A tunnel surrounding rock state monitoring device and method based on a piezoelectric intelligent anchor rod

Abstract

The application relates to the technical field of tunnel monitoring, and relates to a tunnel surrounding rock state monitoring device and method based on a piezoelectric intelligent anchor rod. The device comprises an anchor rod unit and a sensing unit. The anchor rod unit is arranged on the tunnel surrounding rock in the form of a rectangular array. The anchor rod unit comprises four wave-emitting anchor rods and one wave-receiving anchor rod. The wave-receiving anchor rod is arranged at the center of the rectangle, and the four wave-emitting anchor rods are arranged at the four vertices of the rectangle. The sensing unit is arranged inside the wave-receiving anchor rod and the wave-emitting anchor rod. The sensing unit is used for monitoring the surrounding rock structure damage. The application can expand the monitoring range from a single point to an area. The active sensing principle is used to sensitively capture the wave propagation characteristic change caused by the early damage such as micro-cracks and looseness in the surrounding rock, so that early warning can be realized before macroscopic deformation occurs.

Description

Technical Field

[0001] This invention relates to the field of tunnel monitoring technology, and more specifically, to a tunnel surrounding rock condition monitoring device and method based on piezoelectric smart anchors. Background Technology

[0002] With the rapid development of infrastructure construction in my country, such as transportation, water conservancy, and energy, the number and scale of tunnels and underground projects have continued to grow, and the long-term stability and operational safety of tunnel projects have received increasing attention. After excavation, the stress state of the surrounding rock in tunnels undergoes redistribution and is affected by multiple factors during operation, including changes in geological conditions, groundwater infiltration, and cyclic loading. This makes it prone to problems such as loosening, crack propagation, and even instability, necessitating effective monitoring methods for early warning. Currently, traditional monitoring methods mainly rely on point-based or superficial monitoring methods such as surface convergence measurement, multi-point displacement gauges, and pressure cells. These methods are insufficient to comprehensively and timely reflect the stress state and damage evolution process deep within the surrounding rock, and suffer from limitations such as limited monitoring range and delayed response. Although some technologies attempt to obtain surrounding rock parameters through locally buried sensors, they still cannot achieve real-time, three-dimensional perception of the internal state of a large area of ​​surrounding rock, and are susceptible to interference and have low reliability, failing to meet the needs of intelligent tunnel operation and maintenance for early damage identification and precise location. Summary of the Invention

[0003] The purpose of this invention is to provide a tunnel surrounding rock condition monitoring device and method based on piezoelectric smart anchors to improve the aforementioned problems. To achieve the above objective, the technical solution adopted by this invention is as follows: On one hand, this application provides a tunnel surrounding rock condition monitoring device based on piezoelectric smart anchors, including: an anchor unit and a sensing unit. The anchor unit is arranged in a rectangular array on the tunnel surrounding rock. The anchor unit includes four wave-generating anchors and one wave-receiving anchor. The wave-receiving anchor is located at the center of the rectangle, and the four wave-generating anchors are located at the four vertices of the rectangle. The sensing unit is located inside the wave-receiving anchor and the wave-generating anchor, and the sensing unit is used to monitor the damage to the surrounding rock structure.

[0004] On the other hand, this application provides a method for monitoring the surrounding rock condition of tunnels based on piezoelectric smart anchors, the method comprising: Acquire raw wave signal data collected by each sensing unit within the monitoring area; Based on the original wave signal data, signal feature extraction processing is performed to obtain signal feature index information; Based on the signal characteristic index information, a preliminary diagnosis of the regional health status is performed to obtain a preliminary location unit with potential damage; The damage area is precisely located based on the preliminary positioning unit to obtain the specific spatial location of the damage. Based on the specific spatial location of the damage, the proximity of the damaged anchor rod is determined to obtain the spatial proximity relationship between the damage and the specific anchor rod.

[0005] The beneficial effects of this invention are as follows: This invention employs anchor units arranged in a rectangular array, with four wave-generating anchors at the vertices and one wave-receiving anchor at the center of each unit. A three-dimensional, intersecting monitoring network is constructed using sensing units integrated within the anchors. This layout allows stress waves to propagate through the surrounding rock medium between the wave-generating and wave-receiving anchors. By extracting wave velocity, energy, and spectral characteristics from the received raw wave signal data, comprehensive perception of damage to the surrounding rock structure is achieved. This invention extends the monitoring range from a single point to a region, sensitively capturing changes in wave propagation characteristics caused by early damage such as microcracks and loosening within the surrounding rock using active sensing principles, thus providing early warning before macroscopic deformation occurs. Furthermore, integrating the sensing function into the support anchor body forms an integrated support-sensing structure, which requires no additional space and is economical and reliable.

