Early Pioneering Work
Early pioneering work in surface waves goes back to 1950s when the steady state method was first used by Van der Pol (1951) and
Jones (1955) (Fig. 1). At this time, it was based on the fundamental-mode (M0)-only Rayleigh wave assumption and all other types of
waves—higher modes, body waves, etc.—were ignored. This method then evolved later to be more-commonly called Continuous Surface
Wave (CSW) method (Matthews et al., 1996) (Fig. 2). In the meantime, the soil site inversion theory was refined by Tokimatsu et al.
(1991). Since the very early stage of the surface wave application, pavement was found to be more complex than soil (Sezawa, 1938;
Press and Dobrin, 1956), with a special type of guided wave called leaky waves that required a complex-domain approach in solving wave
equations (Jones, 1962; Vidale, 1964). A modern computer approach was introduced later by Martincek (1994), but it still produced
|Fig. 1. Early surface-wave application in 1950s.
|Fig. 2. Basic principle of Continuous Surface Wave (CSW) method.