Simulation analysis method for dirty ballast bed diseases under dynamic-melting action in spring melting period

Abstract

The invention provides a simulation analysis method for a dirty ballast bed disease under a power-melting effect in a spring melting period, and relates to the technical field of ballast bed disease simulation, and the method comprises the steps: collecting hourly temperature in the spring melting period, and settlement increment and dynamic load parameters of monitoring points before and after a train passes through, and obtaining dirty characteristics and mechanical property parameters; determining actual freeze-thaw cycle times and critical freeze-thaw cycle times, and calculating a freeze-thaw damage accumulation index; an accumulated settlement increment characteristic value is extracted to calculate a non-uniform settlement index, and the freeze-thaw fatigue life ratio is corrected for the first time in combination with the temperature average gradient; simulating two working conditions, calculating a bearing capacity attenuation index and a dynamic load acceleration factor, and secondarily correcting a freeze-thaw fatigue life ratio; and dividing disease risk grades. The method can adapt to complex working conditions of temperature transient-settlement non-uniformity, enables an evaluation result to be matched with actual disease development, can accurately evaluate the fatigue life under multi-factor coupling, and provides a judgment basis for disease grade division.

Description

Technical Field

[0001] The present invention relates to the technical field of simulation of dirty roadbed diseases, and in particular to a simulation analysis method of dirty roadbed diseases under the action of dynamic thawing during the spring thaw period. Background Art

[0002] During the spring thaw, contaminated roadbeds face the combined effects of freeze-thaw cycles, temperature gradients, and train dynamic loads. Traditional analysis methods often consider the effects of freeze-thaw or dynamic loads separately, failing to construct simulation models that couple these multiple factors. For example, they focus solely on temperature-induced frost heave and thaw settlement, while ignoring the increased fatigue damage caused by the combined effects of train dynamic loads. Furthermore, they fail to quantify the temporal correlation between the number of freeze-thaw cycles and dynamic loads, resulting in significant deviations between simulation results and actual operating conditions.

[0003] In the prior art, a method and device for identifying dirty roadbed defects during the spring thaw period, published as CN120105848A, establishes a discontinuous graded ligand cementation contact model through discrete element simulation, introduces a temperature-stiffness / strength coupling factor, and constructs a critical dynamic strain model based on large triaxial experimental data, thereby realizing the assessment of roadbed defects under the action of dynamic-melting coupling.

[0004] However, there are still the following deficiencies: As can be seen from the above statements, the data collection dimension is single, the model is static, and the multi-factor coupling effect is not considered; the fluctuations in the frequency of freeze-thaw cycles caused by hourly temperature changes during the spring thaw period, and the impact of uneven settlement of the roadbed surface on the bearing capacity are not considered. There is a lack of quantitative analysis of time-varying temperature fields and spatial deformations, which makes the model unable to adapt to the complex working conditions of "temperature transients-uneven settlements" during the spring thaw period, and the evaluation results are out of touch with the actual development of diseases; the independent effects of freeze-thaw damage and dynamic loads are not separated from the attenuation of bearing capacity to quantify the acceleration mechanism of the synergistic effect of the two, and it is difficult to accurately evaluate the fatigue life under multi-factor coupling, resulting in a lack of judgment basis for the classification of disease levels under multi-factor coupling.

[0005] The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the Invention

[0006] The purpose of the present invention is to provide a simulation analysis method for dirty roadbed diseases under the action of dynamic thawing during the spring thaw period to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions: A simulation analysis method for dirty roadbed damage under dynamic-thaw action during the spring thaw period, comprising the following steps: S1. Evenly spaced monitoring points are arranged along the track. Hourly temperatures are collected during the spring thaw period. The settlement increments at each monitoring point before and after a train passes are recorded and accumulated as cumulative settlement. Dynamic load parameters for the contaminated trackbed are simultaneously acquired. After the spring thaw period, contamination characteristics and mechanical property parameters are collected. The actual number of freeze-thaw cycles is determined based on the hourly temperatures. Freeze-thaw fatigue tests are conducted to plot the change in mechanical property parameters versus freeze-thaw cycle number, determine the critical number of freeze-thaw cycles, and calculate the freeze-thaw damage accumulation index. S2. Correcting the critical freeze-thaw cycle number based on soiling characteristics and mechanical property parameters, and calculating the freeze-thaw fatigue life ratio based on the actual freeze-thaw cycle number and the corrected critical freeze-thaw cycle number; S3. Extract the maximum, minimum, and average values ​​of the cumulative settlement increments at each monitoring point, calculate the uneven settlement index, calculate the temperature gradient based on the hourly temperature, and use this to make a correction to the freeze-thaw fatigue life ratio. S4. Simulate freeze-thaw conditions and freeze-thaw and dynamic load coupled conditions. Use different models to obtain the maximum contact force for each condition based on the freeze-thaw damage accumulation index. Calculate the bearing capacity attenuation index. Compare the attenuation difference between the coupled condition and the freeze-thaw condition to calculate the dynamic load acceleration factor. Combined with the primary freeze-thaw fatigue life ratio, perform a secondary correction on the freeze-thaw fatigue life ratio to obtain the secondary corrected freeze-thaw fatigue life ratio. S5. Classify the risk level of contaminated roadbed damage based on the secondary corrected freeze-thaw fatigue life ratio.

[0008] Furthermore, the dynamic load parameters include static load contact force and dynamic load amplitude, the dirt characteristic parameter is plasticity index, and the mechanical property parameter is compressive strength.

[0009] Furthermore, the actual number of freeze-thaw cycles is determined according to the hourly temperature. The specific steps and the formula are as follows: Setting the Freeze Threshold ; when It is considered as the freezing stage; when The melting stage is considered as the melting stage, in which is the hourly temperature, is the time variable of spring thaw period; Based on hourly temperature and freeze threshold , the effective freeze-thaw cycle process is defined as follows: When the hourly temperature The complete temperature fluctuation cycle from the melting stage to the freezing stage and then back to the melting stage is recorded as one effective freeze-thaw cycle process; Traverse all time points during the spring thaw period to obtain the actual number of freeze-thaw cycles; According to the mechanical properties parameters, the critical number of freeze-thaw cycles is determined through freeze-thaw fatigue tests, and the freeze-thaw damage accumulation index is calculated. The specific steps and the formula are as follows: Freezing process: Place the soiled roadbed material sample in a -20°C environment for 4 hours; Melting process: Heat to 20℃ and keep for 4 hours; Repeat the freezing and thawing process and record the number of cycles; After every 10 freeze-thaw cycles, the compressive strength test of the soiled roadbed material samples was conducted; When the compressive strength loss rate exceeds the preset threshold, it is determined to have reached a critical state: Draw a curve of freeze-thaw cycle number-compressive strength loss rate, and the horizontal axis corresponding to the intersection of the curve and the threshold horizontal line is the critical freeze-thaw cycle number; The freeze-thaw damage accumulation index is calculated based on the following formula: ; in, is the freeze-thaw damage accumulation index, is the actual number of freeze-thaw cycles, is the critical number of freeze-thaw cycles.

[0010] Furthermore, the critical number of freeze-thaw cycles was corrected based on the soiling characteristics and mechanical properties parameters collected after the spring thaw period, according to the following formula: ; ; ; in, is the corrected value of the critical freeze-thaw cycle number, Correction times for dirt, is the number of mechanical corrections, is the critical number of freeze-thaw cycles, 、 、 They are the plasticity index, strength influence coefficient and compressive strength collected after the spring thaw period. is the benchmark compressive strength; The freeze-thaw fatigue life ratio is calculated based on the actual number of freeze-thaw cycles and the correction value of the critical number of freeze-thaw cycles according to the following formula: ; in, is the freeze-thaw fatigue life ratio of the dirty roadbed.

