Page 182 - Numerical Analysis and Modelling in Geomechanics

MODELLING OF GROUND WAVES 163

Figure 5.24 Vertical displacements of three surface nodes during vibrodriving, (a) free-
ground and (b) with a brickwork wall.
vibrations. The vibrations are strongly sinusoidal, matching the driving
frequency. Attenuation is non-uniform, possibly due to the presence of a standing
wave.
The choice of axisymmetric mesh of finite elements is governed by the
wavelength and transmission speed. In addition, spurious boundary reflections
must be eliminated from the computation within the zone of interest. This may
be achieved by the use of infinite elements of various kinds, or by expanding the
finite element mesh sufficiently. Specific problems and advantages of infinite
elements have been discussed.
Detailed wave analysis generally requires considerable computer power and
time, above that which is available for normal piling activities. The empirical