Effect of biopolymer and plant fiber on soil-water characteristics of sandy soil

Abstract The synergistic treatment of sandy soil with biopolymer and plant fiber as a soil improvement technique offers both stable strength and sustainability. However, due to the hydrophilic nature of both materials, soil structure is modified, thereby affecting its water retention capacity. To predict the effect of the combined treatment on the internal moisture of stabilized soil, it is of great significance to develop a non-saturated soil water retention model applicable to the synergistic improvement of biopolymer and plant fiber. Existing models do not account for the interactions between biopolymer and plant fiber with soil. In this study, various interaction mechanisms between biopolymer and soil are considered, including: (1) Biopolymer and plant fiber occupy part of the pore space, thereby altering pore volume of the soil; (2) Biopolymer and plant fiber themselves possess certain water-holding capacity; (3) The expansion of biopolymer and plant fiber may cause changes in soil volume, and their expansion is constrained by soil particles. To validate the new model, water retention curves were obtained through centrifuge measurements and computational verification of existing literature data. The experimental and calculated results demonstrated good consistency. The findings confirm that the new model effectively predicts the water retention characteristics of various soils after synergistic amendment with biopolymer and plant fiber.