Propagation of mechanical waves in very heterogeneous media for concrete characterisation
Date Received
2006/10/09
Field
Non Destructive Testing - Ultrasound
Duration
12 months (with at least 10 months in 2007 ð Post-doc starting before the 1st of March 2007)
Location
Nantes, France, Europe
Description
The Reconnaissance and Geophysics Section of LCPC is currently working in a European
project (MEDACHS-INTERREG) and a French project (SENSO-ANR) dealing with the non-destructive
testing of cover concrete with surface waves. Roughly speaking concrete can be
considered as a matrix (cement + water) and inclusions (aggregates) mix. The mechanical
characterisation of the first centimetres of concrete structures with ultrasound can no longer
rely on the hypothesis of a homogeneous medium of propagation. Indeed the aggregates,
which size varies from a few millimetres to two centimetres, are heterogeneities having the
same size as the required wavelengths.
The objectives of the post-doc will be to consider the propagation of surface waves in hetero-geneous
media when the wavelength is near inclusions size. The project is to pursue numeri-cal
simulations (either discrete or semi analytical) in conjunction with experimental work (using
a newly designed interferometer laser laboratory) to better understand the physical phenom-ena
linked to the interaction of surface waves with heterogeneities. The numerical work will
firstly focus on numerical modelling of the Rayleigh wave interaction with one inclusion and
will secondly deal with more complex interactions in case of numerous heterogeneities i.e.
very strong heterogeneous media. Special attention to the simplifying assumption in relation to
the civil engineering current media of propagation will be required. Experiments will be carried
out on concrete slabs of various compositions with non contact ultrasound (air coupling, laser
interferometer).
The underlying application field is the mechanical characterisation of cover concrete and more
precisely the determination of the porosity of the matrix shallow first 5 centimetres.
Skills required:
PhD in geophysics (seismic) or PhD in non destructive testing (ultrasound).
Partners:
Our partners are, on the one hand, specialists of propagation in very heterogeneous media
(LOA, LGIT, GDR 2501 Ultrasound) and specialists of concrete material investigation (CDGA,
GEA, GeM, LABEIN, LCND, LEPTAB, LMDC, etc.).
Expiration
2007/12/01
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