Non-intrusive detection method for prefabricated cable well and related device

Abstract

The invention discloses a non-intrusive detection method and related device for a prefabricated cable well, and the method comprises the steps: calling a reference response feature of a well type to which a prefabricated cable well to be detected belongs, applying acoustic excitation to a well chamber, and collecting an acoustic response and a vibration response; extracting acoustic features and vibration features, and comparing the acoustic features and the vibration features with reference response features to judge whether abnormity exists or not; when the abnormality exists, determining a space region where the abnormality is located according to the acoustic features and the vibration features; applying directional excitation according to the spatial region and collecting directional response to obtain directional characteristics; and based on the acoustic characteristics, the vibration characteristics and the directional characteristics, performing grading evaluation on the in-well accumulated water deposition state and the well body structure integrity. According to the technical scheme, comprehensive detection of the internal environment and the structural state of the prefabricated cable well can be completed under the conditions that the prefabricated cable well does not enter the well and sensors are not arranged for a medium and long term, and spatial positioning and fine diagnosis of abnormal areas are achieved.

Description

Technical Field

[0001] This invention relates to the field of prefabricated cable well structural condition detection technology, and in particular to a non-invasive detection method, device, equipment and storage medium for prefabricated cable wells. Background Technology

[0002] Precast cable manholes are underground chambers typically manufactured in a factory according to standardized modules and drawings, either as a whole or in sections, and then assembled on-site using hoisting and connectors. They are used to house, connect, and maintain power or communication cables. Compared to cast-in-place concrete cable manholes and masonry cable manholes, precast cable manholes are highly standardized in terms of geometry, wall thickness, cover construction, and joint details. Component materials and reinforcement are subject to factory quality control, resulting in better batch-to-batch consistency. The internal spatial shape and arrangement of auxiliary components are also more regular. Due to this standardization and reproducibility, precast cable manholes are increasingly used in new power distribution projects and urban underground pipeline renovations.

[0003] During long-term operation, prefabricated cable wells require regular inspection and evaluation to assess the safety of the well structure and internal environment. The inspection focus in actual projects mainly includes: whether there are structural damages such as cracks, hollow areas, and leaks in the well walls, bottom slab, and joints; whether there is long-term water accumulation or silt buildup at the bottom of the well and near the cable supports, affecting cable insulation performance and maintenance safety; whether the foundation (the foundation of a cable well mainly includes the bearing layer below the bottom of the well body used to support the well's own weight, surface loads, and surrounding soil pressure) has experienced uneven settlement, causing the well to tilt or crack; and whether the well cover and its locking device are reliable, and whether there is a risk of illegal opening or displacement. In existing technologies, one approach relies on manual opening of the cover for inspection, requiring maintenance personnel to enter the well when necessary to assess the structural integrity and water accumulation through visual inspection, tapping, and simple measurements. This method is labor-intensive, inefficient, and carries high safety risks, and is heavily influenced by the experience of the personnel. Another approach involves installing various sensors inside the well, such as those for water level, smoke, harmful gases, and strain, and connecting them to a monitoring system via wired or wireless means to remotely monitor the status of the cable well. However, this type of solution often requires the installation of long-term power and communication lines inside the well, resulting in a large number of devices, high maintenance costs, poor adaptability to the modification of existing cable wells, and usually only directly measuring a certain local physical quantity, making it difficult to conduct an overall assessment of the structural integrity and internal environment without adding a large number of sensor nodes.

[0004] As can be seen from the above, although existing technologies can achieve periodic inspection and status monitoring of prefabricated cable wells to a certain extent, they either rely on personnel entering the well for direct inspection or on the deployment of various long-term sensing devices inside the well. There is still a lack of a method to comprehensively detect and evaluate the degree of water accumulation and siltation in the well and the integrity of the well structure without entering the well, without changing the original structure and cable layout, and with the avoidance of deploying sensors inside the well for a long time. Summary of the Invention

[0005] This application provides a non-invasive inspection method for prefabricated cable wells, aiming to solve the technical problems of existing prefabricated cable well inspection methods that rely on manual entry into the well or long-term placement of sensors inside the well, resulting in high costs, high risks, and the inability to comprehensively assess the state of water accumulation and structural integrity.

[0006] This invention is implemented as follows: a non-invasive inspection method for prefabricated cable wells, comprising: Retrieve the reference response characteristics of the well type to which the prefabricated cable well to be tested belongs; Acoustic excitation is applied to the well chamber, and acoustic and vibration responses are collected simultaneously. Acoustic and vibration features are extracted, and the acoustic and vibration features are compared with the corresponding reference acoustic and vibration features in the reference response features to determine whether there are any abnormalities in the water accumulation state and the integrity of the well structure. When an anomaly is present, the spatial region where the anomaly is located is determined based on the acoustic and vibration characteristics. Based on the spatial region, directional excitation is applied, directional response is collected, and directional features are extracted; Based on the aforementioned acoustic, vibration, and directional characteristics, a graded assessment of the water accumulation status within the well and the structural integrity of the well body is conducted.

[0007] The present invention also provides a non-invasive inspection device for prefabricated cable wells, comprising: The parameter retrieval module is used to retrieve the reference response characteristics of the well type to which the prefabricated cable well to be tested belongs; The preliminary detection module is used to apply acoustic excitation to the well chamber, simultaneously collect acoustic and vibration responses, extract acoustic and vibration features, and compare the acoustic and vibration features with the corresponding reference acoustic and vibration features in the reference response features to determine whether there are any abnormalities in the water accumulation state and the integrity of the well structure. A spatial positioning module is used to determine the spatial region where the anomaly is located based on the acoustic and vibration characteristics when an anomaly is present. The orientation detection module is used to apply orientation excitation to the spatial region, collect orientation response and extract orientation features; The comprehensive evaluation module is used to comprehensively evaluate the water accumulation status and structural integrity of the well by integrating the acoustic characteristics, vibration characteristics, and directional characteristics.

