Top-down crack test device and method for asphalt overlay layer of rigid pavement

Abstract

The present invention discloses a top-down crack test device for an asphalt overlay layer on a rigid pavement, comprising a loading mechanism and a force-dividing mechanism for being placed on a test piece, wherein the loading mechanism is used to be connected to a pressurizing mechanism to press the force-dividing mechanism downward for testing; the force-dividing mechanism comprises more than two mounting rods, wherein a plurality of force plate assemblies are passed through the mounting rods from left to right, wherein elastic members are sleeved between two adjacent force plate assemblies on the mounting rods, and each force plate assembly comprises two force plates that are fitted together under the extrusion of the elastic members; the loading mechanism comprises a loading plate and a plurality of pressure heads fixed on the bottom surface of the loading plate, wherein the plurality of pressure heads correspond one to one with the positions of the plurality of force plate assemblies below. The present invention also discloses a test method based on the present device. The present invention has the advantages of simple and compact structure, easy installation and maintenance, accurate simulation of the stress conditions of the asphalt overlay layer on a rigid pavement during actual driving, and high test accuracy.

Description

Technical Field

[0001] The invention mainly relates to the field of road traffic tests, and in particular to a top-down crack test device for an asphalt overlay layer of a rigid road surface and a test method based on the device. Background Art

[0002] my country's road surfaces were severely damaged in the early stages, and the service life of the pavement structure is often lower than the designed life. There is an urgent need to improve the durability of road projects, promote faster and better development of my country's transportation industry, and help build a strong transportation country.

[0003] The asphalt overlay of the continuous reinforced concrete rigid pavement is a composite pavement with an asphalt concrete surface layer laid on the continuous reinforced concrete. It can fully meet the durability requirements of the pavement structure under heavy-load traffic conditions and is the main development form of long-life pavement structure for heavy-load traffic in my country. In engineering practice and preliminary research, it was found that the rutting depth of the asphalt overlay of the CRC+AC rigid pavement is relatively small, and the main disease is cracking of the asphalt surface layer. Top-Down cracks are also called top-down cracks. As a type of crack disease, they are mainly manifested as longitudinal cracks near the wheel track of the driving lane, as well as transverse cracks caused by frequent braking of vehicles at a few toll stations or intersections, and "U"-shaped push cracks on the surface of the climbing section.

[0004] As a durable pavement with high initial investment cost, the cracking behavior of the asphalt surface layer of CRC+AC rigid pavement will increase the maintenance cost and affect the service life of the asphalt surface layer, and even affect the durability of the CRC board if the cracking behavior of the asphalt surface layer cannot be effectively controlled. Therefore, a targeted test equipment and method is needed to study the top-down cracks and guide the design of the asphalt overlay pavement of CRC+AC rigid pavement.

[0005] Through repeated research and testing, it was found that under the action of vehicle load, the pavement structure is subjected to certain lateral and longitudinal horizontal forces in addition to the pressure perpendicular to the pavement structure. However, several test methods and test devices in the prior art cannot reflect the actual pavement stress conditions. For example, the published utility model patent (CN204177677 U) and invention patent (CN 104615891 A) on Top-Down cracks provide a test device and corresponding analysis method for Top-Down cracks. The test device and method are mainly aimed at flexible base pavements, and the device only directly simulates the tire track and simplifies it into a rectangle. The applied load is only vertical downward pressure, which is inconsistent with the situation that the pavement is subjected to lateral horizontal forces perpendicular to the driving direction, longitudinal horizontal forces opposite to the driving direction, and vertical pressure during driving. This results in inaccurate and inscientific test results, which affects the scientific design of CRC+AC pavement.

