Multi-channel anchor rod stress information acquisition method and system based on full-bridge circuit

Abstract

This invention discloses a method and system for acquiring multi-channel anchor bolt force information based on a full-bridge circuit, specifically relating to the field of engineering structure strain and dimension measurement technology. It addresses the problems of low system integration, poor signal consistency across channels, and weak anti-interference capabilities leading to data distortion in existing multi-point anchor bolt force monitoring systems. By arranging multiple full-bridge strain circuits axially along the anchor bolt body and simultaneously acquiring their output signals, coherence analysis is performed on the multi-channel synchronous voltage signals to extract the coherence metric for each channel. Based on this metric, abnormal channel data is identified and weighted to calculate the axial force information at each measurement location. Finally, the effective anchorage length of the anchor bolt is determined based on the axial force distribution characteristics, and the results are output, achieving highly reliable, multi-dimensional monitoring of the anchor bolt's force state.

Description

Technical Field

[0001] This invention relates to the field of engineering structural strain and dimension measurement technology, and more specifically, to a method and system for acquiring multi-channel anchor bolt force information based on a full-bridge circuit. Background Technology

[0002] In support systems for mine roadways, tunnels, and slopes, the stress state of anchor bolts directly affects the stability of the support structure and the safety of the project. To assess the support effect and warn of potential risks, real-time and accurate monitoring of the axial stress information of the anchor bolts is necessary. In existing technologies, strain sensors are often placed on the anchor bolt body to indirectly measure its stress. One common approach is to use a single strain gauge or a half-bridge strain circuit, whose output signal is correlated with the micro-strain of the anchor bolt, thus converting the stress information. Another approach is to use mechanical instruments such as hydraulic support blocks to monitor the anchoring force at the tail of the anchor bolt.

[0003] However, when monitoring the stress distribution along the anchor bolt using existing technologies, each measuring point is usually equipped with an independent signal conditioning and acquisition unit, or a simple acquisition circuit with a limited number of channels is used. When facing the need to set up multiple measuring points along the length of the anchor bolt to obtain complete stress distribution information, this method has problems such as low system integration, complex wiring, and difficulty in ensuring the consistency of signals from each channel. At the same time, the actual working environment of the anchor bolt is subject to strong electromagnetic interference, while the output signal of a single strain gauge or half-bridge circuit is weak and has limited anti-common-mode interference capability, which can easily lead to distortion of monitoring data and make it difficult to meet the requirements of high-precision and long-term stable monitoring. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method and system for acquiring multi-channel anchor bolt force information based on a full-bridge circuit to solve the problems mentioned in the background art.

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

[0006] The method for acquiring multi-channel anchor bolt force information based on full-bridge circuit includes the following steps:

[0007] S1. Select multiple measurement positions along the axial direction on the rod body of the anchor to be monitored, and set a full-bridge strain circuit at each measurement position;

[0008] S2. Synchronously acquire the output signals of multiple full-bridge strain gauge circuits to obtain a set of synchronous voltage signals;

[0009] S3. Perform coherence analysis on the synchronization voltage signal and extract the coherence measure between each channel signal and the common pattern of the signal set; wherein, calculate the arithmetic mean of the synchronization voltage signal of each channel at the same sampling time, and take the sequence of arithmetic mean at each sampling time as the common pattern of the signal set.

[0010] S4. Based on coherence measurement, identify measurement channels with abnormal signals, and perform weighted processing on the synchronous voltage signals of measurement channels with abnormal signals to calculate the axial force information of the anchor rod to be monitored at the corresponding measurement position.

[0011] S5. Identify the force distribution characteristics along the anchor rod axis based on the axial force information at multiple measurement locations, and determine the effective anchorage length of the anchor rod according to the force distribution characteristics.

[0012] S6 outputs axial force information and effective anchorage length at multiple measurement locations.

[0013] Furthermore, multiple measurement locations are selected along the axial direction on the anchor rod to be monitored, and a full-bridge strain circuit is set at each measurement location, including:

[0014] Based on the design length of the anchor bolt to be monitored and geological condition parameters, multiple measurement locations are determined along the axial direction of the anchor bolt body.

[0015] At each measurement location, four strain gauges are arranged in the form of a Wheatstone bridge and fixed to the surface of the anchor rod to form a full-bridge strain circuit.

[0016] Furthermore, the output signals of multiple full-bridge strain gauge circuits are synchronously acquired to obtain a set of synchronous voltage signals, including:

[0017] The output signals of each full-bridge strain gauge circuit are sampled simultaneously using a data acquisition device with multiple acquisition channels.

[0018] The sampled signals from each channel are converted into digital voltage values;

[0019] Based on the same clock source, the converted digital voltage values ​​of each channel are latched to generate a set of synchronous voltage signals.

[0020] Furthermore, coherence analysis is performed on the synchronization voltage signal to extract the coherence metric between each channel signal and the common mode of the signal set, including:

[0021] Based on a set of synchronous voltage signals, calculate the common pattern of the signal set that represents the common trend of change of all channel signals;

[0022] For each channel signal, calculate its correlation coefficient with the common pattern of the signal set;

[0023] The correlation coefficient is used as a measure of the coherence of the channel signal.

[0024] Furthermore, based on coherence metrics, measurement channels with abnormal signals are identified, and the synchronization voltage signals of these abnormal measurement channels are weighted to calculate the axial force information of the anchor bolt under monitoring at the corresponding measurement location, including:

[0025] The coherence metric is compared with a preset coherence metric threshold to identify measurement channels with abnormal signals.

[0026] The synchronization voltage signal corresponding to the measurement channel with abnormal signal is assigned a lower weight, and the synchronization voltage signal corresponding to the measurement channel that is not identified as having abnormal signal is assigned a higher weight.

[0027] Based on the weighted synchronous voltage signals of each channel and the corresponding output characteristics of the full-bridge strain circuit, the axial force information of the anchor rod to be monitored at the corresponding measurement position is calculated.