[0006] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing embodiments of the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0007] 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.

[0008] Figure 1 This is a schematic diagram of the tunnel surrounding rock condition monitoring device based on piezoelectric smart anchor bolts as described in an embodiment of the present invention.

[0009] Figure 2 This is a schematic diagram of the sensing unit structure.

[0010] Figure 3 This is a schematic diagram of the sensor unit layout.

[0011] The markings in the diagram are: 1. Nut; 2. Washer; 3. Grout stopper; 4. Second sensing unit; 5. Hollow anchor rod body; 6. First sensing unit; 7. Anchor head; 401. Tubular piezoelectric sensor; 402. Protective layer; 403. Wire; 404. Piezoelectric sheet. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present 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 present invention without inventive effort are within the scope of protection of the present invention.

[0013] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0014] Example 1 like Figure 1 , Figure 2 and Figure 3As shown, this embodiment provides a tunnel surrounding rock condition monitoring device based on piezoelectric smart anchors, including: anchor units and sensing units. The anchor units are arranged in a rectangular array on the tunnel surrounding rock. Each anchor unit includes four wave-generating anchors and one wave-receiving anchor. The wave-receiving anchor is located at the center of the rectangle, and the four wave-generating anchors are located at the four vertices of the rectangle. The sensing units are located inside the wave-receiving and wave-generating anchors and are used to monitor damage to the surrounding rock structure. In the surrounding rock of the tunnel monitoring area, multiple piezoelectric smart anchors are installed in a rectangular array as basic sensing units. Each basic unit consists of five anchors—four wave-generating anchors precisely positioned at the four vertices of the rectangle, and one wave-receiving anchor positioned at the geometric center of the rectangle. This arrangement forms a cross-monitoring network in the surrounding rock, radiating from the center point to the four vertices and containing four independent propagation paths. Each anchor, whether a wave-generating or wave-receiving anchor, has a sensing unit encapsulated inside its shaft. In actual monitoring, a stress wave is generated by an electrically excited sensing unit within one of the wave-generating anchor bolts. This stress wave is transmitted into the rock mass through the coupling interface between the anchor bolt and the surrounding rock, and propagates along a straight path to the receiving anchor bolt located at the center of the unit, where it is received by the sensing unit inside. By sequentially exciting the wave-generating anchor bolts at the four vertices, four sets of wave propagation signals traversing different areas of the surrounding rock within the rectangular unit can be obtained. For scenarios like tunnel engineering, where the internal damage is difficult to directly observe due to its highly concealed nature, this invention analyzes and compares the changes in signal characteristics of stress waves after propagation along different paths. This allows for the inversion of the physical and mechanical state of the surrounding rock along the wave propagation path. When the surrounding rock experiences damage such as loosening or fissure development, it significantly hinders the propagation of stress waves, resulting in identifiable anomalies in the received signals. This point-to-surface layout elevates traditional single-point monitoring to a comprehensive health assessment of an entire surrounding rock area. It is particularly suitable for capturing the initiation and development of potential, unevenly distributed damage within the surrounding rock, providing key technical support for the early and accurate diagnosis of tunnel support structures.

[0015] In one specific embodiment of this disclosure, the wave-collecting anchor bolt includes a nut 1, a washer 2, a grout stopper 3, a hollow anchor bolt body 5, and an anchor head 7. The nut 1 and the anchor head 7 are respectively located at both ends of the hollow anchor bolt body 5. The grout stopper 3 is sleeved on the hollow anchor bolt body 5 and located at the bottom of the nut 1. The washer 2 is located between the grout stopper 3 and the nut 1. The wave-collecting anchor bolt mainly uses the hollow anchor bolt body 5 as the core load-bearing and force-transmitting component. Its two ends are respectively connected to the nut 1 and the anchor head 7 by threads, thereby tensioning and anchoring the anchor bolt in the surrounding rock borehole. During installation, the anchor bolt body 5 with the grout stopper 3 and the washer 2 is placed into the borehole. The grout stopper 3 is located at the borehole opening, and its function is to seal the borehole opening during grouting to prevent grout from flowing out and ensure that the entire length of the anchor bolt is wrapped with mortar to achieve full-length bonding. The washer 2 is placed between the grout stopper 3 and the nut 1 to evenly distribute the pressure when tightening the nut 1, protect the grout stopper 3, and ensure that the anchor bolt has an appropriate preload. The installation methods for wave-generating anchors and wave-receiving anchors are the same, so they will not be described in detail here.

