A System and Method for Analyzing Acoustic Emission Signals of Freeze-Thaw Damage in Soil and Rock Mass

Abstract

This invention relates to the field of geotechnical engineering mechanics testing and non-destructive testing technology. Existing technologies suffer from high computational delays due to passive monitoring modes, the inability to perform real-time physical intervention before macroscopic brittle fracture of soil and rock masses, and the inability to effectively preserve the critical failure state of rocks for microscopic damage constitutive relationship studies. This invention discloses a system and method for analyzing acoustic emission signals from freeze-thaw damage in soil and rock masses. A signal acquisition module is used to capture acoustic emission signals in real time; a feature analysis module is used to extract frequency band energy distribution characteristics and the instantaneous rate of change of the dominant frequency drift; a state determination module is used to determine the microcrack damage evolution stage and the precursors to critical failure based on the above features; and a linkage intervention module is used to generate physical intervention commands based on the determination results, enabling real-time adaptive adjustment or state latching of mechanical loads and ambient temperature. This allows for microsecond-level closed-loop linkage intervention, suppressing sudden shear surface slippage and instability, and effectively preserving the microstructure of rocks on the eve of critical failure.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering mechanics testing and non-destructive testing technology, and in particular to a system and method for analyzing acoustic emission signals of freeze-thaw damage in soil and rock. Background Technology

[0002] In cold-region geotechnical engineering and deep rock mechanics research, the soil and rock masses upon which bridges, tunnels, hydraulic engineering structures, and dams rely are subjected to the combined effects of geostress and cyclic temperature fields over long periods. Freeze-thaw cycles cause phase changes in pore water and incoordination in mineral thermal deformation, easily leading to the initiation and propagation of microcracks, resulting in deterioration of strength, deformation modulus, and permeability, and inducing engineering disasters such as cracking deformation. Existing technologies typically employ acoustic emission monitoring of soil and rock damage evolution, combined with freeze-thaw environment control and mechanical loading devices for testing. One approach focuses on passively acquiring acoustic emission signals and relying on offline algorithms or deep learning models to identify the fracture state. Another approach uses preset temperature control curves and loading programs to achieve freeze-thaw and stress tests. However, the former approach lacks real-time reverse control capabilities, and the algorithms and models suffer from computational delays and limited generalization, making it difficult to implement real-time intervention before macroscopic fracture. In the latter approach, the subsystems lack real-time feedback linkage based on the internal damage state of the sample, making it impossible to adjust the test process in time in the face of sudden fracture, resulting in difficulty in obtaining the complete state under critical failure conditions, which is detrimental to subsequent three-dimensional reconstruction analysis. Summary of the Invention

[0003] The purpose of this invention is to provide a system and method for analyzing acoustic emission signals of freeze-thaw damage in soil and rock, in order to solve the technical problems in the prior art, such as high computational delay due to passive monitoring mode, inability to perform real-time physical intervention before macroscopic brittle fracture of soil and rock, and inability to effectively preserve the critical failure state of soil and rock for microscopic damage constitutive relationship research.

[0004] To address the above problems, the present invention proposes the following technical solution: In a first aspect, the present invention proposes a system for analyzing acoustic emission signals of freeze-thaw damage in soil and rock masses, comprising: The signal acquisition module is used to capture acoustic emission signals generated by soil and rock under force-thermal coupling in real time; The feature analysis module is used to perform frequency domain analysis on the acoustic emission signal and extract the frequency band energy distribution characteristics and the instantaneous change rate of the dominant frequency drift to characterize the freeze-thaw damage of the rock and soil. The state determination module is used to determine the damage evolution stage and critical failure precursor of the microcracks inside the rock and soil mass based on the frequency band energy distribution characteristics and the instantaneous change rate of the dominant frequency drift. The linkage intervention module is used to generate physical intervention commands based on the damage evolution stage and critical failure precursors; the physical intervention commands are used to adaptively adjust or lock the mechanical load and ambient temperature applied to the rock and soil in real time.

[0005] Furthermore, the signal acquisition module includes an ultra-wideband multi-channel acoustic emission acquisition array; The linkage intervention module performs real-time adaptive adjustment or state latching through a micron-level fully digital closed-loop mechanical servo rack and an ultra-wide temperature range multi-phase change environment coupling control box.

[0006] Furthermore, the feature parsing module includes: The energy distribution analysis unit is used to separate the high-frequency energy and low-frequency energy of the acoustic emission signal within a sliding analysis time window, and calculate the relative proportion coefficient of the low-frequency energy to the total energy of the entire frequency band as the frequency band energy distribution feature. The main frequency drift tracking unit is used to track the main frequency that makes the power spectral density reach the global maximum value within the sliding analysis time window, and extract the instantaneous change rate of the main frequency with time as the instantaneous change rate of the main frequency drift.

[0007] Furthermore, the method for calculating the relative proportion of low-frequency energy to the total energy of the entire frequency band includes:

[0008]

[0009]

[0010] in, To analyze the time The cumulative value of low-frequency acoustic emission energy within the sliding time window at the endpoint. To define the cutoff frequency threshold for distinguishing between high-frequency and low-frequency energy, For acoustic emission signals at the analysis time A specific frequency within a sliding time window as the endpoint The power spectral density value at that location, To analyze the time The total accumulated energy of the full-band acoustic emission signal within the sliding time window ending at the endpoint. The highest effective analysis frequency boundary, To analyze the time The relative scaling factor within the sliding time window ending at the endpoint.

