Experimental Study on Interface Model of Asphalt Pavement under Vertical Load

Round 1

Reviewer 1 Report

I have read this paper throughout and give my comments in the attached file. Please give point-to-point response in the next version. In my opinion, English should be improved and please give the English editing certificate to me, thanks. 

Comments for author File: Comments.pdf

Author Response

Response to reviewer #1

I have read this paper throughout and give my comments in the attached file. Please give point-to-point response in the next version. In my opinion, English should be improved and please give the English editing certificate to me, thanks.

Reply: Thank the reviewer for this comment. The original manuscript has been carefully revised to improve readability by a native speaker and related certificate is given below.

However, the other comments of the reviewer #1 are not found in the attached file.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper demonstrates good research in the empirical investigation of the interface model under vertical load on the pavement surface layer. The following minor changes are suggested:

1. English is something that can be improved.

2. All testing methods should also refer to international standards such as AASHTO or ASTM, showing the international testing references adopted other than using Chinese standards. See Table 1 to Table 6.

3. What is the basis for test temperatures of -10, 0, 25, and 50 degrees C? Is there any empirical argument that the author determines the temperature, or is it just an assumption that describes the temperature conditions in the four seasons?

4. Provide a scientific argument regarding the use of pavement material in this study (Page: 6, Section 2.4).

5. To what extent do the adhesion properties of viscosity-level oils A and B affect the stiffness of the pavement material under a given vertical load?

Author Response

Response to reviewer #2

This paper demonstrates good research in the empirical investigation of the interface model under vertical load on the pavement surface layer. The following minor changes are suggested:

1. English is something that can be improved.

Reply: Thank you. The original manuscript has been carefully revised to improve readability by a native speaker and related certificate is given below:

 

2. All testing methods should also refer to international standards such as AASHTO or ASTM, showing the international testing references adopted other than using Chinese standards. See Table 1 to Table 6.

Reply: Thank the reviewer for this comment. The main purpose of this paper is to solve the problem of interlayer slip and contact existing in China, and the relevant experiment were conducted to obtain the parameter optimization value of mixture structure. The follow research will consider the comparative analysis of test data under different international standards.

 

3. What is the basis for test temperatures of -10, 0, 25, and 50 degrees C? Is there any empirical argument that the author determines the temperature, or is it just an assumption that describes the temperature conditions in the four seasons?

Reply: Thank the reviewer for this comment. It mainly considers the common temperature of asphalt and asphalt mixture test specifications in China, and reflects the asphalt mixture temperature of pavement under the conditions of low temperature, 0-degree, room temperature and high temperature.

 

4. Provide a scientific argument regarding the use of pavement material in this study (Page: 6, Section 2.4).

Reply: Thank the reviewer for this comment. Considering the characteristics of mixture types commonly used in asphalt pavement and cement stabilization base in practical construction. AC is adopted in the surface material, and cement stabilized gravel is adopted in the base material. If the surface layer is three-layer, the upper layer AC-13, the middle layer AC-20, and the lower layer AC-25 are generally selected; If the surface layer is two-layer, the upper layer AC-13 and the lower layer AC-20 are generally selected. In addition, this study considers the influence of raw material of region and grading range specified in the code, and combined with the experimental results of mixing ratio design in the laboratory to obtain the specific situation of the mixture selection which can meet the specification requirements.

 

5. To what extent do the adhesion properties of viscosity-level oils A and B affect the stiffness of the pavement material under a given vertical load?

Reply: Thank the reviewer for this comment. First, the average adhesion coefficient of oil A and B decreases 27.3% and 23.5% with the temperature increase from -10 ℃ to 0 ℃, respectively. When the temperature rise to 25 ℃, the average adhesion coefficient of oil A and B decreases 65.7% and 72%, respectively. While the temperature keep rise to 50 ℃, the average adhesion coefficient of two oil have no obvious change. It can be concluded that the type of oil has obvious influence for the interlayer bonding behavior with relative lower temperature. Second, the amount of spread corresponding to the maximum adhesion coefficient of oil A and oil B is 0.8 kg/m² and 0.6 kg/m² in the different temperature, respectively. It can be obtained that the bonding behavior reaches the optimum with the amount of spread 0.6~ 0.8 kg/m² in different temperature.

