System and method for detecting road surface structure strength

Abstract

The application provides a system and method for detecting road surface structure strength, which realizes non-contact measurement of road surface strength through a microwave radar component, effectively avoids time delay caused by beam falling and beam lifting in traditional tests, improves test efficiency, and also realizes real-time monitoring through road test points, improves monitoring precision, is convenient and intuitive, and effectively reflects the change rule of the strength of each structure layer of the road according to the actual elastic modulus of each layer structure of the road calculated according to the instantaneous vibration frequency value of the multiple road test points.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pavement detection, and particularly relates to a system and method for detecting pavement structure strength. BACKGROUND

[0002] At present, the focus of domestic highway construction will develop from "construction and maintenance simultaneously" to "maintenance-oriented", therefore, it is necessary to accurately evaluate the performance of the pavement, which has important value for pavement maintenance and repair. Deflection is one of the important parameters for representing the overall strength of highway pavement, therefore, a falling weight deflectometer (FWD) is developed for testing the important parameter deflection of the overall strength of highway pavement.

[0003] However, the traditional falling weight deflectometer uses a displacement sensor (LVDT) to test the deflection value (Dr), but the installation of the displacement sensor (LVDT) is complicated, the test efficiency is low, only the dynamic displacement value can be output, the detection accuracy is low, and the pavement structure strength index PSSI is used to calculate the highway strength, the calculation method does not fully exert the advantage of the deflection basin in evaluating the pavement bearing capacity, and cannot effectively reflect the change rule of the strength of each structure layer of the highway. SUMMARY

[0004] In view of the problems in the background art, the purpose of the present application is to provide a system and method for detecting pavement structure strength, which improves the detection efficiency, realizes real-time monitoring of the pavement test points, has high dynamic monitoring accuracy, and effectively reflects the change rule of the strength of each structure layer of the highway.

[0005] In order to achieve the above purpose, the present application provides a system for detecting pavement structure strength, comprising: a highway impact component, a microwave radar component and a terminal component, the microwave radar component is connected with the terminal component;

[0006] The microwave radar component is used for transmitting microwave signals to a plurality of highway test points of the impacted highway and receiving echo signals reflected by the plurality of highway test points;

[0007] The terminal component comprises a data acquisition module for acquiring, storing and preprocessing the received echo signals and calculating the instantaneous vibration frequency values of the plurality of highway test points;

[0008] and a data processing module for calculating the actual elastic modulus of each layer structure of the highway according to the instantaneous vibration frequency values of the plurality of highway test points, comparing the actual elastic modulus with a preset elastic modulus, and judging whether the strength of the highway pavement is qualified according to the comparison result.

[0009] Optionally, the plurality of microwave radar units is at least four, and the at least four microwave radar units are respectively a first microwave radar unit, a second microwave radar unit, a third microwave radar unit and a fourth microwave radar unit on a same straight line, wherein the first microwave radar unit is arranged close to a center region of the impact road assembly.

[0010] The first microwave radar unit and the second microwave radar unit are spaced apart by a distance ranging from 10 cm to 30 cm, the first microwave radar unit and the third microwave radar unit are spaced apart by a distance ranging from 50 cm to 70 cm, and the first microwave radar unit and the fourth microwave radar unit are spaced apart by a distance ranging from 100 cm to 140 cm.

[0011] Optionally, the first microwave radar unit and the second microwave radar unit are spaced apart by a distance of 20 cm, the first microwave radar unit and the third microwave radar unit are spaced apart by a distance of 60 cm, and the first microwave radar unit and the fourth microwave radar unit are spaced apart by a distance of 120 cm.

[0012] Optionally, the impact road assembly comprises a heavy hammer, a connecting rod and a bearing member.

[0013] The bearing member is arranged on the road, the connecting rod is arranged on the bearing member, the heavy hammer is movably arranged on the connecting rod, and the heavy hammer is located above the bearing member, so that the heavy hammer can freely fall on the bearing member through the connecting rod.

