Pavement mechanical response monitoring device and modulus back-calculation method

Abstract

A pavement mechanical response monitoring device and a modulus back-calculation method belong to the technical field of pavement monitoring. The present invention is aimed at the problems in the existing pavement monitoring technology that the sensor layout is complicated, the cost is high, and the damage to the original pavement structure is great. The device includes a cylindrical test rod, the length of which is greater than the sum of the thickness of the pavement surface layer and the base layer; the cylindrical test rod is divided into sections according to the number of pavement layers and thicknesses, and the material modulus of each section of the test rod is close to the modulus of the corresponding pavement layer; the axis of the cylindrical test rod is embedded with a fiber grating string, and a fiber grating point is set at the top and bottom of each section of the test rod, which is used to measure the mechanical response amplitude of the top and bottom of each layer of the pavement under the action of external loads. The present invention is used for pavement monitoring.

Description

Technical Field

[0001] The invention relates to a pavement mechanical response monitoring device and a modulus back-calculation method, and belongs to the technical field of pavement monitoring. Background Art

[0002] The performance of pavement service gradually degrades under repeated traffic loads and complex environments. By deploying sensors inside the pavement to monitor the internal mechanical response of the pavement, effective data support is provided for the evaluation of pavement service performance.

[0003] At present, the sensors deployed inside the pavement usually include horizontal strain sensors, vertical strain sensors, soil pressure gauges, piezometers, temperature sensors, humidity sensors, etc. It is worth noting that the pavement monitoring technology has the following shortcomings: 1) Different types of sensors need to be deployed during the construction of new or expanded pavements. For a large number of existing roads, pavement monitoring technology is difficult to promote and apply; 2) The sensor deployment process is relatively complicated, including positioning, grooving, deployment, cable binding, backfilling, paving, rolling and other processes, which affects the normal construction organization of the pavement; 3) The deployment of sensors has a great damage to the original pavement structure, affecting the test accuracy of the mechanical response inside the pavement; 4) In order to realize the modulus back calculation and service performance evaluation of each layer of the pavement, the sensor deployment scheme needs to be optimized in previous studies. The number of sensors deployed at each layer of the pavement is large, resulting in complicated cables affecting the deployment, and the number of channels required for data acquisition equipment is high, and the monitoring cost is high. Summary of the invention

[0004] In view of the problems in the existing road surface monitoring technology that the sensor layout is complicated, the cost is high, and the damage to the original road surface structure is great, the present invention provides a road surface mechanical response monitoring device and a modulus back calculation method.

[0005] A pavement mechanical response monitoring device of the present invention comprises a cylindrical test rod, the length of which is greater than the sum of the thickness of the pavement surface layer and the base layer;

[0006] The cylindrical test rod is divided into sections according to the number of pavement layers and thickness, and the material modulus of each section of the test rod is made close to the modulus of the corresponding pavement layer;

[0007] A fiber grating string is embedded in the axis of the cylindrical test rod, and a fiber grating point is set at the top and bottom of each test rod to measure the mechanical response amplitude of the top and bottom of each layer of the road surface under the action of external loads.

[0008] According to the pavement mechanical response monitoring device of the present invention, the cylindrical test rod is vertically inserted into the pavement monitoring hole, and each section of the test rod is aligned with the corresponding pavement layer.

[0009] A modulus back-calculation method based on pavement mechanical response of the present invention is implemented based on the pavement mechanical response monitoring device, comprising: applying an external load to the pavement, collecting the mechanical response amplitude of each point of the fiber grating string;

[0010] Calculate the ratio of the mechanical response amplitudes of the top and bottom of each pavement layer as the measured value of the layer modulus characteristic parameter;

[0011] Calculate the ratio of the mechanical response amplitudes of the bottom of the upper layer and the top of the lower layer of the pavement as the characteristic parameter measurement value of the modulus difference between adjacent layers;

[0012] The layered elastic system mechanics theory is used to calculate the theoretical value of the layer modulus characteristic parameter of each layer of the pavement and the theoretical value of the modulus difference characteristic parameter of adjacent layers based on the set modulus of each layer of the pavement.