[0028] Furthermore, assigning lower weights to the synchronization voltage signals corresponding to measurement channels with abnormal signals includes setting the weight of channel signals with coherence metrics lower than a preset coherence metric threshold to zero; assigning higher weights to the synchronization voltage signals corresponding to measurement channels not identified as having abnormal signals includes setting the weight of channel signals with coherence metrics not lower than a preset coherence metric threshold to the normalized result of their coherence metric values.

[0029] Furthermore, based on axial force information at multiple measurement locations, the force distribution characteristics along the anchor rod axis are identified, and the effective anchorage length of the anchor rod is determined according to the force distribution characteristics, including:

[0030] Based on the axial force information at multiple measurement locations, a force distribution curve along the anchor rod axis is generated;

[0031] Identify the turning point in the force distribution curve where the axial force significantly decreases from the tail end to the head end of the anchor bolt;

[0032] The distance between the turning point and the tail of the anchor rod is determined as the effective anchorage length of the anchor rod.

[0033] Furthermore, significant attenuation is identified as follows: among a series of continuous evaluation points selected from the tail of the anchor bolt towards the head at fixed step lengths, the tangent slope of the force distribution curve at each evaluation point or the average slope of the interval is calculated sequentially. The absolute value of the slope of the interval at the next evaluation point is subtracted from the absolute value of the slope of the interval at the previous evaluation point, and then divided by the absolute value of the slope of the interval at the previous evaluation point. The positive value of the result is taken as the slope change rate. If the calculated slope change rate is greater than the preset slope change rate threshold, then it is determined that there is a significant attenuation of axial force at that evaluation point.

[0034] Furthermore, it outputs axial force information and effective anchorage length at multiple measurement locations, including:

[0035] The axial force information at multiple measurement locations is associated with the corresponding measurement locations to form an axial force data list;

[0036] Output a list of axial force data and the effective anchorage length.

[0037] On the other hand, the present invention provides a multi-channel anchor bolt force information acquisition system based on a full-bridge circuit, comprising the following modules:

[0038] The circuit layout module is used to select multiple measurement positions along the axial direction on the rod body of the anchor to be monitored, and to set a full-bridge strain circuit at each measurement position.

[0039] The signal acquisition module is used to synchronously acquire the output signals of multiple full-bridge strain gauge circuits to obtain a set of synchronous voltage signals;

[0040] The coherence analysis module is used to perform coherence analysis on the synchronization voltage signal and extract the coherence metric between each channel signal and the common pattern of the signal set.

[0041] The anomaly handling module is used to identify measurement channels with abnormal signals based on coherence measurement, and to perform weighted processing on the synchronous voltage signals of the measurement channels with abnormal signals to calculate the axial force information of the anchor rod to be monitored at the corresponding measurement position.

[0042] The length determination module is used to identify the force distribution characteristics along the anchor rod axis based on the axial force information at multiple measurement locations, and to determine the effective anchorage length of the anchor rod according to the force distribution characteristics.

[0043] The information output module is used to output axial force information and effective anchorage length at multiple measurement locations.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. By deploying multiple full-bridge strain gauge circuits along the anchor bolt axis and implementing synchronous signal acquisition, the hardware ensures strict time alignment of data at each measurement point, providing a reliable timing basis for subsequent analysis. Introducing coherence analysis of the multi-channel synchronous voltage signals automatically extracts the consistency metric between each channel signal and the overall common pattern, thus constructing a mechanism for intrinsic quality self-assessment of multi-channel sensor signals. Through intelligent weighting of abnormal channel signals based on coherence metrics, it effectively suppresses distorted data introduced by local interference or occasional sensor failures when calculating axial force information, significantly enhancing the anti-interference and reliability of the final force information results and solving the problem of consistency and accuracy of multi-channel data in complex environments.

[0046] 2. By deeply exploring the inherent correlation of axial force information from multiple measuring points, a deeper understanding and feature extraction of the anchor bolt's working state was achieved. A continuous axial force distribution curve was generated from the force information at multiple measurement locations, and the turning point of significant force attenuation was intelligently identified. This enabled the quantitative determination of the effective anchorage length of the anchor bolt. The effective anchorage length is a characteristic quantity with clear physical meaning directly derived from the force distribution pattern, enabling dynamic evaluation of the effective load transfer range of the anchor bolt. The monitoring output was elevated from basic stress values ​​to anchorage state characteristic information with greater engineering diagnostic value. This not only provides a new, intuitive, and quantitative criterion for judging the working efficiency of the anchorage system but also lays a more solid information foundation for dynamic support design and safety early warning based on monitoring data. Attached Figure Description

[0047] Figure 1 This is a flowchart of the multi-channel anchor bolt force information acquisition method based on a full-bridge circuit according to the present invention;

[0048] Figure 2 This is a schematic diagram of the multi-channel anchor bolt force information acquisition system based on a full-bridge circuit according to the present invention. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0050] Example 1: Figure 1 The present invention provides a method for acquiring multi-channel anchor bolt force information based on a full-bridge circuit, which includes the following steps:

[0051] S1. Select multiple measurement positions along the axial direction on the rod body of the anchor to be monitored, and set a full-bridge strain circuit at each measurement position;

[0052] S2. Synchronously acquire the output signals of multiple full-bridge strain gauge circuits to obtain a set of synchronous voltage signals;

[0053] S3. Perform coherence analysis on the synchronization voltage signal and extract the coherence metric between each channel signal and the common mode of the signal set;

[0054] S4. Based on coherence measurement, identify measurement channels with abnormal signals, and perform weighted processing on the synchronous voltage signals of measurement channels with abnormal signals to calculate the axial force information of the anchor rod to be monitored at the corresponding measurement position.

[0055] S5. Identify the force distribution characteristics along the anchor rod axis based on the axial force information at multiple measurement locations, and determine the effective anchorage length of the anchor rod according to the force distribution characteristics.

