and change rate, as well as the corresponding position coordinates, are displayed in real time. For example, in the upper right corner of the display screen, information such as "stress change: +1.5MPa (x=12m, y=8m)" and "stress change rate: 0.8MPa / h" are displayed, which makes it easy for operators to accurately understand the stress changes at specific locations.

[0102] Alarm function: When the change amount or change rate of surrounding rock stress exceeds the preset threshold, the display module automatically sends out an audible and visual alarm signal. For example, when the stress change exceeds 5MPa, a red alarm window pops up on the display screen, and a sharp alarm sounds to remind the operator to pay attention to the stability of the surrounding rock. After receiving the alarm signal, the operator should immediately stop TBM excavation, take appropriate support measures or adjust excavation parameters to ensure construction safety. After the surrounding rock stress is stable, continue the excavation operation.

[0103] 3. Verification of the accuracy of the measurement method

[0104] Arrangement of reference measuring points

[0105] Before TBM excavation, in the selected measurement area, in addition to installing the stress sensor in the measurement system, several high-precision strain gauges are arranged as reference measurement points. The strain gauge should have a higher measurement accuracy than the stress sensor, for example, the accuracy can reach ±0.1% FS. Its installation position should be adjacent to or close to the stress sensor to ensure that the measured surrounding rock area is comparable. Generally, a strain gauge is arranged near each stress sensor (no more than 0.5m away), and the installation direction of the strain gauge should be consistent with the sensing direction of the stress sensor to ensure that the surrounding rock stress in the same direction is measured.

[0106] The installation method of strain gauges is similar to that of stress sensors. First, drill a hole in the surrounding rock, then insert the strain gauge into the hole, and use a special adhesive or fixture to fix it to the hole wall to ensure that the strain gauge is in close contact with the surrounding rock and can accurately measure the strain of the surrounding rock. After installation, the strain gauges are numbered and their position coordinates and installation parameters are recorded for subsequent data comparison and analysis.

[0107] Data collection and comparison

[0108] During the TBM excavation process, stress sensors and strain gauges simultaneously measure surrounding rock stress. The stress sensor collects data at its set sampling frequency (e.g., once per second), and the strain gauge also collects data at the same or similar frequency. The collected data is stored in their respective data recording devices, or transmitted to the data processing center in real time through the data transmission module for storage.

[0109] After the excavation is completed, the stress data measured by the stress sensor is compared with the stress data measured by the strain gauge, and the relative error between the two is calculated. The formula is:

[0110]

[0111] Among them, δ is the relative error, σ s is the measured value of the stress sensor, σ cis the strain gauge measurement value;

[0112] The accuracy of the measurement method is judged according to the size of the relative error. If the relative error is within the allowable range, the measurement method is considered accurate and reliable. If the relative error exceeds the allowable range, the measurement system needs to be checked and optimized, and the accuracy needs to be re-verified until the requirements are met. The allowable range is determined based on the actual engineering needs and relevant standards.

[0113] The above specific embodiments are only several optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant inspirations of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A method for measuring the stress change of surrounding rock during TBM excavation, characterized in that: The following steps are involved: Arrange stress sensors: multiple stress sensors are arranged in the surrounding rock in front of the TBM cutterhead and in the surrounding rock around the TBM body. The stress sensors are evenly distributed on circular measurement areas of different radii in a polar coordinate system with the center of the TBM cutterhead as the origin, and the stress sensors on adjacent circular measurement areas are staggered in the circumferential direction; in the surrounding rock around the TBM body, annular measurement belts are arranged at regular intervals along the axial direction of the body, and stress sensors are evenly distributed on each annular measurement belt, and the stress sensors on adjacent annular measurement belts are staggered in both the axial and circumferential directions; Data collection: During the TBM excavation process, the stress sensor collects surrounding rock stress data in real time; Data transmission: The stress data collected by the stress sensor is transmitted to the data processing unit. The transmission methods include wireless transmission and wired transmission. For sensors close to the TBM body, wired transmission is used, and data transmission is carried out through shielded cables to resist electromagnetic interference; for sensors far away, wireless transmission is used, and data transmission is carried out using Bluetooth or ZigBee wireless communication technology, and automatic frequency hopping and error correction functions are provided to ensure stable and reliable data transmission; Data processing: The collected original stress data is filtered to remove noise interference. The median filter algorithm is used. The formula is: y n =median{x n-k ,x n-k+1 ,…,x n+k-1 ,x n+k } Among them, x n is the nth data point in the original stress data sequence, y n is the data point after filtering, k is the half width of the filtering window; According to the position coordinates of the stress sensor in the surrounding rock, the filtered data is spatially interpolated to obtain the continuous distribution field of the surrounding rock stress. The Kriging interpolation algorithm is used, and the formula is: Where Z * (x0) is the estimated value at the interpolation point x0, Z(x i ) is a known point x i The measured value at i is the weight coefficient of the i-th known point, by solving the Kriging equations: We get, where γ(x i ,x j ) is a known point x i and x j The semivariogram function between them, u is the Lagrange multiplier. The surrounding rock stress distribution field at different times is compared and analyzed, and the change amount and change rate of surrounding rock stress are calculated. The formulas are: Wherein, Δσ(x,y,t) is the stress change at the position (x,y) at time t, σ(x,y,t1) and σ(x,y,t2) are the stress values ​​at the position (x,y) at time t1 and t2 respectively, and vΔσ(x,y,t) is the stress change rate at the position (x,y) at time t; Result display and early warning: The processed surrounding rock stress distribution field, stress change and change rate information are visualized through the display unit, and the display methods include two-dimensional contour map, color cloud map or three-dimensional graph; when the surrounding rock stress change or change rate exceeds the preset threshold, an audible and visual alarm signal is automatically issued to remind the operator to pay attention to the surrounding rock stability. The threshold can be set and adjusted according to different geological conditions and engineering requirements.

