Structural Design and Sensitivity Analysis of Semi-Rigid Pavement of a Motorway

This paper presents application of mechanistic-empirical methods in design of semi-rigid pavement for a section of a motorway in Poland. The stage construction was assumed. Three fatigue criteria were applied in the design. For asphalt fatigue cracking and subgrade soil the criteria from the Asphalt Institute (1981) were applied. For fatigue cracking of cement stabilized bases the Dempsey (1984) and De Beer (1992) criteria were applied. In the analysis it was assumed the cement stabilized layers will work in two phases: before and after cracking. To calculate stresses and strains software BISAR (1989) was used, which multilayer elastic theory utilized. Additional study was carried out to find the sensitivity of design thickness of asphalt layer related to several design factors. The most significant factors were (a) load transfer through shrinkage and reflective cracks, (b) high summer temperature which causes decrease of asphalt layers stiffness and increase of tensile stresses in cement stabilized bases, and (c) the effect of overloaded vehicles. The performed sensitivity analysis which included several interrelated factors, indicated that thickness of asphalt layers should be increased by about 4 cm as compared with preliminary design.