Testing device for interlaminar shear performance of asphalt pavement

Abstract

The utility model discloses a bituminous pavement interlayer shear performance testing device, which comprises a loading machine, a loading pressure head, a shear clamp, a horizontal loading device, a vertical loading device and a test piece propelling and fixing device, the upper part of the loading machine comprises a horizontal test piece feeding hole, the horizontal loading device and the vertical loading device are positioned at one end of the test piece feeding hole, and the horizontal loading device and the vertical loading device are positioned at the other end of the test piece feeding hole. The test piece pushing and fixing device is located at the other end of the test piece feeding hole, the horizontal loading device translates towards the test piece in a large range through a hydraulic telescopic rod, the loading pressure head slightly moves towards the test piece, and the shearing clamp is installed on the vertical loading device and located between the test piece feeding hole and the loading pressure head; a shearing hole is formed in the shearing clamp, and the test piece pushing and fixing device pushes the test piece into the shearing hole and fixes the test piece together with the loading pressure head and the gasket. According to the utility model, the output periodic load of the vertical loading device is considered, and the device has the advantages of strong applicability, reliable experimental result, capability of simulating the interlayer shear failure of the asphalt pavement and consideration of the interlayer shear fatigue performance.

Description

Technical Field

[0001] The utility model belongs to the technical field of road detection, in particular to a testing device for the interlayer shearing performance of an asphalt pavement. Background Art

[0002] Asphalt pavements are widely used due to their excellent road performance. However, vehicles often generate horizontal loads within the pavement structure on sections with small radii, steep longitudinal slopes, and acceleration and braking zones. During these conditions, interlayer tangential shear stress can increase several times compared to typical sections. Insufficient interlayer adhesion can easily lead to pavement defects such as horizontal slippage, rutting, and bumping. Consequently, some specifications are beginning to consider interlayer interactions in design, and research on interlayer shear performance is becoming increasingly important.

[0003] In recent years, the focus on highways has shifted from "construction first" to "equal emphasis on construction, management, and maintenance." Thin overlays, used as preventative maintenance, have become increasingly common, posing a greater challenge to interlayer shear resistance. Furthermore, with the increasing number of vehicles on the road, asphalt pavements face increased traffic volume, exacerbating fatigue damage. Thin overlays are susceptible to shear fatigue failure under prolonged, repetitive loads.

[0004] Existing patents either only consider the shear resistance between asphalt pavement layers without considering the pressure perpendicular to the pavement surface, or consider the pressure perpendicular to the pavement surface without considering the shear fatigue between pavement layers under the repeated action of vehicle loads. Currently, there are few devices for testing the shear strength of thin overlays, and the existing devices have many limitations. For example, the experimental devices do not consider friction, resulting in large data dispersion, the devices themselves cannot be adjusted for test specimens, and test specimens can only be prepared in the laboratory, resulting in a limited scope of application. Utility Model Content

[0005] Therefore, in view of the defects of the test devices in the prior art, such as most of them not considering the shear fatigue damage between asphalt pavement layers or not considering the insufficiency of interlayer shear under the pressure of vertical road surface, the existing test devices for testing shear strength are improved; thereby, the present invention realizes the applicability to asphalt pavements of different thicknesses (including thin-layer overlays), and the vertical loading device outputs periodic loads to simulate the shear fatigue damage of the road surface under long-term repeated loads, thereby greatly improving the reliability of experimental data and the applicability of the experimental device.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A test device for interlayer shear performance of asphalt pavement, comprising a loading machine, a loading pressure head, a shear fixture, a horizontal loading device, a vertical loading device, a specimen advancing and fixing device, and a gasket;

[0008] The upper part of the loader includes a horizontal specimen feeding hole, the horizontal loading device and the vertical loading device are located at one end of the specimen feeding hole, and the specimen pushing and fixing device is located at the other end of the specimen feeding hole;

[0009] The horizontal loading device is connected to the upper part of the loading machine through a hydraulic telescopic rod, and the loading pressure head is installed on the side of the horizontal loading device facing the specimen feeding hole. When the horizontal loading device moves toward the specimen feeding hole, the loading pressure head (2) moves slightly toward the specimen feeding hole.