[0006] At the same time, since the top-down crack test of the asphalt overlay layer of the rigid pavement needs to be carried out multiple times, the equipment may be damaged during the test. Therefore, how to extend the service life of the equipment and how to quickly and conveniently replace and maintain the equipment is also a problem that needs to be solved urgently. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a top-down crack test device for an asphalt overlay layer on a rigid pavement, which has a simple and compact structure, is easy to install and maintain, can accurately simulate the stress conditions of an asphalt overlay layer on a rigid pavement during actual driving, and has high test accuracy. Two test methods based on the test device are also provided.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A top-down crack test device for an asphalt overlay layer of a rigid pavement comprises a loading mechanism and a force component mechanism placed on a test piece, wherein the loading mechanism is used to be connected to a pressurizing mechanism to press the force component mechanism downward for testing; the force component mechanism comprises more than two mounting rods, wherein a multi-component force plate assembly is passed through the mounting rods from left to right to simulate a wheel tread, wherein elastic members are sleeved between two adjacent force component plate assemblies on the mounting rods to arrange the multi-component force plate assemblies at intervals, wherein each group of the force component plate assemblies comprises two force component plates that are bonded together under the extrusion of the elastic members, and each force component plate assembly is provided with a plurality of elastic members. The top surfaces of the force component plates are all arranged in an inclined slope with a height at the front and a height at the back, and the top surface of each of the force component plates is arranged in an inclined slope in the left-right direction, so as to form a V-shaped groove on the top surface of each force component plate assembly; the loading mechanism includes a loading plate and a plurality of pressure heads fixed on the bottom surface of the loading plate, and the plurality of pressure heads correspond one by one to the positions of the multi-component force plate assemblies below, and the bottom surface of each of the pressure heads is arranged in an inclined slope with a height at the back and a V-shaped vertical cross section, so as to squeeze the top surface of the force component plate assembly when pressing down to convert the vertical force of the pressure head pressing down into the vertical force, longitudinal force and lateral force of the force component plate assembly on the specimen.

[0010] As a further improvement of the present invention, the two force distribution plates at the outermost ends of the mounting rod are fastened to the mounting rod through a fixing assembly so that the two force distribution plates do not move when pressed down. Each of the fixing assemblies includes an inner fixing nut and an outer fixing nut for clamping and fixing the force distribution plate to the mounting rod. The inner sides of the two force distribution plates are provided with recessed fixing holes for embedding and installing the inner fixing nuts.

[0011] As a further improvement of the present invention, the slope inclination angles in the front-to-back direction and the left-to-right direction of the top surface of each force component plate except the two outermost force components plates are both 11.31°, the slope inclination angles in the front-to-back direction and the left-to-right direction of the bottom surface of each pressure head are also both 11.31°, and the slope inclination angles in the left-to-right direction of the top surfaces of the two outermost force component plates are both less than 11.31°, so that the pressure head does not contact the two outermost force component plates when pressing down.

[0012] As a further improvement of the present invention, five groups of force plate assemblies are provided on the mounting rod to simulate the radial tire tread.

[0013] As a further improvement of the present invention, the spacing between two adjacent groups of force plate assemblies is 1 cm.

[0014] As a further improvement of the present invention, a rubber layer is provided on the bottom surface of each of the force distribution plates.

[0015] As a further improvement of the present invention, lubricating oil is coated on the bottom surface of the pressure head or the top surface of the force distribution plate.

[0016] As a further improvement of the present invention, a connecting rod is provided on the top surface of the loading plate to form a detachable connection with the pressurizing mechanism.

[0017] A method for testing the cracking of an asphalt overlay layer on a rigid pavement from top to bottom, using any of the test devices described above, and the steps are as follows:

[0018] Step 1), according to the test requirements, select the corresponding rigid pavement asphalt overlay block as the test piece, connect the loading mechanism and the pressure mechanism, place the force distribution mechanism on the test piece, and make the force distribution mechanism under the loading mechanism;

[0019] Step 2), start the pressurizing mechanism, so that the pressurizing mechanism drives the loading mechanism to press downward at a speed of 1.5-2.5 mm / min, so that the multiple pressing heads are pressed on the multiple force plate assemblies respectively, and the multiple force plate assemblies squeeze the test piece below;

[0020] Step 3), when the specimen is squeezed to produce cracks, the load value of the pressure mechanism at this time is recorded as the vertical force causing the specimen to crack, that is, the axle load causing the rigid pavement asphalt overlay layer to crack from top to bottom.

