A subgrade analysis and calculation method considering local degradation of permafrost subgrade

Abstract

The present application relates to the field of frozen soil subgrade structure calculation, in particular to a subgrade analysis calculation method considering local degradation of permafrost subgrade. The present application assumes that the diameter D and height H of the pavement settlement area are the target settlement, assumes the position, size and degradation degree of the degradation area, carries out numerical analysis through finite element or discrete element, obtains the post-construction pavement settlement, compares the difference between the simulated post-construction pavement settlement and the target settlement, randomly changes or changes the position, size and degradation degree of the degradation area according to the rule, repeatedly tries and calculates, and finally obtains the foundation degradation position, size and degradation degree which almost coincide with the target settlement. The degradation areas determined by a plurality of sets of degradation area parameters are established in the finite element or discrete element model, are combined with other load calculation conditions of the pavement load respectively, the corresponding subgrade structure load effect of each degradation area is calculated, and the most unfavorable value or the average value is taken to design or evaluate the subgrade strength, deformation and stability.

Description

Technical Field

[0001] This invention relates to the field of calculation technology for permafrost subgrade structures, and specifically to a subgrade analysis and calculation method that considers the local deterioration of permafrost subgrades. Background Technology

[0002] When constructing roads in permafrost regions, the freeze-thaw cycle of the roadbed must be considered. During the freeze-thaw process, moisture migrates and forms ice lenses beneath the roadbed. The melting of these ice lenses can lead to extreme deterioration of local soil properties, resulting in a reduction in the local bearing capacity of the roadbed and causing uneven settlement of the roadbed in permafrost regions.

[0003] Currently, subgrade structure design schemes mainly consider overall thaw settlement characteristics, while local soil deterioration is largely determined by the designers' experience. Subgrade calculations require load combinations that account for soil deterioration. Due to the nonlinearity of soil materials, the relationship between load effects and load variables is nonlinear, necessitating load combinations before directly deriving the load effects. However, because the extent and degree of soil deterioration after freeze-thaw cycles are difficult to predict, subgrade verification during the design phase only roughly estimates the impact of local soil deterioration on the subgrade based on the overall thaw settlement characteristics of the foundation soil, or assumes the soil is a multi-layered homogeneous material. Currently, there is a lack of subgrade design methods that consider localized soil deterioration after freeze-thaw cycles.

[0004] The patent, with patent number CN202210247719.X and titled "A Method for Comparing and Selecting Road Base Course Schemes in Seasonally Frozen Soil Areas," discloses a method for comparing and selecting road base course schemes in seasonally frozen soil areas. It considers the impact of frost heave and thaw settlement on the benefit and cost indicators of the road base course. However, it only provides a road design method and does not provide a roadbed design method. It does not consider the superposition method of the effects of multiple nonlinear influencing factors on the bearing capacity, deformation, and stability of the foundation, nor does it consider the impact of the deterioration of the underlying frozen soil on the deformation of the roadbed.

[0005] The patent with patent number CN202310767954.4 and patent title is "An Evaluation Method for the Degree of Freeze-Thaw Damage to Frozen Soil Subgrade Based on Sequential Deviation". It is based on ice-containing sequential deviation and considers the influence of external temperature changes to obtain the freeze-thaw damage field of the subgrade, revealing the spatial distribution of the freeze-thaw damage of the subgrade. It can simulate and calculate the surface damage of the subgrade. However, it cannot calculate the deep local deterioration of the subgrade that is prone to local subsidence. Summary of the Invention

[0006] In view of this, in order to solve the above problems, the present invention provides a subgrade analysis and calculation method that takes into account the local deterioration of permafrost subgrade.

[0007] To achieve the above objectives, the technical solution adopted by this invention is as follows: a subgrade analysis and calculation method considering local deterioration of permafrost subgrade, comprising the following steps:

[0008] S1: Determine the size of the road subsidence area, and determine the diameter D and height H of the subsidence area according to the target guidance to obtain the target subsidence;

[0009] S2: Assuming the location, size, and degree of deterioration of the deteriorated area, establish a calculation model and conduct numerical analysis using finite element or discrete element methods to obtain the post-construction road surface settlement.

