The Asphalt Rutting Within a Highway Tunnel A Case Study

Asphalt rutting is a major permanent degradation issue caused by the high temperature and the cyclic load of vehicles along roadways. In this work, a highway slow lane within a tunnel was affected by a relevant deformation in a relatively short time. The investigation focused on a 200 m road distance. Benkelman deflection tests on the road surface, measurements of the depth of the road deformation, particle-size distribution of the road base, Proctor and CBR tests were performed. The unbinded underground material matched the required limits. Moreover, a concrete basement with a thickness up to 60 cm was present between the upper bituminous layers and the unbinded sub-base. The concrete increased the stiffness of the whole pavement system. The road base exhibited a good bearing capacity, while the reason for the rutting needed to be found in the middle and lower bituminous layers, in spite of the wide curvature of the permanent deformation.