A method for simulating and analyzing diseases of a dirty channel bed under the action of spring thawing power-melting

Abstract

The application provides a kind of spring thaw period power-melting under the disease simulation analysis method of dirty track bed, it is related to track bed disease simulation technical field, comprising: collecting spring thaw period hour by hour temperature, settlement increment and dynamic load parameters of monitoring point before and after train passing, obtaining dirty characteristics and mechanical performance parameters, determining actual freeze-thaw cycle number and critical freeze-thaw cycle number, calculating freeze-thaw damage cumulative index;Extract the cumulative settlement increment characteristic value to calculate uneven settlement index, and modify freeze-thaw fatigue life ratio once in combination with temperature average gradient;Simulate two kinds of working conditions, calculate bearing capacity attenuation index and dynamic load acceleration factor, and modify freeze-thaw fatigue life ratio twice;Divide disease risk grade.The application can adapt to the complex working condition of "temperature transient-settlement uneven", make the evaluation result consistent with the actual disease development, can accurately evaluate the fatigue life under the coupling of multiple factors, provide the basis for disease grade division.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of simulation of dirty track bed diseases, in particular to a simulation analysis method for dirty track bed diseases under the action of dynamic force and thawing in spring thawing period. BACKGROUND

[0002] The dirty track bed is subjected to the superimposed action of freeze-thaw cycle, temperature gradient change and train dynamic load in the spring thawing period, and the traditional analysis method mainly considers the influence of freeze-thaw or dynamic load alone, without constructing a simulation model coupled with multiple factors. For example, only the frost heaving and thawing settlement caused by temperature is concerned, but the fatigue damage caused by the superposition of train dynamic load is ignored; the time correlation between freeze-thaw cycle times and dynamic load is not quantified, resulting in a large deviation between the simulation results and the actual working conditions.

[0003] In the prior art, a spring thawing period dirty track bed disease identification method and device with publication number CN120105848A is disclosed, which establishes a non-continuous grading body cementation contact model through discrete element simulation, introduces a temperature-stiffness / strength coupling factor, constructs a critical dynamic strain model combined with large triaxial experiment data, and then realizes track bed disease evaluation under the coupling action of dynamic force and thawing.

[0004] However, there are still the following deficiencies: as known from the above statements, the data collection dimension is single, the model is static, and the multi-factor coupling effect is not considered; the fluctuation of freeze-thaw cycle frequency caused by the hourly temperature change in the spring thawing period and the influence of uneven settlement of the track bed surface on the bearing capacity are not considered, and the quantitative analysis of time-varying temperature field and spatial deformation is lacking, so that the model cannot adapt to the complex working conditions of "temperature transient-settlement unevenness" in the spring thawing period, and the evaluation results are disconnected with the actual disease development; the independent effects of freeze-thaw damage and dynamic load are not separated from the bearing capacity attenuation, so as to quantize the acceleration mechanism of the synergistic action of the two, and it is difficult to accurately evaluate the fatigue life under the coupling of multiple factors, resulting in that the disease grade division lacks the judgment basis under the coupling of multiple factors.

[0005] The above information disclosed in the background section is only used to enhance the understanding of the background of the present disclosure, and therefore it can include information that does not constitute the prior art known to those of ordinary skill in the art. SUMMARY

[0006] The purpose of the present application is to provide a simulation analysis method for dirty track bed diseases under the action of dynamic force and thawing in spring thawing period, so as to solve the problems raised in the background.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0008] A simulation analysis method for dirty track bed diseases under the action of dynamic force and thawing in spring thawing period, the specific steps comprising:

[0009] S1. Equally spacing monitoring points along the track, collecting hourly temperature in spring thaw period, recording settlement increment of each monitoring point before and after train passing and accumulating as cumulative settlement, synchronously acquiring dynamic load parameters of dirty track bed, collecting dirty characteristics and mechanical properties parameters after spring thaw period, determining actual freeze-thaw cycle number according to hourly temperature, drawing curve of mechanical properties parameters changing with freeze-thaw cycle number through freeze-thaw fatigue test, determining critical freeze-thaw cycle number and calculating freeze-thaw damage cumulative index;

[0010] S2. Correcting critical freeze-thaw cycle number based on dirty characteristics and mechanical properties parameters, calculating freeze-thaw fatigue life ratio according to actual freeze-thaw cycle number and corrected value of critical freeze-thaw cycle number;

[0011] S3. Extracting maximum, minimum and average value from cumulative settlement increment of each monitoring point, calculating uneven settlement index, calculating temperature gradient according to hourly temperature, making first correction to freeze-thaw fatigue life ratio based on both;

[0012] S4. Simulating freeze-thaw working condition and freeze-thaw and dynamic load coupling working condition, acquiring maximum contact force of each working condition by different models according to freeze-thaw damage cumulative index, calculating bearing capacity attenuation index, calculating dynamic load acceleration factor by comparing attenuation difference of coupling working condition and freeze-thaw working condition, making second correction to freeze-thaw fatigue life ratio combining first freeze-thaw fatigue life ratio, acquiring second corrected freeze-thaw fatigue life ratio;

[0013] S5. Dividing disease risk grade of dirty track bed according to second corrected freeze-thaw fatigue life ratio.

[0014] Further, dynamic load parameters include static load contact force and dynamic load amplitude, dirty characteristics parameter is plasticity index; mechanical properties parameter is compressive strength.

[0015] Further, determining actual freeze-thaw cycle number according to hourly temperature, specific steps and formula as follows:

[0016] Setting freeze threshold ;

[0017] When , it is regarded as freezing stage; when , it is regarded as thawing stage, wherein, is hourly temperature, is time variable of spring thaw period;

[0018] Based on hourly temperature and freeze threshold , defining effective freeze-thaw cycle process as follows:

[0019] When hourly temperature From the complete temperature fluctuation cycle that satisfies the melting stage, drops to the freezing stage, and then rises to the melting stage again, it is recorded as 1 effective freeze-thaw cycle process;

[0020] Traverse all time points in the spring thaw period, and obtain the actual freeze-thaw cycle number;

[0021] According to the mechanical property parameters, through the freeze-thaw fatigue test, the critical freeze-thaw cycle number is determined, and the freeze-thaw damage cumulative index is calculated. The specific steps and the formula are as follows:

[0022] Freezing process: put the dirty channel bed material sample into-20℃ environment for 4 hours;

[0023] Melting process: raise the temperature to 20℃ environment and keep for 4 hours;

[0024] Repeat the freezing and melting process, and record the cycle number;

[0025] After completing 10 freeze-thaw cycles, the compressive strength test is carried out on the dirty channel bed material sample;

[0026] When the compressive strength loss rate exceeds the preset threshold value, it is determined that the critical state is reached:

[0027] Draw the freeze-thaw cycle number-compressive strength loss rate curve. The intersection point of the curve and the threshold horizontal line corresponds to the horizontal coordinate of the critical freeze-thaw cycle number;

[0028] Calculate the freeze-thaw damage cumulative index, and the formula is as follows:

[0029] ;

[0030] Wherein, is the freeze-thaw damage cumulative index, is the actual freeze-thaw cycle number, is the critical freeze-thaw cycle number.

