Coarse-grained sulfate saline soil roadbed filling control standard calculation method

Abstract

The invention discloses a coarse-grained sulfate salinized soil roadbed filling control standard calculation method. The method comprises the following steps: S1, performing a salt expansion deformation orthogonal test to obtain a coarse-grained sulfate salinized soil salt expansion deformation estimation equation containing the working condition in an experimental scene; s2, performing single-factor effect analysis on the working conditions to obtain the influence of salt expansion deformation of each parameter in the working conditions, and determining main influence parameters influencing the salt expansion deformation; s3, determining a working condition boundary value of each layer of the roadbed; and S4, converting the maximum salt expansion deformation value of each layer of the roadbed into a salt expansion deformation value in an experimental scene, substituting the salt expansion deformation value into the salt expansion deformation estimation equation of the coarse-grained sulfate salinized soil according to different working conditions, and determining a control index of each layer of the roadbed filler made of the coarse-grained sulfate salinized soil. According to the salinized soil type and the proposed road structure of different engineering construction areas, the selection condition of the roadbed material is optimized, the resource utilization rate is increased, and the engineering construction cost is saved.

Description

Technical Field

[0001] The invention belongs to the technical field of road construction, and in particular relates to a method for calculating control standards for coarse-grained sulfate saline soil roadbed filling. Background Art

[0002] Coarse sulfate saline soil has salt swelling performance. When the external environmental conditions change, the soluble salt in the soil body undergoes phase change, causing the soil body to swell and shrink, and the strength to decrease, which in turn causes roadbed arching, road surface cracking and other diseases, affecting the safety of engineering construction and the durability of the road. Therefore, controlling the salt swelling performance of coarse sulfate saline soil used as roadbed filling material is a key measure to ensure the durability of the road.

[0003] In order to avoid or reduce the harm caused by the salt swelling of coarse-grained sulfate saline soil, the saline soil is usually replaced with salt-free roadbed filling materials based on the degree of salinization during the construction of road projects in saline soil areas. However, due to the different types of saline soils and the weight of the asphalt pavement itself, salt swelling is inhibited. At present, there is no reliable method to determine how to effectively construct saline soil. Judging the degree of harm of coarse-grained sulfate saline soil only by salt content will cause a large amount of potential roadbed filling material to be wasted. In addition, the vast and sparsely populated environment in the northwest region also leads to high replacement and transportation costs, and construction quality problems may also occur. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a method for calculating the control standard of coarse-grained sulfate saline soil roadbed filling. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0005] A method for calculating control standards for coarse-grained sulfate saline soil roadbed filling, including:

[0006] S1. Based on preset working conditions, an orthogonal test of salt expansion deformation is conducted on coarse-grained sulfate saline soil with different particle sizes in an experimental scenario to obtain a salt expansion deformation prediction equation of coarse-grained sulfate saline soil containing the working conditions in the experimental scenario, wherein the working conditions include salt content, water content, fine-grained soil content and overlying load;

[0007] S2. Performing a single factor effect analysis on the working conditions to obtain the influence of each parameter in the working conditions on the salt expansion deformation, and determining the main influencing parameters affecting the salt expansion deformation, so as to use the main influencing parameters as the control index for the coarse-grained sulfate saline soil roadbed filling;

[0008] S3. Determine the salt expansion depth of the roadbed and the pavement damage value in the actual scenario, select different asphalt pavement combinations and overlying load sizes, and then determine the working condition boundary value of each layer of the roadbed;

[0009] S4. The maximum salt expansion deformation value of each layer of the roadbed is converted into the salt expansion deformation value under the experimental scenario, and the salt expansion deformation prediction equation of the coarse-grained sulfate saline soil is introduced according to different working conditions to determine the control index of each layer of the coarse-grained sulfate saline soil as roadbed filling.

[0010] In a specific embodiment, the S1 step comprises:

[0011] S11. Establish a multiple regression equation related to salt expansion deformation value based on salt content, water content, fine-grained soil content and overlying load;

[0012] S12, establishing a test factor level coding table for orthogonal test, and based on the test factor level coding table, conducting salt expansion deformation orthogonal test in experimental scenario to obtain salt expansion deformation under different working conditions to establish a centralized orthogonal combination design coding table;

[0013] S13, fitting the multiple regression equation according to the orthogonal combination design coding table to obtain an initial coarse-grained sulfate saline soil salt expansion deformation prediction equation;

[0014] S14. Perform a significance test on the correlation coefficient of each factor in the initial coarse-grained sulfate saline soil salt expansion deformation estimation equation, and delete the corresponding factors whose significance level in the correlation coefficient is less than the preset significance value from the initial coarse-grained sulfate saline soil salt expansion deformation estimation equation to obtain the coarse-grained sulfate saline soil salt expansion deformation estimation equation.

