Variability of polymer for determination of soil-water characteristic curves

Unsaturated soil mechanics is crucial in understanding ground conditions and constructing geotechnical structures, particularly amidst the challenges posed by global climate change. Nevertheless, acquiring accurate soil suction values remains challenging due to limitations in existing methodologies, such as susceptibility to cavitation, high costs, and time-intensive procedures. Hence, this study employs a high-suction polymer sensor (HSPS) to evaluate the polymer's performance in determining soil suction. Subsequently, the polymers were used to measure unsaturated soil properties, especially soil-water characteristics curves (SWCC), based on osmotic principles. Five polymer samples classified as superabsorbent polymers (SAP) were synthesized with varying degrees of crosslinking, and their properties were assessed through swelling test and Fourier-transform infrared spectroscopy (FTIR). The soil sample from Turan, located within Nazarbayev University, was analyzed using a bimodal equation to determine the best fit. Results revealed that the swelling value and structural integrity of the polymer significantly affect soil suction capacity, with the findings being deemed temperature-independent, thereby obviating the need for calibration. Two potential factors hindering suction increase were identified: cavitation within the polymer or a reduction in the osmotic gradient due to polymer transformation into hydrogel formation. Overall, the novel polymer shows promise as an alternate material for SWCC measurement considering its simple method and being more sustainable compared to the other polymers, although further investigation is required to enhance the suction potential.