[0031] Further, based on the dirty characteristics and mechanical property parameters collected after the spring thaw period, the critical freeze-thaw cycle number is corrected. The formula is as follows:

[0032] ;

[0033] ;

[0034] ;

[0035] Wherein, is the corrected value of the critical freeze-thaw cycle number, is the dirty correction number, is the mechanical correction number, is the critical freeze-thaw cycle number, , , are the plasticity index, strength influence coefficient, compressive strength, respectively, collected after spring thawing period, is the reference compressive strength;

[0036] According to the actual freeze-thaw cycle number and the modified value of the critical freeze-thaw cycle number, the freeze-thaw fatigue life ratio is calculated, and the formula is as follows:

[0037] ;

[0038] wherein, is the freeze-thaw fatigue life ratio of the fouled ballast bed.

[0039] Further, the maximum, minimum and average values are extracted from the cumulative settlement increment of each monitoring point, the uneven settlement index is calculated, the temperature gradient is calculated according to the hourly temperature, and the freeze-thaw fatigue life ratio is modified based on the two, and the formula is as follows:

[0040] ;

[0041] wherein, is the uneven settlement index of the fouled ballast bed, is the maximum value of the cumulative settlement increment of all monitoring points in the spring thawing period, is the minimum value of the cumulative settlement increment of all monitoring points in the spring thawing period, is the average value of the cumulative settlement increment of all monitoring points in the spring thawing period;

[0042] ;

[0043] ;

[0044] wherein, is the freeze-thaw fatigue life ratio after the first modification, is the average temperature gradient, , are the maximum temperature and the minimum temperature of all monitoring points in the spring thawing period at the time, is the distance of the monitoring point corresponding to the maximum temperature and the minimum temperature in the track extension direction at the time, is the index of the time in the spring thawing period, , is the number of times in the spring thawing period.

[0045] Further, the freeze-thaw working condition and the freeze-thaw and dynamic load coupling working condition are simulated, different models are used to obtain each working condition according to the freeze-thaw damage accumulation index, and the specific steps and the formula are as follows:

[0046] 1) In freeze-thaw working condition, the influence of freeze-thaw damage on the elastic modulus of the material is considered:

[0047] ;

[0048] wherein, is the maximum contact force in freeze-thaw working condition, is the contact force in ideal undamaged state, is the elastic modulus attenuation coefficient, ;

[0049] 2) In coupling working condition, the dynamic response of train running is simulated by finite element method, the instantaneous maximum contact force in dynamic process is collected, the influence of freeze-thaw damage on the mechanical properties of the material is considered, and the synergistic effect of dynamic load and freeze-thaw damage is considered;

[0050] ;

[0051] wherein, is the actual maximum contact force in coupling working condition, is the maximum contact force in dynamic load working condition, 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.

[0052] Further, the bearing capacity attenuation index is calculated, the difference between coupling working condition and freeze-thaw working condition is compared, the dynamic load acceleration factor is calculated, the freeze-thaw fatigue life ratio is modified twice by combining the first freeze-thaw fatigue life ratio, the freeze-thaw fatigue life ratio after secondary modification is obtained, and the formula is as follows:

[0053] The bearing capacity attenuation index of freeze-thaw working condition is calculated:

[0054] ;

[0055] wherein, is the bearing capacity attenuation index of freeze-thaw working condition;

[0056] The total attenuation index of coupling working condition is calculated:

[0057] ;

[0058] wherein, is the total attenuation index of coupling working condition;

[0059] The dynamic load acceleration factor is calculated :

[0060] ;

[0061] The freeze-thaw fatigue life ratio after secondary correction is:

[0062] ;

[0063] Wherein, The freeze-thaw fatigue life ratio after secondary correction.

[0064] Further, according to the freeze-thaw fatigue life ratio after secondary correction, the disease risk level of the contaminated track bed is divided, and the specific steps are as follows:

[0065] When , the contaminated track bed does not experience freeze-thaw cycles, and the remaining freeze-thaw resistance is its initial value;

[0066] When , the contaminated track bed has strong remaining freeze-thaw resistance, and is of low disease risk level;

[0067] When , the contaminated track bed has medium remaining freeze-thaw resistance, and is of medium disease risk level;

[0068] When , the contaminated track bed has weak remaining freeze-thaw resistance, and is of high disease risk level;

[0069] When , the contaminated track bed is in a critical failure state;

[0070] Wherein, is the critical value for dividing the low disease risk level and the medium disease risk level, is the critical value for dividing the medium disease risk level and the high disease risk level.

[0071] Compared with the prior art, the beneficial effects of the present application are:

[0072] The present application arranges monitoring points at equal intervals along the track, collects hourly temperature during the spring thaw period, records the settlement increment of each monitoring point on the track surface before and after each train passes, and accumulates the cumulative settlement increment during the spring thaw period. According to the hourly temperature during the spring thaw period, the actual freeze-thaw cycle number is determined, the curve of the mechanical property parameter changing with the freeze-thaw cycle number is drawn through the freeze-thaw fatigue test, and the critical freeze-thaw cycle number and the freeze-thaw damage accumulation index are determined.

[0073] The freeze-thaw fatigue life ratio is corrected once in combination with the uneven settlement index and the temperature gradient, the quantitative analysis of the time-varying temperature field and the spatial deformation is realized, the model can adapt to the complex working conditions of "temperature transient-settlement unevenness" during the spring thaw period, and the evaluation result is consistent with the actual disease development;

[0074] Through simulating freeze-thaw working conditions, freeze-thaw and dynamic load coupling working conditions, the maximum contact force of each working condition is obtained by different models according to the freeze-thaw damage cumulative index, the bearing capacity attenuation index is calculated, the attenuation difference of the coupling working condition and the freeze-thaw working condition is compared, the dynamic load acceleration factor is calculated, the freeze-thaw fatigue life ratio is modified twice in combination with the first freeze-thaw fatigue life ratio, the freeze-thaw fatigue life ratio after secondary modification is obtained, the fatigue life under the coupling of multiple factors can be accurately evaluated, and the determination basis for disease grade division is provided. BRIEF DESCRIPTION OF DRAWINGS

[0075] Figure 1 It is the whole method flowchart of the application;

[0076] Figure 2 It is the fitting schematic diagram of the plasticity index and the dirt correction times;

[0077] Figure 3 It is the fitting schematic diagram of the compressive strength and the mechanical correction coefficient;

[0078] Figure 4 It is the fitting schematic diagram of the uneven settlement index and the freeze-thaw fatigue life ratio after the first modification;

[0079] Figure 5 It is the fitting schematic diagram of the temperature average gradient and the freeze-thaw fatigue life ratio after the first modification;

[0080] Figure 6 It is the fitting schematic diagram of the freeze-thaw damage cumulative index and the maximum contact force of the freeze-thaw working condition;

[0081] Figure 7 It is the fitting schematic diagram of the maximum contact force of the dynamic load working condition and the actual maximum contact force of the coupling working condition;

[0082] Figure 8 It is the fitting schematic diagram of the freeze-thaw damage cumulative index and the actual maximum contact force of the coupling working condition;

[0083] Figure 9 It is the fitting schematic diagram of the dynamic load amplitude and the actual maximum contact force of the coupling working condition;

[0084] Figure 10 It is the fitting schematic diagram of the static load contact force and the actual maximum contact force of the coupling working condition. DETAILED DESCRIPTION

[0085] In order to make the purpose, technical scheme and advantages of the application more clear and obvious, the application is further described in detail below in combination with specific embodiments.