[0011] Furthermore, the method for calculating the instantaneous rate of change of the dominant frequency drift includes:

[0012]

[0013] in, To analyze the time The frequency that maximizes the power spectral density within a sliding time window ending at the endpoint, i.e., the dominant frequency. To analyze the time The frequency value that maximizes the power spectral density within the sliding time window ending at the endpoint. The time step interval between two consecutive feature parsing operations performed by the feature parsing module. To analyze the time The instantaneous rate of change of the dominant frequency drift within the sliding time window with the endpoint as the endpoint.

[0014] Furthermore, the method for determining the damage evolution stage of microcracks within the soil and rock mass includes: If a deterministic negative drift is continuously detected in the instantaneous rate of change of the dominant frequency drift, and the absolute value of the instantaneous rate of change of the dominant frequency drift exceeds the preset critical threshold for the negative drift rate of the dominant frequency, then it is determined that the microcracks inside the rock and soil mass are undergoing a substantial transformation from the tension mode to the shear mode. Methods for determining the precursors of critical damage include: A joint judgment mechanism is adopted. When the frequency band energy distribution characteristics exceed the preset low frequency band energy ratio warning threshold within a continuous preset analysis period, and the total energy of the entire frequency band is greater than the pre-calibrated environmental background noise shielding baseline, it is determined that the soil and rock mass has entered the macroscopic critical failure precursor stage.

[0015] Furthermore, when it is determined that the microcracks inside the soil and rock mass are undergoing a substantial transition from a tension mode to a shear mode, the basic benchmark mechanical loading rate set before the compensation mechanism is triggered is reduced based on the degree to which the absolute value of the instantaneous change rate of the dominant frequency drift exceeds the preset critical threshold of the negative drift rate of the dominant frequency. This generates a real-time control rate command value for the mechanical load on the soil and rock mass, which serves as a physical intervention command for real-time adaptive adjustment of the mechanical load applied to the soil and rock mass, triggering the compensation mechanism. The greater the degree to which the absolute value of the instantaneous change rate of the dominant frequency drift exceeds the critical threshold of the negative drift rate of the dominant frequency, the greater the magnitude of the reduction adjustment.

[0016] Furthermore, when it is determined that the rock and soil mass has entered a macroscopic state of critical impending failure, the method for generating the physical intervention command includes: The emergency latching intervention mode is triggered, the displacement control rate command is forced to zero to lock the mechanical displacement, the ambient temperature cycle control is cut off, and the PID constant temperature fine-tuning is started to keep the current ambient temperature constant, thereby realizing the latching of the microstructure state of the soil and rock mass before critical failure.

[0017] Furthermore, when the emergency latching intervention mode is triggered, a physical emergency stop level signal is generated by the high-speed optocoupler isolation output terminal of the field programmable gate array and transmitted along the hardwire to the interrupt terminal of the control system for mechanical load and ambient temperature.

[0018] Secondly, this invention proposes a method for analyzing acoustic emission signals of freeze-thaw damage in soil and rock masses, including: Real-time capture of acoustic emission signals generated by soil and rock masses under force-thermal coupling; Frequency domain analysis was performed on the acoustic emission signal to extract the frequency band energy distribution characteristics and the instantaneous change rate of the dominant frequency drift, which are used to characterize the freeze-thaw damage of rock and soil. Based on the frequency band energy distribution characteristics and the instantaneous change rate of the dominant frequency drift, the damage evolution stage and critical failure precursor of the microcracks inside the rock and soil mass are determined. Based on the damage evolution stage and critical failure precursors, physical intervention commands are generated; these commands are used to adaptively adjust or lock the mechanical loads and ambient temperature applied to the soil and rock mass in real time.

[0019] The beneficial effects of this invention are as follows: This invention proposes an acoustic emission signal analysis system for freeze-thaw damage in soil and rock. A signal acquisition module captures acoustic emission signals under force-thermal coupling in real time, and a feature analysis module extracts frequency band energy distribution characteristics and the instantaneous rate of change of the dominant frequency drift. This allows for timely characterization of dynamic information related to microcrack initiation and propagation during freeze-thaw damage in soil and rock. Furthermore, a state determination module, based on the aforementioned characteristics, determines the damage evolution stage of internal microcracks and the precursors to critical failure, improving the targeting and timeliness of soil and rock damage state identification. A linkage intervention module then generates physical intervention commands based on the determination results, enabling real-time adaptive adjustment or state latching of mechanical loads and ambient temperature. This allows the acoustic emission analysis results to directly influence the experimental process control, enhancing the feedback linkage between monitoring, loading, and temperature control. This facilitates timely intervention before critical failure, reduces the probability of sudden complete failure of the sample, and helps retain state information under critical conditions to support subsequent damage mechanism analysis and structural characterization.

[0020] Furthermore, this invention tracks the instantaneous rate of change of the dominant frequency drift of the acoustic emission signal within the sliding analysis time window, and determines the damage evolution stage of the microcracks inside the soil and rock mass by combining the preset critical threshold of the negative drift rate of the dominant frequency. When the microcracks inside the soil and rock mass are detected to have substantially changed from the tension mode to the shear mode, the invention adaptively calculates and issues micron-level displacement retreat or deceleration commands, thereby dynamically adjusting the external mechanical energy input to match the energy required for the propagation of internal cracks, suppressing the sudden sliding instability of the shear surface, and realizing stable control and refined capture of the microscopic evolution process of damage in soil and rock mass.

