Device for measuring large strain of semi-rigid base of highway asphalt pavement

Abstract

The utility model discloses a device for measuring the large strain of a semi-rigid base of a highway asphalt pavement. The device comprises a vibrating wire strain gauge, a PVC pipe, a steel plate, a heat preservation device, a steel string and a metal rod which is attached to the PVC pipe and used for enhancing the stability. The length of the PVC pipe is 1-2m, and the PVC pipe is used for protecting the strain gauge; the steel plates are respectively fixed at two ports of the PVC pipe and are used for sensing strain stress; one end of the string wire is connected with the strain gauge, and the other end is fixed with the steel plate. According to the invention, on one hand, the strain monitoring length is increased, the strain monitoring length is 1-2m, long gauge length strain monitoring is realized, and the strain monitoring cost of asphalt pavements and the like is reduced; on the other hand, even if the semi-rigid base cracks due to temperature and load changes, monitoring can be achieved, and more reliable data are provided for evaluating the crack range of the semi-rigid base of the asphalt pavement and early warning cracks.

Description

Technical Field

[0001] The invention belongs to the field of road engineering, and in particular relates to a device for measuring large strain of a semi-rigid base layer of an asphalt pavement of a highway. Background Art

[0002] With the vigorous development of my country's transportation industry, more and more new highways are being built. Correspondingly, many built highways have gradually entered the monitoring, maintenance and repair stage. The application of vibrating wire strain gauges in the engineering field is generally used to measure the strain of buildings, and then perform corresponding mechanical calculations to obtain the stress distribution of buildings and force analysis, etc., in order to achieve the purpose of understanding the stress distribution of buildings. The specific principle is as follows: When the stress inside the measured structure changes, the strain gauge synchronously senses the deformation, and the deformation is transmitted to the vibrating wire through the front and rear end seats and converted into a change in the stress of the vibrating wire, thereby changing the vibration frequency of the vibrating wire. The frequency signal is transmitted to the reading device via a cable, and the strain inside the measured structure can be measured. At present, strain gauges are also gradually used for road strain monitoring.

[0003] The semi-rigid base of asphalt pavement often produces reflective cracks due to the effects of temperature and vehicle load. However, due to the unevenness of the semi-rigid base of the pavement, the current methods, whether strain gauges or sensors, have too small a test range and cannot truly reflect the strain of the semi-rigid base of the pavement under the influence of temperature and load. In addition, strain gauges and sensors are greatly affected by the surrounding environment, and will cause errors in the measurement data due to the influence of impurities. The use of strain gauges on pavement also has defects: the existing vibrating wire strain gauge has a measurement range of only about 250mm, which cannot meet the needs of pavement testing well and will also increase monitoring costs. In addition, since it is buried in the water-influent stabilizing layer, it will be subjected to the load from the vehicle, so there is no good protection device.

[0004] In summary, how to design a device with a long monitoring distance and protective device for measuring the large strain of the semi-rigid base of highway asphalt pavement is of great significance to reducing the monitoring cost and improving the reliability of monitoring data. Summary of the invention

[0005] In view of this, the present invention provides a device for measuring the large strain of the semi-rigid base of the highway asphalt pavement, and its strain monitoring distance can reach about 2m, which is of great significance for long-distance monitoring of cracking of the semi-rigid base of the asphalt pavement.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The invention discloses a device for measuring large strain of semi-rigid base of highway asphalt pavement, comprising a vibrating wire strain gauge, a PVC pipe, a steel plate, a heat preservation device, a steel wire and metal rods evenly distributed on the PVC pipe for enhancing stability.

[0008] In a preferred embodiment of the present invention, the strain gauge body includes a steel string, flanges fixed at both ends of the steel string, and a bellows for protecting the steel string; the strain gauge body also includes a temperature sensor disposed in the bellows and an electromagnetic coil sleeved in the middle of the steel string, and the middle of the bellows has an outer sleeve that matches the electromagnetic coil. In addition, during actual installation, the signal cables of the electromagnetic coil and the temperature sensor can be integrated into one bundle or can be separately provided.

[0009] In a preferred embodiment of the present invention, a connecting sleeve is provided on one end surface of each flange, and the ends of the bellows are respectively fixedly inserted in the connecting sleeve to achieve fixed installation of the bellows.

[0010] More preferably, metal rods with a length of 10 cm are evenly distributed on the surface of the PVC pipe to achieve overall stability after the device is buried in the water-stabilizing layer.

[0011] More preferably, the metal rod may be made of iron rod, aluminum rod or copper rod.

[0012] More preferably, the steel plate is a 25×25 cm rectangular steel plate with a 2-3 cm thick steel ring welded on one side, and the size of the steel ring can just fit the PVC pipe in. The steel plate senses the stress and strain from the semi-rigid base and transmits it to the strain gauge through the steel string.

[0013] The beneficial effect of adopting this solution is that the 2-3 cm thick steel ring on the steel plate can allow the PVC pipe to have a certain deformation space and slide due to deformation.

[0014] More preferably, a rubber ring is embedded in the steel ring to increase friction to fix the PVC tube, so that the PVC tube and the steel plate form a sealed space.

