In situ study of the shrinkage-swelling of a clay soil over several cycles of drought-rewetting

• An observation of soil displacements over five cycles of shrinkage-swelling is proposed.
• Water content is correlated with temperature and displacement.
• The influence of heterogeneous lithology is observed on the soil behavior.
• The accumulated hydric condition is a good indicator of the behavior of soil under shrinkage and swelling.

This article presents results describing the in situ behavior of clay soils (Pleistocene Brach formation) regarding shrinkage and swelling; an experimental site was established. Different types of sensors were used to continuously measure the movements of the clay bed-rock and variations in the temperature and water content of the soil. These parameters were correlated with annual climatic variations as measured at an on-site meteorological station. The results obtained thus far represent five cycles of drought-rewetting, thus enabling a medium-term study of the shrinkage-swelling of a clay soil over time. A cumulative effect of shrinkage over several cycles was observed with non-negligible variations of water content to a depth of 3 m. Almost 1 cm of cumulative shrinkage occurred over the first three cycles of a 2-meter-thick clay layer. The last two cycles were marked by a stabilization of the swelling. By determining the accumulated soil hydric condition over time, we discovered a correlation between this parameter and the periods of shrinkage-swelling. The accumulated hydric condition, as defined in this article, is a good indicator of the behavior of soil under shrinkage and swelling.