2. The method for measuring surrounding rock stress changes during TBM excavation according to claim 1, characterized in that: Before arranging the stress sensors, geological survey and analysis are also conducted on the measurement area, and the arrangement plan of the stress sensors is determined according to the geological conditions. The number and density of stress sensors are appropriately increased in areas with poor geological conditions such as broken zones and soft rock areas.

3. The method for measuring surrounding rock stress changes during TBM excavation according to claim 1, characterized in that: The method also includes a step of verifying the accuracy of the measurement method, which is as follows: Before TBM excavation, in addition to installing stress sensors, several high-precision strain gauges are arranged as reference measurement points in the selected measurement area. The measurement accuracy of the strain gauges is higher than that of the stress sensors, and their installation positions should be adjacent to or close to the stress sensors. During the TBM excavation process, stress sensors and strain gauges simultaneously measure the surrounding rock stress and record the data collected separately. After the excavation is completed, the stress data measured by the stress sensor is compared with the stress data measured by the strain gauge, and the relative error between the two is calculated. The formula is: Among them, δ is the relative error, σ s is the measured value of the stress sensor, σ c is the strain gauge measurement value; The accuracy of the measurement method is judged according to the size of the relative error. If the relative error is within the allowable range, the measurement method is considered accurate and reliable. If the relative error exceeds the allowable range, the measurement system needs to be checked and optimized, and the accuracy needs to be re-verified until the requirements are met. The allowable range is determined based on the actual engineering needs and relevant standards.

4. The method for measuring surrounding rock stress changes during TBM excavation according to claim 1, characterized in that: The method also includes measures for improving the adaptability of the measurement system, specifically including: When TBM excavation encounters different geological conditions, the arrangement density and position of stress sensors are adjusted according to the geological conditions, and different arrangement strategies are adopted in different geological areas such as soft rock, hard rock and broken zone; For the data transmission module, wireless transmission or wired transmission mode, or a hybrid transmission mode combining the two can be flexibly selected according to the electromagnetic environment and communication distance of the TBM excavation site; The algorithm parameters in the data processing module are adaptively adjusted according to different geological conditions and engineering requirements, including appropriately reducing the filter window size in the filter algorithm in soft rock areas and appropriately increasing the search radius in the interpolation algorithm in hard rock areas; The display interface and alarm threshold of the display unit are personalized according to the operator's habits and actual engineering conditions.

5. The method for measuring surrounding rock stress changes during TBM excavation according to claim 1, characterized in that: The stress sensor uses a piezoresistive strain gauge as a sensing element. The piezoresistive strain gauge is adhered to the surface of an elastic substrate with high strength and high elastic modulus, and is wrapped on the outside with a protective shell with good sealing and pressure resistance. The protective shell is provided with a force transmission structure that is in close contact with the surrounding rock.

6. The method for measuring surrounding rock stress changes during TBM excavation according to claim 1, characterized in that: The display unit displays information including surrounding rock stress related information, excavation speed, cutter head rotation speed, and displays the information in association with surrounding rock stress changes.

7. The method for measuring surrounding rock stress changes during TBM excavation according to claim 1, characterized in that: When the data is transmitted, encryption is performed on the transmitted data.

8. The method for measuring surrounding rock stress changes during TBM excavation according to claim 1, characterized in that: The measurement system is regularly maintained and calibrated, including checking the working status of the stress sensor and calibrating the accuracy of the data acquisition equipment. The maintenance and calibration cycle is determined according to the working intensity and environmental conditions of the TBM excavation.

9. The method for measuring surrounding rock stress changes during TBM excavation according to claim 1, characterized in that: The measured surrounding rock stress data are stored and recorded, and a database is established for further analysis and research on the data. The analysis and research include analyzing the laws of surrounding rock stress changes under different geological conditions and evaluating the long-term impact of TBM excavation on surrounding rock stability. The database includes data query and statistical analysis.

10. The method for measuring surrounding rock stress changes during TBM excavation according to claim 1, characterized in that: During the TBM excavation process, if special geological conditions or abnormal stress changes are encountered, the excavation operation will be suspended, and detailed geological surveys and stress analysis will be carried out on the surrounding rock. The measurement plan will be adjusted or corresponding engineering measures will be taken according to the analysis results. The measurement plan will be adjusted, and the layout of stress sensors will be further optimized and the data processing algorithm will be adjusted.

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