[0016] In one specific embodiment of this disclosure, the sensing unit includes a first sensing unit 6 and a second sensing unit 4. Both the first sensing unit 6 and the second sensing unit 4 are disposed inside the hollow anchor body 5. The first sensing unit 6 is disposed at one end near the anchor head 7, and the second sensing unit 4 is disposed at one end near the grout stop plug 3. This embodiment employs a strategy of placing two sensing units on one anchor to address the characteristic that tunnel surrounding rock damage may have depth differences. Since the propagation energy of stress waves in the rock mass attenuates with distance, and surrounding rock at different depths may be in different stress states or damage stages, placing the two sensing units at the head and tail of the anchor respectively allows for monitoring of the deep and shallow layers of the tunnel, greatly improving the dimensionality of monitoring and the accuracy of diagnosis.

[0017] In one specific embodiment of this disclosure, the sensing unit includes a piezoelectric module, a protective layer 402, a wire 403, and a piezoelectric sheet 404. The protective layer 402 is disposed on the outside of the piezoelectric module, and the piezoelectric sheet 404 is disposed on the bottom of the piezoelectric module. Both the piezoelectric module and the piezoelectric sheet 404 are electrically connected to the wire 403. The piezoelectric module includes two tubular piezoelectric sensors 401, which are overlapped and nested together. Two circular tubular piezoelectric ceramic elements with slightly different sizes are fabricated, with the outer diameter of one tube matching the inner diameter of the other. Subsequently, the smaller tubular sensor is tightly nested inside the larger tubular sensor, so that their central axes coincide, forming a composite structure. Finally, this overlapped assembly is encapsulated and cured with the protective layer 402. Due to the high energy requirements of stress wave excitation in tunnel scenarios, the vibration energy and directionality generated by a single tubular piezoelectric sensor when exciting stress waves are limited. When two tubular sensors are synchronously excited, their vibrations superimpose, significantly enhancing the amplitude and energy of the excitation signal. This allows the emitted stress wave to propagate over greater distances and penetrate a wider area of ​​surrounding rock. Simultaneously, in receiving mode, both sensors jointly sense mechanical vibrations and convert them into electrical signals. The output signal is the superposition of their induced voltages, effectively increasing the effective sensing area and enabling the capture of weaker wave signals, thus significantly improving receiving sensitivity. This is particularly suitable for deep rock monitoring scenarios in tunnels requiring long-distance, high-reliability signal transmission.

[0018] In one specific embodiment of this disclosure, a common wave-generating anchor exists between two adjacent anchor units. When planning the installation positions of anchors in the tunnel monitoring section, instead of independently and isolatedly arranging five anchors for each rectangular monitoring unit, an optimized grid-based layout strategy is adopted. Multiple rectangular units are arranged in a checkerboard or honeycomb pattern on the plane, such that a vertex of one rectangular unit (i.e., the location of a wave-generating anchor) simultaneously becomes a vertex of its adjacent rectangular unit. Thus, the anchor is shared by two (or even more) monitoring units. During monitoring, when an evaluation of a specific unit is required, the common anchor is activated as a wave-generating anchor, and its signal can be received by the central receiving anchors of its respective units, thereby participating in the damage diagnosis of multiple units. The unique effect of this design is that it greatly improves the utilization efficiency of anchor resources and the density of the monitoring network without linearly increasing the number of anchors. In scenarios requiring comprehensive monitoring of large-scale tunnel linings, this shared approach allows for the construction of a denser network of intersecting monitoring paths using fewer anchor bolts. Each receiving anchor bolt can receive signals from multiple directions, providing a more three-dimensional understanding of the surrounding rock. This not only significantly reduces the system's hardware costs and installation workload but, more importantly, enhances the robustness and reliability of the monitoring network. Because signals acquired by a single common anchor bolt can serve the analysis of multiple units, even if there is accidental interference on a particular path within a unit, its impact can be diluted or corrected by data from other paths, avoiding misjudgments caused by single-point signal anomalies and ensuring the accuracy and stability of the overall monitoring system's evaluation results.