[0086] It should be noted that the technical terms or scientific terms used in the present application should be understood as the general meaning understood by those skilled in the art to which the present application belongs, unless otherwise defined. The "first", "second" and similar words used in the present application do not represent any order, quantity or importance, but are only used to distinguish different components. "Include" or "contain" and similar words mean that the elements or objects before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connected" or "connected" and similar words are not limited to physical or mechanical connection, but can include electrical connection, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to represent the relative positional relationship, when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0087] Embodiment 1:

[0088] Please refer to Figure 1 The present application provides a technical solution:

[0089] A method for simulating and analyzing diseases of a dirty track bed under the action of power-melting in spring thawing period, comprising the following specific steps:

[0090] S1. Equidistantly arranging monitoring points along the track, collecting hourly temperature, recording the settlement increment of each monitoring point before and after the train passes, and accumulating the settlement increment as cumulative settlement, synchronously acquiring dynamic load parameters of the dirty track bed, collecting dirty characteristics and mechanical property parameters after the spring thawing period, determining the actual freeze-thaw cycle number according to the hourly temperature, drawing a curve of the mechanical property parameter changing with the freeze-thaw cycle number through freeze-thaw fatigue test, determining the critical freeze-thaw cycle number, and calculating the freeze-thaw damage accumulation index;

[0091] On the basis of the above-mentioned embodiment, the dynamic load parameters include static load contact force, dynamic load amplitude, and the dirty characteristic parameter is plasticity index; the mechanical property parameter is compressive strength.

[0092] On the basis of the above-mentioned embodiment, equidistantly arranging monitoring points along the track, recording the settlement increment of each monitoring point before and after the train passes, and accumulating the settlement increment as cumulative settlement, the specific method is as follows:

[0093] The laser displacement sensor of ILD2200-40 type is selected and arranged at equal intervals along the track extension direction, such as one monitoring point is arranged every 50 meters to ensure uniform spatial distribution. Each monitoring point is located below the track bed surface of the sleeper to avoid the steel rail support point and avoid the direct action of train load on the sensor. The train entering the monitoring area is detected by the track circuit or radar speedometer, the data collection is started 5 minutes in advance, the initial settlement value is recorded, the settlement data is continuously collected until 5 minutes after the train leaves, the final settlement value is recorded, and the single settlement increment of each monitoring point is calculated. According to the single settlement increment and the total number of trains passing through each monitoring point in the spring thaw period, the cumulative settlement increment of each monitoring point in the spring thaw period is obtained.

[0094] On the basis of the above embodiment, the method for collecting static load contact force, dynamic load amplitude, plasticity index and compressive strength is as follows:

[0095] The collection method of static load contact force is as follows:

[0096] The steel rail stress meter (such as HBM U9C type weighing sensor) is buried under the sleeper corresponding to the monitoring point. After calibration, the zero point data is recorded. When the train stops (no power state), the output voltage of the sensor is collected, and the static load value is converted through the calibration formula , , wherein, is the voltage, is the sensitivity coefficient, is the zero point offset.

[0097] The collection method of dynamic load amplitude is as follows:

[0098] The piezoelectric force sensor is used to start collecting 5 minutes before the train passes, set the trigger threshold, record the maximum value and minimum value of the force signal when the train passes , and the dynamic load amplitude is .

[0099] The collection method of plasticity index is as follows:

[0100] Before and after the beginning of the spring thaw period, 1 time each, 3 track bed samples (between sleepers, track bed slope and ballast shoulder) are taken each time, 100g of samples are taken through 0.5mm sieve, fine particles are retained, liquid limit test is carried out, Casagrande liquid limit instrument is used to measure the liquid limit , plastic limit test is carried out, rolling method is used to measure the plastic limit , and the plasticity index is calculated , .

[0101] The collection method of compressive strength is as follows:

[0102] ​Synchronous with the strength influence coefficient test, the uniaxial compressive peak strength of the dirty road bed test piece is directly obtained, usually a pressure testing machine is used to apply uniaxial pressure to the dirty road bed test piece, and the pressure and deformation data are recorded in real time by the equipment, when the test piece is damaged, the maximum pressure value reached is the uniaxial compressive peak strength, which is used as the compressive strength .

[0103] On the basis of the above embodiment, the collected hourly temperature, cumulative settlement increment, dynamic load parameter, dirty pollution characteristic parameter and mechanical property parameter are normalized, through normalization, the data of different indexes are unified to the interval of 0 to 1, the influence of dimension and value range is eliminated, so that these data have comparability and consistency in subsequent analysis operation.

[0104] On the basis of the above embodiment, the actual freeze-thaw cycle number is determined according to the hourly temperature in the spring thawing period, the specific steps and the formula are as follows:

[0105] Set the freezing threshold ;

[0106] When , it is regarded as the freezing stage; when , it is regarded as the thawing stage, wherein, is the hourly temperature, is the time variable of the spring thawing period;

[0107] Based on the hourly temperature and the freezing threshold , the effective freeze-thaw cycle process is defined as follows:

[0108] When the hourly temperature drops from the thawing stage to the freezing stage, and then rises to the thawing stage again in a complete temperature fluctuation cycle, it is recorded as 1 effective freeze-thaw cycle process;

[0109] The time interval from when the temperature continues to be lower than the threshold to when it rises above the freezing threshold is 3 days, which can ensure the time needed for water to freeze into ice in the pore, if the time interval is too short (such as 1 day), the ice has not completely frozen or the thawing is not sufficient, and the damage effect is not significant; if it is too long (such as 7 days), it belongs to extreme working condition, and 3 days can be used as a regular evaluation benchmark;

[0110] Traverse all time points in the spring thawing period to obtain the actual freeze-thaw cycle number;

[0111] According to the mechanical property parameters, the critical freeze-thaw cycle number is determined through the freeze-thaw fatigue test, and the freeze-thaw damage cumulative index is calculated, the specific steps and the formula are as follows:

[0112] Freezing process: put the dirty road bed sample into a-20℃ environment for 4 hours;

[0113] Melting process: warmed to 20℃ environment, maintained for 4 hours;

[0114] Repeat the freezing and melting process, record the cycle number;