[0011] Furthermore, the maximum, minimum and average values ​​of the cumulative settlement increments at each monitoring point were extracted to calculate the uneven settlement index. The temperature gradient was calculated according to the hourly temperature. Based on the two, a correction was made to the freeze-thaw fatigue life ratio according to the following formula: ; in, is the differential settlement index of the dirty roadbed, is the maximum cumulative settlement increment of all monitoring points during the spring thaw period, is the minimum value of the cumulative settlement increment of all monitoring points during the spring thaw period, is the average value of the cumulative settlement increments at all monitoring points during the spring thaw period; ; ; in, is the freeze-thaw fatigue life ratio after correction, is the average temperature gradient, 、 They are all monitoring points in the spring thaw period. The highest and lowest temperatures at the moment, The highest and lowest temperatures correspond to the monitoring points in The distance along the track extension direction at any moment, is the index of the time during the spring thaw period, , is the number of moments in the spring thaw period.

[0012] Furthermore, freeze-thaw conditions and freeze-thaw and dynamic load coupled conditions were simulated, and different models were used to obtain each condition based on the freeze-thaw damage accumulation index. The specific steps and the formulas are as follows: 1) Under freeze-thaw conditions, consider the effect of freeze-thaw damage on the elastic modulus of the material: ; in, is the maximum contact force under freeze-thaw conditions, is the contact force under ideal damage-free condition, is the elastic modulus attenuation coefficient, ; 2) In the coupled working condition, finite element method is used to simulate the dynamic response of the train during operation, collect the instantaneous maximum contact force during the dynamic process, consider the impact of freeze-thaw damage on the mechanical properties of the material, and the synergistic effect of dynamic load and freeze-thaw damage; ; in, is the actual maximum contact force of the coupling condition, is the maximum contact force for the dynamic load case, is the coupling effect coefficient, , is the synergistic effect coefficient of dynamic load and freeze-thaw damage, , is the dynamic load amplitude, is the static contact force.

[0013] Furthermore, the bearing capacity attenuation index is calculated. By comparing the attenuation difference between the coupled working condition and the freeze-thaw working condition, the dynamic load acceleration factor is calculated. Combined with the primary freeze-thaw fatigue life ratio, the freeze-thaw fatigue life ratio is corrected twice to obtain the secondary corrected freeze-thaw fatigue life ratio. The formula is as follows: Calculate the load-bearing capacity attenuation index for freeze-thaw conditions: ; in, is the bearing capacity attenuation index under freeze-thaw conditions; Calculate the total attenuation exponent for the coupled case: ; in, is the total attenuation index of the coupled condition; Calculation of dynamic load acceleration factors : ; Get the second corrected freeze-thaw fatigue life ratio: ; in, is the freeze-thaw fatigue life ratio after secondary correction.

[0014] Furthermore, based on the secondary corrected freeze-thaw fatigue life ratio, the disease risk level of the dirty roadbed is divided. The specific steps are as follows: when When the dirty roadbed has not experienced freeze-thaw cycles, the remaining freeze-thaw resistance is at its initial value; when When the soiled roadbed has a strong residual freeze-thaw resistance, it is at a low disease risk level; when When the residual anti-freeze-thaw capacity of the dirty roadbed is medium, it is a medium disease risk level; when When the residual anti-freeze-thaw capacity of the dirty roadbed is weak, the disease risk level is high; when When , the dirty roadbed is in a critical failure state; in, To classify the critical value of low disease risk and medium disease risk level, It is the critical value for dividing the medium disease risk and high disease risk levels.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention arranges monitoring points at equal intervals along the track to collect hourly temperatures during the spring thaw period. At the same time, the settlement increments at each monitoring point on the trackbed surface before and after each train passes are recorded, and the cumulative settlement increments during the spring thaw period are accumulated. The actual number of freeze-thaw cycles is determined based on the hourly temperatures during the spring thaw period. A freeze-thaw fatigue test is conducted to plot a curve showing how mechanical properties vary with the number of freeze-thaw cycles, thereby determining the critical number of freeze-thaw cycles and the freeze-thaw damage accumulation index. The freeze-thaw fatigue life ratio is corrected by combining the uneven settlement index and temperature gradient to achieve quantitative analysis of the time-varying temperature field and spatial deformation. The model can adapt to the complex working conditions of "temperature transients and uneven settlement" during the spring thaw period, making the assessment results consistent with the actual disease development. By simulating freeze-thaw conditions, freeze-thaw and dynamic load coupled conditions, different models are used to obtain the maximum contact force of each condition based on the freeze-thaw damage accumulation index, and the bearing capacity attenuation index is calculated. By comparing the attenuation difference between the coupled condition and the freeze-thaw condition, the dynamic load acceleration factor is calculated. Combined with the primary freeze-thaw fatigue life ratio, the freeze-thaw fatigue life ratio is corrected twice to obtain the secondary corrected freeze-thaw fatigue life ratio. This can accurately evaluate the fatigue life under multi-factor coupling and provide a basis for the classification of disease levels. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the overall method flow of the present invention; Figure 2 It is a fitting diagram of the plasticity index and the number of dirt corrections; Figure 3 It is a fitting diagram of compressive strength and mechanical correction coefficient; Figure 4 It is a fitting diagram of the uneven settlement index and the freeze-thaw fatigue life ratio after one correction; Figure 5 It is a fitting diagram of the average temperature gradient and the freeze-thaw fatigue life ratio after one correction; Figure 6 This is a schematic diagram of the fitting between the freeze-thaw damage accumulation index and the maximum contact force under freeze-thaw conditions; Figure 7 It is a fitting diagram of the maximum contact force of the dynamic load condition and the actual maximum contact force of the coupling condition; Figure 8 Schematic diagram of the fitting between the freeze-thaw damage accumulation index and the actual maximum contact force of the coupling condition; Figure 9 It is a fitting diagram of the dynamic load amplitude and the actual maximum contact force of the coupling condition; Figure 10It is a fitting diagram of the static load contact force and the actual maximum contact force of the coupling working condition. DETAILED DESCRIPTION

[0017] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0018] It should be noted that, unless otherwise defined, the technical or scientific terms used in the present invention should have the usual meanings understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative position relationships. When the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0019] Example 1: See also Figure 1 , the present invention provides a technical solution: A simulation analysis method for dirty roadbed damage under dynamic-thaw action during the spring thaw period, comprising the following steps: S1. Evenly spaced monitoring points are arranged along the track. Hourly temperatures are collected during the spring thaw period. The settlement increments at each monitoring point before and after a train passes are recorded and accumulated as cumulative settlement. Dynamic load parameters for the contaminated trackbed are simultaneously acquired. After the spring thaw period, contamination characteristics and mechanical property parameters are collected. The actual number of freeze-thaw cycles is determined based on the hourly temperatures. Freeze-thaw fatigue tests are conducted to plot the change in mechanical property parameters versus freeze-thaw cycle number, determine the critical number of freeze-thaw cycles, and calculate the freeze-thaw damage accumulation index. On the basis of the above embodiment, the dynamic load parameters include static load contact force, dynamic load amplitude, the dirt characteristic parameter is plasticity index; and the mechanical property parameter is compressive strength.