[0019] Example 2 This embodiment provides a method for monitoring the surrounding rock condition of tunnels based on piezoelectric smart anchors. The method includes steps S1-S5, specifically including: Step S1: Acquire the raw wave signal data collected by each sensing unit within the monitoring area; Step S2: Perform signal feature extraction processing based on the original wave signal data to obtain signal feature index information; Step S2 further includes steps S21-S24, which specifically include: Step S21: Perform wave velocity calculation processing based on the original wave signal data to obtain wave velocity index information; Wave velocity, as a fundamental physical quantity, is calculated based on the ratio of wave propagation distance to time. When damage occurs inside the surrounding rock, such as the initiation or expansion of cracks, it will lead to a decrease in rock mass stiffness, an increase in the effective length of the stress wave propagation path, or a decrease in wave velocity. It can provide the most direct evidence for assessing the deterioration of the macroscopic mechanical parameters of the rock mass, and is especially suitable for identifying early, distributed damage caused by stress relaxation or material softening.

[0020] Step S22: Perform energy calculation processing based on the original wave signal data to obtain energy index information; This step focuses on analyzing the degree of energy attenuation of stress waves after they pass through the surrounding rock, reflecting the energy loss caused by mechanisms such as scattering and absorption during wave propagation. When there are discontinuities (such as fissures and joints) inside the surrounding rock or when the material becomes loose, stress waves will encounter more interfaces and be scattered, resulting in a significant reduction in the energy of the signal at the receiving end. By calculating the energy integral of the received signal in the time domain, this attenuation effect can be quantified, effectively revealing the changes in wave impedance and energy dissipation characteristics caused by damage.

[0021] Step S23: Perform spectrum analysis processing on the original wave signal data to obtain center frequency index information; By converting the time-domain signal to the frequency domain and extracting the center frequency, the filtering effect of damage on the frequency components of the stress wave can be revealed. Healthy rock masses have specific propagation characteristics for different frequency components in stress waves. When damage occurs, the rock mass acts as a filter, often preferentially attenuating or scattering high-frequency components, causing the center frequency of the received signal to shift towards lower frequencies. This change in frequency domain characteristics does not depend on the absolute amplitude and is relatively less affected by environmental noise. It is particularly adept at capturing overall material damage caused by changes in microstructure (such as weakening of intergranular cementation).

[0022] Step S24: Perform feature set construction processing based on the wave velocity index, energy attenuation index and center frequency index to obtain the signal feature index information.

[0023] Step S3: Perform preliminary diagnosis of regional health status based on the signal characteristic index information to obtain preliminary location units with potential damage; Step S3 further includes steps S31-S34, which specifically include: Step S31: Calculate the damage index of each path in the anchor unit based on the signal characteristic index information to obtain the damage index of each signal propagation path; In this step, the damage index is calculated as follows:

[0024] In the above formula, This represents the damage index of the j-th path in the i-th unit during the k-th monitoring period; , as well as These represent the wave velocity attenuation, energy attenuation, and center frequency shift of the j-th path within the i-th cell during the k-th period, respectively. , and These represent the weighting coefficients corresponding to wave velocity attenuation, energy attenuation, and center frequency shift, respectively. It should be noted that in this application, the weighting coefficients are 0.3, 0.5, and 0.2, respectively. Wave velocity attenuation, energy attenuation, and center frequency shift are obtained by subtracting the initial values ​​from the actual measured values ​​under lossless conditions.

[0025] Based on multidimensional characteristic indicators such as wave velocity, energy, and center frequency, a comprehensive damage index is calculated through weighted fusion, which avoids the randomness and one-sidedness that may exist in a single indicator. Through weighted fusion, physical observations on multiple paths are unified into comparable scalar values, thereby transforming complex differences in wave signals into intuitive values ​​that characterize the health status of the path, and realizing the preliminary quantification from signal characteristics to damage probability.

