Roadbed soil rebound modulus estimation method considering wide area state

Abstract

The invention discloses a roadbed soil rebound modulus estimation method considering a wide-area state. The method comprises the following specific steps: firstly, determining roadbed soil dynamic rebound modulus test parameters under minimum deviatoric stress and carrying out a roadbed soil dynamic rebound modulus test; and then constructing a roadbed soil rebound modulus estimation model considering the wide-area state based on the obtained rebound modulus data. The roadbed soil dynamic performance test under the wide-area stress state is established, and the problem that an existing test method cannot effectively simulate the actual stress state of a static area in a roadbed structure is solved. According to the method, the prediction accuracy of the rebound modulus of the roadbed soil at the stress boundary is improved, the prediction precision of the dynamic rebound modulus of the overall roadbed soil is further improved, and a solid foundation is provided for improvement of the durability of road engineering.

Description

Technical Field

[0001] The present invention belongs to the technical field of road engineering, and particularly relates to a method for predicting the resilient modulus of subgrade soil considering wide-area conditions. Background Art

[0002] In recent years, with the rapid advancement of infrastructure construction, the problem of insufficient durability of road engineering has gradually emerged. Compared with the obvious pavement damage, subgrade diseases often exhibit characteristics such as "strong concealment, gradual development, and indirect influence". Among the various design parameters of the subgrade, the dynamic resilient modulus of the subgrade is an important index for pavement structure design. Objectively and accurately obtaining the dynamic resilient modulus of the subgrade is the key to carrying out research on the theory and methods of durable road design.

[0003] The current resilient modulus prediction models can cover most parts of the subgrade, but neither the static resilient modulus nor the inherent modulus can be covered by the current prediction models. Therefore, conducting research on the resilient modulus of subgrade soil at the stress boundary can further improve the overall prediction accuracy of the dynamic resilient modulus of subgrade soil. The existing test methods for the resilient modulus of subgrade soil cannot effectively simulate the actual stress state in the static area of the subgrade structure. The traditional prediction model for the dynamic resilient modulus of subgrade soil based on the power function cannot accurately describe the mechanical properties of the subgrade structure in the static area. It is very necessary to conduct experimental research on the resilient modulus of the subgrade structure in the static area. Summary of the Invention

[0004] The purpose of the embodiments of the present invention is to provide a method for predicting the resilient modulus of subgrade soil considering wide-area conditions, so as to accurately measure the resilient modulus of subgrade soil in the static area, thereby effectively improving the overall prediction accuracy of the dynamic resilient modulus of subgrade soil.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is a method for predicting the resilient modulus of subgrade soil considering wide-area conditions, which is specifically carried out according to the following steps:

[0006] S1. Determine the test parameters of the dynamic resilient modulus of subgrade soil under extremely small deviator stress;

[0007] S2. Conduct the dynamic resilient modulus test of subgrade soil;

[0008] S3. Construct a prediction model for the resilient modulus of subgrade soil considering wide-area conditions based on the resilient modulus data obtained in S1 and S2.

[0009] Further, the specific steps of S1 are as follows:

[0010] S101. Analyze the resilient modulus characteristics of subgrade soil to determine the relationship between the static modulus of subgrade soil, the fixed contact stress, and the confining pressure;

[0011] S102. Determine the test parameters of the dynamic resilient modulus of subgrade soil under extremely small deviator stress based on the relationship between the static modulus of subgrade soil, fixed contact stress, and confining pressure.

[0012] Further, the test parameters of the dynamic resilient modulus in S102 include: confining pressure σ3, contact stress σ c and cyclic stress σ d .

[0013] Further, S2 is specifically carried out according to the following steps:

[0014] S201. Take the test soil, air it, break it up, and sieve it.

[0015] S202. Calculate the mass proportion of each soil sample according to the particle screening results and dry it, then add distilled water to prepare the soil sample with the target moisture content, and put it into a double-layer sealed bag and let it stand for 12 - 24 h to ensure the uniformity of the soil sample moisture content.

[0016] S203. Use a hydraulic servo pressure testing machine to statically press the test soil in five layers to obtain a triaxial specimen.