[0115] After completing 10 freeze-thaw cycles, the anti-compressive strength test is performed on the dirty track bed sample, wherein the dirty track bed sample has multiple samples, and after the anti-compressive strength test is performed on the previous dirty track bed sample, the previous dirty track bed sample is no longer used, and another sample is used for the next anti-compressive strength test;

[0116] When the anti-compressive strength loss rate exceeds the preset threshold value, it is determined that the critical state is reached:

[0117] Draw the freeze-thaw cycle number-anti-compressive strength loss rate curve, and the intersection point of the curve and the threshold horizontal line corresponds to the horizontal coordinate of the critical freeze-thaw cycle number;

[0118] Calculate the freeze-thaw damage cumulative index, and the formula is as follows:

[0119] ;

[0120] Wherein, is the freeze-thaw damage cumulative index, the freeze-thaw damage cumulative index is used to combine the actual freeze-thaw cycle number and the critical freeze-thaw cycle number two index parameters to evaluate the damage accumulation degree of the dirty track bed under the action of the actual freeze-thaw cycle, and the greater the freeze-thaw damage cumulative index, the higher the damage accumulation degree;

[0121] In the formula, is the actual freeze-thaw cycle number, is the critical freeze-thaw cycle number.

[0122] On this basis, it needs to be explained that:

[0123] When :

[0124] When the actual freeze-thaw cycle number and the critical freeze-thaw cycle number are closer, the damage of the dirty track bed is more serious. Therefore, the actual freeze-thaw cycle number and the freeze-thaw damage cumulative index are positively correlated.

[0125] The actual freeze-thaw cycle number refers to the complete cycle number of freezing and melting of the dirty track bed due to repeated temperature changes during the spring thawing period.

[0126] Through the actual freeze-thaw cycle number and the critical freeze-thaw cycle number , the freeze-thaw damage cumulative index is calculated, and when is close to , Approaching 1, indicating that the contaminated roadbed freeze-thaw damage is serious, close to the failure critical state.

[0127] When , , indicating that the contaminated roadbed reaches the failure critical state.

[0128] Therefore, the function relationship between the freeze-thaw damage cumulative index and the actual freeze-thaw cycle number , the critical freeze-thaw cycle number is expressed in the form described above.

[0129] S2. Based on the contaminated characteristics and mechanical property parameters, the critical freeze-thaw cycle number is corrected, and the freeze-thaw fatigue life ratio is calculated according to the actual freeze-thaw cycle number and the corrected value of the critical freeze-thaw cycle number;

[0130] Table 1. Change of contaminated correction number with plasticity index

[0131]

[0132] As can be seen from Table 1, under the condition that the critical freeze-thaw cycle number remains 100, with the increase of the plasticity index, the contaminated correction number presents a decreasing rule.

[0133] Specifically, for every increase of 0.5 in the plasticity index, the contaminated correction number stably decreases by 1; from the plasticity index of 5 (contaminated correction number 90) to the plasticity index of 17 (contaminated correction number 66), the plasticity index accumulatively increases by 12, and the contaminated correction number accumulatively decreases by 24, both of which are approximately negatively correlated.

[0134] According to Figure 2 , under the condition that the critical freeze-thaw cycle number is fixed at 100, the contaminated correction number and the plasticity index present a significant negative correlation.

[0135] Table 2. Change of corrected value of critical freeze-thaw cycle number with plasticity index

[0136]

[0137] As can be seen from Table 2, under the condition that the critical freeze-thaw cycle number is fixed at 100, the strength influence coefficient is fixed at 0.8, and the reference compressive strength is fixed at 20, with the gradual increase of the compressive strength (from 21 to 41, increasing by 1 each time), the mechanical correction number presents an increasing rule. For every increase of 1 unit of compressive strength, the mechanical correction number stably increases by 0.8, and both of them present a significant positive correlation.

[0138] From Figure 3It can be seen that under the condition of the same critical freeze-thaw cycle number, strength influence coefficient and reference compressive strength, the mechanical correction number and the compressive strength show a significant positive correlation.

[0139] On the basis of the above examples, the critical freeze-thaw cycle number is corrected based on the soil pollution characteristics and mechanical property parameters collected after spring thawing, and the formula is as follows:

[0140] ;

[0141] ;

[0142] ;

[0143] Among them, The correction value of the critical freeze-thaw cycle number is obtained by quantifying the influence of soil pollution characteristics and mechanical property parameters on freeze-thaw resistance, and converting the critical freeze-thaw cycle number under laboratory standard condition test Into the correction value of the critical freeze-thaw cycle number ;

[0144] In the formula, The soil pollution correction number is The mechanical correction number is The critical freeze-thaw cycle number is , The plasticity index and the compressive strength collected after spring thawing are respectively The reference compressive strength is The strength influence coefficient is ;

[0145] The soil pollution correction number is used to combine the critical freeze-thaw cycle number and the plasticity index to evaluate the freeze-thaw sensitivity of the material caused by fine particle composition and soil pollution adsorption, and the greater the soil pollution correction coefficient, the higher the freeze-thaw sensitivity;

[0146] The mechanical correction number is used to combine the critical freeze-thaw cycle number, the compressive strength and the reference compressive strength to evaluate the ability of the soil pollution roadbed to resist frost heaving stress, and the greater the mechanical correction number, the higher the freeze-thaw resistance;

[0147] On this basis, it needs to be explained that:

[0148] The plasticity index reflects the clay content and water physical properties in the fine-grained soil. When the clay content in the soil pollution roadbed is higher, that is, 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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] On this basis, it should be noted that:

[0153] 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.

[0154] Mechanical correction: through the compressive strength Evaluate the mechanical performance reserve of the contaminated roadbed, The higher the freeze-thaw resistance, the stronger the freeze-thaw resistance, and the critical number needs to be corrected upwards.

[0155] After combining the two, the critical freeze-thaw cycle number under laboratory standard condition test The correction value of the critical freeze-thaw number considering the actual contamination and mechanical properties .

[0156] On this basis, it needs to be explained that:

[0157] For freeze-thaw resistance design, the reference compressive strength Can be set as the initial compressive strength of the contaminated roadbed before being subjected to freeze-thaw cycles.

[0158] Therefore, the function relationship between the freeze-thaw damage accumulation index and the actual freeze-thaw cycle number , the critical freeze-thaw cycle number is expressed in the form of the above function.

[0159] Therefore, the function relationship between the correction value of the critical freeze-thaw cycle number And the contamination correction number , the mechanical correction number is expressed in the form of the above function.