[0056] S6 outputs axial force information and effective anchorage length at multiple measurement locations.

[0057] S1. Select multiple measurement positions along the axial direction on the anchor rod to be monitored, and set up a full-bridge strain circuit at each measurement position. The specific implementation is as follows:

[0058] Based on the design length of the anchor bolt to be monitored (i.e., the total length of the anchor bolt planned to be embedded in the soil and rock), and the geological condition parameters related to the location of the anchor bolt obtained through geological exploration, including the surrounding rock strength grade, rock mass integrity coefficient, and the expected range of the plastic zone, multiple measurement locations are determined along the axial direction of the anchor bolt. The measurement locations are determined as follows: one measurement location is set at the tail end and one at the head end of the anchor bolt. The measurement location at the tail end is 5% to 10% of the design length of the anchor bolt, and the measurement location at the head end is greater than or equal to 5% of the design length. On the section of the bolt between the tail and head end measurement locations, at least one intermediate measurement location is added at uniform intervals or according to the lithological change interface indicated by the geological condition parameters. For example, when the anchor bolt needs to pass through different rock layers with significant strength differences, a measurement location is added in the middle of each rock layer or near the rock layer interface. The total number of measurement locations is determined by geological condition parameters and design length, for example, no less than three measurement locations and no more than eight measurement locations.

[0059] At each designated measurement location, four resistance strain gauges are arranged and fixed to the surface of the anchor rod in a Wheatstone bridge configuration, forming a full-bridge strain circuit. During implementation, the surface of the anchor rod at the measurement location is ground and cleaned. Four resistance strain gauges of the same model and batch specifications are selected, with two defined as axial strain gauges and the other two as transverse strain gauges. The two axial strain gauges are attached to the rod surface at the measurement location in a parallel manner along the axial direction of the anchor rod, with the line connecting their center points parallel to the anchor rod axis. The two transverse strain gauges are attached to the rod surface at the same measurement location in a parallel manner along a direction perpendicular to the anchor rod axis, with the line connecting their center points perpendicular to the anchor rod axis. The four resistance strain gauges are arranged in a rectangular pattern around the center of the measurement location on the rod surface.

[0060] After pasting, connect the four strain gauges to form a Wheatstone bridge using wires. The connection is as follows: the first axial strain gauge and the first transverse strain gauge are connected in series to form the first arm of the Wheatstone bridge; the second axial strain gauge and the second transverse strain gauge are connected in series to form the second arm. The positive terminal of the Wheatstone bridge's power input is connected to the connection node between the first axial and transverse strain gauges, and the negative terminal is connected to the connection node between the second axial and transverse strain gauges. The positive terminal of the Wheatstone bridge's signal output is connected to the connection node between the first axial and second transverse strain gauges, and the negative terminal is connected to the connection node between the second axial and first transverse strain gauges. This connection method ensures that when the anchor rod undergoes axial tensile or compressive deformation, the resistance changes of the two axial strain gauges and the two transverse strain gauges are in opposite directions. The output voltage signal of the Wheatstone bridge is proportional to the axial strain, thus forming a full-bridge strain gauge circuit for measuring axial strain.

[0061] A waterproof insulating sealant layer is applied to the strain gauges and wires after the circuit connection is completed to protect the full-bridge strain gauge circuit. After the sealant layer cures, the bridge resistance of the full-bridge strain gauge circuit is tested using a multimeter. The bridge resistance value must be within a reasonable range of the nominal resistance value of this model of strain gauge. The insulation performance of the bridge is checked using a multimeter. The setup and fixing operation is repeated for each measurement position until a full-bridge strain gauge circuit is formed at all measurement positions.

[0062] S2. Synchronously acquire the output signals of multiple full-bridge strain gauge circuits to obtain a set of synchronous voltage signals. The specific implementation is as follows:

[0063] A data acquisition device with multiple analog signal acquisition channels connects the positive and negative output terminals of each full-bridge strain gauge circuit to the positive and negative input terminals of an independent analog signal acquisition channel of the acquisition device, respectively. Each full-bridge strain gauge circuit occupies one analog signal acquisition channel of the acquisition device. The acquisition device contains a programmable regulated power supply circuit that provides a stable DC excitation power supply to each connected full-bridge strain gauge circuit. The DC excitation power supply voltage is selected within the allowable operating voltage range of the resistance strain gauges in the full-bridge strain gauge circuit, for example, 5 volts or 10 volts. Under unified sampling command control, the acquisition device simultaneously samples the output signals of each full-bridge strain gauge circuit connected to each analog signal acquisition channel. The sampling process refers to the multiple sample-and-hold circuits within the acquisition device capturing and temporarily holding the instantaneous voltage value at the input terminal of each analog signal acquisition channel at the same moment. The acquisition device repeatedly performs simultaneous sampling operations at a fixed sampling frequency. The sampling frequency is set based on the highest frequency component that may change in the anchor bolt force. The highest frequency component is obtained by analyzing the typical time spectrum characteristics of the deformation of the surrounding rock in the roadway or the impact of mining. The sampling frequency is set to be at least twice the value of the estimated highest frequency component. For example, when the estimated highest frequency component is 50 Hz, the sampling frequency is set to 100 Hz or 200 Hz.

