Abstract: In the past, grey materials such as cement were used to build and reinforce embankments in the Yellow River basin to prevent soil erosion, which caused serious damage to ecological environment. In response to the national strategy of ecological protection and high-quality development of the Yellow River basin, environment-friendly biopolymers were used to improve the typical silt in the Yellow River basin. In this paper, the water retention characteristics of biopolymer-improved silt are measured with WP4C instrument, and the mechanism of biopolymers to improve the water retention characteristics of silt is analyzed from a microscopic point of view. Compared with unimproved soil, the water content of biopolymer modified silt after saturation increases, the void ratio increases, and the water holding capacity is significantly improved. The water retention capacities of the silts modified by xanthan gum, gellan gum and guar gum increase with increasing the gum content, and the improved effect of gellan gum surpasses those of xanthan gum and guar gum. The improvement mechanism can be explained that the biomolymer particles form hydrogel through hydration, filling the pores between particles and increasing the adhesion between particles. In addition, pore space similar to honeycomb structure is formed in the improved silt by xanthan gum and gellan gum to provide water storage space, thus improving the water retention characteristics of the improved soil. The above research results can provide a scientific basis for the safe and scientific application of biopolymer in the prevention and control of soil erosion in the Yellow River basin.

Key words: silt, xanthan gum, gellan gum, guar gum, water retention characteristic