[0008] The present invention also provides a non-invasive inspection device for prefabricated cable wells, comprising: a memory and at least one processor, wherein the memory stores instructions, and the memory and the at least one processor are interconnected by a circuit; the at least one processor invokes the instructions in the memory to cause the non-invasive inspection device for prefabricated cable wells to perform the steps of the above-described non-invasive inspection method for prefabricated cable wells.

[0009] The present invention also provides a computer-readable storage medium storing instructions that, when executed on a computer, cause the computer to perform the steps of the above-described non-invasive detection method for prefabricated cable wells.

[0010] The technical solution provided in this application, based on the standardized characteristics of prefabricated cable wells, uses a series of non-contact acoustic and vibration testing steps to comprehensively assess the water accumulation state and structural integrity of the well. Specifically, the method first retrieves the reference response characteristics of the well type to be tested. These reference response characteristics reflect the reference response curves of the same well type in terms of acoustic resonance and structural vibration under the condition of an empty well and intact structure. Since prefabricated cable wells are highly uniform in terms of geometric dimensions, well depth, and cable support arrangement, the differences between different well types are mainly reflected in these parameters. By retrieving the corresponding reference response characteristics according to the well type, the frequency shifts and amplitude changes observed in subsequent testing can be directly attributed to the changes in the state of the prefabricated cable well itself, rather than design size or structural differences. Based on this premise, acoustic excitation is applied to the well chamber, and acoustic and vibration responses are collected simultaneously. Acoustic and vibration features are extracted and compared with the reference acoustic and vibration features in the reference response characteristics, respectively. Acoustic characteristics reflect the resonance state of the air cavities within the well. Rising water levels or sediment buildup alter the effective cavity height and energy absorption boundaries, resulting in regular shifts in resonant frequency and frequency band distribution. Vibrational characteristics reflect the structural stiffness and mass distribution of the well. Cracks in the well wall, hollowing of the base plate, or uneven foundation settlement reduce local stiffness or alter mass distribution, causing a decrease in the natural frequency and an increase in damping of the corresponding structural modes. By comparing the acoustic and vibrational characteristics with the reference response characteristics, it is possible to determine the state of water accumulation and structural integrity within the well without entering the well or deploying internal sensors, thus achieving a holistic understanding of core status information.

[0011] After detecting an anomalies, the method goes beyond simple alarm triggering. It continues to utilize the correspondence between different modes of acoustic and vibration characteristics and the spatial location of the well chamber to determine the spatial region where the anomaly is located. For example, it infers whether the anomaly is closer to the bottom of the well, a certain support layer height, or the upper space by analyzing the frequency shifts of different order cavity modes; and it infers which side of the well wall the anomaly is biased towards by analyzing the directional changes of different vibration modes. Based on this spatial region information, the method applies targeted directional excitation to the well chamber, making the acoustic or vibration energy more concentrated and coupled to the suspected anomaly area, collecting directional responses and extracting directional features. Because the directional excitation is designed around the anomaly area in terms of frequency range and excitation location, the sensitivity of the directional features to this area is significantly improved, allowing for more precise differentiation between a slight rise in water level and a large amount of water accumulation, a small amount of siltation near the support and significant blockage, and a slight crack in the well wall and a severe decrease in stiffness. Based on this, the method integrates the aforementioned acoustic, vibration, and directional features to conduct a graded assessment of the water accumulation and siltation status and the integrity of the well structure from both overall state and magnified local information perspectives, providing water level level, siltation level, and structural defect level. Through this complete process, starting from the well type benchmark response, combining overall detection with spatial positioning, and then refining the judgment through directional detection, a comprehensive assessment of the internal environment and structural status of prefabricated cable wells was completed without changing the original structure and cable layout or entering the well. This enabled fault prediction and health management of prefabricated cable wells, solving the problems of high risk, high cost, and difficulty in overall assessment associated with traditional manual entry into the well and multi-sensor solutions. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of an embodiment of the non-invasive detection method for prefabricated cable wells in this invention; Figure 2 This is a schematic diagram of one embodiment of the non-invasive detection device for prefabricated cable wells in this invention; Figure 3 This is a schematic diagram of one embodiment of the non-invasive testing equipment for prefabricated cable wells in this invention.

[0014] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0015] 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 merely illustrative and not intended to limit the invention.

[0016] Figure 1 The implementation flow of the non-invasive inspection method for prefabricated cable wells provided in this embodiment is illustrated. For ease of explanation, only the parts relevant to this embodiment are shown, and are detailed below: Please see Figure 1 The reference response characteristics of the well type to which the prefabricated cable well to be tested belongs are retrieved; Specifically, retrieving the reference response characteristics of the prefabricated cable manhole to be tested refers to calling up a set of acoustic reference characteristics and structural vibration reference characteristics corresponding to that manhole type based on the manhole type identification results before the testing begins. The manhole type refers to the classification of prefabricated cable manholes according to a unified module, structural dimensions, and internal structure. This includes not only structural parameters such as manhole depth, planar dimensions, manhole wall material, number and location of cable support layers, and cable duct direction, but also a typical cable arrangement state matching that manhole type. In actual engineering, prefabricated cable manholes are usually in a cable-laying state after being put into use. The cables and supports will have a considerable impact on the cavity's acoustic field and structural vibration. Therefore, the reference response characteristics need to be obtained under this typical laying state to ensure that the inherent response differences caused by the cable arrangement in subsequent testing are not misjudged as water level, siltation, or structural abnormalities.

[0017] Specifically, after the cable is laid out according to the design drawings in a factory test section or a representative manhole, multiple response tests are conducted on the manhole using broadband acoustic excitation and mechanical impact excitation, respectively, to collect acoustic and vibration response data. Frequency domain analysis is performed on each collected data to identify several resonant frequencies of the cavity, frequency band energy distribution, and several natural frequencies and damping parameters of the structure. Statistical analysis is performed on the test results of the same manhole type to obtain stable characteristic values. These characteristics are then stored in a data table or database according to the correspondence between manhole type identification, cable layout category, modal sequence number, and measurement point information to form benchmark response characteristics. In actual testing, the testing terminal can determine the manhole type identification through manhole cover nameplates, maintenance records, or manhole number information in the GIS system. Based on this identification, the corresponding benchmark acoustic and vibration characteristics are retrieved from the data table as reference data for subsequent comparisons.

