Dynamic resilience modulus testing method for simulating real service state of roadbed

Abstract

The invention relates to the technical field of road evaluation, in particular to a dynamic resilience modulus testing method for simulating a real service state of a roadbed. The method comprises the following steps: setting a vertical downward loading force for a soil foundation in test software, setting different loading frequencies and repetition times, starting a servo control system for testing, collecting monitoring data in the testing process, and determining the dynamic rebound modulus of the soil foundation according to the change relationship among the size of a bearing plate, the loading frequency and the dynamic rebound modulus of the soil foundation in the first stage. Dynamic resilience moduli of the bearing plates with different sizes under different loading frequencies are obtained; and in combination with the dynamic resilience moduli of the bearing plates of different sizes under different loading frequencies, according to the dynamic resilience moduli of the bearing plates of different sizes and the lantern rings of different sizes under different loading frequencies in the second stage, a roadbed dynamic modulus estimation model under the influence of the self weight of the structural layer is obtained, and then the dynamic resilience modulus value of the top surface of the roadbed is estimated. According to the invention, the accuracy of a rebound modulus test result is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of road evaluation, and particularly relates to a dynamic resilient modulus test method for simulating the actual service state of a roadbed. Background Art

[0002] In the design of pavement structures, the resilient modulus of the roadbed represents the anti-deformation ability of the roadbed and pavement, and is one of the important parameters affecting the thickness of the pavement structure layer. The accurate and rapid determination of the resilient modulus has important engineering application value for the design of roadbed and pavement structures, construction quality control, and maintenance decision-making. In the overall structural analysis of roads, the influence of the self-weight of the pavement structure layer on the roadbed needs to be considered when determining the resilient modulus of the roadbed. However, the existing roadbed modulus test methods do not consider this aspect sufficiently.

[0003] At present, the test methods for the resilient modulus of roadbeds mainly include two categories: indoor tests and outdoor tests. Indoor tests mainly include static triaxial tests and dynamic triaxial tests. Outdoor tests include the plate bearing method, the Benkelman beam deflection measurement method, the falling weight deflectometer method, and the portable falling weight deflectometer test method. The current "Field Test Regulations for Highway Subgrade and Pavement" (JTG E60-2008) uses the Benkelman beam deflectometer and the plate bearing to measure the deflection and resilient modulus of the roadbed and pavement respectively. However, both the Benkelman beam method and the plate bearing method are static detection methods, and can only measure the static deflection and static modulus of the roadbed and pavement. The influence of the self-weight of the pavement structure layer on the roadbed is not considered during the measurement, so that the measurement result cannot accurately represent the deformation response characteristics and resilient modulus of the roadbed under the actual service state. Moreover, these methods have problems such as low test efficiency, poor convenience, large human influence factors, and large data discreteness, and are difficult to meet the needs of accurate and rapid detection in highway engineering. The falling weight deflectometer uses the impact load generated by a heavy hammer freely falling on the bearing plate to simulate traffic load, and measures the deformation of the roadbed under the impact load through a displacement sensor. However, the test data is unstable and the test reproducibility is not high. Therefore, it is mainly used for pavement performance evaluation and cannot be used for roadbed modulus tests.

[0004] Indoor triaxial tests require complex equipment and skilled personnel, and there are differences between the measured results and the field test results. Small changes in the resilient modulus of the roadbed will have a greater impact on the design of the upper pavement structure, making the pavement design too wasteful or unsafe. The plate bearing method applies the load at a slow speed and is a static load; the falling weight deflectometer applies a one-time impact load. However, the actual roadbed is subjected to the repeated action of traffic loads during movement and is also subjected to the action of the self-weight load of the pavement. The loads applied by the existing test methods are different from the loads borne by the actual roadbed, resulting in the fact that the deformation response characteristics and resilient modulus of the roadbed obtained from the tests cannot truly reflect the anti-deformation characteristics of the roadbed, directly affecting the accuracy and scientificity of the measurement of the deflection and resilient modulus of the roadbed and pavement, and making it difficult to scientifically evaluate the structural resistance and load response of the roadbed and pavement. Summary of the Invention

[0005] In order to solve the above technical problems, the object of the present invention is to provide a dynamic resilient modulus test method for simulating the actual service state of a subgrade, and the specific technical solution adopted is as follows:

[0006] The present invention provides a dynamic resilient modulus test method for simulating the actual service state of a subgrade, and this method includes the following steps:

[0007] Set a vertically downward load on the soil subgrade in the test software, set different loading frequencies and repetition times, start the servo control system for testing, and collect the monitoring data during the test. The monitoring data includes: the measuring spacing of the displacement sensor on the load plate, the load plate pressure, the load plate size, the collar size, and the loading frequency; the test process includes a first stage and a second stage; among them, the first stage is the stage without simulating the self-weight of the pavement structure, and the second stage is the stage of simulating the self-weight of the pavement structure using the collar;

[0008] According to the variation relationship between the load plate size, loading frequency, and dynamic resilient modulus of the soil subgrade in the first stage, obtain the dynamic resilient modulus of different-sized load plates at different loading frequencies; among them, the dynamic resilient modulus of the soil subgrade during the test is calculated based on the load plate pressure, the average amplitude of the recoverable axial deformation in the loading cycle, and the said measuring spacing;

[0009] Combined with the dynamic resilient modulus of different-sized load plates at different loading frequencies, according to the dynamic resilient modulus of different-sized load plates and different-sized collars at different loading frequencies in the second stage, obtain a subgrade dynamic modulus prediction model under the influence of the self-weight of the structural layer;

[0010] Use the subgrade dynamic modulus prediction model to predict the dynamic resilient modulus values of the subgrade top surface under different loading frequencies for different load plate sizes and collar sizes.

[0011] Preferably, calculating the dynamic resilient modulus of the soil subgrade according to the load plate pressure, the average amplitude of the recoverable axial deformation in the loading cycle, and the said measuring spacing includes:

[0012] Calculate the dynamic resilient modulus of the soil subgrade using the following formula:

[0013]

[0014] Among them, |E * | represents the dynamic resilient modulus of the soil subgrade, P i represents the load plate pressure, A represents the radial cross-sectional area of the load plate, l0 represents the measuring spacing of the displacement sensor on the load plate, and Δ i represents the average amplitude of the recoverable axial deformation in the loading cycle.

[0015] Preferably, the dynamic resilience moduli of bearing plates of different sizes at different loading frequencies are as follows:

[0016] For φ5cm, E = 12083.222 + (815.894 - 120083.222) / (1 + exp((x - 12.348) / dx));

[0017] For φ10cm, E = 8880.627 + (380.644 - 8880.627) / (1 + exp((x - 12.348) / dx));

[0018] For φ15cm, E = 4138.053 + (179.421 - 4138.053) / (1 + exp((x - 12.344) / dx));

[0019] For φ20cm, E = 2300.606 + (133.554 - 2300.606) / (1 + exp((x - 12.308) / dx));

[0020] For φ30cm, E = 2167.348 + (105.245 - 2167.348) / (1 + exp((x - 12.339) / dx));

[0021] For φ40cm, E = 1609.726 + (76.717 - 1609.726) / (1 + exp((x - 12.337) / dx));

[0022] Among them, φ5cm E represents the dynamic resilience modulus at different loading frequencies when the bearing plate size is 5cm, φ10cm E represents the dynamic resilience modulus at different loading frequencies when the bearing plate size is 10cm, φ15cm E represents the dynamic resilience modulus at different loading frequencies when the bearing plate size is 15cm, φ20cm E represents the dynamic resilience modulus at different loading frequencies when the bearing plate size is 20cm, φ30cm E represents the dynamic resilience modulus at different loading frequencies when the bearing plate size is 30cm, φ40cm E represents the dynamic resilience modulus at different loading frequencies when the bearing plate size is 40cm, x represents the loading frequency, e represents the natural constant, and dx represents the differentiation of x.

[0023] Preferably, the dynamic resilient modulus values of the subgrade top surface under different loading frequencies for different bearing plate sizes and collar sizes are as follows:

[0024]

[0025] Among them, E 20d represents the dynamic resilient modulus value of the subgrade top surface at different loading frequencies when the bearing plate size is 20cm and the collar width is 50cm, E 30dIt represents the dynamic resilient modulus values of the subgrade top surface under different loading frequencies with a bearing plate size of 30 cm and a collar width of 35 cm. f represents the loading frequency, e represents the natural constant, and df represents the differentiation of f.

