A device and method for measuring the bond-slip friction parameters between the base and the cushion of asphalt pavement

Abstract

The present application relates to a kind of measuring device and method of asphalt pavement base layer and pad between bonding-slippage friction parameter, it is related to road engineering asphalt pavement technical field, including: test piece restraint mechanism, using double-layer collaborative frame structure, including upper test piece bearing part and lower test piece fixed part, upper test piece bearing part is used to accommodate base layer slippage test piece, lower test piece fixed part is used to accommodate pad slippage test piece, both upper and lower alignment, plate surface coincident arrangement, the real interface contact state of construction base layer and pad, horizontal load applying mechanism, vertical load simulation mechanism and multidimensional parameter monitoring mechanism.The present application will double-layer square test piece, horizontal thrust device and electronic measuring equipment and counterweight load are organically integrated, the accurate determination of bonding-slippage friction parameter between base layer and subgrade pad is realized.The integrity of interface and test precision are guaranteed, the stress state of real reproduction pavement base layer is realized the high-precision characterization of bonding-slippage friction parameter.

Description

Technical Field

[0001] This invention relates to the field of asphalt pavement technology in road engineering, and more particularly to a device and method for measuring the bonding-slip friction parameters between the base course and subbase of asphalt pavement. Background Technology

[0002] Shrinkage cracking is a major distress in asphalt pavements. One of the main factors influencing shrinkage cracking in asphalt pavements is the friction between the base course and the subbase, characterized by the bond-slip parameter. The base course generates horizontal shear force under the influence of temperature shrinkage and vehicle load transmission. The interfacial bond strength between the base course and the subbase directly restricts its shrinkage deformation. Insufficient interfacial bond or uncontrolled slip characteristics can easily lead to pavement shoving, rutting, shrinkage cracking, and other distresses, significantly shortening the pavement's service life. The bond-slip friction parameter between the base course and the subbase of asphalt pavements is a key mechanical indicator characterizing the shear slip resistance and relative slip characteristics of the interface between the base course (e.g., cement-stabilized crushed stone layer) and the subbase (e.g., graded crushed stone layer). This parameter directly relates to the stress transmission and collaborative performance between the base course and the subbase under vehicle loads and temperature changes, and has a decisive impact on the overall stability of the pavement structure. Therefore, accurately characterizing the bond-slip friction parameter between the base course (e.g., cement-stabilized crushed stone layer) and the subbase (e.g., graded crushed stone layer) is a core prerequisite for optimizing pavement structure design and improving engineering reliability. In existing pavement structures, insufficient interlayer bonding or improper control of slip characteristics often leads to relative displacement and stress concentration between layers, resulting in defects such as shoving, rutting, and cracking, significantly shortening the pavement's service life. Therefore, accurate characterization and reasonable control of the bond-slip friction parameters between the base course and subbase can not only effectively improve the scientific nature and reliability of pavement structure design, but also provide technical support for defect prevention and durability improvement, possessing significant engineering application value.

[0003] In actual road stress analysis, the base layer will shrink under the influence of its own temperature shrinkage characteristics and the stable stress transmitted from the upper part. Theoretically, if the base layer and the subbase can slide freely, the base layer can shrink freely without cracking. However, in reality, there is obvious adhesion between the base layer and the subbase, which restricts the shrinkage of the base layer and thus causes cracking. Adhesive shear force is generated at the contact surface between the subbase and the base layer. Figure 1 Figure 1 shows a schematic diagram of low-temperature shrinkage and slippage between the base layer and the subbase layer. Figure 2(a) shows a schematic diagram of the influencing factors of low-temperature shrinkage of cement-stabilized crushed stone, and Figure 3(b) shows a schematic diagram of the stress analysis of low-temperature shrinkage of cement-stabilized crushed stone.

[0004] Existing technologies have significant shortcomings in measuring the bond-slip parameters at the interface between the base course and subbase of asphalt pavements: relevant test methods and results are almost non-existent in the literature, lacking reference standards and reliable data; field testing is complex and labor-intensive, and is significantly affected by construction conditions and environmental factors, making it difficult to guarantee accuracy; at the same time, base course samples excavated in the field cannot truly reflect the wetting and bonding effects of cement, fly ash, and other binders at the interface, and the interface bonding characteristics are easily damaged, leading to distorted parameter measurements and making it difficult to accurately reflect the actual performance of the pavement; furthermore, due to the lack of unified methods and reliable data, existing test results are difficult to provide effective guidance for engineering design and are also difficult to promote in large-scale applications.

