Non-destructive testing method and system for road base compaction based on the impact echo method

Abstract

The application provides a kind of road base compaction degree nondestructive testing method and system based on impact echo method, it is related to road nondestructive testing technical field, it is applied to inspection well or pipeline well peripheral base reinforcement area.The method obtains well body outer contour, base design thickness, wave velocity calibration value and detection point radial distance and ring angle;According to inner, middle and outer ring, detection point is arranged to collect impact echo signal;Well side reflection prediction echo window and base bottom surface reflection evaluation window are generated and well side reflection attenuation curve is formed;Main peak, adjacent energy area and phase mutation area are identified and deducted or weighted to obtain base effective echo;Based on reflection to reach stable component, effective band energy attenuation component and main frequency shift component, compaction abnormal value is formed;Excluding boundary interference, continuous anomaly is combined into ring under-compaction suspected area, the accuracy and reliability of well peripheral base compaction degree nondestructive testing are improved.

Description

Technical Field

[0001] This application relates to the field of road non-destructive testing technology, and in particular to a non-destructive testing method and system for road base compaction based on the impact echo method. Background Technology

[0002] During road construction and operation, manholes and utility manholes often penetrate the roadbed and base course structure. Manholes include stormwater manholes, sewage manholes, and inspection manholes, while utility manholes include water supply manholes, power manholes, and communication manholes. Due to the geometric discontinuity at the interface between the manhole wall and the base course, and the space constraints on the compaction process of the backfill material near the manhole frame, the base course reinforcement zone within a certain range around the manhole becomes a weak point in the compaction quality. Under long-term vehicle loads, this zone is prone to defects such as manhole perimeter subsidence, manhole frame bouncing, and pavement damage.

[0003] Currently, the main methods for detecting the compaction degree of the base course around wells include core sampling and impact echo methods. Core sampling is a destructive testing method, requiring drilling into the base course to obtain compaction results through laboratory procedures. This method has drawbacks, including damaging the pavement structure, having a limited number of testing points, and being unable to perform comprehensive area surveys. Impact echo methods, on the other hand, are non-destructive testing methods. By applying instantaneous impact excitation to the testing points and collecting the surface vibration response signal, the arrival time and spectral characteristics of the reflected signals from the base course's bottom surface are used to assess the uniformity of the base course thickness and its compaction state. This method offers advantages such as being non-destructive and highly efficient.

[0004] However, when traditional impact echo methods are used to detect the base layer around inspection wells or pipeline wells, the well body, acting as a strong reflective interface, generates well-side reflections in the echo signal. These well-side reflections may overlap with the reflections from the base layer bottom surface in the time domain, manifesting as energy attenuation, dominant frequency shift, and arrival time disturbances in a manner similar to compaction anomalies. This creates strong boundary interference for extracting compaction anomaly values. If this boundary interference is not eliminated, the reflection artifacts caused by the well body can easily be misjudged as undercompacted areas of the base layer, leading to misdiagnosis. Conversely, if all detection results near the well body are discarded, the actual undercompactment defects in the surrounding reinforcement area may be missed, resulting in false negatives.

[0005] Therefore, how to effectively distinguish between boundary reflection interference caused by the well body and the actual compaction anomaly of the base layer in the impact echo detection of the base layer reinforcement area around the inspection well or pipeline well, and accurately identify the suspected under-compacted area around the well, is an urgent technical problem to be solved. Summary of the Invention

[0006] The purpose of this application is to overcome the shortcomings of existing impact echo methods in detecting the compaction of road manholes or pipeline manholes, which make it difficult to distinguish between manhole-side reflection interference and actual compaction anomalies, and are prone to misjudgment or omission. This application provides a non-destructive testing method and system for road base compaction based on impact echo method, so as to improve the accuracy and reliability of non-destructive testing of compaction of the base around manholes.

[0007] The purpose of this application is to achieve the following: Firstly, this application provides a non-destructive testing method for the compaction degree of road base courses based on the impact echo method, applicable to the base course reinforcement area around road manholes or pipeline manholes, the method comprising: Obtain the outer contour of the well body, the design thickness of the base layer, the wave velocity calibration value, and the radial distance and circumferential angle of the detection point relative to the well body; Detection points were set up around the well body in the form of inner ring, middle ring and outer ring, and the impact echo signals of each detection point were collected; Based on the radial distance, the base layer design thickness, and the wave velocity calibration value, a wellside reflection prediction echo window and a base layer bottom surface reflection evaluation window are generated. Based on the reflection changes of the inner ring, middle ring, and outer ring detection points at the same circumferential angle within the wellside reflection prediction echo window, a wellside reflection attenuation curve is formed. Within the wellside reflection prediction echo window, the main peak of the wellside reflection, the energy region adjacent to the main peak, and the phase change region are identified, and subtraction or weighting is performed based on the wellside reflection attenuation curve to obtain the effective echo of the base layer. The reflection arrival stability component, effective frequency band energy attenuation component, and main frequency offset component of the effective echo of the base layer are extracted in the reflection evaluation window of the base layer bottom surface, and the three are combined into a compaction anomaly value. The compaction anomalies at the inner, middle, and outer ring detection points in the same radial direction are compared. Boundary interference results that match the wellside reflection attenuation curve are excluded, and continuous anomaly detection points are merged into a suspected circumferential undercompactment zone.

[0008] In conjunction with the first aspect, the acquisition of the well body's external contour, base layer design thickness, wave velocity calibration value, and the radial distance and circumferential angle of the detection point relative to the well body includes: determining the external contour of the well body based on the outer edge of the manhole ring, the outer edge of the manhole wall, or the outer edge of the pipeline manhole; determining the base layer design thickness based on the base layer construction design documents or on-site thickness measurement results; acquiring impact echo signals at a base layer location far from the well body where the compaction state has been confirmed, and obtaining the wave velocity calibration value based on the arrival time of the reflection from the bottom surface of the base layer; and determining the radial distance and circumferential angle of the detection point using the geometric center of the well body's external contour or the projection point of the pipeline manhole axis as an angular reference.

[0009] In conjunction with the first aspect, the generation of the wellside reflection prediction echo window and the base course bottom surface reflection evaluation window includes: determining the wellside reflection arrival time interval based on the radial distance of the detection point and the wave velocity calibration value, and expanding the wellside reflection arrival time interval into the wellside reflection prediction echo window; determining the base course bottom surface reflection arrival time interval based on the base course design thickness and the wave velocity calibration value, and expanding the base course bottom surface reflection arrival time interval into the base course bottom surface reflection evaluation window; when the wellside reflection prediction echo window and the base course bottom surface reflection evaluation window overlap, the overlapping part is marked as a boundary interference candidate area.

[0010] In conjunction with the first aspect, the step of forming a wellside reflection attenuation curve based on the reflection changes of the inner, middle, and outer ring detection points at the same circumferential angle within the wellside reflection prediction echo window includes: extracting the reflection peak value, energy area, or phase change amplitude of the inner, middle, and outer ring detection points at the same circumferential angle within the wellside reflection prediction echo window; sorting the reflection peak value, energy area, or phase change amplitude according to the radial distance of the detection points; determining the reflection change relationship that attenuates with increasing radial distance as the wellside reflection attenuation curve corresponding to the circumferential angle; and selecting only one of the three characteristics—reflection peak value, energy area, and phase change amplitude—as the sole indicator of the wellside reflection attenuation curve at the same circumferential angle.

[0011] In conjunction with the first aspect, identifying the wellside reflection main peak, the adjacent energy region of the main peak, and the phase abrupt change region within the wellside reflection prediction echo window includes: determining the position of the peak with a prominent amplitude within the wellside reflection prediction echo window based on the local background amplitude, and taking the peak position as the wellside reflection main peak; searching for sampling intervals with continuously higher energy than the local background energy forward and backward from the wellside reflection main peak as the center, and taking the sampling intervals as the adjacent energy region of the main peak; performing phase continuity analysis on the signal within the wellside reflection prediction echo window, and taking the sampling intervals with a sudden increase in phase change rate and adjacent to the wellside reflection main peak or the adjacent energy region of the main peak as the phase abrupt change region.

[0012] In conjunction with the first aspect, the subtraction or weight reduction processing based on the wellside reflection attenuation curve to obtain the effective echo of the base layer includes: performing amplitude subtraction, interpolation replacement, or evaluation rejection on the sampling segment where the main peak of the wellside reflection is located, wherein the selection rules for amplitude subtraction, interpolation replacement, or evaluation rejection are as follows: when the proportion of overlapping sampling points between the sampling segment where the main peak of the wellside reflection is located and the evaluation window of the base layer bottom surface is greater than a preset overlap threshold, evaluation rejection is adopted; when the width of the sampling segment where the main peak of the wellside reflection is located is less than a preset width threshold, interpolation replacement is adopted; otherwise, amplitude subtraction is adopted; setting attenuation weights for the energy region adjacent to the main peak according to its distance from the main peak of the wellside reflection and its energy intensity; setting attenuation weights for the phase change region according to the phase change rate; when the corresponding signal change in the middle or outer ring detection point conforms to the wellside reflection attenuation curve, increasing the subtraction amount or decreasing the evaluation weight; when the corresponding signal change deviates from the wellside reflection attenuation curve, retaining it as the evaluation content of the effective echo of the base layer.

[0013] In conjunction with the first aspect, the step of extracting the reflection arrival stability component, effective frequency band energy attenuation component, and dominant frequency offset component of the effective echo from the base course within the base course bottom surface reflection evaluation window, and synthesizing the three into a compaction anomaly value, includes: extracting the bottom surface reflection arrival time within the base course bottom surface reflection evaluation window, and forming a reflection arrival stability component based on the difference in bottom surface reflection arrival time between adjacent detection points; calculating the energy attenuation degree of the effective echo from the base course within the effective frequency band, forming an effective frequency band energy attenuation component; calculating the dominant frequency offset degree of the effective echo from the base course, forming a dominant frequency offset component; after suppressing the effective frequency band energy attenuation component or the dominant frequency offset component that matches the wellside reflection attenuation curve, synthesizing the reflection arrival stability component, the effective frequency band energy attenuation component, and the dominant frequency offset component into a compaction anomaly value, wherein the reflection arrival stability component, the effective frequency band energy attenuation component, and the dominant frequency offset component are all defined according to absolute deviation.

