CORRELATION BETWEEN STATIC AND
DYNAMIC PARAMETERS
In the past, emphasis of geophysical investigations
was to provide general information about geologic
formations (stratification) and ground water
conditions. However, for geotechnical design it is
necessary to obtain parameters, which can be
correlated directly with geotechnical parameters.
Several geophysical methods can be used for this
purpose. An example is seismic testing, especially
down-hole and cross-hole testing. Seismic methods
were initially was used for determination of traveltimes, from which wave velocities, and in particular
the P- (compression) wave velocity was determined.
However, shear wave velocity has turned out to be a
more useful parameter for geotechnical applications,
as its measurement is independent of the
groundwater situation. The shear wave velocity can
also be determined with higher accuracy (as it is
much slower than the compression wave velocity).
SEISMIC METHODS FOR STATIC
GEOTECHNICAL APPLICATIONS
In the past, seismic measurements have been
considered “dynamic” and thus not relevant for
“static” geotechnical problems. However, it can be
shown that seismic field and laboratory tests can be
used for the determination of static deformation
properties of soil and rock, Massarsch (1981). This
can be illustrated with the following example of
vibration measurements in medium dense sand
above the groundwater level.
The shear wave velocity was measured by
geophones placed at increasing distances from a
vibration source, Figure 1. The measured vibration
velocity amplitude at 10 m distance was 0,5 mm/s
and the period of vibration was 0,019 sec (53 Hz).
The shear wave velocity corresponded to CS = 151
m/s (5 m / 0,033). The shear strain level can be