[0005] Existing patent document CN109115633A discloses a device and method for testing the mechanical friction strength between asphalt surface layers. This technology focuses on testing the mechanical friction strength between asphalt surface layers, with a core focus on optimizing the gradation combination of surface layers. It is actually a vertical shear test, not a horizontal one, which is completely different from the test object of the base layer and subbase layer in this invention. Its test object is limited to asphalt mixture surface layers and does not consider the interface characteristics differences between the base layer and subbase layer, making it unsuitable for actual loose subbase materials. Existing patent document CN119413711A discloses a self-slip testing system and method for base layer and lower layer. This technology is for detecting the amount of micro-slip between the base layer and lower layer. The lower layer belongs to the category of asphalt surface layers, and the research focuses on the minute self-slip between the base layer and the asphalt lower layer, not the subbase layer of this invention. The test object is essentially still the base layer-surface layer interface, which is fundamentally different from the material characteristics and bonding mechanism of the base layer-subbase layer interface. Existing patent document CN106644933A discloses a test method for the interlayer bond strength of asphalt pavement, which belongs to the vertical force test. However, the present invention is aimed at the bond-slip characteristics in the horizontal shear direction. The force form is completely different from the test target. The pull-out force is inconsistent with the horizontal shear force generated by the actual shrinkage of the base layer, and the test results lack engineering relevance.

[0006] Therefore, developing a measuring device and method that can accurately reflect the bond-slip properties of the asphalt pavement base course and subbase interface, while being easy to operate and cost-effective, has significant practical application value. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a device and method for measuring the bond-slip friction parameters between the base course and subbase of asphalt pavement. The invention utilizes a specimen constraint mechanism to achieve precise positioning and interface bonding of the base course and subbase slip specimens; a vertical load simulation mechanism applies the gravity of the asphalt surface layer to recreate the true contact state of the interface; a horizontal load application mechanism applies a horizontal thrust to the base course slip specimen, inducing shear slip at the base course and subbase interface; a multi-dimensional parameter monitoring mechanism, through a combination of a first dial gauge, a second dial gauge, and a stress ring micrometer, simultaneously collects dynamic data on the relative slip and bond shear force at the base course and subbase interface. The changes in instrument values ​​are recorded manually, and the data is analyzed using the calculation formulas for relative slip and bond stress to generate a complete bond-slip relationship curve including the rising segment, the falling segment, and the residual bond stage. Finally, core friction parameters such as the maximum bond stress and critical slip are extracted, achieving high-precision, multi-dimensional characterization of mechanical properties such as the bond-slip constitutive relationship.

[0008] The technical means employed in this invention are as follows:

[0009] A device for measuring the bond-slip friction parameters between the base course and subbase of an asphalt pavement, comprising:

[0010] The specimen constraint mechanism, serving as the bearing and positioning benchmark for the sliding specimens of the base layer and the subbase layer, adopts a double-layer collaborative frame structure, including an upper specimen bearing part and a lower specimen fixing part. The upper specimen bearing part is used to accommodate the base layer sliding specimen, and the lower specimen fixing part is used to accommodate the subbase layer sliding specimen. The two are aligned vertically and their surfaces overlap to construct a real interface contact state between the base layer and the subbase layer.

[0011] A horizontal load application mechanism is used to apply a stable and controllable horizontal thrust to the base slip specimen to simulate the shearing effect caused by the shrinkage of the base in the actual road surface. The horizontal load application mechanism is connected to the bearing part of the upper specimen to ensure that the thrust is uniformly transmitted in the horizontal direction.

[0012] A vertical load simulation mechanism is used to reproduce the vertical pressure of the asphalt surface layer on the base layer. The vertical load simulation mechanism is located above the bearing part of the upper specimen and applies vertical gravity by counterweight loading to ensure that the interface contact state is consistent with the actual road surface.

[0013] A multi-dimensional parameter monitoring mechanism is used to simultaneously collect interfacial bond shear force and relative slip. It includes a first dial gauge, a second dial gauge, a micrometer gauge, and a stress ring. The first dial gauge is compressed to near its maximum range and is located on the left side of the base slip specimen. The second dial gauge is located on the right side of the cushion slip specimen with its pointer at approximately its initial position. The two work together to obtain the relative slip. The micrometer gauge is mounted on the stress ring, which is in contact with the cushion slip specimen, and is used to obtain interfacial bond shear force data.

[0014] Furthermore, the upper specimen bearing part and the lower specimen fixing part of the specimen constraint mechanism both adopt frame dimensions that match the asphalt mixture rutting plate specimen, ensuring the compatibility of specimen molding and installation; the lower specimen fixing part is isolated from the ground by pad blocks to eliminate friction interference between the slipped subbase specimen and the ground, ensuring that the horizontal thrust is fully applied to the interface between the base layer and the subbase.

[0015] Furthermore, the horizontal load application mechanism includes a horizontal thrust output unit and a force transmission component. The horizontal thrust output unit adopts a load ratio tester or a jack, and the force transmission component is equipped with a limiting structure to ensure that the thrust only acts on the upper specimen bearing part and avoids interference with the lower specimen fixing part.

