Design of pavements

The use of the pressuremeter in pavement design requires to acknowledge the differences which exist between pavements and foundations. In pavement engineering, the ultimate bearing capacity is rarely considered because other design constraints, namely very small tolerable deflections, ensure that the factor of safety against bearing capacity failure is very large. There are essentially two sets of techniques to design a pavement, one is based on the use of charts, and the other is based on the use of computer programs modelling the pavement and the subgrade as a multilayer system. In the chart method the subgrade is characterized by an average stiffness. The total thickness of pavement necessary is given in a chart as a function of this average stiffness and of the design vehicle for a given level of traffic. In the multilayer system method, each layer has its own modulus and the loading of the pavement by the wheel is simulated with a multilayer elastic computer program.