[0160] On the basis of the above embodiment, according to the actual freeze-thaw cycle number and the correction value of the critical freeze-thaw cycle number, the freeze-thaw fatigue life ratio is calculated, and the formula is as follows:

[0161] ;

[0162] Among them, The freeze-thaw fatigue life ratio of the contaminated roadbed;

[0163] The freeze-thaw fatigue life ratio represents the ratio of the actual freeze-thaw damage degree to the critical damage threshold;

[0164] When , the actual freeze-thaw number does not reach the critical value, and the contaminated roadbed is in a safe state;

[0165] When , the actual freeze-thaw number exceeds the critical value, and the contaminated roadbed material has been damaged by fatigue;

[0166] The freeze-thaw fatigue life ratio is used to evaluate the remaining life of the contaminated roadbed in combination with the actual freeze-thaw cycle number and the correction value of the critical freeze-thaw cycle number. The smaller the freeze-thaw fatigue life ratio, the longer the remaining life of the contaminated roadbed;

[0167] On this basis, it needs to be explained that:

[0168] Actual freeze-thaw cycle number Directly reflects the number of frost-heave thaw-shrink cycle loads that the material can withstand. In each freeze-thaw cycle, the material will expand due to water freezing and shrink due to melting, causing micro-cracks in the material, leading to cumulative damage. The more cycles, the more cumulative damage, the closer to or beyond the critical damage threshold, resulting in a freeze-thaw fatigue life ratio closer to 1, and the material's remaining life becoming shorter and shorter;

[0169] Modified value of critical freeze-thaw cycle number The critical damage threshold considering the dirt characteristics and mechanical properties, reflecting the material's ability to resist freeze-thaw damage, The greater, the more freeze-thaw cycles the material can withstand, the stronger the freeze-thaw resistance, and the same actual freeze-thaw cycle number The lower the damage, the less likely to reach the damage threshold, the closer to 0 the freeze-thaw fatigue life ratio, and the longer the material's remaining life.

[0170] Therefore, the above form is used to express the functional relationship between the freeze-thaw fatigue life ratio And the actual freeze-thaw cycle number , the modified value of the critical freeze-thaw cycle number .

[0171] S3. Extract the maximum, minimum and average values from the cumulative settlement increment of each monitoring point, calculate the uneven settlement index, calculate the temperature gradient based on the hourly temperature, and make a correction to the freeze-thaw fatigue life ratio based on both;

[0172] Based on the above embodiment, the uneven settlement index of the dirt path bed is calculated, and the formula is as follows:

[0173] ;

[0174] Among them, The uneven settlement index of the dirt path bed, the uneven settlement index is used in combination with the maximum value, the minimum value, and the average value of the cumulative settlement increment of the three index parameters, to evaluate the settlement uniformity of the dirt path bed under the action of freeze-thaw cycles, and the greater the uneven settlement index, the more significant the settlement difference, the more uneven the stress distribution in the material, and the higher the risk of freeze-thaw fatigue damage.

[0175] In the formula, The maximum value of the cumulative settlement increment of all monitoring points in the spring thaw period, The minimum value of the cumulative settlement increment of all monitoring points in the spring thaw period, The average value of the cumulative settlement increment of all monitoring points in the spring thaw period;

[0176] On this basis, it needs to be noted that:

[0177] ) reflects the dispersion degree of the settlement increment, the greater the difference, the more significant the difference in settlement at different positions, thereby increasing the uneven settlement index

[0178] ) as a reference value, for normalization processing, so that the uneven settlement index has dimensionless characteristics, facilitating comparison under different working conditions.

[0179] Therefore, the function relationship between the uneven settlement index and the above-mentioned formula ) is expressed.

[0180] Table 3. The change of the first corrected freeze-thaw fatigue life ratio with the uneven settlement index and the average temperature gradient

[0181]

[0182] As can be seen from Table 3, when the freeze-thaw fatigue life ratio of the dirty channel bed is fixed at 5, the first corrected freeze-thaw fatigue life ratio shows a continuously increasing trend with the increase of the uneven settlement index and the average temperature gradient.

[0183] Specifically, the uneven settlement index and the average temperature gradient jointly promote the gradual rise of the first corrected freeze-thaw fatigue life ratio (e.g. from 5.1 of serial number 1, to 9.47 when the serial number is 25).

[0184] As can be seen from Figure 4 , Figure 5 , when the freeze-thaw fatigue life ratio of the dirty channel bed is fixed at 5, the first corrected freeze-thaw fatigue life ratio shows a significant positive correlation with the uneven settlement index and the average temperature gradient:

[0185] Uneven settlement index influence: with the increase of the uneven settlement index, the first corrected freeze-thaw fatigue life ratio continuously increases, the fitting line has high degree of adhesion to the data points, and the correlation is significant;

[0186] Temperature average gradient influence: when the average temperature gradient increases, the first corrected freeze-thaw fatigue life ratio also stably rises, the fitting line accurately depicts the change trend, and the positive correlation is clear.

[0187] On the basis of the above embodiments, the freeze-thaw fatigue life ratio is corrected once based on the uneven settlement index and the temperature gradient, and the formula is as follows:

[0188] ​​​​​​ ;

[0189] ;

[0190] 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.

[0191] 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.

[0192] On this basis, it should be noted that:

[0193] 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.

[0194] 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( )、( ) is the functional relationship between them.

[0195] On this basis, it should be noted that:

[0196] Where, is the freeze-thaw fatigue life ratio after correction.

[0197] The once-revised freeze-thaw fatigue life ratio is revised once in combination with the uneven settlement index and the temperature gradient of the two index parameters, and the smaller the once-revised freeze-thaw fatigue life ratio is, the longer the remaining life is.

[0198] When the uneven settlement index increases, it means that the difference in settlement of each part of the track bed increases, and the stress distribution inside the structure is more uneven, and under the action of freeze-thaw cycles, such uneven stress will accelerate the fatigue damage of the track bed material, leading to a shorter freeze-thaw fatigue life, and thus the once-revised freeze-thaw fatigue life ratio increases; when the temperature average gradient increases, the temperature difference between different positions of the track bed increases, and the difference in the degree of thermal expansion and contraction of the material increases, and the thermal stress generated thereby repeatedly acts on the track bed, accelerating the deterioration of the material performance, so the once-revised freeze-thaw fatigue life ratio increases.

[0199] Therefore, the once-revised freeze-thaw fatigue life ratio is positively correlated with the uneven settlement index and the temperature average gradient .

[0200] Therefore, the function relationship between the once-revised freeze-thaw fatigue life ratio and the uneven settlement index and the temperature average gradient is expressed in the above form.

[0201] S4. Simulate freeze-thaw conditions and freeze-thaw and dynamic load coupling conditions, obtain the maximum contact force in each condition by different models according to the freeze-thaw damage accumulation index, calculate the bearing capacity decay index, calculate the dynamic load acceleration factor by comparing the decay difference between the coupling condition and the freeze-thaw condition, revise the freeze-thaw fatigue life ratio twice in combination with the once freeze-thaw fatigue life ratio, and obtain the twice-revised freeze-thaw fatigue life ratio.

[0202] Table 4. Change of maximum contact force in freeze-thaw conditions with freeze-thaw damage accumulation index

[0203]

[0204] As can be seen from Table 4, when the contact force in the ideal undamaged state (fixed at 100) and the elastic modulus decay coefficient (fixed at 1) remain unchanged, the maximum contact force in the freeze-thaw condition continuously decreases with the increase of the freeze-thaw damage accumulation index, and the decreasing amplitude becomes more and 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 the damage, and there is a clear negative correlation between the two.