[0016] Furthermore, the limiting structure includes a protruding metal pad that is pasted and installed at the bottom specimen placement position of the load-bearing ratio tester according to the layer height of the double-layer rutted board.

[0017] Furthermore, the vertical load simulation mechanism includes a counterweight box and adjustable counterweight blocks. The counterweight box is detachably connected to the upper specimen bearing part. The vertical load can be adjusted by increasing or decreasing the number of adjustable counterweight blocks to meet the gravity simulation requirements of asphalt pavement layers of different thicknesses.

[0018] This invention also discloses a method for measuring the bond-slip friction parameters between the base course and subbase of asphalt pavement, using the aforementioned measuring device, and comprising the following steps:

[0019] Step 1: Specimen preparation and installation. Prepare base layer sliding specimens and subbase sliding specimens according to the actual engineering mix proportions. Place the subbase sliding specimen in the fixed part of the lower specimen and the base layer sliding specimen in the bearing part of the upper specimen, ensuring that the interfaces of the two are tightly fitted and the plate surfaces are aligned. Use spacers to isolate the fixed part of the lower specimen from the ground to complete the specimen assembly.

[0020] Step 2: Load application settings. Place an adjustable counterweight of preset weight on the counterweight box of the vertical load simulation mechanism to reproduce the vertical gravity of the asphalt surface layer; debug the horizontal load application mechanism and set the horizontal thrust loading rate.

[0021] Step 3: Install the monitoring system. Compress the first dial gauge to near its maximum range and place it on the left side of the base slip specimen; place the second dial gauge with its pointer at approximately the initial position on the right side of the cushion slip specimen; install the micrometer on the stress ring, bring the stress ring into contact with the cushion slip specimen, and fix the other end through the upper crossbeam of the horizontal load application mechanism.

[0022] Step 4: Test Start-up and Data Acquisition. Start the horizontal load application mechanism to apply horizontal thrust to the upper specimen bearing part, and obtain the changes in each table after the start of the test until the end of the test; export the data obtained from each table, read the data once at a certain interval, and record it into the table respectively;

[0023] Step 5: Parameter analysis and curve generation. The collected data is processed to calculate the relative slip between the base course and the subbase and the corresponding bond stress, generating a complete bond-slip relationship curve between the pavement base course and the subbase.

[0024] Furthermore, the collected data is processed according to the following formula:

[0025]

[0026] In the formula: The relative slippage (mm) between the base slippage specimen and the cushion slippage specimen at each moment;

[0027] The initial value (mm) of the dial gauge on the base slip specimen;

[0028] The dial gauge value (mm) of the base slip specimen at each moment;

[0029] The initial value (mm) of the dial gauge for the slippage test specimen of the cushion layer;

[0030] The values ​​(mm) of the dial gauge on the slip test specimen of the cushion layer at each moment are shown.

[0031]

[0032] In the formula: The bonding stress (kPa) between the base course and the subgrade layer.

[0033] The initial value (mm) of the stress ring dial gauge;

[0034] The value (mm) of the stress ring dial gauge at each moment;

[0035] It is the stiffness coefficient or force-deformation coefficient of the stress ring (kN / mm);

[0036] The interfacial contact area (m²) between the base slip specimen and the cushion slip specimen. 2 ).

[0037] Furthermore, according to theoretical analysis, the bond-slip relationship is divided into an ascending stage and a descending stage. After reaching the peak, the bond strength gradually decreases as the slip increases, eventually tending to 0 and remaining constant. After observing that the dial gauge value reaches its maximum value, it is still necessary to continue monitoring for a period of time until the dial gauge value hardly changes anymore, and then stop the experiment to obtain the complete bond-slip constitutive relationship between the base course and the subgrade.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] 1. The double-layer frame structure of the specimen constraint mechanism is adapted to the standard specimen size to ensure a tight fit at the interface; the design of the lower layer being fixed and the upper layer being sliding can restore the relative motion state between the base layer and the subbase layer when the base layer shrinks, solving the defects of misalignment of test objects and poor interface fit in existing technologies. This invention realizes the testing of the base layer-subbase layer interface, and the test results are more engineering-specific.

[0040] 2. By employing a horizontal load application mechanism and a vertical load simulation mechanism, the combined stress of horizontal shear thrust and vertical gravity is reproduced, perfectly matching the interface stress during base layer shrinkage in actual road surfaces. The vertical counterweight features an adjustable design, adapting to testing requirements with varying surface layer thicknesses and ensuring that test data directly supports engineering design. The horizontal load application mechanism supports manual operation, eliminating the need for electricity and making it suitable for field use. Furthermore, existing testing equipment is mostly testing machines, capable only of vertical loading, making it unsuitable for testing loose subbase materials; while the device of this invention can be placed horizontally, suitable for loose materials such as subbases, effectively overcoming the application limitations of existing equipment.

