A method for predicting rutting depth taking into account the effect of temperature

Abstract

To provide a practical prediction method capable of predicting the amount of rutting in asphalt pavement in consideration of the influence of temperature.SOLUTION: A method for predicting a rutting amount comprises the steps of: obtaining the amount of permanent deformation of the pavement expected to occur during the design period due to the assumed traffic load for each layer constituting the asphalt pavement and in units of partial periods constituting the design period; making a predetermined representative temperature for the temperature range to which the average temperature of the layer in the partial period belongs to a deemed layer temperature of the layer in the partial period; and using a material constant and / or a physical property at a deemed layer temperature as a material constant and / or a physical property value to be used, when calculating the amount of permanent deformation of the layer in the partial period.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for predicting the amount of rutting, and more particularly to a method for predicting the amount of rutting in an asphalt pavement under conditions that take into account the influence of temperature. [Background technology]

[0002] Rutting is a displacement in the depth direction that occurs on the surface of asphalt pavement where wheels pass.If rutting becomes large, rainwater and other liquids can accumulate in the depressions that have been displaced in the depth direction, which not only causes tire slippage, water splashing, and hydroplaning, but also induces water penetration into the pavement, making rutting an undesirable phenomenon.

[0003] Rutting is generally said to have two causes: 1) Deformation and lateral movement of the surface asphalt mixture due to repeated wheel passage (repeated loading). 2) Accumulation of residual deformation that occurs in each layer of asphalt pavement due to repeated wheel passage (repeated loading).

[0004] In recent years, the development of superior materials such as polymer-modified asphalt has led to progress in countermeasures against rutting caused by cause 1), which has tended to be significantly reduced. On the other hand, for rutting caused by cause 2), countermeasures must be taken for the entire asphalt pavement, but at present there is no practical method for accurately predicting the amount of rutting for the entire pavement, including the roadbed and subgrade, before the pavement is put into service. For example, as seen in Patent Documents 1 and 2, the only technology proposed is to determine the amount of rutting that has already occurred after the fact by conducting a road surface property survey.

[0005] The difficulty in accurately predicting the amount of rutting, which is the cumulative residual deformation that occurs in each layer of asphalt pavement, is thought to be largely due to the structure of the asphalt pavement and the properties of the asphalt mixture. In other words, asphalt pavement is usually composed of a layer of asphalt mixture and the subgrade and roadbed layers underneath, and residual deformation due to repeated loading appears as the sum of the deformation amounts in the depth direction of each layer. For this reason, in order to predict the amount of rutting due to the cumulative residual deformation, it is necessary to make a prediction that includes not only the layer of asphalt mixture, but also the roadbed and roadbed.

[0006] Another major factor is that the physical properties of asphalt change significantly with temperature, so the impact of temperature must be taken into account when predicting the amount of rutting caused by the accumulation of residual deformation. The surface layer of an asphalt pavement is directly affected by sunlight, wind, rain, and other factors, and heats and cools easily, whereas the layers below it take time for heat from the surface to be transmitted, making them slower to heat and cool. Therefore, even on a daily basis, a temperature gradient is thought to exist across the depth of the asphalt pavement. Taking seasonal changes into account, the temperature of the asphalt pavement is thought to vary greatly and in complex ways throughout the year. To predict the amount of rutting that takes temperature into account, it is necessary to take into account the impact of temperature, which varies throughout the year, across the entire asphalt pavement. While this is theoretically possible, it is extremely difficult in practice.

[0007] In the future, deregulation is expected to lead to an increase in the size and number of vehicles, as seen in the increase in large trailers, and as a result, it is thought that the occurrence of rutting due to the accumulation of residual deformation will increase. Under these circumstances, in order to take effective measures against rutting, a practical method is needed that makes it possible to predict the amount of rutting due to the accumulation of residual deformation in asphalt pavement at the pavement design stage. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-217084 [Patent Document 2] Japanese Patent Application Publication No. 2020-190438 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention was made in consideration of the above circumstances, and aims to provide a practical prediction method that makes it possible to predict the amount of rutting in asphalt pavement while taking into account the effects of temperature. [Means for solving the problem]

[0010] To solve the above problems, the inventors conducted extensive research and trial and error. They came up with the idea of ​​dividing the design period into subperiods of appropriate length and predicting the amount of permanent deformation in the depth direction of the pavement for each subperiod and for each layer that constitutes the asphalt pavement. Furthermore, by associating a pre-classified and unified "determined layer temperature" with the subperiod of the layer for which permanent deformation is to be predicted, they found that it is possible to predict permanent deformation for each layer and subperiod without excessive burden, while taking into account the influence of temperature. To calculate the cumulative deformation of the entire asphalt pavement over the entire design period, the permanent deformation calculated for each subperiod and for each layer can be added together for all subperiods and all layers.