[0017] S204. Use a dynamic triaxial test system to conduct a dynamic resilient modulus test on the triaxial specimen obtained in S203.

[0018] Further, during the sieving process of S201, sieve the soil sample through 20 mm, 10 mm, 5 mm, and 2 mm sieves respectively to obtain four particle size ranges: 10 - 20 mm, 5 - 10 mm, 2 - 5 mm, and less than 2 mm.

[0019] Further, the specific process of the five-layer static pressing in S203 is as follows: First, wipe the split mold of the triaxial specimen clean and evenly apply vaseline on its inner surface; then assemble the mold and place a filter paper on the bottom cushion block; then divide the required mass of the soil sample into five equal parts and add them to the mold in sequence, and use a static press to compact it after each layer is added; perform surface roughening treatment after each layer of static pressing is completed; after the static pressing of each layer of the specimen is completed, disassemble the split mold, take out the specimen, and seal it with plastic wrap for 12 - 24 hours to obtain a triaxial specimen.

[0020] Further, during the five-layer static pressing process, the mass m i of each layer of soil sample is:

[0021] m i = ρ dmax × K × V × (1 + 0.01w) / 5 (1)

[0022] Where: K is the compaction degree of the specimen; ρ dmax is the maximum dry density; V is the volume of the specimen; w is the moisture content of the specimen.

[0023] Further, the specific process of S203 is as follows:

[0024] S2031. First, determine whether the air inlet, loading frame, and sealing of the triaxial chamber of the triaxial test system are normal and whether the triaxial specimen is intact.

[0025] S2032. Place filter paper and permeable stones on the top and bottom of the triaxial specimen in sequence, and then put the rubber membrane on the triaxial specimen through the air extraction device and the steel sleeve.

[0026] S2033. Put two rubber rings on the upper and lower parts of the rubber membrane respectively, and make the rubber rings fit in the grooves to seal and prevent air from entering the rubber membrane.

[0027] S2034. Place the assembled triaxial chamber on the loading frame, fix it and align it with the center of the loading rod, and insert the confining pressure tube.

[0028] S2035. Turn on the triaxial test system, input the parameters and loading sequence determined by S1. During the preloading process of the triaxial test, if the total vertical permanent strain of the specimen reaches 5%, stop the test, analyze the reasons and remold the specimen. After the formal loading of the triaxial test is completed, remove the confining pressure and servo loading, and extract the test data.

[0029] Further, the resilient modulus M of the subgrade soil in S3 R The specific prediction model is as follows:

[0030]

[0031] In the formula, k1, k2, k3, and k4 are model parameters; θ is the volumetric stress, θ = 3σ3 + σ S + σ d ; σ3 is the confining pressure; σ S is the contact stress; σ d is the cyclic stress; τ D is the octahedral shear stress of the dynamic effect τ S is the octahedral shear stress of the static effect 101 is the standard atmospheric pressure in Pa.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows: By establishing a test on the dynamic performance of subgrade soil under a wide-area stress state, the present invention successfully solves the problem that the existing test methods cannot effectively simulate the actual stress state in the static area inside the subgrade structure. At the same time, in view of the situation that the traditional prediction model of the dynamic resilient modulus of subgrade soil based on the power function cannot accurately describe the mechanical properties of the subgrade structure in the static area, an improved prediction model of the dynamic resilient modulus of subgrade soil under a wide-area stress state is proposed. This innovation not only significantly improves the accuracy of predicting the resilient modulus of subgrade soil at the stress boundary, but also further improves the prediction accuracy of the overall dynamic resilient modulus of subgrade soil, providing a solid foundation for enhancing the durability of road engineering. Through specialized experimental research on the static area of the subgrade structure, this technology can obtain the dynamic resilient modulus of the subgrade more objectively and accurately, thus promoting the development of the theory and method of durable road design, and having important practical value and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for 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 be obtained based on these drawings.