[0041] 3. The dual-diameter gauges of the multi-dimensional parameter monitoring mechanism collect data synchronously with the stress ring. Combined with data processing formulas, it can generate a complete bond-slip constitutive relationship curve, realizing a full-dimensional characterization of interfacial friction characteristics and providing more comprehensive data support for subsequent analysis. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 The diagram shows the low-temperature shrinkage and slippage of the base layer and the subbase layer. (a) is a schematic diagram of the influencing factors of low-temperature shrinkage of cement-stabilized crushed stone; (b) is a schematic diagram of the stress analysis of low-temperature shrinkage of cement-stabilized crushed stone.

[0044] Figure 2 This is a system diagram of the present invention.

[0045] Figure 3 The results of the bond-slip test between the base course and the subbase are shown. (a) is a graded crushed stone subbase; (b) is a natural gravel subbase; (c) is a sandy soil subbase; and (d) is the maximum bond stress of different subbase materials.

[0046] Figure 4 The slip failure interface of the base course and the subbase course bond-slip test is shown in the figure. (a) is a graded crushed stone subbase; (b) is a natural gravel subbase; and (c) is a sandy soil subbase.

[0047] In the figure: 1. Base slip specimen; 2. Subbase slip specimen; 3. Pad block; 4. Horizontal load application mechanism; 5. Metal pad block; 6. Counterweight box; 7. Counterweight block; 81. First dial indicator; 82. Second dial indicator; 9. Micrometer indicator; 10. Stress ring. Detailed Implementation

[0048] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0051] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0052] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0053] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0054] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0055] like Figure 2As shown in the figure, an embodiment of the present invention discloses a measuring device for the bond-slip friction parameters between the base course and the subbase course of an asphalt pavement, comprising:

[0056] The specimen constraint mechanism, serving as the bearing and positioning benchmark for the base layer sliding specimen 1 and the cushion layer sliding specimen 2, adopts a double-layer collaborative frame structure, including an upper specimen bearing part and a lower specimen fixing part. The upper specimen bearing part is used to accommodate the base layer sliding specimen, and the lower specimen fixing part is used to accommodate the cushion layer sliding specimen. The two are aligned vertically and their surfaces overlap to construct a real interface contact state between the base layer and the cushion layer.

[0057] The horizontal load application mechanism 4 is used to apply a stable and controllable horizontal thrust to the base slip specimen to simulate the shearing effect caused by the shrinkage of the base layer in the actual road surface. The horizontal load application mechanism is connected to the bearing part of the upper specimen to ensure that the thrust is uniformly transmitted in the horizontal direction.

[0058] A vertical load simulation mechanism is used to reproduce the vertical pressure of the asphalt surface layer on the base layer. The vertical load simulation mechanism is located above the upper specimen bearing part and includes a counterweight box 6 and a counterweight block 7. The counterweight box 6 is detachably connected to the upper specimen bearing part. The vertical load can be adjusted by increasing or decreasing the number of counterweight blocks 7 to meet the gravity simulation requirements of asphalt surface layers of different thicknesses.

[0059] A multi-dimensional parameter monitoring mechanism is used to simultaneously collect interfacial bond shear force and relative slip, including a first dial gauge 81, a second dial gauge 82, a micrometer gauge 9, and a stress ring 10; the first dial gauge 81 is compressed to near its maximum range and is located on the left side of the base slip specimen 1; the pointer of the second dial gauge 82 is at approximately its initial position and is located on the right side of the cushion slip specimen 2; the micrometer gauge 9 is mounted on the stress ring 10, and the stress ring 10 is in contact with the cushion slip specimen 2 to monitor the interfacial bond shear force.

[0060] Specifically, the dial indicator of the base slip specimen is set on the left side. When the specimen is compressed to near its maximum range and a thrust is applied, the base slip specimen will produce a displacement to the right. At this time, the dial indicator pointer on the base side will rebound. The slip amount = the initial value of the dial indicator (mm) - the value of the dial indicator at each moment (mm), where the initial value is the maximum value.

[0061] The dial indicator for the slip test specimen of the subbase is located on the right side, with the pointer at the initial position. When a thrust is applied, the slip test specimen of the base layer will move to the right, thereby causing the slip test specimen of the subbase layer below to move synchronously. However, the displacement is relatively small, which causes the dial indicator pointer on the subbase side to be compressed. The slip amount = the value of the dial indicator at each moment (mm) - the initial value of the dial indicator (mm), where the initial value is the smallest value.

[0062] Ultimately, both the base slip specimen and the subbase slip specimen will shift to the right to a certain extent, and the displacement of the base slip specimen is greater than that of the subbase slip specimen. The relative slip amount is the base slip amount minus the subbase slip amount.

