8/16/2019 Levantamento geofísico
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Levantamento geofísico para projeto degasoduto integrado ao
mapeamento dosubsolo para os projetos civis e elétricos
Pipelines projects require the availability of information about
the subsurface along its route, for the
civil and electrical designs. Geology comprises a wide range of
direct methods of prospecting the
soil, as SPT and rotating soundings etc. Geophysics performs
these investigations using indirect
methods from surface, determining soil parameters through
measurement of its physical properties.
The interpretation of these measures allows inferring the
subsoil structure with costs quite competitive
when compared with the direct methods. Among the geophysical
methods available, it should be
highlighted the Electroresistivity. This technique, by mean of
active (injection of electrical currents in
the ground) or passive resources (measuring the natural electric
and magnetic fields), allows to obtain
very accurate models of the subsurface, three-dimensional and
with great structure resolution,
depicting layers, faults, water table, rocky basement etc.
Typically these surveys are conducted early
in the project for the civil project. Considering that the
electrical engineering design studies need
electrical resistivity soil models, for the specification of
cathodic protection, for interference studies
where the duct line crosses with transmission lines and also for
the design of
grounding systems for pumping stations, “city gates” and other
installations along the duct route, it is
suggested in this paper the integration of geophysical surveys
conducted for the civil and electrical
engineering, in a single measurement campaign. This integration
will result on lower costs with
geophysical surveys, considering that the measuring teams will
go to field only once. It must also be
considered that the same equipments are used for the entire set
of measurements. An additional
benefit is that geophysics companies are usually more qualified
for this type of survey, than the small
companies that typically measure soil resistivity for electrical
design, usually limited to small spacing
Wenner measurements, which was the only one recognized by the
former version of NBR-7117,
specific code for the measurement of soil resistivity for
electrical projects. This code has undergoneextensive review and in
its new 2012 version, supports a wide range of geophysical
resources for
conducting soil resistivity measurements and soil modeling.