[0010] The shearing fixture is installed on the vertical loading device, which is located between the upper part of the loader and the loading pressure head; the vertical loading device is connected to the lower part of the loader, and the shearing fixture has a shearing hole;

[0011] The specimen feed hole, shear hole and loading pressure head are on the same horizontal line.

[0012] As a further preferred solution, the specimen advancing and fixing device includes a fixed pressing plate and serrated guide rods connected on both sides of the fixed pressing plate and a smooth guide rod connected at the bottom. A guide groove for inserting the serrated guide rod and the smooth guide rod is provided on the loader side corresponding to the specimen advancing and fixing device, and the upper surface of the serrated guide rod has right-angle teeth; a limit sleeve is provided on the loader above the serrated guide rod, a fixed magnet is provided above the limit sleeve, and a pin is provided inside the limit sleeve, and the pin slides up and is fixed by the fixed magnet or slides down to clamp the serrated guide rod to select a state;

[0013] The fixed pressing plate and the serrated guide rods on both sides and the smooth guide rod at the bottom form a space for loading the specimen. The fixed pressing plate presses the specimen into the specimen feeding hole along the guide groove through the serrated guide rods and the smooth guide rod.

[0014] As a further preferred solution, rollers are distributed on the side of the loading head facing the test piece, and the rolling direction of the rollers is longitudinal.

[0015] As a further preferred solution, a gasket is sandwiched between the loading head and the test piece, and the size and shape of the gasket are similar to the contact surface of the test piece.

[0016] As a further preferred solution, the loading machine is provided with a control system for operating the horizontal loading device, the vertical loading device, and the loading pressure head. The control system controls the vertical loading device to output loads with sinusoidal, triangular, rectangular, and inclined wave test waveforms. The display screen of the control system outputs the shear force-displacement curve, shear strength, and friction coefficient of the specimen during the experiment.

[0017] As a further preferred solution, the outer side of the fixed pressing piece is provided with a fixed handle for manual pushing and pulling.

[0018] This utility model directly conducts shear tests or shear fatigue tests on laboratory specimens or field core samples. Its beneficial effects include reducing friction between the indenter and the specimen surface, enhancing the regularity of experimental data, allowing for adjustable positions of both the fixed pressing plate and the loader's horizontal loading device, thus expanding the test apparatus's applicability, and enabling the application of a regular, reciprocating shear load. This provides a scientific and reliable testing method for studying interlayer shear mechanics, evaluating the combined performance of asphalt pavement structures, estimating the interlayer shear performance of existing asphalt pavements, and guiding the selection of tack coat oils. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the three-dimensional structure of the device of the utility model;

[0020] Figure 2 This is a schematic diagram of the structure of the specimen pushing fixture;

[0021] Figure 3 is a structural diagram of the loading head;

[0022] Figure 4 It is a side view of the device of the utility model;

[0023] Figure 5 It is a top view of the device of the utility model;

[0024] Among them, 1. Loading machine; 11. Horizontal loading device; 12. Vertical loading device; 13. Hydraulic telescopic rod; 14. Guide groove; 15. Control system; 16. Sample fixing hole; 17. Fixed magnet; 18. Pin; 2. Loading pressure head; 21. Roller; 3. Shearing clamp; 4. Fixed pressure plate; 41. Fixed handle; 42. Serrated guide rod; 43. Smooth guide rod; 5. Gasket. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0026] The utility model discloses a test device for the interlayer shear performance of an asphalt pavement, comprising a loading machine 1, a loading pressure head 2, a shearing fixture 3, a horizontal loading device 11, a vertical loading device 12, and a test piece advancing and fixing device;

[0027] The upper part of the loader 1 includes a horizontal specimen feeding hole 16, the horizontal loading device 11 and the vertical loading device 12 are located at one end of the specimen feeding hole 16, and the specimen pushing and fixing device is located at the other end of the specimen feeding hole 16; the horizontal loading device 11 provides horizontal pressure, and the vertical loading device 12 provides vertical thrust, which act together on the specimen. The specimen pushing and fixing device pushes the specimen into the loader 1, feeds it to the horizontal loading device 11 and the vertical loading device 12, and fixes it to serve as a fixed backrest for the horizontal thrust.