[0010] S3: Compare the difference between the simulated and predicted post-construction pavement settlement and the target settlement, randomly change or intentionally change the location, size and degree of deterioration of the deteriorated area according to the pattern, and repeatedly calculate to finally obtain multiple sets of foundation deterioration location, size and degree of deterioration that almost match the target settlement.

[0011] S4: Assuming the foundation deterioration meets the above-mentioned location, size, and degree of deterioration, simulate the construction process. Combined with the given roadbed scheme, consider load combinations such as vehicle loads, and verify the stress and deformation of the roadbed structure under multi-condition nonlinear load combinations. When three sets of deterioration are taken, the most unfavorable value is taken as the reference value; when more than three sets of values ​​are taken, the average value is taken as the reference value for design or evaluation.

[0012] Furthermore, the specific method of step S2 is as follows: the deteriorated area is located directly below or to the side of the subsidence area, and multiple sets of assumed deteriorated area parameters are used, including the diameter d. i Deterioration area height b i The deteriorated area is h away from the road surface i The distance L from the center of the deteriorated area to the center of the subsidence i A finite element or discrete element model was established, and the elastic modulus, internal friction angle, and cohesion parameters of the soil within the localized deterioration zone were set to minimum values ​​to simulate the rapid deterioration of the soil caused by water migration. The settlement range parameter D was obtained through trial calculation. i H i .

[0013] Furthermore, the specific method of step S3 is as follows: Based on the principle of what is beneficial or detrimental to the subsidence area, the location, size, and degree of deterioration of the deteriorated area are randomly or systematically and purposefully changed. The maximum and minimum values ​​of each parameter are calculated to obtain the feasible region of the deteriorated area parameters. The initial parameters are repeatedly modified for trial calculations. The subsidence area parameters D calculated by comparing them with those of the assumed deteriorated area are then compared. i H i Given the target subsidence area parameters D and H, select 3 or more sets of assumed subsidence area parameters di, bi, hi, Li (i∈(3,n)) that meet the error range.

[0014] Furthermore, the diameter D and height H of the subsidence area in step S1) are determined statistically based on the road damage situation in the permafrost region.

[0015] Compared with the prior art, the advantages of the present invention are as follows:

[0016] 1. This invention determines the settlement range based on target orientation, calculates settlement by randomly selecting or purposefully modifying local foundation deterioration parameters, and iteratively calculates to make the calculated settlement closer to the target settlement, thereby determining the local foundation deterioration parameters. This invention proposes a method for calculating local roadbed deterioration, which is more objective than traditional experience-based evaluation and design methods.

[0017] 2. This invention provides a foundation verification method that considers local soil deterioration. The verification process can take into account the nonlinear superposition of local soil deterioration and other loads acting on the foundation soil, which can more comprehensively evaluate the foundation bearing capacity, deformation and stability. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of roadbed deterioration according to the present invention.

[0019] Figure 2 A schematic diagram of the calculation method for subgrade analysis considering localized deterioration. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The technical solutions provided by various embodiments of this invention will be described in detail below with reference to the accompanying drawings.

[0021] This invention provides a method for analyzing and calculating roadbeds that consider localized deterioration in permafrost, comprising the following steps:

[0022] S1: Determine the size of the road subsidence area. Determine the diameter D and height H of the subsidence area according to the target guidance to obtain the target subsidence. The diameter D and height H of the subsidence area are determined statistically based on the road distress situation in the frozen soil area.

[0023] S2: Assuming the location, size, and degree of deterioration of the affected area, a calculation model is established, and numerical analysis is performed using the finite element method or discrete element method to obtain the post-construction pavement settlement. The deteriorated area is located directly below or to the side of the settlement zone, and multiple sets of assumed parameters for the deteriorated area, including the diameter d, are used. i Deterioration area height b i The deteriorated area is h away from the road surface i The distance L from the center of the deteriorated area to the center of the subsidence iA finite element or discrete element model was established, and the elastic modulus, internal friction angle, and cohesion parameters of the soil within the localized deterioration zone were set to minimum values ​​to simulate the rapid deterioration of the soil caused by water migration. The settlement range parameter D was obtained through trial calculation. i H i ;

[0024] S3: Compare the difference between the simulated and predicted post-construction pavement settlement and the target settlement, randomly change or intentionally change the location, size and degree of deterioration of the deteriorated area according to the pattern, and repeatedly calculate to finally obtain multiple sets of foundation deterioration location, size and degree of deterioration that almost match the target settlement.

