State-of-the-art review on plant-based solutions for soil improvement

Vegetation has been used as a means in geotechnical engineering for soil improvement and erosion control.This paper aims to present a state-of-the-art review and future prospective on soil improvement and reinforcement with plants,mainly from a perspective of plant mechanical effects.The mechanics of roots and root-soil composite are reviewed with regard to experiments,including root mechanical tests,direct shear tests,pullout tests and triaxial tests.Various factors influencing root reinforcement are characterized and discussed to explain root-soil interactions and related soil strengthening mechanisms.Considering cost and efficiency,extreme climates,and the conflicting mechanisms of plant growth and soil improvement,researchers have introduced nature-based water-soluble polymers(WSPs)into soil improvement to promote vegetation establishment and provide additional binding strength between soil particles.Despite the benefits,existing related researches and concepts are scarce,and there is still a significant knowledge gap in the coupling effect of WSP and plants for soil improvement.The review indicates that the combination of vegetation and WSP has the potential to create“trade-off”and“complementarity”for progressive soil improvement.Finally,new research topics in the field of soil improvement with plants are identified in the review.