[0018] This step establishes stable response references for different well types under typical cable laying conditions. This allows deviations in acoustic and vibration characteristics observed during subsequent inspections to be attributed to changes in well conditions such as rising water levels, silt accumulation, or decreased structural stiffness, rather than errors caused by long-term structural factors such as the number and arrangement of cables, thus improving the reliability of the identification. In other embodiments, if the prefabricated cable well has not yet been laid with cables at a certain stage, the same reference response characteristics can be established in the empty well state. During subsequent inspections, a reference dataset consistent with the actual well layout at that time can be selected for comparison, still achieving the same state identification purpose.

[0019] Please continue reading. Figure 1 Acoustic excitation is applied to the well chamber, and acoustic and vibration responses are collected simultaneously. Acoustic and vibration features are extracted, and the acoustic and vibration features are compared with the corresponding reference acoustic and vibration features in the reference response features to determine whether there are any abnormalities in the water accumulation state and the integrity of the well structure. In this scheme, acoustic excitation refers to inputting an excitation signal within a certain frequency range into the air cavity and well structure inside the precast cable well, causing the air and concrete structure inside the well to produce a measurable response under the excitation. Acoustic response refers to the sound pressure change signal reflecting the sound field state of the air inside the well over time. Vibration response refers to the acceleration or velocity change signal reflecting the vibration state of the well body and its connection with the ground over time. Acoustic characteristics are several parameters extracted from the acoustic response, such as resonant frequencies, peak amplitude, and frequency band energy. Vibration characteristics are several parameters extracted from the vibration response, such as structural natural frequencies, peak width, and peak amplitude. Specifically, a portable excitation device can be placed on the surface of the well cover on-site, preferably with mechanical impact at the center of the well cover, to excite the structural vibration of the well cover, well ring, and well wall. At the same time, the broadband energy generated by the impact is coupled into the air cavity inside the well through the gaps or vents in the well cover. Simultaneously with the excitation, several acoustic pressure sensors are arranged on the surface of the manhole cover to collect the acoustic response, and several acceleration or velocity sensors are arranged on the surface of the manhole cover and the surrounding ground to collect the vibration response. All sensors are connected to the same multi-channel data acquisition device, and the acoustic and vibration responses are recorded synchronously through a unified trigger signal or a unified time reference.

[0020] The acquired acoustic and vibration responses are raw time-domain signals. These signals undergo preprocessing, including removing the DC component, bandpass filtering according to a set frequency band, and extracting effective segments according to the excitation time window. Then, frequency domain analysis is performed on the processed signals, for example, using Fast Fourier Transform to obtain amplitude-frequency curves. Several prominent resonance peaks are identified in the acoustic response amplitude-frequency curve, and their corresponding resonance frequencies, peak amplitudes, and energy distribution in the frequency bands near the peaks are recorded. These parameters are used as acoustic features. Similarly, several structural natural frequencies are identified in the vibration response amplitude-frequency curve, and the peak frequency, peak width, and peak amplitude are extracted for each resonance peak. These parameters are used as vibration features. Mechanical impact excitation is a short pulse in time and has broadband characteristics in the frequency domain. It can simultaneously excite the well air cavity mode and the well structure mode in a single excitation. Therefore, acoustic and vibration features can be obtained in the same test, which helps reduce the number of on-site operations and ensures the comparability of the two types of features.

[0021] In engineering applications, such as inspecting prefabricated cable manholes under urban roads, maintenance personnel can apply several standardized impacts to the center of the manhole cover sequentially, under conditions of traffic closure or safety barriers. After each impact, a data acquisition device records a multi-channel response signal for several seconds to tens of seconds, and then uses pre-configured software to complete frequency domain analysis and feature extraction. The excitation method, sensor type, and acquisition equipment used in this process are all commonly used in the field, requiring no special modifications. Furthermore, the rigid connection between the manhole cover, manhole ring, and manhole wall ensures that the excitation energy can be effectively transmitted to the manhole body and the air cavity inside the manhole, resulting in a stable correspondence between the acoustic and vibration characteristics and the actual state inside the manhole. In other embodiments, acoustic excitation can also be achieved by placing a small loudspeaker above the vent of the manhole cover to output a swept frequency sound pressure signal, and vibration excitation can be achieved by applying sinusoidal swept frequency or broadband vibration by a dedicated vibrator; acoustic response can be collected by a microphone near the vent, and vibration response can be collected by a velocity sensor. As long as the signals are recorded synchronously under the same time reference and the collected signals are analyzed in the same frequency domain as described above, equivalent acoustic and vibration characteristics can be obtained, thereby enabling the detection of the internal environment and structural condition of the prefabricated cable well.

[0022] In one embodiment of the present invention, the acoustic feature includes a cavity resonant frequency; The process of determining the state of water accumulation in a well includes: When the cavity resonance frequency increases relative to the corresponding order of the empty well state frequency in the reference response characteristics, it is determined that there is water accumulation or siltation in the well.

[0023] It should be noted that the cavity resonance frequency refers to the frequency values ​​corresponding to several resonance peaks identified in the amplitude-frequency curve of the acoustic response after applying acoustic excitation to the well chamber and performing frequency domain analysis. These resonance peaks are generated by the acoustic cavity formed by the air cavity inside the prefabricated cable well, the well wall, cable supports, and other components. In this scheme, the empty well state frequency refers to the cavity resonance frequency of the prefabricated cable well under conditions of no water accumulation and no siltation. The empty well state can include typical cable arrangements, but does not include water and silt that affect the effective air height. During implementation, after completing acoustic feature extraction, the detection terminal obtains several orders of cavity resonance frequencies, which are numbered according to their order and recorded as the measured cavity resonance frequencies. Simultaneously, the empty well state frequency of the same order for the corresponding well type under the empty well state is retrieved from the reference response features. Based on the frequency difference of each order, the detection terminal determines whether the measured cavity resonance frequency has increased relative to the empty well state frequency. When at least one or more order cavity resonance frequencies exceed a preset threshold in the positive offset, the judgment result of water accumulation or siltation inside the well is output.

