Cement stabilized macadam base construction quality evaluation standard method based on deflection value

Abstract

The invention relates to a deflection value-based cement stabilized macadam base construction quality evaluation standard method. The method comprises the following steps of: 1, analyzing influence factors of cement stabilized macadam base construction quality evaluation indexes; 2, calculating the compressive resilience modulus of each base layer through the equivalent age-compressive resilience modulus estimation model of the cement stabilized macadam; 3, calculating the conditions of a single-layer base layer and a double-layer base layer by utilizing pavement mechanics software, and calculating the compressive resilience modulus of each base layer when the conditions of the single-layer base layer and the double-layer base layer are calculated; the top deflection value of the base layer under the coupling of factors such as the cement dosage, the base layer temperature, the curing age, the base layer thickness and the soil matrix rebound modulus; 4, establishing a deflection value-based cement stabilized macadam base construction quality evaluation standard prediction model; and 5, determining a deflection value-based cement stabilized macadam base construction quality evaluation standard value domain. According to the method, the quality evaluation standard value domain of the cement stabilized macadam base can be calculated, and the construction quality of the cement stabilized macadam base is evaluated by comparing and analyzing the relation between the actually measured deflection value and the evaluation standard value domain.

Description

Technical Field

[0001] The present invention relates to a method for evaluating the construction quality of a cement stabilized macadam base based on deflection values, belonging to the technical field of construction engineering. Background Art

[0002] Since the material properties of cement stabilized macadam are closely related to the deflection value of the top surface of the cement stabilized macadam base, in the current method for determining the construction quality evaluation standard of the cement stabilized macadam base, deflection value detection has become a common standard for evaluating the construction quality of the cement stabilized macadam base due to its convenience and intuitiveness. The curing temperature and curing age are related to the material properties of cement stabilized macadam, and the material properties of water stable macadam, the resilient modulus of the subgrade, and the base thickness jointly affect the deflection value of the top surface of the base. However, the current construction quality evaluation standard for the cement stabilized macadam base does not consider the influence of external environmental factors such as temperature conditions and curing age changes on the deflection value, resulting in difficulty in timely, accurately, and reasonably evaluating the quality of the cement stabilized macadam base during construction.

[0003] Specifically, the following problems exist: (1) The standard deflection value of the top of the water stable macadam base does not consider the change in curing temperature conditions. The standard deflection value is usually obtained under specific experimental conditions. Failure to effectively combine the curing temperature in the actual construction environment will result in unreasonable calculation of the standard deflection value.

[0004] (2) There are limitations in conducting deflection value inspection at the design age. Since the material modulus increases with age, when laying in layers, it is necessary to timely inspect the quality of the next layer. However, since the next layer usually has not reached the design age, inspecting according to the design deflection value may result in a qualified project being judged as unqualified, and waiting for the design age will cause delays in the project progress, resulting in a conflict between the construction progress and the quality evaluation.

[0005] (3) The standard deflection value considering different cement dosages is lacking. A high cement dosage can make the cement stabilized macadam base exhibit high strength. In actual applications, the deflection value is often reduced by increasing the cement dosage, resulting in the deflection value possibly meeting the standard when the strength does not meet the design requirements, thus masking potential quality problems.

[0006] In view of this, it is urgent to study a method for evaluating the construction quality of a cement stabilized macadam base based on deflection values. The construction quality evaluation standard determined by this method can not only effectively evaluate and control the construction quality but also conform to the engineering reality. Summary of the Invention

[0007] In order to overcome the shortcomings of existing research, the present invention provides a cement-stabilized gravel base construction quality evaluation standard method based on deflection value, in order to simultaneously consider the influence of factors such as cement dosage, base temperature, curing age, base thickness, soil base rebound modulus on the deflection value of the top surface of the cement-stabilized gravel base, thereby solving the problem of unreasonable quality evaluation standards for water-stabilized gravel base construction.