[0020] On the basis of the above embodiment, monitoring points are arranged at equal intervals along the track, and the settlement increments at each monitoring point before and after the train passes are recorded and accumulated as the cumulative settlement. The specific method is as follows: Laser displacement sensors, model ILD2200-40, were selected and arranged at equal intervals along the track extension direction, for example, one monitoring point was set every 50 meters to ensure uniform spatial distribution. Each monitoring point was located on the roadbed surface below the sleeper, avoiding the rail support points to prevent the train load from directly acting on the sensor. The train entering the monitoring area was detected through track circuits or radar speed meters. Data collection was started 5 minutes in advance and the initial settlement value was recorded. Settlement data was continuously collected until 5 minutes after the train left, and the terminal settlement value was recorded. The single settlement increment of each monitoring point was calculated; based on the single settlement increment and the total number of trains passing each monitoring point during the spring thaw period, the cumulative settlement increment of each monitoring point during the spring thaw period was obtained.

[0021] Based on the above embodiment, the method for collecting static load contact force, dynamic load amplitude, plasticity index and compressive strength is as follows: Method for collecting static load contact force: A rail stress gauge (such as HBM U9C type load cell) is buried under the sleeper corresponding to the monitoring point. After calibration, the zero point data is recorded. When the train is stopped (no power), the sensor output voltage is collected and converted into a static load value using the calibration formula. , ,in, is the voltage, is the sensitivity coefficient, is the zero point offset.

[0022] Method for collecting dynamic load amplitude: Use a piezoelectric force sensor, start collecting data 5 minutes before the train passes, set the trigger threshold, and record the maximum value of the force signal when the train passes. and minimum value , the dynamic load amplitude is .

[0023] Plasticity index collection method: The samples were collected once before and after the spring thaw period. Three samples were collected from the roadbed each time (between sleepers, on the roadbed slope, and on the ballast shoulder). 100g of the sample was passed through a 0.5mm sieve to retain fine particles. The liquid limit test was performed using a Casagrande liquid limit meter. , plastic limit test, using the rubbing method, measured plastic limit , calculate the plasticity index , .

[0024] Compressive strength collection method: The uniaxial compressive peak strength of the dirty roadbed specimen is directly obtained by conducting the strength influence coefficient test simultaneously. Usually, a pressure testing machine is used to apply uniaxial pressure to the dirty roadbed specimen, and the pressure and deformation data are recorded in real time by the equipment. When the specimen is damaged, the maximum pressure value reached is the uniaxial compressive peak strength, which is used as the compressive strength. .

[0025] Based on the above embodiment, the collected hourly temperature, cumulative settlement increment, dynamic load parameters, dirt characteristic parameters and mechanical performance parameters must all be normalized. Through normalization, the data of different indicators are unified to the range of 0 to 1, eliminating the influence of dimension and value range, so that these data are comparable and consistent in subsequent analysis operations.

[0026] Based on the above embodiment, the actual number of freeze-thaw cycles is determined according to the hourly temperature during the spring thaw period. The specific steps and the formula based on them are as follows: Setting the Freeze Threshold ; when It is considered as the freezing stage; when The melting stage is considered as the is the hourly temperature, is the time variable of spring thaw period; Based on hourly temperature and freeze threshold , the effective freeze-thaw cycle process is defined as follows: When the hourly temperature The complete temperature fluctuation cycle from the melting stage to the freezing stage and then back to the melting stage is recorded as one effective freeze-thaw cycle process; The time interval between the temperature continuously falling below the threshold and rising above the freezing threshold is three days. Three days can ensure the time required for water to freeze into ice in the pores. If the time interval is too short (such as one day), the ice will not be completely frozen or will not melt sufficiently, and the damage effect will not be significant. If the time interval is too long (such as seven days), it is an extreme working condition, and three days can be used as a standard assessment benchmark. Traverse all time points during the spring thaw period to obtain the actual number of freeze-thaw cycles; According to the mechanical properties parameters, the critical number of freeze-thaw cycles is determined through freeze-thaw fatigue tests, and the freeze-thaw damage accumulation index is calculated. The specific steps and the formula are as follows: Freezing process: Place the dirty roadbed sample in a -20℃ environment for 4 hours; Melting process: Heat to 20℃ and keep for 4 hours; Repeat the freezing and thawing process and record the number of cycles; After every 10 freeze-thaw cycles, the compressive strength test is carried out on the dirty roadbed sample. If there are multiple dirty roadbed samples, the previous dirty roadbed sample will not be used after the compressive strength test, and another sample will be used for the next compressive strength test; When the compressive strength loss rate exceeds the preset threshold, it is determined to have reached a critical state: Draw a curve of freeze-thaw cycle number-compressive strength loss rate, and the horizontal axis corresponding to the intersection of the curve and the threshold horizontal line is the critical freeze-thaw cycle number; The freeze-thaw damage accumulation index is calculated based on the following formula: ; in, The freeze-thaw damage accumulation index is used to evaluate the damage accumulation degree of the dirty roadbed under the actual freeze-thaw cycle by combining the two indicator parameters of the actual freeze-thaw cycle number and the critical freeze-thaw cycle number. The larger the freeze-thaw damage accumulation index, the higher the damage accumulation degree. Where, is the actual number of freeze-thaw cycles, is the critical number of freeze-thaw cycles.

[0027] On this basis, it should be noted that: exist hour: The closer the actual freeze-thaw cycle number is to the critical freeze-thaw cycle number, the more serious the damage to the dirty roadbed is. Therefore, the actual freeze-thaw cycle number and the freeze-thaw damage accumulation index are positively correlated.

[0028] Actual number of freeze-thaw cycles It refers to the number of complete cycles of freezing and thawing that a dirty roadbed undergoes during the spring thaw period due to repeated rises and falls in temperature.

[0029] Actual freeze-thaw cycles Critical freeze-thaw cycles ,calculate ,when near hour, When it approaches 1, it means that the freeze-thaw damage of the dirty roadbed is serious and close to the critical state of failure.

[0030] when hour, , indicating that the dirty roadbed has reached a critical state of failure.

[0031] Therefore, the above form is used to express the freeze-thaw damage accumulation index and the actual number of freeze-thaw cycles , critical freeze-thaw cycles The functional relationship between them.

[0032] S2. Correcting the critical freeze-thaw cycle number based on soiling characteristics and mechanical property parameters, and calculating the freeze-thaw fatigue life ratio based on the actual freeze-thaw cycle number and the corrected critical freeze-thaw cycle number; Table 1. Changes in the number of dirt corrections with plasticity index

[0033] It can be seen from Table 1 that when the critical number of freeze-thaw cycles remains unchanged at 100, the number of dirt corrections shows a decreasing pattern as the plasticity index increases.

[0034] Specifically, for every 0.5 increase in the plasticity index, the number of dirt corrections steadily decreases by 1; from a plasticity index of 5 (90 dirt corrections) to a plasticity index of 17 (66 dirt corrections), the plasticity index increases by 12 and the number of dirt corrections decreases by 24, and the two are roughly negatively correlated.

[0035] according to Figure 2 It can be seen that when the critical number of freeze-thaw cycles is fixed at 100, the number of dirt corrections and the plasticity index show a significant negative correlation.