[0026] Step S32: Calculate the comprehensive anomaly degree of each anchor unit based on the damage index and the geometric distance of the corresponding propagation path. In this step, the specific calculation process for the comprehensive anomaly index is as follows:

[0027] In the above formula, This represents the overall anomaly degree of the i-th unit in the k-th monitoring period; This represents the propagation distance of the j-th channel within the i-th unit. This step shifts the focus from a single path to a holistic assessment of the overall health of the entire monitoring unit area. In a monitoring unit composed of multiple paths, if damage is located within the unit, its impact is not isolated but will affect multiple or even all propagation paths within the unit to varying degrees. Therefore, this step does not simply average the damage indices of each path, but introduces the geometric distance of each path as a weighting factor in the calculation. Paths with longer propagation distances carry richer information about the surrounding rock condition and are given higher weight in the overall assessment. This weighted aggregation strategy fully considers the attenuation characteristics of damage signals during spatial propagation and the differences in sensitivity of different paths to the coverage of the unit's internal area, enabling the final comprehensive anomaly index of the unit to more scientifically and robustly reflect the overall anomaly level of the entire surrounding rock area covered by the unit.

[0028] Step S33: Determine the abnormal unit based on the comprehensive anomaly index of each anchor bolt unit, and obtain the determination result; This step compares the calculated comprehensive anomaly index of each unit with a preset theoretical threshold. If the comprehensive anomaly index of a unit does not exceed the threshold, the surrounding rock within the unit's coverage area is considered to be in a relatively stable or healthy state. If the index significantly exceeds the threshold, it indicates that the area represented by the unit has a high risk of damage and requires attention. The system automatically filters out areas requiring further refined monitoring from the large amount of data generated by continuous monitoring, greatly improving monitoring efficiency.

[0029] Step S34: Determine the set of preliminary positioning units that need to be finely evaluated based on the judgment results.

[0030] Step S4: Accurately locate the damaged area based on the preliminary positioning unit to obtain the specific spatial location of the damage; Step S4 further includes steps S41-S44, which specifically include: Step S41: Based on the preliminary positioning unit, perform fine measurement area determination processing. By defining the unit and its adjacent units as a new monitoring range, the anchor bolt unit to be finely measured is obtained. Step S42: By activating the first sensing unit 6, the deep surrounding rock condition assessment of the anchor bolt unit to be precisely measured is performed to obtain the damage information of the deep surrounding rock. This step targets the anchor bolts within the area to be precisely measured. It activates the first sensing unit 6, installed near the anchor head 7. The stress waves emitted or received by this unit primarily traverse the deeper rock mass in front of the anchor bolt. By analyzing the wave velocity, energy, and other characteristic indicators of the signal along this path, the density and integrity of the deep surrounding rock far from the tunnel wall can be assessed. This method effectively detects deep loosening or plastic zones originating from the core area of ​​surrounding rock stress redistribution that have not yet manifested on the surface, providing crucial depth-based information for assessing the severity of damage and potential risks. It should be noted that this application uses a surrounding rock condition assessment model to evaluate the surrounding rock condition. The training process of the surrounding rock condition assessment model includes: Step 1: Prepare standard specimens and establish a baseline state. First, process concrete or rock specimens of the same length as the spacing between the anchor bolts in the field. Cast short steel pipe sections with built-in sensing units at both ends of these specimens to accurately simulate the coupling state between the anchor bolts and the surrounding rock. Then, perform initial monitoring on all specimens to obtain the baseline wave velocity, energy, and center frequency, among other wave signal characteristics, under healthy conditions. Samples are then taken for mechanical testing to measure fundamental mechanical parameters such as density, elastic modulus, and compressive strength, establishing an initial, non-destructive reference baseline for model training.

[0031] Step Two: Applying Multi-Condition Damage and Acquiring Post-Damage Signals. Various physical methods (such as applying different levels of axial force, bending moment, and shear force, or subjecting the specimen to freeze-thaw cycles, wet-dry cycles, and dynamic impacts) are used to artificially intervene in the specimen, simulating different types and degrees of damage that tunnel surrounding rock may encounter in actual service. After each damage application, the sensing units at both ends of the specimen are re-excited for monitoring, acquiring the stress wave propagation fluctuation signal under damage conditions, and calculating indicators such as wave velocity attenuation, energy attenuation, and center frequency shift after damage.

[0032] Step 3: Determine post-damage mechanical parameters and construct a sample dataset. After acquiring signals for all damage conditions, destructive mechanical tests are performed on the specimens to accurately determine their actual mechanical parameters under various damage states, such as elastic modulus, compressive strength, and tensile strength after damage. At this point, a complete set of training data is generated for each specimen. Its input features are the changes in wave signal characteristics before and after damage (such as wave velocity attenuation), and its output labels are the corresponding mechanical parameter degradation amounts, thus constructing a sample database containing multiple damage modes.