Reviewer 3 Report

General comments:

1.       Overall, more references should be provided to support the manuscript.

2.       Overall, consider parentheses () for the units of X-Y axes of each graph.

3.       Please, be consistent with the space between magnitudes and their respective units in:

o Subsections:  2.2.; 2.2. Specimen size (100mm); 2.2. Shear rate (5mm/min); 4.1; 4.2; 5.1; 5.2;5.3.

o Tables: 1, 2, 3, 7, 8, 9, 10, 11.

4.       The work could visually improve if better images are provided for figures showing asphalt specimens or testing equipment. As an example, it would help a uniform background as well as a reference scale for images showing asphalt specimens.

 

Comment for sections:

1.       Introduction

1.1. In the phrase” Based on Goodman model, Uzan et al. [6] used BISAR to analyze and calculate the stress and strain of pavement structure” BISAR should be defined (e.g., BISAR software?).

2.       Subsection 2.1

2.1. Please, define the SGC (Superpave Gyratory Compactor?) abbreviation in subsection 2.1.

2.2. Please, use better images for Figures 1 to 4, to show the equipment described. Also, consider grouping these figures in a single one using a single caption, e.g., Figure 1(a), (b), (c), (d).

3.       Subsection 3.1

3.1. Please, add units to the Δμ parameter in the description for Eq 1.

3.2. For consistency, please check font size and style for Eq 2. It seems to be different to Eq 1.

4.       Subsection 4.1

4.1. Figures 11, 12, 13, and 14 should be grouped in a single figure as exemplified in comment 2.2.

4.2. Figures 15, 16, 17, and 18 should be grouped in a single figure as exemplified in comment 2.2.

5.       Subsection 5.1

5.1. Figure 19. Legend does not describe each of the curves. Also, units should be properly written, considering a space between magnitude and unit (0 kg/m² instead of 0Kg/m2).

5.2. Figure 20. Check the y-axis “Ahesion coefficient”. Also, the legend does not properly describe each of the curves.

6.       Subsection 5.2

6.1. Figure 21. Describe better the caption information associated with this figure. Also, the legend does not properly describe each of the curves (e.g., the symbol for 50°C is missing). Some fitting equations are difficult to read since they are not properly placed in the graph.

6.2. Figure 22. R² is missing for each one of the fitting equations. Describe better the caption information associated with this figure.

6.3. Page 14. Check if the reference to the figures in the phrase “It can be seen from Figures 16 and 17 that:” is right.

6.4. Page 15. Check the reference to the figures in the phrase “Therefore, there is an optimal spreading amount of adhesive oil. By fitting the variation trend of Figures 23 and 24…”. These figures are not present in the manuscript.

6.5. Figures 25 and 26 should be grouped in a single figure as exemplified in comment 2.2.

 

7.       Subsection 5.3

7.1. Improve the legend description for figures 27, 28, 29,  and 30. They are confusing.

7.2. Figure 30. Please, be consistent with the type of font chosen for the X-axis.

8.       Subsection 5.4

8.1. Figure 31. Describe better the caption information associated with this figure.

8.2. Figure 32. Describe better the caption information associated with this figure. Also, the legend does not properly describe each of the curves.

8.3. Why the test carried out in this section were focused on oil A? The manuscript should be clearer in concluding if oil A is more appropriate than oil B for these tests.

9.       References

9.1.      Please, provide references in the correct format.

Author Response

Response to reviewer #3

1. Overall, more references should be provided to support the manuscript.

Reply: Thank the reviewer for this comment. The more references have been added in revised manuscript.

 

2. Overall, consider parentheses () for the units of X-Y axes of each graph.

Reply: Thank the reviewer for this comment. The units of X-Y axes of each graph have been modified.

 

3. Please, be consistent with the space between magnitudes and their respective units in:

Subsections:2.2.;2.2. Specimen size (100mm); 2.2. Shear rate (5mm/min); 4.1; 4.2; 5.1; 5.2;5.3.

Tables: 1, 2, 3, 7, 8, 9, 10, 11.

