Natural cube stone road pavements: design approach and analysis

Cube stone road pavements commonly are recognized for their historical, cultural, aesthetic and ecological value. This type of traditional paving is still present and diffuse in Italy in important historic centers as well as in smaller towns where, thanks to their distinctive characters (materials, setts, schemes, typologies) represents a heritage to be preserved. A part technical features, local distinctiveness and quality streetscapes must be considered among the main issues and values to be considered in design and reinstating paving schemes. Among cities, L’Aquila had a wide stone paved historic center partially dismantled due to damages caused by the earthquake of April 6, 2009 to the underground services. In this work a design approach based on the finite element method (FEM) was adopted. A catalog of cube stones streets was proposed in order to provide a decision tool to the technicians for the dimensioning of these pavements. To this purpose, porphyry (6-8 cm) and limestone (10-12 cm) cube stones pavements were investigated in order to provide different aesthetic and technical solutions. Between paving layers and materials a linear elastic behavior and as traffic load condition commercial light trucks (80%) and urban buses (20%) were assumed. The admissible strain-stress states for the surface, the mixed granular foundation, the gravel mixed cemented and concrete slab are reported. The catalog provides, for specific load conditions, the thicknesses of the various layers of the structure paving that have determined stress-strain states lower than those considered admissible and able to guarantee a nominal life at least of twenty years. The results show that best nominal life and safety, even in increasing traffic volume during time, are obtained using porphyry cube stones and gravel mixed concrete cemented or concrete slab substrates.