[0033] Step 4: Perform curve fitting and model training to determine weight thresholds. Input the sample data constructed in Step 3 into the selected machine learning or statistical model for training. The core task is to establish a quantitative mapping relationship between changes in wave signal characteristics and the deterioration of mechanical parameters through curve fitting methods such as regression analysis, thereby determining the weights of each characteristic index (such as wave velocity, energy, and center frequency) when calculating the damage index. Simultaneously, based on the comprehensive anomaly of the sample at a specific degree of damage (such as a 10% decrease in compressive strength), determine the threshold for determining whether a unit is abnormal in the field, ultimately obtaining a predictive model that can accurately assess the degree of deterioration of the surrounding rock's mechanical state based on wave signals.

[0034] Step S43: By activating the second sensing unit 4, the shallow surrounding rock condition assessment of the anchor bolt unit to be precisely measured is performed to obtain the damage information of the shallow surrounding rock. This step involves activating the second sensing unit 4 installed near the grout stop plug 3. The stress wave propagation path corresponding to this unit mainly covers the shallow surrounding rock area from the tail to the middle of the anchor bolt. The shallow surrounding rock is most directly affected by the tunnel excavation disturbance and is prone to damage such as loosening and tensile cracking.

[0035] Step S44: Based on the assessment results of the shallow and deep surrounding rocks, perform spatial location processing of the damage to obtain the specific spatial location of the damage.

[0036] This step integrates damage information from both shallow and deep surrounding rock layers, and combines this with signal anomalies along multiple intersecting propagation paths within the precision measurement area to perform spatial correlation and inference. For example, if a shallow signal shows significant anomalies while a deep signal is relatively normal, it suggests the damage may be located in the shallow layer. If both shallow and deep signals show anomalies, and the degree of anomaly varies gradient, it may indicate that the damaged body has a certain depth and spatial orientation. Through this fusion of multi-source information and spatial interpolation analysis, abstract damage indicators are ultimately transformed into spatial descriptions of the specific location, approximate extent, and even development depth of the damaged body, achieving a leap from regional anomalies to three-dimensional localization.

[0037] Step S5: Based on the specific spatial location of the damage, perform a proximity judgment process on the damaged anchor rod to obtain the spatial proximity relationship between the damage and the specific anchor rod.

[0038] This step specifically includes: screening target anchors based on the specific spatial location of the damage; obtaining a list of anchors to be tested by identifying all anchors within the damaged unit; performing stress wave propagation analysis on a single anchor based on the list of anchors to be tested, obtaining the energy attenuation rate of the stress wave propagating along the anchor body by exciting the sensor at the head of a single anchor and receiving the signal at its tail; judging the proximity of the damage based on the energy attenuation rate, obtaining the spatial relationship between the damage and the anchor with the largest energy attenuation by comparing the magnitude of the energy attenuation rates of each anchor; and performing final location output processing based on the spatial relationship, obtaining the final spatial location result of the damage relative to the anchor support network by integrating all judgment information. Based on the determined specific spatial location of the damage, further analysis of indicators such as the energy attenuation relationship between the damage point and the nearest surrounding anchors is necessary because the effectiveness of anchors, as the main support components, is closely related to the integrity of the surrounding rock mass; when damage occurs in the vicinity of a certain anchor, the path of the stress wave from the head of the anchor to the tail will directly pass through the damaged body, resulting in a significant attenuation of the received signal energy. By calculating and comparing the energy attenuation rate of each adjacent anchor bolt, it is possible to determine which anchor bolt(s) is most closely related to the damage. This makes the diagnosis no longer an isolated case of damage, but rather a potential impact on the support effectiveness of the anchor bolts. This provides guidance for engineers to take measures such as targeted anchor bolt reinforcement and grouting.

[0039] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0040] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. 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.

[0042] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A tunnel surrounding rock condition monitoring device based on piezoelectric smart anchors, characterized in that, include: An anchor bolt unit is arranged in a rectangular array on the surrounding rock of the tunnel. The anchor bolt unit includes four wave-generating anchor bolts and one wave-receiving anchor bolt. The wave-receiving anchor bolt is located at the center of the rectangle, and the four wave-generating anchor bolts are located at the four vertices of the rectangle. A sensing unit is disposed inside the receiving anchor and the generating anchor, and the sensing unit is used to monitor damage to the surrounding rock structure.

