Climate Change Impacts on Reactive Soil Movements

Climate affects the extent of soil moisture variation likely to occur through time and hence the amount of foundation movement likely to occur at a reactive soil site. The Thornthwaite Moisture Index (TMI) as a useful climate parameter has been widely employed in Australia to estimate the depth of design soil suction change (Hs) which is needed for the determination of characteristic ground movement (ys). Precipitation and temperature are the primary weather parameters required for the TMI computation. By applying the projected rainfall reduction and temperature increase in 2030, 2050 and 2070 in the TMI calculation, the effects of climate changes on expansive soil movements and site classification can be quantified by the use of the predicted TMI. In this study, TMI values of various areas of the State of Victoria were calculated by using climate projections generated from 23 climate models. These predicted TMI indices were then used to delineate TMI isopleth lines on the map of the State of Victoria to visualize and compare climate conditions in 2030, 2050 and 2070. These maps show an overall significant growth of drying for the State of Victoria, where the most noticeable increase of aridity is expected to occur in 2070. The general decrease in TMI value across various areas of Victoria indicates a prominent reduction in average soil moisture availability. This implies that residential slabs are likely to experience greater ground movements due to the greater depth of Hs, which in turn may result in a higher incidence of slab edge heave and an increase in the occurrence of distortion of residential buildings built on expansive soils.