Clustered strain sensors for monitoring strain, modulus, and stress in asphalt pavement

Abstract

The present invention discloses a cluster strain sensor capable of monitoring the strain, modulus and stress of an asphalt pavement, and relates to the technical field of strain sensors. The key points of the technical solution are that a plurality of strain sensor units with different equivalent moduli are included. Due to the softening effect of a flexible sleeve and the separation effect of a connecting rod, the measurement of each strain sensor unit will not affect each other, and the measurement direction of each strain sensor unit is kept consistent, and the same driving load is borne. Therefore, the output strain of each strain sensor unit is only related to the size of its equivalent modulus. Since the modulus ratio and strain ratio of each strain sensor unit and the asphalt mixture satisfy a one-to-one corresponding functional relationship, and the corresponding functional relationship is the same, the actual strain and modulus of the asphalt pavement can be obtained according to the output strain and corresponding modulus of each strain sensor unit in the cluster strain sensor, and the stress of the asphalt pavement can be further calculated.

Description

Technical Field

[0001] The present invention relates to the technical field of strain sensors, and in particular to a cluster strain sensor capable of monitoring the strain, modulus and stress of an asphalt pavement. Background Art

[0002] Obtaining the structural dynamic response of asphalt pavement under actual vehicle load during its service life can scientifically guide the pavement structure design and reasonably explain the pavement mechanical failure mechanism, which is an important part of establishing a long-life pavement structure design system. Currently, the sensors used to measure the mechanical response of asphalt pavement structures are mainly strain sensors, and it is generally believed that the output of the strain sensor is the true strain value of the asphalt pavement.

[0003] However, asphalt pavement materials, namely asphalt mixtures, are temperature sensitive, and the modulus of asphalt mixtures changes with temperature. Therefore, under different ambient temperatures, the relative size of the modulus between the strain sensor and the asphalt mixture will change, causing the strain sensor to produce large measurement errors at certain temperatures. In particular, under high temperature conditions, the measurement output result of the strain sensor is smaller than the actual value, and under low temperature conditions, the measurement result of the strain sensor is greater than the actual value. Therefore, the error in the measurement output of the existing strain sensor will lead to misjudgment of the structural state of the asphalt pavement.

[0004] At present, in the field of asphalt pavement structure health monitoring, there is still a lack of real-time measurement of other mechanical parameters of asphalt pavements, such as modulus and stress. The current asphalt pavement modulus measurement mainly uses a drop weight deflectometer, which is a detection method and is not suitable for on-site real-time monitoring of the modulus of pavement structure. Due to the multi-layer structure of the pavement, the drop weight deflectometer has a large error when evaluating the modulus of each layer.

[0005] Therefore, there is an urgent need for a sensor that can accurately measure the strain, modulus and stress of asphalt pavement to solve the problem of monitoring the health status of asphalt pavement structure. Summary of the invention

[0006] The purpose of the present invention is to provide a cluster strain sensor that can monitor the strain, modulus and stress of asphalt pavement. In order to overcome the measurement deviation of the sensor caused by the uncoordinated deformation of the strain sensor and the asphalt mixture due to temperature, and the lack of a device for real-time monitoring of the modulus and stress of the pavement structure, a cluster strain sensor that can monitor the strain, modulus and stress of asphalt pavement is proposed. It can not only accurately measure the actual strain response of the pavement structure, but also measure the real-time modulus and stress of the pavement structure.

[0007] The above technical objectives of the present invention are achieved through the following technical solutions:

[0008] A cluster strain sensor capable of monitoring strain, modulus and stress of asphalt pavement, comprising:

[0009] A plurality of mutually parallel strain sensor units, adjacent strain sensor units are connected by connecting rods, and a wire sheath is nested and fixed on the strain sensor unit at the end position;

[0010] Define the number of strain sensor units as n, then the number of connecting rods is n-1;

[0011] The strain sensor unit includes:

[0012] The elastic strain beam is located inside the strain sensor unit and is in the shape of a cylindrical rod. It is used to sense the changes in the asphalt pavement and deform synchronously with it.