[0021] A method for testing fatigue cracks of an asphalt overlay layer on a rigid pavement from top to bottom, using any of the test devices described above, and the steps are as follows:

[0022] Step 1), according to the test requirements, select the corresponding rigid pavement asphalt overlay block as the test piece, connect the loading mechanism and the pressure mechanism, place the force distribution mechanism on the test piece, and make the force distribution mechanism under the loading mechanism;

[0023] Step 2), starting the pressurizing mechanism according to the axle load to be simulated and setting the test load, so that the pressurizing mechanism drives the loading mechanism to press down according to the test load, so that the multiple pressure heads are pressed on the multiple force plate assemblies respectively, and the multiple force plate assemblies squeeze the test piece below;

[0024] Step 3), after the downward pressure load reaches the test load, the pressure mechanism is lifted and loaded again, and the pressure is repeated until the specimen is destroyed. The maximum number of downward pressures when the specimen is destroyed is the fatigue cracking life of the asphalt overlay layer of the rigid pavement from top to bottom under the test load level.

[0025] Compared with the prior art, the advantages of the present invention are:

[0026] First, the top-down crack test device for the rigid pavement asphalt overlay layer of the present invention is designed with a loading mechanism and a force distribution mechanism of a special structure. During the test, the downward vertical force can be successfully converted into a vertical force, a longitudinal force and a lateral force on the test piece, thereby accurately simulating the stress condition of the rigid pavement asphalt overlay layer during actual driving, thereby achieving high test accuracy.

[0027] Second, the rigid pavement asphalt overlay crack test device of the present invention has a simple and compact structure, strong adaptability, can be quickly connected with the existing pressure mechanism and conduct tests, has low manufacturing cost, and is easy to promote and apply. In addition, this structure can facilitate the disassembly and replacement of various components. Once the device is damaged, the device parts can be replaced as needed, which reduces the maintenance cost.

[0028] Third, the top-down crack test device for the rigid pavement asphalt overlay layer of the present invention has protective and fixing measures for the two outermost force plates at the left and right ends. This is to ensure that the force distribution mechanism maintains the stability of the overall structure and does not cause large deformations such as tilting during extrusion, so as to ensure the normal displacement of other force distribution plates in the middle. By providing an internal fixing nut and an external fixing nut, the force distribution plate or elastic part can be quickly removed during maintenance, and the damaged force distribution plate or elastic part can be quickly replaced. At the same time, by providing a recessed fixing hole to embed the internal fixing nut, the internal fixing nut will not cause obstruction to the other adjacent force distribution plate.

[0029] Fourthly, the top-down crack test device for the rigid pavement asphalt overlay layer of the present invention, through repeated and multiple studies and tests, the special angle setting of 11.31°, combined with the aforementioned special structural setting, can optimally convert the vertical force into lateral horizontal force and longitudinal horizontal force during the test, thereby accurately simulating the stress condition of the rigid pavement asphalt overlay layer during actual driving.

[0030] Fifth, the top-down crack test device for the rigid pavement asphalt overlay layer of the present invention does not contact the two outermost force plates when the pressure head presses down, and can truly simulate the actual ground contact shape of an actual radial tire, effectively ensuring the test accuracy.

[0031] Sixth, the test method of the present invention can quickly obtain the numerical value of the axle load that causes the asphalt overlay layer of the rigid pavement to crack from top to bottom, as well as the numerical value of the fatigue cracking life of the asphalt overlay layer of the rigid pavement from top to bottom under the test load level, with high test efficiency and high test accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the structural principle of the test device of the present invention when used in conjunction with a pressurizing mechanism.

[0033] Figure 2 It is a schematic diagram of the three-dimensional structural principle when the test device of the present invention is pressed on the test piece.

[0034] Figure 3 yes Figure 2 Schematic diagram of the local enlarged structural principle.

[0035] Figure 4 It is a schematic diagram of the front view structural principle of the loading mechanism of the present invention.

[0036] Figure 5 It is a schematic diagram of the side structural principle of the loading mechanism of the present invention.

[0037] Figure 6 It is a schematic diagram of the three-dimensional structural principle of the loading mechanism of the present invention.

[0038] Figure 7 It is a schematic diagram of the front view structural principle of the force distribution mechanism of the present invention.

[0039] Figure 8 It is a schematic diagram of the side structural principle of the force distribution mechanism of the present invention.

[0040] Fig. 9 It is a schematic diagram of the top structural principle of the force distribution mechanism of the present invention.

[0041] Fig.10 It is a schematic diagram of the three-dimensional structural principle of the force distribution mechanism of the present invention.

