Modelling of Climate Induced Moisture Variations and Subsequent Ground Movements in Expansive Soils

Expansive behaviour of soil in response to moisture changes is a significant issue for lightly loaded structures. Recent reports have shown more than 4000 houses in Victoria, Australia have been damaged due to abnormal moisture changes beneath footings. For design purposes, the moisture change due to climate is crucial. This paper provides details of modelling of climate induced soil moisture changes and subsequent ground movements. The soil moisture variation due to climate was modelled using Vadose/w for two sites in Melbourne, Australia. The model was validated against the regular measurements from the field. The predicted soil moistures from the Vadose/w model were used to predict the possible ground movement using FLAC3D. The predicted ground movements were also validated using the field monitored ground movements at the sites. Further, the model was used to determine the possible ground movements due to long-term climate conditions. The model results demonstrate the reductions of soil moisture and shrinkage movements during the millennium drought. The model predictions also suggest that the soils have not been able to fully recover that moisture deficit through the drought breaking rains in 2010 and 2011. This model can be used to observe expectable ground movements due to climate changes and hence can greatly assess the footing performance for different climate scenarios.