[0014] In conjunction with the first aspect, the arrangement of detection points around the well body according to the inner ring, middle ring, and outer ring includes: placing the inner ring detection points in the base reinforcement edge area close to the outer contour of the well body; placing the middle ring detection points in the middle of the base reinforcement area; placing the outer ring detection points in the base transition area away from the well body; and the inner ring detection points, the middle ring detection points, and the outer ring detection points at the same circumferential angle are arranged sequentially along the local normal direction of the outer contour of the well body.

[0015] In conjunction with the first aspect, comparing the compaction anomaly values ​​of the inner, middle, and outer ring detection points in the same radial direction, excluding boundary interference results that match the wellside reflection attenuation curve, and merging consecutive anomaly detection points into a suspected circumferential undercompactment zone includes: when the compaction anomaly value of the inner ring detection point is higher than that of the middle and outer ring detection points, and the compaction anomaly value decreases from the inner ring detection point to the outer ring detection point and is consistent with the wellside reflection attenuation curve, the corresponding direction is marked as a suspected boundary interference direction. The consistency refers to the alignment of the three-point broken line of the compaction anomaly value with the wellside reflection attenuation curve. The Pearson correlation coefficient between the curves is greater than a preset correlation threshold, and the three-point broken line decreases monotonically along the radial distance; when the compaction anomaly value of at least two detection points in the same radial direction exceeds the anomaly judgment threshold and does not conform to the wellside reflection attenuation curve, the corresponding direction is marked as a suspected undercompaction direction; adjacent suspected undercompaction directions are connected according to the circumferential angle sequence, and the corresponding continuous anomaly detection points are merged into a circumferential undercompaction suspected area, where the continuous anomaly detection points refer to detection points that are marked as suspected undercompaction directions in two or more consecutive adjacent circumferential angle directions.

[0016] Secondly, this application provides a non-destructive testing system for road base compaction based on the impact echo method, applied to the base reinforcement area around road manholes or pipeline manholes. The system includes: a parameter acquisition module for acquiring the manhole body outline, base design thickness, wave velocity calibration value, and radial distance and circumferential angle of the detection points relative to the manhole body; an echo acquisition module for arranging detection points around the manhole body in inner, middle, and outer rings, and acquiring the impact echo signals of each detection point; and an echo window and curve generation module for generating a manhole-side reflection prediction echo window and a base bottom surface reflection evaluation window based on the radial distance, the base design thickness, and the wave velocity calibration value, and predicting the echo reflection at the manhole side based on the inner, middle, and outer ring detection points at the same circumferential angle. The reflection changes within the window form a wellside reflection attenuation curve; the boundary echo processing module is used to identify the wellside reflection main peak, the energy region adjacent to the main peak, and the phase abrupt change region within the wellside reflection prediction echo window, and to perform subtraction or weight reduction processing based on the wellside reflection attenuation curve to obtain the effective echo of the base layer; the compaction value formation module is used to extract the reflection arrival stability component, effective frequency band energy attenuation component, and main frequency offset component of the effective echo of the base layer within the base layer bottom surface reflection evaluation window, and to synthesize the three into a compaction anomaly value; the suspected area output module is used to compare the compaction anomaly values ​​of the inner ring, middle ring, and outer ring detection points in the same radial direction, to exclude boundary interference results that match the wellside reflection attenuation curve, and to merge continuous anomaly detection points into a circumferential undercompacted suspected area.

[0017] The method and system provided in this application have the following advantages compared with the prior art: Firstly, this application parametrically models the outer contour of the well body, the design thickness of the base course, and the wave velocity calibration value, and predefines the possible occurrence range of well-side reflection and the effective evaluation range of base course bottom reflection on the time axis, thereby distinguishing the boundary reflection interference caused by the well body from the base course bottom reflection in the time domain, and avoiding misinterpreting well body reflection as compaction anomaly.

[0018] Secondly, this application establishes a well-side reflection attenuation curve by comparing the reflection changes of the inner ring detection point, middle ring detection point and outer ring detection point at the same circumferential angle. The well-side reflection attenuation curve quantitatively describes the law of well-side reflection intensity attenuating with the increase of radial distance, so that the subsequent subtraction or weight reduction processing has a quantitative basis and can effectively retain the undercompacted signal that actually exists in the base layer around the well.

[0019] Third, this application deducts, reduces the weight of or evaluates and eliminates the main peak of wellside reflection, the energy zone adjacent to the main peak and the phase change zone, and performs differentiated processing according to whether the component signal changes conform to the wellside reflection attenuation curve. This can suppress boundary interference while preserving the effective echo of the base layer to the greatest extent and improve the purity of compaction anomalies.

[0020] Fourth, this application synthesizes the compaction anomaly value by combining the reflection arrival stability component, the effective frequency band energy attenuation component, and the main frequency offset component in a multi-component manner, and suppresses the component that matches the wellside reflection attenuation curve before synthesizing it, so that the final compaction anomaly value can better reflect the true undercompaction suspicion of the base layer; furthermore, by comparing the compaction anomaly values ​​and their attenuation rules of the three ring detection points in the same radial direction, the continuous anomaly detection points are merged into a circumferential undercompaction suspected area, which can realize the planar identification and continuous presentation of the undercompaction suspected area of ​​the base layer around the well, avoid misjudgment and omission, and improve the accuracy of non-destructive testing of undercompaction of the base layer around the well. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application 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 this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of the overall process of the non-destructive testing method for road base compaction based on the impact echo method provided in the embodiments of this application; Figure 2 A plan view showing the layout of detection points in the inner, middle, and outer rings around the well body, as provided in this embodiment of the application. Figure 3A schematic diagram of the time axis division of the wellside reflection prediction echo window and the base layer bottom surface reflection evaluation window provided in the embodiments of this application; Figure 4 This is a schematic diagram illustrating the formation of the wellside reflection attenuation curve provided in an embodiment of this application. Figure 5 A schematic diagram illustrating the identification of the main peak, the energy region adjacent to the main peak, and the phase abrupt change region within the wellside reflection prediction echo window provided in this application embodiment; Figure 6 This is a schematic diagram of the structure of the non-destructive testing system for road base compaction based on the impact echo method provided in this application embodiment. Detailed Implementation

[0023] The technical solutions in the embodiments of this application will be clearly and thoroughly described below with reference to the accompanying drawings.

[0024] The method described in this application is applied to the base reinforcement area around road inspection wells or pipeline wells. For ease of understanding, several terms involved in this application are explained below. Base reinforcement area refers to the area of ​​the base layer within a certain radial range outside the inspection well or pipeline well, where additional compaction or material reinforcement is applied to compensate for limitations in backfill compaction processes. Well side reflection refers to the reflected wave generated in the impact echo signal by geometrically discontinuous interfaces such as the well wall and the outer edge of the well ring. Base layer bottom reflection refers to the reflected wave generated in the impact echo signal by the interface between the base layer and the underlying structure. Well side reflection attenuation curve refers to the curve describing the relationship between the intensity of well side reflection and the decrease in radial distance from the detection point to the well body. Circumferential undercompactment suspected area refers to the sector or ring-shaped area formed by consecutively adjacent detection points along the circumference of the well body that are suspected of undercompactment. The above terms should be understood in conjunction with the solution of this application and should not be interpreted narrowly.

[0025] In this embodiment, the implementers of the method are divided into two categories: testing personnel and testing equipment. Testing personnel are responsible for on-site operational tasks, including parameter acquisition, testing point setup, and application of impact excitation. The testing equipment includes an impact source, sensors, and a data acquisition and processing unit, responsible for acquiring and storing impact echo signals and subsequent signal processing tasks, including echo window generation, reflection feature identification, compaction anomaly calculation, and output of suspected undercompacted areas. Testing personnel and testing equipment collaborate to complete the method of this embodiment.

[0026] refer to Figure 1 The non-destructive testing method for road base compaction based on the impact echo method provided in this application includes six steps from S100 to S600. Each step will be described in detail below with reference to the accompanying drawings.

[0027] S100, acquire the outer contour of the well body, the base layer design thickness, the wave velocity calibration value, and the radial distance and circumferential angle of the detection point relative to the well body.

[0028] Specifically, S100 can be further subdivided into S101 to S104: S101, determine the outer contour of the manhole body based on the outer edge of the manhole ring, the outer edge of the manhole wall, or the outer edge of the pipeline manhole.

[0029] Inspectors determine the external contour of the manhole. Based on the outer edge of the manhole ring, the outer edge of the manhole wall, or the outer edge of the pipeline manhole, inspectors determine the external contour of the manhole, obtaining a geometric description of the external contour. Specific methods for determining the external contour include, but are not limited to: inspectors using a total station or measuring tape to measure the outer edge of the manhole ring on-site; inspectors retrieving the outer diameter and axial coordinates of the pipeline manhole from municipal pipeline as-built documentation; and inspectors using a laser rangefinder to scan the outer edge of the manhole wall. The external contour of the manhole is used as a reference for delineating the base reinforcement zone and determining radial distances in subsequent steps.

[0030] S102, determine the base layer design thickness based on the base layer construction design documents or on-site thickness measurement results.

[0031] The inspectors determine the base course design thickness. Based on the base course construction design documents or on-site thickness measurements, the inspectors determine the base course design thickness, denoted as h, in meters. Specific methods for determining the base course design thickness h include, but are not limited to: the inspectors reading the design thickness from the base course construction design documents or mix design documents; or the inspectors obtaining the measured thickness on-site in a known compaction state area using ground-penetrating radar, ultrasonic thickness measurement, or similar methods. The base course design thickness h is used in subsequent steps to estimate the theoretical arrival time of reflection from the base course surface.

[0032] S103, collect impact echo signals at a base location that is far from the well body and where the compaction state has been confirmed, and obtain wave velocity calibration values ​​based on the arrival time of the reflection from the bottom surface of the base.