[0021] Furthermore, this invention extracts the relative proportion coefficient of low-frequency energy to the total energy of the entire frequency band, and uses the environmental background noise shielding baseline for joint judgment. When macroscopic signs of critical failure are detected, it directly forces a zero displacement control rate command and cuts off the environmental temperature cycle control to maintain a constant temperature. This allows the axial strain and confining pressure strain of the soil and rock mass to be locked in time before macroscopic critical failure occurs, effectively preserving the microscopic fracture network of the soil and rock mass on the eve of critical failure. This provides an objective and complete structural carrier for subsequent studies such as high-precision X-ray three-dimensional CT in-situ tomography.

[0022] Furthermore, when the emergency latching intervention mode is triggered, the present invention generates a physical emergency stop level signal from the high-speed optocoupler isolated output terminal of the field-programmable gate array (FPGA) and transmits it along the hardwire to the interrupt terminal of the control system for mechanical load and ambient temperature. This allows the system to bypass the process scheduling and bus communication delays of the host operating system, thereby independently and quickly completing the critical threshold determination and outputting the physical emergency stop level signal. This low-level hardware-level direct intervention mechanism significantly shortens the system response time and improves the reliability of physical interruption within the extremely short time window of brittle fracture in soil and rock. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a system framework diagram of an acoustic emission signal analysis system for freeze-thaw damage in soil and rock provided in an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram illustrating the principle of the acoustic emission signal feature analysis algorithm of an acoustic emission signal analysis system for freeze-thaw damage in soil and rock provided in an embodiment of the present invention.

[0026] Figure 3This is a schematic diagram of the two-level linkage intervention closed-loop control and timing of a system for analyzing acoustic emission signals of freeze-thaw damage in soil and rock provided in an embodiment of the present invention. The upper part is a schematic diagram of the principle of frequency band energy distribution characteristic analysis, and the lower part is a schematic diagram of the principle of tracking the instantaneous rate of change of the main frequency drift. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0029] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0030] Geotechnical engineering and deep rock mechanics research in cold regions widely involves bridges, tunnels, hydraulic engineering structures, dams, and other scenarios. The soil and rock masses upon which these projects rely are subjected to the combined effects of geostress and periodic temperature fields over long periods. During freeze-thaw cycles, pore water repeatedly freezes and thaws, easily leading to frost heave at the tips of pores and cracks. This frost heave, combined with the difference in thermal expansion and contraction of mineral particles, affects the internal structural stability of the rock mass. In these applications, microcracks within the soil and rock mass gradually initiate, expand, and connect under freeze-thaw cycles, resulting in continuous accumulation of physical weathering and mechanical damage. Macroscopically, this manifests as strength reduction, decreased deformation modulus, and altered permeability, potentially leading to cracking, deformation, and other engineering instability problems. Therefore, effective monitoring and assessment of the damage evolution process are necessary.

[0031] Therefore, existing technologies typically employ acoustic emission technology to non-destructively monitor the release of strain energy within materials, combined with freeze-thaw environment control devices and mechanical loading devices for testing. One type of technology primarily acquires acoustic emission signals with high fidelity and then identifies fracture modes using offline algorithms or deep learning models; another type controls the freeze-thaw and stress processes through preset temperature control curves, loading rates, and other procedures. However, existing solutions still have the following shortcomings: On the one hand, current testing paradigms are mostly limited to passive monitoring and post-event analysis. Acoustic emission acquisition systems merely act as observers, responsible for high-fidelity signal recording, relying on complex mathematical algorithms for offline processing. These systems lack reverse hardware control channels, making it impossible to directly intervene at the physical source of damage when abrupt damage changes are detected in the rock mass. Furthermore, due to the time-consuming nature of the algorithms, their computational latency is simply insufficient to meet the hard real-time requirements for emergency physical intervention before macroscopic brittle fracture of rocks. In addition, when introducing black-box models such as deep learning for fracture mode recognition, the generalization ability of the models is limited, and the forward inference of neural networks consumes a large amount of computational resources and time. This uncertain computational latency can easily lead to lag and loss of control in the control system at critical mechanical phase transition nodes.

[0032] On the other hand, existing complex freeze-thaw and mechanical loading test devices are essentially still mechanically assembled from various subsystems. Environmental temperature control curves, hydraulic loading rates, and other parameters are all programmed before the test, making intelligent communication and compromise between different physical fields impossible. When faced with sudden rock and soil fracturing, the loading and environmental control equipment cannot sense the crisis inside the sample. This open-loop control system, lacking real-time feedback and linkage, means researchers can only obtain completely destroyed rock fragments, unable to acquire the complete physical state of the rock under critical failure conditions, severely hindering high-precision X-ray three-dimensional CT reconstruction research.

[0033] In view of the above, the present invention provides a system and method for analyzing acoustic emission signals of freeze-thaw damage in soil and rock masses. The present invention will be further described in detail below with reference to embodiments and accompanying drawings.

[0034] like Figure 1 The diagram shown is a schematic representation of the acoustic emission signal analysis system for freeze-thaw damage in soil and rock according to the present invention, which may include: The signal acquisition module is used to capture acoustic emission signals generated by soil and rock under force-thermal coupling in real time.

[0035] It should be noted that real-time capture refers to continuously acquiring acoustic emission responses related to internal damage activity during the loading and temperature changes of the soil and rock mass, enabling subsequent processing to analyze the current damage evolution state. In some embodiments, the signal acquisition module can be used in conjunction with a corresponding acoustic emission sensing component. Optionally, the acquired acoustic emission signals can also be amplified, filtered, buffered, transmitted, or synchronized.