[0042] The symbols in the figure represent:

[0043] 1. Loading mechanism; 11. Loading plate; 111. Connecting rod; 12. Pressure head; 2. Force distribution mechanism; 21. Mounting rod; 22. Force distribution plate assembly; 221. Force distribution plate; 23. Elastic member; 24. External fixing nut; 25. Internal fixing nut; 31. Control console; 32. Environmental chamber; 33. Pressurized driver; 34. Support platform. DETAILED DESCRIPTION

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] like Figures 1 to 10 As shown, the present invention provides a top-down crack test device for rigid pavement asphalt overlay, comprising a loading mechanism 1 and a force component 2 placed on a test piece, wherein the loading mechanism 1 is connected to a pressurizing mechanism to press the force component 2 downward for testing; in this embodiment, a material testing machine in the prior art is selected as the pressurizing mechanism, so that the test device has strong adaptability and can be directly applied to the equipment in the prior art. Figure 1 As shown, the material testing machine includes a control console 31, an environmental chamber 32, a pressure driver 33, and a support platform 34. The support platform 34 is in the environmental chamber 32, and the test piece is placed on the support platform 34. The control console 31 is connected to the pressure driver 33, and the control console 31 can input test data to control the pressure driver 33 to press downward.

[0046] It should be noted that the left-right, front-back, up-down and other directional descriptions in the present invention are described in accordance with the accompanying drawings in the specification so as to facilitate a correct understanding of the structural arrangement of the device. As shown in the accompanying drawings, arrows AB in the drawings represent the left-right direction, arrows CD represent the front-back direction, and arrows EF represent the up-down direction.

[0047] In this embodiment, the force distribution mechanism 2 includes more than two mounting rods 21, and a plurality of force plate components 22 are provided on the mounting rods 21 from left to right to simulate the tire tread (such as the attached Figures 7 to 10 As shown, there are five groups of force plate assemblies 22. The mounting rod 21 is provided with elastic members 23 between two adjacent force plate assemblies 22, so as to arrange the multiple force plate assemblies 22 in an interval manner. Each group of force plate assemblies 22 includes two force plates 221 that are pressed together by the elastic members 23. The top surface of each force plate 221 is arranged in an inclined slope with a high front and a low back. Figure 8 As shown, when viewed from the side, the force distribution plate 221 is like a right triangle, with a slope that is high in the front and low in the back. The top surface of each force distribution plate 221 is arranged as a slope that is inclined in the left and right directions, so that the top surface of each group of force distribution plate components 22 forms a V-shaped groove. Figure 7 As shown, there are five groups of force plate assemblies 22 in the figure. When looking at the force plate 221 from the front, its top surface also has a slope surface in the left and right directions. However, it should be noted that the top slope surfaces of the two force plates 221 of each group of force plate assemblies 22 are inclined in opposite directions. Only in this way can the top surface of the force plate assembly 22 form a V-shaped groove after the two force plates 221 are closely matched, that is, there are five groups of V-shaped grooves in the figure.

[0048] The loading mechanism 1 includes a loading plate 11 and a plurality of pressure heads 12 fixed on the bottom surface of the loading plate 11. The plurality of pressure heads 12 correspond one-to-one to the positions of the multi-group force plate assemblies 22 below, that is, there are as many pressure heads 12 as there are groups of force plate assemblies 22. The bottom surface of each pressure head 12 is arranged in an inclined slope with a low front and a high back, and a vertical cross-section in a V shape, which is used to compress the top surface of the force plate assembly 22 when pressing down to convert the vertical force of the pressure head 12 pressing down into the vertical force, longitudinal force and lateral force of the force plate assembly 22 on the specimen. That is, the shape of the pressure head 12 is exactly opposite to the force plate assembly 22 below. Figure 6 As shown, when viewed from the side, the pressure head 12 is like an inverted right triangle, with a slope surface that is low in the front and high in the back (while the force distribution plate 221 is high in the front and low in the back). And the vertical cross section of each pressure head 12 is V-shaped, that is, Figure 5 As shown in the figure, there are five pressing heads 12 in total. When viewed from the front, the vertical cross-section of each pressing head 12 is V-shaped, which just matches the V-shaped groove on the top surface of the force dividing plate assembly 22 below, so that the pressing head 12 can be pressed into the V-shaped groove.

[0049] The specific implementation principles are as follows:

[0050] Before the test, the base thickness, asphalt layer thickness and interlayer treatment method of the rigid-flexible composite specimen are selected according to the test requirements. Figure 1 M) is placed on the support platform 34. The force distribution mechanism 2 is placed on the specimen, and the loading mechanism 1 is connected to the driving rod of the pressure driver 33, and then the pressure driver 33 is controlled by the console 31 to press downward.

