Przemysław Górnaś

Backcalculation of pavements incorporating Grouted Macadam technology

Applying cement grout with a high compressive strength to a porous layer made of asphalt concrete results in a pavement with the properties of an intermediate type that combines the characteristics of both flexible and rigid pavements. This solution is known as Grouted Macadam (GM). Despite a wide range of test results on the GM pavements presented in the literature, there are very few advanced modelling solutions formulated in the scope of bearing capacity measured in situ be means of a Falling Weight Deflectometer. This paper turns out that the seemingly small frequency of loading (≈20 Hz) generated during pavement deflection measurements using a Falling Weight Deflectometer-like device, has a significant impact on the backcalculation results of GM pavements. The study shows that, introducing frequency normalisation of both the pavement loading and vertical displacements to the backcalculation, can limit the statistical scatter of backcalculation results by close to a half in comparison with the classical backcalculation procedure.

The influence of frequency normalisation of FWD pavement measurements on backcalculated values of stiffness moduli

Backcalculation is commonly used for determining stiffness moduli of pavement courses and its subgrade based on in situ deflection tests. However, the in situ test results are dependent on the frequency domain, which in turn has a significant influence on the backcalculation results. In this paper, one of the methods for normalising the frequency of load and displacement functions obtained from a dynamic impulse generated by a falling weight deflectometer (FWD) test is verified. The assessment of the method is carried out based on backcalculation results of pavement deflection tests induced by both the dynamic and static loads and an independent numerical experiment. The analysis carried out in this paper shows that the normalisation of vertical displacements and pavement loads to the values corresponding to the frequency of 0 Hz improves the accuracy of the backcalculation results. It can be concluded that the frequency normalisation procedure is an effective way for standardising the boundary conditions in the backcalculation of flexible pavements.