[0033] The testing personnel calibrated the wave velocity. Impact echo detection points were established at locations on the base course, far from the well body and where the compaction state had been confirmed, serving as reference points. At these reference points, the testing personnel applied impact excitation from the impact source of the testing equipment, and the sensors of the equipment simultaneously acquired the impact echo signals. The testing equipment identified the arrival time of the reflection from the bottom surface of the base course from the impact echo signals, recording it as... The testing equipment divides twice the designed thickness h of the base layer by the time it takes for the reflection from the bottom surface of the base layer to reach the target. The wave velocity calibration value was obtained. This serves as a reference value for the base wave velocity in the entire well perimeter detection area. Wave velocity calibration value. The calculation formula is shown in equation (1) below: (1) In the formula, h represents the design thickness of the base layer, with the dimension of length and the unit of meters; The time interval from the moment the impact excitation is applied to the moment the reflected wave from the bottom surface of the base layer is received by the sensor at the reference position is the two-way arrival time of the reflected wave from the bottom surface of the base layer. The dimension is time and the unit is seconds. The dimension of is length divided by time, and the unit is meters per second. All terms in the formula are calculated as physical quantities with the dimension of velocity, ensuring dimensional consistency. The rationale for this calibration method is that the impact excitation propagates through the base layer to the bottom surface and is reflected back to the sensor; the propagation path length is twice the thickness of the base layer, and the propagation time is... Therefore, the wave speed is equal to the propagation path length divided by the propagation time, which is consistent with the basic physical meaning of wave propagation.

[0034] S103 at calibrated wave velocity Simultaneously, the following reference value is calculated and stored from the same impact echo signal collected by the detection equipment at the reference location, serving as the calibration baseline for subsequent steps: effective frequency band energy at the reference location. The calculation method is to take the reflection evaluation window of the base surface. After the internal signal undergoes Fast Fourier Transform, it is within the effective frequency band. The square integral of the internal spectrum amplitude; the dominant frequency at the reference position. The calculation method is to take the reflection evaluation window of the base surface. The frequency at which the internal signal has the maximum spectral amplitude after Fast Fourier Transform; the mean value of the compaction anomaly CV at the reference location. and standard deviation The mean with standard deviation This is obtained by statistically analyzing N sets of impact echo signals obtained from N repeated impact excitations at the reference location, calculated according to step S500, and N values, where N is not less than 10. Since the reference location is far from the wellbore, wellside reflection in its impact echo signal is negligible. Therefore, the effective echo ER of the base layer at the reference location is actually equivalent to the base layer bottom surface reflection evaluation window of the signal itself. The signal segments within can be used directly in S502 and S503 without the need for subtraction or weight reduction processing in step S400. , , , and Together they form a reference set, which is used in subsequent steps S502, S503, and S602.

[0035] S103-A, Field Calibration Procedure. The reference location, the number of reference samples N, the number of repeated impacts mentioned in S103, and the various coefficients and thresholds used in subsequent steps S400 to S600 must be determined through the field calibration procedure described in this step S103-A before actual application. Specifically, it includes the following nine items from S103-A(a) to S103-A(i): S103-A(a) Basis for confirming benchmark location: The benchmark location shall simultaneously meet the following conditions: it shall be located within the same batch of base course construction of the road section being inspected; the distance from any manhole, pipeline manhole, or curbstone outer edge shall be no less than five times the base course design thickness h; and the compaction degree shall be verified by core sampling or sand filling method to meet the design requirements.

[0036] S103-A(b) Number of Reference Samples and Number of Repeated Impacts: At the confirmed reference locations, the testing personnel shall evenly distribute no fewer than three testing points; at each testing point, the impact excitation shall be repeated at least three times, i.e., the number of reference samples N shall be no less than 9. The testing equipment shall calculate the compaction anomaly value CV for each of the N sets of impact echo signals according to step S500, obtaining N CV values, and calculate the mean value based on these values. and sample standard deviation .

[0037] S103-A(c) and Methods for determining the value: The prominentness coefficient of the main peak of well-side reflection relative to the local background amplitude. This is the abrupt change coefficient of the phase change rate. The detection equipment takes a well-side reflection prediction echo window from the same impact echo signal at the reference location. Outside of the static window segment, the mean and standard deviation of the amplitude and phase change rate within the static window segment are statistically analyzed; Take an integer that makes the upper bound of 3 × standard deviation / mean correspond to the given signal-to-noise ratio design value. In engineering, it is usually taken as 3 or 4. Take 2 or 3 based on the same principle.

[0038] S103-A(d)η、 , , Determination of η: η is the maximum weighting coefficient. To increase the coefficient, The attenuation coefficient is... The suppression coefficient. On a calibration block where wellside reflection interference is known to exist but the compaction state of the base course is controllable, the testing personnel measured η, , , Within their respective value ranges, parameter scanning is performed, with the optimization objective being to minimize the sum of the "false positive rate of suspected direction due to boundary interference" and the "false negative rate of suspected direction due to undercompaction," and appropriate parameter combinations are selected. In the absence of calibration blocks, the empirical value η=0.8 can be used. =1.5, =0.5, =0.3 is the initial setting, and is corrected when the CV distribution at the on-site calibration reference position shows a large abnormal error.

[0039] The determination rules for α, β, and γ in S103-A(e) are as follows: α, β, and γ are the composite weights of the reflection arrival stability component, the effective frequency band energy attenuation component, and the dominant frequency offset component, respectively, satisfying α+β+γ=1. When training samples with known compaction states (e.g., core sampling verification) are available, the testing personnel scan α, β, and γ on the simplex with a step size of 0.1, selecting the combination of values ​​with the highest consistency between CV and the known compaction degree order on the training samples; in the absence of training samples, the initial weights can be equalized as α=β=γ=1 / 3, and then fine-tuned according to the field data.

[0040] The rule for determining the value of S103-A(f)k: k is the anomaly detection threshold. The multiples in k are usually 2 or 3. When the road section being tested is sensitive to missed detections (e.g., important municipal arterial roads), k=2 is used; when the road section being tested is sensitive to false detections (e.g., preliminary area surveys), k=3 is used.

[0041] S103-A(g) effective frequency band Determination method: Based on the thickness-frequency relationship of the impact echo method, the theoretical dominant frequency of the reflection from the bottom surface of the base layer is determined. The testing personnel will set a lower limit. Take it as 0.5× , will the upper limit Take 3× Up to 4× When the thickness of the base layer or the wave velocity calibration value deviates from the normal value on site, and Adjust accordingly based on the above proportions.

[0042] S103-A(h) Extended Width , Method for determining: , These represent the expanded widths of the wellside reflection prediction echo window and the base layer bottom surface reflection evaluation window, respectively. , Values ​​were taken as 1 to 2 times the impact excitation pulse width; when the sampling rate was low or the uncertainty of the wave velocity calibration value was large. , It should be increased proportionally to cover the time of arrival offset.

[0043] S103-A(i) Determination method of overlap threshold and width threshold: The "preset threshold for the proportion of overlapping sampling points" mentioned in step S404 is usually taken as 20%; the "width threshold" is usually taken as 0.5 times the number of sampling points corresponding to the impact excitation pulse width. The preset correlation threshold is usually taken as 0.9. The above thresholds can be adjusted by ±20% in the field based on the calibration results.

[0044] The parameters and thresholds obtained in the above-mentioned on-site calibration process together constitute the calibration baseline of the method of this application, which is stored in the testing equipment for direct use in subsequent steps S200 to S600, so as to ensure the reproducibility of test results under different on-site, different equipment, and different base conditions.

[0045] S104, using the geometric center of the well body's outer contour or the projection point of the pipeline well axis as an angular reference, determine the radial distance and circumferential angle of the detection point.

[0046] The inspectors determine the radial distance and circumferential angle. Using the geometric center of the wellbore's outer contour or the projection point of the pipeline well axis as the angular reference, the inspectors establish a planar polar coordinate system. The horizontal distance from each inspection point to the angular reference is taken as the radial distance R, in meters. The azimuth angle of each inspection point relative to a predetermined zero direction is taken as the circumferential angle. The unit is degrees; for example, the geometric center of the wellbore's outer contour points due north. S104 uses polar coordinates to describe the location of the detection point because the wellbore reinforcement zone is distributed in a ring around the well body. The intensity and location of the wellside reflection mainly depend on the radial distance R from the detection point to the well body, and vary at different circumferential angles. The surfaces have different boundary geometries, using radial distance R and circumferential angle. It can most directly express the geometric parameters required for subsequent steps.

[0047] S200, detection points are set up around the well body in the form of inner ring, middle ring and outer ring, and the impact echo signal of each detection point is collected.

[0048] Specifically, S200 can be further divided into S201 and S202: S201, the inner ring detection point is placed in the base reinforcement edge area close to the outer contour of the well body; the middle ring detection point is placed in the middle of the base reinforcement area; and the outer ring detection point is placed in the base transition area away from the well body.

[0049] The testing personnel deployed testing points sequentially in the inner, middle, and outer rings. The inner ring testing points were placed near the base reinforcement edge area of ​​the wellbore's outer contour; the middle ring testing points were placed in the center of the base reinforcement area; and the outer ring testing points were placed in the base transition area away from the wellbore. The inner, middle, and outer ring testing points at the same circumferential angle were sequentially deployed along the local normal direction of the wellbore's outer contour.

[0050] refer to Figure 2 Well body W is located in the middle of the base reinforcement zone. The inner ring (IR), middle ring (MR), and outer ring (OR) are arranged outwards sequentially based on the outer contour of the well body. In each circumferential angle direction, one inner ring detection point, one middle ring detection point, and one outer ring detection point are arranged sequentially along the local normal direction of the outer contour of the well body. Figure 2 Taking a specific circumferential angle as an example, P1 is the inner ring detection point at that angle, P2 is the middle ring detection point at the same angle, and P3 is the outer ring detection point at the same angle. This arrangement along the normal direction is used because subsequent steps require comparing the reflection characteristics of the inner, middle, and outer ring detection points along a direction where the radial distance monotonically increases, thus facilitating the establishment of a stable wellside reflection attenuation curve. The circumferential angles can be evenly spaced around the wellbore circumference according to site conditions, for example... Figure 2 The diagram shows eight circumferential angle directions arranged at 45-degree intervals. In situations with complex circumferential geometry, inspectors may use even closer circumferential angle intervals to increase the number of directions. This application does not impose any special limitations on the intervals or number of circumferential angles.