[0025] Based on the principle of considering both advantages and disadvantages for the subsidence area, the location, size, and degree of deterioration of the area are randomly or systematically and purposefully altered. The maximum and minimum values ​​of each parameter are calculated to obtain the feasible region for the deterioration area parameters. The initial parameters are repeatedly modified for trial calculations. The subsidence area parameters D calculated using the assumed deterioration area are then compared. i H i Given the target subsidence area parameters D and H, select 3 or more sets of assumed subsidence area parameters di, bi, hi, Li (i∈(3,n)) that meet the error range;

[0026] S4: Assuming the foundation deterioration meets the above-mentioned location, size, and degree of deterioration, simulate the construction process. Combined with the given roadbed scheme, consider load combinations such as vehicle loads, and verify the stress and deformation of the roadbed structure under multi-condition nonlinear load combinations. When three sets of deterioration are taken, the most unfavorable value is taken as the reference value; when more than three sets of values ​​are taken, the average value is taken as the reference value for design or evaluation.

[0027] Example 1:

[0028] A method for analyzing and calculating subgrades considering localized deterioration in permafrost subgrades is proposed. It assumes the deteriorated area is located directly below the settlement area and uses a randomly changing method to determine the parameters of the deteriorated area. The flowchart is shown below. Figure 2 As shown:

[0029] S1: Determine the dimensions of the road subsidence area. Based on the target orientation, determine the diameters D and H of the subsidence area to obtain the target subsidence. D and H can be determined statistically based on the road damage conditions in permafrost regions. Figure 1 As shown;

[0030] S2: Assuming the deteriorated area is located directly below the subsidence zone, multiple sets of assumed deteriorated area parameters are used, including diameter d. i Deterioration area height b i The deteriorated area is h away from the road surface iA calculation model was established, and the parameters of soil elastic modulus, internal friction angle, and cohesion within the localized deterioration zone were set to their minimum values. The settlement range parameter D was obtained through trial calculations. i H i ;

[0031] S3: Compare the post-construction pavement settlement predicted by simulation with the target settlement. The selection of random parameters for the deterioration area can be done by first calculating the maximum and minimum values ​​of each parameter according to the principles of what is beneficial or detrimental to the settlement area, thus obtaining the feasible region for the deterioration area parameters. Within this feasible region, two of the three deterioration area parameters can be randomly selected initially, and the third parameter can be calculated iteratively to gradually bring the settlement area closer to the target settlement. For example, selecting parameter d... i and b i Within the feasible region of the deterioration zone, h i The maximum value is h0, and the minimum value is h1. The corresponding settlement range parameters are D0, H0, D1, and H1, respectively. If the errors of D0, H0, D1, and H1 do not meet the requirements, then let... D is obtained using the finite element method or discrete element method. j H j If D j H j If the error does not meet the requirements, then Iterative calculations are performed until the subsidence zone parameters meet the requirements; trial calculations are conducted by repeatedly modifying the initial parameters, and the subsidence zone parameters D obtained from the calculations are compared with those obtained from the assumed deteriorated zone. i H i Given the target subsidence area parameters D and H, select 3 or more sets of assumed subsidence area parameters di, bi, hi, Li (i∈(3,n)) that meet the error range.

[0032] S4: Assuming the foundation deterioration meets the above-mentioned location, size, and degree of deterioration, simulate the construction process. Combined with the given roadbed scheme, consider load combinations such as vehicle loads, and verify the stress and deformation of the roadbed structure under multi-condition nonlinear load combinations. When three sets of deterioration are taken, the most unfavorable value is taken as the reference value; when more than three sets of values ​​are taken, the average value is taken as the reference value for design or evaluation.