[0064] The sampled signals from each channel are converted into digital voltage values. The acquisition device contains an analog-to-digital converter (ADC) with multiple analog input ports corresponding to the number of analog signal acquisition channels, or a multiplexer that sequentially switches the outputs of the sample-and-hold circuits connected to each channel. The ADC resolution is selected based on the required measurement accuracy, such as 16-bit or 24-bit. The ADC reference voltage is a known stable voltage value, provided by a precision voltage reference source within the acquisition device, with an output voltage value of, for example, 2.5 volts or 5.0 volts. The conversion process involves the ADC comparing and quantizing the instantaneous analog voltage value held by each sample-and-hold circuit with its reference voltage, generating a digital code proportional to that instantaneous analog voltage value. This digital code is an integer value, and its range is determined by the ADC resolution; for example, for a 16-bit ADC, the digital code ranges from 0 to 65535. The obtained digital code is multiplied by the reference voltage of the analog-to-digital converter, and then divided by the maximum possible value of the digital code to obtain the corresponding digital voltage value, which is in volts. For example, when the reference voltage is 5.0 volts, the digital code is 32768, and the maximum possible value of the digital code is 65535, the calculated digital voltage value is 32768 × 5.0 volts / 65535, which is approximately 2.5 volts. This process is performed once for the signal captured by each analog signal acquisition channel during each sampling, thus obtaining a digital voltage value for each sample of each channel.

[0065] A set of synchronous voltage signals is generated by latching the converted digital voltage values ​​of each channel using a single clock source. The single clock source refers to the clock signal generated by a high-precision crystal oscillator circuit within the acquisition device. This clock signal is used to synchronously control the sampling time of the sample-and-hold circuit and the start-up time of the analog-to-digital converter (ADC). At the arrival of each sampling period determined by the sampling frequency, the clock edge signal emitted by the clock source triggers the sample-and-hold circuits of all channels to sample simultaneously, and after a fixed delay, triggers the ADC to begin analog-to-digital conversion. Once all channels' ADCs have completed conversion and output valid digital voltage values, a latch register within the acquisition device, under the action of a unified latch control signal (generated by a timing logic circuit from a clock signal), simultaneously stores the digital voltage values ​​generated by all channels at the same sampling time into the latch register. The set of digital voltage values ​​corresponding to all channels at the same sampling time stored in the latch register constitutes a set of synchronous voltage signals. This set of synchronous voltage signals is represented digitally as an array, where each element corresponds to the digital voltage value of a measurement channel at that sampling time, and the index of the array element has a fixed mapping relationship with the measurement channel number. The acquisition device continuously repeats the sampling, conversion, and latching process according to the sampling period, thereby generating multiple sets of synchronous voltage signal sequences arranged in time order for subsequent analysis.

[0066] S3. Perform coherence analysis on the synchronization voltage signal, and extract the coherence metric between each channel signal and the common mode of the signal set. Specifically, this is implemented as follows:

[0067] Based on a set of synchronous voltage signals obtained from the acquisition device, which includes the digital voltage values ​​corresponding to all measurement channels at the same sampling time, coherence analysis is performed on the synchronous voltage signals to extract the coherence metric between each channel signal and the common pattern of the signal set. A common pattern representing the common trend of all channel signals is calculated based on the set of synchronous voltage signals. For the multiple digital voltage values ​​constituting the set of synchronous voltage signals, the number of digital voltage values ​​equals the total number of measurement channels, and the arithmetic mean of these digital voltage values ​​is calculated. The arithmetic mean is calculated by adding the digital voltage values ​​of all measurement channels, dividing the sum by the total number of measurement channels, and the result is the value of the common pattern of the signal set at that sampling time. The unit of this value is the same as the digital voltage value, which is volts. For example, if there are three measurement channels, and the three digital voltage values ​​obtained at a certain sampling time are 1.2 volts, 1.3 volts, and 1.1 volts, then the arithmetic mean is (1.2 + 1.3 + 1.1) / 3 = 1.2 volts, which is the value of the common pattern of the signal set at that sampling time. For each set of synchronization voltage signals acquired sequentially over time, the value of the corresponding common pattern of the signal set is calculated using this method, resulting in a sequence of common patterns of the signal set arranged in chronological order. Each data point in the common pattern sequence of the signal set corresponds to a sampling time, and this sequence represents the common trend of all channel signals after removing the channel-specific differences.

[0068] For each channel signal, calculate its correlation coefficient with the common pattern of the signal set. A channel signal is a series of digital voltage values ​​generated at multiple consecutive sampling times for a specific measurement channel; that is, the time series of the channel's synchronization voltage signal. The common pattern of the signal set is a sequence of common patterns generated at the same multiple consecutive sampling times. The two sequences required to calculate the correlation coefficient must have the same length, cover the same range of sampling times, and have the same number of sampling points. The correlation coefficient is calculated as follows: Calculate the average of all digital voltage values ​​in the channel signal sequence, and calculate the average of all values ​​in the common pattern sequence. Calculate the covariance between the channel signal sequence and the common pattern sequence. The covariance is calculated as follows: For each sampling time, the deviation of the channel signal at that time is obtained by subtracting the average value of the channel signal sequence from the digital voltage value of the channel signal at that time. The deviation of the common pattern sequence of the signal set at that time is also obtained by subtracting the average value of the common pattern sequence of the signal set from the value of the common pattern sequence of the signal set at that time. The two deviations at the same sampling time are multiplied together to obtain the product of deviations at that sampling time. The sum of the products of deviations over all sampling times is then divided by the total number of sampling times. The result is the covariance. The standard deviation of the channel signal sequence is calculated by subtracting the average value of the channel signal sequence from the digital voltage value of each channel signal sequence. The sum of the squared values ​​over all sampling times is then divided by the total number of sampling times. The square root of the result is the standard deviation of the channel signal sequence. The standard deviation of the common pattern sequence of the signal set is calculated using the same method as for the channel signal sequence, using the values ​​and average value of the common pattern sequence of the signal set. The calculated covariance is divided by the product of the standard deviation of the channel signal sequence and the standard deviation of the common pattern sequence of the signal set. The result is the correlation coefficient between the channel signal and the common pattern of the signal set. The correlation coefficient is a dimensionless value, ranging from -1 to +1. The closer the absolute value of the correlation coefficient is to 1, the higher the linear correlation between the channel signal and the common pattern of the signal set; the closer the absolute value of the correlation coefficient is to 0, the lower the linear correlation between the channel signal and the common pattern of the signal set.

