Reference no: EM133015634

300984 Pavement Materials and Design

Lab: Mechanistic design of flexible pavement

Aims

1.1 Understand the mechanistic procedures for designing a flexible pavement
1.2 Use of software CIRCLY to facilitate the design of flexible pavements

Introduction

Mechanistic design of flexible pavements is covered in Austroads "Guide to Pavement Technology: Part 2: Pavement Structural Design". This approach is based on small strain linear elastic analysis supplemented by empirical models defining the performance of different layers of the pavement structure. Today's lab will require the use of CIRCLY to carry out the mechanistic design of flexible pavements.

Method

This lab consists of two parts. First part is for you to get familiarise with the software and the second part is for you to design your own pavement for a real world application.

Part 1

Run CIRCLY for the 3 design cases given in Appendix K of Austroads "Pavement Technology Part 2: Pavement Structural Design" guide. These examples are explained in the "Appendix K Examples" file uploaded on vUWS. These cases are for:

1. Sprayed seal surfaced unbound granular pavement
2. Asphalt pavement containing a cemented material subbase
3. Full depth asphalt pavement

4.1.1. Part 1: Sprayed seal surfaced unbound granular pavement

Step 1: Start CIRCLYv7.0 to open the interface shown below. You will work this program by progressing from icon on left to icon on right.

Step 2: Create a Jobname for your work by pressing the "New" icon on the menu. Enter the jobname. Also check whether the design method is set to "Austroad pavement design".

Step 3: Click on "TLD" (Traffic Load Distribution) under state select "Example" to assign a traffic load distribution specified in appendix K examples with a damage index ESA/HVAG) 0.7.

For real applications you can select stored TLD data as in below figure (NSW - 283 - Pacific Hwy - Brunswick Heads).

Step 4: Click on "TLD" (Traffic Load Distribution) under Job Details tree. Refer to the "Appendix K Examples" file and enter the design NDT (Design Traffic) for this example.

Step 5: Click on "Layered System" under Job Details tree or the "Layers" icon. A "Layers" window will open on the right to display the existing cases of pavement layers (structure) stored in the database. A smaller auxiliary window displaying the pavement structure (layer number, layer material and layer thickness) of the case indicated by the pointer will also appear below the main window. You can see the 3 examples in appendix K as highlighted in the below figure. Also when you click on different example you can see the pavement components underneath.

By default the pointer in the main window and in the auxiliary window will point to the first row. Click on the "Austroads 2004 - Example 1 - Unbound Granular Pavement" case. In the auxiliary window, the pavement structure of this case will appear.

You may create a new pavement structure by clicking on the "New" button at the right of the window. However, for Part 1, you will use existing example structures which are already in CIRCLY.

Note that CIRCLY handles most of the input data using a relational database approach. This is designed to eliminate re-entry of data for design loads and material properties. The relational

database approach gives maximum flexibility in data preparation.

Step 6: Click on "Project Reliability" under Job Details tree. Enter the desired project reliability for this example (refer appendix K for the value).

Step 7: Click on the "Austroads 2004 - Example 1 - Unbound Granular Pavement" case. In the auxiliary window, the pavement structure of this case will appear.

Step 8: Click on the "Granular, E = 500MPa" in the subsidiary window. A "Material Properties" window will appear. You can select and change the material properties for the pavement layer from the "Material Properties" database. As new materials are being created (through the "Materials" icon), the properties are stored in the database to be used until deleted.

4.1.1. Part 1: Sprayed seal surfaced unbound granular pavement

Step 1: Start CIRCLYv7.0 to open the interface shown below. You will work this program by progressing from icon on left to icon on right.

Step 2: Create a Jobname for your work by pressing the "New" icon on the menu. Enter the jobname. Also check whether the design method is set to "Austroad pavement design".

Step 3: Click on "TLD" (Traffic Load Distribution) under state select "Example" to assign a traffic load distribution specified in appendix K examples with a damage index ESA/HVAG) 0.7.

For real applications you can select stored TLD data as in below figure (NSW - 283 - Pacific Hwy - Brunswick Heads).

Step 4: Click on "TLD" (Traffic Load Distribution) under Job Details tree. Refer to the "Appendix K Examples" file and enter the design NDT (Design Traffic) for this example.

Step 5: Click on "Layered System" under Job Details tree or the "Layers" icon. A "Layers" window will open on the right to display the existing cases of pavement layers (structure) stored in the database. A smaller auxiliary window displaying the pavement structure (layer number, layer material and layer thickness) of the case indicated by the pointer will also appear below the main window. You can see the 3 examples in appendix K as highlighted in the below figure. Also when you click on different example you can see the pavement components underneath.

By default the pointer in the main window and in the auxiliary window will point to the first row. Click on the "Austroads 2004 - Example 1 - Unbound Granular Pavement" case. In the auxiliary window, the pavement structure of this case will appear.

You may create a new pavement structure by clicking on the "New" button at the right of the window. However, for Part 1, you will use existing example structures which are already in CIRCLY.

Note that CIRCLY handles most of the input data using a relational database approach. This is designed to eliminate re-entry of data for design loads and material properties. The relational

database approach gives maximum flexibility in data preparation.

Step 6: Click on "Project Reliability" under Job Details tree. Enter the desired project reliability for this example (refer appendix K for the value).

Step 7: Click on the "Austroads 2004 - Example 1 - Unbound Granular Pavement" case. In the auxiliary window, the pavement structure of this case will appear.