[0024] The physical reason for this judgment is that the effective height of the air column inside the prefabricated cable well plays a role in determining the cavity's resonant frequency. When other conditions remain essentially unchanged, a decrease in the effective air height leads to an overall increase in the cavity's resonant frequency. Water or silt accumulation at the bottom of the well occupies the bottom space, reducing the effective height of the air cavity. For cavity modes whose vibration direction is primarily well depth, assuming the sound velocity and well geometry remain constant, a stable, upward-biased shift will occur between the resonant frequency in an empty well and the resonant frequency with water or silt accumulation. By calibrating under different water levels and silt thicknesses during the testing phase, a reasonable threshold range can be set for the frequency differences of each order. This ensures that small frequency fluctuations caused by factors such as temperature changes and manufacturing errors will not trigger misjudgments, while larger frequency increases caused by water and silt accumulation can be reliably identified.

[0025] In other embodiments, the judgment process can also use a comprehensive criterion of multi-order cavity resonant frequencies. For example, the equivalent air height can be fitted based on the frequency changes of multiple orders, and the equivalent air height can be compared with the designed well depth or the calibrated empty well height. When the equivalent air height is significantly less than the empty well height, it can also be judged that there is water accumulation or siltation in the well. Alternatively, the change of the ratio of multiple order frequencies can be used as the judgment index. As long as the judgment basis is still based on the physical relationship that the decrease in effective air height leads to the increase in cavity resonant frequency, the same identification purpose as the frequency difference comparison mentioned above can be achieved.

[0026] In one embodiment of the present invention, the vibration characteristic includes the structure's natural frequency; The process of determining the structural integrity of a well includes: When the inherent frequency of the structure decreases relative to the intact state frequency of the corresponding mode in the reference response characteristics, it is determined that there is a structural defect in the well body.

[0027] Specifically, the structural natural frequencies refer to the frequency values ​​corresponding to the resonance peaks generated by the vibration of the well structure, identified in the amplitude-frequency curve of the vibration response after applying excitation to the well chamber and performing frequency domain analysis. These vibration modes are mainly determined by the well wall, well ring, bottom plate, and the constraint relationship with the foundation. The intact state frequencies refer to the structural natural frequencies obtained from the reference response characteristics through preliminary calibration tests, assuming the prefabricated cable well structure has no cracks, no obvious voids, and no uneven settlement of the foundation. In practice, after completing the frequency domain analysis of the vibration response, the detection terminal identifies several structural modes from the amplitude-frequency curve of the vibration response based on the peak amplitude, frequency range, and coupling relationship with acoustic characteristics, and records the corresponding frequencies as the structural natural frequencies. Then, the intact state frequencies of each mode are retrieved from the reference response characteristics of the same well type and matched one-to-one with the measured structural natural frequencies. The detection terminal calculates the frequency difference of each mode. When the structural natural frequency of one or more key modes decreases significantly relative to the frequency of the intact state and the decrease exceeds a preset threshold, the terminal outputs a judgment result indicating that there is a structural defect in the well body.

[0028] Assuming the material parameters and geometric dimensions of structural components remain unchanged, a decrease in overall stiffness or an increase in added mass will cause the natural frequencies of the corresponding modes to shift towards lower frequencies. For precast cable wells, cracks in the well wall, loose joints, and voids between the base plate and the foundation will all reduce local stiffness, thus lowering the natural frequencies of the overall or local structural modes. Uneven foundation settlement leading to well tilting or changes in the force boundary on one side will also lower the frequencies of lower-order bending modes. Temperature changes or aging of concrete materials have a relatively slow and small impact on natural frequencies. By statistically analyzing the normal fluctuation range of the same well type during the calibration phase, reasonable judgment thresholds can be set for each frequency order, preventing small-amplitude environmental influences from being misjudged as structural defects, while frequency reductions caused by significant stiffness weakening or changes in the force boundary can be reliably distinguished.

[0029] In other implementations, the judgment process may not directly use the frequency difference, but instead use the ratio of multiple structural natural frequencies as a criterion. For example, the frequency ratio between several low-order modes can be calculated, and the measured frequency ratio can be compared with the frequency ratio of the intact state. When the measured frequency ratio is generally biased towards the softened side, the conclusion that the structural stiffness has decreased can also be drawn. This criterion based on frequency ratio can, to some extent, reduce the influence of absolute frequency on temperature and overall mass changes. As long as the basic relationship of structural natural frequency reduction reflecting stiffness reduction is still utilized, the purpose of identifying well body structural defects can be achieved.

[0030] Please continue reading. Figure 1 When an anomaly is present, the spatial region where the anomaly is located is determined based on the acoustic and vibration characteristics. In one embodiment of the present invention, the process of determining whether an anomaly exists includes: An anomaly is determined when the offset of the acoustic or vibrational features relative to the reference response features exceeds a preset threshold. The process of determining the spatial region where the anomaly is located includes: Identify multiple modal frequencies in the acoustic features, wherein the multiple modal frequencies correspond to acoustic cavities at different heights within the well chamber; The offset of each modal frequency is compared with the reference response characteristics. Based on the cavity height corresponding to the modal frequency with the largest offset, the longitudinal height region where the anomaly is located is determined.