[0036] Table 2. Changes in the revised value of the critical freeze-thaw cycle number with the plasticity index

[0037] Table 2 shows that when the critical number of freeze-thaw cycles is fixed at 100, the strength influence coefficient is fixed at 0.8, and the baseline compressive strength is fixed at 20, the number of mechanical corrections increases with increasing compressive strength (from 21 to 41, increasing by 1 each time). For every unit increase in compressive strength, the number of mechanical corrections increases steadily by 0.8, showing a significant positive correlation.

[0038] Depend on Figure 3 It can be seen that when the critical number of freeze-thaw cycles, strength influence coefficient and benchmark compressive strength remain unchanged, the number of mechanical corrections and compressive strength show a significant positive correlation.

[0039] On the basis of the above embodiment, the critical number of freeze-thaw cycles is corrected based on the dirt characteristics and mechanical property parameters collected after the spring thaw period, according to the following formula: ; ; ; in, The critical freeze-thaw cycle number is the correction value of the critical freeze-thaw cycle number under laboratory standard conditions by quantifying the influence of dirt characteristics and mechanical performance parameters on freeze-thaw resistance. Converted into a corrected value for the critical freeze-thaw cycle number ; Where, Correction times for dirt, is the number of mechanical corrections, is the critical number of freeze-thaw cycles, 、 They are the plasticity index and compressive strength collected after the spring thaw period, is the baseline compressive strength, is the strength influence coefficient, ; Number of dirt corrections It is used to combine the two index parameters of critical freeze-thaw cycles and plasticity index to evaluate the freeze-thaw sensitivity of materials caused by fine particle composition and dirt adsorption. The larger the dirt correction coefficient, the higher the freeze-thaw sensitivity. Number of mechanical corrections It is used to evaluate the ability of the soiled roadbed to resist frost heave stress by combining the three index parameters of critical freeze-thaw cycles, compressive strength, and benchmark compressive strength. The greater the number of mechanical corrections, the higher the freeze-thaw resistance performance. On this basis, it should be noted that: The plasticity index reflects the clay content and hydraulic properties of fine-grained soil. The higher the clay content in the dirty roadbed, the higher the plasticity index. The larger the plasticity index, the stronger its ability to absorb water and dirt. During water migration and frost heave, the adsorbed water on the surface of the clay freezes and expands at low temperatures, which will produce greater frost heave stress on the internal structure of the dirty roadbed. If there is dirt in the dirty roadbed, it will further aggravate the retention and uneven distribution of water, making frost heave damage more likely to occur. After the dirt combines with the clay, it may weaken the internal bonding strength of the dirty roadbed, making the dirty roadbed more prone to cracks, peeling and other damage during the freeze-thaw cycle, thereby reducing its ability to resist freeze-thaw. Therefore, the plasticity index The larger the value, the higher the risk of freeze-thaw damage to the material due to dirt and moisture. will decrease, showing a negative correlation.

[0040] Compressive strength It is the core indicator of the mechanical properties of the dirty roadbed and directly reflects the ability to resist compression damage. Higher than the benchmark compressive strength When the number of mechanical corrections is Will follow The critical freeze-thaw cycle number is revised and increased; the compressive strength Lower than the benchmark compressive strength When the strength of the dirty roadbed is insufficient, freeze-thaw damage tends to develop rapidly, and the critical number of times is reduced.

[0041] Therefore, the compressive strength The larger the value, the more sufficient the compressive strength reserve of the material is, and the stronger the ability to resist frost heave stress is. will increase, showing a positive correlation.

[0042] Therefore, the above form is used to express the number of dirt corrections and plasticity index , critical freeze-thaw cycles The functional relationship between them expresses the number of mechanical corrections and compressive strength , benchmark compressive strength , critical freeze-thaw cycles The functional relationship between them.

[0043] On this basis, it should be noted that: Dirt correction: through plasticity index Evaluate the freeze-thaw sensitivity of soiled roadbeds due to fine particle composition and soil adsorption, The larger it is, the weaker the material's ability to resist freezing and thawing is, and the critical number needs to be revised downward.

[0044] Mechanical correction: through compressive strength Evaluate the mechanical performance reserve of dirty roadbed, The higher it is, the stronger the freeze-thaw resistance is, and the critical number needs to be revised upward.

[0045] After combining the two, the critical freeze-thaw cycles under laboratory standard conditions are Corrected to the critical freeze-thaw times taking into account actual dirt and mechanical properties .

[0046] On this basis, it should be noted that: Designed for freeze-thaw resistance, benchmark compressive strength It can be set as the initial compressive strength of the soiled roadbed when it is not subjected to freeze-thaw cycles.

[0047] Therefore, the above function form is used to express the freeze-thaw damage accumulation index and the actual freeze-thaw cycle number , critical freeze-thaw cycles The functional relationship between them.

[0048] Therefore, the above form is used to express the corrected value of the critical freeze-thaw cycle number and number of contamination corrections , mechanical correction times The functional relationship between them.

[0049] On the basis of the above embodiment, according to the correction value of the actual freeze-thaw cycle number and the critical freeze-thaw cycle number, the freeze-thaw fatigue life ratio is calculated according to the following formula: ; in, is the freeze-thaw fatigue life ratio of the dirty roadbed; The freeze-thaw fatigue life ratio represents the ratio of the actual freeze-thaw damage degree to the critical damage threshold; when When the actual freezing and thawing times do not reach the critical value, the dirty roadbed is in a safe state; when When the actual freeze-thaw times exceed the critical value, the dirty roadbed material has suffered fatigue damage; The freeze-thaw fatigue life ratio is used to evaluate the remaining life of the dirty roadbed by combining two indicator parameters: the actual number of freeze-thaw cycles and the correction value of the critical number of freeze-thaw cycles. The smaller the freeze-thaw fatigue life ratio, the longer the remaining life of the dirty roadbed. On this basis, it should be noted that: Actual number of freeze-thaw cycles It directly reflects the number of freeze-thaw cycle loads the material has endured. During each freeze-thaw cycle, microcracks will form inside the material due to the expansion of water freezing and the contraction of water melting, resulting in damage accumulation. The more cycles there are, the more severe the accumulated damage to the material becomes, and the closer it approaches or exceeds the critical damage threshold, the closer the freeze-thaw fatigue life ratio approaches 1, and the remaining life of the material becomes shorter and shorter. Corrected value of critical freeze-thaw cycles It is the critical damage threshold after considering the dirt characteristics and mechanical properties, reflecting the ability of the material to resist freeze-thaw damage. The larger the value, the more freeze-thaw cycles the material can withstand and the stronger the freeze-thaw resistance. Under these conditions, the degree of damage is lower and it is less likely to reach the destruction threshold. The closer the freeze-thaw fatigue life ratio is to 0, the longer the remaining life of the material.

[0050] Therefore, the above form is used to express the freeze-thaw fatigue life ratio and actual number of freeze-thaw cycles , Corrected value of critical freeze-thaw cycles The functional relationship between them.

[0051] S3. Extract the maximum, minimum, and average values ​​of the cumulative settlement increments at each monitoring point, calculate the uneven settlement index, calculate the temperature gradient based on the hourly temperature, and use this to make a correction to the freeze-thaw fatigue life ratio. Based on the above embodiment, the differential settlement index of the dirty roadbed is calculated according to the following formula: ; in, is the uneven settlement index of the dirty roadbed. The uneven settlement index is used to combine the maximum, minimum and average values ​​of the cumulative settlement increment to evaluate the settlement uniformity of the dirty roadbed under the action of freeze-thaw cycles. The larger the uneven settlement index, the more significant the settlement difference, the more uneven the internal stress distribution of the material, and the higher the risk of freeze-thaw fatigue damage.