[0014] The application also provides a method for detecting the strength of a road surface structure, the method comprising:

[0015] Impacting a road;

[0016] A plurality of road detection points leading to the impacted road emit microwave signals and receive echo signals reflected by the plurality of road detection points;

[0017] The received echo signals are collected, stored and preprocessed, and the instantaneous vibration frequency values of the plurality of road detection points are calculated;

[0018] According to the instantaneous vibration frequency values of the plurality of road detection points, the actual elastic modulus of each layer structure of the road is calculated;

[0019] According to the comparison between the actual elastic modulus and the preset elastic modulus, it is determined whether the strength of the road surface is qualified according to the comparison result.

[0020] Optionally, the terminal assembly calculates the instantaneous vibration frequency values of the plurality of road detection points according to the received echo signals, comprising:

[0021] Finding all extreme points in the highway surface micro-motion time domain signal, and calculating the intermediate time domain signal value;

[0022] Determining whether the intermediate time domain signal value meets a preset condition to determine whether the intermediate time domain signal value is an inherent modal value;

[0023] If the preset condition is not met, the intermediate time domain signal value replaces the time domain signal value, and the above steps are re-executed until the preset condition is met, and the intermediate time domain signal value is a target inherent modal value;

[0024] According to the difference between the time domain signal value and the target inherent modal value, a time domain residual signal is obtained, and the above steps are repeated until no new target inherent modal value can be screened out, and k target inherent modal values are obtained, wherein k is greater than or equal to 1;

[0025] According to the k target inherent modal values, a target time domain signal value is calculated;

[0026] According to the target time domain signal value, the instantaneous vibration frequency value is calculated.

[0027] Optionally, the determination of whether the intermediate time domain signal value meets a preset condition comprises:

[0028] In the entire data sequence time domain signal value, the number of extreme points is equal to the number of zero-crossing points, or the number of extreme points and the number of zero-crossing points differ by no more than one;

[0029] At any time point, the envelope mean value defined by the local maximum value and the local minimum value of the time domain signal value is zero.

[0030] Optionally, the calculation of the instantaneous vibration frequency value according to the target time domain signal value comprises:

[0031] Transforming the target time domain signal value to obtain an analytical signal value;

[0032] According to the analytical signal value, the instantaneous vibration frequency value is calculated.

[0033] Optionally, the calculation of the actual elastic modulus of the highway layer structure according to the instantaneous vibration frequency values of the plurality of highway detection points comprises:

[0034] According to the difference between the instantaneous vibration frequency values of the plurality of highway detection points, the bearing parameter values of the surface layer, the base layer, the bottom base layer and the roadbed are obtained;

[0035] According to the bearing parameter values of the surface layer, the base layer, the bottom base layer and the roadbed, the actual elastic modulus is calculated.

[0036] Optionally, the judging whether the strength of the highway pavement is qualified according to the comparison result of the actual elastic modulus and the preset elastic modulus comprises:

[0037] If the ratio between the actual elastic modulus and the preset elastic modulus is greater than 1, it is concluded that the strength of the highway pavement is qualified.

[0038] The beneficial effects of the present application are as follows:

[0039] The non-contact measurement of the pavement strength is realized by the microwave radar assembly, the time delay caused by the beam falling and lifting in the traditional test is effectively avoided, the test efficiency is improved, and the real-time monitoring is realized through the pavement test points, the monitoring accuracy is improved, it is convenient and intuitive, and the actual elastic modulus of each layer structure of the highway calculated according to the instantaneous vibration frequency values of the plurality of highway detection points effectively reflects the change rule of the strength of each structure layer of the highway. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a system structure schematic diagram of the present application for detecting the strength of the pavement structure.

[0041] Figure 2 is a specific structure schematic diagram of the system for detecting the strength of the pavement structure of the present application.

[0042] Figure 3 is a method flow schematic diagram of the present application for detecting the strength of the pavement structure.

