“Computational Civil Engineering - "Intersections" International Journal

“Computational Civil Engineering 2005”, International Symposium 189both of the criteria are met, formulae ∆ tn+ 1 = 1. 2 ⋅ ∆tn (where ∆ t0denotes theinitial time step) is adopted to determine the increment of the time step. In thisway, the number of iterations is greatly reduced while accuracy is satisfied.6. A NUMERICAL APPLICATION WITH THE RAM PROGRAMIt is well known that rutting in flexible pavement is a gradual damaging processcaused by the accumulation of permanent deformations. In this paper, thevisco-elastoplastic method stated above is employed to give an estimation of itsdevelopment. To do this, a structure of three layers is modelled with the pulse striploads being used to represent the moving vehicles, Figure 2. Apparently, thissystem can be simplified as a plain strain configuration with its vertical boundariesbeing held in the horizontal direction and its lower boundary being completelyfixed.Figure 2. Structure of flexible pavementsSince our main interest in this paper is the mechanical behaviour of asphaltmixtures, the cement bound granular sub-base and the cohesive soil are idealized asperfectly plastic materials and it is assumed that Mohr-Coulomb criterion can beused as their yield functions. The surface layer is assumed to be made up of hotrolled asphalt with the design parameters being chosen from Table 1 [7].