[0028] The horizontal loading device 11 is connected to the upper part of the loading machine 1 through a hydraulic telescopic rod 13. The loading head 2 is installed on the side of the horizontal loading device 11 facing the specimen feed hole 16. The horizontal loading device 11 is displaced toward the specimen feed hole 16, and moves a large range to the end of the specimen. The loading head 2 moves slightly toward the specimen feed hole 16, giving the specimen a certain horizontal loading force.

[0029] The hydraulic telescopic rod and fixed pressure piece design are helpful to adjust the shear position of the cylindrical specimen, making the device more applicable.

[0030] The shearing fixture 3 is installed on the vertical loading device 12, and the vertical loading device 12 is located between the upper part of the loader 1 and the loading head 2; the vertical loading device 12 is connected to the lower part of the loader 1, and there is a shear hole in the shearing fixture 3. The specimen is positioned in the shear hole, one end of which is supported by the specimen pushing fixture, and the other end of which is given a certain horizontal loading force by the loading head 2. The vertical loading device 12 pushes the shearing fixture 3 to give a thrust in the longitudinal direction to realize the test of the shear performance of the specimen.

[0031] Considering the convenience of specimen preparation, specimens can be obtained by drilling core samples on actual pavement or preparing them in the laboratory.

[0032] Specifically, the specimen pushing fixture includes a fixed pressing plate 4, a serrated guide rod 42 connected to both sides of the fixed pressing plate 4, and a smooth guide rod 43 connected to the bottom. The loader 1 side corresponding to the specimen pushing fixture is provided with a guide groove 14 for inserting the serrated guide rod 42 and the smooth guide rod 43. The upper surface of the serrated guide rod 42 has right-angle teeth.

[0033] The fixed pressing plate 4 and the serrated guide rods 42 on both sides and the smooth guide rod 43 at the bottom form a space for loading the specimen. The fixed pressing plate 4 presses the specimen into the specimen feed hole 16 along the guide groove 14 through the serrated guide rods 42 and the smooth guide rod 43. The fixed pressing plate 4 serves as a fixed back seat on one side of the specimen, and is used to fix the specimen after inserting it into the specimen feed hole 16, and to support the specimen in the horizontal direction.

[0034] The outer side of the fixed pressing piece 4 is provided with a fixed handle 41 for manual pushing and pulling.

[0035] A limiting sleeve is provided on the loader 1 above the serrated guide rod 42. A fixed magnet 17 is provided above the limiting sleeve, and a latch 18 is provided inside the limiting sleeve. The latch 18 slides up and is fixed by the fixed magnet 17, or slides down and clamps the serrated guide rod 42. This is a state that is manually operated. The latch 18 cooperates with the right-angle teeth of the serrated guide rod 42 to more stably position the fixed pressing plate 4 and enhance the resistance function to the specimen.

[0036] Taking into account the frictional resistance between the shear slip part and the device, a roller is designed at the pressure head and a gasket is added during the experiment, so that the experimental data results are more reliable and stable; specifically, a roller 21 is distributed on the side of the loading pressure head 2 facing the specimen, and the rolling direction of the roller 21 is longitudinal. The roller 21 reduces the friction between the pressure head and the surface of the specimen, making the experimental data more regular; a gasket 5 is sandwiched between the loading pressure head 2 and the specimen. The size and shape of the gasket 5 are similar to the contact surface of the specimen, which reduces the excessive local pressure on the specimen at the roller 21.

