Multiple Impact Surface Waves for Determination of Pavement System Moduli for Assessment and Design

The Multiple Impact Surface Wave (MISW) method involves the measurement and modeling of the propagation of surface waves in pavements. MISW can accurately determine not only the surface pavement thickness and low-strain elastic modulus of concrete and asphalt, but also the thicknesses and moduli of underlying base and subgrade layers. The MISW test method was used in a forensic concrete pavement investigation project and the thickness/moduli results for the concrete, base and subgrade layers are compared with Spectral Analysis of Surface Waves (SASW) results. The MISW method is able to accurately estimate the properties of base materials immediately below the much stiffer pavement layers by accounting for higher order wave modes during the inversion process in comparison to SASW results. Example results are presented of the use of MISW combined with Impact Echo (IE) data analyses to predict thickness/moduli of an asphalt pavement. Finally, a discussion is presented of the calculation of asphalt elastic moduli from MISW results for mechanistic-empirical design of asphalt pavements.