[0069] The calculated correlation coefficient is used as the coherence measure of the channel signal. The coherence measure is an index used to quantify the consistency between the channel signal and the common patterns of the overall signal set. A corresponding coherence measure value is calculated for each measurement channel. The coherence measure values ​​of all measurement channels constitute a coherence measure set. The coherence measure value is a real number between -1 and +1. Under normal conditions of anchor bolt force monitoring, the coherence measure values ​​of each channel signal are usually positive and close to 1, for example, they may be distributed in the range of 0.8 to 1.0. If the coherence measure value of a certain measurement channel is significantly lower than that of other channels, for example, below 0.5, it indicates that the full-bridge strain circuit corresponding to that channel is malfunctioning or is subject to strong local interference. The coherence measure will be used in subsequent steps to identify measurement channels with abnormal signals.

[0070] S4. Based on coherence measurement, identify measurement channels with abnormal signals, and perform weighted processing on the synchronization voltage signals of measurement channels with abnormal signals to calculate the axial force information of the anchor rod to be monitored at the corresponding measurement position. The specific implementation is as follows:

[0071] Coherence metrics are compared with a preset coherence metric threshold to identify measurement channels with abnormal signals. The preset coherence metric threshold is a pre-defined value used to determine whether the coherence metric is within the normal range. The method for obtaining the preset coherence metric threshold is based on statistical analysis of historical monitoring data under normal operating conditions. During a period of stable stress after anchor installation, synchronous voltage signals from each measurement channel are collected, and a series of coherence metric values ​​are calculated. These coherence metric values ​​obtained under stable conditions are statistically analyzed, and the mean and standard deviation of all coherence metric values ​​are calculated. The mean is subtracted from the value by 2, and the result is used as the benchmark reference value for the preset coherence metric threshold. Simultaneously, combined with engineering practice experience, the value of the preset coherence metric threshold is typically selected within the range of 0.5 to 0.7. Combining the benchmark reference value and the empirical range, a specific value for the preset coherence metric threshold is finally determined. For example, if the average coherence metric value obtained through historical data statistics is 0.92 and the standard deviation is 0.08, then subtracting twice the standard deviation from the average gives 0.76. This value of 0.76 falls outside the empirical range of 0.5 to 0.7 but is close. In this case, based on engineering judgment, the preset coherence metric threshold can be set to 0.75. The process of identifying measurement channels with abnormal signals involves comparing the coherence metric value of each measurement channel with the preset coherence metric threshold one by one. If the coherence metric value of a measurement channel is less than the preset coherence metric threshold, then that measurement channel is determined to be a measurement channel with abnormal signals. If the coherence metric value of a measurement channel is greater than or equal to the preset coherence metric threshold, then that measurement channel is determined to be a measurement channel not identified as having abnormal signals.

[0072] The synchronization voltage signals corresponding to measurement channels with abnormal signals are assigned lower weights, while those corresponding to measurement channels not identified as having abnormal signals are assigned higher weights. One way to assign lower weights is to set the weight of channel signals with a coherence metric below a preset coherence metric threshold to 0. A weight of 0 means that the synchronization voltage signal corresponding to the measurement channel with the abnormal signal is not included in the subsequent calculation of axial force information; its data is excluded. Another way to assign higher weights is to set the weight of channel signals with a coherence metric not lower than the preset coherence metric threshold to the normalized result of their coherence metric values. The purpose of normalization is to ensure that the sum of the weight values ​​of all measurement channels not identified as having abnormal signals is 1, and that the weight of each channel is proportional to its coherence metric value. The specific process of normalization is to first add the coherence metric values ​​of all measurement channels not identified as having abnormal signals to obtain a total coherence metric. Then, the coherence metric value of each measurement channel not identified as having signal anomalies is divided by the sum of the coherence metrics. The quotient is the normalized weight of that channel's signal. For example, there are three measurement channels not identified as having signal anomalies, with coherence metric values ​​of 0.85, 0.90, and 0.95, respectively. The sum of the coherence metrics is 0.85 + 0.90 + 0.95 = 2.70. The normalized weight of the first channel is 0.85 / 2.70 ≈ 0.315, the normalized weight of the second channel is 0.90 / 2.70 = 0.333, and the normalized weight of the third channel is 0.95 / 2.70 ≈ 0.352. These normalized weight values ​​are all greater than 0 and less than 1, and the sum of the three weight values ​​is 0.315 + 0.333 + 0.352 = 1.000. With this allocation method, channels with higher coherence metrics are considered to have higher signal reliability, and they are given greater weight in the calculation.

[0073] Based on the weighted synchronous voltage signals of each channel and their corresponding full-bridge strain gauge circuit output characteristics, the axial force information of the anchor rod under monitoring at the corresponding measurement position is calculated. The full-bridge strain gauge circuit output characteristic refers to the conversion relationship between the output voltage of the full-bridge strain gauge circuit and the surface strain of the anchor rod. This relationship is determined to be a constant through calibration experiments, called the strain gauge bridge sensitivity coefficient, with units of microstrain per volt. For each measurement channel, the method for calculating the axial force information varies depending on its weight value. For measurement channels with abnormal signals where the weight is set to 0, the potentially distorted synchronous voltage signal is not directly used to calculate the axial force information. An alternative method is to use the axial force information calculation results of the adjacent normal channel with a non-zero weight to estimate the axial force information at the corresponding position of the abnormal channel through linear interpolation. If the abnormal channel is located at an end point with no available adjacent normal channel, the axial force information value obtained from the previous effective calculation cycle is used. For measurement channels with non-zero weights that are not identified as abnormal signals, the calculation process is as follows. First, the synchronization voltage signal used for the current calculation of this channel is acquired. This synchronization voltage signal is the raw digital voltage value collected, measured in volts. The raw digital voltage value is multiplied by the normalization weight corresponding to this channel to obtain the weighted synchronization voltage signal value. Then, the weighted synchronization voltage signal value is multiplied by the strain gauge bridge sensitivity coefficient to obtain the axial strain value on the surface of the anchor rod at this measurement location. The axial strain value is usually expressed as microstrain, where 1 microstrain equals 10 to the power of -6. Finally, the axial force information is calculated according to Hooke's Law. The axial force information is equal to the axial strain value multiplied by the elastic modulus of the anchor rod material and then multiplied by the cross-sectional area of ​​the anchor rod. The elastic modulus is a material constant of the anchor rod steel, measured in gigapascals (GPa). For example, the elastic modulus of ordinary threaded steel is approximately 210 GPa. The cross-sectional area is calculated based on the nominal diameter of the anchor rod; for example, an anchor rod with a diameter of 22 mm has a cross-sectional area of ​​approximately 380 square millimeters. The calculated axial force information is measured in kilonewtons (kN). Following this method, an axial force information value is calculated for each measurement location corresponding to each measurement channel. These axial force values ​​collectively describe the force distribution along the axial direction of the anchor rod being monitored at the current moment.