[0013] A micro-resistance strain gauge is bonded and fixed to the mid-span position of the elastic strain beam surface to collect and transmit deformation data of the elastic strain beam;

[0014] The end flanges are located at both ends of the elastic strain beam and fixed relatively thereto, and the overall structure is a rectangular parallelepiped;

[0015] The protective cover extends along the length direction of the elastic strain beam and is formed between the two end flanges, and is sleeved on the elastic strain beam outside the micro-resistance strain gauge to cooperate with the end flanges to form a package for the interior;

[0016] Flexible sleeve, which is installed outside the protective sleeve and the end flange to protect the inside of the strain sensor unit

[0017] Further configuration: the side surfaces of the protective cover adjacent to the remaining strain sensor units are partially increased in wall thickness outward to form screw holes, the screw holes match the connecting rods, a circular hole for accommodating the screw holes is opened at the corresponding screw hole positions on the flexible cover, and the wire sheath is arranged outside the circular hole at the end position.

[0018] It is further configured that the connecting rod is a hollow rod-shaped structure for accommodating a wire connected to the micro-resistance strain gauge, and a thread matching the screw hole is formed on the outer side wall of the end of the connecting rod.

[0019] Further arrangement: the wire sheath is a hollow structure, one end of which is sleeved outside the screw hole and fixed to the screw hole and the flexible sleeve by glue. There are two wire sheaths, and the wire is introduced into the wire sheath from the micro resistance strain gauge through the connecting rod and the screw hole according to the principle of proximity.

[0020] It is further arranged that: the end flange includes two parts formed integrally, the size of the part fixed to the elastic strain beam is smaller than the size of the other part, the small-sized part of the end flange is located at both ends of the elastic strain beam and embedded in the port of the protective cover to form a sliding structure; the large-sized part of the end flange is embedded in the protective cover along the degree of elasticity of the elastic strain beam and is flush with the end edge of the protective cover.

[0021] It is further configured that: the number of strain sensor units n is greater than or equal to 2, and the materials and dimensions of the flexible sleeve, the protective sleeve and the end flange of each strain sensor unit are the same.

[0022] Further setting: The equivalent modulus of each strain sensor unit is different, and the equivalent modulus of the strain sensor is calculated by the following formula:

[0023]

[0024] Among them, E e is the equivalent modulus of the strain sensor unit; E d is the modulus of the elastic strain beam material; A d is the cross-sectional area of ​​the elastic strain beam; A is the area enclosed by the cross-sectional area of ​​the flexible sleeve.

[0025] Further configuration: the length of the connecting rod is greater than or equal to the nominal maximum particle size of the asphalt mixture.

[0026] Preferably, the flexible sleeve has a thickness of 1 to 2 mm and is made of rubber.

[0027] In summary, the present invention has the following beneficial effects:

[0028] 1. In the present invention, the measurement deviation caused by the uncoordinated deformation of the strain sensor and the asphalt mixture caused by temperature is taken into consideration. This measurement deviation is related to the equivalent modulus of the strain sensor and the modulus of the asphalt mixture. The present invention proposes a cluster strain sensor based on the one-to-one functional relationship between the modulus ratio and strain ratio of the strain sensor and the asphalt mixture. This cluster strain sensor includes multiple strain sensor units with different equivalent moduli. Due to the softening effect of the flexible sleeve and the separation effect of the connecting rod, the measurement of each strain sensor unit will not affect each other. Due to the connection effect of the connecting rod, the measurement direction of each strain sensor unit remains consistent and bears the same driving load. Therefore, the output strain of each strain sensor unit is only related to the size of its equivalent modulus.

[0029] 2. In the present invention, since the materials and sizes of the flexible sleeve, protective sleeve and end flange of each strain sensor unit are consistent, the modulus ratio and strain ratio of each strain sensor unit and the asphalt mixture satisfy a one-to-one functional relationship, and the functional relationship corresponding to each strain sensor unit is the same. Therefore, the actual strain and modulus of the asphalt pavement can be obtained according to the output strain and corresponding modulus of each strain sensor unit in the cluster strain sensor, and the stress of the asphalt pavement can be further calculated. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention is further described below in conjunction with the accompanying drawings.

