C. Rampino et al., Laboratory testing on an unsaturated soil: equipment, procedures, and first experimental results, CAN GEOTECH, 36(1), 1999, pp. 1-12
This paper describes two new apparatuses recently developed at the Universi
ta di Napoli Federico II (Italy) in order to test soils under unsaturated c
onditions. The related experimental procedures and the first results obtain
ed on a dynamically compacted silty sand are also discussed. The devices me
ntioned are a Bishop and Wesley stress-path cell and a Wissa oedometer, mod
ified to control matric suction and to measure all the stress-strain variab
les relevant to unsaturated soil mechanics. Specific experimental procedure
s were established to perform tests under general conditions and were caref
ully verified during several tests. Using the triaxial cell, isotropic and
anisotropic compression stages were carried out under constant suction leve
ls of 0, 100, 200, and 300 kPa. Furthermore, two deviator stages were perfo
rmed following different stress paths and water drainage conditions. Using
the oedometer, an additional suction level (400 kPa) was investigated durin
g compression tests driven up to 5 MPa of vertical net stress (sigma(v) - u
(a)). This research is a part of a major project in progress at the Diparti
mento di Ingegneria Geotecnica of Naples; it is aimed at the experimental a
nalysis of the behaviour of several dynamically compacted soils and at the
numerical modelling of boundary problems related to earth structures.