This report includes the fundamental theoretical aspects
of geophysics applied in environmental surveys. The main
emphasis is put on analysing of electrical,
electromagnetic, and soil temperature measurements.
Petrophysical basis necessary for quantitative
interpretation and modelling is covered.
Some theoretical formulas and laboratory measurements of
water samples indicate that the salinity(TDS) can be
interpreted from surface measurements and that TDS is a
relatively reliable indicator of groundwater
Geophysical methods can be successfully used both before
waste disposal operations for evaluation of site
characteristics and for monitoring of possible leachate
flow. When galvanic electrical survey takes place some
forth of sounding-profiling array is superior in the
sense of earth section coverage and cost effectiveness.
Among the many possibilities, the set - Wenner-B,
pole-dipole and pole-polearrays - was chosen. Layered
earth and three-dimensional modelling indicate that the
combination of arrays covers the depth range of 0 - 30
metres. Direct inversion methods and aspects in layer
model interpretation are discussed. It was also noted
that the self-potential method may offer new
possibilities in the detection of leakage points.
Electromagnetic methods from another variety of tools for
earth probing purposes. After fundamental concepts the
selected three-layer earth models are analysed in
frequency and time domain and for loop(dipole) and plane
wave excitation. The same models are used as with
galvanic electrical methods to allow easy comparison.
Dielectric effects are taken into account and the
apparent resistivity sounding curves are also calculated.
The results of the EM-theory indicate that the
EM-sounding methods would be powerful techniques to be
used together with electrical methods in detecting
near-surface structures, but the instrumentation
currently available does not cover high frequencies or
the early time transients required. The possibilities of
plane wave methods in the detection of lateral
resistivity changes are also discussed. The results of
the VLF-theory indicate strongly the dominating and
masking effects of shallow soil structures.
The possibilities of using the soil temperature
measurements in evaluating hydrogeologic conditions in
groundwater flow systems is studied by means of a case
study example from the existing landfill site in Tuusula.
The results were not found encouraging due to complicated
interpretational points of view.
|Place of Publication||Espoo|
|Publisher||VTT Technical Research Centre of Finland|
|Number of pages||126|
|Publication status||Published - 1987|
|MoE publication type||D4 Published development or research report or study|
|Series||Valtion teknillinen tutkimuskeskus. Tutkimuksia - Research Reports|
- environmental surveys
- municipal engineering
- electromagnetic methods
- soil properties