[0011] That is, the present invention provides a method for predicting the amount of rutting in an asphalt pavement, comprising: (A) determining the amount of permanent deformation in the depth direction of the pavement that is predicted to occur during the design period due to the expected traffic load for each layer that constitutes the asphalt pavement and for each partial period that constitutes the design period; and (a) adding up the determined permanent deformation amounts for all layers for which the permanent deformation amounts were determined and for all partial periods for which the permanent deformation amounts were determined, and setting the result as a predicted value for the amount of rutting in the design period, The step (a) (c) among the layers for which the permanent deformation amount is to be calculated, for a layer for which the amount of permanent deformation to be calculated may be affected by temperature, a step of setting a predetermined representative temperature for a temperature range to which the average temperature of the layer in the partial period belongs as the deemed layer temperature of the layer in the partial period; (e) The above problem is solved by providing a method for predicting the amount of rutting in asphalt pavement that takes into account the effects of temperature, which includes a step of using the material constants and / or physical property values ​​at the assumed layer temperature as the material constants and / or physical property values ​​to be used when calculating the amount of permanent deformation of the layer in question during the relevant partial period.

[0012] As described above, in the prediction method according to the present invention, a single deemed layer temperature corresponding to the average temperature for each partial period of each layer constituting an asphalt pavement is assigned. Then, when calculating the permanent deformation for each layer and for each partial period, the material constants and / or physical properties at that deemed layer temperature are used. Therefore, it is not necessary to calculate the material constants and physical properties in detail for each temperature, and it is not necessary to perform complicated calculations that take into account the complex daily changes in temperature. This makes it possible to calculate the predicted permanent deformation while taking into account the effects of temperature.

[0013] The average temperature for each partial period of a layer whose permanent deformation may be affected by temperature may be calculated by averaging actual measurements, or may be calculated from temperature data such as the average temperature for the partial period. When calculating from temperature data, it is of course preferable to use temperature data for the area where the asphalt pavement to be designed is to be constructed.

[0014] In a preferred embodiment, the partial periods that make up the design period are periods measured in calendar months. The design period for asphalt pavement is usually measured in years and often spans multiple years. When the design period spans multiple years, for example, January of the first year and January of the following year are considered equivalent partial periods, and the same is true for February, March, etc. Therefore, when the design period spans multiple years, January and February may be combined into a single partial period or group of partial periods, with January being January and February being February, respectively.

[0015] In another preferred embodiment, the predicted permanent deformation is calculated for each layer and for each partial period based on the following formula (4):

number

[0016] As mentioned above, R (i,m) is the predicted value of the permanent deformation obtained for each layer i and for each partial period m, so by adding these values ​​for all layers and all partial periods, the predicted value of the rutting amount can be obtained.

[0017] Furthermore, in another preferred aspect, the prediction method of the present invention includes a step of determining the predicted amount of permanent deformation of the pavement in the depth direction for each layer constituting the asphalt pavement, and for each partial period group, which is a group of one or more partial periods having the same assumed layer temperature, and a step of adding up the determined permanent deformation amounts for all layers for which the permanent deformation amounts have been determined, and for all partial period groups for which the permanent deformation amounts have been determined, to obtain a predicted value for the amount of rutting in the design period.

[0018] In the above embodiment, the predicted permanent deformation amount for each layer constituting the asphalt pavement and for each sub-period group is calculated based on the following formula (7):

number

[0019] In another preferred aspect, the prediction method of the present invention includes a step of determining the predicted amount of permanent deformation in the depth direction of the pavement for each layer constituting the asphalt pavement and for each temperature condition group, which is a group consisting of one or more partial periods in which the assumed layer temperature is the same for all corresponding layers, and a step of calculating the predicted amount of rutting by adding up the determined permanent deformation amounts for all layers for which the permanent deformation amounts were determined and for all temperature condition groups for which the permanent deformation amounts were determined.

[0020] In a preferred embodiment, the predicted permanent deformation amount is calculated for each temperature condition group and for all layers based on the following formula (10):

number

[0021] When the predicted permanent deformation is calculated for each temperature condition group for all layers, the predicted rutting amount can be calculated using the following formula (11):

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[0022] The present invention provides the advantage that the amount of rutting in an asphalt pavement can be accurately predicted without undue burden, taking into account the influence of temperature. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a graph showing the relationship between the number of loadings and permanent set obtained in an FN test. [Figure 2] 1 is a graph plotting the relationship between the ratio of permanent strain εp to elastic strain εe and the number of loadings. DETAILED DESCRIPTION OF THE INVENTION

[0024] The method for predicting the amount of rutting according to the present invention includes the steps of (a) determining the amount of permanent deformation in the depth direction of the pavement that is predicted to occur during a design period due to anticipated traffic loads for each layer constituting the asphalt pavement and for each partial period constituting the design period, and (b) adding up the determined amounts of permanent deformation for all layers for which the amounts of permanent deformation were determined and for all partial periods for which the amounts of permanent deformation were determined, and calculating the result as the predicted amount of rutting for the design period.

[0025] <Layer structure of asphalt pavement> An example of the layer structure of an asphalt pavement targeted by the prediction method according to the present invention is shown in Table 1 below.