2. The tunnel surrounding rock condition monitoring device based on piezoelectric smart anchor bolt according to claim 1, characterized in that: The wave-collecting anchor includes a nut (1), a washer (2), a grout stopper (3), a hollow anchor body (5), and an anchor head (7). The nut (1) and the anchor head (7) are respectively disposed at both ends of the hollow anchor body (5). The grout stopper (3) is sleeved on the hollow anchor body (5). The grout stopper (3) is disposed at the bottom of the nut (1). The washer (2) is disposed between the grout stopper (3) and the nut (1).

3. The tunnel surrounding rock condition monitoring device based on piezoelectric smart anchor bolt according to claim 2, characterized in that: The sensing unit includes a first sensing unit (6) and a second sensing unit (4). Both the first sensing unit (6) and the second sensing unit (4) are located inside the hollow anchor body (5). The first sensing unit (6) is located at one end near the anchor head (7), and the second sensing unit (4) is located at one end near the grout stop plug (3).

4. The tunnel surrounding rock condition monitoring device based on piezoelectric smart anchor bolt according to claim 1, characterized in that: The sensing unit includes a piezoelectric module, a protective layer (402), a wire (403), and a piezoelectric sheet (404). The protective layer (402) is disposed on the outside of the piezoelectric module, and the piezoelectric sheet (404) is disposed on the bottom of the piezoelectric module. Both the piezoelectric module and the piezoelectric sheet (404) are electrically connected to the wire (403).

5. The tunnel surrounding rock condition monitoring device based on piezoelectric smart anchor bolt according to claim 4, characterized in that: The piezoelectric module includes two tubular piezoelectric sensors (401), which are overlapped and nested together.

6. The tunnel surrounding rock condition monitoring device based on piezoelectric smart anchor bolt according to claim 1, characterized in that: There is a common wave-generating anchor between two adjacent anchor units.

7. A method for monitoring concrete damage based on piezoelectric active sensing, using the tunnel surrounding rock condition monitoring device based on piezoelectric smart anchors as described in claims 1-6, characterized in that, include: Acquire raw wave signal data collected by each sensing unit within the monitoring area; Based on the original wave signal data, signal feature extraction processing is performed to obtain signal feature index information; Based on the signal characteristic index information, a preliminary diagnosis of the regional health status is performed to obtain a preliminary location unit with potential damage; The damage area is precisely located based on the preliminary positioning unit to obtain the specific spatial location of the damage. Based on the specific spatial location of the damage, the proximity of the damaged anchor rod is determined to obtain the spatial proximity relationship between the damage and the specific anchor rod.

8. The concrete damage monitoring method based on piezoelectric active sensing according to claim 7, characterized in that, Signal feature extraction processing is performed based on the original wave signal data, including: Based on the original wave signal data, wave velocity calculation processing is performed to obtain wave velocity index information; Energy calculation processing is performed on the original wave signal data to obtain energy index information; The original wave signal data is subjected to spectrum analysis to obtain center frequency index information. The signal characteristic index information is obtained by constructing a feature set based on the wave velocity index, energy attenuation index, and center frequency index.

9. The concrete damage monitoring method based on piezoelectric active sensing according to claim 7, characterized in that, Based on the aforementioned signal characteristic index information, a preliminary diagnosis of the regional health status is performed, including: The damage index of each path in the anchor unit is calculated based on the signal characteristic index information to obtain the damage index of each signal propagation path; The comprehensive anomaly degree of each anchor bolt unit is calculated based on the damage index and the geometric distance of the corresponding propagation path. Anomalies are determined based on the comprehensive anomaly index of each anchor bolt unit, and the determination result is obtained. Based on the judgment results, a preliminary set of positioning units that require detailed evaluation is determined.

10. The concrete damage monitoring method based on piezoelectric active sensing according to claim 7, characterized in that, Accurate localization of the damaged area based on the preliminary localization unit includes: Based on the preliminary positioning unit, the fine measurement area is determined. By defining the unit and its adjacent units as a new monitoring range, the anchor bolt unit to be finely measured is obtained. By activating the first sensing unit (6), the deep surrounding rock condition assessment of the anchor bolt unit to be precisely measured is performed to obtain information on the damage status of the deep surrounding rock. By activating the second sensing unit (4), the shallow surrounding rock condition assessment of the anchor bolt unit to be precisely measured is performed to obtain information on the damage status of the shallow surrounding rock. Based on the assessment results of the shallow and deep surrounding rocks, spatial location processing of the damage is performed to obtain the specific spatial location of the damage.

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