[0043] Figure 4 is a specific detection structure schematic diagram of each layer of the pavement of the system for detecting the strength of the pavement structure of the present application.

[0044] Among them, the sign explanation is as follows:

[0045] Impact highway assembly 100, heavy hammer 110, connecting rod 120, bearing 130;

[0046] Microwave radar assembly 200, first microwave radar unit 210, second microwave radar unit 220, third microwave radar unit 230, fourth microwave radar unit 240, fixing frame 250;

[0047] Terminal assembly 300, data acquisition module 310, data processing module 320. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all the embodiments.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application; the use herein of terms such as "comprise" and "comprising", "have" and "having", "include" and "including" and any variations thereof are to be construed as referring to compositions and methods comprising, consisting of, consisting essentially of, or consisting of, as appropriate, in accordance with the principles of the application.

[0050] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase "in an embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another.

[0051] A system for detecting road surface structure strength according to the present application will be described in detail below with reference to the accompanying drawings.

[0052] With reference to Figure 1 and Figure 4 , the impact road assembly 100, the microwave radar assembly 200 and the terminal assembly 300, the microwave radar assembly 200 is connected with the terminal assembly 300, the microwave radar assembly 200 is used for transmitting microwave signals to a plurality of road detection points of the impacted road and receiving echo signals reflected by the plurality of road detection points, the terminal assembly 300 includes a data acquisition module 310 for acquiring, storing and preprocessing the received echo signals and calculating instantaneous vibration frequency values of the plurality of road detection points, and a data processing module 320 for calculating actual elastic moduli of road layer structures according to the instantaneous vibration frequency values of the plurality of road detection points, comparing the actual elastic moduli with preset elastic moduli, and judging whether the strength of the road surface is qualified according to the comparison result. The microwave radar assembly 200 realizes non-contact measurement of the road surface strength, effectively avoids time delay caused by beam falling and beam lifting in traditional testing, improves testing efficiency, and also realizes real-time monitoring through road test points, improves monitoring accuracy, is convenient and intuitive, and the actual elastic moduli of the road layer structures calculated according to the instantaneous vibration frequency values of the plurality of road detection points effectively reflect the change rule of the strength of the road layer structures.

[0053] Optionally, the microwave radar assembly 200 comprises a plurality of microwave radar units for detecting different positions of the road strength, the plurality of microwave radar units are connected with the terminal assembly 300, and the plurality of microwave radar units are spaced apart at different distances, and the distances between the plurality of microwave radar units gradually increase. By the plurality of microwave radar units, a plurality of different detection points of the impact road surface are formed to obtain data between different points. The data is transmitted to the terminal assembly 300, so as to calculate and process more complete road strength parameters, which is beneficial to analyze the strength of the road, and the distances between the plurality of microwave radar units gradually increase, so that the dynamic monitoring precision is higher, and the change rule of the strength of each structure layer of the road is effectively reflected.

[0054] Optionally, the plurality of microwave radar units are four, and the four microwave radar units are respectively a first microwave radar unit 210, a second microwave radar unit 220, a third microwave radar unit 230 and a fourth microwave radar unit 240 on the same straight line. The first microwave radar unit 210 is arranged close to the impact road center area of the impact road assembly 100. Optionally, more than four microwave radar units can be arranged according to the actual situation, and the data detected by the more than four microwave radar units is transmitted to the terminal assembly 300, so as to obtain more comprehensive and more accurate road strength parameters calculated, analyzed and processed by the terminal assembly 300. However, more than four microwave radar units will increase the cost, and less than four microwave radar units can also detect the road, but the precision is far less than that of four microwave radar units, therefore, four microwave radar units are the most suitable.

[0055] It should be noted that when the impact road assembly 100 falls on the road surface, the impact load with a certain energy is generated, so that the plurality of microwave radar units for detecting different positions of the road strength and the asphalt concrete road surface near the plurality of microwave radar units vibrate at a certain frequency. The plurality of microwave radar units receive the echo signal of the road surface at different detection points, that is, the related information of the vibration of the asphalt concrete road surface at a frequency, and transmit the information to the terminal assembly 300. Through the calculation and processing of the terminal assembly 300, the structural strength of different layers of the road is obtained according to the data information of different points, and the change rule of the strength of each structure layer of the road is effectively reflected.