[0015] More preferably, the steel chord is in an umbrella frame structure, one end of which is welded and fixed to the flange, and the other end of which is welded and fixed to the steel plate. The number of steel chords welded to each flange is 4.

[0016] The beneficial effect of adopting this solution is that the steel plate and the strain gauge are connected by the steel string so that the influence of the bending moment of the strain gauge can be omitted during the measurement process, and only the length measurement is focused.

[0017] More preferably, the PVC pipe should have a cable outlet hole for the strain gauge signal transmission cable to pass through.

[0018] More preferably, in order to reduce the influence of temperature factors on the steel string, a layer of rubber-plastic tube is nested in the PVC tube for heat insulation.

[0019] More preferably, since the device is buried in a water-stable layer and has been insulated, in order to accurately measure the temperature change of the environment, temperature compensation is performed: first test the measurement value of the ambient temperature of the strain gauge with an insulation device at normal temperature (such as a constant temperature of 20°C) (1), and then subtract this measurement value (1) from the temperature data measured after being buried in the water-stable layer to obtain a more accurate temperature.

[0020] Compared with the prior art, the present invention has the following advantages: the present invention protects the strain gauge from being damaged by vehicle load by inserting the strain gauge into a 1-2m long PVC pipe. On the other hand, steel plates are fixed at both ends of the PVC pipe to sense the stress and strain of the semi-rigid base layer, thereby lengthening the effective strain length, realizing long-gauge strain monitoring, and greatly reducing the strain monitoring cost of the road surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the present invention.

[0022] Figure 2 It is an enlarged view of the strain gauge body of the present invention.

[0023] Figure 3 It is a front view of the steel ring structure of the present invention.

[0024] In the accompanying drawings, the technical features represented by the reference numerals are as follows:

[0025] 101—steel plate; 102—connecting steel string; 103A—front flange; 103B—rear flange; 104—bellows; 105—temperature sensor; 106—outer casing; 107—electromagnetic coil; 108—strain gauge steel string; 109—cable; 110—connecting sleeve; 111—rubber-plastic tube; 112—PVC tube; 113—metal rod; 114—steel ring; 301—rubber ring. DETAILED DESCRIPTION

[0026] The following is a detailed description of an embodiment of the present invention in conjunction with the accompanying drawings. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0027] In the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" that may appear should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] The present invention provides a device for measuring large strain of semi-rigid base of highway asphalt pavement. On the one hand, it protects the strain gauge from being damaged by vehicle load. On the other hand, it increases the strain monitoring length, which is 8 times the effective length (250mm) of the existing commercially available strain gauge, realizes long gauge length strain monitoring, and greatly reduces the strain monitoring cost of the road surface.

[0029] Specifically, combined Figure 1 It can be seen that the device for measuring the large strain of the semi-rigid base of highway asphalt pavement described in the present invention includes a strain gauge body, a PVC pipe 112 for protecting the strain gauge and a metal rod 113 attached to the PVC pipe; a steel plate 101 for sensing stress changes and temperature changes, a rubber-plastic pipe 111 for insulating the working environment of the strain gauge in the pipe, a steel string 102 connecting the flange and the steel plate, and a steel ring 114 welded to the steel plate.

[0030] When in use, the present invention is buried in the water-stable layer, the metal rod 113 can be in full contact with the filler to ensure the overall stability of the device, and the rubber-plastic tube 111 is nested in the PVC tube 112 for heat preservation to reduce the influence of temperature on the steel string. The cable of the temperature sensor 105 and the electromagnetic coil 107 extends outward through the reserved opening on the PVC tube 112. The effective strain monitoring length of the present invention is about 2m. Compared with the current method for monitoring the cracking of the semi-rigid base, the test range of both the strain gauge and the sensor is small, and the data will be affected by the surrounding environment (such as gravel and stones stuck around the instrument), which will cause errors in the data and cannot truly reflect the strain of the semi-rigid base of the road surface under the influence of temperature and load. Taking the strain monitoring of a 4m road surface as an example, the measurement of the existing commercially available strain gauges is generally within 250mm, and 16 instruments are required to realize the strain monitoring of a 4m building; the effective strain length of the strain gauge of the present invention is 2m, and only 2 strain gauges of the present invention are needed to realize the strain monitoring of the semi-rigid base of the 4m road surface, which greatly reduces the monitoring cost.

[0031] Combination Figure 2It can be seen that the strain gauge body includes a steel string 108, a flange 103 fixed at both ends of the steel string 108, a bellows 104 for protecting the steel string 108, a temperature sensor 105 and an electromagnetic coil 107 sleeved in the middle of the steel string 108, the middle of the bellows 104 has an outer sleeve 106 that matches the electromagnetic coil 107, the temperature sensor 105 and the electromagnetic coil 107 are located in the outer sleeve 106, and the cables of the electromagnetic coil 107 and the temperature sensor 105 extend out of the bellows 104 and the PVC pipe 112. When in use, when the stress of the semi-rigid base changes, the strain gauge body is transmitted to the vibrating string 108 in the bellows through the steel plate 101, the steel string 102 and the flange 103 and converted into a change in the stress of the vibrating string, thereby changing the vibration frequency of the vibrating string. The electromagnetic coil 107 excites the vibrating string 108 and measures its vibration frequency. The frequency signal is transmitted to the strain gauge through the cable to obtain the strain amount, and the temperature of the environment in which the present invention is located is measured by the temperature sensor 105.