[0037] Preferably, the gasket 5, the shearing fixture 3, the sample fixing hole 16, and the fixing pressing plate 4 are all cylindrical in structure and have the same diameter;

[0038] Preferably, the fixing magnet 17 can fix the latch 18 by magnetic attraction, and the latch 18 is made of iron or has magnetism.

[0039] The loading machine 1 has a control system 15 for controlling the horizontal loading device 11, the vertical loading device 12, and the loading pressure head 2, that is, the control system 15 can control the extension or shortening of the hydraulic telescopic rod 13; the control system 15 can control the horizontal loading device 11 to apply a constant pressure in the horizontal direction to the specimen; the control system 15 can control the vertical loading device 12 to output loads with test waveforms such as sine waves, triangular waves, rectangular waves, and inclined waves; the display screen of the control system 15 can output the shear force-displacement curve, shear strength, and friction coefficient of the specimen during the experiment.

[0040] In the present invention, the movement of the horizontal loading device 11, the vertical loading device 12, and the loading pressure head 2 are all controlled by the hydraulic system, and the driving principle thereof will not be described in detail.

[0041] The utility model has the advantages of strong applicability, reliable experimental results, ability to simulate interlayer shear failure of asphalt pavement, consideration of interlayer shear fatigue performance, and consideration of the output of cyclic load by the vertical loading device. Example 1

[0042] The asphalt pavement shear strength test device introduced in this case is mainly used for testing the interlayer shear strength of asphalt pavement and thin overlay. It includes:

[0043] Composite specimens are prepared experimentally or obtained by on-site coring. The diameter of the cylindrical specimen is 100mm, the upper layer is asphalt mixture, and the thickness is 10-60mm. The material below is not limited, but the thickness of the remaining part does not exceed 200mm.

[0044] Loading machine, after the horizontal loading device on the loading machine moves to the end position of the specimen, drive the loading pressure head 2 to adjust the horizontal pressure on the specimen (0-0.4MPa) as needed, and generate a constant pressure on the specimen that does not change with time. Before the experiment begins, the loading pressure head needs to be installed on the horizontal loading device, and ensure that the roller surface is vertical and parallel to the surface where the horizontal loading device is located. The vertical loading device on the loading machine can apply experimental waveforms: sine wave, triangle wave, rectangular wave, inclined wave, etc. At the beginning, check the position of the shear clamp, and the circular hole and the specimen fixing hole of the loader should be aligned. Before the experiment starts, the fixed pressure plate guide rod can slide along the guide groove. If the fixed pressure plate needs to be fixed during the experiment, the fixed pressure plate can be fixed by manually lowering the pin.

[0045] Gasket, adjust the specimen to the appropriate position at the beginning of the experiment, place the gasket on the left surface of the specimen and make it contact with the surface of the loading head roller, and then adjust the hydraulic telescopic rod to completely fix its position.

[0046] During the experiment, the composite specimen was placed in the specimen fixing hole of the loader. By adjusting the thrust of the fixed pressure plate and the movement of the loader's hydraulic telescopic rod, the horizontal loading device 11 was moved so that the shear surface was located between the loader's specimen fixing hole and the vertical shear fixture (the specimen end was primarily located in the shear hole of the shear fixture 3). After the gasket was placed, the controller set the applied horizontal pressure and vertical shear force. After the fixed pressure plate 4 was fixed, the vertical loading device 12 adopted a displacement-controlled mode under the constant pressure of the loading head 2 (simulating the pressure of an asphalt pavement under vehicle pressure). After the experiment, the experimental output results can be viewed on the controller's display screen, including the shear displacement-shear force curve, shear strength (the peak of the shear displacement-shear force curve corresponds to the maximum shear force), and friction coefficient (the ratio of shear strength to normal load). Example 2

[0047] The device used in this case is the same as the previous case, but the experimental purpose is different. This case is to test the shear fatigue performance of the specimen.