[0056] In an embodiment, the first microwave radar unit 210 and the second microwave radar unit 220 are spaced apart by a distance ranging from 10 cm to 30 cm, the first microwave radar unit 210 and the third microwave radar unit 230 are spaced apart by a distance ranging from 50 cm to 70 cm, and the first microwave radar unit 210 and the fourth microwave radar unit 240 are spaced apart by a distance ranging from 100 cm to 140 cm. Alternatively, the first microwave radar unit 210 and the second microwave radar unit 220 are spaced apart by a distance of 20 cm, the first microwave radar unit 210 and the third microwave radar unit 230 are spaced apart by a distance of 60 cm, and the first microwave radar unit 210 and the fourth microwave radar unit 240 are spaced apart by a distance of 120 cm. By detecting the positions of the different microwave radar units, different data can be measured. Of course, the most suitable distances between the microwave radar units can effectively improve the accuracy of detecting the strength of the road surface. In this embodiment, the first microwave radar unit 210 is taken as the reference distance, and the distances between the first microwave radar unit 210 and the second microwave radar unit 220, the first microwave radar unit 210 and the third microwave radar unit 230, and the first microwave radar unit 210 and the fourth microwave radar unit 240 are 20 cm, 60 cm, and 120 cm, respectively. Of course, other distances can also be used, but the strength of the road surface detected by the distances between the microwave radar units is more accurate.

[0057] Alternatively, the microwave radar assembly 200 further comprises a fixed frame 250 which is suspended, and the plurality of microwave radar units are arranged on the fixed frame 250 so that the plurality of microwave radar units are suspended over the road. By being suspended, the plurality of microwave radar units are not in contact with the road surface, thereby avoiding the delay in detection time caused by lifting and lowering the beam in the conventional test, and improving the detection accuracy. Alternatively, the fixed frame 250 is arranged on a carrying vehicle, and the carrying vehicle facilitates the transportation of the system for detecting the strength of the road surface structure at any time. The fixed frame 250 can be a beam frame.

[0058] Please refer to Figure 2 In an embodiment, each of the plurality of microwave radar units comprises a transmitter for transmitting a signal to a detection position of the road, a receiver for receiving a reflected signal of the detection position of the road, and a signal processor for converting the reflected signal into a micro-displacement time history signal of the road surface. The signal processor is connected to the terminal assembly 300. Alternatively, the signal processor converts the reflected signal into a micro-displacement time domain signal. Specifically, each of the plurality of microwave radar units comprises a transmitting antenna and a receiving antenna. The transmitter transmits the signal to the transmitting antenna, and then the signal is transmitted to the detection position of the road surface through the transmitting antenna. At this time, the detection position of the road surface transmits a reflected signal to the receiving antenna, and then the receiving antenna transmits the reflected signal to the receiver. In addition, the transmitter can also transmit relevant information to the receiver.

[0059] Alternatively, the data acquisition module 310 and the data processing module 320 calculate whether the strength of the road surface is qualified through the following specific process:

[0060] A1, add N times of Gaussian white noise signal z i (t) to the whole time-domain signal x(t)

[0061] x i (t) = x(t) + z i (t), i = 1 ~ N; x i (t) is a time-domain signal function with noise.

