CN104457604B - Asphalt pavement site radial strain test sensor based on optical fiber sensing technology - Google Patents

Abstract

The invention relates to an on-site radial strain test sensor for asphalt pavement based on optical fiber sensing technology, which belongs to the technical field of road equipment. It is characterized in that it is buried before the pavement layer to be tested is laid. Before placing, pour the potting glue into the potting tank, seal the potting port and the heat insulation layer. Control the shape of the ring arrangement of the armored wires of the test section at the test site. After the normal paving and rolling of the pavement structure is completed, the grating is slowly tightened and temporarily fixed. Pull the control line of the sealing valve system, so that the optical fiber in the potting groove is separated from the sealing sleeve and directly contacts with the potting compound. After the potting glue has fully reached its rigidity, remove the temporary fixation of the optical fiber at the demodulator. The effects and benefits of the invention are low cost, simple use, convenient layout, no influence on the normal construction of the pavement, and little influence on the stress field distribution of the pavement structure itself. The invention avoids the damage to the sensor caused by the large deformation in the forming process of the asphalt pavement structure, and maintains the high precision during the test.

Description

On-site radial strain test sensor for asphalt pavement based on optical fiber sensing technology

technical field

The invention belongs to the technical field of road experiment equipment, and relates to an on-site radial strain test sensor for asphalt pavement based on optical fiber sensing technology.

technical background

Road is an important part of transportation infrastructure. In recent years, my country's road construction investment has accounted for 2%-3% of my country's GDP. But from a global perspective, the early disease problem of roads has never been fundamentally resolved. On the other hand, the impact of road maintenance on road traffic has become more and more unbearable, and it is easy to cause vicious traffic accidents. Therefore, with the development of the economy and the demand for heavy traffic on the road, improving the performance of the road structure has become a key research goal of road engineering.

For a long time, the design of asphalt mixtures at home and abroad has been mainly based on empirical methods. With the increasing requirements for road structures to withstand high traffic volume, heavy loads and long life, the performance of road structures and their damage evolution are becoming more and more grasped. Attention has been paid to it, and the research work in the field of road engineering at home and abroad has aggravated the application of mechanical analysis in road structure design. The fundamental solution to the early disease problem of road structure requires an accurate grasp of the mechanical behavior of the comprehensive action of road materials, structures, hydrogeology, loads and the environment, and the lack of effective testing methods to provide reference data is one of the key obstacles to this work .

The introduction of indoor experimental methods such as dynamic modulus, repeated loading, and static creep marks the beginning of the fine mechanical analysis of asphalt pavement materials, but for asphalt pavement materials with uneven height, anisotropy, and different tension and compression, field tests are more important. It can reflect the actual response of the road structure under the coupled action of environment-traffic loads. How to correlate the field road structure response with the precise test of laboratory road test specimens is also of great significance.

The harsh service environment of the road structure and the characteristics of the asphalt mixture require that the sensors embedded in the road structure must be able to withstand high temperature (up to 160 ° C), wet working environment, high rolling pressure, repeated heavy loads, etc., and have a large coverage , so the vast majority of traditional civil engineering sensors cannot be directly used in road structures. However, the existing on-site road surface strain measurement technology based on optical fiber technology is limited to linear measurement, and it is difficult to control the gauge length of the sensor to a small size due to the size limitation of optical fiber sensitive components and packaging materials.

Contents of the invention

The purpose of the present invention is to provide a kind of on-the-spot radial strain test sensor of asphalt pavement based on optical fiber sensing technology.

Technical scheme of the present invention is as follows:

An on-site radial strain test sensor for asphalt pavement based on optical fiber sensing technology, including bare fiber grating, armored protection wire, shape controller, potting groove, single-end fixing block, deformation buffer groove, heat insulation layer and sealing Valve system; bare fiber grating as deformation sensitive element. The containment valve system includes control lines, gaskets, and isolation sleeves.