Reply: Thank the reviewer for this comment. The space between magnitudes and units have been modified in Subsections and Tables.

 

4. The work could visually improve if better images are provided for figures showing asphalt specimens or testing equipment. As an example, it would help a uniform background as well as a reference scale for images showing asphalt specimens.

Reply: Thank the reviewer for the suggestion. Due to the lack of consideration in the experiment, the figures do not have a uniform background. This issue will be paid more attention to in the subsequent research.

Comment for sections:

1. Introduction

1.1. In the phrase” Based on Goodman model, Uzan et al. [6] used BISAR to analyze and calculate the stress and strain of pavement structure” BISAR should be defined (e.g., BISAR software?).

Reply: Thank the reviewer for this comment. BISAR is a finite element software which has been defined in revised manuscript.

 

2. Subsection 2.1

2.1. Please, define the SGC (Superpave Gyratory Compactor?) abbreviation in subsection 2.1.

2.2. Please, use better images for Figures 1 to 4, to show the equipment described. Also, consider grouping these figures in a single one using a single caption, e.g., Figure 1(a), (b), (c), (d).

Reply: Thank the reviewer for this comment. SGC is the Superpave Gyratory Compactor which has been modified in revised manuscript.

Due to the lack of consideration in the experiment, the figures do not have good quality. This issue will be paid more attention to in the subsequent research. These figures have been modified in a single one using a single caption.

 

3. Subsection 3.1

3.1. Please, add units to the Δμ parameter in the description for Eq 1.

3.2. For consistency, please check font size and style for Eq 2. It seems to be different to Eq 1.

Reply: Thank the reviewer for this comment. The unites of Δμ parameter has been added in the description for Eq 1. The front size and style of Eq 2 has been revised as same as Eq 1 in revised manuscript.

 

4. Subsection 4.1

4.1. Figures 11, 12, 13, and 14 should be grouped in a single figure as exemplified in comment 2.2.

4.2. Figures 15, 16, 17, and 18 should be grouped in a single figure as exemplified in comment 2.2.

Reply: Thank the reviewer for this comment. These figures have been grouped in a single figure respectively in revised manuscript.

 

5. Subsection 5.1

5.1. Figure 19. Legend does not describe each of the curves. Also, units should be properly written, considering a space between magnitude and unit (0 kg/m² instead of 0Kg/m2).

5.2. Figure 20. Check the y-axis “Ahesion coefficient”. Also, the legend does not properly describe each of the curves.

Reply: Thank the reviewer for this comment. These units and legend of figures have been modified in revised manuscript.

 

6. Subsection 5.2

6.1. Figure 21. Describe better the caption information associated with this figure. Also, the legend does not properly describe each of the curves (e.g., the symbol for 50°C is missing). Some fitting equations are difficult to read since they are not properly placed in the graph.

6.2. Figure 22. R² is missing for each one of the fitting equations. Describe better the caption information associated with this figure.

6.3. Page 14. Check if the reference to the figures in the phrase “It can be seen from Figures 16 and 17 that:” is right.

6.4. Page 15. Check the reference to the figures in the phrase “Therefore, there is an optimal spreading amount of adhesive oil. By fitting the variation trend of Figures 23 and 24…”. These figures are not present in the manuscript.

6.5. Figures 25 and 26 should be grouped in a single figure as exemplified in comment 2.2.

Reply: Thank the reviewer for this comment. The symbol for 50°C has been added. The caption of Figure 21 and 22 have been modified better, and the reference to the figures have been check and modified, and the Figure 25 and 26 have been grouped in a single figure in revised manuscript.

 

7. Subsection 5.3

7.1. Improve the legend description for figures 27, 28, 29, and 30. They are confusing.

7.2. Figure 30. Please, be consistent with the type of font chosen for the X-axis.

Reply: Thank the reviewer for this comment. At the different temperature, viscosity-level A and B have corresponding adhesion coefficients under different amount of spread, and polynomial curve is fitted according to the measured values respectively. The above descriptions have been added in revised manuscript and the type of front chosen for the X-axis in Figure 30 has been modified.