[0036] The feature analysis module is used to perform frequency domain analysis on the acoustic emission signal and extract the frequency band energy distribution characteristics and the instantaneous change rate of the dominant frequency drift to characterize the freeze-thaw damage of the rock and soil.

[0037] It should be noted that the frequency band energy distribution characteristics are used to reflect the energy distribution of the acoustic emission signal in different frequency ranges, so as to characterize the frequency domain response changes corresponding to crack activity in soil and rock during freeze-thaw damage. The instantaneous rate of change of the dominant frequency drift is used to reflect the speed at which the dominant frequency of the acoustic emission signal changes over time, so as to characterize the dynamic abrupt change trend of signal characteristics during damage development. In some embodiments, frequency domain analysis can be performed using appropriate spectral transformation, time-frequency analysis, or other methods that enable frequency domain feature extraction. The specific frequency domain analysis method can be selected according to the actual application needs and is not limited to a fixed algorithm.

[0038] The state determination module is used to determine the damage evolution stage and critical failure precursor of the microcracks inside the rock and soil mass based on the frequency band energy distribution characteristics and the instantaneous change rate of the dominant frequency drift.

[0039] It should be noted that the state determination module does not only judge isolated signals at a single moment, but combines the frequency band energy distribution characteristics and the characteristic changes represented by the instantaneous change rate of the dominant frequency drift to identify the evolutionary state of microcracks inside the soil and rock mass from initiation and propagation to near instability, and further determine whether there are signs of critical failure. In some embodiments, state determination can employ threshold comparison, rule matching, feature correlation analysis, or other methods capable of state identification. Optionally, the damage evolution stage can be divided into several stages according to actual needs, and signs of critical failure can also be identified based on pre-set judgment conditions.

[0040] The linkage intervention module is used to generate physical intervention commands based on the damage evolution stage and critical failure precursors; the physical intervention commands are used to adaptively adjust or lock the mechanical load and ambient temperature applied to the rock and soil in real time.

[0041] It should be noted that in this invention, the acoustic emission signal analysis results are not merely used for post-event recording or offline analysis, but can be further transformed into output information for physical field control, enabling the system to respond to external conditions based on the current damage state of the soil and rock mass. In some embodiments, when the determination result indicates that the soil and rock mass is in a certain damage evolution stage, the linkage intervention module can output adjustment commands adapted to that stage to adjust the mechanical load and ambient temperature accordingly; when the determination result indicates the appearance of precursors to critical failure, the linkage intervention module can also output state latching commands to maintain the current mechanical load and / or ambient temperature in the corresponding state, so as to preserve the state information of the soil and rock mass before critical failure. As for the adjustment amplitude, adjustment rhythm, latching object, and execution method, they can be set according to specific application requirements and are not limited to a fixed form.

[0042] Furthermore, the present invention will be described in more detail through some more specific embodiments. For example... Figure 2 The diagram shown is a schematic of the acoustic emission signal analysis system for freeze-thaw damage in soil and rock according to the present invention.

[0043] To achieve microsecond-level physical closed-loop intervention, the signal acquisition module can be deployed as an ultra-wideband multi-channel acoustic emission acquisition array. Internally, it is equipped with a piezoelectric ceramic broadband sensor, a bandpass filter, and an ultra-low noise differential preamplifier. The piezoelectric ceramic broadband sensor converts high-frequency and low-frequency stress wave signals generated by microscopic damage release within the rock into electrical signals. The bandpass filter suppresses interference components outside the target frequency band, and the ultra-low noise differential preamplifier amplifies the weak electrical signals with low noise to improve the signal quality required for subsequent analysis. In this way, the acoustic emission response corresponding to microscopic damage release within the rock can be captured in situ and converted into a microvolt-level analog voltage signal for frequency domain analysis by the subsequent feature analysis module. In practical applications, the number of channels, frequency coverage, and specific selection of components in the acquisition array can be flexibly configured according to different acquisition accuracy, response speed, and on-site deployment conditions.

[0044] To improve the processing speed of acoustic emission signal analysis and intervention triggering, the feature analysis module and the state determination module can be jointly deployed in the underlying ultra-high-speed data stream processing and triggering center. The underlying ultra-high-speed data stream processing and triggering center refers to the processing unit used to rapidly process the data output by the signal acquisition module, identify its state, and generate trigger control information. This center may contain a Field Programmable Gate Array (FPGA) and a Digital Signal Processor (DSP). The FPGA can be used to handle high-speed parallel data reception, data buffering, preprocessing, feature extraction triggering, and logic control tasks to meet the low-latency processing requirements of continuous data streams. The DSP can be used to perform operations related to frequency domain analysis, feature calculation, and state determination, so as to identify the damage evolution stages and critical failure precursors of microcracks within the soil and rock mass based on changes in the acoustic emission signal. Through this joint deployment, the frequency band energy distribution characteristics and the instantaneous change rate of the dominant frequency drift output by the feature analysis module can be directly provided to the state determination module for processing within a short path, thereby reducing data transmission latency between modules.