[0008] The standard method for evaluating the construction quality of cement-stabilized crushed stone base based on deflection value includes the following steps: Step 1: Analyze the influencing factors of the construction quality evaluation index of cement stabilized gravel base, select cement dosage x, base temperature T, curing age t, base thickness H, soil base rebound modulus E 0 is the independent variable; Step 2: Calculate the compressive resilience modulus of each base layer in single-layer and double-layer situations through the cement-stabilized crushed stone equivalent age-compressive resilience modulus estimation model , , : Step 3: Use pavement mechanics software to calculate the top deflection value of the base layer under the coupling of cement dosage, base layer temperature, curing age, base layer thickness and soil base rebound modulus in single-layer and double-layer base layers; Step 4: Establish a prediction model for the construction quality evaluation standard of cement-stabilized crushed stone base based on deflection value; Step 5: Determine the standard value range for the construction quality assessment of cement-stabilized crushed stone base based on deflection value.

[0009] The cement stabilized crushed stone equivalent age-compressive resilience modulus estimation model in step 2 uses the formula Nonlinear fitting was performed to predict the compressive rebound modulus at different cement dosages through equivalent age; Where E represents the compressive rebound modulus, Represents equivalent age, A and B are parameters and dimensionless.

[0010] The equivalent age refers to the age of each base layer at different temperatures being equivalent to the age of curing at standard temperature, including the equivalent age of a single-layer base layer and the equivalent age of a double-layer base layer.

[0011] The equivalent age of the single-layer base The calculation method is as follows:

[0012] In the formula, Indicated in Temperature health Day relative to standard temperature The equivalent age of the next regimen, d; =1 represents 10℃, = 2 represents 30 °C; = 1, 2, 3, 4 represent the curing ages of 3d, 7d, 14d, and 28d; The standard temperature is usually taken as 20 °C; represents the curing temperature in °C; is the gas constant, with a value of 8.3144 ; Ea is the activation energy, in J / mol.

[0013] The equivalent age of the double-layer base includes the equivalent age of the lower base and the equivalent age of the upper base in the double-layer base. The calculation formula for the equivalent age of the lower base is as follows:

[0014] In the formula represents the equivalent age of the lower base in the case of a double-layer base, represents the equivalent age of the upper base in the case of a double-layer base cured at temperature for days relative to the equivalent age cured at the standard temperature.

[0015] Step 4 specifically includes: Regarding the prediction of the standard deflection value range as a multi-classification problem, establish multiple logistic regression prediction models for the construction quality evaluation standards of single-layer and double-layer cement stabilized macadam bases respectively, and assign grading values to the single-layer and double-layer deflection distribution intervals; The functional form of the multiple logistic regression model is as follows:

[0016] In the formula is the constant term, is the independent variable, is the regression coefficient.

[0017] In step 5, the multiple logistic regression prediction models for the construction quality evaluation standards of single-layer and double-layer cement stabilized macadam bases can be directly used to calculate the standard value range of the evaluation criteria under the coupling of multiple factors during the construction of single-layer and double-layer bases.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention first calculates the deflection value at the top surface of the water-stabilized macadam base affected by factors such as cement dosage, base temperature, curing age, base thickness, and subgrade resilient modulus using pavement mechanics analysis software. Then, based on the multiple Logistic regression model, prediction models for the construction quality evaluation standards of water-stabilized macadam bases in single-layer and double-layer cases are constructed. Finally, the standard value range of the construction quality evaluation standards of the cement stabilized macadam base is calculated through the constructed regression model. This standard value range can be directly used for the quality evaluation of the cement stabilized macadam base during construction. The present invention comprehensively considers influencing factors such as cement dosage, base course temperature, curing age, base course thickness, and subgrade resilient modulus, and establishes a prediction model for the construction quality evaluation standard of cement stabilized macadam base course based on deflection values.