[0031] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0032] Figure 2 It is a schematic diagram of the assembly of the elastic strain beam, the micro-resistance strain gauge, the protective cover and the end flange in the present invention;

[0033] Figure 3 It is a schematic diagram of the assembly of the strain sensor unit in the present invention;

[0034] Figure 4 It is a schematic diagram of the side-by-side connection between strain sensor units in the present invention;

[0035] Figure 5 It is a schematic diagram of the connection between the strain sensor unit and the wire sheath in the present invention;

[0036] Figure 6 It is a schematic diagram of the distribution of the conductors of the micro-resistance strain gauge in the present invention.

[0037] In the figure, 1. micro resistance strain gauge; 2. elastic strain beam; 3. end flange; 4. protective cover; 5. screw hole; 6. flexible cover; 7. round hole; 8. strain sensor unit; 9. connecting rod; 10. wire sheath; 11. wire. DETAILED DESCRIPTION

[0038] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0039] The technical solution adopted by the present invention is:

[0040] A cluster strain sensor capable of monitoring the strain, modulus and stress of an asphalt pavement specifically comprises: n strain sensor units 8, n-1 connecting rods 9, and 2 wire sheaths 10.

[0041] Before designing the present invention, the key points to consider include:

[0042] a. The inharmonious deformation of the strain sensor and the asphalt mixture caused by temperature leads to the measurement deviation of the sensor. This measurement deviation is related to the equivalent modulus of the strain sensor and the modulus of the asphalt mixture;

[0043] b. The modulus ratio and strain ratio of the strain sensor and the asphalt mixture satisfy a one-to-one functional relationship:

[0044] ε s / ε a =f(E s / E a ) (1)

[0045] In the formula, ε s and E s are the output strain and equivalent modulus of the strain sensor, ε a and E a is the strain and modulus of the asphalt pavement;

[0046] c. In actual measurement, the strain and modulus of the asphalt pavement are unknown quantities, while the output strain and equivalent modulus of the strain sensor are known quantities. At least two equations (1) are required to solve the strain and modulus of the asphalt pavement, so at least two strain sensors are required, and the equivalent modulus of each strain sensor is not equal; at the same time, the functional relationship formula (1) between the modulus ratio and strain ratio of each strain sensor and the asphalt mixture needs to be the same. Under these conditions, the asphalt mixture modulus and strain can be inversely calculated based on the output strain and equivalent modulus of the strain sensor, and the stress of the asphalt pavement can be calculated based on the inversely calculated asphalt mixture modulus and strain.

[0047] Taking the above factors into consideration, through experiments and practice, the present invention provides a clustered strain sensor. In the clustered strain sensor, the strain sensor unit 8 includes:

[0048] The elastic strain beam 2 is arranged inside the strain sensor unit 8 and is in the shape of a cylindrical rod, and is used to sense the change of the asphalt road surface and deform synchronously with it;

[0049] A micro-resistance strain gauge 1 is bonded and fixed to the mid-span position of the surface of the elastic strain beam 2, and is used to collect and transmit deformation data of the elastic strain beam 2;

[0050] The end flanges 3 are located at both ends of the elastic strain beam 2 and fixed relatively thereto, and are in a rectangular parallelepiped structure as a whole;

[0051] The protective cover 4 extends along the length direction of the elastic strain beam 2 and is formed between the two end flanges 3, and is sleeved on the elastic strain beam 2 outside the micro-resistance strain gauge 1, and is used to cooperate with the end flanges 3 to form a package for the inside;

[0052] The flexible sleeve 6 is sleeved outside the protective sleeve 4 and the end flange 3 to protect the interior of the strain sensor unit 8 .

[0053] In the embodiment, the specific structure is as follows Figures 1 to 6 As shown, it specifically includes: 3 strain sensor units 8, 2 connecting rods 9, and 2 wire sheaths 10;

[0054] like Figure 2 and 3 As shown, a pair of circular local areas of the lateral opposite surfaces of the protective cover 4 increase the wall thickness outward and set screw holes 5, and the increased wall thickness is equal to the thickness of the flexible cover 6; a pair of circular holes 7 are set on the lateral opposite surfaces of the flexible cover 6 to match the screw holes 5 on the lateral opposite surfaces of the protective cover 4; the micro-resistance strain gauge 1 is adhered to the mid-span position of the surface of the elastic strain beam 2 to measure the strain of the elastic strain beam 2; the protective cover 4 covers the elastic strain beam 2 and the micro-resistance strain gauge 1 to prevent the elastic strain beam 2 and the micro-resistance strain gauge 1 from being directly damaged by the action of external materials;