[0205] 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.

[0206] 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:

[0207] 1) Under freeze-thaw conditions, consider the effect of freeze-thaw damage on the elastic modulus of the material:

[0208] ;

[0209] 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.

[0210] Where, is the contact force under ideal damage-free condition, is the elastic modulus attenuation coefficient, ;

[0211] 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

[0212] 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;

[0213] 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.

[0214] On this basis, it should be noted that:

[0215] 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.

[0216] 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.

[0217] 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 ).

[0218] 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.

[0219] Table 5. Variation of the actual maximum contact force of the coupling condition with the freeze-thaw damage accumulation index

[0220]

[0221] 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.

[0222] Depend on Figures 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:

[0223] The actual maximum contact force of the coupling condition increases with the increase of the maximum contact force of the dynamic load condition and the amplitude of the dynamic load, showing a positive correlation.

[0224] The actual maximum contact force of the coupling condition decreases with the increase of the freeze-thaw damage cumulative index and the static load contact force, showing a negative correlation.

[0225] 2) In the coupling condition, the finite element simulation is used to simulate the dynamic response of the train in operation, the instantaneous maximum contact force in the dynamic process is collected, the influence of freeze-thaw damage on the mechanical properties of the material is considered, and the synergistic effect of dynamic load and freeze-thaw damage is considered;

[0226] ;

[0227] wherein, The actual maximum contact force of the coupling condition is used to combine the maximum contact force of the dynamic load condition, the freeze-thaw damage cumulative index, the amplitude of the dynamic load, and the static load contact force four index parameters to evaluate the failure probability of the material under the dynamic load and freeze-thaw coupling condition, and the greater the actual maximum contact force of the coupling condition, the higher the failure probability;

[0228] In the formula, is the coupling effect coefficient, , is the synergistic effect coefficient of dynamic load and freeze-thaw damage, , is the amplitude of the dynamic load, is the static load contact force;

[0229] It means that the weakening effect of freeze-thaw damage on contact force is in the medium to significant range. Because The freeze-thaw damage degree itself represents the freeze-thaw damage degree, The greater the freeze-thaw damage degree, the more serious the material damage.

[0230] If , it will lead to the weakening effect of freeze-thaw damage on contact force being underestimated, which is contradictory to the phenomenon of “freeze-thaw significantly reducing the strength of the material” in the experiment;

[0231] If , it may make the contact force decay too much, and the superposition result of the synergistic effect of the dynamic load exceeds the actual failure range of the material.

[0232] The specific value range of the coupling effect coefficient is determined by carrying out material mechanical property tests under different freeze-thaw cycle times, measuring the change law of the contact force with the freeze-thaw damage cumulative index, applying dynamic load to each freeze-thaw sample, recording the contact force decay amplitude, and establishing a linear relationship of the contact force decay rate .

[0233] Statistical groups of experimental data, by least squares fitting to get the mean and fluctuation range, ensure that the fitting error is within an acceptable range.

[0234] The specific value range of the concrete, through finite element simulation of different The contact force response under the value, compared with the stress distribution of dynamic load and freeze-thaw damage coupling:

[0235] Fixed and , change , calculate the contact force increment ratio;

[0236] When , the contact force increment is not consistent with the physical observation;

[0237] When , the contact force increment exceeds the measured data of material failure.

[0238] Therefore, set .

[0239] On this basis, it needs to be explained that:

[0240] The maximum contact force of the dynamic load working condition is the basis load of dynamic action when the train is running, reflecting the instantaneous load peak value produced by factors such as vibration and speed change in the train running process. In the coupling working condition, the synergistic effect of freeze-thaw damage and dynamic load will further amplify the contact force is corrected based on . Therefore, the actual maximum contact force of the coupling working condition and the maximum contact force of the dynamic load working condition are positively correlated.

[0241] With the increase of , the material experiences multiple expansion and contraction in the freeze-thaw cycle, internal microcracks, pore expansion, crystal structure damage, and significant reduction in mechanical properties such as elastic modulus, strength, and bearing capacity, so the maximum contact force that can be sustained naturally decreases. Therefore, the actual maximum contact force of the coupling working condition and the cumulative index of freeze-thaw damage are negatively correlated.

[0242] The dynamic load amplitude refers to the fluctuation amplitude of the dynamic load relative to the static load, that is, the additional load produced by train vibration. When increases, the impact effect of dynamic load on the dirty track bed is enhanced, while freeze-thaw damage will weaken the ability to resist dynamic impact, and the synergistic effect of the two will further amplify the contact force. In the formula, the synergistic effect coefficient​ and The ratio of the two reflects this effect, represents the correction of the contact force by the ratio of the dynamic load amplitude and the static load. Therefore, the actual maximum contact force of the coupled working condition and the dynamic load amplitude are positively correlated, and the actual maximum contact force of the coupled working condition and the static load contact force are negatively correlated.

[0243] Therefore, the functional relationship between the actual maximum contact force of the coupled working condition and the maximum contact force of the dynamic load working condition, the cumulative index of freeze-thaw damage, the dynamic load amplitude, and the static load contact force is expressed in the form above.

[0244] The calculation formula of the maximum contact force of the dynamic load working condition is as follows:

[0245] ;

[0246] wherein, is the maximum contact force of the dynamic load working condition, which is used to combine the static load contact force and the dynamic load amplitude to evaluate the additional effect of the dynamic load on the bearing capacity and fatigue life of the structure, and The greater the value is, the greater the additional effect of the dynamic load on the bearing capacity and fatigue life of the structure is.

[0247] is the dynamic amplification factor, when it is ordinary railway, ; when it is high-speed railway, ;

[0248] Theoretical calculation shows that when the wheel passes through the ideal track at the lowest speed on the ordinary railway, the dynamic contact force is about 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 load and poor track conditions.

[0249] In the design specification of high-speed railway, when the quasi-static model is used for calculation, the lowest dynamic amplification effect needs to be considered. For example, when the train passes through the ideal ballastless track at the design speed, based on the Hertz contact theory and the multi-body dynamics model, it is calculated that the dynamic contact force is at least 1.3 times the static load; the domestic high-speed railway shows that the dynamic amplification factor is generally between 1.3-1.6 under normal maintenance conditions, and 1.8 as the upper limit has covered the extreme working condition.

[0250] On this basis, it needs to be noted that:

[0251] When the dynamic load frequency is far away from the material natural frequency, the system can be approximately linearly responsive, at which time the contact force increment caused by the dynamic load is linearly related to the load amplitude (i.e. ), which is superimposed on the static load contact force The maximum contact force is formed.

[0252] When , the dynamic load does not cause contact force amplification (only static load effect);

[0253] When , due to inertial force, vibration coupling and other factors, the contact force exceeds the static load value, The greater the dynamic effect is more significant.

[0254] Therefore, the maximum contact force of the dynamic load working condition Based on the static load-dynamic load superposition of the linear system, the dynamic amplification effect is quantified.