[0032] During the actual installation, the electromagnetic coil 107 is wound and fixed in the outer casing 106, and the temperature sensor 105 is suspended outside the electromagnetic coil 107 to ensure the normal operation of the electromagnetic coil. The cables 109 of the electromagnetic coil 107 and the temperature sensor 105 are integrated into a bundle and led out from the reserved opening of the PVC tube 112. A 2-3 cm thick steel ring 114 is welded on one side of the steel plate 101, and the size of the steel ring 114 can just fit the PVC tube 112. A rubber ring 301 is embedded in the steel ring 114 to increase the friction to fix the PVC tube 112, so that the PVC tube 112 and the steel plate 101 form a sealed space.

[0033] Combination Figure 2 It can be seen that a connection sleeve 110 is provided on one end face of each flange 103, and the connection sleeves 110 on the two flanges 103 are arranged front and back oppositely, and the two ends of the bellows 104 are respectively inserted into the connection sleeves 110 on the flanges 103, thereby realizing the fixed installation of the bellows 104. In addition, for the convenience of distinction, the front flange 103 is recorded as flange 103A, and the rear flange 103 is recorded as flange 103B. The flange 103A is welded to the four steel strings 102, and the flange 103B is welded to the other four steel strings 102.

[0034] During strain monitoring, the present invention is buried in the water-stable layer, and then the cable is led out from the reserved opening of the PVC pipe 112 and connected to the strain gauge to perform strain monitoring.

[0035] In actual processing, PVC pipes can be selected from high-strength, high-toughness, high-impact, and anti-fatigue PVC-O pipes to minimize damage caused by vehicle loads, thereby protecting the strain gauge. The bellows are made of stainless steel bellows, and both ends are sealed and inserted into the connecting sleeve of the flange. The connection is welded with low-stress laser to ensure its internal sealing and extend the working life of the strain gauge body in harsh environments. Rubber and plastic pipes are used for insulation to insulate the environment inside the PVC pipe, reduce the impact of temperature on the steel string, and reduce data errors.

[0036] Finally, it should be emphasized that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments without creative work, or replace some of the technical features therein with equivalents. Therefore, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A device for measuring large strain of semi-rigid base of highway asphalt pavement, characterized by: It includes a strain gauge body, a PVC pipe for protecting the strain gauge and a metal rod attached to the PVC pipe for enhancing stability; a steel plate, a heat preservation device and a steel string for sensing stress changes and temperature changes, wherein the heat preservation device is a rubber-plastic pipe embedded in the PVC pipe, the steel plate is located at the two outermost ends of the device, the steel string is used to connect the steel plate and the strain gauge, and the steel plate and the steel string are welded; the length of the PVC pipe is 1 to 2 meters.

2. The device for measuring large strain of semi-rigid base of highway asphalt pavement according to claim 1 is characterized by: The strain gauge body includes a steel string, flanges fixed at both ends of the steel string, and a bellows for protecting the steel string; the strain gauge body also includes a temperature sensor arranged in the bellows and an electromagnetic coil sleeved in the middle of the steel string, and the middle of the bellows has an outer protective sleeve that cooperates with the electromagnetic coil.

3. The device for measuring large strain of semi-rigid base of highway asphalt pavement according to claim 1 is characterized by: The surface of the PVC tube is attached with evenly distributed metal rods, each of which has a length of 10 cm.

4. The device for measuring large strain of semi-rigid base of highway asphalt pavement according to claim 1 is characterized by: The steel plate is a rectangular steel plate of 25×25 cm, with a 2-3 cm thick steel ring welded on one side. The size of the steel ring can allow the PVC pipe to be just embedded.

5. The device for measuring large strain of semi-rigid base of highway asphalt pavement according to claim 4 is characterized in that: A rubber ring is embedded in the steel ring to increase friction to fix the PVC pipe so that the PVC pipe and the steel plate form a sealed space.

6. The device for measuring large strain of semi-rigid base of highway asphalt pavement according to claim 2 is characterized by: The steel chord is in an umbrella frame structure, one end of which is fixed to the flange, and the other end of which is fixed to the steel plate.

7. The device for measuring large strain of semi-rigid base of highway asphalt pavement according to claim 6 is characterized by: The steel chords, the flange and the steel plate are fixed by welding, and the number of steel chords on each side of the PVC pipe is 4.

8. A device for measuring large strain of semi-rigid base of highway asphalt pavement according to claim 1 or 3, characterized in that: The PVC pipe should have a cable outlet hole for the strain gauge signal transmission cable to pass through.

9. The device for measuring large strain of semi-rigid base of highway asphalt pavement according to claim 3 is characterized by: The metal rod is made of iron rod, aluminum rod or copper rod.

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