[0034] Figure 1 is the loading mode diagram of the subgrade dynamic modulus;

[0035] Figure 2 is the loading mode diagram of the subgrade static modulus;

[0036] Figure 3 is the definition diagram of the static resilient modulus inside the subgrade; (a) is the relationship diagram between the resilient modulus and the cyclic stress, (b) is the relationship diagram between the resilient modulus and the load application duration; (c) is the relationship diagram between the subgrade resilient modulus and the load;

[0037] Figure 4 is the experimental diagram of the resilient modulus of subgrade soil under extremely small deviator stress in this embodiment; (a) is σ3 = 60 kPa, (b) is σ3 = 45 kPa; (c) is σ3 = 30 kPa; (d) is σ3 = 15 kPa;

[0038] Figure 5 is the experimental diagram of the inherent modulus of subgrade soil in this embodiment;

[0039] Figure 6 is the fitting result diagram of the classical three-parameter model;

[0040] Figure 7 is the comparison diagram of the prediction results between this embodiment and the NCHRP1-28A model;

[0041] Figure 8 This is a comparison chart of the predicted modulus and the measured modulus in this embodiment. Specific Embodiment

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0043] This embodiment provides a method for predicting the resilient modulus of subgrade soil considering wide-area conditions, which is specifically carried out according to the following steps:

[0044] In this embodiment, most of the interior of the subgrade belongs to the static force action area. A preliminary exploration is carried out on the resilient modulus of this area, which involves the static resilient modulus in the subgrade and the dynamic resilient modulus of subgrade soil under extremely small deviator stress.

[0045] In the prior art, it is generally considered that the resilient modulus of the subgrade measured under the action of a pulse load is called the dynamic resilient modulus (such as Figure 1 ), and the resilient modulus of the subgrade measured under the action of a constant load is called the static resilient modulus (such as Figure 2 ). If these two loading modes are directly applied to the top surface of the subgrade, they are the PFWD test and the bearing plate test methods.

[0046] It is generally considered that the shallow layer of the subgrade affected by dynamic loads is called the dynamic influence area, that is, the subgrade working area; while the deep layer of the subgrade is basically not affected by dynamic loads and is considered as the static influence area. To study the characteristics of subgrade soil in the dynamic and static influence areas of the subgrade, some scholars have carried out tests on the dynamic and static resilient moduli of subgrade soil, that is, using the dynamic modulus loading method to obtain the prediction model of the dynamic resilient modulus of subgrade soil or using the static modulus loading method to obtain the prediction model of the static resilient modulus. Furthermore, combined with the division of the subgrade working area, the dynamic resilient modulus is used for calculation in the dynamic influence area, and the static resilient modulus is used for calculation in the static influence area.

[0047] When the loading method of the static modulus is directly applied to the surface of the subgrade, its applicability is not controversial; however, when this method is used to evaluate the static resilient modulus inside the subgrade, it shows certain limitations and cannot accurately reflect the mechanical characteristics under actual working conditions. In fact, using the static modulus to measure the resilient deflection of the subgrade reflects the resilient deformation situation after all the subgrade soil above this depth is completely unloaded, rather than the actual stress state of the subgrade soil at this depth. However, if unloading is not carried out, the modulus cannot be accurately measured, because by definition, the modulus is the ratio of stress change to strain change.

[0048] Such as Figure 3As shown in (c), the subgrade is subjected to the combined action of overlying static load and moving vehicle load. Moreover, the dynamic force decreases with increasing depth, and the loading duration becomes longer. Therefore, the true static modulus inside the subgrade should be determined under fixed contact stress and confining pressure while continuously reducing the magnitude of the cyclic stress. The magnitude of the static modulus is approximately the intersection point of the reverse extension line of the resilient modulus and the y-axis (as shown in Figure 3 (a)). Or it is equivalent to the limit value of the dynamic modulus under the action of an infinitely long-term load (as shown in Figure 3 (b)).

[0049] S1. Develop a test plan for the dynamic resilient modulus of subgrade soil under extremely small deviator stress

[0050] S101. The subgrade is vertically subjected to the combined action of overlying static force and moving vehicle load. When the true static modulus inside the subgrade is under fixed contact stress and confining pressure with continuously decreasing cyclic stress, the magnitude of the static modulus is the intersection point of the reverse extension line of the resilient modulus and the y-axis (as shown in Figure 3 (a)).