[0063] This invention uses manual data processing. First, the changes in the readings of the first, second, and third dial gauges are recorded using the screen recording function of a mobile phone. Then, the data is processed according to the calculation method of relative slip and stress, and finally, a graph is drawn.

[0064] Furthermore, the upper specimen bearing part and the lower specimen fixing part of the specimen constraint mechanism both adopt frame dimensions that match the asphalt mixture rutting plate specimen, ensuring the compatibility of specimen molding and installation; the lower specimen fixing part is isolated from the ground by the pad block 3, eliminating friction interference between the slippage specimen and the ground, and ensuring that the horizontal thrust is fully applied to the interface between the base layer and the subbase layer.

[0065] Furthermore, the horizontal load application mechanism includes a horizontal thrust output unit and a force transmission component. The horizontal thrust output unit uses a load ratio tester or a jack to provide power by hand-cranking or de-energizing the load, thus ensuring its use on the construction site. The force transmission component is equipped with a limiting structure to ensure that the thrust only acts on the upper specimen bearing part, avoiding interference with the lower specimen fixing part.

[0066] Furthermore, the limiting structure includes a protruding metal pad 5 that is pasted and installed at the bottom specimen placement position of the load-bearing ratio tester according to the layer height of the double-layer rutted board.

[0067] Furthermore, the vertical load simulation mechanism includes a counterweight box and adjustable counterweight blocks. The counterweight box is detachably connected to the upper specimen bearing part. The vertical load can be adjusted by increasing or decreasing the number of adjustable counterweight blocks to meet the gravity simulation requirements of asphalt pavement layers of different thicknesses.

[0068] This invention also discloses a method for measuring the bond-slip friction parameters between the base course and subbase of asphalt pavement, using the aforementioned measuring device, and comprising the following steps:

[0069] Step 1: Specimen preparation and installation. Prepare base layer sliding specimens and subbase sliding specimens according to the actual engineering mix proportions. Place the subbase sliding specimen in the fixed part of the lower specimen and the base layer sliding specimen in the bearing part of the upper specimen, ensuring that the interfaces of the two are tightly fitted and the plate surfaces are aligned. Use spacers to isolate the fixed part of the lower specimen from the ground to complete the specimen assembly.

[0070] Step 2: Load application settings. Place an adjustable counterweight of preset weight on the counterweight box of the vertical load simulation mechanism to reproduce the vertical gravity of the asphalt surface layer; debug the horizontal load application mechanism and set the horizontal thrust loading rate.

[0071] Step 3: Install the monitoring system. Compress the first dial gauge to near its maximum range and place it on the left side of the base slip specimen; place the second dial gauge with its pointer at approximately the initial position on the right side of the cushion slip specimen; install the micrometer on the stress ring, bring the stress ring into contact with the cushion slip specimen, and fix the other end through the upper crossbeam of the horizontal load application mechanism.

[0072] Step 4: Test Start-up and Data Acquisition. Start the horizontal load application mechanism to apply horizontal thrust to the upper specimen bearing part, and obtain the changes in each table after the start of the test until the end of the test; export the data obtained from each table, read the data once at a certain interval, and record it into the table respectively;

[0073] In this embodiment, the test is started and data is collected. The horizontal load application mechanism is activated to apply a horizontal thrust to the upper specimen bearing part. The changes of each table after the start of the test are recorded using the mobile phone video function until the end of the test. The video recordings of each table are exported, and the data is read every 5 seconds and recorded into the table respectively.

[0074] Step 5: Parameter analysis and curve generation. The collected data is processed to calculate the relative slip between the base course and the subbase and the corresponding bond stress, generating a complete bond-slip relationship curve between the pavement base course and the subbase.

[0075] Specifically, the collected data is processed according to the following formula:

[0076]

[0077] In the formula: The relative slippage (mm) between the base slippage specimen and the cushion slippage specimen at each moment;

[0078] The initial value (mm) of the dial gauge on the base slip specimen;

[0079] The dial gauge value (mm) of the base slip specimen at each moment;

[0080] The initial value (mm) of the dial gauge for the slippage test specimen of the cushion layer;

[0081] The values ​​(mm) of the dial gauge on the slip test specimen of the cushion layer at each moment;

[0082]

[0083] In the formula: The bonding stress (kPa) between the base course and the subgrade layer.

[0084] The initial value (mm) of the stress ring dial gauge;

[0085] The value (mm) of the stress ring dial gauge at each moment;

[0086] It is the stiffness coefficient or force-deformation coefficient of the stress ring (kN / mm);

[0087] The interfacial contact area (m²) between the base slip specimen and the cushion slip specimen. 2 ).

