Permissible spatial variation of CCC data from driving comfort requirements over time

Abstract

Spatial variations of soil properties occur even within nominally homogeneous soil layers. Therefore, to achieve a reliable geotechnical design, it is necessary to consider local variations of soil properties. Varying soil stiffness leads to spatially variable settlements, implying increasing dynamic forces on passing vehicles. Higher dynamic forces result in additional settlements and simultaneously reduce driving comfort. This process continues steadily until repair of the asphalt pavement is required. The aim of this study was to develop a new mechanically reasoned method for deriving the permissible spatial variation of continuous compaction control (CCC) data from driving comfort requirements. A numerical model was developed that allows modelling of the long-term evenness of asphalt pavements due to passing vehicles, taking into account spatial variation of the subsoil stiffness. The numerical model is based on the subgrade reaction method, modelling the surface and subjacent base courses by a series of spring elements. Thereby, a depth-dependent stress distribution and interactions of the base courses are considered. The initial stiffness of the spring elements is derived from oedometer tests. Depending on the traffic load and utilisation period, the long-term evenness of an asphalt pavement and the effects of a spatially varying subsoil stiffness can be investigated.