[0055] The end flange 3 is divided into two sections along the measuring direction. The section with a smaller circumscribed circle radius is fixed at both ends of the elastic strain beam 2 and embedded in the port of the protective cover 4 to form a sliding structure. The section with a larger circumscribed circle radius is flush with the protective cover 4 along the measuring direction. The flexible cover 6 wraps the side surfaces of the end flange 3 and the protective cover 4 to avoid mutual influence between the strain sensor units 8 during measurement.

[0056] like Figure 4 As shown, the connecting rod 9 is a hollow structure, and a thread is set on the outer wall of the end to match the screw hole 5 of the protective cover 4. The strain sensor unit 8 is assembled side by side through the thread at the end of the connecting rod 9 and the screw hole 5 of the protective cover 4 to ensure that the measuring direction of the strain sensor unit 8 always remains consistent.

[0057] like Figure 5 As shown, the end of the wire sheath 10 is aligned with the screw hole 5 of the protective cover 4 of the strain sensor unit 8 at the edge, and then fixed by gluing.

[0058] like Figure 6 As shown, the wire 11 of the micro-resistance strain gauge 1 is introduced into the edge strain sensor unit 8 through the connecting rod 9 according to the proximity principle, and then introduced into the wire sheath 10 through the screw hole 5 of the protective cover 4 of the edge strain sensor unit 8, and the wire 11 of the micro-resistance strain gauge 1 of the edge strain sensor is directly introduced into the wire sheath 10 through the screw hole 5 of its protective cover 4.

[0059] In addition, the number of strain sensor units 8 is 3, not less than 2, and the materials and sizes of the flexible sleeve 6, protective sleeve 4, and end flange 3 of the three strain sensor units 8 are completely consistent, and the materials and cross-sectional sizes of the elastic strain beam 2 may be different; the equivalent moduli of the strain sensor units 8 are different, and the difference between them is more than 2 times.

[0060] Meanwhile, the length of the connecting rod 9 is greater than or equal to the nominal maximum particle size of the asphalt mixture; the thickness of the flexible sleeve 6 is 1 to 2 mm and is made of rubber.

[0061] The equivalent modulus of the strain sensor is calculated by the following formula:

[0062]

[0063] Among them, E e E is the equivalent modulus of the strain sensor unit 8; d A is the modulus of the material of the elastic strain beam 2; d is the cross-sectional area of ​​the elastic strain beam 2; A is the area enclosed by the cross-sectional area of ​​the flexible sleeve 6.

[0064] The present invention includes multiple strain sensor units 8 with different equivalent moduli. Due to the softening effect of the flexible sleeve 6 and the separating effect of the connecting rod 9, the measurements of each strain sensor unit 8 will not affect each other. Due to the connecting effect of the connecting rod 9, the measurement direction of each strain sensor unit 8 remains consistent and bears the same driving load. Therefore, the output strain of each strain sensor unit 8 is only related to the size of its equivalent modulus. Since the materials and sizes of the flexible sleeve 6, protective sleeve 4 and end flange 3 of each strain sensor unit 8 are consistent, the modulus ratio and strain ratio of each strain sensor unit 8 and the asphalt mixture satisfy a one-to-one corresponding functional relationship, and the functional relationships corresponding to each strain sensor unit 8 are the same. Therefore, the actual strain and modulus of the asphalt pavement can be obtained according to the output strain and corresponding modulus of each strain sensor unit 8 in the cluster strain sensor, and the stress of the asphalt pavement can be further calculated.

[0065] The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are within the scope of the technical solution of the invention.

