Measurement and calculation method of intelligent compaction vibration modulus index to avoid phase detection

Abstract

The present invention discloses a method for measuring and calculating an intelligent compaction vibration modulus index that avoids phase detection. This method no longer uses contact force, but uses two amplitude expressions to calculate the stiffness coefficient, thereby avoiding the measurement of the phase. At the same time, by estimating the range of the damping ratio, the system of equations is converted into a nonlinear programming problem under constraints, reducing the error caused by the ill-conditioned system of equations. The index provided by the present invention can be used as long as the roller has multi-stage frequency modulation and amplitude modulation functions, which lowers the technical threshold and expands the scope of application compared to the original index.

Description

Technical Field

[0001] The present invention belongs to the technical field of intelligent compaction detection of road engineering, and specifically relates to a method for measuring and calculating an intelligent compaction vibration modulus index that avoids phase detection. Background Art

[0002] Intelligent compaction detection technology is to equip the compaction equipment with a series of sensors to detect the dynamic response of the compaction equipment (mainly the center of mass acceleration of the steel wheel of the vibratory roller), and then extract the corresponding intelligent compaction measurement indicators to reflect the compaction quality based on the relationship between the dynamic response and the compaction quality of the material. Compared with the traditional compaction detection method in road engineering, intelligent compaction detection technology has the advantages of real-time, comprehensive and non-destructive.

[0003] The core of intelligent compaction detection technology is to extract appropriate compaction measurement indicators based on the measured dynamic response. Among the currently used compaction indicators, vibration modulus E vib It is the only absolute compaction index related only to the properties of the compacted material, and has the same physical meaning as the structural modulus in engineering. It can detect the modulus in real time while compacting, so it has great development potential. However, compared with classic harmonic ratio indicators such as CMV and CCV, E vib In addition to detecting the acceleration signal of the vibration wheel during measurement, it is also necessary to obtain the phase data of the eccentric block of the steel wheel to calculate the contact force. However, the eccentric block itself is inside the steel wheel, and phase detection is relatively difficult. Currently, most domestic intelligent roller manufacturers do not have this technology, which limits the application of the vibration modulus index. In order to solve this problem, the present invention attempts to explore a new measurement and calculation method for the vibration modulus index that avoids phase detection. Summary of the invention

[0004] The purpose of the present invention is to provide a measurement and calculation method for an intelligent compaction vibration modulus index that circumvents phase detection, so as to avoid the barrier limitations of phase detection technology and facilitate the promotion of the application of vibration modulus indicators in the practice of intelligent compaction detection technology.

[0005] A method for measuring and calculating an intelligent compaction vibration modulus index that avoids phase detection adopts the following steps:

[0006] Step 1: Select a test section with uniform stiffness distribution for intelligent compaction detection, and estimate the approximate range of the damping ratio parameters of the roadbed structure of the test section; whether the stiffness distribution of the test section is uniform can be verified in advance by using the CMV index for repeatability, that is, to check whether similar index measurement results can be obtained by rolling the same area twice with the same roller and operating parameters. The operating parameters include speed, excitation frequency and excitation force amplitude; CMV is an intelligent compaction measurement index, and the calculation formula of this index is as follows:

[0007]

[0008] In the formula, A ω and A 2ω Respectively represent the fundamental frequency and second harmonic components in the acceleration signal spectrum after Fourier transform;

[0009] Step 2: Collecting the original acceleration signal and position information, and matching the acceleration signal with the position information; wherein collecting the original acceleration signal includes installing an acceleration sensor on the central axis of the vibrating wheel of the roller to collect the vertical acceleration signal of the vibrating wheel; collecting the position information includes installing a positioning device on the top of the roller and connecting to a base station or RTK network to receive the position signal; during measurement, the roller uses different excitation frequencies in the forward and backward processes of the compacted strip, and calculates the CMV index based on the detected acceleration signal; during the compaction process, the original acceleration signal and the corresponding position information are recorded;

[0010] Step 3: Back-calculate the vibration wheel displacement based on the acceleration signal: When calculating, first select a certain length of acceleration signal interval, use the average method in the interval to remove the DC component in the original acceleration signal, and then use the processed acceleration result to obtain the velocity and displacement signals through numerical integration; finally, splice the integration results of each period in the interval in sequence to obtain the vibration wheel displacement;

[0011] Step 4: Calculate the stiffness coefficient k d : Use the data in the calculation interval corresponding to the same position in the two previous and subsequent compaction processes to solve the stiffness coefficient of the compacted material;

[0012] Step 5: Calculate the vibration modulus E vib (k d ): k d Value converted to vibration modulus E vib (k d ).