[0019] The present invention respectively establishes multiple logistic regression models for predicting the deflection value standards in the cases of single-layer base course and double-layer base course, which can more accurately predict the deflection standard value ranges under different structural forms, and independently evaluate the construction quality of a certain number of layers of cement stabilized macadam base course according to the prediction results of the models. Brief Description of the Drawings

[0020] Figure 1 It is a specific flow chart of the method for determining the construction quality evaluation standard of the cement stabilized macadam base course of the present invention. Detailed Embodiment

[0021] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] Next, taking an experiment on the growth law of the compressive resilient modulus of the base course under standard curing conditions and non-standard curing conditions as the basis, and taking the determination of the evaluation standard of the water stable macadam base course asphalt pavement in a certain area as an example, the present invention will be further elaborated. Refer to Figure 1 , a method for the construction quality evaluation standard of the cement stabilized macadam base course based on deflection values according to the present invention, the method specifically includes the following steps: Step 1: Analyze the influencing factors of the construction quality evaluation index of the cement stabilized macadam base course, and select cement dosage x, base course temperature T, curing age t, base course thickness H, and subgrade resilient modulus E 0 as independent variables; The independent variable cement dosage (x) selects three common types of 4%, 5%, and 6%; selects the common standard curing temperature of 20°C, 30°C higher than the standard curing temperature, and 10°C lower than the standard curing temperature as the value types of the independent variable base course temperature (T); the curing age (t) selects the common ages of 3d, 7d, 14d, and 28d in combination with the construction environment and the cement hydration rate; according to the general thickness value range of the water stable macadam base course asphalt pavement in the test area, select the thickness of one layer of the base course (H) as three common values of 16cm, 17cm, and 18cm, and the two-layer thickness includes 16 + 16cm, 17 + 17cm, and 18 + 18cm; the subgrade resilient modulus (E0) includes the value range from light traffic to heavy traffic, that is, three types of 40mpa, 50mpa, and 60mpa.

[0023] Step 2: Calculate the compressive resilient modulus of each base course in the single-layer and double-layer cases through the equivalent age-compressive resilient modulus prediction model of cement stabilized macadam , , : In this example, using the test results of the indoor compressive resilient modulus of cement stabilized macadam specimens, an equivalent age-compressive resilient modulus prediction formula for cement stabilized macadam is established. Among them, the parameter values of the regression equation of the compressive resilient modulus of water stable macadam with different cement dosages are shown in Table 1 below.

[0024]

[0025] In the formula, E represents the compressive resilient modulus, represents the equivalent age, and A and B are parameters, dimensionless.

[0026] Table 1 Parameter values of the regression equation of the compressive resilient modulus of water stable macadam with different cement dosages

[0027] In this example, the equivalent age refers to the age of each base course cured at different temperatures equivalent to the age cured at the standard temperature (20°C), including the equivalent age of the single-layer base course and the equivalent age of the double-layer base course. Among them, the calculation method of the equivalent age of the single-layer base course is as follows:[[]]

[0028] In the formula, represents the equivalent age, in days, of curing for days at temperature relative to curing at the standard temperature ; = 1 represents 10°C, = 2 represents 30°C; = 1, 2, 3, 4 represent the curing ages of 3d, 7d, 14d, 28d; is the standard temperature, usually taken as 20°C; represents the curing temperature, in °C; is the gas constant, with a value of 8.3144 ; Ea is the activation energy, in J / mol. The activation energy of cement stabilized macadam is determined through experiments to be Ea = 40 kJ / mol, and the results are shown in Table 2.

[0029] Table 2 Calculation table of the equivalent age of the single-layer base course

[0030] The equivalent age of the double-layer base course includes the equivalent age of the lower base course in the double-layer base course and the equivalent age of the upper base course in the double-layer base course. Among them, the calculation formula of the equivalent age of the lower base course is as follows:

[0031] In the formula represents the equivalent age of the lower base layer in the case of a double-layer base layer, represents the equivalent age of the upper base layer in the case of a double-layer base layer cured at a temperature for days relative to the equivalent age cured at the standard temperature (20°C). In this example, the equivalent age of the lower base layer and the equivalent age of the upper base layer The calculation results are shown in Table 3.