[0031] Specifically, identifying multiple modal frequencies in acoustic features refers to selecting several resonance peaks dominated by the air cavities in the well chamber from the amplitude-frequency curve of the acoustic response, given the existing acoustic features, and using the frequencies of these resonance peaks as multiple modal frequencies. To ensure that these modal frequencies correspond to acoustic cavities at different heights within the well chamber, during the calibration phase of the reference response features, using this well type as the object, and under conditions of an empty well and intact structure, graded tests are conducted at different water levels. For example, the water level is sequentially controlled at several height intervals, such as near the bottom plate, near the middle support layer, and near the wellhead. The same acoustic excitation is applied to the well chamber at each height interval, and the acoustic response is collected and analyzed. By comparing the amplitude-frequency curves at each height interval, the resonance peak most sensitive to frequency changes at a certain height interval is recorded. A correspondence is established between the order of these resonance peaks and the corresponding height interval, and this correspondence is stored along with the reference response features. During testing, frequency domain analysis is performed on the acoustic response to identify several modal frequencies of the same order as those in the baseline response characteristics. The cavity height ranges recorded during the calibration phase are then used to identify the acoustic cavities at different heights within the well chamber for each modal frequency. In other embodiments, a simplified acoustic analysis of the well chamber can be performed to calculate the principal vibration height ranges of different order cavity modes. This calculation, combined with a small number of experiments for correction, can then be used to establish the same correspondence.

[0032] Comparing the frequency offsets of each modal with the baseline response characteristics involves calculating the difference between the measured modal frequency and the modal frequency of the same order under empty well conditions for each modality, and recording the frequency offset and its positive or negative direction. Since water accumulation or siltation only occupies a certain height range within the well chamber, it has the greatest impact on the cavity mode most strongly coupled to that height range. Its corresponding modal frequency offset is larger than other modes, and the offset direction is upward. The detection terminal sorts the frequency offsets according to their magnitude, selects the modal frequency with the largest offset, reads the cavity height range corresponding to that modal frequency during the calibration phase, and determines that this height range is the longitudinal height region where the anomaly is located. For example, when the frequency offset corresponding to the height range near the bottom plate is the largest, the anomaly is determined to be mainly located in the bottom region; when the frequency offset corresponding to the height range near a certain middle support layer is the largest, the anomaly is determined to be mainly concentrated near that support layer. In other implementations, multiple modal frequency offsets can be weighted and summarized according to their energy weights in different height ranges to obtain a comprehensive index for each height range. Then, the height range with the largest index can be selected as the longitudinal height region where the anomaly is located, further improving the localization capability when multiple minor anomalies exist simultaneously.

[0033] In one embodiment of the present invention, the process of determining the spatial region where the anomaly is located further includes: The response characteristics of different vibration modes in the vibration features are analyzed. The location of the anomaly in the circumferential direction is determined based on the change characteristics of a specific vibration mode. Combined with the longitudinal height region, the three-dimensional spatial location of the anomaly is determined.

[0034] The above embodiment analyzes the response characteristics of different vibration modes in the vibration features and determines the location of the anomaly in the circumferential direction based on the change characteristics of a specific vibration mode. This can be understood as follows: by using multiple vibration measuring points arranged at different locations around the manhole cover, the response amplitude and phase of the vibration mode corresponding to the natural frequency of the same structure at different locations are compared, thereby inferring which circumferential direction the weakening of the well body stiffness or the change in constraint is concentrated in. In this scheme, the vibration mode refers to the specific vibration pattern formed by the manhole cover and the connected well ring and well wall near a certain natural frequency of the structure; the response characteristics refer to parameters such as the amplitude, phase difference, and energy distribution of the vibration mode at each measuring point. In implementation, four or more accelerometers can be arranged at equal intervals along the circumferential direction around the manhole cover to record the vibration amplitude and phase of each measuring point at the aforementioned natural frequency of the structure, forming a set of response characteristic data corresponding one-to-one with the location of the measuring point. In the benchmark response characteristic calibration stage, the response distribution characteristics of each structural vibration mode at these measuring points under the intact state have been recorded, which usually present an approximately symmetrical or symmetrical arrangement according to the design structure. When cracks, loose joints, or foundation settlement occur near a sidewall or circumferential direction of the well body, the local stiffness associated with that direction decreases. This causes significant changes in the displacement and acceleration responses of that area under specific modes compared to the intact state. For example, the amplitude may increase or decrease significantly, or the symmetry with the opposite side may be disrupted. The detection terminal compares the normalized measured response characteristics with the reference response characteristics to identify which direction has the greatest deviation, and determines the circumferential direction corresponding to that direction as the location of the anomaly. For example, in an urban road scenario, if measuring points are arranged along the east, south, west, and north directions, under a certain low-order bending mode, the amplitude at the eastern measuring point is significantly abnormal compared to the intact state, while the changes in other directions are smaller. In this case, the area near the east side of the well body is identified as the abnormal direction. In other implementations, the direction of the dominant wave propagation can also be determined by analyzing the arrival time difference and energy distribution of the short-time impact response at each measuring point. The location of stiffness weakening can then be inferred from the wave propagation direction, still achieving the identification of the abnormal circumferential direction location.

[0035] Determining the anomaly's three-dimensional spatial location by combining its circumferential position with its longitudinal height region involves combining the longitudinal height region (e.g., near the bottom plate, the middle support layer, or near the wellhead) with its circumferential position to define a three-dimensional area with both height and azimuth ranges within the cylindrical space of the well chamber. This area represents the most likely location of the anomaly. The longitudinal height region, determined by the cavity resonant frequency offset, corresponds to a height range along the well chamber's axial direction. The circumferential position corresponds to an angular range on the well chamber's cross-section. After locating the anomaly in these two directions, the detection terminal can approximate the well chamber as a cylinder or polygonal prism, establishing a circumferential angular coordinate system centered on the well axis. The anomaly's circumferential position is represented as an angular range, and the longitudinal height region as a height range from one elevation to another. The intersection of these two coordinates forms an arc-shaped three-dimensional region. For example, if the longitudinal height region is determined to be near the height of the first layer of cable supports in the middle, and the circumferential position is located in the southeast quadrant of the well body, then this three-dimensional spatial position can be described as "the well wall and its adjacent area within a certain degree range around the southeast quadrant within the height range of the first layer of supports in the middle". This three-dimensional position can be used to guide the subsequent directional excitation arrangement (prioritizing enhanced detection in the corresponding azimuth and height-sensitive frequency bands), and can also be used to arrange key inspection areas during on-site maintenance. In other embodiments, if the well body geometry is a rectangular or polygonal cross-section, the circumferential position can be defined according to the azimuth segments corresponding to each side or corner. The longitudinal height region, combined with this, can still determine an abnormal region with three-dimensional dimensions of length, width, and height, thereby achieving a unified three-dimensional spatial positioning logic in prefabricated cable wells with different geometric forms.