[0051] S102. Determine the confining pressure σ3, contact stress σ c and cyclic stress σ d and other parameters for the resilient modulus test of subgrade soil.

[0052] S2. Conduct the dynamic resilient modulus test of subgrade soil

[0053] S201. Retrieve the test soil, air-dry it, break it into pieces, and sieve it. To ensure that the gradation of the triaxial test is the same as that of the undisturbed soil, the soil sample is sieved through 20 mm, 10 mm, 5 mm, and 2 mm sieves respectively to obtain four gradations of particle sizes: 10 - 20 mm, 5 - 10 mm, 2 - 5 mm, and less than 2 mm;

[0054] S202. Calculate the mass ratio of each gradation of soil sample according to the particle size screening results, dry it, then add distilled water to prepare a soil sample with the target moisture content, and put it into a double-layer sealed bag for 12 - 24 h of moisture conditioning to ensure uniform moisture content of the soil sample.

[0055] S203. Use a hydraulic servo pressure testing machine to statically press the specimen in five layers. The mass of each layer of soil sample is calculated according to Equation (1):

[0056] m i =ρ dmax ×K×V×(1 + 0.01w) / 5 (1)

[0057] In the formula: m i is the mass of each layer of soil sample, g; K is the compaction degree of the specimen, %; ρ dmax is the maximum dry density, g / cm 3 ; V is the volume of the specimen, cm 3 ; w is the moisture content of the specimen, %.

[0058] During the compaction process, first wipe the split mold of the specimen clean and evenly apply vaseline on its inner surface to facilitate the subsequent demolding of the specimen. Then, assemble the mold and place a filter paper on the bottom cushion block. Next, divide the mass of the soil sample required according to the working conditions into five equal parts and add them to the mold in sequence. After each layer is added, use a static press to compact it. To avoid stratification of the soil sample during the compaction process, roughen the surface after each layer of static compaction is completed to prevent stratification or weak surfaces from appearing in the specimen. After the static compaction of each layer of the specimen is completed, disassemble the split mold to take out the specimen and seal it with plastic wrap for 12 - 24h to obtain a triaxial specimen.

[0059] S204. Conduct the dynamic resilient modulus test using the Dynatriax100 / 14 dynamic triaxial test system.

[0060] S2041. Check the Dynatriax100 / 14 large - scale dynamic triaxial test system. First, determine whether the actuator can work normally, check whether the air inlet leaks, whether the loading frame is fixed, whether the triaxial cell is well - sealed, and whether the triaxial specimen is intact.

[0061] S2042. Place filter paper and permeable stones on the top and bottom of the specimen in sequence, and then put the rubber membrane on the triaxial specimen through the air - extraction equipment and the steel sleeve.

[0062] S2043. Put two rubber rings on the upper and lower parts of the rubber membrane respectively, so that the rubber rings are sleeved at the grooves to seal and prevent air from entering the rubber membrane.

[0063] S2044. Place the assembled triaxial cell on the loading frame, fix it and align it with the center of the loading rod. Insert the confining pressure tube.

[0064] S2045. Open the air valve, the lifting device of the loading frame, the air pressure regulating equipment, the control system, and the computer in sequence, start the triaxial test system, input the test parameters and the loading sequence, install the LVDT displacement pen, and start the triaxial test. During the pre - loading process, if the total vertical permanent strain of the specimen reaches 5%, the test should be stopped to analyze the reasons and remold the specimen. After the formal loading of the triaxial test is completed, release the confining pressure and the servo loading, and extract the test data.

[0065] S3. Construct a prediction model for the resilient modulus of subgrade soil considering the wide - area state

[0066] S301. Use the gene expression programming (GEP) algorithm to propose a prediction model for the resilient modulus M of subgrade soil in the wide - area state R The prediction model is shown in Equation (2).

[0067]

[0068] where k1, k2, k3, and k4 are model parameters; θ is the volumetric stress, θ = 3σ3 + σ S + σ d ; σ3 is the confining pressure; σ S is the contact stress; σ d is the cyclic stress; τ D is the octahedral shear stress of the dynamic effect τ S is the octahedral shear stress of the static effect 101 is the standard atmospheric pressure in Pa.