[0013] As a further preferred solution, the stiffness coefficient k in step 4 is d The calculation method is as follows:

[0014] First, refer to the following formula to calculate the natural frequency of the compaction system:

[0015]

[0016] Where ω0 and ξ represent the natural frequency and damping ratio of the compaction system, ω1 and ω2 represent the excitation frequency of the roller during the forward and backward compaction processes, respectively, and F e1 and F e2represents the amplitude of the exciting force during the two compaction processes, A1 and A2 represent the average amplitude of the displacement signal in the calculation interval, m d represents the mass of the vibration wheel; the estimated damping ratio range is introduced into the above formula, and the nonlinear programming algorithm is used to solve the ω0 value corresponding to the minimum F(ω0,ξ), and then k is calculated using the following formula d :

[0017]

[0018] As a further preferred solution, in step 5, k d With E vib (k d ) is as follows:

[0019]

[0020] In the above formula, ν represents the Poisson's ratio of the compacted material, l and R represent the width and radius of the vibrating wheel respectively, and m f Represents the mass of the frame allocated to the vibration wheel; using the above relationship, E can be obtained by iteration. vib (k d )index.

[0021] As a further preferred solution, in step 1, the method for calculating similar index measurement results is: during two compaction processes, the average value and standard deviation of the relative difference of the index at the same position are within a certain range.

[0022] As a further preferred solution, in step 1, the damping ratio range may be estimated using empirical values ​​or determined through experiments.

[0023] As a further preferred solution, in step 2, in order to limit the vibration wheel from being emptied, the CMV measurement value is selected to be less than 10. If it is higher than 10, the amplitude of the roller should be adjusted.

[0024] As a further preferred solution, in step 3, during numerical integration, only the data points of a single cycle are integrated each time, and then the integral constant is corrected according to the principle that the integral area of ​​a single cycle is zero.

[0025] Beneficial effects:

[0026] The present invention provides a method for measuring and calculating an intelligent compaction vibration modulus index that avoids phase detection. The existing vibration modulus index needs to use the contact force between the steel wheel and the compaction structure when calculating, and the back calculation of the contact force requires determining the phase of the exciting force or the eccentric block. The phase detection of the eccentric block is relatively difficult, and most domestic roller manufacturers do not have this technology, resulting in limited use of the vibration modulus. The E in the present invention vib (kd ) index changes the calculation method of the stiffness coefficient and uses the amplitude expression at two different excitation frequencies to replace the calculation of contact force or phase, thereby circumventing the technical restrictions on phase measurement abroad. This index can be used as long as the roller has multi-level frequency and amplitude modulation capabilities, which is achievable for current intelligent rollers. Therefore, it can greatly reduce the threshold for the use of the vibration modulus index and expand its application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the single degree of freedom dynamic model of vibration compaction;

[0028] Figure 2 It is a schematic diagram of the acceleration signal spectrum;

[0029] Figure 3 It is a schematic diagram of the finite element model of roadbed vibration compaction;

[0030] Figure 4 This is a schematic diagram of the acceleration signal obtained by finite element simulation;

[0031] Figure 5 (a) is a schematic diagram of the velocity signal obtained by integrating the acceleration signal once. Figure 5 (b) is a schematic diagram of the displacement signal obtained by quadratic integration of the acceleration signal. Specific embodiments

[0032] The content of the present invention is further explained below in conjunction with specific embodiments and the accompanying drawings.

[0033] The existing vibration modulus calculation method needs to use contact force, and the contact force calculation formula is based on the single degree of freedom dynamic model (such as Figure 1 ) is derived, and the specific expression is as follows:

[0034]

[0035] In the formula, F c is the contact force, F e represents the peak value of the exciting force, represents the phase of the exciting force at time zero, ω represents the exciting frequency, m d and m f Represent the vibration wheel and the frame mass allocated to the vibration wheel, respectively, and a represents the vertical acceleration of the vibration wheel, with upward being positive. In the above formula, the peak value of the contact force is known, but the phase is difficult to measure, which limits the use of the vibration modulus.