[0036] Please continue reading. Figure 1 Based on the spatial region, directional excitation is applied, directional response is collected, and directional features are extracted; In one embodiment of the present invention, the orientation feature includes local response features for anomaly spatial regions; The process of extracting directional features includes: For the acoustic cavity or structural part corresponding to the abnormal spatial region, the frequency, amplitude and damping parameters of its response signal are extracted as refined feature parameters of the corresponding region.

[0037] It should be noted that applying directional excitation based on a spatial region means, after determining the location of the abnormal spatial region in both the longitudinal height and circumferential direction, selecting the manhole cover location and excitation frequency band that has the shortest structural transmission path or the strongest acoustic coupling with that spatial region, and then performing a second or subsequent excitation operation on the manhole chamber. The spatial region refers to the three-dimensional region jointly defined by the aforementioned longitudinal height region and circumferential location, such as the area near the height of the first layer of cable supports in the middle and close to the east side of the manhole body. In practice, an area near this circumferential location can be selected on the manhole cover plane as the excitation point. For example, an impact hammer or vibration excitation device can be arranged at a position slightly towards the center on the east side of the manhole cover, applying impact along the normal direction of the manhole cover or slightly off-center to allow energy to preferentially propagate along the contact point between the manhole cover and the manhole ring to the corresponding side of the manhole wall and structural parts near that height. If the spatial region is mainly related to acoustic cavities (e.g., significant water accumulation or siltation within a certain height range), a narrow-band sweep excitation can be output within the cavity mode-sensitive frequency band corresponding to that region, covering the cavity mode frequencies of the aforementioned corresponding height region. If the spatial region is mainly related to structural parts (e.g., localized weakening of well wall stiffness or localized hollowing of the bottom plate), a more low- or mid-frequency impact excitation can be selected to fully excite the structural modes more strongly coupled to that structural part. Simultaneously with directional excitation, several vibration measurement points are arranged on the surface of the well cover and the surrounding ground near the projection direction of the spatial region, and sound pressure measurement points are arranged near the vent holes of the well cover or near the openings in that direction, making the acquired response signals more sensitive to changes in that spatial region. By selecting the excitation location, direction, and frequency band based on the spatial region, the propagation path of the excitation energy in the structure and cavity is more concentrated in the abnormal spatial region, increasing the contribution of that region to the overall response and facilitating the subsequent extraction of directional features characterizing the state changes of that region from the response signal. In other implementations, directional excitation can also be achieved by sequentially applying small-range moving impacts or frequency sweeps at multiple locations on the manhole cover, collecting responses at each location, and comparing the response changes that are more sensitive to abnormal spatial areas under different directional excitations to achieve the same purpose of emphasizing specific spatial areas.

[0038] In the above embodiments, local response features refer to the portion of the frequency domain or time domain response that reflects the state changes of the abnormal spatial region at a specific measuring point or combination of measuring points under directional excitation conditions. For example, the vibration amplitude change of a measuring point near the edge of a manhole cover close to the abnormal circumference at a relevant modal frequency, or the frequency and peak shape changes of the cavity resonance peak associated with that height range. In practice, for one or more modal frequencies related to the abnormal spatial region, frequency bands near these modes can be selected from the amplitude-frequency curve after directional excitation. The center frequency, peak amplitude, and peak width of the mode can be determined using curve fitting or half-power bandwidth methods. There is a one-to-one correspondence between the peak width and the damping parameter, thereby obtaining the damping parameter of the mode. For abnormal regions dominated by acoustic cavities, the response of sound pressure measuring points can be preferentially selected for feature extraction; for abnormal regions dominated by structural parts, the response of vibration measuring points in the corresponding direction can be preferentially selected for feature extraction. By comparing these frequency, amplitude, and damping parameters with the characteristics of the same location under overall excitation and with the corresponding parameters in the baseline response characteristics, changes in stiffness, energy dissipation, and local mass distribution in the spatial region can be determined. This refines the identification of the degree and type of anomaly, such as distinguishing between increased cavity dissipation due to simple water accumulation and decreased structural stiffness due to well wall cracking. In other embodiments, the damping parameters can also be obtained by time-domain envelope fitting of the free decay segment after directional excitation. As long as the final quantized parameters that reflect the local energy decay characteristics of the anomalous spatial region are obtained, they can be used as part of the directional features, achieving the same local state characterization effect as the frequency domain half-power bandwidth method.

[0039] Please continue reading. Figure 1 Based on the acoustic, vibration, and directional characteristics, the water accumulation status and structural integrity of the well are assessed in a graded manner.

[0040] In one embodiment of the present invention, the grading assessment includes: The severity level of water accumulation in the well is determined based on the variation of the acoustic and directional characteristics relative to the baseline response characteristics. The severity level of well body structural defects is determined based on the variation of the vibration and orientation characteristics relative to the baseline response characteristics.

