## 4 Impact of Climate Change and Practical Implications
While a higher soil shear strength is expected for drier conditions due to elevated levels of matric suction, the frequent wetting-drying cyclic changes will influence the soil macro and microstructure (e.g., development of a network of micro-cracks) that will in turn contribute to progressive deterioration of shear strength especially when compacted soil is subsequently exposed to wetting [34]. The atmospheric temperature together with relative humidity levels are the main drivers of the level of evaporation taking place although prevailing wind direction, vegetation type and cover, permeability and compaction conditions have been reported to also play a role [35]. The moisture variation in the ground also takes place up to a certain depth where the soil is likely to be subjected to wetting and drying cycles induced by from climatic changes. The rate of this change is typically dependent of the water retention behaviour of the soil, runoff and type of soil cover (bare, vegetation or impermeable) and the magnitude is controlled by climatic action, e.g., prevalence and patterns of rainfall or drought conditions. While the estimation of the depth of moisture change (Hs) is complex, a simple procedure based on local climate using Thorrnthwaite moisture index (TMI) distribution may be adopted. Table 4 shows the relationship between the depth of moisture change according to TMI values and type of climate classification for Australian Territories. The location of the site from which samples were collected can be classified as wet temperature with a TMI of 20 and thus depth of change of moisture would be 1.5-1.8 m. While there are other aspects related to soil behaviour such as water retention, permeability, compaction conditions and soil microstructure that strongly influence water flow in unsaturated materials, the TMI method provide a rough estimate of this depth. This paper examines the comparative behaviour of various stabilisers used in industry, and shows their impacts on several variables, including Atterberg Limits, swelling and shear strength behaviour, microstructure and chemical composition. The results presented \begin{table}
\begin{tabular}{c c c} \hline
**TMI** & **Classification** & **Depth of Moisture Change, Hs (m)** \\ \hline \(>\)40 & Wet coastal & 1.5 \\ \hline \(10\) to 40 & Wet temperate & 1.5–1.8 \\ \hline \(-\)5 to 10 & Temperate & 1.8–2.3 \\ \hline \(-\)25 to \(-\)5 & Dry Temperate & 2.3–3.0 \\ \hline \(-\)40 to \(-\)25 & Semi-arid & 3.0–4.0 \\ \hline \(<\)\(-\)40 & Arid & \(>\)4.0 \\ \hline \end{tabular}
\end{table} 
Table 4: Depth of moisture change with Thorrnthwaite moisture index values (after [36]). directly showed the comparative effectiveness of these stabilisers for controlling volume change and shear behaviour of a natural expansive soil in roadworks or earthworks conditions. While all stabilisers were effective, HL was best to control one dimensional volume change whereas the specimens treated with PC showed the best performance in the post-inundation conditions. However, it should be noted that the greatest shear strength gains resulting from the stabiliser addition are limited to relatively small strains. This is reasonable as the soil is likely to experience levels of shear strain (1%) smaller or comparable to those reported at yield during service. From an environmental footprint standpoint, each stabiliser can be compared by considering the embodied emissions of their production. As the emissions associated with transport, labour and machinery will vary depending on the location, source and means of application, these will be excluded from the calculation process.