[0062] A2, find all extreme points of time-domain signal x i (t)

[0063] A3, fit the envelope line E imax (t) of the upper and lower extreme points with a cubic spline curve imin (t), and calculate the mean value m i (t) = [E imax (t) + E imin (t)] / 2, and subtract it from x(t): h i (t) = x(t) + m i (t), h i (t) can be represented as an intermediate time-domain function;

[0064] A4, determine whether h i (t) satisfies the preset data to determine whether h i (t) is an intrinsic modal value (IMF);

[0065] A5, if not, replace x i (t) with h i (t), repeat steps A2-A4 until h i (t) satisfies the preset data, then this h i (t) is the intrinsic modal value (IMF) to be extracted, denoted as h i1 (t);

[0066] A6, let the residual signal c i1 (t) = x i (t) - h i1 (t), repeat steps A2-A5 until the last residual signal c ik (t) is only a monotonic value or a constant value, i.e. no more IMF components can be screened out, then x i (t) can be decomposed into k intrinsic modal values (IMF), denoted as h ij (t), j = 1 ~ k; then the time-domain signal x i (t) is mathematically expressed as:

[0067]

[0068] x i (t) represents a time domain function mean value;

[0069] A7, is according to the following formula:

[0070]

[0071] Solving IMF j , j = 1 ~ k, then

[0072] At this time, x(t) represents a real signal time domain function;

[0073] A8, x(t) is a real signal, and x(t) is transformed into y(t) by using Hilbert:

[0074]

[0075] Then x(t) and y(t) constitute an analytic signal b(t) = x(t) + y(t)j = a(t)e θ(t)j , wherein:

[0076] Then the instantaneous frequency can be obtained:

[0077]

[0078] Specifically, whether the step A4 satisfies the preset data includes:

[0079] In the entire data sequence x(t), the number of extreme points is equal to the number of zero-crossing points, or at most, the difference cannot be more than one;

[0080] At any time point, the envelope mean value defined by the local maximum and local minimum of the signal is zero.

[0081] Further, the following steps are further included:

[0082] B1, the FWD frequency basin index is used as the road structure bearing capacity condition evaluation index, that is, the frequency basin parameter:

[0083] Δf1 = f0-f 20 , Δf2 = f 20 -f 60 , Δf3 = f 60 -f 120 , Δf4 = f 120 -0, respectively, as the bearing capacity condition influence parameters of the surface layer, the base layer, the bottom base layer and the roadbed, wherein f0, f 20 , f 60 , f 120This refers to the frequency value at the measurement point. Specifically, it represents the frequency difference between the measurement points of each radar detection unit.

[0084] The frequency basin parameter Δf was determined based on asphalt pavement testing. i With the modulus E of each structural layer i Correlation analysis was performed, and the relationship between the frequency basin parameters and the modulus of each layer was established: Where parameter a i β i It was obtained through data regression fitting.

[0085] B2. Based on the theoretical elastic modulus E of each structural layer of asphalt pavement, establish evaluation indicators:

[0086]

[0087] If the measured CPI ≥ 1, it indicates that the strength of each structural layer of the asphalt concrete pavement meets the design requirements; otherwise, it does not. Using a frequency basin test at pavement measurement points to assess pavement structural strength fully leverages the advantages of the deflection basin test for evaluating pavement bearing capacity, while effectively reflecting the variation patterns of the strength of each structural layer of the highway.

[0088] In one implementation, the impact road component 100 includes a hammer 110, a connecting rod 120, and a carrier 130. The carrier 130 is mounted on the road, the connecting rod 120 is mounted on the carrier 130, and the hammer 110 is movably mounted on the connecting rod 120. The hammer 110 is positioned above the carrier 130 so that it can freely fall from the connecting rod 120 onto the carrier 130. By freely falling at an adjustable height onto the carrier 130, an impact load of a certain energy is generated. This load then acts on the asphalt pavement detection points, causing the asphalt concrete pavement at and around the detection points to vibrate at a certain frequency. The microwave radar unit then transmits the received pavement frequency vibration data from each detection point to the terminal component 300, ultimately obtaining the desired parameters.

[0089] Please see Figure 3 This application also provides a method for detecting the strength of pavement structures, the method comprising:

[0090] Step S10: Impact the highway;

[0091] Step S20: Transmit microwave signals to multiple road detection points that have been impacted by the road and receive echo signals reflected by the multiple road detection points.