[0026] [Table 1]

[0027] As shown in Table 1, the asphalt pavement shown in the example consists of five layers, starting from the pavement surface: surface layer, intermediate layer, base layer, subgrade, and roadbed. The subgrade is further divided into three layers depending on the materials used: asphalt stabilized layer, graded crushed stone layer (upper subgrade), and crushed run layer (lower subgrade), for a total of seven layers that make up the asphalt pavement.

[0028] The method of dividing the multiple layers that make up an asphalt pavement is not limited to that shown in Table 1, but for the purpose of calculating the amount of permanent deformation for each layer, it is advisable to classify layers made of materials that are expected to have a different response to the expected wheel load as separate layers. Also, when calculating the amount of permanent deformation for each layer and for each partial period, the effect of the temperature of that layer during that partial period is taken into account, so even if layers are made of the same material, it is advisable to classify parts at different depths from the surface that are expected to have significantly different average temperatures during the partial period as separate layers.

[0029] <Partial period> On the other hand, partial periods constituting a design period include, for example, partial periods obtained by dividing the design period by the length of each calendar month. If the calendar months are used as partial periods, then if the design period is one year, the design period will be composed of 12 partial periods from January to December. If the design period is less than one year or longer than one year, the design period will be composed of partial periods equal to the number of months that make up the design period. If the design period spans multiple years, it is considered that one year will be repeated under the same conditions, so for example, January of each year is considered to be an equivalent partial period, and the same is true for February, March, etc. Therefore, as mentioned above, January and February may be grouped together as a single partial period or group of partial periods, with each month being considered January and February, respectively.

[0030] However, partial periods are not limited to calendar months. Instead of dividing partial periods from January to December by the length of each calendar month, a year may be divided into 12 equal parts, with each partial period having a length of 365 days / 12, or any number of partial periods of any length may be set.

[0031] However, if the length of the partial period is too short, the amount of work required to calculate the permanent deformation becomes excessive, which may make it impractical, and is therefore undesirable. Conversely, if the length of the partial period is too long, the error in considering the effect of temperature becomes large, which may make it impossible to make an accurate prediction, and is therefore undesirable. The length of each partial period should preferably be at least one week, and at most three months, but it is most convenient to use a calendar month as the partial period.

[0032] <Predicted permanent deformation> There are no particular restrictions on the method for calculating the predicted permanent deformation for each layer and for each partial period based on the layer structure of the asphalt pavement in question, the design period, and the partial periods that make up the design period. Any method may be used as long as it is possible to calculate the predicted permanent deformation for each layer and for each partial period. For example, it is preferable to use the following formula (1) described on page 76 of "Pavement Engineering Library 7: Fundamentals of Pavement Engineering," Japan Society of Civil Engineers, March 2012.

number

[0033] Permanent set ε p Multiplying this by the thickness hi of layer i gives the permanent deformation Ri of layer i. p is expressed by the above formula (1), the permanent deformation Ri of the layer i can be calculated by the following formula (2).

number

[0034] <Deemed layer temperature> As mentioned above, the material constants αi and βi of layer i are temperature-dependent material constants. However, the temperature of each layer that makes up the asphalt pavement varies from layer to layer, changes daily, and is usually different between day and night even on a daily basis. Therefore, it is not realistic to calculate the material constants αi and βi of layer i taking into account the complex changes in the temperature of each layer. Therefore, in this invention, the assumed layer temperature Tim is used as the temperature of layer i.

[0035] That is, the deemed layer temperature Tim is a temperature determined based on the average temperature of layer i in a partial period m for which the permanent deformation is to be calculated, and a representative temperature predetermined for the temperature range to which the average temperature belongs is set as the deemed layer temperature Tim for the partial period of the layer. The relationship between the predetermined temperature range and the similarly predetermined representative temperature is, for example, as shown in Table 2.

[0036] [Table 2]

[0037] For example, if the average temperature in partial period m of layer i is 22.0°C, the temperature range to which that average temperature belongs is the first temperature range, which is set to a temperature range of "up to 25.0°C," so the representative temperature of 20°C, which is preset for the first temperature range, is the deemed layer temperature Tim in partial period m of layer i. Similarly, if the average temperature in partial period m of layer i is 27.0°C, the temperature range to which that average temperature belongs is the second temperature range, which defines a temperature range of "greater than 25.0°C to 35.0°C," so the representative temperature of 30°C, which is preset for the second temperature range, is the deemed layer temperature Tim in partial period m of layer i. Similarly, for a layer and partial period whose average temperature belongs to the third temperature range, which defines a temperature range of "greater than 35.0°C to 45.0°C," the deemed layer temperature Tim is 40°C.

