CN113624838B - Pavement layering modulus calculation method for constructing dispersion curve based on deflection time course curve - Google Patents
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Abstract
The invention discloses a pavement layering modulus calculation method for constructing a dispersion curve based on a deflection time course curve, which comprises the following steps of 1) obtaining the deflection time course curve measured on site by a nondestructive testing deflection instrument; 2) The data measured by each two sensors are divided into a group; 3) Obtaining a time domain curve for filtering noise and invalid wave bands; 4) Obtaining a corresponding dispersion curve and a phase difference of each group of data, and selecting an effective signal section according to the phase difference; 5) Constructing a dispersion curve of the surface wave propagating in the pavement in each group of data, and drawing a complete total dispersion curve; 6) Carrying out average treatment on the data points to obtain an average dispersion curve; 7) And carrying out inversion analysis on the average dispersion curve to obtain a value of the change of the shear wave speed along with the depth of the pavement, and obtaining an elastic modulus value along with the change of the depth according to a linear elastic theory. The invention obtains specific modulus values at different road depths and obtains a set of rapid and accurate modulus measurement calculation method.
Description
Technical Field
The invention relates to the field of nondestructive testing of a pavement in road engineering, in particular to a pavement layering modulus calculation method for constructing a dispersion curve based on a deflection time course curve.
Background
Maintaining adequate load bearing capacity is one of the important goals of pavement maintenance and repair, and the mainstream method of estimating load bearing capacity of pavement layers is to evaluate the modulus characteristics thereof, and the change and attenuation of modulus can be considered as an important indicator of degradation of pavement performance. The methods for evaluating the pavement modulus at the present stage mainly comprise two methods: laboratory tests in coring in situ and nondestructive in situ. However, in situ coring can compromise the integrity of the pavement and destroy the original confining pressure of the pavement to the core sample. Therefore, the nondestructive testing method is a mainstream means for evaluating the pavement performance in recent years because of low cost, environmental friendliness and good reliability. In the existing nondestructive testing method, means for measuring pavement modulus are mainly divided into two main types: deflection measurement techniques and surface wave detection techniques. The technology based on deflection measurement also comprises a method for obtaining deflection data by impacting the ground and a method for measuring the deflection data by laser, wherein the modulus of the pavement is difficult to calculate by the latter, and the former uses a falling weight type deflection meter FWD as the main component, so that the characteristics of the pavement modulus can be rapidly detected and can be effectively calculated, and the technology is favored by a plurality of students. However, the traditional method of calculating modulus by FWD is based on the back-calculation of the deflection basin, which is insensitive to the variation of the modulus of the surface layer, the measured result is not unique, is easily affected by the chosen initial value, and only the average of the modulus of the whole layer thickness consisting of the same material can be measured. Surface wave detection-based techniques are also classified into several broad categories: SASW method, MASK method, PSPA. The SASW method can accurately calculate the thickness of each layer of each pavement and the exact modulus value of each layer which changes along with the change of depth, the MASK method can calculate the exact modulus value of each layer of the non-deep pavement which changes along with the change of depth, and the PSPA method can calculate the average modulus value of the shallow pavement. The method has perfect wave propagation theory, but is very slow in detection speed due to the manual operation and hand-held placement operation when being used for on-site measurement, is unfavorable for multi-point rapid detection, and has certain potential safety hazard.
In the past research, fresh students combine the nondestructive testing technologies of the two different principles to use, and the rapid testing characteristic of the deflection measuring instrument and the theoretical perfection characteristic of the surface wave spectrum analysis technology are combined, a series of fluctuation theoretical analysis is carried out on a time course curve measured on site, and a pavement dispersion curve is constructed, so that a modulus value is calculated, a set of rapid and accurate modulus measurement calculation method is obtained, and the rapid and accurate modulus measurement calculation method contributes to the pavement nondestructive testing technology.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a pavement layering modulus calculation method for constructing a dispersion curve based on a deflection time course curve.
