Experimental study of mechanical behaviour of clayey materials under hygrom
etric condition is usually performed either on unloaded samples or by means
of classical oedometer tests used in soil mechanics. Such methods are not
well adapted to hard deep clayey rocks with little deformability, porosity
and permeability. Moreover, stress and strain tensors having a significant
effect on hygro-mechanical behaviour and properties cannot be measured and
investigated appropriately by classical tests. This is why a specific triax
ial test was designed in which the sample is surrounded by a fiber glass ti
ssue allowing air circulation and then by silicon on which confining pressu
re is applied. Thus, equilibrium between air and sample was reduced. Stress
and strain tensors were also measured in time on the sample subjected to a
mechanical loading and to a controlled suction. After presentation of the
test, preliminary results are given. (C) 2000 Academie des sciences / Editi
ons scientifiques et medicales Elsevier SAS.