Predictive model for water retention curve of water-absorbing polymer amended soil

Water-absorbing polymer (WAP) amendment is emerging as a sustainable soil management technique in various geoenvironmental projects for controlling the subsurface water flow in the vadose zone. The addition of WAP can alter the pore structure and improve water-retention characteristics of the soil. The existing water-retention characteristic curve (WRCC) models for polymer-amended soils are complex and require a number of empirical parameters, which cannot be easily obtained through simple laboratory experimentation. The current study proposes a simple predictive WRCC model for WAP-amended soils based on the understanding that WAP particles absorb and retain water within their polymer structure and therefore influence the void ratio. The proposed model captures the change in the void ratio of the amended soil through a modified phase relationship for predicting WRCC. The performance of the model was validated for four different textured soils with varying WAP concentrations. The comparison between measured and predicted WRCC indicates that the proposed model can capture the changes in the void ratio as well as the WRCC with adequate accuracy.