[0038] The temperature ranges and representative temperatures shown in Table 2 are merely examples, and the number of temperature ranges, the respective temperature ranges, and the representative temperatures are not limited to those shown in Table 2. The temperature range of 25.0°C or less may be divided into two or more temperature ranges, or a temperature range above 45.0°C may be set. For example, five temperature ranges may be set from 0°C to 50°C in increments of 10°C. A representative temperature different from those shown in Table 2 may be set for each temperature range, but it is preferable to set approximately the midpoint of the set temperature range as the representative temperature.

[0039] Although the assumed layer temperature can be calculated for all layers that make up the asphalt pavement in question, it is more reasonable to calculate it only for those layers for which the amount of permanent deformation is being calculated and for which the amount of permanent deformation is likely to be affected by temperature. For example, in the layer structure shown in Table 1, the surface layer, intermediate layer, base layer, and asphalt stabilized layer are likely to have their permanent deformations affected by temperature, so it is best to calculate the assumed layer temperature for each partial period for at least these layers.

[0040] On the other hand, the average temperature of layer i during partial period m can be determined by any suitable method. For example, if there is already average temperature data obtained by actual measurements for asphalt pavement with a similar layer structure that already exists in an area where the same or similar weather conditions are expected, or if it is possible to obtain average temperature data by actual measurements, then the actually measured average temperature can be used.

[0041] If there is no actual measured average temperature data or it is difficult to obtain it by actual measurement, the average pavement temperature Mp for each layer during each partial period can be obtained from the temperature data for the relevant region using the following formula (5.3.3) described in "5-3-2 Structural Design Conditions" in the "Pavement Design Handbook," compiled by the Japan Road Association, February 2006, pp. 113-118.

number

[0042] In addition, in the above-mentioned section of the Pavement Design Handbook, after explaining the symbols used in equation (5.3.3), it states, "The average temperature of a layer is the temperature at a position h' / 3 from the top surface of that layer (thickness = h'). Therefore, the average temperature of a layer is the depth from the road surface to the top of that layer plus h' / 3, which is z."

[0043] Based on this, the average temperatures for each layer during each subperiod were calculated for the case where an asphalt pavement with the layer configuration shown in Table 1 was constructed in a certain assumed area. The subperiods were 12 subperiods, measured in calendar months from January to December. The monthly mean temperature Ma was calculated from the monthly mean temperatures published for the target area over the past five years. The value z was calculated by adding one-third of the layer thickness to the depth of the top surface of each layer from the pavement surface. Note that the temperature data used to calculate the monthly mean temperature Ma is not limited to the past five years. Monthly mean temperatures Ma calculated from monthly mean temperatures over periods shorter or longer than five years can also be used. Of the layer configurations shown in Table 1, the fine-grained crushed stone layer, crushed run layer, and subgrade were not included in the calculation of the average temperature because it was determined that the permanent deformation of these layers was unlikely to be affected by temperature. The results are shown in Table 3.

[0044] [Table 3]

[0045] The average temperature in each partial period for each layer listed in Table 3 is applied to the relationship between the temperature range and representative temperature in Table 2, and the assumed layer temperature is calculated as shown in Table 4 below.

[0046] [Table 4]

[0047] <Material constants α, β> Once the assumed layer temperature Tim for each layer in each partial period is determined, the elastic modulus of each pavement material determined by the DM test (Dynamic Modulus test), the number of loadings determined by the FN test (Flow Number test) and the permanent strain ε p / elastic strain ε e ) the material constants α and β of each layer at each assumed layer temperature can be calculated.

[0048] The DM test is a test to measure the dynamic modulus of elasticity E of an asphalt mixture using AMPT. * As described in the "Study on the Relationship between Resistance to Plastic Deformation and Resistance to Plastic Deformation" at the 72nd Annual Academic Conference of the Japan Society of Civil Engineers, September 2017, presentation number V-008, a triaxial repeated compression test was conducted. A load was applied to a cylindrical specimen with displacement gauges attached to three points on the side so that a certain strain would occur, and the dynamic modulus of elasticity E was calculated from the stress and strain. * The FN test is a test to determine the dynamic modulus of elasticity E of asphalt mixtures using the same AMPT method. * As described in "Study on the Relationship between Creep Strength and Plastic Deformation Resistance," 72nd Annual Academic Conference of the Japan Society of Civil Engineers, September 2017, presentation number V-008, this is a stress-controlled repeated compression test, in which a creep curve is obtained by measuring the plastic strain that occurs when repeated loading is applied, and the number of loadings FN until the rate of change of plastic strain changes from a decrease to an increase is calculated.

[0049] Table 5 shows the conditions for the DM test, and Table 6 shows the conditions for the FN test.

[0050] [Table 5]

[0051] [Table 6]

[0052] In Tables 5 and 6, the test temperatures of 20°C, 30°C, and 40°C correspond to the assumed layer temperatures of each layer shown in Table 4, and the loading pressure of 0.70 MPa in Table 6 corresponds to a wheel load of 5.75 tons, and is a loading pressure that takes into account the expected increase in the size of vehicles in the future.

