Asphalt pavement strain and modulus monitoring method based on embedded strain sensor group

Abstract

The present invention discloses a method for monitoring the strain and modulus of an asphalt pavement based on an embedded strain sensor group. Strain sensors with different equivalent moduli are embedded in a pavement structure to form a strain sensor group. Based on a logistic curve model satisfied by the modulus ratio and strain ratio of the strain sensor group and the asphalt mixture, the actual strain and actual modulus of the asphalt mixture are solved according to the output of the strain sensor group, thereby overcoming the measurement deviation caused by the incoordination between the sensor and the asphalt mixture caused by temperature, achieving accurate monitoring of the true strain response of the pavement structure under any temperature condition, and further monitoring the modulus of the pavement structure; the strain and modulus of the asphalt pavement can also be measured without stopping the vehicle, which is more accurate than the traditional static measurement method of the asphalt pavement modulus, and can more accurately judge the actual health status of the pavement structure.

Description

Technical Field

[0001] The present invention relates to the technical field of road structure health monitoring, and in particular to an asphalt pavement strain and modulus monitoring method based on an embedded strain sensor group. Background Art

[0002] Obtaining the structural dynamic response of asphalt pavement under actual traffic load during its service life can scientifically guide the pavement structure design and reasonably explain the pavement mechanical failure mechanism. It is an important part of establishing a long-life pavement structure design system. The horizontal tensile strain of the asphalt layer is the main monitoring object of pavement structure health monitoring. When the horizontal tensile strain exceeds a certain level, it will cause pavement cracking. Therefore, it is necessary to embed strain sensors in the pavement structure to monitor the strain state of the pavement structure in real time.

[0003] However, asphalt pavement material (i.e., asphalt mixture) is a temperature-sensitive material. The modulus of asphalt mixture is lower under high temperature conditions in summer, while the modulus of asphalt mixture is higher under low temperature conditions in winter. Therefore, the modulus of asphalt mixture under different temperature environments is quite different. However, the change in the material modulus of the strain sensor is not obvious when the ambient temperature changes. Therefore, with the change in ambient temperature, the deformation coordination between the strain sensor buried in the asphalt pavement structure and the surrounding asphalt mixture will also change. If the tensile modulus of the strain sensor is greater than the modulus of the asphalt mixture, the measurement result of the strain sensor will be smaller than the actual deformation of the asphalt mixture. Similarly, if the tensile modulus of the strain sensor is smaller than the modulus of the asphalt mixture, the measurement result of the strain sensor will be greater than the actual deformation of the asphalt mixture. Only when the modulus of the strain sensor is the same as the modulus of the asphalt mixture can the strain sensor deform in coordination with the asphalt mixture, and the output result of the strain sensor is the true strain of the asphalt mixture.

[0004] In the field of strain sensors, it is currently difficult to produce a strain sensor whose modulus changes in real time and has the same modulus as the asphalt mixture at the same temperature. Therefore, when existing strain sensors measure the strain of asphalt mixtures at different temperatures, there will inevitably be measurement deviations. Therefore, it is necessary to solve the measurement errors caused by the incompatibility between existing strain sensors and pavement materials. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for monitoring strain and modulus of asphalt pavement based on an embedded strain sensor group, comprising the following steps:

[0006] S1. Establishing a strain sensor group, wherein the strain sensor group includes no less than 2 strain sensors, and the tensile equivalent modulus of each strain sensor is set to be unequal to each other;

[0007] S2. Number each strain sensor in the strain sensor group. Assume that there are n strain sensors in the strain sensor group, and the i-th strain sensor is marked as strain sensor i, where 1<=i<=n, and the tensile equivalent modulus of strain sensor i is recorded as E ei ;

[0008] S3, burying all strain sensors in the strain sensor group at intervals along the length direction of the road surface at the positions to be measured in the road surface structure, and the interval between any two adjacent strain sensors is set to 1-2 cm;

[0009] S4, collect data from the strain sensor group in real time, and record the strain output of strain sensor i as ε si ;

[0010] S5, substituting the strain output of each strain sensor in the strain sensor group and the equivalent modulus of the strain sensor group into equation (1) to solve the strain magnitude of the pavement structure under the vehicle load and the pavement modulus magnitude;

[0011]

[0012] Among them, ε a Indicates the strain size, E a represents the pavement modulus, a, b, c are the logistic curve parameters of the strain sensor, and a=1+e b .

[0013] The technical solution further defined in the present invention is:

[0014] Further, in step S5,

[0015] When n=2 in formula (1), the strain magnitude of the pavement structure under vehicle load and the pavement modulus magnitude are solved by formula (2):

[0016]

[0017] Among them, ε a Indicates the strain size, E a Indicates the pavement modulus;

[0018] When n>2 in formula (1), the strain magnitude ε of the pavement structure under vehicle load is a and pavement modulus E a As the parameter to be fitted, the tensile equivalent modulus of the strain sensor group is taken as x, where x = [E e1 , E e2 , ..., E en ], the strain output of the strain sensor group is y, where y = [ε e1 , ε e2, ..., ε en ], based on the least squares fitting method (3), the strain size of the pavement structure under the vehicle load and the pavement modulus size are obtained.

