Section 8: Pavement Design Reports
Anchor: #i1010527Projects Requiring Pavement Design and Pavement Design Reports
A pavement design and a pavement design report are required for the following projects that are over 500 ft long:
- new location projects (flexible and rigid)
- reconstruction projects (flexible and rigid)
- rehabilitation (2R) projects, where upgrading as defined in Chapter 5 (reconstruction and rehabilitation design criteria) of the Roadway Design Manual is performed
- rehabilitation (3R) projects (flexible and rigid)
- projects that involve removal of water trapped in the pavement structure (underdrains, edge drains, restoration of drainage systems)
- hydraulic cement concrete (rigid) overlays of existing pavements
- hot mix asphalt (HMA) overlays greater than 2 in. thick.
HMA overlays, 2-in. thick and less, are considered a preventative maintenance treatment; therefore, a pavement design report is not required where adequate structural capacity is documented. Considering the significant investment thin overlays represent; these treatments should be taken into account in an overall payment preservation program. An analysis should be performed that substantiates the appropriateness of this maintenance strategy.
The pavement design for special cases will typically be based on engineering judgment, historical performance, district policy, and other guidelines (i.e., this guide, industry guidelines, and research findings). A design report will be required.
The following list provides examples of special cases that require documentation of the criteria and rationale for the strategy selected:
- approaches on a bridge replacement
- addition of shoulders
- detours
- addition of a travel lane
- matching the existing or the adjacent section.
- HMA overlays of rigid pavements. The only “rational” approach generally available to department engineers for designing a HMA overlay to an existing rigid pavement is the AASHTO Overlay procedure (automated in DARWin™). However, this process is highly subjective.
- bonded rigid overlays on rigid pavements
- thin whitetopping of flexible pavements.
For design categories not covered above, contact the district pavement engineer for guidance about recommended design procedures and documentation requirements.
Anchor: #i1010634Pavement Design Report and Other Documentation
A pavement design report is a formal engineering document that presents all analyses, data, policies, and other considerations used to design the structural aspects of a pavement. As a minimum, the design report should include the following:
- Cover sheet showing highway designation, district, county, project CSJ, geographical limits, and signatures of persons involved in the preparation and approval.
- Narrative discussing the overall objective, site particulars (location, facility type, soil conditions and subgrade Texas Triaxial Classification [TTC], drainage considerations), PMIS data analysis/pavement condition surveys, conclusions, and recommended pavement structure. The narrative should include a discussion of the section’s construction and maintenance history, identifying factors that significantly affect pavement performance, and a summary of laboratory tests conducted on any materials extracted from the existing structure.
- If the pavement structure selected is different from the structure recommended by the design procedure, a discussion of the selection process must be included in the report.
- Location map. Maps should be detailed enough to distinguish urban or rural project locations, and the presence of water features such as lakes, streams, etc.
- Soils map of the project area with a brief description of each type of soil located within the project area. Identify any known sulfate deposits.
- Existing and proposed typical sections. For the proposed structure, clearly define the various pavement layers, thickness, and materials with specification item. For the existing structure, sections should be as detailed as possible. Proposed or existing positive drainage systems should be indicated on the typical sections.
- TPP Traffic Data and any adjustments to the traffic data.
- Results of NDT to characterize the existing structural condition (including the MODULUS backcalculation summary).
- Design input values and output.
- FSP-19W summary, modified Texas Triaxial check, mechanistic checks, stress analysis, etc. for flexible pavement.
- AASHTO (DARWin or TSLAB86) design summary for rigid pavements.
- Conclusion. The pavement design report will conclude with a recommended pavement design based on the data, analyses, and procedures included in the report. The information included in the report should be a synthesis of all work performed to arrive at the recommended pavement structure.
- Appendices.
- Surface Aggregate Selection Form 2088 (Wet Weather Accident Reduction Program [WWARP], flexible pavements only)
- Additional appendices, as needed (results of borings, material lab tests, raw PMIS data, life-cycle cost analysis, drainage analysis, etc.).
For specific cases that do not require a pavement design report (2R projects, sections less than 500-ft. in length, non-structural overlays), documentation should be retained at the district. The documentation should include a brief description of the criteria, engineering considerations, and/or district policy used in the decision process.
For other reporting requirements, contact the district pavement engineer for guidance.
Anchor: #i1010731Completing the Pavement Design Report
The pavement design report may be prepared by anyone having knowledge of the specific project under development and is familiar with the analysis tools used. The first licensed engineer in the chain of responsibility will review and sign the report. After completion of the pavement design report development phase, please follow the procedure to complete the report described in the following table:
|
Step |
Action |
|---|---|
| 1 |
The district pavement engineer (DPE) generally has approval authority (see Section 2, 'District Pavement Engineer's Role'). The DPE is responsible for reviewing the technical content of the report and appropriateness of the design for conditions cited within the report. |
| 2 |
If the report is approved, the approval is indicated by the DPE signature, license number, and date on the report cover sheet. If the district does not have an assigned or certified DPE, the report must be forwarded to the director of CST-M&P for approval. |
| 3 |
After the annotated engineer license number on the approved report, add the phrase “This document is released for the purpose of interim review and is not intended for bidding, construction, or permitting purposes” (in accordance with paragraph 137.33[e] of the Texas Engineering Practice Act). |
Anchor: #i1010740
Pavement Design Report Review and Archive
A copy of all completed pavement design reports must be submitted to the director of CST-M&P for review and archive.
Archived reports can be viewed on the TxDOT intranet (site not available to internet users) at the ‘Plans Online’ page located at http://gsdpolaws/ under the heading, ‘Pavement Design.’
Newly assigned DPEs are encouraged to arrange attendance of the required training sessions for flexible and rigid pavement design, as soon as practical, through the director of CST-M&P (see District Pavement Engineer’s Role).