Thread a bare fiber grating or a sleeved fiber grating into the armored wire used as the measurement section, making sure that the grating is always in the ring test area. One end of the fiber grating leads is fixed in the potting tank by a single-end fixing block, and the other end of the fiber grating is used as a signal transmission section to pass through the sealing sleeve part of the sealing valve system in the potting tank in advance, and then through the deformation buffer tank and Reserved holes at both ends of the potting tank. Before the sensor is buried, the sealing gasket of the sealing valve system in the potting tank is fixed on the inside of the potting tank with low-viscosity glue, and the other gasket located outside the potting tank is close to the wall of the potting tank to ensure that the outside of the potting tank The reserved hole at the end is sealed, and the potting compound does not flow out of the reserved hole in the potting tank. The control line of the sealing valve system located outside the potting tank is led out of the pavement structure by a separate armored protection line or the control line and the optical fiber transmission line pass through the same armored protection line to lead to the connection demodulation instrument point. The upper part of the potting tank is provided with a potting port. A heat insulation layer made of heat insulation material is arranged outside the potting tank and the deformation buffer tank. The heat insulation layer can avoid the rapid curing effect of high temperature on the potting compound when the asphalt pavement is formed. The shape controller can be a cylinder or a ring, which is used to control the circular layout shape of the armored wire of the test section when the sensor is laid, and can be removed after the sensor is placed.

The single-end fixing block is made of fiber reinforced plastic (FRP, Fiber Reinforced Polymer), epoxy resin material or metal material; the potting glue is made of low-viscosity epoxy resin material; the sealing valve system control line is made of metal wire or small deformation Composed of plastic wires; the sealing sleeve of the sealing valve system is made of soft plastic or rubber material; the gasket of the sealing valve system is made of soft plastic or rubber material; the potting groove is made of metal material or fiber reinforced plastic; the shape controller is not limited to materials .

The on-site radial strain test sensor of the asphalt pavement is buried before the pavement layer to be tested is laid. Before the sensor is placed, the potting glue is prepared and poured into the potting tank, and then the potting port and the heat insulation layer are sealed. When laying out the sensor, use the shape controller to control the circular layout shape of the armored wire in the test section at the test site, slightly tighten the optical fiber at the sensor connection demodulator, and then remove the shape controller. A portion of bitumen mixture can be pre-spread on the sensor for better shaping. After completing the normal paving and rolling of the pavement structure, connect the transmission fiber to the grating demodulator, and slowly pull the transmission fiber while observing the data of the demodulator, until the grating stops stretching when it starts to be stretched, and transmits it externally The segment is temporarily fixed, keeping a slight hand pull. Pull the control line of the sealing valve system, so that the sealing gasket in the potting tank is separated from the bonded side wall of the potting tank until it reaches the opposite side wall, so that the optical fiber in the potting tank is separated from the isolation sleeve and directly contacts the potting compound. After the potting compound fully reaches the rigidity, remove the temporary fixation of the optical fiber at the demodulator. During the test, dynamic and static loads can be carried out at the center of the measuring ring of the sensor, and the strain value measured by the sensor can be converted into the radial strain value at the measuring point.

The effects and benefits of the invention are low cost, simple use, convenient layout, and no influence on normal road construction. Since the diameter of the optical fiber itself is very small, the diameter of the sensor involved in the present invention can also be made small, which has little influence on the stress field distribution of the road surface structure itself. The invention avoids the damage to the sensor caused by the large deformation in the forming process of the asphalt pavement structure, and maintains the high precision during the test. The measuring radius of the sensor involved in the present invention is adjustable, and it can be continuously arranged at different radii in the center of the loading point at the same time, which is difficult for linear sensors limited by gauge length. The annular design of the sensor involved in the present invention is more convenient to compare with the loading test results of the cylindrical asphalt test block in the asphalt mixture chamber. Since the annular perimeter is 3.14 times the diameter, the annular design can be tested on the basis of the same gauge length. The area is smaller and the precision controllability is higher. The sensor involved in the invention can measure static strain and dynamic strain, and can also be used as on-site dynamic response testing equipment to cooperate with asphalt mixture dynamic modulus experiment, and can also cooperate with road deflection equipment to measure internal response of road structure.

Description of drawings

Accompanying drawing 1 is the structural diagram of the main components of the on-site radial strain test sensor and the sealing valve system of the asphalt pavement based on the optical fiber sensing technology.