[0026] The present invention has at least the following beneficial effects:

[0027] The present invention conducts tests on the dynamic resilient modulus of the subgrade under different sizes of bearing plates by setting up test equipment with different loading frequencies and repetition times to determine the influence of the loading frequency and the bearing plate size on the dynamic modulus of the subgrade. At the same time, in order to simulate the influence of the self-weight of the pavement structure layer on the subgrade modulus, tests on the dynamic modulus of the subgrade under different collar sizes are carried out. A prediction model for the dynamic modulus of the subgrade considering the influence of the self-weight of the structure layer is established to truly simulate the combined influence of the subgrade under repeated traffic loads and the self-weight of the pavement during actual service. This enables the measured subgrade deformation response characteristics and resilient modulus to truly reflect the anti-deformation characteristics of the subgrade, providing a basis for improving the effectiveness and reliability of asphalt pavement structure design, and having certain theoretical and engineering application values. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 It is a flowchart of a method for testing the dynamic resilient modulus to simulate the actual service state of the subgrade provided by an embodiment of the present invention;

[0030] Figure 2 It is a loading schematic diagram for simulating the self-weight load of the pavement;

[0031] Figure 3 It is a diagram of the equivalent resilient modulus of the subgrade top surface under different bearing plate sizes under dynamic load;

[0032] Figure 4 It is a fitting diagram of the equivalent resilient modulus of the subgrade top surface under different bearing plate sizes under dynamic load;

[0033] Figure 5 It is a diagram of the equivalent resilient modulus of the subgrade top surface under different sizes of bearing plates under static load;

[0034] Figure 6 It is a diagram of the static resilient modulus of the subgrade top surface for bearing plates with diameters of Φ10 cm, Φ20 cm, and Φ30 cm under the same collar width;

[0035] Figure 7It is the diagram of the dynamic resilient modulus of the subgrade top surface under different collar sizes of the load plates with diameters of Φ20 cm and Φ30 cm. Specific Embodiment

[0036] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following provides a detailed description of a dynamic resilient modulus test method for simulating the actual service state of a roadbed in combination with the accompanying drawings and preferred embodiments.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs.

[0038] The following specifically describes the specific solution of a dynamic resilient modulus test method for simulating the actual service state of a roadbed provided by the present invention in combination with the accompanying drawings.

[0039] An embodiment of a dynamic resilient modulus test method for simulating the actual service state of a roadbed:

[0040] This embodiment proposes a dynamic resilient modulus test method for simulating the actual service state of a roadbed. As Figure 1 shown, a dynamic resilient modulus test method for simulating the actual service state of a roadbed in this embodiment includes the following steps:

[0041] Step S1, set a vertically downward load on the subgrade in the test software, set different loading frequencies and repetition times, start the servo control system for testing, and collect the monitoring data during the test. The monitoring data includes: the measurement spacing of the displacement sensor on the load plate, the load plate pressure, the load plate size, the collar size, and the loading frequency; the test process includes a first stage and a second stage; among them, the first stage is the stage without simulating the self-weight of the pavement structure, and the second stage is the stage of simulating the self-weight of the pavement structure using the collar.

[0042] In this embodiment, low liquid limit clay is selected for the subgrade, and its technical indicators all meet the requirements of the "Test Regulations for Highway Engineering Aggregates" (JTG / E42-2005). According to the "Highway Geotechnical Test Regulations" (JTG-E40), the physical and mechanical property indexes of the soil sample are tested and shown in Table 1. When filling the roadbed, the moisture content should be controlled as much as possible between "optimum moisture content - 3% to + 2%", and the test should be carried out immediately after compaction.

[0043] Table 1 Physical Property Parameters of Low Liquid Limit Clay

[0044]

[0045] According to the "Field Test Regulations for Highway Subgrade and Pavement" (JTG 3450-2019), on the surface of the in-situ soil subgrade, loading is carried out using the combined test equipment for dynamic and static deflection and resilient modulus of subgrade and pavement, and the whole process data is collected through laser displacement sensors. The pressure on different collar rings is applied with a fixed stress by a jack to simulate the influence of pavement self-weight load on the soil subgrade, and a pressure sensor is used to determine the magnitude of the force.

[0046] Use the test equipment to preload at 2 MPa to make the loading plate in close contact with the soil subgrade. After stabilizing the pressure for 1 minute, unload to 0.5 MPa. After the unloading is stable for 1 minute, load at a loading speed of 2 kN / s until 13 MPa. Immediately, carry out dynamic load loading at the specified frequency. After the dynamic load loading is completed, unload at an unloading speed of 2 kN / s to 0.5 MPa. After the unloading is stable for 1 minute, continue to carry out dynamic load loading at the next frequency. After the last group of dynamic load loading is completed, unload to 0.5 MPa, stabilize the pressure for 1 minute, and then end the test.

