  In order to better understand the heave observed on the railway roadbed of
the French high-speed train (TGV) at Chabrillan in southern France, the
swelling behaviour of the involved expansive clayey marl taken from the site by
coring was investigated. The aim the study is to analyse the part of heave
induced by the soil swelling. First, the swell potential was determined by
flooding the soil specimen in an oedometer under its in-situ overburden stress.
On the other hand, in order to assess the swell induced by the excavation
undertaken during the construction of the railway, a second method was applied.
The soil was first loaded to its in situ overburden stress existing before the
excavation. It was then flooded and unloaded to its current overburden stress
(after the excavation). The swell induced by this unloading was considered.
Finally, the experimental results obtained were analyzed, together with the
results from other laboratory tests performed previously and the data collected
from the field monitoring. This study allowed estimating the heave induced by
soil swelling. Subsequently, the part of heave due to landslide could be
estimated which corresponds to the difference between the monitored heave and
the swelling heave.