[0015] In a specific implementation, the preset significance value is 0.05.

[0016] In a specific embodiment, the salt expansion deformation prediction equation of the coarse-grained sulfate saline soil is expressed as:

[0017] Y=-0.768-1.019X1+0.362X1 2 +0.053X1X2+0.002X1X3-0.068X1X4,

[0018] Among them, X1 is the salt content; X1 2 is the quadratic term of salt content; X1X2 is the interaction term between salt content and water content; X1X3 is the interaction term between salt content and fine-grained soil content; X1X4 is the interaction term between salt content and overlying load.

[0019] In a specific embodiment, the influence of the salt expansion deformation includes negative influence and positive influence, the influence magnitude is determined according to the initial influence degree and influence trend, and the parameter with the greatest influence is taken as the main influence parameter.

[0020] In a specific embodiment, the roadbed is divided into a first depth, a second depth, and a third depth according to the combination of salt expansion depth and pavement structure, and the corresponding first deformation parameter, second deformation parameter, and third deformation parameter are selected based on the pavement damage value;

[0021] According to the fine-grained soil content in the coarse-grained sulfate saline soil, it is divided into the first type of sand, the second type of sand, and the third type of sand; according to the roadbed humidity, it is divided into the first humidity, the second humidity, and the third humidity; and the first upper load overlay load, the second upper load overlay load, and the third upper load overlay load are selected to determine the working condition boundary value of each layer of the roadbed.

[0022] Beneficial effects of the present invention:

[0023] The method for calculating the control standard of coarse-grained sulfate saline soil roadbed filling of the present invention is based on the salt swelling test results of multiple factors such as salt content, water content, fine particle content and overlying load, constructs a salt swelling deformation prediction equation of coarse-grained sulfate saline soil, adopts single factor effect analysis to obtain the main influencing factors affecting the salt swelling deformation, selects the control index of coarse-grained sulfate saline soil roadbed filling, and then determines the salt swelling depth of the roadbed and the road surface damage value, selects different asphalt pavement combinations to calculate the overlying load size, and then determines the working condition boundary value of different layers of the roadbed, and brings the salt swelling deformation simplified prediction equation into the different working conditions to determine the control index of different layers of coarse-grained sulfate saline soil as roadbed filling material; compared with the traditional coarse-grained sulfate saline soil filling method, the method optimizes the selection conditions of the coarse-grained sulfate saline soil as roadbed filling material, combines the saline soil type and the road structure, determines the control standard of coarse-grained sulfate saline soil as roadbed filling material at different layers under various conditions, can meet the construction needs of different saline soil areas, improve the utilization rate of saline soil, reduce the cost of engineering construction, improve the construction quality, and has good social and economic benefits.

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of a method for calculating control standards for coarse-grained sulfate saline soil roadbed filling provided by an embodiment of the present invention;

[0026] Figure 2 is a comparison chart of predicted values ​​and measured values ​​of salt expansion deformation of coarse-grained sulfate saline soil provided by an embodiment of the present invention;

[0027] Figure 3 is a single factor effect influence curve diagram provided by an embodiment of the present invention;

[0028] Figure 4 It is a measured geothermal curve in a specific example provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0030] Embodiment 1

[0031] See also Figure 1 , Figure 1 The present invention provides a flow chart of a method for calculating a control standard for a coarse-grained sulfate saline soil roadbed, including:

[0032] S1. Based on preset working conditions, an orthogonal test of salt expansion deformation is conducted on coarse-grained sulfate saline soil with different particle sizes in an experimental scenario to obtain a salt expansion deformation prediction equation of coarse-grained sulfate saline soil containing the working conditions in the experimental scenario, wherein the working conditions include salt content, water content, fine-grained soil content and overlying load;

[0033] Specifically, the S1 step includes:

[0034] S11. Establish a multiple regression equation related to salt expansion deformation value based on salt content, water content, fine-grained soil content and overlying load;

[0035] This embodiment is described with a specific example.

[0036] First, the basic physical parameters of the sample were determined through screening tests, compaction tests, etc., as shown in Table 1.

[0037] Table 1 Screening test results

[0038]

[0039] Table 2 Basic physical properties

[0040]

[0041] Secondly, the relationship between the four influencing factors of salt content (X1), water content (X2), fine-grained soil content (X3), and overburden load (X4) and the salt expansion deformation value (Y) is selected to establish the general form of the multivariate regression equation as follows:

[0042] b0, b j 、b jj 、b ij is the corresponding coefficient.