[0051] At this time, the pressure driver 33 drives the loading mechanism 1 to move downward, so that each pressure head 12 contacts and squeezes the force plate assembly 22 below. The force plate assembly 22 then squeezes and acts on the specimen below. When the specimen is cracked due to squeezing, the load value recorded by the material testing machine 3 at this time is the vertical force causing the specimen to crack, that is, the axle load causing the rigid road asphalt overlay layer to crack from top to bottom. The specific test method is described in detail below.

[0052] It should be emphasized that in the above-mentioned pressurizing process, since the bottom surface of each pressure head 12 is arranged to be low in the front and high in the back, and the top surface of each force component plate 221 is arranged to be high in the front and low in the back, the sliding coordination between the inclined slopes in the front-to-back direction and the inclined slopes makes the force component plate 221 slide in the front-to-back direction during the continuous pressing process of the pressure head 12. This sliding in the front-to-back direction can convert the vertical force of the pressure head 12 pressing down into the longitudinal force of the force component plate assembly 22 on the specimen. At the same time, since the vertical cross-section of each pressure head 12 is V-shaped (that is, it has an inclined slope in the left and right directions), and the top surface of each force distribution plate 221 is set with an inclined slope in the left and right directions, the sliding cooperation between the inclined slopes in the left and right directions makes the pressure head 12 slide in the left and right directions at the same time during the continuous downward pressure process (the force distribution plate 221 on the left side slides to the left, and the force distribution plate 221 on the right side slides to the right). This left and right sliding can convert the vertical force of the pressure head 12 into the lateral force of the force distribution plate assembly 22 on the specimen. In addition, the vertical force caused by the downward pressure of the pressure head 12 itself can be successfully converted into the vertical force, longitudinal force and lateral force of the force distribution plate assembly 22 on the specimen, thereby accurately simulating the stress condition of the rigid road asphalt overlay layer in actual driving, so that the test accuracy is high.

[0053] It should also be noted that, in this embodiment, the elastic member 23 is a spring sleeved on the mounting rod 21. The elastic member 23 has multiple special functions. First, the two force plates 221 of each group of force plate assemblies 22 must be set separately in order to achieve displacement in different directions of left and right, and the elastic member 23 is set to ensure that the force plates 221 of the same group are tightly fitted before loading and pressing, so that each group of force plate assemblies 22 are subjected to force at the same time when loading and pressing, ensuring scientificity and test accuracy. Second, since the test is repeated many times, after each pressing, under the action of the elastic member 23, the displaced force plate 221 can be quickly reset, which is convenient for the next loading and pressing. Third, the penetration limiting effect of the mounting rod 21 plus the extrusion fine-tuning effect of the elastic member 23 can limit the displacement of the force plate 221, ensuring that each displacement is scientifically controllable, rather than randomly displacing once pressed, thereby affecting the scientificity and test accuracy of the test. Of course, in other embodiments, other elastic members, such as rubber rings, silicone rings, etc., can also be set, which should all belong to the protection scope of the present invention.

[0054] Through the above special scientific design, it has the following technical advantages:

[0055] First, the top-down crack test device for the asphalt overlay layer of a rigid pavement of the present invention is designed with a loading mechanism 1 and a force distribution mechanism 2 of a special structure. During the test, the downward vertical force can be successfully converted into a vertical force, a longitudinal force and a lateral force on the test piece, thereby accurately simulating the stress condition of the asphalt overlay layer of the rigid pavement during actual driving, thereby achieving high test accuracy.

[0056] Second, the rigid pavement asphalt overlay crack test device of the present invention has a simple and compact structure, strong adaptability, can be quickly connected with the existing pressure mechanism and conduct tests, has low manufacturing cost, and is easy to promote and apply. In addition, this structure can facilitate the disassembly and replacement of various components. Once the device is damaged, some parts can be replaced as needed, which reduces maintenance costs.