[0074] S5. Identify the force distribution characteristics along the anchor rod axis based on axial force information at multiple measurement locations, and determine the effective anchorage length of the anchor rod according to the force distribution characteristics. Specifically, the implementation is as follows:

[0075] Based on axial force information from multiple measurement locations, a force distribution curve along the anchor bolt's axis is generated. The axial force information at these locations is a series of calculated values, each corresponding to a specific measurement location. The measurement location is identified by its distance from the tail end face of the anchor bolt; this distance is called the measurement point coordinate, typically measured in millimeters. The process of generating the force distribution curve includes data point preparation and curve construction. Data point preparation involves using the measurement point coordinates for each location as the abscissa and the axial force information value at that location as the ordinate, thus forming a data point. The set of data points from all measurement locations constitutes the original data for plotting the force distribution curve. Since the number of measurement locations is limited, the data points are discontinuous on the abscissa. To obtain a continuous curve to observe the trend of axial force variation along the anchor bolt's length, curve construction is necessary. One method for curve construction is to interpolate the original data points. Interpolation involves calculating the coordinates of more intermediate points between known adjacent data points according to mathematical rules, so that connecting these points forms a continuous curve. For example, cubic spline interpolation can be used. This method ensures that the generated interpolation curve passes through all original data points and has continuous first and second derivatives at the connection points, resulting in a smooth curve. Another method is polynomial fitting, which uses a polynomial function to approximate the relationship between axial force and the coordinates of the measuring points. The coefficients of the polynomial are determined using the least squares method to minimize the overall error between the ordinate value calculated by the polynomial function and the ordinate value of the original data points. Through interpolation or fitting, a continuously varying functional relationship from the tail to the head of the anchor bolt is obtained. This functional relationship is the mathematical expression of the force distribution curve. Based on this functional relationship, the estimated value of the axial force information corresponding to any position along the axial direction of the anchor bolt can be calculated, thus presenting the force distribution curve in the form of a graph or data list.

[0076] Identify the inflection point in the force distribution curve where the axial force significantly decreases from the tail to the head of the anchor bolt. The force distribution curve describes the trend of axial force values ​​as the coordinates of the measuring points change. When the anchor bolt is effectively anchored, the axial force typically decreases gradually from the tail to the head. The inflection point is a point on the force distribution curve where the rate of decrease in axial force with increasing distance changes significantly, typically showing a sharp slowdown in the rate of decrease, and the curve becoming relatively flat. The process of identifying the inflection point is based on the analysis of the first derivative or slope change of the force distribution curve. Specific steps include selecting a series of consecutive evaluation points from the tail to the head of the anchor bolt at a fixed step size, for example, 50 mm. For each evaluation point, calculate the slope of the tangent line to the force distribution curve at that point. Since the force distribution curve is given in functional form, the tangent line slope is obtained by calculating the value of the first derivative of this function at the evaluation point. If the curve is composed of discrete interpolation points, the average slope of the interval is approximated by the difference between two adjacent interpolation points. Starting from the tail of the anchor bolt, the slope values ​​of adjacent evaluation point intervals are compared sequentially. A slope change rate threshold is set to determine whether the slope has changed significantly. The slope change rate is calculated by subtracting the absolute value of the slope of the previous evaluation point interval from the absolute value of the slope of the subsequent evaluation point interval, then dividing by the absolute value of the slope of the previous evaluation point interval, and taking the positive value of the calculation result as the change rate. When the calculated slope change rate is greater than the preset slope change rate threshold, it is considered that a significant attenuation inflection point has occurred at that point. Another identification method is to find the inflection point on the force distribution curve, that is, the point where the concavity and convexity of the curve change, which is determined by analyzing the zero point of the second derivative of the curve. The identified inflection point corresponds to a specific measurement point location coordinate value.

[0077] The preset slope change rate threshold was obtained through statistical analysis of a large number of historical stress distribution curves of multiple normally anchored anchors under stable stress conditions. Specifically, the actual slope change rate near the inflection point of each historical curve was calculated, and the distribution range and central tendency of these change rate values ​​were statistically analyzed. For example, the average value of all change rate values ​​plus one standard deviation was taken as the threshold benchmark value. Combined with engineering experience, the preset slope change rate threshold was finally determined to be an empirical constant between 0.2 and 0.4.

[0078] The distance between the turning point and the tail of the anchor rod is defined as the effective anchorage length of the anchor rod. The tail of the anchor rod is the end face on the anchor rod body where the nut and the support plate are installed. The coordinate value of the measuring point at the turning point is the length measured along the anchor rod axis towards the head, with the tail of the anchor rod as the origin. The distance between the turning point and the tail of the anchor rod is numerically equal to the coordinate value of the measuring point at the turning point. This distance value is the effective anchorage length of the anchor rod at the current moment. The effective anchorage length represents the length of the portion of the anchor rod body that actually bears and transmits the axial load to the surrounding rock, and the unit is the same as the coordinate value of the measuring point, which is millimeters. For example, if the identified turning point is 1500 mm away from the end face of the anchor rod tail, then the effective anchorage length of the current anchor rod is 1500 mm. The effective anchorage length dynamically reflects the changes in the anchoring effect; during normal operation of the anchor rod, this length remains relatively stable or changes slowly. If the effective anchorage length is drastically shortened, for example, rapidly reduced from 2000 mm to 1200 mm, it may indicate a degradation in anchorage performance, such as localized debonding or rock slippage at the front end of the anchorage.