[0051] S202, the inner ring detection point, the middle ring detection point and the outer ring detection point at the same circumferential angle are arranged sequentially along the local normal direction of the well body outline.

[0052] Inspection personnel, in collaboration with inspection equipment, collect impact echo signals from each inspection point. At each inspection point, the personnel sequentially apply impact excitation using the impact source of the inspection equipment. The sensors of the inspection equipment simultaneously collect the surface vibration response, which is then converted into a time-series impact echo signal and stored by the data acquisition and processing unit of the inspection equipment. The impact sources used in the inspection equipment include, but are not limited to, steel ball drop hammer impact sources and electromagnetic impact sources; the sensors used include, but are not limited to, accelerometers and displacement sensors. After the impact source applies instantaneous impact excitation to the surface of the inspection point, the stress wave propagates in the base medium and is reflected at discontinuous interfaces such as the well wall interface and the bottom surface of the base. The reflected waves are received by the sensors and form the impact echo signal for subsequent analysis.

[0053] S300, based on the radial distance, the base layer design thickness and the wave velocity calibration value, a wellside reflection prediction echo window and a base layer bottom surface reflection evaluation window are generated, and a wellside reflection attenuation curve is formed based on the reflection changes of the inner ring, middle ring and outer ring detection points within the wellside reflection prediction echo window at the same circumferential angle.

[0054] Specifically, S300 can be further subdivided into S301 to S305: S301, determine the wellside reflection arrival time interval based on the radial distance of the detection point and the wave velocity calibration value, and expand the wellside reflection arrival time interval into a wellside reflection prediction echo window.

[0055] The detection equipment generates a wellside reflection prediction echo window. The testing equipment is calibrated based on the radial distance R of the testing point and the wave velocity value. Determine the theoretical arrival time of wellside reflection and the arrival time of the wellside reflection theory. Extended to wellside reflection prediction echo window Wellside reflection theory arrival time The calculation formula is shown in equation (2) below: (2) In the formula, R is the radial distance from the detection point to the outer contour of the well body, in meters; This is the wave speed calibration value, in meters per second; The unit is seconds. The physical meaning of this formula is: the stress wave generated by the impact excitation travels horizontally from the detection point to the well wall and is reflected back to the detection point. The round-trip path length is twice R, and the propagation time is... .

[0056] Wellside reflection prediction echo window Arrival time based on wellside reflection theory Expand forward and backward by the same amount Each unit of time is obtained, that is Time interval Expand width The method described in S103-A(h) determines the pulse width of the impact excitation, the sampling rate, and the uncertainty of the wave velocity calibration value. In practical applications, the extended width is usually... It is set to a pulse width order of magnitude, for example, one to two times the pulse width of the impact excitation pulse, in order to cover the arrival time offset. This application extends the width... The specific value is not specifically limited and can be adjusted according to the actual situation in practical applications.

[0057] S302, determine the arrival time interval of the reflection from the bottom surface of the base layer based on the base layer design thickness and the wave velocity calibration value, and expand the arrival time interval of the reflection from the bottom surface of the base layer into an evaluation window for the reflection from the bottom surface of the base layer.

[0058] The testing equipment generates a reflection evaluation window for the base layer. The testing equipment is calibrated based on the base layer design thickness h and wave velocity value. Determine the theoretical arrival time of reflection from the base layer. And the theoretical arrival time of the reflection of the base surface. Expanded into a base surface reflection evaluation window The theoretical arrival time of reflection from the base surface. The calculation formula is shown in equation (3) below: (3) In the formula, h represents the design thickness of the base layer, in meters; This is the wave velocity calibration value, in meters per second; The unit is seconds, and Maintain consistency. The physical meaning of this formula is: the stress wave generated by the impact excitation starts from the detection point, propagates vertically to the bottom surface of the base layer, and then reflects back to the detection point. The round-trip path length is twice the design thickness h of the base layer, and the propagation time is... .

[0059] Evaluation window for reflection of base surface Arrival time based on the theory of reflection from the base surface Expand forward and backward by the same amount Each unit of time is obtained, that is Time interval Expand width Determination principles and expansion width same.

[0060] S303, when the wellside reflection prediction echo window overlaps with the base bottom surface reflection evaluation window, the overlapping part is marked as a boundary interference candidate area.

[0061] The detection equipment marks the boundary interference candidate area. The detection equipment determines the wellside reflection prediction echo window. Evaluation window for reflection of base surface Does overlap occur on the timeline: when and When overlap occurs, the detection equipment marks the overlapping area as a candidate region for boundary interference. ;when and When no overlap occurs, the detection device does not mark boundary interference candidate regions. (Reference) Figure 3 Wellside reflection prediction echo window Evaluation window for reflection of base surface The arrival time of wellside reflections is covered on the time axis. and the time of reflection from the bottom surface of the base layer The overlapping area of ​​the surrounding sampling intervals constitutes the boundary interference candidate region. Set boundary interference candidate areas. The purpose is to: evaluate the reflection of the underlying surface of the base layer in subsequent tests. During the reflection feature extraction process, candidate regions falling into the boundary interference area are considered. The features within the well are subject to stricter deduction or weight reduction to avoid wellside reflections being mixed into the evaluation scope of base course bottom surface reflections.

[0062] S304, extract the reflection peak value, energy area or phase change amplitude of the inner ring, middle ring and outer ring detection points at the same circumferential angle within the wellside reflection prediction echo window.

[0063] The detection equipment extracts the reflection characteristics of the three ring detection points. The equipment selects a set of inner ring, middle ring, and outer ring detection points at the same circumferential angle; the equipment then extracts wellside reflection prediction echo windows from the impact echo signals of the three detection points. Within a signal segment, the detection equipment extracts the reflection peak, energy area, or phase change amplitude as reflection characteristics for each signal segment. The reflection peak is extracted by taking the maximum amplitude within the signal segment, with dimensions consistent with the original signal amplitude. The energy area is extracted by taking the integral of the square of the amplitude over time within the signal segment, with dimensions of amplitude squared multiplied by time. The phase change amplitude is extracted by performing a Hilbert transform on the signal segment to obtain the instantaneous phase and then taking the range of the instantaneous phase, with dimensions in radians. Since the dimensions of these three reflection characteristics are different and cannot be directly compared between different types, when forming a wellside reflection attenuation curve between the same set of three-ring detection points, only one of the above three reflection characteristics must be selected as the sole indicator of the attenuation curve; mixing different types is not allowed. Detection personnel can select one of the above three reflection characteristics as the basis for the attenuation curve based on the on-site signal-to-noise ratio; this application does not impose any special restrictions on this.

[0064] S305, sort the reflection peak, energy area or phase change amplitude according to the radial distance of the detection point; determine the reflection change relationship that attenuates as the radial distance increases as the wellside reflection attenuation curve corresponding to the circumferential angle.

[0065] The detection equipment generates a wellside reflection attenuation curve. The equipment sorts the reflection peak value, energy area, or phase change amplitude according to the radial distance R between the detection points, obtaining three data points. The equipment then connects these three data points sequentially in ascending order of radial distance R to form the wellside reflection attenuation curve corresponding to the circumferential angle. (Reference) Figure 4 For a given circumferential angle, the radial distances between the three detection points—inner ring IR, middle ring MR, and outer ring OR—are denoted as follows: , , The reflection characteristic values ​​of the three are derived from The larger value at the point decreases to The smaller value at the point is used to form a monotonically decreasing wellside reflection attenuation curve. The fitting method used in this application can be piecewise linear fitting, monotonically spline fitting, or directly using a three-point broken line as a simplified wellside reflection attenuation curve. This application does not impose special limitations on the fitting method. In practical applications, an appropriate method can be selected based on the number of detection points and the noise level. When the formed three-point broken line does not satisfy the condition of monotonically decreasing radial distance, the detection device marks the circumferential angle direction as "the direction of insignificant attenuation law". In subsequent steps S407, S504, and S601, this direction will no longer be suppressed or excluded on the ground of "meeting the wellside reflection attenuation curve", thereby avoiding the mistaken suppression of the true undercompacted signal of the base layer.

[0066] The reason why a wellside reflection attenuation curve must be formed for S305 is that the wellside reflection intensity should usually decrease monotonically with the increase of radial distance, while the reflection change caused by the undercompacted area of ​​the base layer does not have this systematic monotonically decreasing law. The two can be distinguished by the wellside reflection attenuation curve. In S400 to S600, the wellside reflection attenuation curve will serve as a quantitative basis for determining whether it is a well body boundary interference.

[0067] S400 identifies the main peak of wellside reflection, the energy region adjacent to the main peak, and the phase change region within the wellside reflection prediction echo window, and performs subtraction or weight reduction processing based on the wellside reflection attenuation curve to obtain the effective echo of the base layer.

[0068] Specifically, S400 can be further subdivided into S401 to S407: S401, within the wellside reflection prediction echo window, determine the position of the peak value that stands out based on the local background amplitude, and take the peak position as the main peak of the wellside reflection.

[0069] The detection equipment identifies the main peak (PK) of the wellside reflection. The detection equipment uses the wellside reflection prediction echo window. Internal calculation of local background amplitude The detection equipment uses a wellside reflection prediction echo window. Internal search amplitude is higher than All sampling points, of which A prominence coefficient greater than 1 The rules for determining the value are given in S103-A(c). In practical applications, the testing personnel can... Set to 3 or 4; the detection device will use the sampling point with the largest amplitude among all sampling points as the wellside reflection main peak PK. Local background amplitude. The determination methods include, but are not limited to: well-side reflection prediction echo window of the detection equipment. The root mean square of the signal outside the static window is used as the local background amplitude. ; or the detection equipment uses a wellside reflection prediction echo window The median amplitude, excluding the highest peaks, is taken as the local background amplitude. .

[0070] S402, with the well-side reflection main peak as the center, search forward and backward for sampling intervals where the energy is continuously higher than the local background energy, and take the sampling interval as the energy region near the main peak.