[0013] The layer modulus characteristic parameter error and the adjacent layer modulus difference characteristic parameter error are calculated based on the theoretical value and the measured value. Then, an optimization algorithm is used to iteratively calculate based on the layer modulus characteristic parameter error and the adjacent layer modulus difference characteristic parameter error to update the set value of the modulus of each layer of the pavement until the error between the corresponding theoretical value and the measured value is less than a threshold value. The set value of the modulus of each layer of the current pavement is used as the final modulus value of each layer of the pavement.

[0014] According to the modulus back-calculation method based on pavement mechanical response of the present invention, it is assumed that the pavement includes n layers, and the layer modulus characteristic parameter measurement value R of the jth layer from top to bottom is 1j for:

[0015]

[0016] In the formula is the mechanical response amplitude of the jth layer top, is the mechanical response amplitude of the jth layer bottom;

[0017] j=1, 2, 3,…, n.

[0018] According to the modulus back-calculation method based on pavement mechanical response of the present invention, the measured value R of the modulus difference characteristic parameter of the jth adjacent layer is 2j for:

[0019]

[0020] According to the modulus back-calculation method based on pavement mechanical response of the present invention, the mechanical response amplitude is the vertical strain.

[0021] According to the modulus back-calculation method based on pavement mechanical response of the present invention, the layered elastic system mechanical theory includes an analytical solution method or a finite element method.

[0022] According to the modulus back-calculation method based on pavement mechanical response of the present invention, the optimization algorithm includes Newton's method, pattern search, genetic algorithm, particle swarm algorithm or agent model method.

[0023] Beneficial effects of the present invention: The pavement mechanical response monitoring device of the present invention has a lightweight pavement mechanical response test rod, which is suitable for sensor deployment and monitoring of newly built, renovated and expanded roads, and existing roads, and has versatility in various application scenarios. The deployment process is simple, the monitoring cost is low, and the original pavement structure is basically not damaged.

[0024] The test rod of the device of the present invention has a simple configuration and has the advantages of easy installation, serial connection of test points, fewer cables, low cost, etc., which is conducive to the large-scale engineering promotion and application of road surface monitoring technology.

[0025] The method of the present invention decouples the mechanical response obtained by monitoring the monitoring points of each layer and backcalculates the modulus of each layer. It has a clear physical meaning and provides effective data and analysis methods for pavement service performance evaluation. It can promote the development of pavement monitoring technology and provide strong support for the large-scale promotion and application of pavement monitoring technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of the pavement mechanical response monitoring device of the present invention being arranged in a pavement structure;

[0027] Figure 2 It is a specific flow chart of the modulus back-calculation method based on pavement mechanical response described in the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0030] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0031] Specific implementation method 1. Combination Figure 1 As shown, the first aspect of the present invention provides a pavement mechanical response monitoring device, comprising a cylindrical test rod, the length of which is greater than the sum of the thickness of the pavement surface layer and the base layer;

[0032] The cylindrical test rod is divided into sections according to the number of pavement layers and thickness, and the material modulus of each section of the test rod is made close to the modulus of the corresponding pavement layer;

[0033] A fiber grating string is embedded in the axis of the cylindrical test rod, and a fiber grating point is set at the top and bottom of each test rod to measure the mechanical response amplitude of the top and bottom of each layer of the road surface under the action of external loads.

[0034] The cylindrical test rod described in this embodiment has the advantage of being lightweight. Its fiber grating points are customized according to the thickness of each layer of the pavement structure; the total number of fiber gratings is twice the total number of pavement structure layers. Since the roadbed is infinitely deep and the length of the test rod is limited, the fiber grating points corresponding to the test rod section of the roadbed are set at the end and top of the test rod section, and the test values ​​at these two locations are used as the test values ​​of the top and bottom of the roadbed layer.

[0035] In a specific implementation, the cylindrical test rod is vertically inserted into the road surface monitoring hole and fixed, and each section of the test rod is aligned with the corresponding road surface layer, thereby ensuring that the fiber grating point position on each section of the test rod corresponds to the top and bottom of each road surface layer.