[0053] Using the DM test described above, the elastic modulus at each temperature was determined for the asphalt mixture (Material A) used primarily for the intermediate or base layer, the asphalt mixture (Material B) used primarily for the surface layer, and the asphalt stabilized layer. The results are shown in Table 7.

[0054] [Table 7]

[0055] The elastic modulus values ​​for graded crushed stone and crushed run in Table 7 are taken from the Pavement Design Handbook, compiled by the Japan Road Association, February 2006, pp. 113-118, and Table 5.3.1 on page 117 of "5-3-2 Structural Design Conditions." Regarding the subgrade, page 114 of the Pavement Design Handbook states, "When the CBR value is required, the elastic modulus is usually estimated from equation (5.3.1)." Based on this, the elastic modulus E = 10CBR. Since the design CBR of the assumed subgrade is 12, we set the elastic modulus to 120, which is 10 times that value. Furthermore, because these graded crushed stone, crushed run, and subgrade are pavement materials that do not contain asphalt, their elastic modulus is assumed to be constant regardless of temperature.

[0056] The results of the FN test conducted on Material A at a test temperature of 40°C are shown in Figure 1. As shown in Figure 1, in the FN test, the number of loadings N at a loading pressure of 0.70 MPa and the resulting permanent strain ε p A relationship with this is required.

[0057] On the other hand, the elastic strain ε e is calculated from the load pressure σ (0.7 MPa) applied during the FN test and the elastic modulus E of each material obtained in the DM test. e =σ / E, so these ε p , N, ε e Based on the relationship and the above-mentioned formula (1), the material constants α and β of the material subjected to the DM test and the FN test can be calculated.

[0058] That is, equation (1) is as follows:

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[0059] As described above, the DM test and FN test were performed while changing the temperature and material, and the material constants α and β of each material at each temperature were determined as shown in Table 8 below.

[0060] [Table 8]

[0061] For the material constants α and β, if available, literature values ​​can be used. This is particularly advantageous for subgrades and roadbeds, where temperature is not considered to have a significant effect, since there is no need to be concerned about the temperature at which the material constants are calculated. For example, for granular materials such as crushed stone and crusher run, which are used in roadbeds, the material constants α and β for granular materials listed in "Pavement Engineering Library 7: Fundamentals of Pavement Engineering," Japan Society of Civil Engineers, March 2012, p. 77, Example 3.13 can be used. For subgrades, the material constants α and β for gravelly soil listed in "Pavement Engineering Library 7: Fundamentals of Pavement Engineering," Japan Society of Civil Engineers, March 2012, p. 77, Table 3.7 can be used.

[0062] <Elastic strain ε e > Elastic strain ε in each layer of asphalt pavement ecan be calculated using the pavement structure analysis program "GAMES" based on the multilayer elastic theory, which is introduced along with its operating method in "Pavement Engineering Library 3: Introduction to Pavement Structure Analysis Using Multilayer Elastic Theory," Japan Society of Civil Engineers, April 2005, pp. 69-94. In other words, by setting the required analysis conditions such as temperature, elastic modulus of each layer, Poisson's ratio, subgrade thickness, interlayer slip ratio, and loading conditions according to the operating method of "GAMES," and then running the program, the elastic strain ε generated in each layer of the asphalt pavement can be calculated. e can be obtained.

[0063] The temperature is assumed to be 20°C, 30°C, or 40°C (the assumed layer temperature). The modulus of elasticity is the value shown in Table 7. The subgrade thickness is the standard 100 cm. The interlayer slip ratio is 0 (because the asphalt mixture is bonded with a tack coat), and 0.99 (between the asphalt mixture and the subbase, between the subbase and the subbase, and between the subbase and the subgrade) because they are all unbonded. The loading condition is set to 56.35 kN, taking into account the expected increase in vehicle size. The Poisson's ratio for each material can be the value listed in the Pavement Design Handbook, compiled by the Japan Road Association, February 2006, pp. 113-118, or in Table 5.3.1 on page 117 of "5-3-2 Structural Design Conditions."

[0064] <Length of partial period> On the other hand, the length of a partial period is reflected in the number of passing wheels N, i.e., the number of times the wheel load acts. For example, if the design period consists of 12 partial periods, the length of the partial period is reflected by setting the number of passing wheels in the partial period to 1 / 12 of the total number of passing wheels expected in the design period.

[0065] <Permanent deformation of each story in partial period units> As described above, the material constants α and β at each assumed layer temperature and the elastic strain ε of each layer are calculated. e Once this is known, the permanent deformation of layer i in partial period m can be calculated using the following equation (4).

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[0066] <Predicted amount of rutting> The predicted permanent deformation R of the layer i in the partial period m (i,m) The predicted value R of the amount of rutting can be calculated by adding up the values ​​for all layers and all partial periods. That is, the predicted value R of the amount of rutting can be calculated by the following formula (5) or (6).

number

number

[0067] As described above, in the prediction method according to the present invention, the deemed layer temperature of each layer is calculated for each of the multiple partial periods that make up the design period, and the amount of permanent deformation predicted for each layer and for each partial period is calculated using physical properties such as the material constants α and β of each material at the deemed layer temperature Tim in each partial period of each layer, and similarly the elastic coefficient E of each material at the deemed layer temperature Tim in each partial period of each layer. This has the advantage that the predicted amount of rutting can be calculated taking into account the effects of temperature within the normally expected range of effort and time, without requiring excessive time and effort or a huge amount of calculation.