 

8. Subsection 5.4

8.1. Figure 31. Describe better the caption information associated with this figure.

8.2. Figure 32. Describe better the caption information associated with this figure. Also, the legend does not properly describe each of the curves.

8.3. Why the test carried out in this section were focused on oil A? The manuscript should be clearer in concluding if oil A is more appropriate than oil B for these tests.

Reply: Thank the reviewer for this comment. The caption information of Figure 31 and 32 have been modified better, and the legend of Figure 32 has been adjusted in revised manuscript.

It can be found in subsection 5.3, the performance of oil A is better than that of oil B at different, and this part will be highlighted in the conclusion.

 

9. References

9.1. Please, provide references in the correct format.

Reply: Thank the reviewer for this comment. The format of references has been modified in revised manuscript.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

1. My comments were rewritten in the attachment file. I don't know why authors didn't find it.

2. I don't find grammar improvements by comparing two versions of articles. 

Comments for author File: Comments.pdf

Author Response

Response to reviewer #1

1. The scientific novelty of this paper may be not adequate, as there are not enough introductions in the first section. I cannot obtain the research urgency.

Reply: Thank you.

The scientific novelty of this paper has been restated in the revised manuscript as follows:

To sum up, the simulation of pavement field about interlayer contact is not perfect enough. A lot of researches on interlayer stress and theoretical models have been done, but some issues remain unsolved. For example, the study of interlayer interface based on numerical simulation only consider the friction between layers, and the intercalation between aggregates is not been considered, which will inevitably affect the mechanical response of the pavement structure. Additionally, few researchers consider the effect of vertical load on the stress state of interlayer interface when developing interlayer shear molds. Even if considered, the vertical load is a constant simulation value, which is far from the actual value. The interfacial characteristics of asphalt layers under different vertical load conditions, different spraying amounts and different temperatures are rarely studied. Therefore, it is necessary to perform researches on different types of interlayer contact under vertical load.

In view of the above, the investigation for changeable rule of interlayer interface of asphalt pavement under vertical load condition based on Goodman model is performed in this paper. The authors choose the experiment temperature, gradation, amount of viscosity-level oil, type of viscosity-level oil and vertical compressive stress as test parameters, and the an interlayer direct shear tests are conducted by the universal testing machine (UTM) and self-modified test fixture. Based on the experimental and theoretical analysis, the basic variation rules of the interlayer characteristics of the mixture under different conditions are obtained. Additionally, the optimal spraying amounts of the interlayer viscous oil between the upper and middle layers, the middle and lower layers, the lower layer and the cement stabilized base layer is recommended.

Please see the lines 71 to 89 in the revised manuscript.

 

2. I suggest the English in this paper should be improved by a native English speaker and an English editing certificate can be added for a supplement material.

Reply: Thank you.

Thank the reviewer for this comment. The original manuscript has been carefully revised to improve readability by a native speaker and related certificate is given below.

 

3. Add line numbers may help to read the paper, and this is the writing rule of the MDPI journals.

Reply: Thank you.

The line numbers have been added in the revised manuscript.

 

4. I suggest a primary achievement summary should be added in the abstract.

Reply: Thank you.

Abstract has been rewritten in the revised manuscript as follows:

The layered asphalt pavement makes the interlayer contact more complicated. In order to further understand the characteristics of interlayer interface of asphalt pavement under vehicle load, this paper analyzes the change rule of interlayer interface of asphalt pavement under vertical load condition based on Goodman model. According to the characteristics of asphalt pavement, the experiment temperature, gradation, amount of viscosity-level oil, type of viscosity-level oil and vertical compressive stress are taken as parameters, and the universal testing machine (UTM) and self-modified test fixture are used to carry out the direct interlayer shear test. Experimental results shows that the vertical load has a significant effect on the characteristics of interlayer interface. With the increase of the vertical load, the maximum bonding coefficient will change greatly. Additionally, when the vertical load is constant, the temperature and spreading amount of viscosity-level oil have a great influence on the interlayer bonding state. With the increase of the temperature, the maximum bonding coefficient decreases. The adhesion coefficient increases first and then decreases with the increase of the spreading amount. The best spreading amounts of oil between the upper and middle layers, the middle and lower layers, and the lower layer and cement stabilized base layer under different vertical load conditions are recommended. This study will offer an important guidance in pavement structure.

