## 2 Materials and Methods
### Preparation of Soil Samples  
Bulk soil collected from the site was initially air-dried and then oven-dried at 105 \({}^{\circ}\)C for at least 24 h, following the guidelines outlined in BS 1377-1:2016 [29]. After drying, the soil was crushed and sieved through a 2 mm sieve to break apart clods and remove gravel-sized particles. This resulted in a uniform fine-grained matrix suitable for laboratory testing. Stabilising agents--either 6% ordinary Portland cement (OPC) or 1% guar gum (GG) by dry weight of soil--were carefully mixed with the prepared soil. This mixing was performed manually and supplemented with a mechanical mixer to ensure uniformity. Once the dry mixing was complete, water was incrementally sprayed onto the mixture and thoroughly blended until the target moisture content was reached. All samples were compacted at an approximately optimal moisture content (OMC) of 12% and 90% of the modified Proctor maximum dry density (MDD). Specim preparation involved static compaction of the moist soil mixture within cylindrical moulds to create samples measuring50 mm in diameter and 100 mm in height (height-to-diameter ratio of 2:1), which minimised boundary effects during triaxial testing. Each specimen was compacted in four layers to reduce air entrapment and promote uniform density. One hundred and eight samples were prepared and evenly divided into three groups: untreated, cement-stabilised, and guar gum-stabilised, with 36 samples in each group. Each group was further subdivided based on the number of wetting-drying (WD) cycles: 1, 5, 10, and 15, with nine replicates for each condition (Figure 1). The 1-cycle group served as control samples, representing the initial condition--they were compacted, cured, and reconstituted without undergoing cyclic moisture changes, thereby isolating the immediate effects of stabilisation without any environmental degradation. After compaction, all samples were cured under controlled laboratory conditions for 7 days at 25 \(\pm\) 2 \({}^{\circ}\)C, wrapped in sealed plastic to prevent moisture loss. This curing period allowed for initial cement hydration and guar gum gel formation, while maintaining the same conditions for untreated samples to ensure consistency in the experiment. No additional water was added during the curing period, and all samples were handled carefully to prevent premature drying or shrinkage cracking, especially in the cement-treated samples.  
Figure 1: Flowchart of the study. OMC = optimum moisture content, MDD = maximum dry density, WD = wetting–drying cycles.  
Following curing, the soil samples underwent the designated wetting-drying (WD) cycles (Figure 1). One WD cycle was defined as one complete sequence of wetting followed by drying. Wetting was performed by submerging the base of each specimen in water, allowing capillary rise until saturation was reached. The duration of the wetting phase varied among samples and treatments, although it remained fairly consistent within each treatment group. Due to changes in permeability and pore structure, later cycles required longer wetting times, especially for treated samples. Drying phases were carried out in a humidity-controlled chamber or desiccation apparatus designed to induce matric suction of approximately \(-1500\) kPa, corresponding to moisture contents near the plastic limit or OMC of the clay. Each specimen was subjected to its assigned number of WD cycles (1, 5, 10, or 15), with particular care taken to avoid mechanical damage, especially during handling in the softened, saturated state.