Le Calcaire de Saint-Ouen

Saint-Ouen limestone:
its genesis an principal facies.
G. CHAMPETIER DE RIBES
The author begins with a brief description of the conditions of deposit (genesis) of
Saint-Ouen limestone and the transformations (diagenesis) which have affected it in
the course of geological ages. He then defines the stratigraphie limits of Saint-Ouen
limestone in the Paris area, referring to the La Frette section on the banks of the
Seine North of Paris. Several typical sections of this bartonian substage are then
presented, with a description of the variations in facies observed from West to East.
In conclusion, a section of Saint-Ouen limestone cannot be interpreted without a fairly
thorough knowledge of the regional formation, and the geologist must always bear in
mind the conditions of genesis of this deposit.
Definition of the layer
and some problems relating to it.
B. CARON
In connection with a number of highway projects and underground work in the Paris
area, the author carried out geological surveys of sites involving Saint-Ouen limestone,
and gives his views on the "complexity" of this layer and the methods which would
make it possible to gain a better knowledge of it.
He begins with a presentation of Saint-Ouen limestone encountered at various depths
in the subsoil of Paris and its suburbs. Then, from personal observations and from
results published by specialists, he describes the layer and its stratigraphic, lithologic,
tectonic and hydrogeological particularities in the Paris area, showing with some
examples that these particularities are not distributed at random. Conclusions are
drawn concerning a method of studying this geological formation in which collaboration
between the geologist and the soil mechanics engineer should prove extremely fruitful.
General mechanical properties
Of Saint-Ouen limestone.
Saint-Ouen limestone constitutes a very heterogenous layer presenting sometimes
shallow alternation of lithological varieties ranging from impervious plastic marl to
hard fissured rock. The layer is resistant, despite high water content and high indices
of plasticity and low cohesion.
To illustrate this fact, this article gives the water content frequency curves, Atterberg
limits and dry densities of about a hundred samples of Saint-Ouen marl. In particular,
it is seen from the plasticity chart that representative points lie along a line whose
s l
°P e i s different from the Casagrande line test l p
= 0.55 (W L
- 12).
Mechanical tests, rapid triaxial consolidated undrained tests, with measurement of
interstitial pressure, or slow consolidated drained tests, give values of the angle of
j. FLORENTIN intergranular friction f ' in the neighbourhood of 37°, whereas the values normally
to be expected in soils with indices of plasticity greater than 50 are much lower;
around 20°.
To attempt to explain this anomaly and to discover in particular whether it may be due
to a structure of the marl linked with physico-chemical phenomena, it is proposed
to study, at several well-identified levels of marl in the layer, the Atterberg limits
before and after curing, and the shear strength characteristics of undisturbed samples
and of disturbed samples of the same soils.
The author was responsible for a series of bridges whose pile foundations rest on
r
i r . • Saint-Ouen limestone.
Foundations of engineering
„ 4 . . : „ +u„ ~* n», any He enumerates engineer in all similar the circumstances.
problems which arose in this connection, and which will face
structures in the plain of Rosny.
anv enaineer in similar
£ rcumstances
.
p. CHASSANDE T^ The e
qquestions u e s t
j o n s 0 of f
r arate t e 0f of working, the the method of executing the foundations, and costs
of the various solutions adopted are successively dealt with.
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