[0047] In this embodiment, dynamic loading tests will be carried out under different loading plates, collar ring sizes, and loading frequencies, and considering different collar ring weights, in order to establish the relationship between the dynamic resilient modulus characteristics of the soil subgrade, the loading plate size, the collar ring size, and the loading frequency.

[0048] The dynamic load is applied by setting the vertically downward loading force in the test software, setting the loading waveform in the test software. The loading waveform is selected as a half-sine wave. Set the loading frequency and the number of repetitions in the test software. The standard test loading process is shown in Table 2. After setting the vertically downward loading force, frequency, and the number of repetitions, start the servo control system for testing. The data acquisition system real-time collects the measurement spacing of the displacement sensor on the loading plate, the loading plate pressure, and the corresponding loading frequency. The schematic diagram of dynamic load loading is shown in Figure 2 As shown in the figure, in the left loading schematic diagram, it is to simulate the load action situation during the traditional subgrade modulus determination, and only a concentrated load p is applied at the loading plate. In the right loading schematic diagram, it is to simulate the load action situation during the subgrade modulus determination of the method provided in this embodiment. The dynamic load is applied by setting the vertically downward loading force p in the test software of the combined test equipment for dynamic and static deflection and resilient modulus of subgrade and pavement. The pressure q on different collar rings is applied with a fixed stress by a jack to simulate the influence of pavement self-weight load on the soil subgrade, and a pressure sensor is used to determine the magnitude of the force.

[0049] Table 2 Number of repeated loadings at each loading frequency

[0050]

[0051] Sizes of the load-bearing plates: Φ5 cm, Φ10 cm, Φ15 cm, Φ20 cm, Φ20 cm, Φ30 cm, Φ40 cm; Sizes of the collars: inner diameter Φ10 cm, outer ring width 15 cm; inner diameter Φ20 cm, outer ring widths in sequence: 10 cm, 15 cm, 20 cm, 25 cm, 30 cm, 40 cm, 50 cm, 60 cm; inner diameter Φ30 cm, outer ring widths in sequence: 5 cm, 10 cm, 15 cm, 20 cm, 25 cm, 35 cm, 45 cm, 55 cm.

[0052] In this embodiment, a simulation process is used to determine the subgrade dynamic modulus prediction model under the influence of the self-weight of the structural layer, and thus the dynamic resilient modulus values of the subgrade top surface under different loading frequencies, different load-bearing plate sizes, and different collar sizes can be predicted. In this embodiment, the servo control system is started for testing. The entire testing process is divided into two stages. The first stage is the stage without simulating the self-weight of the pavement structure, and the second stage is the stage of using the collar to simulate the self-weight of the pavement structure. During the process of starting the servo control system for testing, various monitoring data during the testing process are collected. The monitoring data includes the measurement spacing of the displacement sensors on the load-bearing plate, the load-bearing plate pressure, the load-bearing plate size, the collar size, and the loading frequency.

[0053] Thus, all types of monitoring data during the testing process are collected in this embodiment.

[0054] Step S2: Obtain the dynamic resilient modulus of load-bearing plates of different sizes at different loading frequencies according to the variation relationship among the load-bearing plate size, loading frequency, and subgrade dynamic resilient modulus in the first stage; wherein, the subgrade dynamic resilient modulus during the testing process is calculated based on the load-bearing plate pressure, the average amplitude of the recovered axial deformation in the loading cycle, and the said measurement spacing.

[0055] Next, calculate the subgrade dynamic resilient modulus according to the monitoring data collected in the first stage:

[0056]

[0057] where, |E * | represents the subgrade dynamic resilient modulus, P i represents the load-bearing plate pressure (MPa), A represents the radial cross-sectional area of the load-bearing plate (mm 2 ), l0 represents the measurement spacing of the displacement sensors on the load-bearing plate (mm), Δ i represents the average amplitude of the recoverable axial deformation in the loading cycle (mm); σ0 represents the axial stress amplitude (MPa), and ε0 represents the axial recoverable strain amplitude (mm / mm).

[0058] Combining the above three formulas, the subgrade dynamic resilient modulus can be expressed as:

[0059]

[0060] Using the above formula, the dynamic resilient modulus of load - bearing plates with different sizes under different loading frequencies can be obtained.