Accompanying drawing 2 is a schematic diagram of the overall layout of the sensor.

In the figure: 1 bare optical fiber grating; 2 armored protection line; 3 single-end fixed block; 4 control line; demodulator; 11 shape controllers.

detailed description

The specific implementation manner of the present invention will be described in detail below in conjunction with the technical scheme and the accompanying drawings.

As shown in the figure, it mainly includes bare fiber grating 1, armored protection line 2, single-end fixing block 3, control line 4, isolation envelope 5, potting groove 6, sealing gasket 7, deformation buffer groove 8, and heat insulation layer 9 ; Fiber Bragg grating demodulator 10; Shape controller 11.

Thread the fiber grating tape sleeve through the armored wire used as the measurement section, making sure that the grating is always in the annular test area. One end of the fiber grating is fixed in the potting tank by a single-end fixing block, and the other end, as a signal transmission section, passes through the deformation buffer tank and the reserved hole in the potting tank respectively, and passes through the sealing valve system in the potting tank in advance part of the isolation envelope. The isolation sleeve and the gasket of the sealed valve system are connected by a control line. Before the sensor is buried, the sealing gasket of the sealing valve system in the potting tank is fixed on one side of the potting tank with low-viscosity glue. Outflow from the fiber reserved hole in the groove. The control line of the sealing valve system located outside the potting tank is led out of the pavement structure through a separate armored line or leads to the connection demodulation instrument point through the same armored line together with the optical fiber transmission line. The upper part of the potting tank is provided with a potting port. A heat insulation layer made of heat insulation material is arranged outside the potting tank and the deformation buffer tank.

The on-site radial dynamic and static strain test sensor of the asphalt pavement is buried before the pavement layer to be tested is laid. When the sensor is buried, the potting glue is prepared and poured into the potting tank, and then the potting port and the heat insulation layer are sealed. When laying out the sensor, use the shape controller to control the circular layout shape of the armored wire in the test section at the test site, slightly tighten the optical fiber at the sensor connection demodulator, and then remove the shape controller. Parts of cleared mix can be pre-laid on the sensor for better shaping. After the normal paving and rolling of the pavement structure is completed, the transmission fiber is connected to the grating demodulator, and the grating is slowly tightened while observing the data of the demodulator, until the grating is tense and starts to be pulled, stop stretching and temporarily fix it. Pull the control line of the sealing valve system, so that the sealing gasket in the potting tank is separated from the bonded side wall of the potting tank until it reaches the opposite side wall, so that the optical fiber in the potting tank is separated from the isolation sleeve and directly contacts the potting compound. After the potting compound fully reaches the rigidity, remove the simple fixation of the optical fiber at the demodulator. During the test, dynamic and static loads can be carried out at the corresponding center of the sensor measuring ring, and the strain value measured by the sensor can be converted into the radial strain value at the measuring point.

The potting tank and the deformation buffer tank can be integrated and only separated by side walls, or they can be independent tanks. The deformation buffer tank is sealed before and after laying, and the potting tank is provided with a glue filling opening before embedding. There is an opening in the middle of the outer wall facing the deformation buffer tank and the potting tank. The size of the hole is just enough to allow the armored wire to pass through, and the armored wire can enter and exit freely at the hole to ensure that the test ring can expand with the test part when the road is rolled. The length of the armored wire stretching into the deformation buffer tank will ensure that the armored wire remains in the deformation buffer tank after the road surface is rolled. A small opening is reserved in the middle of the side wall separating the deformation buffer tank and the potting tank. The hole size is only to allow the optical fiber to pass through. The inner wall of the hole can be glued with a rubber layer to prevent the potting glue in the potting tank from flowing into the deformation buffer tank.

The measurement radius of the on-site radial strain test sensor for asphalt pavement can be changed according to requirements. Multiple sensors can be arranged along different depths and different radii at the same test site to measure the strain field distribution. The radial strain can be obtained according to the following formula.

ε _r = ε/(2π)

In the formula, ε _r represents the radial strain at the measuring point, and ε represents the strain value measured by the grating.