[0057] like Figures 7 to 10 As shown, further, in a preferred embodiment, the two force distribution plates 221 at the outermost sides of the left and right ends of the mounting rod 21 are fastened to the mounting rod 21 by a fixing assembly so that the two force distribution plates 221 do not move when pressed down, and each fixing assembly includes an inner fixing nut 25 and an outer fixing nut 24 for clamping and fixing the force distribution plate 221 on the mounting rod 21. The inner side surfaces of the two force distribution plates 221 are provided with recessed fixing holes for embedding and installing the inner fixing nuts 25.

[0058] The two outermost force distribution plates 221 at the left and right ends are protected and fixed in order to maintain the overall structural stability of the force distribution mechanism 2, so that the overall structure does not tilt or undergo large deformations during extrusion, and to ensure that the displacement of other force distribution plates 221 in the middle is normal. In other embodiments, the two outermost force distribution plates 221 can be welded to the mounting rod 21. By providing an internal fixing nut 25 and an external fixing nut 24, the force distribution plate 221 or the elastic member 23 can be quickly removed during maintenance, and the damaged force distribution plate 221 or the elastic member 23 can be quickly replaced. At the same time, the inner fixing nut 25 is embedded in the inner fixing nut 25 by providing a recessed fixing hole, so that the inner fixing nut 25 will not cause obstruction to the other adjacent force distribution plate 221.

[0059] Further, in a preferred embodiment, the slope inclination angles in the front-to-back direction and the left-to-right direction of the top surface of each force component plate 221 except the two outermost force component plates 221 are both 11.31°, and the slope inclination angles in the front-to-back direction and the left-to-right direction of the bottom surface of each pressure head 12 are also both 11.31°, and the left-to-right direction slope inclination angles of the top surfaces of the two outermost force component plates 221 are both less than 11.31°, so that the pressure head 12 does not contact the two outermost force component plates 221 when pressing down ( Figure 3 The above settings have special scientific considerations:

[0060] First, through repeated and multiple studies and tests, the special angle setting of 11.31°, combined with the aforementioned special structural setting, can optimally convert the vertical force into lateral horizontal force and longitudinal horizontal force during the test, thereby accurately simulating the stress of the rigid road asphalt overlay layer during actual driving. Secondly, the slope inclination angles of the two outermost force distribution plates 221 are all less than 11.31°, so that the pressure head 12 does not contact the two outermost force distribution plates 221 when pressing down. That is, the two outermost force distribution plates 221 will not be directly squeezed by the upper pressure head 12, but will be driven down by the overall downward-moving mounting rod 21. This makes the two force distribution plates 221 only have downward pressure and longitudinal force caused by the overall sliding of the force distribution plate assembly 22 in the front-to-back direction, and no lateral force converted by the pressure head 12 will appear. Such a special setting is because: in order to truly simulate the actual ground contact shape of the radial tire, because in actual conditions, the outermost wheel track of the radial tire has no outward lateral force when the vehicle is in normal driving state. Imagine: if the two outermost force component plates 221 are also completely in contact with the pressure head 12, under the premise that the two force component plates 221 are fixed, as the pressure head 12 presses down, the other force component plates 221 are not completely fixed and can produce lateral displacement. However, since the two outermost force component plates 221 cannot move outward, each group of force component plates 221 will have a certain lateral force at the beginning of the downward pressure. As the displacement increases, the lateral force cannot reach the expected design size and will increase the longitudinal force, thereby affecting the accuracy of the test results and causing the test to fail.

[0061] like Figures 7 to 10 As shown, further, in a preferred embodiment, five groups of force plate assemblies 22 are provided on the mounting rod 21 to simulate the radial tire surface. The radial tire is the most representative tire at present. Through the above settings, the device can simulate the actual road surface being pressed down as realistically as possible, and the scientificity and practicality are greatly enhanced.

[0062] Further, in a preferred embodiment, the spacing between two adjacent groups of force plate assemblies 22 is 1 cm. This spacing setting ensures the normal operation of the device and the test accuracy.

[0063] Furthermore, in a preferred embodiment, a rubber layer is provided on the bottom surface of each force distribution plate 221 to simulate the actual performance of a rubber tire pressing on the ground.

[0064] Furthermore, in a preferred embodiment, lubricating oil is applied on the bottom surface of the pressure head 12 or the top surface of the force distribution plate 221 to facilitate the sliding fit between each pressure head 12 and each force distribution plate 221 and reduce friction.