[0071] The detection equipment identifies the energy region NE adjacent to the main peak. Centered on the well-side reflection main peak PK, the equipment accumulates energy forward and backward that is consistently higher than the local background energy. The sampling range; when the detection equipment encounters energy drop-off to the local background energy When sampling points are reached, accumulation is stopped; the detection equipment will collect the accumulated data, which includes the wellside reflection main peak PK and whose energy is continuously higher than the local background energy. The sampling interval is designated as the energy region NE adjacent to the main peak. That is, the energy region NE adjacent to the main peak includes the sampling segment containing the well-side reflection main peak PK. In subsequent processing steps S404 and S405, the sampling segment containing the well-side reflection main peak PK is processed only according to the method specified in S404; the attenuation weight set in S405... It only applies to the portion of the energy region NE adjacent to the main peak, excluding the sampling segment where the well-side reflection main peak PK is located, thus avoiding repeated processing of the sampling segment where the well-side reflection main peak PK is located. Local background energy The determination method and local background amplitude Similarly, including but not limited to: well-side reflection prediction echo windows for detection equipment. The average instantaneous energy of the signal outside the static window is used as the local background energy. ; or the detection equipment uses a wellside reflection prediction echo window The median energy, excluding the energies corresponding to the highest and lowest peaks, is taken as the local background energy. .

[0072] S403, perform phase continuity analysis on the signal within the wellside reflection prediction echo window, and take the sampling interval with a sudden increase in phase change rate and adjacent to the wellside reflection main peak or the energy region adjacent to the main peak as the phase change region.

[0073] The detection equipment identifies the phase abrupt change region (PJ). The detection equipment predicts the echo window based on wellside reflections. The signal within is subjected to Hilbert transform to obtain the instantaneous phase. The detection equipment measures the instantaneous phase. Find the first-order time difference to obtain the phase change rate. The detection equipment will measure the phase change rate. Exceeding its local mean The sampling interval located near the main reflection peak PK or the adjacent energy region NE on the well side is designated as the phase abrupt change region PJ. A mutation coefficient greater than 1 The rules for determining the value are given in S103-A(c). In practical applications, the testing personnel can... Set it to 2 or 3. The Hilbert transform is a well-known algorithm in the field of signal processing, and its specific derivation will not be elaborated here.

[0074] S404 to S406 are processed according to the rules shown in Table 1 for the main peak PK, the energy region NE adjacent to the main peak, and the phase change region PJ of the wellside reflection. The combined effect of the processing results is used to obtain the effective echo ER of the base layer.

[0075] Table 1: Rules for Treating Wellside Reflection Zones

[0076] S404 performs amplitude subtraction, interpolation replacement, or evaluation elimination on the sampling segment where the main peak PK of the wellside reflection is located.

[0077] Among them, amplitude subtraction refers to the detection equipment subtracting the estimated amplitude of wellside reflection from the sampling amplitude of the main peak section according to a predetermined subtraction function; interpolation replacement refers to the detection equipment using the undisturbed sampling amplitude on both sides of the main peak to perform smooth interpolation on the sampling of the main peak section, and the smooth interpolation method includes, but is not limited to, linear interpolation and cubic spline interpolation; evaluation elimination refers to the detection equipment excluding the main peak section from the evaluation range when synthesizing compaction anomalies in the subsequent process.

[0078] S404 selects between the three processing methods according to the following deterministic rules: (1) First, the detection equipment calculates the ratio of the number of overlapping sampling points on the time axis between the sampling segment where the main peak reflection PK is located on the well side and the reflection evaluation window WB on the bottom surface of the base layer, to the total number of sampling points in the main peak segment, which is denoted as the overlap ratio r. If the overlap ratio r is greater than the preset overlap threshold... According to S103-A(i), which is usually taken as 0.2, evaluation exclusion is adopted, that is, the main peak segment is excluded from the evaluation scope of step S500. This is because when the main peak segment highly overlaps with WB, any subtraction or interpolation will inevitably interfere with the evaluation of the reflection of the base surface.

[0079] (2) Secondly, if the overlap ratio r does not exceed The detection equipment further calculates the ratio of the number of sampling points occupied by the main peak segment to the number of sampling points corresponding to the impact excitation pulse width; if this ratio is less than the preset width threshold... (According to S103-A(i), usually 0.5 is taken, that is, the width of the main peak segment is shorter than half the pulse width), then interpolation replacement is used, because the main peak segment is narrow and the sampling amplitude on both sides that is not disturbed can effectively support interpolation smoothing.

[0080] (3) In other cases, amplitude subtraction is used. The predetermined subtraction function is based on the peak amplitude of PK. Maximum value, local background amplitude The subtraction function is a subtraction function that minimizes the value and decays along the center of the main peak outwards in a Gaussian or cosine half-bell shape. Specifically, the subtraction amplitude at sampling point j... Determine using the following formula: ,in The time corresponding to sampling point j. The time of the sampling point where PK is located. It is 1 / 3 of the half width of the main peak segment.

[0081] The interpolation interval length is equal to the extension of 3 sampling points at each end of the main peak segment. The evaluation rejection range is the entire main peak segment. The processing results generated by the above three processing methods are used as the corresponding sampling amplitude of the effective echo ER of the base layer within the main peak segment, which is directly used in subsequent S500 steps.

[0082] S405, set attenuation weights for the energy region adjacent to the main peak according to its distance from the well-side reflected main peak and its energy intensity.

[0083] The detection equipment sets attenuation weights for the portion of the energy region NE adjacent to the main peak, excluding the sampling section where the well-side reflected main peak PK is located (hereinafter referred to as NE\PK section), according to its distance from and energy intensity to the well-side reflected main peak PK. Decay weight The setting rule is: the closer the sampling point j is to the main peak PK of the wellside reflection, the better. The smaller the value, the closer the energy of sampling point j is to the peak energy of the well-side reflection main peak PK. The smaller. This application adopts... The calculation formula is shown in equation (4) below: (4) In the formula, , The time distance from sampling point j to the main reflection peak PK on the well side is... The half-width of the energy region NE adjacent to the main peak This represents the dimensionless proximity score, with a value range of [0, 1]. , Let j be the instantaneous energy at sampling point j. This refers to the instantaneous energy reflected from the main peak PK at the well side. represents the dimensionless energy proximity, with a value range of [0, 1]. This is the maximum weighting coefficient, with a value range of (0, 1). The rules for determining the value are given in S103-A(d). In practical applications, inspectors can... Set to 0.8; The attenuation weight for sampling point j, with a value range of... Dimensionless. Decay weight. In subsequent steps, it acts as a multiplier on the amplitude or energy contribution of sampling point j, that is, sampling point j contributes as a multiplier to the energy integral of S502. This method involves participating in the calculation, thereby achieving weight reduction and suppression.

[0084] Using formula (4) as an example: Let the half-width of NE be... for Seconds, for a sampling point j within the NE\PK section, the time distance from its location to the main reflection peak PK on the well side. for Seconds indicate proximity. The instantaneous energy at sampling point j Instantaneous energy at the main peak PK of the well side reflection If it is 0.6 times that of the energy level, then the energy level is close to that of the energy level. Take the maximum weighting coefficient. If the value is 0.8, then the attenuation weight can be calculated using formula (4). That is, the energy contribution of sampling point j is reduced to 76% of its original value.

[0085] S406, set the attenuation weight for the phase change region according to the phase change rate.

[0086] The detection equipment sets attenuation weights for the phase change region PJ according to the phase change rate. Decay weight The calculation formula is shown in equation (5) below: (5) In the formula, , Let j be the rate of phase change at sampling point j. This represents the maximum rate of phase change within the phase transition region PJ. represents the dimensionless phase change rate proximity, with a value range of [0, 1]. With formula (4) The meaning is the same, representing the maximum weighting coefficient; The attenuation weight for sampling point j, with a value range of... , dimensionless. Using formula (5) as an example: Let the phase change rate of a sampling point j within PJ be... Maximum phase change rate If the phase change rate is 0.8 times that of the phase change rate, then the phase change rate is close to the phase change rate. Take the maximum weighting coefficient. If the value is 0.8, then the attenuation weight can be calculated using formula (5). That is, the energy contribution of sampling point j is reduced to 36% of its original value.

[0087] Figure 5 Furthermore, a set of typical signal waveforms within the wellside reflection prediction echo window and the visual classification of the three types of regions processed by S401 to S406 are presented. Figure 5 In the diagram: the horizontal axis represents time t, and the vertical axis represents the signal amplitude and instantaneous phase; the outer box represents the overall range of the wellside reflection prediction echo window; the horizontal dashed line represents the local background amplitude; the area in the center, covering the highest peak of the waveform, filled with diagonal lines and marked PK, is the sampling segment where the main peak of the wellside reflection is located; the areas distributed on the left and right sides of the sampling segment where PK is located, filled with vertical lines and marked NE\PK, are the part of the energy region NE adjacent to the main peak, excluding PK, and the overall range of NE is composed of the sampling segment where PK is located and the NE\PK parts on both sides; the area located near the right side of NE, filled with horizontal lines and marked PJ, is the phase change region. The three types of regions are distinguished by different profile line directions and text markings. The regions identified by the above three types of filling blocks have the following one-to-one correspondence with steps S401 to S406: S401 Identification Figure 5 The diagonal fill block in the image, i.e., the sampling segment where PK is located, is identified by S402. Figure 5 The union of the diagonal fill block and the vertical fill blocks on both sides, i.e., the entire range of NE, is recognized by S403. Figure 5 The horizontal fill blocks, i.e., PJ, are used in the sampling process. S404 only performs amplitude subtraction, interpolation replacement, or evaluation rejection on the sampling segments of PK covered by the diagonal fill blocks. S405 only sets attenuation weights based on distance and energy intensity for the NE / PK portions covered by the vertical fill blocks. S406 only sets attenuation weights based on phase change rate for the PJ covered by the horizontal fill blocks. These three types of fill blocks do not overlap on the time axis, thus ensuring that the sampling segments of PK are not processed repeatedly by S404 and S405. S407 then combines... Figure 4The wellside reflection attenuation curves shown above are used to differentiate the three types of processing results based on whether they "conform to the attenuation curve" or "deviate from the attenuation curve".