[0092] Step S30: The received echo signal is acquired, stored, and preprocessed to calculate the instantaneous vibration frequency values ​​of multiple highway detection points. All extreme points are found in the road surface micro-motion time-domain signal, and the intermediate time-domain signal values ​​are calculated.

[0093] determining whether the intermediate time domain signal value satisfies a preset condition to determine whether the intermediate time domain signal value is an inherent modal value;

[0094] If the preset condition is not satisfied, the intermediate time domain signal value replaces the time domain signal value, and the above steps are re-executed until the preset condition is satisfied, and the intermediate time domain signal value is a target inherent modal value;

[0095] A time domain residual signal is obtained according to the difference between the time domain signal value and the target inherent modal value, and the above steps are repeated until a new target inherent modal value cannot be screened out, to obtain k target inherent modal values, wherein k is greater than or equal to 1;

[0096] A target time domain signal value is calculated according to the k target inherent modal values;

[0097] The instantaneous vibration frequency value is calculated according to the target time domain signal value.

[0098] The specific calculation process of step S30 is as follows:

[0099] S31, add a Gaussian white noise signal z i (t) N times in the entire time domain signal x(t):

[0100] x i (t) = x(t) + z i (t), i = 1 ~ N, x i (t) represents a time domain function with noise;

[0101] S32, find all extreme points of the time domain signal x i (t);

[0102] S33, use a cubic spline curve to fit the envelope lines E imax (t) and E imin (t) of the upper and lower extreme points, and calculate the mean value m i (t) = [E imax (t) + E imin (t)] / 2, and subtract it from x(t): h i (t) = X(t) + m i (t), h i (t) can be represented as an intermediate time domain function;

[0103] S34, determine whether h i (t) satisfies a preset condition to determine whether h i (t) is an inherent modal value IMF;

[0104] S35, if not, replace hi (t) instead of x i (t), repeat A2-A4 steps until h i (t) meets preset criterion, then this h i (t) is the intrinsic modal value (IMF) to be extracted, denoted as h i1 (t);

[0105] S36, let the residual signal c i1 (t) = x i (t) - h i1 (t), repeat S31-S35 steps until the last residual signal c ik (t) is only a monotonic value or a constant value, i.e. no more IMF components can be screened out, then x i (t) can be decomposed into k intrinsic modal values (IMF), denoted as h ij (t), j = 1 ~ k; then the time-domain signal x i (t) is mathematically expressed as:

[0106] S37, according to the following formula:

[0107]

[0108] Solve IMF j , j = 1 ~ k,

[0109]

[0110] x(t) represents a real signal time-domain function;

[0111] S38, x(t) is a real signal, and x(t) is transformed into y(t) by using Hilbert:

[0112]

[0113] Then x(t) and y(t) constitute an analytic signal b(t) = x(t) + y(t)j = a(t)e θ(t)j , wherein:

[0114] Then the instantaneous vibration frequency value

[0115] Optionally, whether the step S34 meets the preset data includes:

[0116] In the entire data sequence x(t), the number of extreme points is equal to the number of zero-crossing points, or at most, the difference cannot be more than one;

[0117] ​At any time point, the local maximum and minimum of the signal define an envelope mean of zero. The present application uses microwave radar to measure the vibration frequency of the asphalt concrete pavement, which is a non-contact measurement method, effectively avoiding the time delay caused by beam falling and beam lifting in traditional testing, improving the testing efficiency; secondly, the asphalt pavement test point can be monitored in real time, and the dynamic monitoring accuracy is high, which is convenient and intuitive.

[0118] Step S40, according to the instantaneous vibration frequency value of the plurality of highway detection points, the actual elastic modulus of the highway layer structure is calculated.