The aim of the invention can be achieved by the following technical scheme:
a pavement layering modulus calculation method for constructing a dispersion curve based on a deflection time course curve comprises the following steps:
1) Obtaining deflection time course curves measured on site by a nondestructive testing deflection instrument, namely deflection value data which are measured by each sensor and change along with time in a period of time when weights such as drop hammers or wheels impact the ground;
2) Grouping sensors of the deflection instrument, wherein data measured by each two sensors are grouped into a group;
3) Analyzing deflection time course data measured on site based on theoretical analysis process of nondestructive testing technology (such as SASW, MASK method, etc.) of surface wave spectrum analysis to obtain time domain curve with noise and invalid wave band filtered;
4) Performing Fourier transformation and a series of fluctuation theoretical calculation on the time domain curve to obtain a corresponding dispersion curve and a phase difference of each group of data, and selecting an effective signal section according to the phase difference;
5) Calculating the phase speed of the surface wave according to the phase angle information, so as to construct a dispersion curve of the surface wave propagating in the pavement in each group of data, namely a curve of the phase speed changing along with the frequency/wavelength, converging the dispersion curves constructed by each group of data, and drawing a complete total dispersion curve;
6) Because the data points in the total dispersion curve are too many, the subsequent inversion analysis is not facilitated, and therefore the data points are subjected to average processing to obtain an average dispersion curve;
7) And carrying out inversion analysis on the average dispersion curve to obtain a value of the change of the shear wave speed along with the depth of the pavement, and obtaining an elastic modulus value along with the change of the depth according to a linear elastic theory.
In the step 2), the reason why the plurality of deflection sensors are grouped in pairs is that the theoretical research of the SASW (surface wave spectroscopy) is based on the data received by two adjacent sensors, and a dispersion curve is constructed by calculating the signal phase difference between the adjacent sensors; the two sensor pitches of each group are different, and the different sensor pitches can draw dispersion curves covering different frequency ranges.
In the step 4), the effective signal segment is selected according to the following steps: (1) Removing low-quality phase information segments, namely phase angles which do not accord with general trends, including obvious fluctuation phase angles and backward zigzag phase angles; (2) Removing a signal segment under the near field effect according to a filtering formula of the near field effect; (3) rejecting signal segments having wavelengths less than 4 times the receiver spacing.
Compared with the prior art, the invention has the following advantages:
1. the method can analyze and process the deflection time course curve based on the dispersion characteristic of the surface wave to construct a corresponding road surface dispersion curve; and obtaining the pavement model characteristic according to the constructed dispersion curve. Compared with the prior art, the invention can fully utilize the characteristics of the existing nondestructive testing technology, combines the rapid detection characteristics of the deflection measuring instrument with the theoretical perfection characteristics of the seismic wave spectrum analysis technology, obtains a whole set of rapid and accurate modulus measurement calculation method, and makes a contribution to the pavement nondestructive testing technology.
2. The invention can rapidly and accurately obtain the elastic modulus of each layer of pavement under the condition of not damaging the asphalt pavement structure. Compared with the prior art, the method can not only obtain the average modulus of the whole pavement, but also rapidly and accurately obtain the exact modulus value of each layer at different pavement depths, thereby perfecting the pavement modulus evaluation system.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
FIG. 2 is a plot of deflection time course measured by a deflection sensor.
Fig. 3 is a time domain signal at two sensors within a set of data.
Fig. 4 is a frequency domain signal at two sensors within a set of data.
Fig. 5 is phase difference information between two sensors within a set of data.
Fig. 6 is a graph of joint dispersion for several sets of data.
Fig. 7 is an average dispersion curve.
FIG. 8 is a graph of elastic modulus as a function of asphalt pavement depth.
Detailed Description
The invention will now be described in detail with reference to the drawings and specific examples.
The invention is based on the existing theoretical research on measuring pavement modulus by seismic waves, further expands application, and provides a method for constructing a pavement dispersion curve by using a deflection time course curve measured on site, and obtains pavement modulus values which change along with depth based on the dispersion curve. In the embodiment, the FWD of the drop hammer type deflection instrument is taken as an example to obtain field actual measurement data, namely deflection time course curve; because the falling weight impacts the ground to generate certain earthquake waves, a series of fluctuation theoretical analysis is carried out on the FWD deflection time course curve by adopting the related earthquake wave spectrum analysis technology such as the theoretical research of SASW method, and a road surface dispersion curve is constructed, so that the modulus values at different road surface depths are obtained.