[0088] S407, when the corresponding signal change in the middle or outer ring detection point conforms to the wellside reflection attenuation curve, the deduction amount is increased or the evaluation weight is reduced; when the corresponding signal change deviates from the wellside reflection attenuation curve, it is retained as the evaluation content of the effective echo of the base layer.

[0089] The detection equipment differentiates based on whether it conforms to the wellside reflection attenuation curve. The equipment extracts the change in the same characteristic quantity as the inner ring detection point from the corresponding signals of the middle and outer ring detection points, and compares this change with the wellside reflection attenuation curve formed in step S305. The "corresponding signal change" refers to the characteristic value (one of three: reflection peak value, energy area, or phase change amplitude) of the same characteristic quantity as the inner ring detection point on the middle and outer ring detection points, and forms a three-point broken line according to the radial distance R from small to large. When the corresponding signal change in the middle or outer ring detection point conforms to the wellside reflection attenuation curve, i.e., the Pearson correlation coefficient between the three-point broken line and the attenuation curve formed in step S305 is greater than a preset correlation threshold, and the three-point broken line monotonically decreases along the radial distance, the detection equipment increases the deduction amount or decreases the evaluation weight. For example, the detection equipment multiplies the amplitude deduction amount in step S404 by an enhancement factor. Or the attenuation weights in steps S405 and S406. , Multiply by the attenuation coefficient Among them, the improvement coefficient The value range of is (1, 2], and the attenuation coefficient is The value range of is (0, 1). , The rules for determining the value are given in S103-A(d). In practical applications, inspectors can... Set it to 1.5, and The value is set to 0.5. When the corresponding signal change at the detection point in the middle or outer ring deviates from the wellside reflection attenuation curve, the detection equipment retains the corresponding signal as the evaluation content of the effective echo (ER) of the base layer, that is, it does not further deduct or reduce the weight of the corresponding signal. The reason why S407 adopts differentiated processing is that the signal change that conforms to the wellside reflection attenuation curve has typical well boundary interference characteristics, and can be more actively deducted or reduced in weight; while the signal change that deviates from the wellside reflection attenuation curve is more likely to originate from the compaction anomaly of the base layer itself, and should be retained to avoid missed judgment.

[0090] After processing by S401 to S407, the detection equipment obtains the effective echo (ER) of the base layer, which serves as the basis for the formation of subsequent compaction anomalies.

[0091] S500, extract the reflection arrival stability component, effective frequency band energy attenuation component and main frequency offset component of the effective echo of the base layer in the reflection evaluation window of the base layer bottom surface, and combine the three into a compaction anomaly value.

[0092] Specifically, S500 can be further subdivided into S501 to S504: S501, extract the bottom surface reflection arrival time within the bottom surface reflection evaluation window of the base layer, and form a reflection arrival stability component based on the difference in bottom surface reflection arrival time between adjacent detection points.

[0093] The detection equipment generates a reflection that reaches the stability component CA. The detection equipment uses a reflection evaluation window on the bottom surface of the substrate. Internal extraction bottom surface reflection arrival time Where the subscript i represents the i-th detection point; the detection device takes the bottom surface reflection arrival time of the other two detection points in the same radial direction as the i-th detection point (for example, if the i-th detection point is the inner ring detection point, then take the bottom surface reflection arrival time of the middle ring detection point and the outer ring detection point in the same radial direction), and compares it with the bottom surface reflection arrival time of the i-th detection point. Together they form a ternary neighborhood; the detection device calculates the mean of the ternary neighborhood. and sample standard deviation The detection equipment calculates the reflection reaching stability component according to the following formula (6). : (6) In the formula, , , The units of measurement are all time, and the unit is seconds; It is a dimensionless and non-negative quantity, and its physical meaning is the standardization factor of the absolute value of the deviation of the arrival time of the bottom reflection of the i-th detection point from the mean of the neighborhood. The larger the value, the more significant the deviation of the base interface position of the i-th detection point from the neighborhood baseline, and the worse the corresponding reflection arrival stability. When When the value approaches zero, the detection equipment operates according to the preset minimum standard deviation. (Pick Replace 1% of the value to avoid numerical overflow.

[0094] Using formula (6) as an example: the arrival time of the bottom reflection of the inner ring detection point in a certain radial direction. for Seconds, Central Ring Road inspection point for Seconds, outer ring inspection point for Seconds. The detection equipment calculates the mean of the ternary neighborhood. seconds, sample standard deviation Seconds. Then the reflection from the inner ring detection point reaches the stability component. , is a dimensionless non-negative quantity.

[0095] S502, calculate the energy attenuation degree of the effective echo of the base layer within the effective frequency band, and form the effective frequency band energy attenuation component.

[0096] The detection equipment generates an effective frequency band energy attenuation component (CB). The detection equipment evaluates the reflection of the effective echo (ER) from the base layer at the bottom surface of the base layer via a window. The signal segment within the range is subjected to a Fast Fourier Transform to obtain the spectrum; the detection equipment operates within the effective frequency band commonly used in the impulse echo method. Integrating the square of the spectral amplitude with respect to the frequency yields the effective bandwidth energy. The detection equipment calculates the effective frequency band energy attenuation component according to formula (7). : (7) In the formula, Let i be the effective frequency band energy of the i-th detection point. The effective frequency band energy calculated and stored at the reference position described in step S103 is in the same manner, and the two have the same dimensions and units. It is a dimensionless and non-negative quantity, and its physical meaning is the normalized attenuation degree of the effective frequency band energy of the i-th detection point relative to the reference position. The larger the value, the more severe the attenuation of the effective echo energy at the i-th detection point. When the effective echo energy at the base level is higher than the reference time, The value is truncated to 0 according to formula (7); at this time, "no energy decay" is regarded as "no energy decay anomaly", which is consistent with the non-negative meaning of "degree of anomaly". An example is given using formula (7): the effective frequency band energy at the reference position. for The effective frequency band energy of the i-th detection point is in any unit. for For any unit, then , is a dimensionless non-negative quantity.

[0097] Effective frequency band lower limit and upper limit Determined as follows, see S103-A(g): Based on the thickness-frequency relationship of the impact echo method, the theoretical dominant frequency of the reflection from the bottom surface of the substrate is related to the design thickness h of the substrate and the calibrated wave velocity. Satisfying "clock frequency equals Divide by 2h, that is, the base layer design thickness h is 0.3, and the wave velocity calibration value. At a speed of 3500 meters per second, the theoretical main frequency is approximately 5800 Hz; based on this, the testing personnel set the lower limit. Set it to about half of the theoretical clock speed, and set the upper limit. Set to three to four times the theoretical main frequency, for example, for a conventional base layer with a design thickness h of 0.2 to 0.4 meters. Usually taken to , Usually taken This application addresses... , The specific value is not specifically limited; in practical applications, the testing personnel can adjust it according to the thickness of the base layer.

[0098] S503, calculate the degree of main frequency offset of the effective echo of the base layer, and form the main frequency offset component.

[0099] The detection equipment generates the dominant frequency offset component (CC). The detection equipment evaluates the effective echo (ER) of the substrate reflected from the bottom surface of the substrate via a window. The signal segment within the range is subjected to a Fast Fourier Transform to obtain the spectrum; the detection device takes the frequency position with the largest amplitude in the spectrum as the main frequency. The detection equipment calculates the main frequency offset component according to formula (8). : (8) In the formula, Let i be the dominant frequency of the i-th detection point. The main frequency is calculated and stored in the same way at the reference position described in step S103. Both are measured in the dimension of frequency and in Hertz. It is a dimensionless and non-negative quantity, and its physical meaning is the normalized absolute offset of the main frequency of the i-th detection point relative to the reference position. The larger the value, the more significant the change in the stiffness of the base medium at the i-th detection point relative to the reference position. This applies regardless of whether the dominant frequency increases (stiffness increases) or decreases (stiffness decreases). All values ​​are absolute, reflecting the degree of deviation from the reference. An example using formula (8) illustrates this: Reference position main frequency. The main frequency of the i-th detection point is 5800 Hz. If it is 4500 Hz, then , is a dimensionless non-negative quantity.

[0100] S504, after suppressing the effective frequency band energy attenuation component or the main frequency offset component that matches the wellside reflection attenuation curve, the reflection reaching stability component, the effective frequency band energy attenuation component and the main frequency offset component are combined into a compaction anomaly value.

[0101] The detection equipment suppresses the effective frequency band energy attenuation component CB or the main frequency offset component CC that matches the wellside reflection attenuation curve. The detection equipment arranges the CB (or CC) of three detection points (inner ring, middle ring, and outer ring) in the same radial direction from small to large radial distance R, obtaining a three-point broken line curve of CB (or CC) in this direction; the detection equipment matches the three-point broken line curve with the wellside reflection attenuation curve of the same circumferential angle formed by S305, and the matching method adopts Pearson correlation coefficient: when the Pearson correlation coefficient is greater than the preset correlation threshold (default 0.9, according to S103-A(i)), the detection equipment determines that the two have a high degree of consistency in shape; considering that there are only three detection points in the same radial direction in this application and the robustness of the Pearson correlation coefficient is limited, the detection equipment also needs to meet the following auxiliary judgment conditions at the same time: the three-point broken line curve is monotonically decreasing along the radial distance R, and the slope sign between any two adjacent points is consistent with the slope sign of the corresponding position of the wellside reflection attenuation curve. When the Pearson correlation coefficient is greater than the preset correlation threshold and the auxiliary judgment condition is met, the detection device will multiply CB or CC by the inhibition coefficient. The inhibition is performed before synthesis, where the inhibition coefficient is... The value range of is (0, 1). The rules for determining the value are given in S103-A(d). In practical applications, inspectors can... The threshold is set to 0.3. When the Pearson correlation coefficient is less than or equal to the preset correlation threshold, or when the auxiliary judgment condition is not met, the detection device does not suppress the correlation, and CB or CC is directly used for synthesis. Furthermore, to improve the robustness of the above matching judgment, if the site permits, the detection device can additionally deploy 1 to 2 densified detection points in the same radial direction, that is, the total number of detection points in the same radial direction is greater than three, and the Pearson correlation is compared between the densified multi-point broken line and the attenuation curve, thereby reducing the impact of the limited robustness of the correlation coefficient in the case of the three-point broken line.