[0019]

[0020] Among them, ε a Indicates the strain size, E a Indicates the pavement modulus.

[0021] In the above-mentioned asphalt pavement strain and modulus monitoring method based on embedded strain sensor group, the type of strain sensor is set to be a fiber grating strain sensor.

[0022] In the above-mentioned asphalt pavement strain and modulus monitoring method based on embedded strain sensor group, in step S3, the distance between any two adjacent strain sensors is set to 1.5 cm.

[0023] In the above-mentioned asphalt pavement strain and modulus monitoring method based on embedded strain sensor group, the embedding depth of the strain sensor in the pavement structure is set to 15 cm.

[0024] The beneficial effects of the present invention are:

[0025] In the present invention, strain sensors with different equivalent moduli are embedded in the pavement structure to form a strain sensor group. Based on the logistic curve model satisfied by the modulus ratio and strain ratio of the strain sensor group and the asphalt mixture, the actual strain and actual modulus of the asphalt mixture are solved according to the output of the strain sensor group, thereby overcoming the measurement deviation caused by the incoordination between the sensor and the asphalt mixture caused by temperature, achieving accurate monitoring of the true strain response of the pavement structure under any temperature conditions, and further monitoring the modulus of the pavement structure; the strain and modulus of the asphalt pavement can also be measured without stopping the vehicle, and the measured modulus of the asphalt pavement is the instantaneous modulus, which reflects the viscoelasticity of the asphalt pavement material. Compared with the traditional static measurement method of the asphalt pavement modulus, it is more accurate and can more accurately judge the actual health status of the pavement structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A cross-sectional schematic diagram of a pavement structure and arrangement of strain sensors in an embodiment of the present invention;

[0027] Figure 2 The strain data collected by the strain sensor in the embodiment of the present invention 0.5s before and after the peak value of the strain load;

[0028] Figure 3 is the real strain of the asphalt pavement calculated in the embodiment of the present invention;

[0029] Figure 4 It is the true modulus of the asphalt pavement calculated in the embodiment of the present invention. DETAILED DESCRIPTION

[0030] The present embodiment provides a method for monitoring strain and modulus of asphalt pavement based on an embedded strain sensor group, comprising the following steps:

[0031] S1. Assemble a strain sensor group, which includes three fiber Bragg grating strain sensors, which are respectively denoted as strain sensor 1, strain sensor 2 and strain sensor 3. The tensile equivalent modulus of strain sensor 1, strain sensor 2 and strain sensor 3 are set to 0.39 GPa, 4.21 GPa and 7.85 GPa respectively.

[0032] S2. Number each strain sensor in the strain sensor group. Assume that there are n strain sensors in the strain sensor group, and the i-th strain sensor is marked as strain sensor i, where 1<=i<=n, and the tensile equivalent modulus of strain sensor i is recorded as E ei ;

[0033] S3, all strain sensors in the strain sensor group are buried at intervals along the length direction of the road surface at the positions to be measured in the road surface structure, and the spacing between any two adjacent strain sensors is set to 1.5 cm, so as to ensure that the speed and tire load of the vehicle are basically the same when passing through the two strain sensors; Figure 1 As shown, it is a cross-sectional schematic diagram of the pavement structure and the arrangement of strain sensors. The buried depth of the strain sensor is set to 15 cm, the tire load is set to 50 KN, and the loading speed is set to 22 km / h.

[0034] S4, collect data from the strain sensor group in real time, and record the strain output of strain sensor i as ε si ;

[0035] like Figure 2 As shown in the figure, the strain data collected 0.5s before and after the strain load peak of the strain sensor. It can be seen that the strain results measured by the strain sensor are not the same, and the strain peak value of strain sensor 1 is greater than the strain peak value of strain sensor 2, and the strain peak value of strain sensor 2 is greater than the strain peak value of strain sensor 3, which once again shows that the equivalent modulus of the strain sensor itself will affect the measurement results of the strain sensor. The reason for the above phenomenon is that the larger the tensile equivalent modulus of the strain sensor, the less likely the strain sensor is to deform, which will cause the strain sensor measurement output result to become smaller.