Claims

1. A cluster strain sensor capable of monitoring the strain, modulus and stress of asphalt pavement, characterized in that: include: A plurality of mutually parallel strain sensor units (8), each strain sensor unit (8) having a different equivalent modulus, adjacent strain sensor units (8) being connected via a connecting rod (9), and a wire sheath (10) being nested and fixed on the strain sensor unit (8) at the end position; The number of the strain sensor units (8) is defined as n, and the number of the connecting rods (9) is n-1; Wherein, the strain sensor unit (8) comprises: An elastic strain beam (2), arranged inside the strain sensor unit (8), is in the shape of a cylindrical rod and is used to sense changes in the asphalt pavement and deform synchronously with the changes; A micro-resistance strain gauge (1) is bonded and fixed to the mid-span position of the surface of the elastic strain beam (2) and is used to collect and transmit deformation data of the elastic strain beam (2); The end flanges (3) are located at both ends of the elastic strain beam (2) and are relatively fixed thereto, and are in a rectangular parallelepiped structure as a whole; A protective sleeve (4) extending along the length direction of the elastic strain beam (2) and formed between the two end flanges (3), sleeved on the elastic strain beam (2) outside the micro-resistance strain gauge (1), and used to cooperate with the end flanges (3) to form a package for the interior; A flexible sleeve (6) is sleeved outside the protective sleeve (4) and the end flange (3) and is used to protect the interior of the strain sensor unit (8).

2. The cluster strain sensor capable of monitoring the strain, modulus and stress of asphalt pavement according to claim 1 is characterized in that: The side surfaces of the protective sleeve (4) adjacent to the other strain sensor units (8) are partially increased in wall thickness outward to form screw holes (5), the screw holes (5) match the connecting rods (9), a circular hole (7) for accommodating the screw holes (5) is provided on the flexible sleeve (6) at the position corresponding to the screw holes (5), and the wire sheath (10) is sleeved outside the circular hole (7) at the end position.

3. The cluster strain sensor capable of monitoring the strain, modulus and stress of asphalt pavement according to claim 2 is characterized in that: The connecting rod (9) is a hollow rod-shaped structure, used to accommodate a wire (11) connected to the micro-resistance strain gauge (1), and a thread matching the screw hole (5) is formed on the outer side wall of the end of the connecting rod (9).

4. The cluster strain sensor capable of monitoring the strain, modulus and stress of asphalt pavement according to claim 3 is characterized by: The wire sheath (10) is a hollow structure, one end of which is sleeved outside the screw hole (5) and is bonded and fixed to the screw hole (5) and the flexible sheath (6) by glue. The number of the wire sheaths (10) is two, and the wire (11) is introduced into the wire sheath (10) from the micro resistance strain gauge (1) through the connecting rod (9) and the screw hole (5) according to the principle of proximity.

5. The cluster strain sensor capable of monitoring the strain, modulus and stress of asphalt pavement according to claim 4 is characterized in that: The end flange (3) comprises two integrally formed parts, the size of the part fixed to the elastic strain beam (2) is smaller than the size of the other part, the small-sized part of the end flange (3) is located at both ends of the elastic strain beam (2) and is embedded in the port of the protective cover (4) to form a sliding structure; the large-sized part of the end flange (3) is embedded in the protective cover (4) along the vertical direction of the elastic strain beam (2) and is flush with the end edge of the protective cover (4).

6. The cluster strain sensor capable of monitoring the strain, modulus and stress of asphalt pavement according to claim 5 is characterized in that: The number n of the strain sensor units (8) is greater than or equal to 2, and the materials and dimensions of the flexible sleeve (6), the protective sleeve (4), and the end flange (3) of each strain sensor unit (8) are the same.

7. The cluster strain sensor capable of monitoring the strain, modulus and stress of asphalt pavement according to claim 1 is characterized in that: The equivalent modulus of the strain sensor unit (8) is calculated by the following formula: Among them, E e is the equivalent modulus of the strain sensor unit (8); E d A is the modulus of the material of the elastic strain beam (2); d is the cross-sectional area of ​​the elastic strain beam (2); and A is the area enclosed by the cross-sectional area of ​​the flexible sleeve (6).

8. The cluster strain sensor capable of monitoring the strain, modulus and stress of asphalt pavement according to claim 1 is characterized by: The length of the connecting rod (9) is greater than or equal to the nominal maximum particle size of the asphalt mixture.

9. The cluster strain sensor capable of monitoring the strain, modulus and stress of asphalt pavement according to claim 1 is characterized in that: The thickness of the flexible sleeve (6) is 1 to 2 mm and it is made of rubber.

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