Extraction of pavement and soil thermal diffusivity from measured temperature times series

This report describes several methods to extract pavement thermal diffusivity from pavement temperature measurements at two or more depths. Two methods use analytic solutions for heat transfer in an infinite solid to relate the attenuation of diurnal temperature change with depth to thermal diffusivity. The first approach considers the surface temperature forcing to be a simple sinusoidal function with a period of one day. The second method considers the surface temperature forcing to be a general periodic signal that can be decomposed with a Fourier series. The accuracy of these two methods are limited by non-homogeneous nature of pavement/subgrade/soil systems. The third method uses a one-dimensional finite difference heat transfer model to extract thermal diffusivity from measured pavement temperature. This method requires more computational effort, but can take into account the variation in thermal diffusivity between the pavement and underlying layers.