[0088] Furthermore, according to theoretical analysis, the bond-slip relationship is divided into an ascending stage and a descending stage. After reaching the peak, the bond strength gradually decreases as the slip increases, eventually tending to 0 and remaining constant. After observing that the dial gauge value reaches its maximum value, it is still necessary to continue monitoring for a period of time until the dial gauge value hardly changes anymore, and then stop the experiment to obtain the complete bond-slip constitutive relationship between the base course and the subgrade.

[0089] The slip relationship between the base course and the subbase can be represented by a simplified bilinear bond-slip constitutive model, the formula of which is shown below:

[0090]

[0091] In the formula: —Local bond stress;

[0092] —Relative slip;

[0093] —Local maximum bond stress;

[0094] —The relative slip corresponding to the local maximum bond stress;

[0095] —Maximum relative slip.

[0096] Example 1

[0097] This embodiment discloses a method for measuring the bond-slip friction parameters between the base course and subbase of asphalt pavement, using the aforementioned measuring device, and including the following steps:

[0098] Step 1: Specimen Preparation and Installation. Base course slip test specimens and subbase slip test specimens are prepared according to the actual engineering mix proportions. The dimensions of both base course slip test specimens and subbase slip test specimens are 300mm × 300mm × 50mm. The crushed stone gradation of the base course slip test specimens is shown in Table 1 below, using 5.0% optimum moisture content and 5.0% optimum cement content. The crushed stone material is limestone. The subbase slip test specimens use three commonly used materials: graded crushed stone, natural gravel, and sand. The graded crushed stone subbase uses the same gradation as the base course, with limestone as the crushed stone material. The natural gravel and sand subbases are designed according to specifications. The specific gradations of the three subbase materials are shown in Table 2 below. The optimal water content for the graded crushed stone cushion layer is 4.36% based on previous engineering experience, while the optimal water content for the natural gravel and sandy soil cushion layers is 4.5% and 5.5%, respectively. The cushion layer slip test specimen is placed in the fixed part of the lower specimen, and the base layer slip test specimen is placed in the bearing part of the upper specimen, ensuring that the interface of the two is tightly fitted and the plate surfaces are aligned. The fixed part of the lower specimen is isolated from the ground by the pad block to complete the specimen assembly.

[0099] Table 1. Design gradation of base materials

[0100]

[0101] Table 2 Design Gradation of Subgrade Subbase Materials

[0102]

[0103] Step 2: Load application settings. Place an adjustable counterweight of preset weight on the counterweight box of the vertical load simulation mechanism to reproduce the vertical gravity of the asphalt surface layer; debug the horizontal load application mechanism and set the horizontal thrust loading rate.

[0104] Step 3: Install the monitoring system. Compress the first dial gauge to near its maximum range and place it on the left side of the base slip specimen. Place the second dial gauge with its pointer at approximately the initial position on the right side of the cushion slip specimen. Install the micrometer on the stress ring, making contact between the stress ring and the cushion slip specimen. Fix the other end of the micrometer to the upper crossbeam of the horizontal load application mechanism. If using a bearing ratio tester, first remove the stress ring, install the micrometer, and then re-fix it. Attach metal pads at the specimen placement area at the bottom of the tester according to the height of the double-layer specimen to ensure that the thrust is applied only to the upper base slip specimen.

[0105] Step 4: Test Start-up and Data Acquisition. Start the horizontal load application mechanism to apply horizontal thrust to the upper layer specimen bearing part. Use the mobile phone video function to record the changes of each table after the start of the test until the end of the test. Export the recorded videos of each table, read the data every 5 seconds, and record them into the tables respectively. Make 3 parallel specimens for each type of cushion material. The specimen curing age is three months to ensure that the bonding strength of the specimens reaches the actual level of the project.

[0106] Through experiments, data from dial gauges on base course slip specimens, subgrade slip specimens, and stress rings were analyzed and recorded. The experiments employed video recording and manual data retrieval, with data read every 5 seconds. After data collection, the experimental data were analyzed and processed, and the relative slip between the base course and subgrade, as well as the corresponding bond stress, were calculated using the following formula.

[0107]

[0108] In the formula: —The relative slip amount (mm) between the base slip specimen and the cushion slip specimen at each moment;

[0109] —Initial value (mm) of dial gauge for base slip specimen;

[0110] —Values ​​(mm) of the dial gauge at each moment for the base slip specimen;

[0111] —Initial value (mm) of dial gauge for slippage test specimen of cushion layer;

[0112] —Values ​​(mm) of the dial gauge at each moment for the slippage test specimen.

[0113]

[0114] In the formula: — Bond stress between base course and subgrade (kPa).

[0115] —Initial value of the stress ring dial gauge (mm);

[0116] —The value of the stress ring dial gauge at each moment (mm);

[0117] The results of the bonding-slip test between the base layer and the subbase are shown in the figure. Figure 3 (a), (b), (c), (d).