[0102] The detection equipment synthesizes the compaction anomaly value CV. The detection equipment synthesizes the three components into a compaction anomaly value according to the following formula (9). : (9) In the formula, , , The composite weights of the three components are dimensionless positive numbers and satisfy the following conditions: ; , , All of them are dimensionless quantities, therefore It is also a dimensionless, non-negative quantity, and its physical meaning is the overall compaction anomaly degree at the i-th detection point. In practical applications, testing personnel can set it based on the on-site calibration results. , , The value of , , , The determination rules are detailed in S103-A(e), for example, scenarios more sensitive to reflection arrival stability can be... Set to 0.5. This application does not impose special restrictions on the synthesis method; in addition to the weighted summation method mentioned above, the maximum value among the three can also be used as the compaction anomaly value. Using formula (9) as an example: following the calculation results of formulas (6), (7), and (8), , , ;set up ,but , is a dimensionless non-negative quantity.

[0103] The reason why S501 to S504 use three components—reflection arrival stability component, effective frequency band energy attenuation component, and dominant frequency offset component—to synthesize the compaction anomaly value CV is that: reflection arrival stability reflects the disturbance at the base layer interface; effective frequency band energy attenuation reflects the enhanced absorption of stress waves by the base layer medium; and dominant frequency offset reflects the change in the stiffness of the base layer medium. These three components together constitute a multi-dimensional characterization of the compaction state, as a single component is insufficient to comprehensively characterize base layer compaction anomalies.

[0104] S600, compare the compaction anomalies of the inner ring, middle ring and outer ring detection points in the same radial direction, eliminate boundary interference results that match the wellside reflection attenuation curve, and merge continuous anomaly detection points into a suspected circumferential undercompactment zone.

[0105] Specifically, S600 can be further divided into three steps, S601 to S603. The determination rules for S601 to S603 are summarized in Table 2.

[0106] Table 2. Radial Direction Determination Rules

[0107] S601, when the compaction anomaly value of the inner ring detection point is higher than that of the middle ring detection point and the outer ring detection point, and the compaction anomaly value decreases from the inner ring detection point to the outer ring detection point and is consistent with the wellside reflection attenuation curve, the corresponding direction is marked as the suspected direction of boundary interference.

[0108] The detection equipment identifies suspected directions of boundary interference. For each radial direction, the equipment extracts the compaction anomaly value (CV) at three detection points in the order of inner ring, middle ring, and outer ring, and records them as follows: , , The detection equipment determines whether the conditions are met simultaneously. Furthermore, the attenuation patterns of the three factors are consistent with the wellside reflection attenuation curve formed by S305; when all three conditions are met, the detection equipment marks this radial direction as a suspected boundary interference direction. The specific determination method for "attenuation pattern consistent with wellside reflection attenuation curve" is as follows: the detection equipment will... radial distance , , Arrange the points to form a three-point broken line. Compare the three-point broken line with the wellside reflection attenuation curve using Pearson correlation. If the Pearson correlation coefficient is greater than the preset correlation threshold (see S103-A(i), default 0.9), and the three-point broken line is monotonically decreasing along the radial distance R, it is considered to be consistent.

[0109] S602, when the compaction anomaly value of at least two detection points in the same radial direction exceeds the anomaly determination threshold and does not conform to the wellside reflection attenuation curve, the corresponding direction is marked as a suspected undercompactment direction.

[0110] The detection equipment identifies directions suspected of being undercompacted. For each radial direction, the equipment determines whether there are at least two detection points whose compaction anomaly values ​​(CV) exceed the anomaly detection threshold. If present, further determine whether the CV distribution pattern of these detection points does not conform to the wellside reflection attenuation curve; when both conditions are met, the detection equipment marks the radial direction as a suspected undercompactment direction. Anomaly detection threshold. The calculation formula is shown in equation (10): (10) In the formula, The average compaction anomaly value CV is calculated from a set of impact echo signals at the reference location described in step S103. For the corresponding standard deviation, both are dimensionless quantities. , The statistical sample size and calculation method are described in S103-A(b); k is a positive integer, usually ranging from 2 to 3. k=2 is used for detection scenarios that are sensitive to missed detections, and k=3 is used for detection scenarios that are sensitive to false positives. For specific rules, please refer to S103-A(f). In practical applications, the testing personnel can set k to 2. Since it is a dimensionless quantity, it has the same dimension as CV and can be directly compared. An example is given using formula (10): the mean CV at the reference position. The standard deviation is 0.10. If the value is 0.05, and k is 2, then... Following the example of formula (9) Since 0.658 > 0.20, the compaction anomaly value at the inner ring detection point exceeds the anomaly judgment threshold; the detection equipment further checks along the radial direction whether the CV of the middle and outer ring detection points simultaneously exceeds the threshold. And check whether its CV distribution conforms to the wellside reflection attenuation curve, so as to decide whether to mark the radial direction as the suspected undercompaction direction or the suspected boundary interference direction.

[0111] S603, connect adjacent suspected undercompaction directions according to the circumferential angle sequence, and merge the corresponding continuous abnormal detection points into a suspected circumferential undercompaction area.

[0112] The testing equipment merges suspected areas of under-compacted circumferential areas. The testing equipment is based on the circumferential angle. The detection device iterates through all suspected undercompaction directions marked by S602 in sequence. When two or more consecutive adjacent circumferential angular directions are marked as suspected undercompaction directions, the detection device merges the consecutive adjacent circumferential angular directions and the detection points thereon into a single circumferential undercompaction suspected area. "Consecutive adjacent" refers to the circumferential angular direction being within the range of the suspected undercompaction direction. The order of the adjacent directions with a vertical tolerance of 1; the detection equipment outputs the circumferential angle range, radial distance range, and compaction anomaly value (CV) of all suspected circumferential undercompacted areas. The purpose of this merging is to avoid false alarms caused by the randomness of single-point judgment, improve the robustness of undercompacted area identification, and facilitate subsequent construction by section during pavement repair or grouting reinforcement.

[0113] refer to Figure 6 This application also provides a road base compaction non-destructive testing system SYS based on the impact echo method, which is applied to the base reinforcement area around road manholes or pipeline manholes. The system includes a parameter acquisition module M1, an echo acquisition module M2, an echo window and curve generation module M3, a boundary echo processing module M4, a compaction value formation module M5, and a suspected area output module M6.

[0114] The parameter acquisition module M1 is used to acquire the outer contour of the well body, the design thickness of the base layer, the wave velocity calibration value, and the radial distance and circumferential angle of the detection point relative to the well body. The specific implementation method of the parameter acquisition module M1 is the same as the aforementioned step S100.

[0115] The echo acquisition module M2 is used to set up detection points around the well body according to the inner ring, middle ring, and outer ring, and to acquire the impact echo signals of each detection point. The specific implementation method of the echo acquisition module M2 is the same as the aforementioned step S200.

[0116] The echo window and curve generation module M3 is used to generate a wellside reflection prediction echo window and a base layer bottom surface reflection evaluation window based on the radial distance, the base layer design thickness, and the wave velocity calibration value. It also generates a wellside reflection attenuation curve based on the reflection changes of the inner, middle, and outer ring detection points within the wellside reflection prediction echo window at the same circumferential angle. The specific implementation of the echo window and curve generation module M3 is the same as the aforementioned step S300.

[0117] The boundary echo processing module M4 is used to identify the main peak of the wellside reflection, the energy region adjacent to the main peak, and the phase abrupt change region within the wellside reflection prediction echo window, and to perform subtraction or weight reduction processing based on the wellside reflection attenuation curve to obtain the effective echo of the base layer. The specific implementation of the boundary echo processing module M4 is the same as the aforementioned step S400.

[0118] The compaction value generation module M5 is used to extract the reflection arrival stability component, effective frequency band energy attenuation component, and dominant frequency offset component of the effective echo of the base layer within the reflection evaluation window of the base layer bottom surface, and synthesize the three into a compaction anomaly value. The specific implementation method of the compaction value generation module M5 is the same as the aforementioned S500 step.

[0119] The suspected area output module M6 is used to compare the compaction anomaly values ​​of the inner, middle, and outer ring detection points in the same radial direction, eliminate boundary interference results that match the wellside reflection attenuation curve, and merge consecutive anomaly detection points into a circumferential undercompacted suspected area. The specific implementation of the suspected area output module M6 is the same as the aforementioned step S600.

[0120] The above six modules can be implemented using computer program code or an embedded controller, or they can be implemented using a single-board computer in conjunction with an impact echo detection instrument. The data flow between the modules is as follows: the parameter acquisition module M1 provides the well body outline, base layer design thickness, wave velocity calibration value, and detection point location information to the echo window and curve generation module M3; the echo acquisition module M2 provides the impact echo signal to the boundary echo processing module M4; and the echo window and curve generation module M3 provides the wellside reflection prediction echo window to the boundary echo processing module M4. Evaluation window for reflection of base surface The wellside reflection attenuation curve; the boundary echo processing module M4 provides the effective echo ER of the base layer to the compaction value forming module M5; the compaction value forming module M5 provides the compaction anomaly value CV to the suspected area output module M6, and the suspected area output module M6 outputs the circumferential undercompacted suspected area results.

[0121] The various embodiments of this application can be combined arbitrarily to achieve different technical effects. Those skilled in the art, after reading this application, can make non-creative improvements to the methods and systems of this application, such as adjusting the number of detection points or adjusting the expansion width. and Modifications such as changing the fitting method of the wellside reflection attenuation curve and changing the synthesis method of the compaction anomaly value CV should all be included within the scope of protection of this application. The above descriptions are merely embodiments of the technical solution of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, or improvements made based on the disclosure of this application should be included within the scope of protection of this application.