Please see the lines 11 to 25 in the revised manuscript.

 

5. What is the commonly used international standard? Just a Chinese code may be not readable for international readers.

Reply: Thank the reviewer for this comment. The main purpose of this paper is to solve the problem of interlayer slip and contact existing in China, and the relevant experiment were conducted to obtain the parameter optimization value of mixture structure. The follow research will consider the comparative analysis of test data under different international standards.

 

6. Are there any newly references in terms of this paper? 1968-2013，References among 2013-2022 should be considered to add in the introduction section. besides, I suggest some more references should be added, as there are only 11 articles or codes in this version. It's inadequate.

Reply: Thank you.

Some related and newly references have been added in the revised manuscript as follows:

• Ning Z. F.. Analysis and Evaluation of Interlayer Combination of Asphalt Pavement. Hunan University, 2012.
• Fang H., Luo H., Zhu H.. The feasibility of continuous construction of the base and asphalt layers of asphalt pavement to solve the problem of reflective cracks. Construction & Building Materials, 2016, 119(aug.30):80-88.
• Specifications for Design of Highway Asphalt Pavement, JTG D50-2017. People's Communications Publishing House, 2017.
• Technical Specification for construction of Highway Asphalt Pavement,JTG F40-2004,People's Communications Publishing House, 2004.
• Liu H. M., Song X. D., Huo Y. G., et al. Development and application of shear stress measuring instrument between layers of asphalt pavement. Journal of Xian University of Science & Technology, 2014.
• Cho S. H.. Evaluation of Interfacial Stress Distribution and Bond Strength between Asphalt Pavement Layers. North Carolina State University, 2015.
• Livneh M., Shklarsky E.. The bearing capacity of asphalt concrete surfacing. Proc. 1st: Int. Conf. on the Structural Design of Asphalt Pavements, Univ. of Michigan, Ann Arbor, Mich., 1962. 345-353.
• Goodman R. E., Brekke T. L., A model for the mechanics of jointed rock. Journal of Mechanics &Foundations Div, 1968, 94(3):637-659.
• Uzan J., Livneh M., Eshed Y.. Investigation of adhesion properties between asphalt concrete layers. Asphalt Paving Technologists, 1978, (4): 495-521.
• Romanoschi S. A., Metcalf J. B.. The characterization of asphalt concrete layer interfaces. Ninth International Conference on Asphalt Pavements, 2002.
• Mariana R., Kruntchev A., Andrew C.. Effect of Bond Condition on Flexible Pavement Performance. Journal of Transportation Engineering, 2005, 130 (11): 880-888.
• Leng Z., Ozer H., Al-Qadi H. I. Carpenter, H.S. Interface bonding between hot-mix asphalt and various Portland cement concrete surfaces. Transportation Research Record. 2057, Transportation research, 2008, 46-53.
• Kruntcheva M. R., Collop A. C., Thom N H. Properties of Asphalt Concrete Layer Interfaces. American Society of Civil Engineers, 2013, 18(3):467-471.
• Hu X. D., Walubita Lubinda F.. Effects of Layer Interfacial Bonding Conditions on the Mechanistic Responses in Asphalt Pavements, 2010: 28-36.
• Wang S. Y.. Study on Test Method of Interlayer Shear Strength of Indoor Asphalt Concrete Pavement. Highway, 2010.2 (2): 144-147.
• Liu F. Q.. Influence of Interlaminar Shear Stress among Layers of Asphalt Pavement with Semi-rigid Base on Its Distortion Energy. Journal of Lanzhou Institute of Technology, 2016.

 

7. What are the differences between you and them in terms of the test methods and results.

Reply: Thank you.

The scientific novelty of this paper has been restated in the revised manuscript as follows:

To sum up, the simulation of pavement field about interlayer contact is not perfect enough. A lot of researches on interlayer stress and theoretical models have been done, but some issues remain unsolved. For example, the study of interlayer interface based on numerical simulation only consider the friction between layers, and the intercalation between aggregates is not been considered, which will inevitably affect the mechanical response of the pavement structure. Additionally, few researchers consider the effect of vertical load on the stress state of interlayer interface when developing interlayer shear molds. Even if considered, the vertical load is a constant simulation value, which is far from the actual value. The interfacial characteristics of asphalt layers under different vertical load conditions, different spraying amounts and different temperatures are rarely studied. Therefore, it is necessary to perform researches on different types of interlayer contact under vertical load.