[0033] Example 2:

[0034] A method for analyzing and calculating subgrades considering localized deterioration in permafrost subgrades is proposed. This method assumes the deteriorated area is located to the side of a settlement area and uses a targeted adjustment method to determine the parameters of the deteriorated area. The flowchart is shown below. Figure 2 As shown:

[0035] S1: Determine the dimensions of the road subsidence area. Based on the target orientation, determine the diameters D and H of the subsidence area to obtain the target subsidence. D and H can be determined statistically based on the road damage conditions in permafrost regions. Figure 1 As shown;

[0036] S2: Assuming the deteriorated area is located to the side of the subsidence zone, multiple sets of assumed deteriorated area parameters are used, including diameter d. i Deterioration area height b i The deteriorated area is h away from the road surface i The distance L from the center of the deteriorated area to the center of the subsidence i A finite element or discrete element model is established, and the soil elastic modulus, internal friction angle, and cohesion parameters within the localized deterioration zone are set to their minimum values. The settlement range parameter D is then calculated. i H i ;

[0037] S3: Calculate d through trial and error i b i h i L i With D i H i A multivariate logistic regression analysis was performed on the relationship between the subsidence area and the target subsidence area. The parameters of the deteriorated region, which had a significant impact on the subsidence range, were prioritized for adjustment. Trial calculations of the subsidence range were conducted until the subsidence area closely approximated the target subsidence area. The initial parameters with smaller impacts were repeatedly modified and trial calculations were performed. The subsidence area parameter D calculated from the assumed deteriorated region was then compared with the parameter D obtained from the subsidence area calculation. i H i With the target subsidence area parameters D and H, we can obtain 3 or more sets of assumed subsidence area parameters di, bi, hi, Li (i∈(3,n)) that satisfy the error range.

[0038] S4: Assuming the foundation deterioration meets the above-mentioned location, size, and degree of deterioration, simulate the construction process. Combined with the given roadbed scheme, consider load combinations such as vehicle loads, and verify the stress and deformation of the roadbed structure under multi-condition nonlinear load combinations. When three sets of deterioration are taken, the most unfavorable value is taken as the reference value; when more than three sets of values ​​are taken, the average value is taken as the reference value for design or evaluation.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for analyzing and calculating roadbeds considering localized deterioration in permafrost, characterized in that, The steps are as follows: S1: Determine the size of the road subsidence area, and determine the diameter D and height H of the subsidence area according to the target guidance to obtain the target subsidence; S2: Assuming the location, size, and degree of deterioration of the deteriorated area, establish a calculation model and conduct numerical analysis using finite element or discrete element methods to obtain the post-construction road surface settlement. S3: Compare the difference between the simulated and predicted post-construction pavement settlement and the target settlement, randomly change or intentionally change the location, size and degree of deterioration of the deteriorated area according to the pattern, and repeatedly calculate to finally obtain multiple sets of foundation deterioration location, size and degree of deterioration that almost match the target settlement. S4: Assuming the foundation deterioration meets the above-mentioned location, size, and degree of deterioration, simulate the construction process. Combined with the given roadbed scheme, consider load combinations such as vehicle loads, and verify the stress and deformation of the roadbed structure under multi-condition nonlinear load combinations. When three sets of deterioration are taken, the most unfavorable value is taken as the reference value; when more than three sets of values ​​are taken, the average value is taken as the reference value for design or evaluation. The specific method of step S3 is as follows: Based on the principle of what is beneficial or detrimental to the subsidence area, the location, size, and degree of deterioration of the deteriorated area are randomly or systematically and purposefully changed. The maximum and minimum values ​​of each parameter are calculated to obtain the feasible region of the deteriorated area parameters. The initial parameters are repeatedly modified for trial calculations. The subsidence area parameters D calculated by comparing them with those of the assumed deteriorated area are then compared. i H i Given the target subsidence area parameters D and H, select 3 or more sets of assumed subsidence area parameters di, bi, hi, Li (i∈(3,n)) that meet the error range.

2. The subgrade analysis and calculation method considering local deterioration of permafrost subgrade according to claim 1, characterized in that, The specific method of step S2 is as follows: the deteriorated area is located directly below or to the side of the subsidence area, and multiple sets of assumed deteriorated area parameters are used, including the diameter d. i Deterioration area height b i The deteriorated area is h away from the road surface i The distance L from the center of the deteriorated area to the center of the subsidence i A finite element or discrete element model was established, and the elastic modulus, internal friction angle, and cohesion parameters of the soil within the localized deterioration zone were set to minimum values ​​to simulate the rapid deterioration of the soil caused by water migration. The settlement range parameter D was obtained through trial calculation. i H i .

3. The subgrade analysis and calculation method considering local deterioration of permafrost subgrade according to claim 2, characterized in that, The diameter D and height H of the subsidence area in step S1) are determined statistically based on the road damage situation in the permafrost region.

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