[0036] However, it should be noted that the calculation of contact force is essentially to solve Figure 1 In fact, the stiffness coefficient can also be calculated directly using the excitation force and displacement amplitude. Figure 2The single degree of freedom dynamic model in , the amplitude expression can be obtained as follows:

[0037]

[0038] In the formula, A represents the amplitude of the vibrating wheel, ω0 and ξ represent the natural frequency and damping ratio of the compaction system respectively. If the natural frequency ω0 in the above formula can be calculated, the stiffness coefficient can be calculated using the following formula:

[0039]

[0040] Of course, there are two unknowns, ω0 and ξ, in the amplitude expression, and two equations must be provided to solve it. Therefore, it is necessary to use different excitation frequencies in the forward and backward processes on the same compaction strip, thus obtaining two amplitude expressions to form the following set of equations:

[0041]

[0042] Where ω1 and ω2 represent the vibration frequencies of the roller during the forward and backward compaction processes, respectively, and F e1 and F e2 It represents the amplitude of the exciting force during the two compaction processes, and A1 and A2 represent the average amplitude of the displacement signal in the calculation interval.

[0043] The above formula is the calculation principle of the stiffness coefficient in the present invention. It should be noted that, in theory, the natural frequency and stiffness coefficient can be calculated directly according to the above formula, but the above formula is mathematically ill-conditioned and is too sensitive to small deviations of related parameters. In order to improve the calculation accuracy, the present invention adopts a method of estimating the damping ratio, limits the range of variation of the damping ratio, and changes the original set of equations to solve the minimum value problem of the following formula under constraints, so as to avoid large deviations in the calculation results of the natural frequency:

[0044]

[0045] According to the above principle, the present invention adopts the following steps to measure and calculate the vibration modulus:

[0046] Step 1: Select a suitable test section and estimate the approximate range of the damping ratio parameters of the roadbed structure of the test section. The stiffness distribution of the selected section should be relatively uniform and suitable for intelligent compaction testing. If necessary, the CMV index can be used in advance for repeatability verification, that is, to check whether similar index measurement results can be obtained when the same roller and operating parameters (speed, excitation frequency and excitation force amplitude) are used to roll the same area (during the two compaction processes, the average and standard deviation of the relative difference of the index at the same position are within a certain range). The calculation formula of the CMV index is as follows:

[0047]

[0048] In the formula, A ω and A 2ω Respectively represent the fundamental frequency and second harmonic components in the acceleration signal spectrum after Fourier transformation (reference Figure 1 ). The damping ratio range can be estimated using empirical values ​​or determined through experiments.

[0049] Step 2: Collect the original acceleration signal and match the acceleration signal with the position information. Install an acceleration sensor on the central axis of the vibrating wheel to collect the vertical acceleration signal of the vibrating wheel. At the same time, install a positioning device on the top of the roller and connect it to the base station or RTK network to receive the position signal. During the measurement, the roller uses different excitation frequencies in the forward and backward processes of the compacted strip, and calculates the CMV index based on the detected acceleration signal. The CMV measurement value should not be too large (recommended to be less than 10), otherwise the amplitude of the roller should be adjusted to limit the air escape of the vibrating wheel. During the compaction process, record the original acceleration signal and the corresponding position information.

[0050] Step 3: Inversely calculate the displacement of the vibration wheel based on the acceleration signal. When calculating, first select a calculation interval of a certain length, use the average method within the interval to remove the DC component in the original acceleration signal, and then use the processed acceleration results to obtain the velocity and displacement signals through numerical integration. When integrating, only integrate the data points of a single cycle each time, and then correct the integral constant according to the principle that the integral area of ​​a single cycle is zero, and finally splice the integral results of each cycle in the interval in sequence.