[0068] In the above example, the predicted permanent deformation amount is calculated for each layer and for each partial period. However, it is also possible to set a partial period group, which is a group of one or more partial periods having the same assumed layer temperature, and calculate the predicted permanent deformation amount for each layer and for each partial period group.

[0069] In this case, the amount of permanent deformation predicted for each layer and for each partial period group is calculated for each layer and for each partial period group based on the following formula (7).

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[0070] To obtain the predicted amount of rutting, the amount of permanent deformation obtained for each layer and for each sub-period group may be added together for all layers and for all sub-period groups. That is, the predicted value R of the amount of rutting can be calculated by the following formula (8) or (9).

number

number

[0071] As described above, when the amount of permanent deformation is calculated for each partial period group, which is a group of one or more partial periods having the same assumed layer temperature, the amount of rutting that can be predicted can be calculated with less work than when the amount of permanent deformation is calculated for each layer and for each partial period.

[0072] Furthermore, in the above example, the predicted permanent deformation amount is calculated for each layer and for each partial period unit or for each partial period group. However, it is also possible to set a temperature condition group consisting of one or more partial periods in which the deemed layer temperature is the same for all corresponding layers, and to calculate the predicted permanent deformation amount for each layer and for each temperature condition group.

[0073] The temperature condition group will be explained below using the assumed bed temperature shown in Table 4 as an example.

[0074] [Table 9]

[0075] As described above, in the example shown in Table 9, during the seven-month partial periods from January to April and October to December, the deemed layer temperatures of the surface layer, middle layer, base layer, and AS stabilization layer are all 20°C, and since the deemed layer temperatures are the same for all corresponding layers, this is considered to be one temperature condition group A.

[0076] However, when comparing April and May, the deemed layer temperatures of the base layer and the AS stabilized layer are both the same at 20°C, but for the surface and middle layers, the deemed layer temperature in April is 20°C, but in May it is 30°C, so it cannot be said that the deemed layer temperatures are the same for all corresponding layers. Therefore, May is classified as temperature condition group B, which is different from temperature condition group A. Since there is no other month in which the deemed layer temperature is the same as May in all corresponding layers, May alone constitutes temperature condition group B.

[0077] In June, July, and September, the deemed layer temperature was 30°C in all of the surface, middle, base, and AS stabilization layers, and the deemed layer temperature was the same for all corresponding layers, so these were grouped into one temperature condition group C. August differs from all other months in that the deemed layer temperature in the surface layer was 40°C, so it constitutes temperature condition group D by itself.

[0078] The assumed layer temperature for each layer in each temperature condition group and the percentage of the period each temperature condition group occupies in 12 months are shown in Table 10 below.

[0079] [Table 10]

[0080] When using the above-mentioned temperature condition groups, the expected number of passing wheels in each temperature condition group can be obtained by multiplying the total expected number of passing wheels in the design period by the proportion of the period occupied by each temperature condition group in the design period.

[0081] When the above temperature condition groups are used, the predicted permanent deformation amount can be calculated for each temperature condition group by the following formula (10).

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[0082] To obtain a predicted value of the amount of rutting, the permanent deformation Rp obtained for each temperature condition group is added together for all temperature condition groups, as shown in the following formula (11).

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[0083] By introducing the concept of temperature condition groups, the relationship between partial periods and assumed temperatures can be organized by dividing partial periods into temperature condition groups. This not only greatly simplifies calculations and work compared to determining the amount of permanent deformation for each layer and for each partial period, but is also expected to result in greater labor savings compared to determining the amount of permanent deformation for each layer and for each partial period group with the same assumed layer temperature.

[0084] <Example 1 of rutting prediction> For the asphalt pavement having the layer configuration shown in Table 11 below, the amount of permanent deformation was calculated for each layer and for each temperature condition group to determine the predicted amount of rutting.

[0085] [Table 11]

[0086] The construction locations were the same as those shown in Table 3 for the average temperatures over the past five years, and the temperature ranges and representative temperatures were also set in the same way as in Table 2, so the temperature condition groups and their proportions are as shown in Table 10 above.

[0087] Additionally, the elastic modulus of each material at each temperature was determined using the values ​​shown in Table 7, and the material constants α and β for Material A, Material B, and the asphalt stabilization layer were determined using the values ​​shown in Table 8. The material constants α and β for the grading-adjusted crushed stone, crusher run, and subgrade were determined using the values ​​shown in Table 12 below, based on values ​​given in the literature, and were assumed to be constant regardless of temperature.