[0052] Where, is the maximum cumulative settlement increment of all monitoring points during the spring thaw period, is the minimum value of the cumulative settlement increment of all monitoring points during the spring thaw period, is the average value of the cumulative settlement increments at all monitoring points during the spring thaw period; On this basis, it should be noted that: ( ) reflects the degree of discreteness of the settlement increment. The larger the difference, the more significant the difference in settlement at different locations, which makes the uneven settlement index Therefore, the differential settlement index and( ) is positively correlated.

[0053] ( ) as the reference value for normalization, so that the uneven settlement index It has dimensionless characteristics, which facilitates comparison under different working conditions.

[0054] Therefore, the above form is used to express the uneven settlement index and( )、( ) is the functional relationship between them.

[0055] Table 3. Changes of freeze-thaw fatigue life ratio after correction with uneven settlement index and average temperature gradient

[0056] It can be seen from Table 3 that when the freeze-thaw fatigue life ratio of the dirty roadbed is fixed at 5, with the increase of the uneven settlement index and the average temperature gradient, the freeze-thaw fatigue life ratio after one correction shows a continuously increasing trend.

[0057] Specifically, the uneven settlement index and the average temperature gradient work together to push the once-corrected freeze-thaw fatigue life ratio to gradually increase (for example, from 5.1 at sequence number 1, to 9.47 at sequence number 25 as both increase).

[0058] Depend on Figure 4 、 Figure 5It can be seen that when the freeze-thaw fatigue life ratio of the dirty roadbed is fixed at 5, the once-corrected freeze-thaw fatigue life ratio shows a significant positive correlation with the uneven settlement index and the average temperature gradient: Influence of uneven settlement index: As the uneven settlement index increases, the freeze-thaw fatigue life ratio after one correction continues to increase, the fitting line fits the data points well, and the correlation is significant; Influence of average temperature gradient: When the average temperature gradient increases, the once-corrected freeze-thaw fatigue life ratio also increases steadily. The fitting line accurately depicts the changing trend, and the positive correlation is clear.

[0059] On the basis of the above embodiment, the freeze-thaw fatigue life ratio is corrected based on the uneven settlement index and the temperature gradient, according to the following formula: ; ; in, The average temperature gradient refers to the temperature variation within a unit distance along the track extension direction, which is used to quantify the difference in temperature distribution in space. in, is the freeze-thaw fatigue life ratio after correction, 、 They are all monitoring points in the spring thaw period. The highest and lowest temperatures at a given time point, The highest and lowest temperatures correspond to the monitoring points in The distance between time points along the track extension direction, is the index of the time point during the spring thaw period, , is the number of time points within the spring thaw period.

[0060] On this basis, it should be noted that: The essence of the average temperature gradient is the average temperature change per unit distance, and ( ) directly reflects the average amplitude of temperature change. When the distance between two monitoring points ( ) is fixed, ( ) is larger, indicating that the temperature difference between the two monitoring points is more significant and the temperature gradient within a unit distance is larger; when ( ) is fixed, the distance between the two monitoring points ( ) is larger, indicating that the spatial distance of temperature change is longer, the temperature change is smoother, and the average temperature gradient within unit distance is smaller.

[0061] In summary, the average temperature gradient and( ) is positively correlated, and the average temperature gradient and( ) is negatively correlated, so the above form is used to express the average temperature gradient and( )、( ) between them.

[0062] On this basis, it should be noted that: Where, is the freeze-thaw fatigue life ratio after correction.

[0063] The once-corrected freeze-thaw fatigue life ratio is used to combine the two index parameters of uneven settlement index and temperature gradient to make a correction to the freeze-thaw fatigue life ratio of dirty roadbed. The smaller the once-corrected freeze-thaw fatigue life ratio is, the longer the remaining life is. When the differential settlement index When the load increases, it means that the settlement difference of each part of the roadbed increases, and the stress distribution inside the structure becomes more uneven. Under the action of freeze-thaw cycles, this uneven stress will accelerate the fatigue damage of the roadbed material, resulting in a shortened freeze-thaw fatigue life, which in turn makes the freeze-thaw fatigue life after a correction greater than that after a correction. Increase; when the average temperature gradient When the temperature increases, the temperature difference between different positions of the roadbed becomes larger, and the difference in the degree of thermal expansion and contraction of the material becomes more severe. The resulting thermal stress acts repeatedly on the roadbed, accelerating the degradation of material properties and also reducing the freeze-thaw fatigue life of the roadbed. Therefore, the freeze-thaw fatigue life after one correction is shorter than Increase; Therefore, the freeze-thaw fatigue life after a correction is and differential settlement index , average temperature gradient Both are positively correlated.

[0064] Therefore, the above form is used to express the once-corrected freeze-thaw fatigue life ratio and differential settlement index , average temperature gradient The functional relationship between them.

[0065] S4. Simulate freeze-thaw conditions and freeze-thaw and dynamic load coupled conditions. Use different models to obtain the maximum contact force for each condition based on the freeze-thaw damage accumulation index. Calculate the bearing capacity attenuation index. Compare the attenuation difference between the coupled condition and the freeze-thaw condition to calculate the dynamic load acceleration factor. Combined with the primary freeze-thaw fatigue life ratio, perform a secondary correction on the freeze-thaw fatigue life ratio to obtain the secondary corrected freeze-thaw fatigue life ratio. Table 4. Changes of maximum contact force under freeze-thaw conditions with freeze-thaw damage accumulation index

[0066] As shown in Table 4, when the contact force (fixed at 100) and the elastic modulus attenuation coefficient (fixed at 1) in the ideal damage-free state remain unchanged, the maximum contact force under the freeze-thaw condition shows a continuous decreasing trend with the increase of the freeze-thaw damage accumulation index. The decreasing amplitude becomes more significant with the increase of the freeze-thaw damage accumulation index, reflecting that the weakening effect of freeze-thaw damage accumulation on the contact force increases with the deepening of damage, and there is a clear negative correlation between the two.

[0067] Depend on Figure 6 It can be seen that with the increase of the freeze-thaw damage accumulation index, the maximum contact force under freeze-thaw conditions shows a linear decreasing trend, and the fitting line fits the data points well, indicating that there is a significant linear negative correlation between the two.

[0068] Based on the above embodiment, freeze-thaw conditions and freeze-thaw and dynamic load coupled conditions were simulated, and different models were used to obtain the maximum contact force of each condition according to the freeze-thaw damage accumulation index. The specific steps and the formulas are as follows: 1) Under freeze-thaw conditions, consider the effect of freeze-thaw damage on the elastic modulus of the material: ; in, is the maximum contact force under freeze-thaw conditions. The maximum contact force under freeze-thaw conditions is used to quantify the effect of freeze-thaw damage on the maximum contact force by combining the three index parameters of contact force under ideal damage-free state, freeze-thaw damage accumulation index, and elastic modulus attenuation coefficient. The larger it is, the smaller the effect of freeze-thaw damage on the maximum contact force.

[0069] Where, is the contact force under ideal damage-free condition, is the elastic modulus attenuation coefficient, ; will be different The values ​​are substituted into the freeze-thaw-load coupled finite element model to calculate the structural response and compare it with the field monitoring data or laboratory results to adjust The value range of when When , the structural deformation calculated by the model is consistent with the measured value, which can be used as the lower limit of sensitive materials; when When , the model can reflect the modulus fluctuations of a few materials in a specific freeze-thaw stage and can be used as an upper limit.