[0036] S5. Solving the strain and modulus of the asphalt pavement requires the output of at least two strain sensors, so the strain and modulus of the asphalt pavement are solved according to the output of strain sensor 1 and strain sensor 2, the output of strain sensor 2 and strain sensor 3, and the output of strain sensor 1 and strain sensor 3 respectively;

[0037] The logistic curve parameters a, b, and c of the strain sensor group are selected as 1.203, -1.593, and 2.190, respectively; the outputs of strain sensor 1 and strain sensor 2, the outputs of strain sensor 2 and strain sensor 3, the outputs of strain sensor 1 and strain sensor 3, and the corresponding tensile equivalent modulus of the strain sensors are respectively substituted into the following formula to solve the strain size of the pavement structure under the vehicle load and the pavement modulus size,

[0038]

[0039] Among them, ε a Indicates the strain size, E a represents the pavement modulus, a, b, c are the logistic curve parameters of the strain sensor;

[0040] Furthermore, the strain and modulus of the asphalt pavement are expressed as follows: a and pavement modulus E a , the results are as follows Figure 3 and Figure 4 As shown,

[0041]

[0042] Among them, ε a Indicates the strain size, E a Indicates the pavement modulus;

[0043] Furthermore, based on the outputs of strain sensor 1, strain sensor 2, and strain sensor 3, the strain and modulus of the asphalt pavement are solved. The strain and modulus of the asphalt pavement are obtained by fitting the following overdetermined equations using the least squares method. The solution results are as follows: Figure 3 and Figure 4 As shown;

[0044]

[0045] like Figure 3 As shown in , the actual strain of the asphalt pavement obtained based on the strain output of 2 or 3 strain sensors is basically the same; Figure 4As shown, it can be seen that the real modulus of the solved asphalt pavement is constant in a short time, so the average value of all moments is taken. The average values ​​of the pavement modulus solved by the outputs of strain sensor 1 and strain sensor 2, strain sensor 2 and strain sensor 3, strain sensor 1 and strain sensor 3, strain sensor 1, strain sensor 2 and strain sensor 3 are 1.89 GPa, 1.82 GPa, 1.87 GPa and 1.87 GPa respectively. It can be seen that the pavement modulus calculated by this method is basically consistent.

[0046] The field core sample of AC-25, the third layer of the pavement structure, was obtained by coring. The modulus of the core sample was measured to be 1.82 GPa through a uniaxial compression test, and was found to be close to the pavement modulus result measured by the strain sensor. This shows that the asphalt pavement strain and modulus monitoring method based on an embedded strain sensor group adopted in the present invention can overcome the difference in coordination between the strain sensor and the asphalt mixture caused by temperature changes, and ensure that the measurement result of the strain sensor is the true state of the pavement structure.

[0047] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A method for monitoring strain and modulus of asphalt pavement based on an embedded strain sensor group, characterized in that: The following steps are included S1. Establishing a strain sensor group, wherein the strain sensor group includes no less than 2 strain sensors, and the tensile equivalent modulus of each strain sensor is set to be unequal to each other; S2. Number each strain sensor in the strain sensor group. Assume that there are n strain sensors in the strain sensor group, and the i-th strain sensor is marked as strain sensor i, where 1 <= i <= n, and the tensile equivalent modulus of strain sensor i is recorded as E ei ; S3, burying all strain sensors in the strain sensor group at intervals along the length direction of the road surface at the positions to be measured in the road surface structure, and the interval between any two adjacent strain sensors is set to 1-2 cm; S4, collect data from the strain sensor group in real time, and record the strain output of strain sensor i as ε si ; S5, substituting the strain output of each strain sensor in the strain sensor group and the equivalent modulus of the strain sensor group into equation (1) to solve the strain magnitude of the pavement structure under the vehicle load and the pavement modulus magnitude; Among them, ε a Indicates the strain size, E a represents the pavement modulus, a, b, c are the logistic curve parameters of the strain sensor, and a=1+e b ; In step S5, when n=2 in equation (1), the strain magnitude of the pavement structure under the vehicle load and the pavement modulus magnitude are solved by equation (2). Among them, ε a Indicates the strain size, E a Indicates the pavement modulus; When n>2 in formula (1), the strain magnitude ε of the pavement structure under vehicle load is a and pavement modulus E a As the parameter to be fitted, the tensile equivalent modulus of the strain sensor group is taken as x, where x = [E e1 , E e2 , ..., E en ], the strain output of the strain sensor group is y, where y = [ε e1 , ε e2 , ..., ε en ], based on the least squares fitting method (3), the strain size of the pavement structure under the vehicle load and the pavement modulus size are obtained. Among them, ε a Indicates the strain size, E a Indicates the pavement modulus.

2. The asphalt pavement strain and modulus monitoring method based on embedded strain sensor group according to claim 1 is characterized in that: The type of the strain sensor is set to be a fiber grating strain sensor.

3. The asphalt pavement strain and modulus monitoring method based on embedded strain sensor group according to claim 1 is characterized in that: In step S3, the distance between any two adjacent strain sensors is set to 1.5 cm.

4. The asphalt pavement strain and modulus monitoring method based on embedded strain sensor group according to claim 3 is characterized in that: The embedding depth of the strain sensor in the pavement structure is set to 15 cm.

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