[0119] Step S40 specific calculation process:

[0120] The FWD frequency basin index is used as the evaluation index of the bearing capacity of the pavement structure, that is, the frequency basin parameter:

[0121] Δf1=f0-f 20 , Δf2=f 20 -f 60 , Δf3=f 60 -f 120 , Δf4=f 120 -0, respectively as the influence parameter of the bearing capacity of the surface layer, the base layer, the bottom base layer and the roadbed, wherein f0, f 20 , f 60 , f 120 are the frequency values of the detection points. That is, the frequency difference of the detection points between each radar detection unit.

[0122] Step S50, according to the comparison of the actual elastic modulus and the preset elastic modulus, whether the strength of the highway pavement is qualified is judged according to the comparison result.

[0123] Step S50 specific calculation process:

[0124] According to the frequency basin parameter Δf i and the correlation analysis of each structure layer modulus E i , and establish the relationship between the frequency basin parameter and each layer modulus: Wherein the parameters a i , β i are obtained by data regression fitting.

[0125] Step S60, according to the relationship formula established between the plurality of instantaneous vibration frequency values and the elastic modulus of the highway layer structure, the strength parameter of the highway pavement is obtained according to the relationship formula.

[0126] Step S60 specific calculation process:

[0127] Combined with the theoretical elastic modulus E 理 of each structure layer of the asphalt pavement, the evaluation index is established:

[0128]

[0129] As measured CPI ≥ 1, indicating that the strength of each structural layer of asphalt concrete pavement meets the design requirements, otherwise does not meet the design requirements. The frequency basin of pavement measuring points is used to evaluate the strength of pavement structure, which fully plays the advantage of bending basin in evaluating the bearing capacity of pavement, and effectively reflects the change law of the strength of each structural layer of highway.

Claims

1. A system for detecting the strength of a pavement structure, characterized by The system comprises: an impact road assembly (100), a microwave radar assembly (200), and a terminal assembly (300), wherein the microwave radar assembly (200) is connected with the terminal assembly (300); the microwave radar assembly (200) is configured to emit microwave signals to a plurality of road detection points of the impacted road and receive echo signals reflected by the plurality of road detection points; the terminal assembly (300) comprises a data acquisition module (310) configured to acquire, store, and pre-process the received echo signals and calculate instantaneous vibration frequency values of the plurality of road detection points; and a data processing module (320) for calculating actual elastic modulus of each layer structure of the road according to the instantaneous vibration frequency values of the multiple road detection points, comparing the actual elastic modulus with preset elastic modulus, and judging whether the strength of the road surface is qualified according to the comparison result;E i =a i (Δf i ) βi , i=1~4, wherein Δf i is a frequency basin parameter, E i is the modulus of each layer, and parameters a i and β i are obtained through data regression fitting; the plurality of microwave radar units are at least four, and the at least four microwave radar units are respectively a first microwave radar unit (210), a second microwave radar unit (220), a third microwave radar unit (230), and a fourth microwave radar unit (240) on the same straight line, wherein the first microwave radar unit (210) is arranged close to a central area of the impacted road of the impact road assembly (100); the terminal assembly (300) calculates the instantaneous vibration frequency values of the plurality of road detection points according to the received echo signals, comprising: finding all extreme points in a road surface micro-motion time domain signal value to calculate an intermediate time domain signal value; judging whether the intermediate time domain signal value meets a preset condition to determine whether the intermediate time domain signal value is an inherent modal value; if the preset condition is not met, the intermediate time domain signal value replaces the time domain signal value, and the above steps are re-executed until the preset condition is met, and the intermediate time domain signal value is a target inherent modal value; a time domain residual signal is obtained according to a difference between the time domain signal value and the target inherent modal value, and the above steps are repeated until a new target inherent modal value cannot be screened out, and k target inherent modal values are obtained, wherein k is greater than or equal to 1; a target time domain signal value is calculated according to the k target inherent modal values; the instantaneous vibration frequency value is calculated according to the target time domain signal value.