[0045] Specifically, the underlying ultra-high-speed data stream processing and triggering center can also be configured with opto-isolated high-speed digital output terminals. In practical applications, when the state determination module identifies the corresponding damage evolution stage or critical failure precursor, it can output corresponding control information to the linkage intervention module or related execution equipment via the opto-isolated high-speed digital output terminals to support subsequent real-time adaptive adjustment or state latching of mechanical load and ambient temperature. It should be noted that the specific models, quantities, interface forms, and task allocation methods of the field-programmable gate array, independent digital signal processor, and opto-isolated high-speed digital output terminals can all be set according to actual application requirements. In some embodiments, the physical execution end of the linkage intervention module can be deployed as a micron-level fully digital closed-loop mechanical servo rack and an ultra-wide temperature range multi-phase change environment coupling control box. In practical applications, the micron-level fully digital closed-loop mechanical servo rack can be equipped with an AC permanent magnet synchronous servo motor and a zero-backlash ball screw. The AC permanent magnet synchronous servo motor provides a fast-response and stable drive output, while the zero-backlash ball screw converts the motor's rotary motion into linear motion and reduces the impact of transmission backlash on loading accuracy and control response, thus facilitating more precise adjustment of mechanical loads on soil and rock. The ultra-wide temperature range multi-phase change environment coupling control box can be equipped with a carbon fiber transmission line sealed chamber, a liquid nitrogen cryogenic vaporization spray module, and a semiconductor Peltier precision cooling and heating array. The carbon fiber transmission line sealed chamber provides a relatively enclosed temperature-controlled environment for the sample and reduces the impact on X-ray penetration when X-ray detection is required; the liquid nitrogen cryogenic vaporization spray module provides a low-temperature environment or rapid cooling capability; and the semiconductor Peltier precision cooling and heating array allows for precise cooling or heating adjustment of the ambient temperature. With this configuration, the linkage intervention module can adaptively adjust the mechanical load and ambient temperature in real time based on the state determination results, or latch the corresponding state when necessary.

[0046] The weak acoustic emission voltage signal output by the preamplifier can be input to the field-programmable gate array (FPGA) for high-speed processing. Amplifying the microvolt-level acoustic emission voltage signal by the preamplifier facilitates subsequent identification and computation by the digital processing unit. The FPGA can serve as a low-level high-speed data processing node, performing parallel splitting and rapid processing of the input signal. The data stream entering the FPGA can be split into at least two paths in parallel. One path can be transmitted to a host computer via a bus for data storage, display, or subsequent analysis; the other path can directly enter the frequency domain analysis and processing link in the hardware logic without leaving the chip. As one implementation, this frequency domain analysis and processing link can employ a Fast Fourier Transform (FFT) pipeline embedded in the hardware logic to perform frequency domain transformation on the acoustic emission signal and extract corresponding features. By setting the data storage path and the fast analysis path in parallel, the original or processed signal data can be retained on the one hand, and the processing path from signal input to feature output can be shortened on the other hand. This is conducive to the feature analysis module obtaining the frequency band energy distribution characteristics and the instantaneous change rate of the main frequency drift in a timely manner, and to the state determination module further determining the damage evolution stage and critical failure precursor of the microcracks inside the rock and soil mass.

[0047] like Figure 2 The image shows a schematic diagram illustrating the principle of an acoustic emission signal feature analysis algorithm for a system designed for analyzing acoustic emission signals of freeze-thaw damage in soil and rock masses. Figure 3 The diagram illustrates a two-stage linkage intervention closed-loop control and timing sequence of an acoustic emission signal analysis system for freeze-thaw damage in soil and rock. In the energy distribution analysis unit of the feature analysis module, within a set sliding analysis time window of fixed duration, the system separates the high-frequency and low-frequency energy of the acoustic emission signal, calculates the relative proportion of low-frequency energy to the total energy of the entire frequency band, and uses this as the frequency band energy distribution characteristic characterizing soil and rock damage. This analysis process can be expressed by the following formula:

[0048]

[0049]

[0050] in, To analyze the time The cumulative value of low-frequency acoustic emission energy within the sliding time window at the endpoint. To define the cutoff frequency threshold for distinguishing between high-frequency and low-frequency energy, For acoustic emission signals at the analysis time A specific frequency within a sliding time window as the endpoint The power spectral density value at that location, To analyze the time The total accumulated energy of the full-band acoustic emission signal within the sliding time window ending at the endpoint. The highest effective analysis frequency boundary, To analyze the time The relative scaling factor within the sliding time window ending at a certain point. It should be noted that the sliding time window mentioned above specifically refers to a time length of... The sliding time window. It should be noted that... The specific value can be adaptively set based on the reciprocal of the minimum effective frequency resolution required for the system to perform a fast Fourier transform. The cutoff frequency threshold is set to forcibly distinguish between high-frequency and low-frequency energy. The cutoff frequency threshold is determined by conducting basic acoustic emission compression pre-experiments on similar soil and rock samples and statistically analyzing the signal spectrum characteristics of the pre-rupture stage.

[0051] Simultaneously, the dominant frequency drift tracking unit in the feature parsing module tracks the dominant frequency that causes the power spectral density to reach its global maximum within the sliding analysis time window, and extracts the instantaneous rate of change of the dominant frequency over time. This extraction process can be expressed by the following formula:

[0052]

[0053] in, The frequency value that maximizes the power spectral density, i.e., the dominant frequency. The dominant frequency at the previous sampling analysis time. The time step interval between two consecutive feature parsing operations performed by the feature parsing module. To analyze the time The instantaneous rate of change of the dominant frequency drift within the sliding time window ending at the endpoint. It should be noted that... The specific value can be obtained by taking the reciprocal of the acoustic emission signal sampling frequency set by the underlying hardware and the preset downsampling factor. Multiplication to obtain, downsampling factor The setting is based on the ratio of the maximum processing clock frequency of the field-programmable gate array to the original signal sampling frequency, rounded down.