[0069] Calculate the corresponding stress state at each point in the subgrade structure and substitute it into the subgrade soil resilient modulus prediction model obtained by formula (2), then the resilient modulus value at this point can be calculated.

[0070] The present invention improves the existing test scheme that cannot effectively simulate the actual stress state in the static zone of the subgrade structure, and the traditional subgrade soil dynamic resilient modulus prediction model based on the power function cannot accurately describe the mechanical properties of the subgrade structure in the static zone.

[0071] Embodiment

[0072] Carry out extremely small dynamic deviator stress tests using Changsha clay, and the basic physical properties of the soil samples are shown in Table 1.

[0073] Table 1 Basic Physical Properties of Changsha Clay

[0074]

[0075] Set σ3 = 60 kPa, σ c = 12 kPa; σ3 = 60 kPa, σ c = 18 kPa; σ3 = 60 kPa, σ c = 30 kPa; σ3 = 60 kPa, σ c = 42 kPa; σ3 = 60 kPa, σ c = 60 kPa; σ3 = 60 kPa, σ c = 90 kPa;

[0076] σ3 = 45 kPa, σ c = 9 kPa; σ3 = 45 kPa, σ c = 13.5 kPa; σ3 = 45 kPa, σ c = 22.5 kPa; σ3 = 45 kPa, σ c = 31.5 kPa;

[0077] σ3 = 45 kPa, σ c = 45 kPa; σ3 = 45 kPa, σ c = 67.5 kPa;

[0078] σ3 = 30 kPa, σ c = 6 kPa; σ3 = 30 kPa, σ c = 9 kPa; σ3 = 30 kPa, σ c = 15 kPa; σ3 = 30 kPa, σ c = 21 kPa;

[0079] σ3 = 30 kPa, σ c = 30 kPa; σ3 = 30 kPa, σ c = 45 kPa;

[0080] σ3 = 15 kPa, σ c = 3 kPa; σ3 = 15 kPa, σ c = 4.5 kPa; σ3 = 15 kPa, σ c = 7.5 kPa; σ3 = 15 kPa, σ c = 10.5 kPa;

[0081] σ3 = 15 kPa, σ c = 15 kPa; σ3 = 15 kPa, σ c = 22.5 kPa;

[0082] A total of 24 groups of σ3 and σ c ; Under each stress, the resilient modulus tests of subgrade soil were carried out respectively under σ d = 30, 25, 20, 15, 10, 5 kPa. The load application duration was taken as 100 ms, and the results are as Figure 4 (a) - (d) shown.

[0083] In the existing resilient modulus prediction models, without any load applied, their resilient moduli are all zero, that is, M R (σ3 = σ c = σ d = 0) = 0 MPa. Obviously, the subgrade soil also has a resilient modulus when there is no external force, and this modulus is called the "intrinsic modulus" of the subgrade soil.

[0084] The resilient modulus tests under the conditions of σ3 = 0 kPa and σ c = 2 kPa were carried out using Changsha clay as shown in Table 1, with σ d = 120, 90, 80, 70, 60, 50, 40, 30, 20, 15, 10, 5 kPa, and the results are as Figure 5 shown. It can be seen from Figure 5 that by extending the curve in the reverse direction, the approximate intrinsic modulus of the subgrade can be obtained as about 56 MPa. It can be seen that for the shallow subgrade, without the action of vehicle load, its resilient modulus is approximately 56 MPa.

[0085] The 24-level loading sequence of the resilient modulus in this embodiment is shown in Table 2. The resilient modulus tests of subgrade soil are carried out under σ d = 120, 90, 60, 30, 20, 15, 10, 5 kPa for each stress state (a total of 8 * 24 = 192 groups of sequences). The 28-level loading sequence is shown in Table 3 (28 groups of sequences), the inherent modulus loading sequence is shown in Table 4 (8 groups of sequences), and the T0194-2019 fine-grained soil dynamic resilient modulus loading sequence in the "Code for Highway Geotechnical Tests" (JTG 3430-2020) (16 groups of sequences) is shown in Table 5, with a total of 244 working conditions.