[0043] S12, establishing a test factor level coding table for orthogonal test, and based on the test factor level coding table, conducting salt expansion deformation orthogonal test in experimental scenario to obtain salt expansion deformation under different working conditions to establish a centralized orthogonal combination design coding table;

[0044] In one example, for example, the salt content is at two levels of 3.0% and 1.5%, the moisture content is at two levels of 6% and 4%, the fine particle content is at two levels of 30% and 15%, and the overburden load is at two levels of 2.76 kPa and 1.38 kPa.

[0045] The zero level and the variation interval are calculated based on the upper and lower levels of each factor. The calculation formulas are as follows:

[0046] Among them, Z 0j is the zero level of the jth factor; Z 1j is the jth factor 1 level (upper level); Z 2j is the j-th factor -1 level (lower level); Δ j is the variation interval of the jth factor; γ is the star arm, the distance between the star point and the center point, which is related to the number of factors and the number of trials of the center point.

[0047] In this embodiment, γ=1.414 is selected, and the experimental factor level coding table can be obtained, as shown in Table 3.

[0048] Table 3 Experimental factor level coding table

[0049]

[0050] According to the experimental factor level coding table in Table 3, the specific values ​​of each group of experimental factors are clarified, and then the orthogonal test of salt expansion deformation under the experimental scenario is carried out to measure the salt expansion deformation under different working conditions, so as to obtain the orthogonal combination design coding table after centralization, as shown in Table 4.

[0051] Table 4 Orthogonal combination design coding table

[0052]

[0053]

[0054] S13, fitting the multiple regression equation according to the orthogonal combination design coding table to obtain an initial coarse-grained sulfate saline soil salt expansion deformation prediction equation;

[0055] Taking the above example as an example, the final fitting equation for estimating the initial salt expansion deformation of coarse-grained sulfate saline soil is:

[0056] Y=-0.901+0.111X1+0.205X2-0.032X4+0.300X1 2 -0.032X2 2 -0.001X3 2

[0057] +0.028X4 2+0.022X1X2-0.015X1X3-0.232X1X4+0.008X2X3+0.013X3X4,

[0058] Regression analysis of the above equation shows that the correlation coefficient R = 0.989549, the determination coefficient RR = 0.9792, the F value = 10.0911, the p value = 0.0408, and the significance level P < 0.05, indicating that the model is good and the factor analysis of the model is effective.

[0059] S14. Perform a significance test on the correlation coefficient of each factor in the initial coarse-grained sulfate saline soil salt expansion deformation estimation equation, and delete the corresponding factors whose significance level in the correlation coefficient is less than the preset significance value from the initial coarse-grained sulfate saline soil salt expansion deformation estimation equation to obtain the coarse-grained sulfate saline soil salt expansion deformation estimation equation.

[0060] Based on the above equation, the significance test of the correlation coefficient of each factor in the estimation equation is shown in Table 5.

[0061] Table 5 Factor significance test table

[0062]

[0063] Taking the significance level α = 0.05, the items with significance level α≤0.05 in the correlation coefficient have a significant impact on the equation, the items with α≤0.01 have a very significant impact on the equation, and the items with α>0.05 have no significant impact on the equation. Based on this, the insignificant factors in the estimation equation are eliminated, the equation parameters are recalculated, and the simplified estimation equation for salt expansion deformation of coarse-grained sulfate saline soil is obtained as follows:

[0064] Y=-0.768-1.019X1+0.362X1 2 +0.053X1X2+0.002X1X3-0.068X1X4 (4)

[0065] Where: X1 is the salt content; X1 2 is the quadratic term of salt content; X1X2 is the interaction term between salt content and water content; X1X3 is the interaction term between salt content and fine-grained soil content; X1X4 is the interaction term between salt content and overlying load.

[0066] Regression analysis of the above equation shows that the regression square sum is 20.419, the residual is 0.337, and R2 = 0.953, indicating that the equation is effective and the fitting effect is good. In addition, the equation is used to calculate the comparison between the salt expansion deformation value and the measured deformation value under various working conditions. Figure 2 As shown, the square lines in the figure are observed values, and the circular lines are fitted values ​​of this embodiment. It can be seen that the fitted values ​​are basically consistent with the measured values, and the error is small.