[0070] On this basis, it should be noted that: Freeze-thaw damage accumulation index Reflects the cumulative degree of freeze-thaw damage. The larger the value, the more severe the freeze-thaw damage the material has experienced. The more severe the material damage, the more obvious the performance degradation, and the smaller the maximum contact force it can withstand under the same working conditions. Therefore, the maximum contact force under freeze-thaw working conditions is and freeze-thaw damage accumulation index is negatively correlated. Elastic modulus attenuation coefficient Characterize the sensitivity of elastic modulus to freeze-thaw damage, elastic modulus attenuation coefficient The larger the value is, the faster the elastic modulus decays under the same freeze-thaw damage accumulation index, the more obvious the decrease in material contact stiffness, and the greater the decrease in the maximum contact force. and elastic modulus attenuation coefficient Is negatively correlated.

[0071] The linear term captures the direct effect of area loss: Freeze-thaw damage accumulation index Directly reflects the expansion of micro cracks inside the material and the reduction of effective bearing area, The larger it is, the smaller the effective bearing area is and the contact force decreases linearly.

[0072] The square root term reflects the nonlinear effect of stiffness softening. Together, the two lead to an accelerated decrease in contact force as damage intensifies, which is consistent with the basic laws of material mechanical behavior and contact theory: ( ) in the elastic modulus attenuation coefficient Characterizes the sensitivity of the material to softening, when ( ) increases, the elastic modulus decreases, resulting in a nonlinear decrease in contact stiffness. The contact force is related to the square root of the stiffness (based on contact mechanics theory, such as the nonlinear relationship between force and elastic modulus in Hertzian contact). When the stiffness decreases, the contact force decays slowly at first and then quickly (for example, when the stiffness is halved, the force is not halved, but drops to ).

[0073] Therefore, the above form is used to express the maximum contact force of the freeze-thaw condition Functional relationship between contact force, freeze-thaw damage accumulation index, and elastic modulus attenuation coefficient under ideal damage-free state.

[0074] Table 5. Variation of the actual maximum contact force of the coupling condition with the freeze-thaw damage accumulation index

[0075] Table 5 shows that, under the synergistic effect of factors such as dynamic load amplitude and static load contact force, as the freeze-thaw damage accumulation index decreases (gradually from 0.2 to 0.01), the actual maximum contact force of the coupled condition increases (gradually from 99.5 to 280), showing a significant negative correlation between the freeze-thaw damage accumulation index and the actual maximum contact force of the coupled condition.

[0076] Depend on Figure 7-10 It can be seen that the actual maximum contact force of the coupling condition has different correlation rules with the maximum contact force of the dynamic load condition, the freeze-thaw damage accumulation index, the dynamic load amplitude, and the static load contact force: As the maximum contact force and dynamic load amplitude of the dynamic load condition increase, the actual maximum contact force of the coupled condition increases, showing a positive correlation; As the freeze-thaw damage accumulation index and static load contact force increase, the actual maximum contact force of the coupling condition decreases, showing a negative correlation.

[0077] 2) In the coupled working condition, finite element method is used to simulate the dynamic response of the train during operation, collect the instantaneous maximum contact force during the dynamic process, consider the impact of freeze-thaw damage on the mechanical properties of the material, and the synergistic effect of dynamic load and freeze-thaw damage; ; in, The actual maximum contact force of the coupling condition is used to combine the four index parameters of the maximum contact force of the dynamic load condition, the freeze-thaw damage accumulation index, the dynamic load amplitude, and the static load contact force to evaluate the failure probability of the material under the dynamic load and freeze-thaw coupling condition. The greater the actual maximum contact force of the coupling condition, the higher the failure probability. Where, is the coupling effect coefficient, , is the synergistic effect coefficient of dynamic load and freeze-thaw damage, , is the dynamic load amplitude, is the static load contact force; This means that the weakening effect of freeze-thaw damage on contact force is in the moderate to significant range. It represents the degree of freeze-thaw damage. The larger it is, the more severe the material damage is.

[0078] like , which will lead to an underestimation of the weakening effect of freeze-thaw damage on contact force, which contradicts the experimental phenomenon that "freeze-thaw significantly reduces material strength"; like , the contact force may be excessively attenuated, and the superposition result of the synergistic effect with the dynamic load may exceed the actual failure range of the material.

[0079] The contact force attenuation rate was established by measuring the change of contact force with the freeze-thaw damage accumulation index through conducting material mechanical property tests under different freeze-thaw cycles and applying dynamic load to each group of freeze-thawed specimens. linear relationship.

[0080] Statistics of multiple sets of experimental data were obtained by least squares fitting The mean and fluctuation range of are used to ensure that the fitting error is within an acceptable range.

[0081] The specific value range of The contact force response under the value of ΔH is compared with the stress distribution when dynamic load is coupled with freeze-thaw damage: fixed and ,Change , calculate the contact force increment ratio; when When , the contact force increment does not match the physical observation; when When , the contact force increment exceeds the measured data of material failure.

[0082] Therefore, setting .

[0083] On this basis, it should be noted that: Maximum contact force for dynamic load case It is the basic load of dynamic action during train operation, reflecting the instantaneous load peak caused by factors such as vibration and speed change during train operation. In coupled working conditions, the synergistic effect of freeze-thaw damage and dynamic load will further amplify the contact force on this basis. Therefore Therefore, the actual maximum contact force of the coupling case is and maximum contact force for dynamic load cases Is positively correlated.

[0084] along with Increase, the material undergoes multiple expansion and contraction during the freeze-thaw cycle, resulting in internal microcracks, pore expansion, crystal structure destruction, and significant reduction in mechanical properties such as elastic modulus and strength of the material, as well as a decrease in bearing capacity. The maximum contact force that can be sustained Therefore, the actual maximum contact force of the coupling case is and freeze-thaw damage accumulation index Is negatively correlated.

[0085] Dynamic load amplitude Refers to the fluctuation amplitude of dynamic load relative to static load, that is, the additional load caused by train vibration. When the load increases, the impact effect of dynamic load on the dirty roadbed increases, while freeze-thaw damage will weaken the ability to resist dynamic impact. The synergistic effect of the two will further amplify the contact force. The synergistic effect coefficient in the formula is and The ratio of reflects this effect. represents the correction of the contact force by the ratio of the dynamic load amplitude to the static load. Therefore, the actual maximum contact force of the coupling case is and dynamic load amplitude is positively correlated, the actual maximum contact force of the coupling condition and static contact force Is negatively correlated.

[0086] Therefore, the above form is used to express the functional relationship between the actual maximum contact force of the coupling condition and the maximum contact force of the dynamic load condition, the freeze-thaw damage accumulation index, the dynamic load amplitude, and the static load contact force.

[0087] The calculation formula for the maximum contact force of the dynamic load case is as follows: ; in, is the maximum contact force of the dynamic load condition. The maximum contact force of the dynamic load condition is used to combine the two index parameters of static load contact force and dynamic load amplitude to evaluate the additional impact of dynamic load on the bearing capacity and fatigue life of the structure, and The larger it is, the greater the additional impact of dynamic load on the structural bearing capacity and fatigue life; is the power amplification coefficient. In ordinary railways, ; On high-speed railways, ; Theoretical calculations show that on ordinary railways, when the wheels pass through ideal tracks at the lowest speed, the dynamic contact force is approximately 1.1-1.2 times the static load; the upper limit of 2.5 is used to cope with the strong dynamic amplification effect under heavy loads and poor track conditions.