[0118] The slip failure interface of the base layer and subbase layer bond-slip test is shown below. Figure 4 (a), (b), (c).

[0119] Furthermore, theoretical analysis shows that the bond-slip relationship consists of an ascending phase and a descending phase. After reaching the peak, the bond strength gradually decreases with increasing slip, eventually approaching zero and remaining constant. After observing that the dial gauge reading reaches its maximum value, monitoring should continue for a period of time until the dial gauge reading hardly changes anymore, at which point the experiment is stopped, thus obtaining the complete bond-slip constitutive relationship between the base course and the subgrade. The slip relationship between the base course and the subgrade can be represented by a simplified bilinear bond-slip constitutive model.

[0120] In the experiment, a stable thrust was applied to the cement-stabilized crushed stone base course. Without the restriction of the subbase, the cement-stabilized crushed stone base course could slide freely. However, in actual engineering, the subbase restricts its free sliding. Shear bond stress is generated at the contact surface between the two. The magnitude of the bond force is related to the materials, gradation and embedment of the two.

[0121] The experimental results show that the bond-slip characteristics between different subbase materials and cement-stabilized crushed stone base courses differ, but the overall trend is consistent with the theoretical analysis, exhibiting a clear two-stage characteristic: the first stage is the rising stage, where the bond stress between the base course and the subbase gradually increases with the increase of slip until it reaches the peak bond stress; the second stage is the falling stage, where the bond stress gradually decreases with the continued increase of slip and then tends to stabilize. The consistency between the experimental results and the theoretical analysis results in terms of trend indicates that the bond-slip constitutive relation used in the theoretical analysis is reasonable. The experimental results also show that the maximum bond stress between the subbase material and the cement-stabilized crushed stone base course is in the order of graded crushed stone > natural gravel > sand, but the dispersion is relatively large, which is consistent with the characteristics of cement-stabilized crushed stone base courses. This is closely related to the gradation characteristics and physical properties of different subbase materials: graded crushed stone, due to its well-designed gradation, encompasses aggregates of various particle sizes and has a relatively smooth gradation curve. Coarse aggregates form a stable skeleton, while fine aggregates fully fill the pores, effectively ensuring the density of the subbase itself. Simultaneously, its prominent aggregate shape not only increases the internal friction between particles but also enhances the interfacial friction with the upper cement-stabilized crushed stone base layer. Therefore, the bond stress between the graded crushed stone subbase and the cement-stabilized crushed stone base layer is relatively high. In contrast, natural sand and gravel have a lower content of fine aggregate in their gradation, resulting in higher porosity between particles and lower density compared to graded crushed stone. The natural gravel particles have a smoother, rounder surface, resulting in lower internal friction between particles and weaker interfacial friction when in contact with the cement-stabilized crushed stone base. Therefore, the bond stress between the natural gravel cushion layer and the cement-stabilized crushed stone base is lower than that of the graded crushed stone cushion layer. For sand, the smaller particle size and lack of coarse aggregate to form a stable skeleton structure mean that even after compaction, the overall structure remains loose, with weak interparticle self-adhesion and limited interfacial embedding area with the cement-stabilized crushed stone base. Furthermore, the lower strength of sand itself results in the lowest bond stress between the sand cushion layer and the cement-stabilized crushed stone base. The relationship between the bond stress between different cushion materials and the base layer is consistent with the theoretical analysis results, verifying the feasibility and practicality of this invention.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for measuring the bond-slip friction parameters between the base course and subbase of an asphalt pavement, characterized in that, include: The specimen constraint mechanism, serving as the bearing and positioning benchmark for the sliding specimens of the base layer and the subbase layer, adopts a double-layer collaborative frame structure, including an upper specimen bearing part and a lower specimen fixing part. The upper specimen bearing part is used to accommodate the base layer sliding specimen, and the lower specimen fixing part is used to accommodate the subbase layer sliding specimen. The two are aligned vertically and their surfaces overlap to construct a real interface contact state between the base layer and the subbase layer. A horizontal load application mechanism is used to apply a stable and controllable horizontal thrust to the base slip specimen to simulate the shearing effect caused by the shrinkage of the base layer in actual road surface. The horizontal load application mechanism is connected to the bearing part of the upper specimen. A vertical load simulation mechanism is used to reproduce the vertical pressure of the asphalt surface layer on the base layer. The vertical load simulation mechanism is located above the bearing part of the upper specimen and applies vertical gravity by counterweight loading to ensure that the interface contact state is consistent with the actual road surface. A multi-dimensional parameter monitoring mechanism is used to simultaneously collect interfacial bond shear force and relative slip. It includes a first dial gauge, a second dial gauge, a micrometer gauge, and a stress ring. The first dial gauge is compressed to near its maximum range and is located on the left side of the base slip specimen. The second dial gauge is located on the right side of the cushion slip specimen with its pointer at approximately its initial position. The two work together to obtain the relative slip. The micrometer gauge is mounted on the stress ring, which is in contact with the cushion slip specimen, and is used to obtain interfacial bond shear force data.