As shown in FIG. 1, the invention provides a pavement layering modulus calculation method for constructing a dispersion curve based on a deflection time course curve, which comprises the following steps:
1) Obtaining deflection time course curves measured on site by a nondestructive testing deflection instrument, namely deflection value data which are measured by each sensor and change along with time in a period of time when weights such as drop hammers or wheels impact the ground;
2) Grouping sensors of the deflection instrument, wherein data measured by each two sensors are grouped into a group;
the reason why the plurality of deflection sensors are grouped in pairs is that theoretical research of the seismic wave spectrum detection technology is based on data received by two adjacent sensors, and a dispersion curve is constructed by calculating signal phase differences between the adjacent sensors; the two sensor pitches of each group are different, and the different sensor pitches can draw dispersion curves covering different frequency ranges.
3) Analyzing deflection time course data measured on site based on theoretical analysis process of nondestructive testing technology (such as SASW, MASK method, etc.) of surface wave spectrum analysis to obtain time domain curve with noise and invalid wave band filtered;
4) Performing Fourier transformation and a series of fluctuation theoretical calculation on the time domain curve to obtain a corresponding dispersion curve and a phase difference of each group of data, and selecting an effective signal section according to the phase difference;
the effective signal section is selected according to the following steps:
1. removing low-quality phase information segments, namely phase angles which do not accord with general trends, including obvious fluctuation phase angles and backward zigzag phase angles;
2. removing a signal segment under the near field effect according to a filtering formula of the near field effect;
3. and eliminating signal segments with the wavelength smaller than 4 times of the interval between the receivers.
5) Calculating the phase speed of the surface wave according to the phase angle information, so as to construct a dispersion curve of the surface wave propagating in the pavement in each group of data, namely a curve of the phase speed changing along with the frequency/wavelength, converging the dispersion curves constructed by each group of data, and drawing a complete total dispersion curve;
6) Because the data points in the total dispersion curve are too many, the subsequent inversion analysis is not facilitated, and therefore the data points are subjected to average processing to obtain an average dispersion curve;
7) And carrying out inversion analysis on the average dispersion curve to obtain a value of the change of the shear wave speed along with the depth of the pavement, and obtaining an elastic modulus value along with the change of the depth according to a linear elastic theory.
Examples:
since the falling weight deflectometer FWD is the more mainstream deflectometer at this stage, in this example, the FWD is used to acquire the deflection time-course curve.
1) Obtaining deflection value data of each sensor, which is measured by the FWD and changes with time, in a time period that the drop hammer impacts the ground, wherein the deflection time course curve is measured on site, and the deflection value data is shown in FIG. 2;
2) Grouping sensors of the deflection instrument FWD, wherein data measured by each two sensors are grouped into one group;
3) Researching a theoretical analysis process of a nondestructive testing technology SASW method based on surface wave spectrum analysis, analyzing deflection time-course data measured on site to obtain a time-domain curve for filtering noise and invalid wave bands, wherein the time-domain curve of one group of data is shown in figure 3;
4) Performing Fourier transformation and a series of fluctuation theoretical calculation on the time domain curve to obtain a corresponding dispersion curve and a phase difference of each group of data, and selecting an effective signal segment according to the phase difference, wherein the frequency domain signal of one group of data is shown as a figure 4, the phase angle information of one group of data is shown as a figure 5, and the shaded part in the figure 5 is an unselected signal segment;
5) Calculating the phase velocity of the surface wave according to the phase angle information, thereby constructing a dispersion curve of the surface wave propagating in the pavement in each group of data, namely a curve of the phase velocity changing along with the frequency/wavelength, converging the dispersion curves constructed by each group of data, and drawing a complete total dispersion curve, as shown in figure 6;
6) Since the data points in the total dispersion curve are too many, the subsequent inversion analysis is not facilitated, and therefore the data points are subjected to average processing to obtain an average dispersion curve, as shown in fig. 7;
7) Inversion analysis is carried out on the average dispersion curve to obtain a value of the change of the shear wave speed along with the depth of the pavement, and an elastic modulus value along with the change of the depth is obtained according to a linear elastic theory, as shown in fig. 8.