[0051] Step 4: Calculate the stiffness coefficient k d The stiffness coefficient is calculated using the data in the calculation interval corresponding to the same position in the two compaction processes. The following expression can be used for calculation:

[0052]

[0053] The estimated damping ratio range is introduced into the above formula, and the nonlinear programming algorithm is used to solve the corresponding ω0 value when F(ω0,ξ) is minimum. Then k is calculated using the following formula: d :

[0054]

[0055] Step 5: Calculate the vibration modulus E vib (k d ). d The value is converted to vibration modulus, and the conversion method is as follows:

[0056]

[0057] In the above formula, ν represents the Poisson's ratio of the compacted material, l and R represent the width and radius of the vibrating wheel respectively. Using the above relationship, E can be obtained by iteration. vib (k d )index

[0058] First, the estimation method of damping ratio is explained. The estimation of damping ratio can be done by empirical method and experimental method. The empirical method can use the following empirical formula or refer to the empirical values ​​in previous research materials:

[0059] Vertical damping ratio of cohesive soil:

[0060]

[0061] Vertical damping ratio of sand and silt:

[0062]

[0063] In the formula, is the dimensionless mass ratio, m and A are the mass and bottom area of ​​the vibrating load, respectively, which are the mass and contact area of ​​the vibrating wheel in this paper, and ρ is the density of the roadbed soil.

[0064] The accuracy of the indicators in the present invention is verified by means of finite element simulation. A vibration compaction finite element model is established based on the assumption of plane strain. Figure 3 The selection of the relevant parameters of the vibrating wheel refers to the XCMG XS263J single steel wheel vibrating roller. The main working parameters of this type of roller are shown in Table 1. The compacted material is assumed to be purely elastic, and the calculation accuracy of the finite element model is verified using the Lundberg theoretical solution.

[0065] Table 1 E under different compaction material modulus conditions vib (k c )

[0066]

[0067] Taking the compacted material modulus of 100MPa as an example, Figure 4The calculation results of the acceleration signal of the center of mass of the vibration wheel obtained by finite element simulation when the excitation frequency is 32Hz (weak vibration mode) are given (sampling frequency is 1000Hz, and the calculation interval is 0.5s). According to step 3, the discrete acceleration data points are integrated using the trapezoidal formula (the acceleration signal obtained by the finite element simulation has no zero-point drift phenomenon, and the process of removing the DC component of the original signal can be omitted). Each integration selects data points of approximately one cycle, and 33 are selected in this example. The integral area of ​​the signal within an excitation cycle is calculated again using the trapezoidal formula for the signal after the integration. The average amplitude of the signal can be obtained by dividing the result by the cycle length. According to the principle that the integral area of ​​a single cycle is zero, this value is subtracted from the obtained signal data points. Repeat the above steps, and finally splice the calculation results of each cycle in sequence to obtain the complete integrated waveform within the calculation interval. According to the above method, integrating once can obtain the velocity signal, and integrating twice can obtain the displacement signal, such as Figure 5 As shown. The average amplitude of the displacement signal in the calculated interval is 1.24mm. Then adjust the excitation frequency of the roller in the finite element model to 27Hz, the excitation force to 145kN, and obtain a new set of acceleration data. The above method is also used to obtain the average displacement amplitude of 1.01mm. Substitute the relevant data into the expression in step 4, the damping ratio limit range is taken as 0.05~0.15, and the minimum value condition of the expression is obtained based on the fmincon function of MATLAB, thereby obtaining k d The calculated result is 80.64MN / m. Further, substituting this value into the expression in step 5, the vibration modulus E is obtained through iterative calculation. vib (k d ) result is 94.06MPa.

[0068] Using the above method, Table 2 gives the E under different roadbed modulus conditions. vib (k d ), where the excitation frequencies of the two vibration compaction simulations are 27Hz and 32Hz respectively, and the excitation force amplitude is generally taken as 290kN. However, under the condition of 27Hz, when the roadbed modulus is above 80MPa, the excitation force amplitude is reduced to 145kN to limit the voiding. According to Table 1, it can be seen that the relative error between the index value and the actual modulus is within 15%, and except for the low modulus area, the relative error in most cases does not exceed 10%. Such accuracy can meet the requirements of engineering applications.

[0069] Table 2 E under different compaction material modulus conditions vib (k d )

[0070]

[0071]

[0072] Finally, it should be pointed out that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. All components not specified in this embodiment can be implemented using existing technologies.