[0088] [Table 12]

[0089] Using the pavement structure analysis program "GAMES" mentioned above, the analysis conditions were set in the same way as above, and the amount of elastic strain in the depth direction of the road for each layer was calculated for each temperature condition group. The results are shown in Table 13.

[0090] [Table 13]

[0091] The design period was set at 25 years, and the load pressure was set at 0.70 MPa, taking into consideration future increases in vehicle size. The number of vehicles passing over the 25-year design period was calculated based on the fatigue failure number of 35,000,000 passes / 10 years for traffic volume category N7, as given in Table 3.2.2 on page 30 of the "Pavement Design Handbook," published by the Japan Road Association, February 2006, and multiplied by 2.5 to arrive at 87,500,000 passes / 25 years.

[0092] Using the above values, the predicted value of the rutting depth was calculated based on equations (10) and (11). The results are shown in Table 14.

[0093] [Table 14]

[0094] <Example 2 of rutting prediction> For an asphalt pavement that had been constructed 9 years and 4 months ago and had rutting of up to 17 mm measured, the predicted amount of rutting was calculated using the above formulas (10) and (11) and compared with the actual measured value. The material constants α, β, and elastic modulus E of the materials that make up the asphalt pavement were calculated using the same materials as those used during construction. The layer structure of the asphalt pavement in question is shown in Table 15.

[0095] [Table 15]

[0096] The construction site was the same as the site where the average temperatures for the past five years were shown in Table 3, so the monthly average temperatures for each layer were set to the same values ​​as those shown in Table 3. The temperature ranges and representative temperatures were also set to the same values ​​as those in Table 2, so the temperature condition groups and their proportions are as shown in Table 10 above.

[0097] The elastic modulus E and material constants α and β at each assumed layer temperature for the polymer-modified Type II asphalt mixture and the straight asphalt mixture were determined using DM and FN tests, as described above. The loading pressure in the FN test was 0.63 MPa, equivalent to a normal design wheel load of 5 tons. The determined elastic modulus E and material constants α and β are shown in Tables 16 and 17, respectively. The elastic moduli for the asphalt stabilized layer, graded crushed stone, crusher run, and subgrade listed in Table 16 were the same as those listed in Table 7. As shown in Table 9 above, the assumed layer temperature of the asphalt stabilized layer at the target construction site never reached 40°C, so the material constants α and β at 40°C for the asphalt stabilized layer were not determined.

[0098] [Table 16]

[0099] [Table 17]

[0100] The material constants of the graded crushed stone, crusher run, and roadbed were set to the values ​​shown in Table 12 and were assumed to be constant regardless of temperature.

[0101] Using the pavement structure analysis program "GAMES" mentioned above, the analysis conditions were changed to correspond to the layer structure of the asphalt pavement being analyzed, and the amount of elastic strain in the depth direction of the road for each layer was calculated for each temperature condition group. The results are shown in Table 18.

[0102] [Table 18]

[0103] The design period was set at 9 years and 4 months, the period that has already elapsed on site, and the load pressure was set at 0.63 MPa, the current design value. The number of passing vehicles during the 9-year and 4-month design period was calculated based on the fatigue failure number of 35,000,000 passes / 10 years for traffic volume category N7, as listed in Table 3.2.2 on page 30 of the "Pavement Design Handbook," published by the Japan Road Association in February 2006, and multiplied by 9 years and 4 months to arrive at 32,666,667 passes / 9 years and 4 months.

[0104] Using the above values, the predicted value of the amount of rutting was calculated based on equations (10) and (11). The results are shown in Table 19.

[0105] [Table 19]

[0106] As described above, the predicted rutting depth obtained based on the prediction method of the present invention was 19.8 mm, which was in extremely good agreement with the maximum measured rutting depth of 17 mm at the actual site 9 years and 4 months after construction.

[0107] In the above prediction example, the percentage of each temperature condition group in the 12 months was multiplied by the total number of wheels passed over the 9-year, 4-month design period to determine the number of wheels passed over each temperature condition group, but the percentage of each temperature condition group may be adjusted depending on the month and year in which the 4-month portion exceeding the full 9 years falls. For example, if the 4-month excess is the 4 months from January to April, all of these belong to temperature condition group A, so the percentage of temperature condition group A is (7 months x 9 years + 4 months) / (12 months x 9 years + 4 months) x 100 = 67 months / 112 months x 100 = 59.8%, and the percentages of the other temperature condition groups will also change accordingly. [Industrial Applicability]

[0108] As explained above, according to the present invention, it is possible to very accurately predict the amount of rutting in an asphalt pavement under conditions that take into account the effects of temperature. The rutting amount prediction value provided by the present invention is extremely convenient for road managers and road builders, and has great industrial applicability.