[0048] During this experiment, the vertical loading device 12 applied loads intermittently and periodically (simulating the cyclical horizontal loads exerted by wheels on the asphalt pavement). A controlled stress mode and a sinusoidal loading pattern, more consistent with actual pavement failure, were used. The loading stress ratios were chosen to be 0.3, 0.4, 0.5, 0.7, and other stress levels. The stress levels and fatigue life in this experiment can be used as indicators for evaluating the shear fatigue performance of the test specimens.

[0049] The above is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited to this. Any technician familiar with the technical field within the technical scope disclosed by the present invention can make equivalent replacements or changes based on the technical solution and utility model concept of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A test device for the interlaminar shear performance of asphalt pavement, characterized by: It includes a loading machine (1), a loading head (2), a shearing fixture (3), a horizontal loading device (11), a vertical loading device (12), and a specimen pushing and fixing device; The upper portion of the loading machine (1) includes a horizontal specimen feeding hole (16), the horizontal loading device (11) and the vertical loading device (12) are located at one end of the specimen feeding hole (16), and the specimen pushing and fixing device is located at the other end of the specimen feeding hole (16); The horizontal loading device (11) is connected to the upper part of the loading machine (1) via a hydraulic telescopic rod (13), and the loading pressure head (2) is installed on the side of the horizontal loading device (11) facing the specimen feeding hole (16). When the horizontal loading device (11) moves toward the specimen feeding hole (16), the loading pressure head (2) slightly moves toward the specimen feeding hole (16); The shearing fixture (3) is mounted on a vertical loading device (12), and the vertical loading device (12) is located between the upper portion of the loading machine (1) and the loading pressure head (2); the vertical loading device (12) is connected to the lower portion of the loading machine (1), and a shearing hole is provided in the shearing fixture (3); The specimen feed hole (16), the shear hole, and the loading pressure head (2) are located on a horizontal line.

2. The test device for interlaminar shear performance of asphalt pavement according to claim 1, characterized in that: The specimen pushing fixture comprises a fixed pressing plate (4) and sawtooth guide rods (42) connected on both sides of the fixed pressing plate (4) and a smooth guide rod (43) connected at the bottom. A guide groove (14) for inserting the sawtooth guide rod (42) and the smooth guide rod (43) is provided on the side of the loader (1) corresponding to the specimen pushing fixture. The upper surface of the sawtooth guide rod (42) is a right-angle tooth. A limiting sleeve is provided on the loader (1) above the sawtooth guide rod (42). A fixed magnet (17) is provided above the limiting sleeve. A latch (18) is provided inside the limiting sleeve. The latch (18) slides up to be fixed by the fixed magnet (17) or slides down to clamp the sawtooth guide rod (42). The fixed pressing plate (4) and the serrated guide rods (42) on both sides and the smooth guide rod (43) at the bottom form a space for loading the specimen. The fixed pressing plate (4) presses the specimen into the specimen feeding hole (16) along the guide groove (14) through the serrated guide rods (42) and the smooth guide rod (43).

3. The test device for interlaminar shear performance of asphalt pavement according to claim 2, characterized in that: A roller (21) is distributed on one side of the loading pressure head (2) facing the test piece, and the rolling direction of the roller (21) is longitudinal.

4. The test device for interlaminar shear performance of asphalt pavement according to claim 3, characterized in that: A gasket (5) is sandwiched between the loading pressure head (2) and the test piece, and the size and shape of the gasket (5) are similar to those of the contact surface of the test piece.

5. The test device for interlaminar shear performance of asphalt pavement according to claim 2 or 4, characterized in that: The loading machine (1) is provided with a control system (15) for controlling a horizontal loading device (11), a vertical loading device (12), and a loading pressure head (2). The control system (15) controls the vertical loading device (12) to output a load of a sine wave, a triangle wave, a rectangular wave, or an inclined wave test waveform. The display screen of the control system (15) outputs a shear force-displacement curve, shear strength, and friction coefficient of the specimen during the experiment.

6. The test device for interlaminar shear performance of asphalt pavement according to claim 2, characterized in that: The outer side of the fixed pressing plate (4) is provided with a fixed handle (41) for manual pushing and pulling.

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