Claims

1. A method for measuring and calculating an intelligent compaction vibration modulus index that avoids phase detection, characterized in that: Use the following steps: Step 1: Select a test section with uniform stiffness distribution for intelligent compaction testing, and estimate the range of the damping ratio parameters of the roadbed structure of the test section; whether the stiffness distribution of the test section is uniform can be verified in advance by using the CMV index for repeatability, that is, to check whether similar index measurement results can be obtained by rolling the same area twice with the same roller and operating parameters. The operating parameters include speed, excitation frequency and excitation force amplitude; CMV is an intelligent compaction measurement index, and the calculation formula of this index is as follows: In the formula, A ω and A 2ω Respectively represent the fundamental frequency and second harmonic components in the acceleration signal spectrum after Fourier transform; Step 2: Collecting the original acceleration signal and position information, and matching the acceleration signal with the position information; wherein collecting the original acceleration signal includes installing an acceleration sensor on the central axis of the vibrating wheel of the roller to collect the vertical acceleration signal of the vibrating wheel; collecting the position information includes installing a positioning device on the top of the roller and connecting to a base station or RTK network to receive the position signal; during measurement, the roller uses different excitation frequencies in the forward and backward processes of the compacted strip, and calculates the CMV index based on the detected acceleration signal; during the compaction process, the original acceleration signal and the corresponding position information are recorded; Step 3: Back-calculate the vibration wheel displacement based on the acceleration signal: When calculating, first select a certain length of acceleration signal interval, use the average method in the interval to remove the DC component in the original acceleration signal, and then use the processed acceleration result to obtain the velocity and displacement signals through numerical integration; finally, splice the integration results of each period in the interval in sequence to obtain the vibration wheel displacement; Step 4: Calculate the stiffness coefficient k d : Use the data in the calculation interval corresponding to the same position in the two previous and subsequent compaction processes to solve the stiffness coefficient of the compacted material; Step 5: Calculate the vibration modulus E vib (k d ): k d Value converted to vibration modulus E vib (k d ).

2. The method for measuring and calculating the intelligent compaction vibration modulus index for avoiding phase detection according to claim 1, characterized in that: Stiffness coefficient k in step 4 d The calculation method is as follows: First, refer to the following formula to calculate the natural frequency of the compaction system: Where ω0 and ξ represent the natural frequency and damping ratio of the compaction system, ω1 and ω2 represent the excitation frequency of the roller during the forward and backward compaction processes, respectively, and F e1 and F e2 represents the amplitude of the exciting force during the two compaction processes, A1 and A2 represent the average amplitude of the displacement signal in the calculation interval, m d represents the mass of the vibration wheel; the estimated damping ratio range is introduced into the above formula, and the nonlinear programming algorithm is used to solve the ω0 value corresponding to the minimum F(ω0,ξ), and then k is calculated using the following formula d :

3. The method for measuring and calculating the intelligent compaction vibration modulus index for avoiding phase detection according to claim 1, characterized in that: Step 5 k d With E vib (k d ) is as follows: In the above formula, ν represents the Poisson's ratio of the compacted material, l and R represent the width and radius of the vibrating wheel respectively, and m f Indicates the mass of the frame assigned to the vibration wheel, m d represents the mass of the vibration wheel; using the above relationship, E can be obtained by iteration method. vib (k d )index.

4. The method for measuring and calculating the intelligent compaction vibration modulus index for avoiding phase detection according to claim 1, characterized in that: In step 1, the method for calculating similar index measurement results is as follows: during two compaction processes, the average value and standard deviation of the relative difference of the index at the same position are within a certain range.

5. The method for measuring and calculating the intelligent compaction vibration modulus index for avoiding phase detection according to claim 1, characterized in that: In step 1, the damping ratio range can be estimated using empirical values ​​or determined through experiments.

6. The method for measuring and calculating the intelligent compaction vibration modulus index for avoiding phase detection according to claim 1, characterized in that: In step 2, in order to limit the air escape of the vibrating wheel, the CMV measurement value is selected to be less than 10. If it is higher than 10, the amplitude of the roller should be adjusted.

7. The method for measuring and calculating the intelligent compaction vibration modulus index for avoiding phase detection according to claim 1, characterized in that: In step 3, during numerical integration, only the data points of a single cycle are integrated each time, and then the integral constant is corrected according to the principle that the integral area of ​​a single cycle is zero.

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