Soil Vibration; Man-made vibrations; Soil Damping; Material damping; wave propagation
Résumé :
[en] Man-made vibrations from different types of sources are usually measured on
the surface of the ground or building. The measured signal is always the superposition of all
travelling basic waves. For a homogeneous half space there are three basic waves – the
Compressional (P-wave), Shear (S-wave) and Rayleigh wave (R-wave). Depending on the
measuring equipment, only the accelerations or velocities in time of the superposed wave can
be measured, but not the distribution of the individual basic waves.
Additional problems are that each of the basic waves has its own velocity, besides the
body and surface waves have different attenuation laws. By using the rules of superposition
of harmonic waves and also the propagation laws of the P-, S- and R-waves, it should be
theoretically possible to split the measured superposed signal into the basic waves, because
mathematically a system of equations can be assembled which describes the displacements at
multiple measuring points in time.
In this paper this problem has been solved for a homogenous, elastic and isotropic soil,
which is disturbed by a harmonically oscillating disc on the surface. A numerical simulation
was performed using a finite element method. The displacements in time were recorded in 10
points on the surface and a system of superposed equations was assembled and solved.
The findings prove that each of the three basic waves has its own phase shift with the
source, something which was not known before.