Claims (3)
1. A pavement layering modulus calculation method for constructing a dispersion curve based on a deflection time course curve is characterized by comprising the following steps: the method comprises the following steps:
1) Obtaining deflection time course curves measured on site by a nondestructive testing deflection instrument, namely deflection value data which are measured by each sensor and change along with time in a time period when a heavy object impacts the ground;
2) Grouping sensors of the deflection instrument, wherein data measured by each two sensors are grouped into a group;
3) Analyzing deflection time course data measured on site in a theoretical analysis process of a nondestructive testing technology based on surface wave spectrum analysis to obtain a time domain curve for filtering noise and invalid wave bands;
4) Performing Fourier transformation and a series of fluctuation theoretical calculation on the time domain curve to obtain a corresponding dispersion curve and a phase difference of each group of data, and selecting an effective signal section according to the phase difference;
5) Calculating the phase speed of the surface wave according to the phase angle information, so as to construct a dispersion curve of the surface wave propagating in the pavement in each group of data, namely a curve of the phase speed changing along with the frequency/wavelength, converging the dispersion curves constructed by each group of data, and drawing a complete total dispersion curve;
6) Because the data points in the total dispersion curve are too many, the subsequent inversion analysis is not facilitated, and therefore the data points are subjected to average processing to obtain an average dispersion curve;
7) And carrying out inversion analysis on the average dispersion curve to obtain a value of the change of the shear wave speed along with the depth of the pavement, and obtaining an elastic modulus value along with the change of the depth according to a linear elastic theory.
2. The pavement layered modulus calculation method for constructing a dispersion curve based on a deflection time course curve according to claim 1, which is characterized by comprising the following steps: in the step 2), the reason why the plurality of deflection sensors are grouped in pairs is that the theoretical research of the SASW (surface wave spectroscopy) is based on the data received by two adjacent sensors, and a dispersion curve is constructed by calculating the signal phase difference between the adjacent sensors; the two sensor pitches of each group are different, and the different sensor pitches can draw dispersion curves covering different frequency ranges.
3. The pavement modulus calculation method for constructing a dispersion curve based on a FWD deflection time course curve according to claim 1, wherein the pavement modulus calculation method is characterized by comprising the following steps: in the step 4), the effective signal segment is selected according to the following steps: (1) Removing low-quality phase information segments, namely phase angles which do not accord with general trends, including obvious fluctuation phase angles and backward zigzag phase angles; (2) Removing a signal segment under the near field effect according to a filtering formula of the near field effect; (3) rejecting signal segments having wavelengths less than 4 times the receiver spacing.
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| CN1576817A (en) * | 2004-09-07 | 2005-02-09 | 长安大学 | Modulus anti-inference method for rock-fill roadbed |
| CN108037187A (en) * | 2017-12-05 | 2018-05-15 | 南京航空航天大学 | Airfield runway based on Rayleigh waves comes to nothing monitoring method |
| CN111041949A (en) * | 2019-12-05 | 2020-04-21 | 同济大学 | A crack depth detection method for asphalt pavement based on surface wave dispersion curve |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1576817A (en) * | 2004-09-07 | 2005-02-09 | 长安大学 | Modulus anti-inference method for rock-fill roadbed |
| CN108037187A (en) * | 2017-12-05 | 2018-05-15 | 南京航空航天大学 | Airfield runway based on Rayleigh waves comes to nothing monitoring method |
| CN111041949A (en) * | 2019-12-05 | 2020-04-21 | 同济大学 | A crack depth detection method for asphalt pavement based on surface wave dispersion curve |
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| 刚性基层沥青路面参数动态反演;曹丹丹;赵延庆;孔繁盛;王国忠;;中国公路学报;20180815(第08期);全文 * |
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