[0061] By replacing the load - bearing plate of the dynamic and static deflection modulus joint test equipment for subgrade and pavement, the equivalent resilient modulus of the subgrade top surface under different sizes of load - bearing plates at different frequencies is measured. The equivalent resilient modulus of the subgrade top surface under different sizes of load - bearing plates at different frequencies under dynamic load is as Figure 3 shown.

[0062] From Figure 7 it can be concluded that the equivalent dynamic resilient modulus of the subgrade top surface under different load - bearing plate sizes decreases continuously with the increase of the load - bearing plate size, indicating that when the subgrade is subjected to an increasing load - bearing area, partial plasticity will occur on the basis of elastic deformation, resulting in a gradual decrease in the measured resilient modulus. Due to the different load - bearing plate sizes, the measured modulus values are different at different sizes, thus affecting the design of the pavement structure. Under the same load - bearing plate size, the equivalent dynamic resilient modulus of the subgrade top surface increases with the increase of the loading frequency. The dynamic resilient modulus of each load - bearing plate size at different loading frequencies is fitted, and the fitting diagram is shown in Figure 4 .

[0063] The dynamic resilient modulus of load - bearing plates with different sizes under different loading frequencies can be fitted by the Boltzmann function, and the correlation is relatively high. The dynamic resilient modulus of different load - bearing plate sizes at different frequencies can be predicted according to the fitting equation. The specific fitting equations are as follows:

[0064] For φ5cm, E = 12083.222+(815.894 - 120083.222) / (1 + exp((x - 12.348) / dx));

[0065] For φ10cm, E = 8880.627+(380.644 - 8880.627) / (1 + exp((x - 12.348) / dx));

[0066] For φ15cm, E = 4138.053+(179.421 - 4138.053) / (1 + exp((x - 12.344) / dx));

[0067] For φ20cm, E = 2300.606+(133.554 - 2300.606) / (1 + exp((x - 12.308) / dx));

[0068] For φ30cm, E = 2167.348+(105.245 - 2167.348) / (1 + exp((x - 12.339) / dx));

[0069] φ40cm E = 1609.726 + (76.717 - 1609.726) / (1 + exp((x - 12.337) / dx));

[0070] Among them, φ5cm E represents the dynamic resilient modulus at different loading frequencies when the bearing plate size is 5 cm, φ10cm E represents the dynamic resilient modulus at different loading frequencies when the bearing plate size is 10 cm, φ15cm E represents the dynamic resilient modulus at different loading frequencies when the bearing plate size is 15 cm, φ20cm E represents the dynamic resilient modulus at different loading frequencies when the bearing plate size is 20 cm, φ30cm E represents the dynamic resilient modulus at different loading frequencies when the bearing plate size is 30 cm, φ40cm E represents the dynamic resilient modulus at different loading frequencies when the bearing plate size is 40 cm, x represents the loading frequency, e represents the natural constant, and dx represents the differentiation of x.

[0071] Step S3: Combine the dynamic resilient moduli of bearing plates with different sizes at different loading frequencies, and obtain the subgrade dynamic modulus prediction model under the influence of the self-weight of the structural layer according to the dynamic resilient moduli of bearing plates with different sizes and collar rings with different sizes at different loading frequencies in the second stage.

[0072] To simulate the influence of the self-weight of the pavement structural layer, the thickness of the pavement structural layer is taken as 74 cm and the density is 2.3 g / cm 3 , and the pressure of the pavement structural layer is calculated to be 0.017 MPa. The reaction force is applied through a jack, and the force size is determined by a pressure sensor. From Figure 2 , it can be seen that the subgrade modulus begins to converge when the bearing plate is Φ20 cm. Therefore, in the following, this embodiment mainly studies the bearing plates Φ20 cm and Φ30 cm. The dynamic resilient modulus diagrams of the bearing plates Φ20 cm and Φ30 cm under different frequencies and different collar ring sizes are as shown in Figure 5 and Figure 6 .

[0073] From Figure 5 and Figure 6 , it can be seen that under the dynamic load, the dynamic resilient modulus increases continuously with the increase of the collar ring size. When the ring width increases to a certain extent, the change of the subgrade dynamic resilient modulus value gradually tends to be stable and approaches a certain limit value; when the collar ring size is the same, the dynamic resilient modulus on the top surface of the subgrade increases with the increase of the loading frequency. Under the bearing plate Φ20 cm, the change of the dynamic modulus value tends to be stable when the ring width is 50 cm; under the bearing plate Φ30 cm, the change of the dynamic modulus value tends to be stable when the ring width is 35 cm.