[0054] Based on the feature parameters extracted from the underlying hardware, the state determination module determines the internal damage evolution stage of the soil and rock mass in real time. When the measured instantaneous rate of change of the dominant frequency drift is negative, and its absolute value exceeds the preset critical threshold for the negative drift rate of the dominant frequency... This indicates that the microcracks have undergone a large-scale accumulation and transformation from a tensile mode to a shear mode. At this time, the linkage intervention module generates physical intervention commands, issuing real-time control rate command values ​​to the micron-level fully digital closed-loop mechanical servo frame based on the following method: Based on the degree to which the absolute value of the instantaneous rate of change of the dominant frequency drift exceeds the preset critical threshold for the negative drift rate of the dominant frequency at the current analysis moment, the basic benchmark mechanical loading rate set before the compensation mechanism is triggered is reduced and adjusted. This generates a real-time control rate command value for the mechanical load applied to the soil and rock mass, serving as a physical intervention command for real-time adaptive adjustment of the mechanical load applied to the soil and rock mass, thus triggering the compensation mechanism. The greater the degree to which the absolute value of the instantaneous rate of change of the dominant frequency drift exceeds the critical threshold for the negative drift rate of the dominant frequency, the greater the magnitude of the rate reduction adjustment. It should be noted that the basic benchmark mechanical loading rate set before the compensation mechanism is triggered... The standard static compression test specifications for this type of rock and soil can be set according to the guidelines recommended by the International Society for Rock Mechanics. The analysis time... t The instantaneous rate of change of the dominant frequency drift within the sliding time window ending at the endpoint To track the main frequency The value calculated over time at the current analysis time The instantaneous rate of change of the dominant frequency drift and the critical threshold of the negative drift rate of the dominant frequency are obtained by performing conventional constant rate loading rupture pre-experiments on soil and rock samples of the same batch and statistically analyzing the average rate of change of the dominant frequency before the critical rupture.

[0055] Furthermore, to achieve precise locking of the microstructure of the soil and rock mass on the eve of critical failure, the state determination module also employs a joint determination mechanism to determine whether the soil and rock mass has entered a state of macroscopic pre-fracture. Specifically, this determination occurs if and only if within a continuous preset analysis period... Within this, the calculated relative proportion of low-frequency energy to the total energy across the entire system frequency band is determined. Exceeding the preset warning threshold for low-frequency energy ratio And the calculated cumulative value of total acoustic emission energy across the entire frequency band. Greater than the system's pre-calibrated environmental background noise shielding baseline When the state of macroscopic rupture is determined, the emergency latching intervention mode is triggered by the linkage intervention module.

[0056] Among them, the preset analysis period The time span for continuous reliability verification based on the underlying state determination module is set to be 3 to 5 times the average duration of a single effective acoustic emission impact event, in order to filter out transient interference. Low-frequency energy proportion warning threshold. The environmental background noise shielding baseline was calibrated by statistical analysis of the proportion of sudden increases in low-frequency signals during the pre-fracture stage in similar rock pre-experiments; This is obtained by continuously collecting and calculating the average peak envelope of environmental noise energy across the entire frequency band when the system is stationary without any physical load applied.

[0057] This invention also proposes a method for analyzing acoustic emission signals caused by freeze-thaw damage in soil and rock masses. The following embodiment, based on the aforementioned system architecture, provides a complete operational calculation process including real-world example data. Taking a standard cylindrical water-saturated granite sample as an example, the process details the control method of this invention, mainly including the following steps: S101. Monitor the acoustic emission signals generated by the target soil and rock mass under the action of force-thermal coupling.

[0058] Upon system startup, the signal acquisition module (deployed as an ultra-wideband multi-channel acoustic emission acquisition array) captures stress wave signals released from microscopic damage within the granite sample in situ. The microvolt-level acoustic emission voltage signal, after being preamplified, is input to the field-programmable gate array (FPGA) of the underlying ultra-high-speed data stream processing and triggering center. The data stream does not leave the chip but directly enters the fast Fourier transform (FFT) pipeline embedded in the hardware logic.

[0059] S102. Using the preset feature analysis module, separate the frequency band energy and calculate the relative proportionality coefficient.

[0060] In the energy distribution analysis unit of the feature analysis module, the system separates the high-frequency and low-frequency energies of the acoustic emission signal within a set sliding analysis time window of fixed duration, and calculates the relative proportion coefficient of the low-frequency energy to the total energy of the system across the entire frequency band. This analysis process is expressed by the following formula:

[0061]

[0062]

[0063] For example, the calculation process in step S102 further includes the following steps: First, set the duration parameter of the sliding analysis time window. (i.e., 1 millisecond), cutoff frequency threshold limit Highest effective analysis frequency boundary Secondly, when the rack is stably loaded and running to the current analysis time... At that time, the system calculates the cumulative value of acoustic emission energy in the low-frequency band using definite integral. And the total cumulative energy of acoustic emission across the entire frequency band. Then, substitute the example data above into the relative proportion coefficient formula for calculation:

[0064] Finally, the output result is: The relative proportionality coefficient calculated at time [time]. for .

[0065] S103. Using a preset main frequency drift tracking unit, extract the instantaneous change rate of the main frequency drift.

[0066] Simultaneously, the dominant frequency drift tracking unit in the feature parsing module tracks the dominant frequency that causes the power spectral density to reach its global maximum within the sliding analysis time window, and extracts the instantaneous rate of change of the dominant frequency over time. This extraction process is expressed by the following formula:

[0067]

[0068] in, Main frequency, It is the instantaneous rate of change of the main frequency drift.