[0079] S6. Output axial force information and effective anchorage length at multiple measurement locations. The specific implementation is as follows:

[0080] Axial force information at multiple measurement locations is associated with their corresponding locations to form an axial force data list. The corresponding measurement locations are identified by their coordinates, which represent the distance from the measurement location to the end face of the anchor bolt, in millimeters. The association process involves creating a data record for each measurement location. Each data record contains two data items: the first stores the coordinate value of the measurement location, and the second stores the calculated axial force information at that location. All data records for each measurement location are arranged in ascending order of their coordinates, forming an ordered data set—the axial force data list. This axial force data list is represented in computer memory as an array data structure, where each element is a data record. For example, three measurement locations can generate a list of axial force data containing three records. The first record has a measurement point coordinate value of 500 and an axial force value of 45.3; the second record has a measurement point coordinate value of 1200 and an axial force value of 28.7; and the third record has a measurement point coordinate value of 2000 and an axial force value of 12.1. The measurement point coordinates are in millimeters, and the axial force values ​​are in kilonewtons. The axial force data list can also include a timestamp data item, which records the acquisition time of the data. The timestamp format is year-month-day hour:minute:second.

[0081] Outputs a list of axial force data and the effective anchorage length. Output is performed via a wired communication interface using the RS-485 electrical standard. During output, the axial force data list and the effective anchorage length are organized according to a predefined data encapsulation format. This format includes a frame header, a data length field, an effective anchorage length field, a record count field, a data record field, and a checksum field. The frame header occupies 2 bytes and contains the fixed hexadecimal value 0xAA55. The data length field occupies 2 bytes and contains the total number of bytes from the effective anchorage length field to the checksum field. The effective anchorage length field occupies 4 bytes and stores the effective anchorage length in millimeters using IEEE 754 single-precision floating-point format. The record count field occupies 2 bytes and stores the number of data records in the axial force data list using an unsigned integer format. The data record field stores each data record consecutively, with each record occupying 8 bytes. The first 4 bytes store the coordinates of the measurement point in signed integer format, and the last 4 bytes store the axial force information in IEEE 754 single-precision floating-point format. The check field occupies 2 bytes and contains the CRC16 cyclic redundancy check code calculated from all bytes from the frame header to the end of the data record field. The binary data stream organized according to this format is converted into differential electrical signals by the RS-485 communication interface's transmit driver and sent to the communication cable. For example, when the effective anchorage length is 1500.0 mm and the axial force data list contains the aforementioned three records, the data stream sent by the organization is as follows: frame header 0xAA55, data length field value (calculated), floating-point representation of the effective anchorage length field value of 1500.0, record quantity field value 3, binary representation of the first record data (500, 45.3), binary representation of the second record data (1200, 28.7), binary representation of the third record data (2000, 12.1), and the corresponding CRC16 checksum. This method completes the output of the axial force data list and the effective anchorage length value.

[0082] Example 2: Figure 2 A schematic diagram of the multi-channel anchor bolt force information acquisition system based on a full-bridge circuit of the present invention is provided. The multi-channel anchor bolt force information acquisition system based on a full-bridge circuit includes the following modules:

[0083] The circuit layout module is used to select multiple measurement positions along the axial direction on the rod body of the anchor to be monitored, and to set a full-bridge strain circuit at each measurement position.

[0084] The signal acquisition module is used to synchronously acquire the output signals of multiple full-bridge strain gauge circuits to obtain a set of synchronous voltage signals;

[0085] The coherence analysis module is used to perform coherence analysis on the synchronization voltage signal and extract the coherence metric between each channel signal and the common pattern of the signal set.

[0086] The anomaly handling module is used to identify measurement channels with abnormal signals based on coherence measurement, and to perform weighted processing on the synchronous voltage signals of the measurement channels with abnormal signals to calculate the axial force information of the anchor rod to be monitored at the corresponding measurement position.

[0087] The length determination module is used to identify the force distribution characteristics along the anchor rod axis based on the axial force information at multiple measurement locations, and to determine the effective anchorage length of the anchor rod according to the force distribution characteristics.

[0088] The information output module is used to output axial force information and effective anchorage length at multiple measurement locations.

[0089] All calculations involved in the embodiments are dimensionless numerical calculations, and the preset parameters and thresholds in the calculations are set by those skilled in the art according to the actual situation.

[0090] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0091] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and inventive constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0092] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0093] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or modules may be electrical, mechanical, or other forms.

[0094] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0095] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for acquiring multi-channel anchor bolt force information based on a full-bridge circuit, characterized in that, Includes the following steps: S1. Select multiple measurement positions along the axial direction on the rod body of the anchor to be monitored, and set a full-bridge strain circuit at each measurement position; S2. Synchronously acquire the output signals of multiple full-bridge strain gauge circuits to obtain a set of synchronous voltage signals; S3. Perform coherence analysis on the synchronization voltage signal and extract the coherence measure between each channel signal and the common pattern of the signal set; wherein, calculate the arithmetic mean of the synchronization voltage signal of each channel at the same sampling time, and take the sequence of arithmetic mean at each sampling time as the common pattern of the signal set. S4. Based on coherence measurement, identify measurement channels with abnormal signals, and perform weighted processing on the synchronous voltage signals of measurement channels with abnormal signals to calculate the axial force information of the anchor rod to be monitored at the corresponding measurement position. S5. Identify the force distribution characteristics along the anchor rod axis based on the axial force information at multiple measurement locations, and determine the effective anchorage length of the anchor rod according to the force distribution characteristics. S6 outputs axial force information and effective anchorage length at multiple measurement locations.