2. The measuring device for the bonding-slip friction parameters between the base course and subbase of asphalt pavement according to claim 1, characterized in that, The upper specimen bearing part and the lower specimen fixing part of the specimen restraint mechanism both adopt frame dimensions that match the asphalt mixture rutting plate specimen; the lower specimen fixing part is isolated from the ground by pad blocks to eliminate friction interference between the slipped subbase specimen and the ground, ensuring that the horizontal thrust is fully applied to the interface between the base layer and the subbase.

3. The measuring device for the bond-slip friction parameters between the base course and subbase of asphalt pavement according to claim 1, characterized in that, The horizontal load application mechanism includes a horizontal thrust output unit and a force transmission component. The horizontal thrust output unit is a load-bearing ratio tester or a jack. The force transmission component is equipped with a limiting structure to ensure that the thrust only acts on the upper specimen bearing part.

4. The measuring device for the bonding-slip friction parameters between the base course and subbase of asphalt pavement according to claim 3, characterized in that, The limiting structure includes a protruding metal pad that is pasted and installed at the bottom specimen placement position of the load-bearing ratio tester according to the layer height of the double-layer rutted board.

5. The measuring device for the bond-slip friction parameters between the base course and subbase of asphalt pavement according to claim 1, characterized in that, The vertical load simulation mechanism includes a counterweight box and adjustable counterweight blocks. The counterweight box is detachably connected to the upper specimen bearing part. The vertical load can be adjusted by increasing or decreasing the number of adjustable counterweight blocks to meet the gravity simulation requirements of asphalt pavement layers of different thicknesses.

6. A method for measuring the bond-slip friction parameters between the base course and subbase of an asphalt pavement based on the measuring device for bond-slip friction parameters between the base course and subbase of an asphalt pavement according to any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Specimen preparation and installation. Prepare base layer sliding specimens and subbase sliding specimens according to the actual engineering mix proportions. Place the subbase sliding specimen in the fixed part of the lower specimen and the base layer sliding specimen in the bearing part of the upper specimen, ensuring that the interfaces of the two are tightly fitted and the plate surfaces are aligned. Use spacers to isolate the fixed part of the lower specimen from the ground to complete the specimen assembly. Step 2: Load application settings. Place an adjustable counterweight of preset weight on the counterweight box of the vertical load simulation mechanism to reproduce the vertical gravity of the asphalt surface layer; debug the horizontal load application mechanism and set the horizontal thrust loading rate. Step 3: Install the monitoring system. Compress the first dial gauge to near its maximum range and place it on the left side of the base slip specimen; place the second dial gauge with its pointer at approximately the initial position on the right side of the cushion slip specimen; install the micrometer on the stress ring, bring the stress ring into contact with the cushion slip specimen, and fix the other end through the upper crossbeam of the horizontal load application mechanism. Step 4: Test Start-up and Data Acquisition. Start the horizontal load application mechanism to apply horizontal thrust to the upper specimen bearing part, and obtain the changes in each table after the start of the test until the end of the test; export the data obtained from each table, read the data once at a certain interval, and record it into the table respectively; Step 5: Parameter analysis and curve generation. The collected data is processed to calculate the relative slip between the base course and the subbase and the corresponding bond stress, generating a complete bond-slip relationship curve between the pavement base course and the subbase.

7. The method according to claim 6, characterized in that, The collected data is processed according to the following formula: In the formula: The relative slippage (mm) between the base slippage specimen and the cushion slippage specimen at each moment; The initial value (mm) of the dial gauge on the base slip specimen; The dial gauge value (mm) of the base slip specimen at each moment; The initial value (mm) of the dial gauge for the slippage test specimen of the cushion layer; The values ​​(mm) of the dial gauge on the slip test specimen of the cushion layer at each moment; In the formula: The bonding stress (kPa) between the base course and the subgrade layer. The initial value (mm) of the stress ring dial gauge; The value (mm) of the stress ring dial gauge at each moment; It is the stiffness coefficient or force-deformation coefficient of the stress ring (kN / mm); The interfacial contact area (m²) between the base slip specimen and the cushion slip specimen. 2 ).

8. The method according to claim 6, characterized in that, According to theoretical analysis, the bond-slip relationship is divided into an ascending stage and a descending stage. After reaching the peak, the bond strength gradually decreases as the slip increases, eventually tending to 0 and remaining constant. After observing that the dial gauge value reaches its maximum value, it is still necessary to continue monitoring for a period of time until the dial gauge value hardly changes anymore, and then stop the test to obtain the complete bond-slip constitutive relationship between the base course and the subgrade.

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