[0255] Therefore, the above form is used to express the functional relationship between the maximum contact force of the dynamic load working condition and the static load contact force, the dynamic amplification coefficient, and the dynamic load amplitude.

[0256] On the basis of the above embodiment, according to the maximum contact force under each working condition, the bearing capacity attenuation index of different working conditions is calculated, and the dynamic load acceleration factor is obtained. Combined with the first modified freeze-thaw fatigue life ratio and the dynamic load acceleration factor, the freeze-thaw fatigue life ratio is secondly modified, and the secondly modified freeze-thaw fatigue life ratio is obtained. The formula is as follows:

[0257] Calculate the bearing capacity attenuation index of freeze-thaw working condition:

[0258] ;

[0259] Among them, is the bearing capacity attenuation index of freeze-thaw working condition;

[0260] Calculate the total attenuation index of coupling working condition:

[0261] ;

[0262] Among them, is the total attenuation index of coupling working condition;

[0263] On this basis, it needs to be explained that:

[0264] The above function quantifies the degradation of bearing capacity in relative attenuation amount, (A) is the absolute attenuation amount of contact force caused by damage, (B) is the relative attenuation ratio, which can be dimensionless to reflect the degradation degree of bearing capacity. Calculate the dynamic load acceleration factor:

[0265]

[0266] ; ​​​

[0267] wherein, is a dynamic load acceleration factor, the dynamic load acceleration factor is used to combine the total attenuation index of the coupling working condition and the bearing capacity attenuation index 2 of the freeze-thaw working condition. Index parameter, quantifying the acceleration effect of dynamic load on freeze-thaw damage, the greater the dynamic load acceleration factor, the more significant the acceleration effect of dynamic load on freeze-thaw damage.

[0268] The freeze-thaw fatigue life ratio after secondary correction is:

[0269]

[0270] wherein, The freeze-thaw fatigue life ratio after secondary correction is used to combine the freeze-thaw fatigue life ratio after primary correction and the dynamic load acceleration factor 2 index parameters, quantifying the influence of the synergistic effect on the life, and the greater the freeze-thaw fatigue life ratio after secondary correction, the shorter the remaining life;

[0271] On this basis, it should be noted that:

[0272] Reflecting the “basic weakening” of freeze-thaw on the fatigue life of the dirty track bed, which is the embodiment of static damage;

[0273] Dynamic load cannot independently cause freeze-thaw damage, but will accelerate crack propagation through vibration stress on the basis of the degradation of the dirty track bed caused by freeze-thaw, is a quantitative factor for this acceleration effect.

[0274] In the material fatigue damage theory, Miner's rule, when two kinds of loads act synergistically, if the damage rate of the latter load depends on the material state caused by the former load, then the damage accumulation often shows a product relationship. Therefore, freeze-thaw first reduces the basic performance of the dirty track bed, and dynamic load further accelerates fatigue failure on the basis of freeze-thaw damage, so the life ratio under the coupling effect needs to be multiplied by . .

[0275] Therefore, the above form is used to express the functional relationship between the freeze-thaw fatigue life ratio after secondary correction and the freeze-thaw fatigue life ratio after primary correction and the dynamic load acceleration factor.

[0276] S5. According to the freeze-thaw fatigue life ratio after secondary correction, the disease risk grade of the dirty track bed is divided.

[0277] On the basis of the above embodiment, according to the freeze-thaw fatigue life ratio after secondary correction, the disease risk grade of the dirty track bed is divided, and the specific steps are as follows:

[0278] When ​When the value of the ratio is greater than 1, the fouled track bed has strong residual anti-freeze-thaw capability, and is of a low disease risk level;

[0279] When the value of the ratio is greater than 1, the fouled track bed has strong residual anti-freeze-thaw capability, and is of a low disease risk level; When the value of the ratio is greater than 1, the fouled track bed has strong residual anti-freeze-thaw capability, and is of a low disease risk level;

[0280] When the value of the ratio is greater than 1, the fouled track bed has strong residual anti-freeze-thaw capability, and is of a low disease risk level;

[0281] When the value of the ratio is greater than 1, the fouled track bed has strong residual anti-freeze-thaw capability, and is of a low disease risk level; When the value of the ratio is greater than 1, the fouled track bed has strong residual anti-freeze-thaw capability, and is of a low disease risk level;

[0282] When the value of the ratio is greater than 1, the fouled track bed has strong residual anti-freeze-thaw capability, and is of a low disease risk level;

[0283] wherein, is a critical value for dividing the low disease risk level and the medium disease risk level, is a critical value for dividing the medium disease risk level and the high disease risk level.

[0284] According to the mechanical model of the fouled track bed and the freeze-thaw fatigue damage theory, and in combination with the dynamic load action principle, the theoretical values of the track bed structure reaching different disease levels under different freeze-thaw fatigue life ratios are derived. For example, by establishing a fatigue damage constitutive equation of the track bed under the coupling action of freeze-thaw and dynamic load, the twice-revised freeze-thaw fatigue life ratio corresponding to different states such as the beginning of obvious structural damage of the track bed and the influence on driving safety is calculated, so as to determine the theoretical values of and.

[0285] The above formulas are all dimensionless numerical calculations, and the formulas are obtained by software simulation of a large amount of data to obtain the most real situation, and the preset parameters in the formulas are set by a person skilled in the art according to the actual situation.

[0286] The above embodiments can be realized wholly or partially by software, hardware, firmware or any combination thereof. When realized by software, the above embodiments can be realized in the form of a computer program product wholly or partially. A person skilled in the art can realize that the units and algorithm steps of the examples described in combination with the embodiments disclosed herein can be realized by electronic hardware, or a combination of computer software and electronic hardware. Whether the functions are executed by hardware or software methods depends on the specific application and design constraints of the technical solutions.

[0287] ​​​​The units described as separate components may or may not be physically separate, and the components displayed as units may or may not be physical units, and may be located in one place, or distributed on multiple network units. Part or all of the units can be selected to achieve the purpose of the embodiment of the present application according to actual needs.

[0288] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for simulating and analyzing diseases of a ballast bed under the action of dynamic thawing in spring thawing period, characterized in that, The specific steps include: S1. Equidistantly arrange monitoring points along the track, collect hourly temperature in the spring thaw period, record the settlement increment of each monitoring point before and after the train passes, and accumulate the settlement increment into cumulative settlement, simultaneously obtain the dynamic load parameter of the dirty track bed, collect the dirt characteristics and mechanical property parameters after the spring thaw period, determine the actual freeze-thaw cycle number according to the hourly temperature, draw the curve of the mechanical property parameter changing with the freeze-thaw cycle number through the freeze-thaw fatigue test, determine the critical freeze-thaw cycle number, and calculate the freeze-thaw damage accumulation index; S2. Correct the critical freeze-thaw cycle number based on the dirt characteristics and mechanical property parameters, calculate the freeze-thaw fatigue life ratio according to the actual freeze-thaw cycle number and the corrected value of the critical freeze-thaw cycle number; S3. Extract the maximum, minimum and average values from the cumulative settlement increment of each monitoring point, calculate the uneven settlement index, calculate the temperature gradient according to the hourly temperature, and correct the freeze-thaw fatigue life ratio based on the two; S4. Simulate the freeze-thaw working condition and the freeze-thaw and dynamic load coupling working condition, obtain the maximum contact force of each working condition by different models according to the freeze-thaw damage accumulation index, calculate the bearing capacity attenuation index, calculate the dynamic load acceleration factor by comparing the attenuation difference between the coupling working condition and the freeze-thaw working condition, correct the freeze-thaw fatigue life ratio twice in combination with the freeze-thaw fatigue life ratio, and obtain the freeze-thaw fatigue life ratio after the second correction; S5. Divide the disease risk grade of the dirty track bed according to the freeze-thaw fatigue life ratio after the second correction.