[0086] Table 2 24-level resilient modulus loading sequence

[0087]

[0088]

[0089] Table 3 28-level resilient modulus loading sequence

[0090]

[0091]

[0092] Table 4 Inherent modulus loading sequence

[0093]

[0094] Table 5 T0194-2019 loading sequence

[0095]

[0096] The 244 groups of loading sequence data in Tables 2 to 5 are respectively predicted using the classical three-parameter model and the results are as Figure 6 shown. It can be found that in the case of extremely small deviator stresses and subgrade soil moduli, the existing prediction models for the resilient modulus of subgrade soil considering the wide-area state have poor accuracy and do not meet the engineering accuracy requirements.

[0097] In this embodiment, the GEP algorithm is used to fit the 244 groups of sequences. The gene expression programming algorithm is a new type of adaptive evolutionary algorithm proposed by Ferreira on the basis of genetic algorithms and genetic programming. It has both the simplicity of the "fixed-length linear string" of genetic algorithms and the search ability of the "dynamic tree structure" of genetic programming. Similar to the genetic algorithm, the GEP algorithm mainly includes steps such as initializing the population, calculating fitness, selection, mutation, recombination, and transposition.

[0098] The prediction model fitted by GEP is shown in Equation (2)

[0099]

[0100] For the fitting results of the classic three-parameter model NCHRP1-28A and the prediction model found in this embodiment for 244 working conditions are as Figure 7 shown. It is found that due to considering the wide-area stress state, the prediction effect of the classic three-parameter model NCHRP1-28A is not ideal. Since the traditional model cannot consider the inherent modulus of the subgrade (the confining pressure, contact stress, and cyclic stress are all zero), and the resilient modulus under extremely small deviatoric stresses, this will inevitably lead to an unsatisfactory fitting effect. Therefore, in order to establish a prediction model for the resilient modulus that can consider the wide-area state, the GEP algorithm is used to find the prediction model shown in Equation (2). From Figure 7 it can be seen that the fitting result of the prediction model found by GEP is relatively ideal, and it can better predict the resilient modulus of subgrade soil considering the wide-area state.

[0101] In order to better illustrate the accuracy of the GEP model, the measured values of 244 groups of sequences are compared with the predicted values of the GEP model, as Figure 8 shown. By comparing the measured values of 244 groups of loading sequences with the predicted values of the GEP model, it is found that the fitting result of the prediction model found by GEP is relatively ideal, and it can better predict the resilient modulus of subgrade soil considering the wide-area state. It can be seen that the new model of the resilient modulus prediction model can well fit different soil types and different loading sequences. The new model can not only be compatible with the results of traditional loading sequences, but also has a better fitting accuracy than the traditional resilient modulus prediction model. Therefore, it is necessary to consider the wide-area state in the loading sequence and prediction model of the resilient modulus of subgrade soil, and propose a prediction model for the resilient modulus of subgrade soil considering the wide-area state.

[0102] Each embodiment in this specification is described in a related manner. The same or similar parts among the embodiments can be referred to each other, and the key points of each embodiment are the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0103] The above are only the preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are all included in the protection scope of the present invention.

Claims

1. A method for predicting the resilient modulus of subgrade soil considering wide-area states, characterized in that, The specific steps are as follows: S1. Determine the test parameters of the dynamic resilient modulus of subgrade soil under extremely small deviator stress; S2. Conduct the dynamic resilient modulus test of subgrade soil; S3. Based on the resilient modulus data obtained in S1 and S2, construct a prediction model for the resilient modulus of subgrade soil considering the wide-area state.

2. The method for predicting the resilient modulus of subgrade soil considering wide-area conditions according to claim 1, wherein The specific steps of S1 are as follows: S101. Analyze the resilient modulus characteristics of subgrade soil to determine the relationship between the static modulus of subgrade soil, fixed contact stress, and confining pressure; S102. Based on the relationship between the static modulus of subgrade soil, fixed contact stress, and confining pressure, determine the test parameters of the dynamic resilient modulus of subgrade soil under extremely small deviator stress.