Step 8: Click on the "Granular, E = 500MPa" in the subsidiary window. A "Material Properties" window will appear. You can select and change the material properties for the pavement layer from the "Material Properties" database. As new materials are being created (through the "Materials" icon), the properties are stored in the database to be used until deleted.

Close the "Materials Properties" window as the correct material properties have already been selected for this example.

Step 9: Click on "Materials" icon. The "Materials Properties" window will appear as the main window on the right. In the "Material Type" pull down menu, a selection of material type is available. You may add or delete material properties within a particular material type. Make sure the material properties are entered for the right material type.

For this case, it may be noted that the granular material is from the "Unbound Granular (Austroads 2004 sub-layering)" material type. CIRCLY will therefore perform the sub-layering within the program if this material type is chosen.
Since no new material is required to be added, proceed to the next step.

Step 10: The layers, material properties and traffic design data for the "Sprayed seal surfaced unbound granular pavement" are now ready for analysis by CIRCLY. Click on the "Analyse" icon.

CIRCLY will analyse the pavement layers and display the damage factor, CDF, corresponding to each pavement layer, where appropriate, in the right window. The damage factor in this case is the ratio of the design traffic to the allowable traffic in the pavement layer.

(Pavement to be accepted, the allowable traffic for each layer need to be higher that the design traffic i.e CDF should be less than 1. If the CDF is more than 1, we need to re-design the pavement. We can change the material (different modules) and/or the layer thickness)
Note the CDF value for the subgrade computed by CIRCLY and compare it with the value calculated from the example. This should be reported in the report.

Step 11: Click on the "Print" icon and view the Job Summary file. At the end of the file, the critical strain computed by CIRCLY for the subgrade is reported. Compare and report the critical strain from CIRCLY and from the example published in Austroads. Save the Job Summary file and submit it as an attachment to your lab report.

4.1.2. Part 1: Asphalt pavement containing a cemented material subbase (pre-cracking)

Step 1: Click on the "Layers" icon. Point to "Austroads 2004 - Example 2 - Asphalt Pavement containing Cemented Layer" by clicking on it. The pavement structure of this case will appear in the subsidiary window below.

Step 2: Check the pavement structure data in the subsidiary window to make sure it corresponds to the data in the "Appendix K Examples" file. If necessary, amend the data to the original values.

Step 3: Click on the "Analyse" icon to analyse this case. At the end of the analysis, CIRCLY will display the CDF for the pavement layers.
Note the CDF values for the different damages in the pavement layers computed by CIRCLY and compare with the values calculated from the example. These should be reported in the report.

Save the Job Summary file and submit it as an attachment to your lab report. Compare and report the critical strains from CIRCLY and from the example published in Austroads.

Step 4: Check if the pavement structure is unacceptable because one or more of the CDF values is equal or greater than 1 (this will be highlighted in red). If a pavement is unacceptable, you may use CIRCLY to re-design the thickness of any pavement layer by pointing to any layer and ticking the "Design thickness of layer highlighted below" box in the "Analyse" window.

Click "Analyse" for CIRCLY to re-evaluate the design thickness and produce a thickness value that is acceptable.

4.1.3. Part 1: Asphalt pavement containing a cemented material subbase (post-tcracking)

Step 1: Click on the "Layers" icon. Point to "Austroads 2004 - Example 2 - Asphalt Pavement containing Cemented Layer" by clicking on it. If the pavement structure for this case has been amended, return the structure data to the original values.

Step 2: Click on the "Layers" icon. Point to "Austroads 2004 - Example 2 - Post-cracked" case by clicking on it. The pavement structure of this case will appear in the subsidiary window below.

Step 3: Check the pavement structure data in the subsidiary window to make sure it corresponds to the data in the "Appendix K Examples" file. If necessary, amend the data to the original values.

Step 4: Click on the "Analyse" icon to analyse this case. At the end of the analysis, CIRCLY will display the CDF for the pavement layers.
Note the CDF values for the different damages in the pavement layers computed by CIRCLY and compare with the values calculated from the example. These should be reported in the report.

Save the Job Summary file and submit it as an attachment to your lab report. Compare and report the critical strains from CIRCLY and from the example published in Austroads.

4. 4.1.4. Part 1: Full depth asphalt pavement

Step 1: Click on the "Layers" icon. Point to "Austroads 2004 - Example 3 - Full Depth Asphalt Pavement" by clicking on it. If the pavement structure for this case has been amended, return the structure data to the original values.

Step 3: Check the pavement structure data in the subsidiary window to make sure it corresponds to the data in the "Appendix K Examples" file. If necessary, amend the data to the original values.
Step 4: Click on the "Analyse" icon to analyse this case. At the end of the analysis, CIRCLY will display the CDF for the pavement layers.

4.2. Part 2

In Part 2, use CIRCLY to design a flexible asphalt pavement containing a cemented material subbase for Pacific Highway near Brunswick Heads heading north. The following information is given:

• design traffic is a x 107 HVAG over 30 year period
• subgrade design CBR = b%
• Asphalt modulus size 14 mm mix = 2200 MPa
• Asphalt modulus size 20 mm mix = 2500 MPa
• Desired project reliability = c%

WIM characteristics of the traffic at Pacific Highway near Brunswick Heads towards north may be obtained from stored data in the software or from Table D1 of Austroads guide, and part of the table is given below for easy reference. The only requirement is that the asphalt thickness must be at least 175 mm. Make appropriate assumptions regarding the properties of the other materials of the pavement.

Attachment:- Pavement Materials and Design.rar