What Types of Stress Waves are Introduced into a Structure by Impact?

If transient stress waves are introduced into a concrete structure by mechanical impact at a point on the surface, as shown in Fig. 1, the stress waves include a dilatational (P-) wave and a distortional (S-) wave, which propagate into the structure along hemispherical
wavefronts, and a Rayleigh (R-) wave, which propagates along the surface of the structure. Among the stress waves, the P-wave propagates fastest and the R-wave propagates slowest. The S-wave propagates slightly faster than the R-wave. In an infinite isotropic elastic solid, the P-wave speed, Cp, and the S-wave speed, Cs, are related to the Young’s modulus of elasticity, E, Poisson’s ratio, v, and the density, p. For a Poisson’s ratio of 0.2, the R-wave speed is 92% of the S-wave speed and 56% of the P-wave speed. The motion of a particle disturbed by the P-wave is parallel to the direction of wave propagation while the particle motion disturbed by the S-wave is
perpendicular to the wave propagation direction as schematically illustrated in Fig. 1.

The particle motion disturbed by the R-wave is elliptical. The vertical disturbance of a particle on the impact surface caused by the R-wave arrival is much larger than that caused by the S-wave and P-wave arrivals.