[0036] Specific implementation method 2: Combination Figure 2 As shown, another aspect of the present invention further provides a modulus back-calculation method based on pavement mechanical response, which is implemented based on the pavement mechanical response monitoring device described in the first specific implementation manner, and includes:

[0037] Apply external loads to the road surface and collect the mechanical response amplitude of each point of the fiber grating string;

[0038] Calculate the ratio of the mechanical response amplitudes of the top and bottom of each pavement layer as the measured value of the layer modulus characteristic parameter;

[0039] Calculate the ratio of the mechanical response amplitudes of the bottom of the upper layer and the top of the lower layer of the pavement as the characteristic parameter measurement value of the modulus difference between adjacent layers;

[0040] The layered elastic system mechanics theory is used to calculate the theoretical value of the layer modulus characteristic parameter of each layer of the pavement and the theoretical value of the modulus difference characteristic parameter of adjacent layers based on the set modulus of each layer of the pavement.

[0041] The layer modulus characteristic parameter error and the adjacent layer modulus difference characteristic parameter error are calculated based on the theoretical value and the measured value. Then, based on the layer modulus characteristic parameter error and the adjacent layer modulus difference characteristic parameter error, a common optimization algorithm is used to perform iterative calculation to update the set value of the modulus of each layer of the pavement until the error between the corresponding theoretical value and the measured value is less than the threshold, that is, the measured value and the theoretical value are as consistent as possible. The set value of the modulus of each layer of the current pavement is used as the final modulus value of each layer of the pavement.

[0042] As an example, the external load described in this embodiment includes but is not limited to static load, impact load, vehicle moving load, etc.

[0043] Furthermore, assuming that the road surface consists of n layers, the measured value of the layer modulus characteristic parameter R of the jth layer from top to bottom is 1j for:

[0044]

[0045] In the formula is the mechanical response amplitude of the jth layer top, is the mechanical response amplitude of the jth layer bottom;

[0046] j=1, 2, 3,…, n.

[0047] The measured value of the characteristic parameter of the modulus difference between the jth adjacent layers R 2j for:

[0048]

[0049] Layer modulus characteristic parameter measurement value R 1j and the measured value of the characteristic parameter of the modulus difference between adjacent layers R 2j The differences in loading effects are eliminated and only the modulus combinations of the layers are relevant.

[0050] As an example, the mechanical response amplitude is vertical strain.

[0051] As an example, the layered elastic system mechanics theory includes an analytical solution method or a finite element method.

[0052] As an example, the optimization algorithm includes Newton's method, pattern search, genetic algorithm, particle swarm algorithm or agent model method.

[0053] Specific embodiment: Combination Figure 1 As shown in the figure, taking a 6-layer pavement structure as an example, the thickness of each layer of the pavement from top to bottom is 0.05, 0.06, 0.07, 0.3, 0.2, +∞m, the Poisson's ratio of each layer from top to bottom is 0.25, 0.25, 0.25, 0.25, 0.25, 0.35, and the density of each layer from top to bottom is 2400, 2400, 2400, 2200, 2200, 1900kg / m 3 .

[0054] The length of the cylindrical test rod is 0.8m, and a multi-point fiber Bragg grating string is embedded in the axis. All the fiber Bragg grating points in the multi-point fiber Bragg grating string are customized according to the thickness of each layer of the pavement structure, and the number of fiber Bragg gratings is twice the number of pavement structure layers. The fiber Bragg grating points are located at 0, 0.049, 0.051, 0.109, 0.111, 0.179, 0.181, 0.478, 0.481, 0.679, 0.681, and 0.8m of the test rod. The test rod is vertically inserted and fixed into the hole by drilling a hole in the pavement, and the fiber Bragg grating points are ensured to be at the top and bottom of each surface layer and base layer. In the roadbed, the fiber Bragg grating points are located at the sum of the thickness of the surface layer and base layer and at the end of the total length of the test rod, such as Figure 1 shown.

[0055] Combination Figure 2 , calculate the modulus value of each pavement layer:

[0056] In the first step, a moving load is applied to the road surface. The load form is a standard axle load of a double-circle single-wheel group, the axle load size is 0.7MPa, the load circle radius is 0.1065m, the double-circle spacing is 0.3195m, the moving speed is 10m / s, and one of the wheel tracks of the load is just above the sensor. The mechanical response amplitude of the multi-point fiber grating string in the test rod is obtained. At 0, 0.049, 0.051, 0.109, 0.111, 0.179, 0.181, 0.479, 0.481, 0.679, 0.681, and 0.8m of the test rod, the mechanical response amplitude is The order is -52.9με, -70.9με, -101.5με, -77.9με, -91.4με, -53.7με, -27.2με, -8.3με, -10.0με, -10.4με, -44.2με, -38.0με.