Claims (5)

1. a kind of Bituminous Pavement radial strain test sensor based on optical fiber sensing technology, including bare optical fibers and bare optical gratings, armour Dress protective wire, controller for profile, embedding groove, single-ended fixed block, deformation buffer groove, thermal insulation layer and sealing valve system；Bare fibre light Grid are as deformation sensitive element；Sealing valve system includes control line, sealing gasket and every big envelope；It is characterized in that：By bare fibre Grating or plus the fiber grating of casing protection penetrate the armoury wire as measurement part it is ensured that grating is always positioned at annular test section Domain；One end lead-out wire of fiber grating is fixed in embedding groove by single-ended fixed block, and the other end of fiber grating passes as signal Defeated section be previously threaded through sealing valve system in embedding groove every jacket portion, then pass through the pre- of deformation buffer groove and embedding groove two ends Box out；Sealing valve system is fixed on inside embedding groove in the sealing gasket low viscosity glue in embedding groove before burying by sensor, position Another sealing gasket outside embedding groove is close to embedding cell wall it is ensured that by the preformed hole sealing of embedding groove outer end, casting glue is not from filling Flow out in the preformed hole of sealing groove；The control line that sealing valve system is located at outside embedding groove draws pavement structure by independent armouring protective wire Or control line is caused through same armouring protective wire together with optical fiber transmission line and is connected demodulation instrument point；Embedding groove top is provided with filling Jiao Kou；Set, outside embedding groove and deformation buffer groove, the thermal insulation layer being made up of heat-barrier material；Casting glue is poured into when burying by sensor Embedding groove, seals embedding groove and thermal insulation layer afterwards；After completing the normal decking and rolling of pavement structure, tension grating simultaneously passes outside Temporarily fix for defeated section；Pull the control line of sealing valve system, the optical fiber in embedding groove departs from every big envelope and casting glue directly contact； After casting glue is fully achieved rigidity, remove the temporary transient fixation of optical fiber.

2. a kind of Bituminous Pavement radial strain test sensing based on optical fiber sensing technology according to claim 1 Device it is characterised in that：Lay the ring disposition shape controlling test section armouring protective wire during sensor by controller for profile, pass Sensor measurement radius is adjustable, continuously lays sensor loading at dot center's different radii.

3. a kind of Bituminous Pavement radial strain test based on optical fiber sensing technology according to claim 1 and 2 passes Sensor it is characterised in that：Deformation buffer groove lay before and after be sealing, with embedding groove just to outer wall in the middle part of be provided with opening, hole Footpath size is just to allow armoury wire to pass through, and armouring protective wire frees in and out it is ensured that test circle can when road surface is rolled in Kong Chu Expand with part of detecting, stretch into the armoury wire of deformation buffer groove length to ensure road surface roll finish after be still to armoury wire and stayed Inside deformation buffer groove.

4. a kind of Bituminous Pavement radial strain test based on optical fiber sensing technology according to claim 1 and 2 passes Sensor it is characterised in that：Single-ended fixed block adopts fiber-reinforced plastic, epoxide resin material or metal material to constitute；Casting glue It is made up of low viscosity epoxy resin material；Sealing valve system control line is made up of the little plastic cord of tinsel or deformation；Sealing valve System is made up of flexible plastic or elastomeric material every big envelope；Sealing valve system sealing gasket is made up of flexible plastic or elastomeric material；Embedding Groove adopts metal material or fiber-reinforced plastic to constitute；Controller for profile is cylinder or annulus, does not limit material.

5. a kind of Bituminous Pavement radial strain test sensing based on optical fiber sensing technology according to claim 3 Device it is characterised in that：Single-ended fixed block adopts fiber-reinforced plastic, epoxide resin material or metal material to constitute；Casting glue by Low viscosity epoxy resin material is constituted；Sealing valve system control line is made up of the little plastic cord of tinsel or deformation；Sealing valve system System is made up of flexible plastic or elastomeric material every big envelope；Sealing valve system sealing gasket is made up of flexible plastic or elastomeric material；Embedding groove Constituted using metal material or fiber-reinforced plastic；Controller for profile is cylinder or annulus, does not limit material.