Thornthwaite moisture index and depth of suction change under current and future climate ‒ An Australian study

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Climate change is one of the major global challenges and it can have a significant influence on the behaviour and resilience of geotechnical structures. The changes in moisture content in soil lead to effective stress changes and can be accompanied by significant volume changes in reactive/expansive soils. The volume change leads to ground movement and can exert additional stresses on structures founded on or within a shallow depth of such soils. Climate change is likely to amplify the ground movement potential and the associated problems are likely to worsen. The effect of atmospheric boundary interaction on soil behaviour has often been correlated to Thornthwaite moisture index (TMI). In this study, the long-term weather data and anticipated future projections for various emission scenarios were used to generate a series of TMI maps for Australia. The changes in TMI were then correlated to the depth of suction change (Hs), an important input in ground movement calculation. Under all climate scenarios considered, reductions in TMI and increases in Hs values were observed. A hypothetical design scenario of a footing on expansive soil under current and future climate is discussed. It is observed that a design that might be considered adequate under the current climate scenario, may fail under future scenarios and accommodations should be made in the design for such events.