Reduced-scale ultrasonic modelling of Rayleigh wave transmission over seismic barriers

Several types of seismic barriers have been proposed in the past to protect buildings from traffic-induced ground vibrations, mainly from propagating Rayleigh surface waves. In many cases the developers are forced to use direct experimental measurements on real size seismic barriers at frequencies typical for traffic-induced ground vibrations, i.e. at 10-100 Hz. As an alternative and much less expensive approach, a reduced-scale experimental modelling using ultrasonic Rayleigh wave propagation over very small-scale replicas of real seismic barriers is considered in the present work. Rayleigh wave pulses with the central frequency of 1 MHz have been used, which corresponds to the value of scaling factor about 1:1000. Propagation over three types of seismic barriers was investigated: 1) arrays of periodic vertical holes, 2) Combinations of periodically positioned trenches, including a single trench, and 3) statistically rough surfaces. The results of the measurements of transmission and reflection coefficients are presented.