[0067] S2. Performing a single factor effect analysis on the working conditions to obtain the influence of each parameter in the working conditions on the salt expansion deformation, and determining the main influencing parameters affecting the salt expansion deformation, so as to use the main influencing parameters as the control index for the coarse-grained sulfate saline soil roadbed filling;

[0068] When performing single factor effect analysis, it is necessary to calculate the single factor utility results when other factors in the formula are at zero level, and normalize each single factor. Finally, it can be displayed in a table or other form to determine the impact size. This embodiment is illustrated in the form of a curve, such as Figure 3 In the figure, the salt expansion deformation on one side of the curve close to the origin of the coordinate system is respectively the overburden load, fine particle content, water content, and salt content, while the other end is just the opposite. It can be seen that the effect of salt content on salt expansion deformation is a quadratic parabola effect. The greater the salt content, the more significant the effect on salt expansion deformation; water content and fine particle content are linear influencing factors, and the increase of water content and fine particle content promotes salt expansion deformation; overburden load is a negative linear influencing factor, and the increase of overburden load can inhibit salt expansion deformation.

[0069] From the perspective of the degree of influence, it is intuitive to see that salt content (X1)>water content (X2)>overburden load (X4)>fine particle content (X3), and it is concluded that salt content is the main influencing factor affecting salt expansion deformation. If it is displayed in other ways, it can be determined based on the initial influence degree and influence trend of the specific value, and the factor with positive influence and large growth value can be selected as the main influencing factor.

[0070] S3. Determine the salt expansion depth of the roadbed and the pavement damage value in the actual scenario, select different asphalt pavement combinations and overlying load sizes, and then determine the working condition boundary value of each layer of the roadbed;

[0071] Specifically, the roadbed is divided into a first depth, a second depth, and a third depth according to the salt expansion depth and the pavement structure combination, and the corresponding first deformation parameter, second deformation parameter, and third deformation parameter are selected based on the pavement damage value;

[0072] According to the fine-grained soil content in the coarse-grained sulfate saline soil, it is divided into the first type of sand, the second type of sand, and the third type of sand; according to the roadbed humidity, it is divided into the first humidity, the second humidity, and the third humidity; and the first upper load overlay load, the second upper load overlay load, and the third upper load overlay load are selected to determine the working condition boundary value of each layer of the roadbed.

[0073] The following is an example of the geothermal curve measured on site on a road section where an actual project is located.

[0074] like Figure 4As shown in the figure, the lowest average temperature for roadbed depth of 1.5m is greater than 0℃, and the salt swelling depth is usually 1.5m. Therefore, the salt swelling depth of Class II and below highways is considered to be in the range of 1.5m to 1.6m, and that of expressways and Class I highways is considered to be 2.0m.

[0075] According to existing technical specifications and standards, regarding the deformation requirements and threshold values ​​of roads, taking into account various defects, 25 mm·m is taken. -2 It is the comprehensive value of road surface damage.

[0076] The combination design of the pavement structure should be based on the traffic level of the road and natural factors such as meteorology and hydrology, and reasonably select and arrange the various levels of the pavement structure. Common asphalt pavement structure combinations are shown in Table 6, and the base and subbase combinations of expressways and first-class highways are shown in Table 7 and the combination code description is shown in Table 8.

[0077] Table 6 Recommended asphalt pavement structure

[0078]

[0079] Table 7 Combinations of base and subbase for expressways and first-class highways

[0080]

[0081] Table 8 Combination code description and schematic

[0082]

[0083] According to the asphalt surface layer structure and the combination of base and subbase, the weight of the asphalt pavement under different combinations is calculated and used as the overlying load. The calculation results are shown in Table 9.

[0084] Table 9 Asphalt pavement weight

[0085]

[0086] According to the salt expansion depth and typical pavement structure combination, the roadbed is divided into three filling depths: 0-1.2m, 1.2-1.9m, and 1.9-2.5m. -2The pavement damage values ​​are assigned to different layers, with the controlled deformation of 0-1.2m being 6mm, 1.2-1.9m being 7mm, and 1.9-2.5m being 12mm. Coarse-grained sulfate saline soil is divided into three types according to the fine-grained soil content: sand (F≤5%), sand containing fine-grained soil (5%<F≤15%), and fine-grained soil sand (15%<F≤50%). The roadbed humidity is divided into three types: 2%~4%, 4%~6%, and 6%~8%. In combination with different asphalt pavement combinations, three different overburden loads of 10kPa, 15kPa, and 20kPa are selected on the principle of partial safety to replace the typical pavement structure. This is used as the demarcation value for different working conditions to calculate the control standard for coarse-grained sulfate saline soil filling.

[0087] S4. The maximum salt expansion deformation value of each layer of the roadbed is converted into the salt expansion deformation value under the experimental scenario, and the salt expansion deformation prediction equation of the coarse-grained sulfate saline soil is introduced according to different working conditions to determine the control index of each layer of the coarse-grained sulfate saline soil as roadbed filling.