[0074] For the dynamic moduli under the bearing plate Φ30 cm with a collar ring width of 35 cm and the bearing plate Φ20 cm with a collar ring width of 50 cm, a fitting is performed, and the fitting curve is as shown in Figure 7 . The fitting equation is as follows:

[0075] E20 = 2337 - 2165 / (1 + exp((f - 12.306) / df));

[0076] E30 = 2184 - 2062 / (1 + exp((f - 12.339) / df));

[0077] Wherein, E20 is the dynamic resilient modulus value of the subgrade top surface when the bearing plate size is 20 cm, and E30 is the dynamic resilient modulus value of the subgrade top surface when the bearing plate size is 30 cm.

[0078] It should be noted that: in this embodiment, the correlation coefficient of the fitting equation during curve fitting is 0.99.

[0079] The dynamic resilient modulus of different-sized bearing plates and different-sized collar rings at different loading frequencies can be fitted by the Boltzmann function, and the correlation is relatively high. The predicted equations for the dynamic resilient modulus under the bearing plate Φ30 cm with a collar width of 35 cm and the bearing plate Φ20 cm with a collar width of 50 cm are obtained through fitting. The dynamic resilient modulus values of the subgrade top surface under the bearing plate Φ30 cm with a collar width of 35 cm and the bearing plate Φ20 cm with a collar width of 50 cm can be expressed as:

[0080]

[0081] Wherein, E 20d represents the dynamic resilient modulus value of the subgrade top surface at different loading frequencies with a bearing plate size of 20 cm and a collar width of 50 cm, and the unit is MPa; E 30d represents the dynamic resilient modulus value of the subgrade top surface at different loading frequencies with a bearing plate size of 30 cm and a collar width of 35 cm, and the unit is Mpa; f represents the loading frequency, and the unit is Hz; e represents the natural constant, and df represents the differentiation of f.

[0082] So far, by using the method provided in this embodiment, a prediction model for the subgrade dynamic modulus under the influence of the self-weight of the structural layer is obtained.

[0083] The dynamic resilient modulus of the soil subgrade gradually decreases as the bearing plate size increases, and begins to stabilize when the size reaches 30 cm. The dynamic resilient modulus of the soil subgrade gradually increases as the collar size increases, and begins to stabilize when the collar size reaches 50 cm for the bearing plate Φ20 cm; the collar size converges when it reaches 35 cm for the bearing plate Φ30 cm.

[0084] Step S4, using the subgrade dynamic modulus prediction model, predict the dynamic resilient modulus values of the subgrade top surface at different loading frequencies for different bearing plate sizes and collar sizes.

[0085] In this embodiment, a subgrade dynamic modulus prediction model is obtained in step S3. Using this model, the dynamic resilient modulus values of the subgrade top surface under different loading frequencies, different bearing plate sizes, and different collar sizes can be predicted.

[0086] Considering the influence of the self-weight of the pavement structure layer on the subgrade dynamic modulus, a more accurate dynamic modulus prediction model is established. This method reveals the variation law of the dynamic resilient modulus of the soil subgrade under different bearing plate sizes, different collar sizes, and different loading frequencies, and on this basis, a prediction model of the subgrade resilient modulus is established. The subgrade resilient modulus is closely related to the bearing plate size and the collar size. Considering the influence of the pavement self-weight, increasing the collar size or the load on the collar can effectively improve the subgrade resilient modulus.

[0087] In this embodiment, by setting up test equipment with different loading frequencies and repetition times, the dynamic resilient modulus test of the subgrade under different-sized bearing plates is carried out to determine the influence of the loading frequency and the bearing plate size on the subgrade dynamic modulus. At the same time, in order to simulate the influence of the self-weight of the pavement structure layer on the soil subgrade modulus, the dynamic modulus test of the subgrade under different collar sizes is carried out. A subgrade dynamic modulus prediction model considering the influence of the structure layer self-weight is established to truly simulate the combined influence of repeated traffic loads and pavement self-weight on the subgrade during actual service. This makes the measured subgrade deformation response characteristics and resilient modulus truly reflect the anti-deformation characteristics of the subgrade, providing a basis for improving the effectiveness and reliability of asphalt pavement structure design, and having certain theoretical and engineering application values.