[0065] like Figures 4 to 6As shown, further, in a preferred embodiment, a connecting rod 111 is provided on the top surface of the loading plate 11 to form a detachable connection with the pressurizing mechanism, so that the device is easy to install and disassemble.

[0066] Based on the above technical feature description, the present invention also provides a top-down cracking test method for a rigid pavement asphalt overlay layer, using any of the above test devices, the steps are as follows:

[0067] Step 1), according to the test requirements, select the corresponding rigid pavement asphalt overlay block as the test piece, connect the loading mechanism 1 and the pressure mechanism, place the force division mechanism 2 on the test piece, and make the force division mechanism 2 under the loading mechanism 1;

[0068] Step 2), start the pressurizing mechanism, so that the pressurizing mechanism drives the loading mechanism 1 to press downward at a speed of 1.5-2.5 mm / min, so that the multiple pressing heads 12 press on the multiple force plate assemblies 22, and the multiple force plate assemblies 22 squeeze the test piece below;

[0069] Step 3), when the specimen is squeezed and cracks are formed, the load value of the pressure mechanism at this time is recorded as the vertical force causing the specimen to crack, that is, the axle load causing the asphalt overlay layer of the rigid pavement to crack from top to bottom.

[0070] Through the above method and equipment, the axle load value that causes the asphalt overlay layer of the rigid road surface to crack from top to bottom can be quickly obtained, with high test efficiency and high test accuracy.

[0071] Based on the above technical feature description, the present invention also provides a top-down crack fatigue test method for an asphalt overlay layer of a rigid pavement, using any of the above test devices, the steps are as follows:

[0072] Step 1), according to the test requirements, select the corresponding rigid pavement asphalt overlay block as the test piece, connect the loading mechanism 1 and the pressure mechanism, place the force division mechanism 2 on the test piece, and make the force division mechanism 2 under the loading mechanism 1;

[0073] Step 2), according to the axle load to be simulated, the pressurizing mechanism is started and the test load is set, so that the pressurizing mechanism drives the loading mechanism 1 to press down according to the test load, so that the multiple pressing heads 12 are pressed on the multiple force plate assemblies 22, and the multiple force plate assemblies 22 squeeze the test piece below;

[0074] Step 3), after the downward pressure load reaches the test load, the pressure mechanism is lifted and loaded again, and the pressure is repeated until the specimen is destroyed. The maximum number of downward pressures when the specimen is destroyed is the fatigue cracking life of the asphalt overlay layer of the rigid pavement from top to bottom under the test load level.

[0075] Through the above methods and equipment, the value of the fatigue cracking life of the asphalt overlay layer of the rigid pavement from top to bottom under the test load level can be quickly obtained, with high test efficiency and high test accuracy.

[0076] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the technical content disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should fall within the scope of protection of the technical solution of the present invention.

Claims

1. A top-down crack test device for rigid pavement asphalt overlay, characterized by: The invention comprises a loading mechanism (1) and a force distribution mechanism (2) for being placed on a test piece, wherein the loading mechanism (1) is connected to a pressurizing mechanism to press the force distribution mechanism (2) downward to perform a test; the force distribution mechanism (2) comprises two or more mounting rods (21), wherein a multi-component force plate assembly (22) is passed through the mounting rods (21) from left to right to simulate a wheel tread; an elastic member (23) is sleeved between two adjacent force distribution plate assemblies (22) on the mounting rods (21) to arrange the multi-component force plate assemblies (22) at intervals; each group of the force distribution plate assemblies (22) comprises two force distribution plates (221) which are fitted together under the pressing action of the elastic member (23); and each of the force distribution plates (221) is provided with a plurality of force distribution plates (221) which are ... ) are arranged with a top surface that is high in front and low in the back in the form of an inclined slope, and the top surface of each of the force component plates (221) is arranged with an inclined slope in the left-right direction, so that the top surface of each force component plate assembly (22) forms a V-shaped groove; the loading mechanism (1) comprises a loading plate (11) and a plurality of pressure heads (12) fixed on the bottom surface of the loading plate (11), the plurality of pressure heads (12) corresponding to the positions of the multi-component force plate assemblies (22) below, the bottom surface of each of the pressure heads (12) being low in front and high in the back in the form of an inclined slope, and the vertical cross section is V-shaped, so as to compress the top surface of the force component plate assembly (22) when pressing downward, so as to convert the vertical force of the pressure head (12) pressing downward into the vertical force, longitudinal force and lateral force of the force component plate assembly (22) on the test piece.