Claims

1. A method for predicting the amount of rutting in an asphalt pavement, comprising: (A) determining the amount of permanent deformation in the depth direction of the pavement that is predicted to occur during the design period due to the expected traffic load for each layer that constitutes the asphalt pavement and for each partial period that constitutes the design period; and (a) adding up the determined permanent deformation amounts for all layers for which the permanent deformation amounts have been determined and for all partial periods for which the permanent deformation amounts have been determined, and setting the resulting value as a predicted value for the amount of rutting in the design period; The step (a) (c) among the layers for which the permanent deformation amount is to be calculated, for a layer whose permanent deformation amount may be affected by temperature, a step of setting a predetermined representative temperature for a temperature range to which the average temperature of the layer in the partial period belongs as the deemed layer temperature of the layer in the partial period; (D) A step of using material constants and / or physical property values ​​at the deemed layer temperature as material constants and / or physical property values ​​to be used when calculating the amount of permanent deformation of the layer in the partial period. A method for predicting the amount of rutting in asphalt pavement taking into account the effects of temperature.

2. 2. The method according to claim 1, wherein in the step (a), the predicted permanent deformation is calculated for each layer and for each partial period based on the following formula (4): [Equation 1] In the above formula, the meanings of the symbols are as follows: i: Layer number for which permanent deformation is to be calculated (i = 1, 2, 3, etc.) m: Partial period number for which permanent deformation is to be calculated (m = 1, 2, 3, ...) R （ｉ，ｍ） : Permanent deformation predicted for layer i in subperiod m Tim: Deemed layer temperature in the partial period m of the i layer α （ｉ，Ｔｉｍ） , β （ｉ，Ｔｉｍ） : material constant of layer i at assumed layer temperature Tim N ｍ : Number of passing wheels expected in partial period m (times) ε ｅ（ｉ，ｍ） : Elastic strain occurring in layer i during partial period m hi: layer thickness of layer i (mm).

3. 3. The method according to claim 1, wherein the partial periods constituting the design period are periods measured in calendar months.

4. 3. The prediction method according to claim 1, further comprising the step of determining, by actual measurement or from air temperature data, the average temperature of a partial period of the layer during which the amount of permanent deformation to be determined may be affected by temperature.

5. The step (a) is a step of determining the predicted amount of permanent deformation of the pavement in the depth direction for each layer constituting the asphalt pavement and for each partial period group, which is a group of one or more partial periods having the same assumed layer temperature; 2. The prediction method according to claim 1, wherein the step (i) is a step of adding up the determined permanent deformation amounts for all layers for which the permanent deformation amounts have been determined and for all partial period groups for which the permanent deformation amounts have been determined, and setting the sum as a predicted value for the amount of rutting in the design period.

6. 6. The prediction method according to claim 5, wherein in the step (a), the predicted permanent deformation amount is calculated for each layer and for each partial period group based on the following formula (7): [Equation 2] In the above formula, the meanings of each symbol are as follows: i: Layer number for which permanent deformation is to be calculated (i = 1, 2, 3, etc.) r: Partial period group number for which permanent deformation is to be calculated (r = 1, 2, 3, ...) R （ｉ，ｒ） : Permanent deformation predicted for layer i in sub-period group r Tir: Deemed layer temperature in the sub-period group r of layer i α （ｉ，Ｔｉｒ） , β （ｉ，Ｔｉｒ） : material constant of layer i at assumed layer temperature Tir N ｒ : Number of passing wheels expected in partial period group r (times) ε ｅ（ｉ，ｒ） : Elastic strain occurring in layer i in sub-period group r hi: layer thickness of layer i (mm).

7. The step (a) is a step of calculating the predicted permanent deformation of the pavement in the depth direction for each layer constituting the asphalt pavement and for each temperature condition group, which is a group of one or more partial periods in which the assumed layer temperature is the same for all corresponding layers; 2. The prediction method according to claim 1, wherein the step (i) is a step of adding up the determined permanent deformation amounts for all layers for which the permanent deformation amounts have been determined and for all temperature condition groups for which the permanent deformation amounts have been determined, and setting the sum as a predicted value for the amount of rutting during the design period.

8. 8. The method according to claim 7, wherein the predicted permanent deformation is calculated for each temperature condition group for all layers for which the permanent deformation is calculated, based on the following formula (10): [Equation 3] In the above formula, i: Layer number for which permanent deformation is to be calculated (i = 1, 2, 3, etc.) n: total number of layers for which permanent deformation is to be calculated p: temperature condition group number (r=1, 2, 3...) Rp: The sum of the predicted permanent deformation amounts for all layers in all partial periods belonging to the temperature condition group p α （ｉ，ｐ） , β （ｉ，ｐ） : Material constant of layer i in all partial periods belonging to temperature condition group p N: Total number of passes expected during the design period (times) gamma ｐ : The proportion (%) of the time period that all partial periods belonging to the temperature condition group p occupy in the design period ε ｅ（ｉ，ｐ） : Elastic strain occurring in layer i during a partial period belonging to temperature condition group p hi: layer thickness of layer i (mm).

9. 9. The method according to claim 8, wherein the predicted permanent deformation amount is calculated based on the following formula (11): [Equation 4] In the above formula, R: Predicted permanent deformation s: total number of temperature condition groups.

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