[0032] Table 3 Calculation Table of Equivalent Age of Double-Layer Base Layer

[0033] Using the equivalent age-compressive resilient modulus prediction model, calculate the predicted value of the compressive resilient modulus of cement stabilized macadam in the case of a single-layer base layer ( ), and the calculation results are shown in the following Tables 4-6: Table 4 Compressive Resilient Modulus of Cement Stabilized Macadam Predicted Value (4%)

[0034] Table 5 Compressive Resilient Modulus of Cement Stabilized Macadam Predicted Value (5%)

[0035] Table 6 Compressive Resilient Modulus of Cement Stabilized Macadam Predicted Value (6%)

[0036] Using the equivalent age-compressive resilient modulus prediction model, predict the compressive resilient modulus of the lower base layer in the case of a double-layer base layer ( ), where The prediction results are shown in the following Tables 7-9: Table 7 Compressive Resilient Modulus of the Lower Layer When the Upper Layer Temperature is 10°C Predicted Value (4%)

[0037] Table 8 Compressive Resilient Modulus of the Lower Layer When the Upper Layer Temperature is 20°C Predicted Value (5%)

[0038] Table 9 Compressive Resilient Modulus of the Lower Layer When the Upper Layer Temperature is 30°C Predicted Value (6%)

[0039] Step 3: Using pavement mechanics software, calculate the deflection values at the top of the base layer under the coupling of factors such as cement dosage, base layer temperature, curing age, base layer thickness, and subgrade resilient modulus for single-layer and double-layer base layer conditions; In this example, through the pavement mechanics analysis software, the distribution range of the deflection values at the top of the base layer for the single-layer base layer condition is [0.769, 2.557], and the distribution range of the deflection values at the top of the base layer for the double-layer base layer condition is [0.450, 2.000].

[0040] Step 4: Establish a prediction model for the construction quality evaluation standard of cement stabilized macadam base based on deflection values; In order to obtain the prediction model for the distribution range of the deflection values at the top of the base layer in different pavement structures, this example is demonstrated with the help of a multiple Logistic regression model. Multiple Logistic regression analysis uses a non-linear function to process the relationship between multiple independent variables and the dependent variable, and converts this relationship into a probability output. In S4, the establishment of the prediction model for the construction quality evaluation standard of cement stabilized macadam base based on deflection values considers the prediction of the deflection standard value range as a multi-classification problem, and respectively establishes multiple logistic regression prediction models for the construction quality evaluation standards of single-layer and double-layer cement stabilized macadam bases.

[0041] The functional form of the multiple logistic regression model in this example is as follows:

[0042] In the formula is the constant term, is the independent variable, is the regression coefficient.

[0043] In this example, the deflection values at the top of the base layer calculated for the single-layer and double-layer base layers are grouped by setting thresholds. For the single-layer multinomial logistic regression model, the dataset is divided into 4 levels, and the corresponding values are assigned as k = 1, k = 2, …, k = 4, where 1 represents the deflection value y ∈ [0.75, 1.05]; 2 represents the deflection value y ∈ [1.05, 1.20); 3 represents the deflection value y ∈ [1.20, 1.41); 4 represents the deflection value y ∈ [1.41, 2.56]; for the double-layer multinomial logistic regression model, the dataset is divided into 4 levels, 1 represents the deflection value y ∈ [0.45, 0.64]; 2 represents the deflection value y ∈ [0.64, 0.75); 3 represents the deflection value y ∈ [0.75, 0.90); 4 represents the deflection value y ∈ [0.90, 2.00]. With the help of IBM SPSS Statistics software, the weight coefficients of each characteristic index are calculated. Taking the last level 4 as the reference class, a prediction model for the range of the construction quality evaluation standard of the cement stabilized macadam base layer based on the deflection value is preliminarily constructed. The multinomial logistic regression fitting equation of the construction quality evaluation standard of the cement stabilized macadam base layer based on the deflection value finally obtained in this example is as follows: Prediction model for the evaluation standard based on the deflection value of the single-layer base layer: ; ; ; Prediction model for the evaluation standard based on the deflection value of the double-layer base layer: ; ; ; Perform the goodness-of-fit test for multinomial logistic regression. The results of the goodness-of-fit test are shown in Table 10 below.