2. The method for acquiring multi-channel anchor bolt force information based on a full-bridge circuit according to claim 1, characterized in that, Multiple measurement locations are selected along the axial direction of the anchor rod to be monitored. A full-bridge strain circuit is set at each measurement location, including: Based on the design length of the anchor bolt to be monitored and geological condition parameters, multiple measurement locations are determined along the axial direction of the anchor bolt body. At each measurement location, four strain gauges are arranged in the form of a Wheatstone bridge and fixed to the surface of the anchor rod to form a full-bridge strain circuit.

3. The method for acquiring multi-channel anchor bolt force information based on a full-bridge circuit according to claim 1, characterized in that, The output signals of multiple full-bridge strain gauge circuits are synchronously acquired to obtain a set of synchronous voltage signals, including: The output signals of each full-bridge strain gauge circuit are sampled simultaneously using a data acquisition device with multiple acquisition channels. The sampled signals from each channel are converted into digital voltage values; Based on the same clock source, the converted digital voltage values ​​of each channel are latched to generate a set of synchronous voltage signals.

4. The method for acquiring multi-channel anchor bolt force information based on a full-bridge circuit according to claim 1, characterized in that, Coherence analysis is performed on the synchronization voltage signal to extract the coherence metric between each channel signal and the common mode of the signal set, including: Based on a set of synchronous voltage signals, calculate the common pattern of the signal set that represents the common trend of change of all channel signals; For each channel signal, calculate its correlation coefficient with the common pattern of the signal set; The correlation coefficient is used as a measure of the coherence of the channel signal.

5. The method for acquiring multi-channel anchor bolt force information based on a full-bridge circuit according to claim 1, characterized in that, Based on coherence metrics, measurement channels with abnormal signals are identified. The synchronization voltage signals of these abnormal measurement channels are then weighted to calculate the axial force information of the anchor bolt at the corresponding measurement location, including: The coherence metric is compared with a preset coherence metric threshold to identify measurement channels with abnormal signals. The synchronization voltage signal corresponding to the measurement channel with abnormal signal is assigned a lower weight, and the synchronization voltage signal corresponding to the measurement channel that is not identified as having abnormal signal is assigned a higher weight. Based on the weighted synchronous voltage signals of each channel and the corresponding output characteristics of the full-bridge strain circuit, the axial force information of the anchor rod to be monitored at the corresponding measurement position is calculated.

6. The method for acquiring multi-channel anchor bolt force information based on a full-bridge circuit according to claim 5, characterized in that, Assigning lower weights to the synchronization voltage signals corresponding to measurement channels with abnormal signals includes setting the weight of channel signals with coherence metrics below a preset coherence metric threshold to zero; assigning higher weights to the synchronization voltage signals corresponding to measurement channels not identified as having abnormal signals includes setting the weight of channel signals with coherence metrics not below a preset coherence metric threshold to the normalized result of their coherence metric values.

7. The method for acquiring multi-channel anchor bolt force information based on a full-bridge circuit according to claim 1, characterized in that, Based on axial force information from multiple measurement locations, the stress distribution characteristics along the anchor rod's axial direction are identified, and the effective anchorage length of the anchor rod is determined according to these characteristics, including: Based on the axial force information at multiple measurement locations, a force distribution curve along the anchor rod axis is generated; Identify the turning point in the force distribution curve where the axial force significantly decreases from the tail end to the head end of the anchor bolt; The distance between the turning point and the tail of the anchor rod is determined as the effective anchorage length of the anchor rod.

8. The method for acquiring multi-channel anchor bolt force information based on a full-bridge circuit according to claim 7, characterized in that, Significant attenuation is identified as follows: For a series of consecutive evaluation points selected at fixed step lengths from the tail of the anchor bolt towards the head, the tangent slope of the force distribution curve at each evaluation point or the average slope of the interval is calculated sequentially. The absolute value of the slope of the interval at the next evaluation point is subtracted from the absolute value of the slope of the interval at the previous evaluation point, and then divided by the absolute value of the slope of the interval at the previous evaluation point. The positive value obtained is taken as the slope change rate. If the calculated slope change rate is greater than the preset slope change rate threshold, then the inflection point at which significant attenuation of axial force occurs is determined.

9. The method for acquiring multi-channel anchor bolt force information based on a full-bridge circuit according to claim 1, characterized in that, Outputs axial force information and effective anchorage length at multiple measurement locations, including: The axial force information at multiple measurement locations is associated with the corresponding measurement locations to form an axial force data list; Output a list of axial force data and the effective anchorage length.

10. A multi-channel anchor bolt force information acquisition system based on a full-bridge circuit, used to implement the multi-channel anchor bolt force information acquisition method based on a full-bridge circuit as described in any one of claims 1-9, characterized in that, Includes the following modules: The circuit layout module is used to select multiple measurement positions along the axial direction on the rod body of the anchor to be monitored, and to set a full-bridge strain circuit at each measurement position. The signal acquisition module is used to synchronously acquire the output signals of multiple full-bridge strain gauge circuits to obtain a set of synchronous voltage signals; The coherence analysis module is used to perform coherence analysis on the synchronization voltage signal and extract the coherence metric between each channel signal and the common pattern of the signal set. The anomaly handling module is used to identify measurement channels with abnormal signals based on coherence measurement, and to perform weighted processing on the synchronous voltage signals of the measurement channels with abnormal signals to calculate the axial force information of the anchor rod to be monitored at the corresponding measurement position. The length determination module is used to identify the force distribution characteristics along the anchor rod axis based on the axial force information at multiple measurement locations, and to determine the effective anchorage length of the anchor rod according to the force distribution characteristics. The information output module is used to output axial force information and effective anchorage length at multiple measurement locations.

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