In view of the above, the investigation for changeable rule of interlayer interface of asphalt pavement under vertical load condition based on Goodman model is performed in this paper. The authors choose the experiment temperature, gradation, amount of viscosity-level oil, type of viscosity-level oil and vertical compressive stress as test parameters, and the an interlayer direct shear tests are conducted by the universal testing machine (UTM) and self-modified test fixture. Based on the experimental and theoretical analysis, the basic variation rules of the interlayer characteristics of the mixture under different conditions are obtained. Additionally, the optimal spraying amounts of the interlayer viscous oil between the upper and middle layers, the middle and lower layers, the lower layer and the cement stabilized base layer is recommended.

Please see the lines 71 to 89 in the revised manuscript.

 

8. A table may be more clear to readers. please consider this suggestion.

Reply: Thank you.

The main technical parameters of UTM-100 are shown in Table 1.

Table 1. The main technical parameters of UTM-100

Technical indicators	Unit	Value or range
Test temperature range	℃	-20 ~ 80
Maximum vertical load	kN	100
Pressure sensor accuracy	kN	0.01
Displacement sensitivity	mm	0.001
Loading rate	Adjustable
Data acquisition	Automatic

Please see the lines 97 to 98 in the revised manuscript.

 

9. A similar constraint condition related to the actual engineering? Please explain for this.

Reply: Thank you.

The related contents have been added in the revised manuscript as follows:

It is worth noting that the specimen was mainly applied the horizontal interlayer shear action under vertical load. This is a simplification of the actual engineering, but not exactly identical.

Please see the lines 150 to 152 in the revised manuscript.

 

10. Figures 6 and 7 can be summarized in one figure and it can be compared. Besides, the selection reason of the parameter K should be strengthened.

Reply: Thank you.

The related contents have been added in the revised manuscript as follows:

It can be seen from Figure 3 that with the increase of relative shear displacement, the shear load on the interlayer interface increases at first, and then decreases gradually to a stable state. According to this phenomenon, we can know that when the interlaminar shear load increases to the ultimate shear strength of the specimen, the interlayer structure is damaged. However, residual shear strength still exists between the layers after interlayer failure. Figure 4 shows that the interlayer bonding coefficient increases to a limit value at first, and then decreases and tends to be stable. Now most researchers think that the stress-strain curve of the pavement interlayer specimen before failure rises in a straight line at the initial stage. The slope of the straight line is defined as the initial interlayer bonding coefficient . With the rise of the curve, the specimen will reach the ultimate shear strength. The interlayer bonding coefficient at this time is considered to be . When the value of  changes from  to , it is the stage that the pavement interlayer interface changes from the initial viscous state to viscous failure. Therefore, the average value of  and  is often used to describe the bonding state of the pavement interlayer structure. However, a large number of repeated experiments applied the vertical load are carried out in this study and there are obvious difference between  and . Therefore, the author use the ultimate bonding coefficient  to describe the bonding state of the pavement interlayer structure. It may be more accurate and conforms the conclusion come from the Goodman model. If the value of  is larger, it indicates that the bonding performance of interlayer interface is better and tends to be completely continuous; If the value of  is smaller, it indicates that the bonding performance of interlayer interface is worse and tends to slide.

Please see the lines 190 to 208 in the revised manuscript.

Author Response File: Author Response.pdf

Reviewer 3 Report

Thanks to the authors for responding each comment and suggestion. The following minor revision is suggested:

- Please, verify that figures are correctly numbered and cited in the revised manuscript. Figure 16 should be numbered and cited as figure 15. Please, correct this in the revised manuscript.

Author Response

Response to reviewer #3

Thanks to the authors for responding each comment and suggestion. The following minor revision is suggested:

Please, verify that figures are correctly numbered and cited in the revised manuscript. Figure 16 should be numbered and cited as figure 15. Please, correct this in the revised manuscript.