3. The method for predicting the resilient modulus of subgrade soil considering wide-area conditions according to claim 2, characterized in that, The dynamic resilience modulus test parameters described in S102 include: confining pressure σ3, contact stress σ c and cyclic stress σ d .

4. A method for predicting the resilient modulus of subgrade soil considering wide-area conditions according to claim 1, characterized in that, The specific steps of S2 are as follows: S201. Take the test soil, dry it in the sun, break it up, and sieve it; S202. Calculate the mass ratio of each soil sample according to the particle screening results and dry it, then add distilled water to prepare the soil sample with the target moisture content, and put it into a double-layer sealed bag and stew it for 12 - 24 hours to ensure the uniformity of the soil sample moisture content; S203. Use a hydraulic servo pressure testing machine to statically press the test soil in five layers to obtain a triaxial specimen; S204. Use a dynamic triaxial test system to conduct a dynamic resilient modulus test on the triaxial specimen obtained in S203.

5. A method for predicting the resilient modulus of subgrade soil considering wide-area conditions according to claim 4, characterized in that, During the sieving process of S201, sieve the soil sample through 20mm, 10mm, 5mm, and 2mm sieves respectively to obtain four particle size ranges of 10 - 20mm, 5 - 10mm, 2 - 5mm, and less than 2mm.

6. The method for predicting the resilient modulus of subgrade soil considering wide-area conditions according to claim 4, characterized in that, The specific process of the five-layer static pressing in S203 is as follows: First, wipe the split mold of the triaxial specimen clean and evenly apply vaseline on its inner surface; then assemble the mold and place a filter paper on the bottom cushion block; then divide the required mass of the soil sample into five equal parts and add them to the mold in sequence, and use a static press to compact it after each layer is added; roughen the surface after each layer of static pressing is completed; after the static pressing of each layer of the specimen is completed, disassemble the split mold, take out the specimen, and seal it with plastic wrap for 12 - 24 hours to obtain a triaxial specimen.

7. The method for predicting the resilient modulus of subgrade soil considering wide-area conditions according to claim 6, wherein During the process of five-layer static pressure, the mass m of each soil sample i is as follows: m i = ρ dmax ×K×V×(1 + 0.01w) / 5 (1) Where: K is the compaction degree of the specimen; ρ dmax is the maximum dry density; V is the volume of the specimen; w is the water content of the specimen.

8. A method for predicting the resilient modulus of subgrade soil considering wide-area conditions according to claim 4, characterized in that The specific process of S203 is as follows: S2031. First, determine whether the air inlet, loading frame, and sealing of the triaxial test system are normal and whether the triaxial specimen is intact; S2032. Place filter paper and permeable stones on the top and bottom of the triaxial specimen in sequence, and then put the rubber membrane on the triaxial specimen through a pumping device and a steel sleeve; S2033. Put two rubber rings on the upper and lower parts of the rubber membrane respectively, so that the rubber rings are sleeved at the grooves to seal and prevent air from entering the rubber membrane; S2034. Place the assembled triaxial chamber on the loading frame, fix it and align it with the center of the loading rod, and insert the confining pressure tube; S2035. Turn on the triaxial test system, input the parameters and loading sequence determined in S1, and start the preloading process of the triaxial test. If the total vertical permanent strain of the specimen reaches 5% during the test, stop the test, analyze the reasons, and remold the specimen. When the formal loading of the triaxial test is completed, unload the confining pressure and servo loading, and extract the test data.

9. A method for predicting the resilient modulus of subgrade soil considering wide-area conditions according to claim 4, characterized in that, The resilient modulus M of the subgrade soil in S3 R The prediction model is specifically as follows: where k1, k2, k3, k4 are model parameters; θ is the bulk stress θ = 3σ3 + σ S + σ d ; σ3 is the confining pressure; σ S is the contact stress; σ d is the cyclic stress; τ D is the octahedral shear stress of the dynamic effect τ S is the octahedral shear stress of the static effect 101 is the standard atmospheric pressure.

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