[0088] High-speed railway design specifications require consideration of minimum dynamic amplification effects when using quasi-static models. For example, when a train travels over an ideal ballastless track at the design speed, the dynamic contact force calculated based on Hertz contact theory and multi-body dynamics models is at least 1.3 times the static load. Domestic high-speed railways demonstrate that the dynamic amplification factor under normal maintenance conditions generally ranges from 1.3 to 1.6, with an upper limit of 1.8 covering extreme operating conditions.

[0089] On this basis, it should be noted that: When the dynamic load frequency is far away from the natural frequency of the material, the system can be approximated as a linear response. At this time, the contact force increment caused by the dynamic load is linearly related to the load amplitude (i.e. ), superimposed on the static contact force The maximum contact force is formed.

[0090] when When , dynamic load does not cause contact force amplification (only static load acts); when When the contact force exceeds the static load value due to factors such as inertia force and vibration coupling, The larger it is, the more significant the dynamic effect is.

[0091] Therefore, the maximum contact force for the dynamic load case is Based on the static-dynamic superposition of linear systems, Quantifying the dynamic amplification effect.

[0092] Therefore, the above form is used to express the functional relationship between the maximum contact force of the dynamic load condition and the static load contact force, the dynamic amplification coefficient, and the dynamic load amplitude.

[0093] On the basis of the above embodiment, the bearing capacity attenuation index of different working conditions is calculated according to the maximum contact force under each working condition, and the dynamic load acceleration factor is obtained based on this. The freeze-thaw fatigue life ratio after the primary correction is combined with the dynamic load acceleration factor, and the freeze-thaw fatigue life ratio is corrected twice to obtain the secondary corrected freeze-thaw fatigue life ratio. The formula is as follows: Calculate the load-bearing capacity attenuation index for freeze-thaw conditions: ; in, is the bearing capacity attenuation index under freeze-thaw conditions; Calculate the total attenuation exponent for the coupled case: ; in, is the total attenuation index of the coupled condition; On this basis, it should be noted that: The above function quantifies the load-carrying capacity degradation in terms of relative attenuation, ( ) is the absolute attenuation of contact force caused by damage, ( ) is the relative attenuation ratio, which can reflect the degradation degree of bearing capacity in a dimensionless way.

[0094] Calculate the dynamic load acceleration factor: ; in, The dynamic load acceleration factor is used to combine the two index parameters, the total attenuation index of the coupled working condition and the bearing capacity attenuation index of the freeze-thaw working condition, to quantify the accelerating effect of the dynamic load on the freeze-thaw damage. The larger the dynamic load acceleration factor, the more significant the accelerating effect of the dynamic load on the freeze-thaw damage.

[0095] Get the second corrected freeze-thaw fatigue life ratio: ; in, is the freeze-thaw fatigue life ratio after secondary correction. The secondary correction freeze-thaw fatigue life ratio is used to combine the two index parameters of the freeze-thaw fatigue life ratio after primary correction and the dynamic load acceleration factor to quantify the synergistic effect of the two on the life. The larger the secondary correction freeze-thaw fatigue life ratio, the shorter the remaining life. On this basis, it should be noted that: It reflects the “basic weakening” of the fatigue life of the dirty roadbed caused by freeze-thaw, which is a manifestation of static damage; Dynamic loads cannot independently induce freeze-thaw damage, but they can accelerate crack propagation through vibration stress on the basis of the degradation of the dirty roadbed caused by freeze-thaw. is the quantitative factor of this acceleration effect.

[0096] In the Miner criterion, when two loads act synergistically, if the damage rate of the latter load depends on the material state caused by the former load, the damage accumulation often shows a product relationship. Therefore, freeze-thaw first reduces the performance of the dirty roadbed foundation, and dynamic loads further accelerate fatigue damage on the basis of freeze-thaw damage. Therefore, the life under coupled action is longer than that required. Multiply .

[0097] Therefore, the above form is used to express the functional relationship between the freeze-thaw fatigue life ratio after secondary correction, the freeze-thaw fatigue life ratio after primary correction, and the dynamic load acceleration factor.

[0098] S5. Classify the risk level of contaminated roadbed damage based on the secondary corrected freeze-thaw fatigue life ratio.

[0099] Based on the above embodiment, the risk level of the contaminated roadbed is divided according to the secondary corrected freeze-thaw fatigue life ratio. The specific steps are as follows: when When the dirty roadbed has not experienced freeze-thaw cycles, the remaining freeze-thaw resistance is at its initial value; when When the soiled roadbed has a strong residual freeze-thaw resistance, it is at a low disease risk level; when When the residual anti-freeze-thaw capacity of the dirty roadbed is medium, it is a medium disease risk level; when When the residual anti-freeze-thaw capacity of the dirty roadbed is weak, the disease risk level is high; when When , the dirty roadbed is in a critical failure state; in, To classify the critical value of low disease risk and medium disease risk level, It is the critical value for dividing the medium disease risk and high disease risk levels.

[0100] Based on the mechanical model of dirty roadbed and freeze-thaw fatigue damage theory, combined with the principle of dynamic load, the theoretical values ​​of roadbed structure reaching different disease degrees under different freeze-thaw fatigue life ratios are derived. For example, by establishing the fatigue damage constitutive equation of roadbed under the coupling of freeze-thaw and dynamic load, the corresponding secondary corrected freeze-thaw fatigue life ratios are calculated when the roadbed begins to show obvious structural damage and affects driving safety, so as to determine the and Theoretical value.

[0101] The above formulas are all dimensionless and numerical calculations. The formulas are obtained by collecting a large amount of data and performing software simulation to obtain the most recent real situation. The preset parameters in the formulas are set by technicians in this field according to actual conditions.

[0102] The above embodiments can be implemented in whole or in part by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented in whole or in part in the form of a computer program product. Those skilled in the art will appreciate that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by computer software, electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed by hardware or software depends on the specific application and design constraints of the technical solution.

[0103] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, and may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment as needed.

[0104] The above is only a specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed in this application, which should be covered by the scope of protection of the present application.

Claims

1. A simulation analysis method for dirty roadbed damage under the action of dynamic thawing during the spring thaw period, characterized in that: The specific steps include: S1. Evenly spaced monitoring points are arranged along the track. Hourly temperatures are collected during the spring thaw period. The settlement increments at each monitoring point before and after a train passes are recorded and accumulated as cumulative settlement. Dynamic load parameters for the contaminated trackbed are simultaneously acquired. After the spring thaw period, contamination characteristics and mechanical property parameters are collected. The actual number of freeze-thaw cycles is determined based on the hourly temperatures. Freeze-thaw fatigue tests are conducted to plot the change in mechanical property parameters versus freeze-thaw cycle number, determine the critical number of freeze-thaw cycles, and calculate the freeze-thaw damage accumulation index. S2. Correcting the critical freeze-thaw cycle number based on soiling characteristics and mechanical property parameters, and calculating the freeze-thaw fatigue life ratio based on the actual freeze-thaw cycle number and the corrected critical freeze-thaw cycle number; S3. Extract the maximum, minimum, and average values ​​of the cumulative settlement increments at each monitoring point, calculate the uneven settlement index, calculate the temperature gradient based on the hourly temperature, and use this to make a correction to the freeze-thaw fatigue life ratio. S4. Simulate freeze-thaw conditions and freeze-thaw and dynamic load coupled conditions. Use different models to obtain the maximum contact force for each condition based on the freeze-thaw damage accumulation index. Calculate the bearing capacity attenuation index. Compare the attenuation difference between the coupled condition and the freeze-thaw condition to calculate the dynamic load acceleration factor. Combined with the primary freeze-thaw fatigue life ratio, perform a secondary correction on the freeze-thaw fatigue life ratio to obtain the secondary corrected freeze-thaw fatigue life ratio. S5. Classify the risk level of contaminated roadbed damage based on the secondary corrected freeze-thaw fatigue life ratio.

