The impact of climate as expressed by Thornthwaite Moisture Index on residential footing design on expansive soil in Australia

Climate change has become one of the most pressing environmental concerns and the greatest challenges to global infrastructure in society today. It has been proved by many researchers that Victoria along with other Australian states and territories has been experiencing a drying climate over the past several decades. Numerous lightly-loaded residential buildings constructed on expansive soils are subjected to distortions arising from differential ground movements. Many countries in the world include Australia, United States, Israel, India and South Arica have reported infrastructure damage problems due to the movement of expansive soils. The problems are particularly significant in Australia as 20% of the surface area in Australia is covered by expansive soils (Richards et al. 1983). The primary focus in this research study is the Thornthwaite Moisture Index (TMI). The main objective is to develop a program (based on Excel spreadsheet) for TMI calculation and to predict and produce future TMI isopleth map for Victoria, and thus to facilitate a better understanding of the impact of climate change on residential footing design and construction. In the thesis, long term climate records over 60 years (i.e. 1954 - 2013) from 70 weather stations of Victoria were adopted for TMI determination and this computation work was performed by the use of the program developed by the candidate. TMI isolines were then plotted on the Victoria map to present climate conditions since 1954. The main factors influencing climate change and ground movements were discussed. The past and the projected climate change, particularly for elements such as temperature, precipitation and sea level were also reviewed. Numerous emission scenarios and diverse climate models used to project the future climate were presented. Step-by-step method in predicting and quantifying future climate condition for Victoria by the use of TMI was demonstrated. The derived TMI results were then used for the delineation of isolines in Victoria map for 2030, and 2050 and 2070. Three case studies were carried out to facilitate a better understanding of different equations and methods used for estimating TMI as well as to demonstrate the effect of climate change on the characteristic ground surface movement ys, which was predicted based on the projected climate trend and the depth of seasonal design suction change Hs. The main contributions of this research are the updated as well as the predicted future TMI isopleth maps of Victoria, which superseded the old TMI map recorded in AS2870 (2011) and can be used to evaluate the impact of climate change on residential footing design. These maps have demonstrated that Victoria has experienced a significant growth of drying over the past 60 years and an overall increase of aridity for its future climate is expected if the drying climate trends are persisted. It is believed that the developed TMI climate tool would be very useful for design engineers and building industry