[0088] The maximum salt expansion deformation is required to be 6mm in the range of 0-1.2m, 7mm in the range of 1.2m-1.9m, and 12mm in the range of 1.9m-2.5m. The maximum salt expansion deformation value of each layer is converted into the salt expansion deformation corresponding to the indoor test height, and according to different working conditions, it is substituted into formula (4) to calculate the salt content control index of different layers of coarse-grained sulfate saline soil used as roadbed filler.

[0089]

[0090]

[0091] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0092] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0093] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in a claim. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0094] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for calculating control standards for coarse-grained sulfate saline soil roadbed filling, characterized in that: include: S1. Based on preset working conditions, an orthogonal test of salt expansion deformation is conducted on coarse-grained sulfate saline soil with different particle sizes in an experimental scenario to obtain a salt expansion deformation prediction equation of coarse-grained sulfate saline soil containing the working conditions in the experimental scenario, wherein the working conditions include salt content, water content, fine-grained soil content and overlying load; S2. Performing a single factor effect analysis on the working conditions to obtain the influence of each parameter in the working conditions on the salt expansion deformation, and determining the main influencing parameters affecting the salt expansion deformation, so as to use the main influencing parameters as the control index for the coarse-grained sulfate saline soil roadbed filling; S3. Determine the salt expansion depth of the roadbed and the pavement damage value in the actual scenario, select different asphalt pavement combinations and overlying load sizes, and then determine the working condition boundary value of each layer of the roadbed; S4. The maximum salt expansion deformation value of each layer of the roadbed is converted into the salt expansion deformation value under the experimental scenario, and the salt expansion deformation prediction equation of the coarse-grained sulfate saline soil is introduced according to different working conditions to determine the control index of each layer of the coarse-grained sulfate saline soil as roadbed filling.

2. The method for calculating control standards for coarse-grained sulfate saline soil roadbed filling according to claim 1 is characterized in that: The S1 step includes: S11. Establish a multiple regression equation related to salt expansion deformation value based on salt content, water content, fine-grained soil content and overlying load; S12, establishing a test factor level coding table for orthogonal test, and based on the test factor level coding table, conducting salt expansion deformation orthogonal test in experimental scenario to obtain salt expansion deformation under different working conditions to establish a centralized orthogonal combination design coding table; S13, fitting the multiple regression equation according to the orthogonal combination design coding table to obtain an initial coarse-grained sulfate saline soil salt expansion deformation prediction equation; S14. Perform a significance test on the correlation coefficient of each factor in the initial coarse-grained sulfate saline soil salt expansion deformation estimation equation, and delete the corresponding factors whose significance level in the correlation coefficient is less than the preset significance value from the initial coarse-grained sulfate saline soil salt expansion deformation estimation equation to obtain the coarse-grained sulfate saline soil salt expansion deformation estimation equation.

3. The method for calculating control standards for coarse-grained sulfate saline soil roadbed filling according to claim 2 is characterized in that: The preset significance value is 0.

05.

4. The method for calculating control standards for coarse-grained sulfate saline soil roadbed filling according to claim 1 is characterized in that: The salt expansion deformation prediction equation of coarse-grained sulfate saline soil is expressed as: Y=-0.768-1.019X1+0.362X1 2 +0.053X1X2+0.002X1X3-0.068X1X4, Among them, X1 is the salt content; X1 2 is the quadratic term of salt content; X1X2 is the interaction term between salt content and water content; X1X3 is the interaction term between salt content and fine-grained soil content; X1X4 is the interaction term between salt content and overlying load.

5. The method for calculating control standards for coarse-grained sulfate saline soil roadbed filling according to claim 1 is characterized in that: The influence of the salt expansion deformation includes negative influence and positive influence. The influence magnitude is determined according to the initial influence degree and influence trend, and the parameter with the greatest influence is taken as the main influence parameter.

6. The method for calculating control standards for coarse-grained sulfate saline soil roadbed filling according to claim 1 is characterized in that: Dividing the roadbed into a first depth, a second depth and a third depth according to the salt expansion depth and the pavement structure combination, and selecting corresponding first deformation parameters, second deformation parameters and third deformation parameters based on the pavement damage value; According to the fine-grained soil content in the coarse-grained sulfate saline soil, it is divided into the first type of sand, the second type of sand, and the third type of sand; according to the roadbed humidity, it is divided into the first humidity, the second humidity, and the third humidity; and the first upper load overlay load, the second upper load overlay load, and the third upper load overlay load are selected to determine the working condition boundary value of each layer of the roadbed.

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