[0069] For example, the calculation process in step S103 further includes the following steps: First, the sampling frequency of the acoustic emission signal of the system's underlying hardware is set to... Downsampling Based on this, the time step interval is obtained. Secondly, in Node, the system extracts the previous sampling time ( That is, the main frequency of 2699.99s. and the current clock speed Then, substitute the example data above into the instantaneous rate of change formula for calculation:

[0070] Finally, the output result is: At time, the extracted instantaneous rate of change of the dominant frequency drift .

[0071] S104. Based on the instantaneous change rate of the main frequency drift, determine the damage evolution stage and generate physical intervention instructions.

[0072] Based on the feature parameters extracted from the underlying hardware, the state determination module determines the internal damage evolution stage of the soil and rock mass in real time. When the absolute value of the measured instantaneous change rate of the dominant frequency drift exceeds a preset critical threshold, the linkage intervention module generates a physical intervention command and issues a real-time control rate command value. The real-time control rate command value is determined in the following way: Based on the degree to which the absolute value of the instantaneous change rate of the dominant frequency drift exceeds the preset critical threshold of the negative drift rate of the dominant frequency, the basic benchmark mechanical loading rate set before the compensation mechanism is triggered is reduced and adjusted. This generates a real-time control rate command value for the mechanical load on the soil and rock mass, which serves as a physical intervention command to adaptively adjust the mechanical load applied to the soil and rock mass in real time, triggering the compensation mechanism. The greater the degree to which the absolute value of the instantaneous change rate of the dominant frequency drift exceeds the critical threshold of the negative drift rate of the dominant frequency, the greater the magnitude of the reduction and adjustment.

[0073] For example, the calculation process in step S104 further includes the following steps: First, set the basic reference mechanical loading rate before the compensation mechanism is triggered. Critical threshold for negative drift rate of main frequency And pre-determine the mechanical stiffness of the frame. Initial undamaged elastic modulus The system determines that... Time measured It is a negative value, and its absolute value Exceeding the critical threshold The large number of microcracks indicates a large-scale accumulation and transformation of microcracks from tensile to shear types.

[0074] Finally, the output result is: the real-time control rate command value issued by the system to the micron-level all-digital closed-loop mechanical servo rack. The instantaneous deceleration effectively mitigated sudden slippage instability of the shear surface.

[0075] S105. A joint judgment mechanism is adopted to trigger the emergency latching intervention mode.

[0076] Furthermore, in order to accurately lock in the microstructure of the rock on the eve of critical failure, the state determination module also adopts a joint determination mechanism to determine whether the rock and soil mass has entered the pre-macroscopic fracture state.

[0077] For example, the calculation process in step S105 further includes the following steps: First, set a continuous preset analysis period. The system's pre-calibrated environmental background noise shielding baseline Low-frequency energy ratio warning threshold Secondly, when the loading process progresses to the point of facing a complete macroscopic fracture... At that time, the system recalculated and obtained the accumulated value of acoustic emission energy in the low-frequency band. Total cumulative acoustic emission energy across the entire frequency band Then, the system calculates the relative proportionality coefficient. Finally, the logical decision is executed, based on the calculated... Much greater than the set warning threshold And the current total energy across the entire frequency band Much greater than the ambient background noise The joint judgment conditions are met simultaneously.

[0078] Output result: The linkage intervention module immediately triggers the "emergency latching intervention mode," and the high-speed optocoupler isolation output terminal of the field-programmable gate array directly generates a physical emergency stop level signal, forcing the zero-displacement control rate command (i.e., The ambient temperature cycle control was cut off, and the PID constant temperature fine-tuning was started, thereby achieving rigid latching of the sample's microstructure a few milliseconds before macroscopic crushing and damage occurred.

[0079] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0080] From the above description of the embodiments, those skilled in the art will clearly understand that the present invention can be implemented in hardware, firmware, or a combination thereof. When implemented in software, the above-described functions can be stored in a computer-readable medium or transmitted as one or more instructions or code on a computer-readable medium. Computer-readable media include computer storage media and communication media, wherein communication media include any medium that facilitates the transmission of a computer program from one place to another. Storage media can be any available medium accessible to a computer. For example, but not limited to, computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible to a computer. Furthermore, any connection can suitably be considered a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of the medium. As used in this invention, disk and disc include compressed optical discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, wherein disks typically magnetically copy data, while discs optically copy data using lasers. The combinations described above should also be included within the scope of protection for computer-readable media.

[0081] In summary, the above description is merely a preferred embodiment of the technical solution of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A system for analyzing acoustic emission signals of freeze-thaw damage in soil and rock masses, characterized in that, include: The signal acquisition module is used to capture acoustic emission signals generated by soil and rock under force-thermal coupling in real time. The feature analysis module is used to perform frequency domain analysis on the acoustic emission signal and extract the frequency band energy distribution characteristics and the instantaneous change rate of the dominant frequency drift to characterize the freeze-thaw damage of the rock and soil. The state determination module is used to determine the damage evolution stage and critical failure precursor of the microcracks inside the rock and soil mass based on the frequency band energy distribution characteristics and the instantaneous change rate of the dominant frequency drift. The linkage intervention module is used to generate physical intervention commands based on the damage evolution stage and critical failure precursors; the physical intervention commands are used to adaptively adjust or lock the mechanical load and ambient temperature applied to the rock and soil in real time.

2. The acoustic emission signal analysis system for freeze-thaw damage of soil and rock mass according to claim 1, characterized in that: The signal acquisition module includes an ultra-wideband multi-channel acoustic emission acquisition array; The linkage intervention module performs real-time adaptive adjustment or state latching through a micron-level fully digital closed-loop mechanical servo rack and an ultra-wide temperature range multi-phase change environment coupling control box.