2. The system for detecting road surface structure strength according to claim 1, wherein: a distance between the first microwave radar unit (210) and the second microwave radar unit (220) is in a range of 10 cm to 30 cm, a distance between the first microwave radar unit (210) and the third microwave radar unit (230) is in a range of 50 cm to 70 cm, and a distance between the first microwave radar unit (210) and the fourth microwave radar unit (240) is in a range of 100 cm to 140 cm.

3. The system for detecting the strength of a pavement structure according to claim 2, wherein a distance between the first microwave radar unit (210) and the second microwave radar unit (220) is 20 cm, a distance between the first microwave radar unit (210) and the third microwave radar unit (230) is 60 cm, and a distance between the first microwave radar unit (210) and the fourth microwave radar unit (240) is 120 cm.

4. The system for detecting the strength of a pavement structure according to claim 1, wherein the impact road assembly (100) comprises a heavy hammer (110), a connecting rod (120), and a bearing member (130). The bearing (130) is arranged on the road, the connecting rod (120) is arranged on the bearing (130), the weight (110) is movably arranged on the connecting rod (120), and the weight (110) is located above the bearing (130), so that the weight (110) can freely fall on the bearing (130) through the connecting rod (120).

5. A method of detecting the strength of a pavement structure by using the system according to any one of claims 1 to 4, characterized by, The method comprises: Impacting the road; A plurality of road detection points on the impacted road emit microwave signals and receive echo signals reflected by the plurality of road detection points; The received echo signals are collected, stored, preprocessed, and the instantaneous vibration frequency values of the plurality of road detection points are calculated; According to the instantaneous vibration frequency values of the plurality of road detection points, the actual elastic modulus of each layer structure of the road is calculated; According to the comparison between the actual elastic modulus and the preset elastic modulus, whether the strength of the road surface is qualified is judged according to the comparison result.

6. The method of claim 5, wherein, The terminal assembly calculates the instantaneous vibration frequency values of the plurality of road detection points according to the received echo signals, which comprises: Finding all extreme points in the road surface micro-motion time domain signal value to calculate intermediate time domain signal values; Judging whether the intermediate time domain signal values meet preset conditions to determine whether the intermediate time domain signal values are inherent modal values; If the preset conditions are not met, the intermediate time domain signal values replace the time domain signal values, and the above steps are re-executed until the preset conditions are met, and the intermediate time domain signal values are target inherent modal values; According to the difference between the time domain signal values and the target inherent modal values, a time domain residual signal is obtained, and the above steps are repeated until no new target inherent modal value can be screened out, and k target inherent modal values are obtained, wherein k is greater than or equal to 1; According to the k target inherent modal values, target time domain signal values are calculated; According to the target time domain signal values, the instantaneous vibration frequency values are calculated.

7. The method of claim 6, wherein, The judgment of whether the intermediate time domain signal values meet the preset conditions comprises: In the entire data sequence time domain signal value, the number of extreme points is equal to the number of zero-crossing points, or the number of extreme points and the number of zero-crossing points differ by not more than one; At any time point, the envelope mean value defined by the local maximum and local minimum of the time domain signal value is zero.

8. The method of claim 6, wherein, The calculation of the instantaneous vibration frequency values according to the target time domain signal values comprises: The target time domain signal values are converted to obtain analytic signal values; According to the analytic signal values, the instantaneous vibration frequency values are calculated.

9. The method of claim 5, wherein, The calculation of the actual elastic modulus of each layer structure of the road according to the instantaneous vibration frequency values of the plurality of road detection points comprises: According to the differences between the instantaneous vibration frequency values of the plurality of road detection points, bearing parameter values of the surface layer, the base layer, the bottom base layer, and the roadbed are obtained; According to the bearing parameter values of the surface layer, the base layer, the bottom base layer, and the roadbed, the actual elastic modulus is calculated.

10. The method of claim 5, wherein, The judgment of whether the strength of the road surface is qualified according to the comparison between the actual elastic modulus and the preset elastic modulus comprises: If the ratio between the actual elastic modulus and the preset elastic modulus is greater than 1, it is concluded that the strength of the highway pavement is qualified.

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