Evaluation of Long-Term Performance of Pavement Drainage Layers on I-469 in Indiana

Subsurface drainage is important for long-term pavement performance. Rational procedures to analyze and evaluate the design, reliability, and effectiveness of subsurface drainage systems are needed in order for their use to be recommended with confidence. Three pavement subdrainage test sections were constructed in 1995 on the eastbound driving lane of I-469 in Indiana, at the northern junction with I-69, between Stations 150+05 and 173+40. Presented are the original laboratory characterization and mechanistic evaluation for permanent deformation and stability of the test sections employing finite element analysis. Triaxial tests were conducted on all pavement layers of the sections. Falling weight deflectome-ter evaluations in 1995 and 1998 are also presented. Such measurements are not available after 1998 because compliance with Indiana Department of Transportation safety regulations is required at that location. Finite element analyses were conducted by using laboratory-measured material properties to predict pavement response to falling weight deflec-tometer loads, compare predicted and measured deflections, examine layer shear stability for shear stress and strength, and predict rutting. Long-term pavement performance indicators up until 2007 (including international roughness index and ground penetration radar), after 12 years of heavy truck traffic, are also presented. Finite element analysis predicted very well the deflections measured by the falling weight deflectometer and accumulated rutting of the three test sections. Comparisons of shear stresses and strengths indicated that the sections were stable. All long-term evaluations indicated that all drainage layers in the study sections have performed their function adequately and protected the subgrade.