Claims

1. A non-destructive testing method for road base compaction degree based on impact echo method, characterized in that, The method, applied to the base reinforcement area surrounding road inspection wells or pipeline wells, includes: Obtain the outer contour of the well body, the design thickness of the base layer, the wave velocity calibration value, and the radial distance and circumferential angle of the detection point relative to the well body; Detection points were set up around the well body in the form of inner ring, middle ring and outer ring, and the impact echo signals of each detection point were collected; Based on the radial distance, the base layer design thickness, and the wave velocity calibration value, a wellside reflection prediction echo window and a base layer bottom surface reflection evaluation window are generated. Based on the reflection changes of the inner ring, middle ring, and outer ring detection points at the same circumferential angle within the wellside reflection prediction echo window, a wellside reflection attenuation curve is formed. Within the wellside reflection prediction echo window, the main peak of the wellside reflection, the energy region adjacent to the main peak, and the phase change region are identified, and subtraction or weighting is performed based on the wellside reflection attenuation curve to obtain the effective echo of the base layer. The reflection arrival stability component, effective frequency band energy attenuation component, and main frequency offset component of the effective echo of the base layer are extracted in the reflection evaluation window of the base layer bottom surface, and the three are combined into a compaction anomaly value. The compaction anomalies at the inner, middle, and outer ring detection points in the same radial direction are compared. Boundary interference results that match the wellside reflection attenuation curve are excluded, and continuous anomaly detection points are merged into a suspected circumferential undercompactment zone.

2. The method according to claim 1, characterized in that, The acquisition of the well body's external contour, base layer design thickness, wave velocity calibration value, and the radial distance and circumferential angle of the detection point relative to the well body includes: The outer contour of the manhole body is determined based on the outer edge of the manhole ring, the outer edge of the manhole wall, or the outer edge of the pipeline manhole. The design thickness of the base layer is determined based on the base layer construction design documents or on-site thickness measurement results. Impact echo signals were collected at a base layer location that was far from the well body and where the compaction state had been confirmed, and wave velocity calibration values ​​were obtained based on the arrival time of the reflection from the bottom surface of the base layer. Using the geometric center of the well body's outer contour or the projection point of the pipeline well axis as an angular reference, the radial distance and circumferential angle of the detection point are determined.

3. The method according to claim 1, characterized in that, The generated wellside reflection prediction echo window and the base course bottom surface reflection evaluation window include: The arrival time interval of wellside reflection is determined based on the radial distance of the detection point and the wave velocity calibration value, and the arrival time interval of wellside reflection is extended into a wellside reflection prediction echo window. The arrival time interval of reflection from the bottom surface of the base layer is determined based on the base layer design thickness and the wave velocity calibration value, and the arrival time interval of reflection from the bottom surface of the base layer is expanded into a base layer bottom surface reflection evaluation window; When the wellside reflection prediction echo window overlaps with the base bottom surface reflection evaluation window, the overlapping part is marked as a boundary interference candidate area.

4. The method according to claim 1, characterized in that, The step of forming a wellside reflection attenuation curve based on the reflection changes of the inner, middle, and outer ring detection points at the same circumferential angle within the wellside reflection prediction echo window includes: Extract the reflection peak value, energy area, or phase change amplitude of the inner ring, middle ring, and outer ring detection points at the same circumferential angle within the wellside reflection prediction echo window; The reflection peak value, the energy area, or the phase change amplitude are sorted according to the radial distance of the detection points; The relationship between the attenuation of reflection and the increase of radial distance is determined as the wellside reflection attenuation curve corresponding to the circumferential angle; one of the three characteristics, namely the reflection peak value, energy area and phase change amplitude, is selected as the unique index of the wellside reflection attenuation curve for the same circumferential angle.

5. The method according to claim 1, characterized in that, The identification of the wellside reflection main peak, the energy region adjacent to the main peak, and the phase abrupt change region within the wellside reflection prediction echo window includes: Within the wellside reflection prediction echo window, the position of the peak value with prominent amplitude is determined based on the local background amplitude, and the peak position is taken as the main peak of the wellside reflection. Centered on the main peak of the well-side reflection, a sampling interval with continuously higher energy than the local background energy is searched forward and backward, and the sampling interval is taken as the energy region adjacent to the main peak; Phase continuity analysis is performed on the signal within the wellside reflection prediction echo window, and the sampling interval with a sudden increase in phase change rate and adjacent to the wellside reflection main peak or the energy region adjacent to the main peak is regarded as the phase abrupt change region.

6. The method according to claim 5, characterized in that, The process of subtracting or downweighting based on the wellside reflection attenuation curve to obtain the effective echo at the base layer includes: The sampling segment containing the main peak of the wellside reflection is subjected to amplitude subtraction, interpolation replacement, or evaluation rejection. The selection rules for amplitude subtraction, interpolation replacement, or evaluation rejection are as follows: when the proportion of overlapping sampling points between the sampling segment containing the main peak of the wellside reflection and the evaluation window of the bottom surface of the base layer is greater than a preset overlap threshold, evaluation rejection is used; when the width of the sampling segment containing the main peak of the wellside reflection is less than a preset width threshold, interpolation replacement is used; otherwise, amplitude subtraction is used. An attenuation weight is set for the energy region adjacent to the main peak according to its distance from the well-side reflected main peak and its energy intensity; The attenuation weights for the phase change regions are set according to the phase change rate; When the corresponding signal change at the detection point in the middle or outer ring conforms to the wellside reflection attenuation curve, the deduction amount is increased or the evaluation weight is reduced. When the corresponding signal change deviates from the wellside reflection attenuation curve, it is retained as an evaluation of the effective echo of the base layer.

7. The method according to claim 1, characterized in that, The reflection arrival stability component, effective frequency band energy attenuation component, and dominant frequency offset component of the effective echo of the base layer are extracted within the reflection evaluation window of the base layer bottom surface. These three components are then combined into a compaction anomaly value, including: The arrival time of bottom surface reflection is extracted within the bottom surface reflection evaluation window of the base layer, and a reflection arrival stability component is formed based on the difference in the arrival time of bottom surface reflection at adjacent detection points. Calculate the energy attenuation degree of the effective echo from the base layer within the effective frequency band to form the effective frequency band energy attenuation component; Calculate the degree of dominant frequency offset of the effective echo from the base layer to form a dominant frequency offset component; After suppressing the effective frequency band energy attenuation component or the dominant frequency offset component that matches the wellside reflection attenuation curve, the reflection arrival stability component, the effective frequency band energy attenuation component, and the dominant frequency offset component are combined into a compaction anomaly value. The compaction anomaly value is used to indicate the suspicion of under-compaction of the base course and can be used for compaction quality evaluation when combined with on-site calibration. The reflection arrival stability component, the effective frequency band energy attenuation component, and the dominant frequency offset component are all defined according to the absolute deviation.

8. The method according to claim 1, characterized in that, The arrangement of detection points around the well body in the form of inner ring, middle ring, and outer ring includes: The inner ring detection points are placed in the base reinforcement edge area close to the outer contour of the well body; the middle ring detection points are placed in the middle of the base reinforcement area; and the outer ring detection points are placed in the base transition area away from the well body. The inner ring detection point, the middle ring detection point, and the outer ring detection point at the same circumferential angle are arranged sequentially along the local normal direction of the well body outline.

9. The method according to claim 1, characterized in that, The process of comparing the compaction anomaly values ​​of the inner, middle, and outer ring detection points in the same radial direction, excluding boundary interference results that match the wellside reflection attenuation curve, and merging consecutive anomaly detection points into a suspected circumferential undercompactment zone includes: When the compaction anomaly value at the inner ring detection point is higher than that at the middle ring and outer ring detection points, and the compaction anomaly value decreases from the inner ring detection point to the outer ring detection point and is consistent with the wellside reflection attenuation curve, the corresponding direction is marked as the suspected direction of boundary interference. The consistency means that the Pearson correlation coefficient between the three-point broken line of the compaction anomaly value and the wellside reflection attenuation curve is greater than a preset correlation threshold, and the three-point broken line decreases monotonically along the radial distance. When the compaction anomaly values ​​at at least two detection points in the same radial direction exceed the anomaly determination threshold and do not conform to the wellside reflection attenuation curve, the corresponding direction is marked as a suspected undercompacted direction. The anomaly determination threshold is calculated by the mean μ and standard deviation σ of the compaction anomaly values ​​at the reference location. The method is determined by, where k is a positive integer not less than 2; Connect adjacent suspected undercompaction directions according to the circumferential angle sequence, and merge the corresponding continuous abnormal detection points into a circumferential undercompaction suspected area. The continuous abnormal detection points refer to the detection points that are marked as suspected undercompaction directions in two or more consecutive adjacent circumferential angle directions.

10. A non-destructive testing system for road base compaction based on the impact-echo method, characterized in that, The system, applied to the base reinforcement area around road inspection wells or pipeline wells, includes: The parameter acquisition module is used to acquire the outer contour of the well body, the design thickness of the base layer, the wave velocity calibration value, and the radial distance and circumferential angle of the detection point relative to the well body; The echo acquisition module is used to set up detection points around the well body in the form of inner ring, middle ring and outer ring, and to acquire the impact echo signal of each detection point; The echo window and curve generation module is used to generate a wellside reflection prediction echo window and a base layer bottom surface reflection evaluation window based on the radial distance, the base layer design thickness and the wave velocity calibration value, and to form a wellside reflection attenuation curve based on the reflection changes of the inner ring, middle ring and outer ring detection points at the same circumferential angle within the wellside reflection prediction echo window. The boundary echo processing module is used to identify the main peak of the wellside reflection, the energy region adjacent to the main peak, and the phase change region within the wellside reflection prediction echo window, and to perform subtraction or weight reduction processing based on the wellside reflection attenuation curve to obtain the effective echo of the base layer. The compaction value generation module is used to extract the reflection arrival stability component, effective frequency band energy attenuation component, and main frequency offset component of the effective echo of the base layer within the reflection evaluation window of the base layer bottom surface, and combine the three into a compaction anomaly value; The suspected area output module is used to compare the compaction anomaly values ​​of the inner ring, middle ring and outer ring detection points in the same radial direction, exclude boundary interference results that match the wellside reflection attenuation curve, and merge continuous anomaly detection points into a circumferential undercompactment suspected area.

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