3. The acoustic emission signal analysis system for freeze-thaw damage of soil and rock mass according to claim 1, characterized in that, The feature parsing module includes: The energy distribution analysis unit is used to separate the high-frequency energy and low-frequency energy of the acoustic emission signal within a sliding analysis time window, and calculate the relative proportion coefficient of the low-frequency energy to the total energy of the entire frequency band as the frequency band energy distribution feature. The main frequency drift tracking unit is used to track the main frequency that makes the power spectral density reach the global maximum value within the sliding analysis time window, and extract the instantaneous change rate of the main frequency with time as the instantaneous change rate of the main frequency drift.

4. The acoustic emission signal analysis system for freeze-thaw damage of soil and rock mass according to claim 3, characterized in that, The method for calculating the relative proportion of low-frequency energy to the total energy of the entire frequency band includes: in, To analyze the time The cumulative value of low-frequency acoustic emission energy within the sliding time window at the endpoint. To define the cutoff frequency threshold for distinguishing between high-frequency and low-frequency energy, For acoustic emission signals at the analysis time A specific frequency within a sliding time window as the endpoint The power spectral density value at that location, To analyze the time The total accumulated energy of the full-band acoustic emission signal within the sliding time window ending at the endpoint. The highest effective analysis frequency boundary, To analyze the time The relative scaling factor within the sliding time window ending at the endpoint.

5. The acoustic emission signal analysis system for freeze-thaw damage of soil and rock mass according to claim 3, characterized in that, The method for calculating the instantaneous rate of change of the dominant frequency drift includes: in, To analyze the time The frequency that maximizes the power spectral density within a sliding time window ending at the endpoint, i.e., the dominant frequency. To analyze the time The frequency value that maximizes the power spectral density within the sliding time window ending at the endpoint. The time step interval between two consecutive feature parsing operations performed by the feature parsing module. To analyze the time The instantaneous rate of change of the dominant frequency drift within the sliding time window with the endpoint as the endpoint.

6. The acoustic emission signal analysis system for freeze-thaw damage in soil and rock mass according to claim 1, characterized in that, A method for determining the damage evolution stage of microcracks within the soil and rock mass includes: If a deterministic negative drift is continuously detected in the instantaneous rate of change of the dominant frequency drift, and the absolute value of the instantaneous rate of change of the dominant frequency drift exceeds the preset critical threshold for the negative drift rate of the dominant frequency, then it is determined that the microcracks inside the rock and soil mass are undergoing a substantial transformation from the tension mode to the shear mode. Methods for determining the precursors of critical damage include: A joint judgment mechanism is adopted. When the frequency band energy distribution characteristics exceed the preset low frequency band energy ratio warning threshold within a continuous preset analysis period, and the total energy of the entire frequency band is greater than the pre-calibrated environmental background noise shielding baseline, it is determined that the soil and rock mass has entered the macroscopic critical failure precursor stage.

7. The acoustic emission signal analysis system for freeze-thaw damage in soil and rock mass according to claim 6, characterized in that, When it is determined that the microcracks inside the soil and rock mass are undergoing a substantial transition from a tension mode to a shear mode, the basic benchmark mechanical loading rate set before the compensation mechanism is triggered is reduced based on the degree to which the absolute value of the instantaneous change rate of the dominant frequency drift exceeds the preset critical threshold of the negative dominant frequency drift rate. This generates a real-time control rate command value for the mechanical load on the soil and rock mass, which serves as a physical intervention command for real-time adaptive adjustment of the mechanical load applied to the soil and rock mass, triggering the compensation mechanism. The greater the degree to which the absolute value of the instantaneous change rate of the dominant frequency drift exceeds the critical threshold of the negative dominant frequency drift rate, the greater the magnitude of the rate reduction adjustment.

8. The acoustic emission signal analysis system for freeze-thaw damage of soil and rock mass according to claim 6, characterized in that, When it is determined that the soil and rock mass has entered a macroscopic critical failure precursor stage, the method for generating the physical intervention command includes: The emergency latching intervention mode is triggered, the displacement control rate command is forced to zero to lock the mechanical displacement, the ambient temperature cycle control is cut off, and the PID constant temperature fine-tuning is started to keep the current ambient temperature constant, thereby realizing the latching of the microstructure state of the soil and rock mass before critical failure.

9. The acoustic emission signal analysis system for freeze-thaw damage in soil and rock mass according to claim 8, characterized in that, When the emergency latching intervention mode is triggered, a physical emergency stop level signal is generated by the high-speed optocoupler isolation output terminal of the field programmable gate array and transmitted along the hardwire to the interrupt terminal of the control system for mechanical load and ambient temperature.

10. A method for analyzing acoustic emission signals of freeze-thaw damage in rock and soil, characterized in that, include: Real-time capture of acoustic emission signals generated by soil and rock masses under force-thermal coupling; Frequency domain analysis was performed on the acoustic emission signal to extract the frequency band energy distribution characteristics and the instantaneous change rate of the dominant frequency drift, which are used to characterize the freeze-thaw damage of rock and soil. Based on the frequency band energy distribution characteristics and the instantaneous change rate of the dominant frequency drift, the damage evolution stage and critical failure precursor of the microcracks inside the rock and soil mass are determined. Based on the damage evolution stage and critical failure precursors, physical intervention commands are generated; these commands are used to adaptively adjust or lock the mechanical loads and ambient temperature applied to the soil and rock mass in real time.

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