Experimental Study of the Usage of Combined Biopolymer and Plants in Reinforcing the Clayey Soil Exposed to Acidic and Alkaline Contaminations

Abstract

In the last decade, biopolymers have been extensively studied, showing a great potential in soil reinforcement and the promotion of vegetation growth with limited environmental impact. In this paper, a soil reinforcing method with combined biopolymer (xanthan gum, XG) and plants (oat) was proposed to strengthen the clayey soil with different pore fluid pH values. A series of laboratory tests were conducted, mainly including the plant cultivation tests and the direct shear tests. It was found that oats grew better in the neutral, weakly acidic, and weakly alkaline soil environments. Both 0.25% XG and 0.50% XG that mostly promoted plant growth, also led to higher soil shear strength. An excessive XG content (e.g., 0.75% and 1.00%) may lead to the formation of a hard XG–soil matrix, preventing oat growth and therefore resulting in a lower shear strength. The XG–oat combination was found to be more effective in treating the soils with acidic pH values. Furthermore, the XG–oat combination is able to reduce the types and contents of heavy metal elements in the soil. Therefore, we suggest using biopolymers in combination with plants to improve the stability and geotechnical performances of the shallow soil slopes that are exposed to acidic and alkaline contamination.

Keywords

• xanthan gum
• oats
• clayey soil
• acidic/alkaline contamination
• direct shear test