2. The simulation analysis method for dirty roadbed damage under the action of spring thaw dynamics and thawing according to claim 1 is characterized by: The dynamic load parameters include static load contact force and dynamic load amplitude, the dirt characteristic parameter is the plasticity index, and the mechanical property parameter is the compressive strength.

3. The simulation analysis method for dirty roadbed damage under the action of spring thaw dynamics and thawing according to claim 2 is characterized by: The actual number of freeze-thaw cycles is determined based on the hourly temperature. The specific steps and the formula are as follows: Setting the Freeze Threshold ; when It is considered as the freezing stage; when The melting stage is considered as the melting stage, in which is the hourly temperature, is the time variable of spring thaw period; Based on hourly temperature and freeze threshold , the effective freeze-thaw cycle process is defined as follows: When the hourly temperature The complete temperature fluctuation cycle from the melting stage to the freezing stage and then back to the melting stage is recorded as one effective freeze-thaw cycle process; Traverse all time points during the spring thaw period to obtain the actual number of freeze-thaw cycles; According to the mechanical properties parameters, the critical number of freeze-thaw cycles is determined through freeze-thaw fatigue tests, and the freeze-thaw damage accumulation index is calculated. The specific steps and the formula are as follows: Freezing process: Place the soiled roadbed material sample in a -20°C environment for 4 hours; Melting process: Heat to 20℃ and keep for 4 hours; Repeat the freezing and thawing process and record the number of cycles; After every 10 freeze-thaw cycles, the compressive strength test of the soiled roadbed material samples was conducted; When the compressive strength loss rate exceeds the preset threshold, it is determined to have reached a critical state: Draw a curve of freeze-thaw cycle number-compressive strength loss rate, and the horizontal axis corresponding to the intersection of the curve and the threshold horizontal line is the critical freeze-thaw cycle number; The freeze-thaw damage accumulation index is calculated based on the following formula: ； in, is the freeze-thaw damage accumulation index, is the actual number of freeze-thaw cycles, is the critical number of freeze-thaw cycles.

4. The simulation analysis method for dirty roadbed damage under the action of spring thaw dynamics and thawing according to claim 3 is characterized by: The critical number of freeze-thaw cycles was modified based on the soil characteristics and mechanical properties parameters collected after the spring thaw period, according to the following formula: ； ； ； in, is the corrected value of the critical freeze-thaw cycle number, Correction times for dirt, is the number of mechanical corrections, is the critical number of freeze-thaw cycles, 、 、 They are the plasticity index, strength influence coefficient and compressive strength collected after the spring thaw period. is the benchmark compressive strength; The freeze-thaw fatigue life ratio is calculated based on the actual number of freeze-thaw cycles and the correction value of the critical number of freeze-thaw cycles according to the following formula: ； in, is the freeze-thaw fatigue life ratio of the dirty roadbed.

5. The simulation analysis method for dirty roadbed damage under the action of spring thaw dynamics and thawing according to claim 4 is characterized by: The maximum, minimum and average values ​​of the accumulated settlement increments at each monitoring point are extracted to calculate the uneven settlement index. The temperature gradient is calculated based on the hourly temperature. Based on the above two factors, a correction is made to the freeze-thaw fatigue life ratio. The formula is as follows: ； in, is the differential settlement index of the dirty roadbed, is the maximum cumulative settlement increment of all monitoring points during the spring thaw period, is the minimum value of the cumulative settlement increment of all monitoring points during the spring thaw period, is the average value of the cumulative settlement increments at all monitoring points during the spring thaw period; ； in, is the freeze-thaw fatigue life ratio after correction, is the average temperature gradient, 、 They are all monitoring points in the spring thaw period. The highest and lowest temperatures at a given time point, The highest and lowest temperatures correspond to the monitoring points in The distance between time points along the track extension direction, is the index of the time point during the spring thaw period, , is the number of time points within the spring thaw period.

6. The simulation analysis method for dirty roadbed damage under the action of spring thaw dynamics and thawing according to claim 5 is characterized by: Simulate freeze-thaw conditions and freeze-thaw and dynamic load coupled conditions. Use different models to obtain the maximum contact force for each condition based on the freeze-thaw damage accumulation index. The specific steps and the underlying formula are as follows: 1) Under freeze-thaw conditions, consider the effect of freeze-thaw damage on the elastic modulus of the material: ； in, is the maximum contact force under freeze-thaw conditions, is the contact force under ideal damage-free condition, is the elastic modulus attenuation coefficient, ; 2) In the coupled working condition, finite element method is used to simulate the dynamic response of the train during operation, collect the instantaneous maximum contact force during the dynamic process, consider the impact of freeze-thaw damage on the mechanical properties of the material, and the synergistic effect of dynamic load and freeze-thaw damage; ； in, is the actual maximum contact force of the coupling condition, is the maximum contact force for the dynamic load case, is the dynamic load amplitude, is the coupling effect coefficient, , is the synergistic effect coefficient of dynamic load and freeze-thaw damage, , is the static contact force.

7. The simulation analysis method for dirty roadbed damage under the action of spring thaw dynamics and thawing according to claim 6 is characterized by: The bearing capacity attenuation index is calculated by comparing the attenuation difference between the coupled working condition and the freeze-thaw working condition, and the dynamic load acceleration factor is calculated. Combined with the primary freeze-thaw fatigue life ratio, the freeze-thaw fatigue life ratio is corrected twice to obtain the secondary corrected freeze-thaw fatigue life ratio. The formula is as follows: Calculate the load-bearing capacity attenuation index for freeze-thaw conditions: ； in, is the bearing capacity attenuation index under freeze-thaw conditions; Calculate the total attenuation exponent for the coupled case: ； in, is the total attenuation index of the coupled condition; Calculation of dynamic load acceleration factors : ； Get the second corrected freeze-thaw fatigue life ratio: ； in, is the freeze-thaw fatigue life ratio after secondary correction.

8. The simulation analysis method for dirty roadbed damage under the action of spring thaw dynamics and thawing according to claim 7 is characterized by: Based on the secondary corrected freeze-thaw fatigue life ratio, the disease risk level of the dirty roadbed is divided. The specific steps are as follows: when When the dirty roadbed has not experienced freeze-thaw cycles, the remaining freeze-thaw resistance is at its initial value; when When the soiled roadbed has a strong residual freeze-thaw resistance, it is at a low disease risk level; when When the residual anti-freeze-thaw capacity of the dirty roadbed is medium, it is a medium disease risk level; when When the residual anti-freeze-thaw capacity of the dirty roadbed is weak, the disease risk level is high; when When , the dirty roadbed is in a critical failure state; in, To classify the critical value of low disease risk and medium disease risk level, It is the critical value for dividing the medium disease risk and high disease risk levels.

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