2. The top-down crack test device for rigid pavement asphalt overlay according to claim 1 is characterized by: The two force distribution plates (221) at the outermost sides of the mounting rod (21) are both fastened to the mounting rod (21) via a fixing assembly so that the two force distribution plates (221) do not move when pressed downward. Each of the fixing assemblies comprises an inner fixing nut (25) and an outer fixing nut (24) for clamping and fixing the force distribution plate (221) to the mounting rod (21). The inner side surfaces of the two force distribution plates (221) are each provided with a recessed fixing hole for embedding and installing the inner fixing nut (25).

3. The top-down crack test device for rigid pavement asphalt overlay according to claim 2 is characterized by: The slope inclination angles in the front-to-back direction and the left-to-right direction of the top surfaces of each of the force component plates (221) except the two outermost force component plates (221) are both 11.31°, and the slope inclination angles in the front-to-back direction and the left-to-right direction of the bottom surface of each of the pressure heads (12) are also both 11.31°. The slope inclination angles in the left-to-right direction of the top surfaces of the two outermost force component plates (221) are both less than 11.31°, so that the pressure head (12) does not contact the two outermost force component plates (221) when pressing downward.

4. The top-down crack test device for rigid pavement asphalt overlay according to claim 3 is characterized by: The mounting rod (21) is provided with five groups of force plate components (22) for simulating a radial tire tread.

5. The top-down crack test device for rigid pavement asphalt overlay according to claim 1 is characterized by: The distance between two adjacent groups of force plate assemblies (22) is 1 cm.

6. The top-down crack test device for rigid pavement asphalt overlay according to claim 1 is characterized by: The bottom surface of each force distribution plate (221) is provided with a rubber layer.

7. The top-down crack test device for rigid pavement asphalt overlay according to claim 1 is characterized by: Lubricating oil is applied on the bottom surface of the pressure head (12) or the top surface of the force distribution plate (221).

8. The top-down crack test device for rigid pavement asphalt overlay according to claim 1 is characterized by: A connecting rod (111) is provided on the top surface of the loading plate (11) for forming a detachable connection with a pressurizing mechanism.

9. A method for testing the cracking of asphalt overlays on rigid pavement from top to bottom, characterized by: Using the test device as described in any one of claims 1 to 8, the steps are as follows: Step 1), according to the test requirements, a corresponding rigid road asphalt overlay block is selected as a test piece, the loading mechanism (1) and the pressure mechanism are connected, the force distribution mechanism (2) is placed on the test piece, and the force distribution mechanism (2) is placed below the loading mechanism (1); Step 2), starting the pressurizing mechanism, so that the pressurizing mechanism drives the loading mechanism (1) to press downward at a speed of 1.5-2.5 mm / min, so that the multiple pressing heads (12) are pressed on the multiple force plate assemblies (22) respectively, and the multiple force plate assemblies (22) squeeze the test piece below; Step 3), when the specimen is squeezed to produce cracks, the load value of the pressure mechanism at this time is recorded as the vertical force causing the specimen to crack, that is, the axle load causing the rigid pavement asphalt overlay layer to crack from top to bottom.

10. A method for testing the fatigue of cracks in a rigid pavement asphalt overlay from top to bottom, characterized in that: Using the test device as described in any one of claims 1 to 8, the steps are as follows: Step 1), according to the test requirements, a corresponding rigid road asphalt overlay block is selected as a test piece, the loading mechanism (1) and the pressure mechanism are connected, the force distribution mechanism (2) is placed on the test piece, and the force distribution mechanism (2) is placed below the loading mechanism (1); Step 2), starting the pressurizing mechanism according to the axle load to be simulated and setting the test load, so that the pressurizing mechanism drives the loading mechanism (1) to press downward according to the test load, so that the multiple pressing heads (12) are pressed on the multiple force plate assemblies (22) respectively, and the multiple force plate assemblies (22) squeeze the test piece below; Step 3), after the downward pressure load reaches the test load value, the pressure mechanism is lifted and loaded again and pressed down, and this is repeated until the specimen is destroyed. The maximum number of downward pressure times when the specimen is destroyed is the fatigue cracking life of the asphalt overlay layer of the rigid pavement from top to bottom under the test load level.

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