[0088] The method provided in this embodiment obtains the correlation between the bearing plate size, the collar size, the loading frequency, and the dynamic resilient modulus of the soil subgrade top surface. At the same time, a corresponding resilient modulus prediction model is established. The proposed correlation of the dynamic resilient modulus and its prediction model have high reference value for predicting the resilient modulus of the soil subgrade in the actual structure and subgrade design. The method provided in this embodiment can not only simulate the influence of the self-weight of the pavement structure layer on the soil subgrade modulus, but also more truly characterize the influence of repeated traffic loads on the subgrade deformation response and resilient modulus under the actual service state of the subgrade, thereby providing a reference for subgrade design and construction and a basis for improving the effectiveness and reliability of pavement structure design.

[0089] It should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A dynamic rebound modulus test method simulating the actual service state of a roadbed, characterized in that: The method comprises the following steps: In the test software, a vertical downward loading force is set for the soil foundation, different loading frequencies and repetition times are set, the servo control system is started for testing, and monitoring data during the test is collected. The monitoring data includes: the measurement spacing of the displacement sensor on the bearing plate, the bearing plate pressure, the bearing plate size, the ring size and the loading frequency; the test process includes the first stage and the second stage; the first stage is the stage without simulating the self-weight of the pavement structure, and the second stage is the stage of simulating the self-weight of the pavement structure by using the ring; According to the changing relationship between the bearing plate size, loading frequency and dynamic elastic modulus of the soil foundation in the first stage, the dynamic elastic modulus of bearing plates of different sizes at different loading frequencies is obtained; wherein the dynamic elastic modulus of the soil foundation during the test is calculated based on the bearing plate pressure, the average amplitude of the recoverable axial deformation in the loading cycle, and the measurement interval; Combined with the dynamic rebound modulus of bearing plates of different sizes at different loading frequencies, and according to the dynamic rebound modulus of bearing plates of different sizes and collars of different sizes at different loading frequencies in the second stage, the dynamic modulus estimation model of the roadbed under the influence of the deadweight of the structural layer is obtained; The roadbed dynamic modulus prediction model is used to predict the dynamic rebound modulus values ​​of the roadbed top surface under different loading frequencies and different bearing plate sizes and collar sizes.

2. The method for testing the dynamic modulus of elasticity of a roadbed simulating the actual service state according to claim 1, characterized in that: The dynamic modulus of resilience of the soil foundation is calculated based on the bearing plate pressure, the average amplitude of the recoverable axial deformation in the loading cycle, and the measurement interval, including: The dynamic modulus of resilience of the soil foundation is calculated using the following formula: Among them, |E * | represents the dynamic rebound modulus of soil foundation, P i represents the load-bearing plate pressure, A represents the radial cross-sectional area of ​​the load-bearing plate, l0 represents the measurement spacing of the displacement sensor on the load-bearing plate, Δ i Represents the average amplitude of recoverable axial deformation during the loading cycle.

3. The method for testing the dynamic modulus of elasticity of a roadbed simulating the actual service state according to claim 1, characterized in that: The dynamic rebound modulus of bearing plates of different sizes at different loading frequencies is: Among them, φ5cm E represents the dynamic rebound modulus at different loading frequencies when the bearing plate size is 5cm, φ10cm E represents the dynamic rebound modulus at different loading frequencies when the bearing plate size is 10cm, φ15cm E represents the dynamic rebound modulus at different loading frequencies when the bearing plate size is 15cm, φ20cm E represents the dynamic rebound modulus at different loading frequencies when the bearing plate size is 20cm, φ30cm E represents the dynamic rebound modulus at different loading frequencies when the bearing plate size is 30cm, φ40cm E represents the dynamic rebound modulus at different loading frequencies when the bearing plate size is 40cm, x represents the loading frequency, e represents the natural constant, and dx represents the differentiation of x.

4. The method for testing the dynamic modulus of elasticity simulating the actual service state of a roadbed according to claim 1, characterized in that: The dynamic rebound modulus of the roadbed top surface under different loading frequencies and different bearing plate sizes and ring sizes is: Among them, E 20d It represents the dynamic rebound modulus of the top surface of the roadbed under different loading frequencies when the bearing plate size is 20 cm and the ring width is 50 cm. 30d It represents the dynamic rebound modulus of the top surface of the roadbed under different loading frequencies when the bearing plate size is 30 cm and the ring width is 35 cm. f represents the loading frequency, e represents the natural constant, and df represents the differentiation of f.

Images