[0041] In the above embodiments, determining the severity level of water accumulation in the well based on the changes in acoustic and directional features relative to the baseline response features means that, after determining that water or siltation exists in the well and acquiring acoustic, directional, and baseline response features, these feature parameters are quantified into several indicators related to water level and siltation thickness, and compared with pre-calibrated threshold intervals to provide a classification conclusion. The acoustic features used to reflect the degree of water accumulation may include the offset of the resonant frequencies of multiple cavity modes relative to the frequency of the empty well state, the attenuation degree of the peak amplitude of each mode, and the redistribution of energy within the relevant frequency band; the directional features may select local response features such as frequency offset, peak amplitude, and damping parameters corresponding to the cavity modes in the abnormal spatial region. During implementation, in the experimental phase, for representative well types, acoustic responses are collected under different water levels and siltation thicknesses, the above parameters are extracted, and the frequency offset, amplitude change, and damping change range corresponding to each condition are recorded to form threshold intervals corresponding to the water level and siltation thickness levels. During on-site testing, the testing terminal calculates the magnitude of change of relevant parameters in the overall acoustic and directional characteristics relative to the baseline response characteristics. This includes, for example, the absolute value and relative percentage increase in a key modal frequency, the percentage decrease in peak amplitude, and the degree of increase in damping parameters. These magnitudes are then compared to calibrated thresholds: if all changes are within the slight range, the severity of water accumulation in the well is determined to be slight; if the key modal frequency shift and damping increase enter the middle range, it is determined to be moderate; and if multiple parameters exceed the highest threshold, it is determined to be severe. By simultaneously utilizing the overall spectral changes in the acoustic characteristics and the local refinement parameters in the directional characteristics, the average water accumulation status across the entire well and the local severity in specific spatial areas can be considered within the same set of rules. This ensures that the resulting severity level reflects both the overall trend and gives sufficient weight to local anomalies. In other implementations, acoustic and directional features can also be normalized to dimensionless indices, and a comprehensive water accumulation index can be formed by weighted summation. The severity level can then be output based on the correspondence between the index and a preset interval. As long as the weights and interval settings are still based on the aforementioned calibration results and physical meaning, an equivalent graded assessment can be achieved.

[0042] Determining the severity level of well body structural defects based on the variation amplitude of vibration and directional characteristics relative to the baseline response characteristics involves, after extracting vibration characteristics from the vibration response and directional characteristics from the detection of abnormal spatial regions, quantitatively comparing the parameters reflecting stiffness reduction and energy dissipation changes in these characteristics with their corresponding parameters in the intact state, and classifying the severity of structural defects according to the variation amplitude. Vibration characteristics can include the reduction amplitude of several low- and mid-order structural natural frequencies, the increase amplitude of resonance peaks, and the redistribution of overall vibration energy in different modes; directional characteristics can include refined parameters such as local frequency reduction, abnormal amplification or attenuation of local peak amplitudes, and increase in local damping parameters corresponding to the structural modes in the abnormal spatial regions. During implementation, in the structural calibration stage of the precast cable well, different levels of defect conditions can be artificially set on the test well. For example, cracks of different widths and lengths in the well wall can be created, different ranges of hollow bottom plates can be simulated, or the foundation support conditions can be changed. Vibration tests can be conducted on each level of defect condition, the above parameters can be extracted, and the frequency reduction range, damping increase magnitude, and local response asymmetry corresponding to each defect level can be recorded. This forms a range of characteristic parameters for three or more levels of defects: mild, moderate, and severe. During on-site testing, the testing terminal compares the parameters in the measured vibration and directional characteristics with the corresponding parameters in the baseline response characteristics for the intact state. It calculates the absolute and relative percentage decrease in key modal frequencies, the percentage increase in peak width, the increment of local damping parameters, and the ratio of the response difference between the abnormal spatial region and the opposite region. These changes are then matched to the calibration range: if the parameter changes are within a slight deviation range, the structural defect severity is determined to be mild, which can be addressed through planned maintenance; if the changes enter the moderate range, the well structure's safety margin is considered significantly reduced, requiring more urgent repair work; if multiple key modal frequencies decrease significantly and local damping increases significantly, it can be determined to be a severe defect, requiring priority reinforcement or structural replacement. By combining global vibration characteristics and directional characteristics of the abnormal spatial region, it avoids amplifying random errors based solely on local characteristics and also avoids insufficient sensitivity to severe local damage when analyzing only overall characteristics. In engineering applications, this provides maintenance personnel with a structural defect level assessment that matches the actual risk level. In other implementations, vibration characteristics and orientation characteristics can be combined into a comprehensive structural risk index according to a pre-set weight, and the severity level of defects can be given according to the interval correspondence of the index. As long as the weight allocation and interval division meet the aforementioned calibration results and stress analysis conclusions, the same risk classification effect as direct threshold segmentation can be achieved.

[0043] The above describes the non-invasive inspection method for prefabricated cable wells in embodiments of the present invention. The following describes the non-invasive inspection device for prefabricated cable wells in embodiments of the present invention. Please refer to [link / reference]. Figure 2 One embodiment of the non-invasive detection device for prefabricated cable wells according to the present invention includes: The parameter retrieval module 101 is used to retrieve the reference response characteristics of the well type to which the prefabricated cable well to be tested belongs; The preliminary detection module 102 is used to apply acoustic excitation to the well chamber, simultaneously collect acoustic and vibration responses, extract acoustic and vibration features, and compare the acoustic and vibration features with the corresponding reference acoustic and vibration features in the reference response features to determine whether there are any abnormalities in the water accumulation state and the integrity of the well structure. The spatial positioning module 103 is used to determine the spatial region where the anomaly is located based on the acoustic and vibration characteristics when an anomaly is present. Orientation detection module 104 is used to apply orientation excitation according to the spatial region, collect orientation response and extract orientation features; The comprehensive evaluation module 105 is used to comprehensively evaluate the state of water accumulation in the well and the structural integrity of the well by integrating the acoustic characteristics, vibration characteristics and directional characteristics.

[0044] above Figure 2 The non-invasive inspection device for prefabricated cable wells in this embodiment of the invention is described in detail from the perspective of modular functional entities. The non-invasive inspection device for prefabricated cable wells in this embodiment of the invention is described in detail below from the perspective of hardware processing.

[0045] Figure 3 This is a schematic diagram of a non-invasive inspection device for prefabricated cable wells provided in an embodiment of the present invention. The non-invasive inspection device 200 for prefabricated cable wells can vary significantly due to different configurations or performance characteristics. It may include one or more processors 210 (e.g., one or more processors) and a memory 220, and one or more storage media 230 (e.g., one or more mass storage devices) for storing application programs 233 or data 232. The memory 220 and storage media 230 can be temporary or persistent storage. The program stored in the storage media 230 may include one or more modules (not shown in the diagram), each module including a series of instruction operations on the non-invasive inspection device 200 for prefabricated cable wells. Furthermore, the processor 210 may be configured to communicate with the storage media 230 and execute the series of instruction operations in the storage media 230 on the non-invasive inspection device 200 for prefabricated cable wells to implement the steps of the aforementioned non-invasive inspection method for prefabricated cable wells.