2. The method according to claim 1, wherein the method is characterized by: The dynamic load parameter includes static load contact force and dynamic load amplitude, the dirt characteristic parameter is plasticity index, and the mechanical property parameter is compressive strength.

3. The method according to claim 2, wherein the method is characterized by: Determine the actual freeze-thaw cycle number according to the hourly temperature, and the specific steps and formulas are as follows: Setting a freeze threshold ; When is considered as a freezing phase; when is considered as a thawing phase, wherein, is the hourly temperature, is the time variable of the spring thaw period; Based on hourly temperatures and a freeze threshold , define an effective freeze-thaw cycle process as follows: When the hourly temperature From the complete temperature fluctuation cycle that satisfies the melting stage descending to the freezing stage, and then rising to the melting stage again, it is recorded as 1 effective freeze-thaw cycle process; Traverse all time points in the spring thaw period to obtain the actual freeze-thaw cycle number; According to the mechanical property parameter, determine the critical freeze-thaw cycle number through the freeze-thaw fatigue test, calculate the freeze-thaw damage accumulation index, and the specific steps and formulas are as follows: Freezing process: place the dirty track bed material sample in a-20℃ environment for 4 hours; Melting process: warm up to a 20℃ environment and keep for 4 hours; Repeat the freezing and melting process and record the cycle number; After completing 10 freeze-thaw cycles, test the compressive strength of the dirty track bed material sample; When the compressive strength loss rate exceeds the preset threshold, it is determined that the critical state is reached: Draw the curve of freeze-thaw cycle number-compressive strength loss rate, and the intersection point of the curve and the threshold horizontal line corresponds to the critical freeze-thaw cycle number; Calculate the freeze-thaw damage accumulation index, and the formula is as follows: ； wherein, is the freeze-thaw damage cumulative index, is the actual number of freeze-thaw cycles, is the critical number of freeze-thaw cycles.

4. The method according to claim 3, wherein the method is characterized by: Correct the critical freeze-thaw cycle number based on the dirt characteristics and mechanical property parameters collected after the spring thaw period, and the formula is as follows: ； ； ； wherein, is a correction value for the critical freeze-thaw cycle number, is a correction value for the number of times of dirtiness, is a correction value for the number of times of mechanics, is a critical freeze-thaw cycle number, , , are a plasticity index, a strength influence coefficient, and a compressive strength, respectively, collected after the spring thawing period, is a reference compressive strength; Calculate the freeze-thaw fatigue life ratio according to the actual freeze-thaw cycle number and the corrected value of the critical freeze-thaw cycle number, and the formula is as follows: ； wherein is the ratio of the freeze-thaw fatigue life of the soiled track bed.

5. The method according to claim 4, wherein the method is characterized by: Extract the maximum, minimum and average values from the cumulative settlement increment of each monitoring point, calculate the uneven settlement index, calculate the temperature gradient according to the hourly temperature, and correct the freeze-thaw fatigue life ratio once based on the two, and the formula is as follows: ； wherein, is the non-uniform settling index of the dirty road bed, is the maximum value of the cumulative settlement increment of all monitoring points in the spring thaw period, is the minimum value of the cumulative settlement increment of all monitoring points in the spring thaw period, is the average value of the cumulative settlement increment of all monitoring points in the spring thaw period; ； wherein, is the once modified freeze-thaw fatigue life ratio, is the temperature average gradient, , are the maximum temperature and the minimum temperature of all monitoring points at the i-th time point in the spring thaw period, respectively, are the maximum temperature and the minimum temperature of all monitoring points at the i-th time point in the spring thaw period, respectively, is the distance of the monitoring points corresponding to the maximum temperature and the minimum temperature along the track extension direction at the i-th time point, is the index of the time point in the spring thaw period, , , is the number of time points in the spring thaw period.

6. The method according to claim 5, wherein the method is characterized by: The maximum contact force of each working condition was obtained by different models according to the freeze-thaw damage cumulative index, and the specific steps and formulas are as follows: 1) In the freeze-thaw working condition, the influence of freeze-thaw damage on the elastic modulus of the material was considered: ； wherein, is the maximum contact force for freeze-thaw conditions, is the contact force for ideal non-damaging conditions, is the modulus of elasticity decay coefficient, ; 2) In the coupling working condition, the dynamic response of the train was simulated by finite element method, the instantaneous maximum contact force in the dynamic process was collected, the influence of freeze-thaw damage on the mechanical properties of the material was considered, and the synergistic effect of dynamic load and freeze-thaw damage was considered; ； wherein, is the actual maximum contact force for the coupled condition, is the maximum contact force for the dynamic load condition, 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 load contact force.

7. The method according to claim 6, wherein the method is characterized by: The bearing capacity attenuation index was calculated, the difference in attenuation between the coupling working condition and the freeze-thaw working condition was compared, the dynamic load acceleration factor was calculated, the freeze-thaw fatigue life ratio was twice corrected combined with the first freeze-thaw fatigue life ratio, and the twice corrected freeze-thaw fatigue life ratio was obtained, and the formulas are as follows: The bearing capacity attenuation index of freeze-thaw working condition was calculated: ； wherein, is the bearing capacity degradation index for freeze-thaw conditions; The total attenuation index of coupling working condition was calculated: ； wherein, is the total attenuation index for the coupling condition; Computing dynamic load acceleration factors : ； The twice corrected freeze-thaw fatigue life ratio was obtained: ； wherein, N is the ratio of the freeze-thaw fatigue life after the second correction.

8. The method according to claim 7, wherein the method is characterized by: According to the twice corrected freeze-thaw fatigue life ratio, the disease risk level of the dirty track bed was divided, and the specific steps are as follows: When the soiled road bed has not experienced freeze-thaw cycles, the remaining freeze-thaw resistance is its initial value; When the soil is contaminated, the residual freeze-thaw resistance of the roadbed is strong, and the disease risk level is low. When the remaining freeze-thaw resistance of the soiled road bed is medium, the disease risk level is medium. When the soil path bed has weak residual freeze-thaw resistance and a high disease risk level. When the soiled roadway bed is in a critical failure state; wherein is the critical value for dividing the low disease risk and the medium disease risk grades, is the critical value for dividing the medium disease risk and the high disease risk grades.

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