[0044] Table 10 Goodness-of-fit test table

[0045] The larger the chi-square value, the stronger the correlation. The P-values of the Pearson statistic and the Deviance statistic in the table are both greater than 0.05. Therefore, under the condition of the significance level = 0.05, it shows that the fitting effects of the two multinomial logistic regression models are both relatively good.

[0046] Perform the likelihood ratio test and significance test for multinomial logistic regression. Compare the likelihood ratio of the final model using all covariates and the model with only the constant term to evaluate the significance of the multinomial logistic regression model. The test results are shown in Table 11 below.

[0047] Table 11 Likelihood Ratio Test Table of the Prediction Model

[0048] The smaller the -2 log-likelihood value and the significance level (P value < 0.05), the more significant the statistical property of the model. As can be seen from the above table, the intercept values of the -2 log-likelihood values are all greater than the final values; at the same time, the significance levels of the two final models are both less than 0.05, indicating that the independent variables have significant explanatory power for the dependent variable in the above two models, that is, the model fitting degree is relatively high.

[0049] Next, verify the three prediction equations for the evaluation criteria of the single-layer base based on the deflection value: Randomly select a set of data from the original data, that is, X1 = 4, X2 = 14, X3 = 30, X4 = 16, X5 = 40, and substitute it into the prediction equation of the single-layer base deflection value, and we can get: ; ; ; ; It can be seen that the probability of Y = 3 is the highest. Therefore, at this time, the standard deflection value of the cement stabilized macadam base is most likely to be concentrated between 1.20 mm and 1.40 mm, and the measured value of the deflection at the top surface of the base is 1.380 mm, which falls within the predicted value range. So the above three prediction equations meet the requirements.

[0050] Next, verify the three prediction equations for the evaluation criteria of the double-layer base deflection value: Randomly select a set of data from the original data, that is, X1 = 4, X2 = 28, X3 = 10, X4 = 36, X5 = 50, and substitute it into the prediction equation of the single-layer base deflection value, and we can get: = 0.044719376 = 0.912699677 = 0.042580946 = 1.18031E-14 It can be seen that the probability of Y = 2 is the highest. Therefore, at this time, the standard deflection value of the cement stabilized macadam base is most likely to be concentrated between 0.64 mm and 0.75 mm, and the measured value of the deflection at the top surface of the base is 0.649 mm. So the above three prediction equations meet the requirements.

[0051] Step 5: Determine the value range of the construction quality evaluation standard for the cement stabilized macadam base based on the deflection value.

[0052] Input the cement dosage \(x\), base course temperature \(T\), curing age \(t\), base course thickness \(H\), and subgrade resilient modulus \(E\) of the pavement base to be predicted into the obtained multiple logistic regression prediction model. 0 , and calculate the standard value range. Select a measured value on the test road with a cement dosage of 4%, a measured base course temperature of 25.7 °C, a curing age of 13 days, a single-layer base course thickness of 16 cm, and a subgrade resilient modulus of 40 MPa. Substitute it into the construction quality prediction model of the single-layer cement stabilized macadam base course and verify that the probability of falling into interval 3 is greater. The distribution interval of this standard deflection value is the construction quality evaluation standard for the cement stabilized macadam base course during construction, that is, the standard value range for evaluating the construction quality of the single-layer cement stabilized macadam base course at this time is [1.20 mm, 1.41 mm]. When it is a double-layer situation, with a cement dosage of 5%, a measured base course temperature of 15.6 °C, a curing age of the topmost base course of 9 days, a thickness of 32 cm for the two-layer base course, and a subgrade resilient modulus of 40 MPa, substitute it into the construction quality prediction model of the double-layer cement stabilized macadam base course and verify that the probability of falling into interval 3 is greater, that is, the standard value range for evaluating the construction quality of the double-layer cement stabilized macadam base course at this time is [0.75 mm, 0.90 mm].