[0057] Step 2: Calculate the ratio of the mechanical response amplitudes of the top and bottom of each layer as the modulus characteristic parameter of the layer, R 11 , R 12 , R 13 , R 14 , R 15 , R 16 are 0.75, 1.30, 1.70, 3.28, 0.96, and 1.16 respectively; and the ratio of the mechanical response amplitudes of the upper layer bottom and the lower layer top between adjacent layers is calculated as the characteristic parameter of the modulus difference between adjacent layers, R 21 , R 22 , R 23 , R 24 , R 25 They are 0.70, 0.85, 1.97, 0.83 and 0.23 respectively.

[0058] In the third step, combining the analytical solution of the mechanics of the layered elastic system and the particle swarm optimization algorithm, taking the modulus characteristic parameters and difference characteristic parameters as input, the modulus characteristic parameters and difference characteristic parameters obtained by the test rod fiber Bragg grating string test are as close as possible to the modulus characteristic parameters and difference characteristic parameters calculated by the mechanics theory of the layered elastic system. The modulus of each layer is calculated by repeated iterations, and finally, the modulus inversion results of the 1st to 6th layers are 7539, 5241, 4322, 8532, 5742, and 128MPa, respectively.

[0059] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. A modulus back-calculation method based on pavement mechanical response, implemented based on a pavement mechanical response monitoring device, characterized in that: The device includes a cylindrical test rod, the length of which is greater than the sum of the thickness of the pavement surface layer and the base layer; The cylindrical test rod is divided into sections according to the number of pavement layers and thickness, and the material modulus of each section of the test rod is made close to the modulus of the corresponding pavement layer; A fiber grating string is embedded in the axis of the cylindrical test rod, and a fiber grating point is set at the top and bottom of each test rod to measure the mechanical response amplitude of the top and bottom of each layer of the road surface under the action of external loads; The cylindrical test rod is vertically inserted into the pavement monitoring hole, and each section of the test rod is aligned with the corresponding pavement layer; Methods include, Apply external loads to the road surface and collect the mechanical response amplitude of each point of the fiber grating string; Calculate the ratio of the mechanical response amplitudes of the top and bottom of each pavement layer as the measured value of the layer modulus characteristic parameter; Calculate the ratio of the mechanical response amplitudes of the bottom of the upper layer and the top of the lower layer of the pavement as the characteristic parameter measurement value of the modulus difference between adjacent layers; The layered elastic system mechanics theory is used to calculate the theoretical value of the layer modulus characteristic parameter of each layer of the pavement and the theoretical value of the modulus difference characteristic parameter of adjacent layers based on the set modulus of each layer of the pavement. The layer modulus characteristic parameter error and the adjacent layer modulus difference characteristic parameter error are calculated based on the theoretical value and the measured value. Then, an optimization algorithm is used to iteratively calculate based on the layer modulus characteristic parameter error and the adjacent layer modulus difference characteristic parameter error to update the set value of the modulus of each layer of the pavement until the error between the corresponding theoretical value and the measured value is less than a threshold value. The set value of the modulus of each layer of the current pavement is used as the final modulus value of each layer of the pavement.

2. The modulus back-calculation method based on pavement mechanical response according to claim 1 is characterized in that: Assuming that the road surface consists of n layers, the measured value of the layer modulus characteristic parameter R of the jth layer from top to bottom is 1j for: In the formula is the mechanical response amplitude of the j-th layer top, is the mechanical response amplitude of the jth layer bottom; j=1, 2, 3,…, n.

3. The modulus back-calculation method based on pavement mechanical response according to claim 2 is characterized in that: The measured value of the characteristic parameter of the modulus difference between the jth adjacent layers R 2j for:

4. The modulus back-calculation method based on pavement mechanical response according to claim 1, characterized in that: The mechanical response amplitude is the vertical strain.

5. The modulus back-calculation method based on pavement mechanical response according to claim 1, characterized in that: The mechanical theory of layered elastic system includes analytical solution method or finite element method.

6. The modulus back-calculation method based on pavement mechanical response according to claim 1, characterized in that: The optimization algorithm includes Newton's method, pattern search, genetic algorithm, particle swarm algorithm or agent model method.

7. The modulus back-calculation method based on pavement mechanical response according to claim 1, characterized in that: The external loads include static loads, impact loads and vehicle movement loads.

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