Reply: Thank you.

The related contents have been corrected in the revised manuscript.

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

Some concerns are not addressed. 

1. Line number is not found.

2. Passive tense may be more suitable for English writing for these contents. 

To sum up, the simulation of pavement field about interlayer contact is not perfect enough. A lot of researches on interlayer stress and theoretical models have been done, but some issues remain unsolved. For example, the study of interlayer interface based on numerical simulation only consider the friction between layers, and the intercalation be-tween aggregates is not been considered, which will inevitably affect the mechanical re-sponse of the pavement structure. Additionally, few researchers consider the effect of ver-tical load on the stress state of interlayer interface when developing interlayer shear molds. Even if considered, the vertical load is a constant simulation value, which is far from the actual value. The interfacial characteristics of asphalt layers under different ver-tical load conditions, different spraying amounts and different temperatures are rarely studied. Therefore, it is necessary to perform researches on different types of interlayer contact under vertical load.

In view of the above, the investigation for changeable rule of interlayer interface of asphalt pavement under vertical load condition based on Goodman model is performed in this paper. The authors choose the experiment temperature, gradation, amount of vis-cosity-level oil, type of viscosity-level oil and vertical compressive stress as test parame-ters, and the an interlayer direct shear tests are conducted by the universal testing machine (UTM) and self-modified test fixture. Based on the experimental and theoretical analysis, the basic variation rules of the interlayer characteristics of the mixture under different conditions are obtained.

3.  Is there verification of the simplification of the actual engineering? Or just a theoretical mechanical analysis is better.

Author Response

Response to reviewer #1

1. Line number is not found.

Reply: Thank you.

Line number has been added in the revised manuscript.

2. Passive tense may be more suitable for English writing for these contents.

Reply: Thank you for your suggestion.

The related contents have been rewritten in the revised manuscript as follows:

To sum up, the simulation of pavement field about interlayer contact is not perfect enough. A lot of researches on interlayer stress and theoretical models have been done, but some issues remain unsolved. For example, the study of interlayer interface based on numerical simulation only consider the friction between layers, and the intercalation between aggregates is not been considered, which will inevitably affect the mechanical response of the pavement structure. Additionally, the effect of vertical load on the stress state of interlayer interface is rarely considered when interlayer shear molds are developed. Even if considered, the vertical load is a constant simulation value, which is far from the actual value. The interfacial characteristics of asphalt layers under different vertical load conditions, different spraying amounts and different temperatures are also rarely studied. Therefore, it is necessary to perform researches on different types of interlayer contact under vertical load.

In view of the above, the investigation for changeable rule of interlayer interface of asphalt pavement under vertical load condition based on Goodman model is performed in this paper. The experiment temperature, gradation, amount of viscosity-level oil, type of viscosity-level oil and vertical compressive stress are chose as the main test parameters, and an interlayer direct shear tests are conducted by the universal testing machine (UTM) and self-modified test fixture. Based on the experimental and theoretical analysis, the basic variation rules of the interlayer characteristics of the mixture under different conditions are obtained. Additionally, the optimal spraying amounts of the interlayer viscous oil between the upper and middle layers, the middle and lower layers, the lower layer and the cement stabilized base layer is recommended.

Please see the lines 71 to 89 in the revised manuscript.

 

3. Is there verification of the simplification of the actual engineering? Or just a theoretical mechanical analysis is better.

Reply: Thank you for your consideration.

We very much agree with your suggestion. But this part of the content has not been carried out.

In previous studies, the effect of vertical load on the stress state of interlayer interface is rarely considered when interlayer shear molds are developed. In order to further understand the characteristics of interlayer interface of asphalt pavement under vehicle load, this paper analyzes the change rule of interlayer interface of asphalt pavement under vertical load condition based on Goodman model. Therefore, the experimental specimens were mainly applied the horizontal interlayer shear action under vertical load. This is a simplification of the actual engineering, but not exactly identical. This is a great progress compared with previous studies. Of course, in actual engineering, there are lateral constraints between pavement layers, which will be done in the follow-up research.