[0053] The present invention can simultaneously consider the influence of factors such as cement dosage, base course temperature, curing age, base course thickness, and subgrade resilient modulus on the deflection value of the top surface of the cement stabilized macadam base course. Using this method, the standard value range for evaluating the quality of the cement stabilized macadam base course can be calculated, and the construction quality of the cement stabilized macadam base course can be evaluated by comparing and analyzing the relationship between the measured deflection value and this evaluation standard value range.

[0054] The above has described the embodiments of the present invention in detail, but the present invention is not limited to the described embodiments. For those skilled in the art, without departing from the principles and spirit of the present invention, various changes, modifications, substitutions, and variations made to these embodiments still fall within the protection scope of the present invention.

Claims

1. A standard method for evaluating the construction quality of cement-stabilized crushed stone base based on deflection value, characterized by: The following steps are involved: Step 1: Analyze the influencing factors of the construction quality evaluation index of cement stabilized crushed stone base, and select cement dosage x, base temperature T, curing age t, base thickness H, and soil base rebound modulus E0 as independent variables; Step 2: Calculate the compressive resilience modulus of each base layer in single-layer and double-layer situations through the cement-stabilized crushed stone equivalent age-compressive resilience modulus estimation model , , : Step 3: Use pavement mechanics software to calculate the top deflection value of the base layer under the coupling of cement dosage, base layer temperature, curing age, base layer thickness and soil base rebound modulus in single-layer and double-layer base layers; Step 4: Establish a prediction model for the construction quality evaluation standard of cement-stabilized crushed stone base based on deflection value; Step 5: Determine the standard value range for the construction quality assessment of cement-stabilized crushed stone base based on deflection value.

2. The method for evaluating the construction quality of cement-stabilized crushed stone base based on deflection value according to claim 1 is characterized by: The cement stabilized crushed stone equivalent age-compressive resilience modulus estimation model in step 2 uses the formula Nonlinear fitting was performed to predict the compressive rebound modulus at different cement dosages through equivalent age; Where E represents the compressive rebound modulus, Represents equivalent age, A and B are parameters and dimensionless.

3. The method for evaluating the construction quality of cement-stabilized crushed stone base based on deflection value according to claim 1 or 2, characterized in that: The equivalent age refers to the age of each base layer at different temperatures being equivalent to the age of curing at standard temperature, including the equivalent age of a single-layer base layer and the equivalent age of a double-layer base layer.

4. The standard method for evaluating the construction quality of cement-stabilized crushed stone base based on deflection value according to claim 3 is characterized by: The equivalent age of the single-layer base The calculation method is as follows: ， In the formula, Indicated in Temperature health Day relative to standard temperature The equivalent age of the next regimen, d; =1 represents 10℃, =2 represents 30℃; =1, 2, 3, 4 represent 3d, 7d, 14d, 28d health care age; The standard temperature is usually 20°C; Indicates health temperature ℃; is the gas constant, and its value is 8.3144 ; Ea is the activation energy, J / mol.

5. The method for evaluating the construction quality of cement-stabilized crushed stone base based on deflection value according to claim 3 is characterized by: The double-layer base equivalent age includes the equivalent age of the lower base when the double-layer base is used and the equivalent age of the upper base when the double-layer base is used, wherein the calculation formula of the equivalent age of the lower base is as follows: ， In the formula Indicates the equivalent age of the lower base layer in the case of a double-layer base layer, In the case of double-layer base, the upper base is at a temperature Health Days are the equivalent age of health maintenance at standard temperature.

6. The method for evaluating the construction quality of cement-stabilized crushed stone base based on deflection value according to claim 1 is characterized by: The step 4 specifically includes: The prediction of the standard range of deflection is regarded as a multi-classification problem. The multivariate logistic regression prediction model of the construction quality evaluation standard of single-layer and double-layer cement-stabilized crushed stone base is established respectively, and the distribution range of single-layer and double-layer deflection is graded and assigned. The functional form of the multivariate logistic regression model is as follows: ， In the formula is a constant term, is the independent variable, is the regression coefficient.

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