CTLGroup was retained to perform a preliminary rigid and flexible pavement design for sections of the SH 71 Managed Lanes project, incorporating Alternative Technical Concepts (ATCs) accepted by TXDOT. Scope of work included document review, pavement thickness design, material selection, evaluation of subgrade soils properties, and responding to requests for information during the construction phase.
Pavement designs were prepared as required over the design life. These included flexible designs prepared using TXDOT’s FPS-21 software as well as rigid designs using the AASHTO Guide for Design of Pavement Structures. These designs met the Mechanistic and Triaxial checks for pavement performance. The Effective PI was specified by TXDOT as the procedure for mitigating expansive clay soils prevalent at the project site in central Texas. The conventional flexible design consisted of a Thin Overlay Mixture (TOM) for a high performance surface, a Performance Graded Type C Surface and Type B Base Mixture, and a high-quality prime coat underseal. The base layer consisted of an untreated flexible base. Overlay options were allowed and are scheduled in year 15. A Continuously Reinforced Concrete Pavement was specified for the SH 71 main lanes east of FM 973 and included a bond breaker with 6-inch cement treated base.