[0046] The non-invasive inspection device 200 for prefabricated cable wells may also include one or more power supplies 240, one or more wired or wireless network interfaces 250, one or more input / output interfaces 260, and / or one or more operating systems 231, such as Windows Server, Mac OS X, Unix, Linux, FreeBSD, etc. Those skilled in the art will understand that... Figure 3 The structure of the non-invasive inspection device for prefabricated cable wells shown does not constitute a limitation on the non-invasive inspection device for prefabricated cable wells provided by the present invention. It may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0047] The present invention also provides a computer-readable storage medium, which may be a non-volatile computer-readable storage medium or a volatile computer-readable storage medium, wherein the computer-readable storage medium stores instructions that, when executed on a computer, cause the computer to perform the steps of the non-invasive detection method for the prefabricated cable well.

[0048] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system, device, or unit described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0049] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0050] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method of non-invasive detection of a pre-fabricated cable shaft, characterized in that, The method comprises the following steps: obtaining the reference response characteristics of the well type to which the preformed cable well to be tested belongs; applying acoustic excitation to the well chamber, synchronously collecting acoustic response and vibration response, extracting acoustic characteristics and vibration characteristics, and comparing the acoustic characteristics and vibration characteristics with the corresponding reference acoustic characteristics and reference vibration characteristics in the reference response characteristics respectively to determine whether there is an abnormality in the water accumulation state in the well and the structural integrity of the well body; when there is an abnormality, determining the spatial region where the abnormality is located according to the acoustic characteristics and vibration characteristics; applying directional excitation according to the spatial region, collecting directional response and extracting directional characteristics; comprehensively evaluating the water accumulation state in the well and the structural integrity of the well body according to the acoustic characteristics, vibration characteristics and directional characteristics.

2. The method of non-invasive detection of a pre-fabricated cable shaft according to claim 1, characterized in that, The acoustic characteristics include cavity resonance frequencies; the process of determining the water accumulation state in the well comprises: when the cavity resonance frequencies are higher than the cavity state frequencies of the corresponding orders in the reference response characteristics, it is determined that there is water or accumulation in the well.

3. The method of non-invasive detection of a pre-fabricated cable shaft according to claim 1, characterized in that, The vibration characteristics include structural natural frequencies; the process of determining the structural integrity of the well body comprises: when the structural natural frequencies are lower than the intact state frequencies of the corresponding modes in the reference response characteristics, it is determined that there is a structural defect in the well body.

4. The method of non-invasive detection of a pre-fabricated cable chamber according to claim 1, characterized in that, the process of determining whether there is an abnormality comprises: when the offset of the acoustic characteristics or vibration characteristics with respect to the reference response characteristics exceeds a preset threshold, it is determined that there is an abnormality; the process of determining the spatial region where the abnormality is located comprises: identifying a plurality of modal frequencies in the acoustic characteristics, the plurality of modal frequencies corresponding to acoustic cavities at different heights in the well chamber respectively; comparing the offset of each modal frequency with the reference response characteristics, and determining the longitudinal height region where the abnormality is located according to the cavity height corresponding to the modal frequency with the largest offset.

5. The method of non-invasive detection of a pre-fabricated cable shaft according to claim 4, characterized in that, the process of determining the spatial region where the abnormality is located further comprises: analyzing the response characteristics of different vibration modes in the vibration characteristics, determining the position of the abnormality in the circumferential direction according to the change characteristics of a specific vibration mode, and combining the longitudinal height region to determine the three-dimensional spatial position of the abnormality.

6. The method of non-invasive detection of a pre-fabricated cable shaft according to claim 5, characterized in that, The directional characteristics include local response characteristics of the abnormal spatial region; the process of extracting directional characteristics comprises: extracting the frequency, amplitude and damping parameters of the response signal of the acoustic cavity or structural part corresponding to the abnormal spatial region as the detailed characteristic parameters of the corresponding region.

7. The method of non-invasive detection of a pre-fabricated cable shaft according to claim 6, characterized in that, The hierarchical evaluation comprises: determining the severity level of the water accumulation in the well according to the change amplitude of the acoustic characteristics and directional characteristics with respect to the reference response characteristics; determining the severity level of the structural defect of the well body according to the change amplitude of the vibration characteristics and directional characteristics with respect to the reference response characteristics.

8. A non-intrusive detection device for a pre-fabricated cable shaft, characterized in that The method comprises the following steps: a parameter retrieval module for retrieving the reference response characteristics of the well type to which the preformed cable well to be tested belongs; a preliminary detection module for applying acoustic excitation to the well chamber, synchronously collecting acoustic response and vibration response, extracting acoustic characteristics and vibration characteristics, and comparing the acoustic characteristics and vibration characteristics with the corresponding reference acoustic characteristics and reference vibration characteristics in the reference response characteristics respectively to determine whether there is an abnormality in the water accumulation state in the well and the structural integrity of the well body; The spatial positioning module is configured to determine a spatial region where the anomaly is located according to the acoustic feature and the vibration feature when the anomaly exists. The directional detection module is configured to apply directional excitation according to the spatial region, collect directional response and extract directional feature. The comprehensive evaluation module is configured to comprehensively evaluate the acoustic feature, the vibration feature and the directional feature, and grade the well water accumulation state and the well body structural integrity.

9. A non-intrusive detection apparatus for a pre-fabricated cable shaft, characterized in that The non-intrusive detection device of the prefabricated cable well comprises a memory and at least one processor, and the memory stores instructions. The at least one processor invokes the instructions in the memory to enable the non-intrusive detection device of the prefabricated cable well to perform the steps of the non-intrusive detection method of the prefabricated cable well according to any one of claims 1 to 7.

10. A computer-readable storage medium having stored thereon instructions, the instructions comprising, The instructions are executed by the processor to implement the steps of the non-intrusive detection method of the prefabricated cable well according to any one of claims 1 to 7.

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