Experimental Study of the Dynamic Characteristics and Microscopic Mechanism of Lightweight Soil Modified with Expanded Polystyrene and Sisal Fibre

Abstract

With the increasing demand and use of highways, railways and tunnels in China, the phenomena of foundation settlement, uneven deformation and ground cracking caused by the cyclic loading by traffic are becoming increasingly significant. There is now an emphasis on research to prevent or decrease these phenomena by mixing new materials into the soil body. In this study, cyclic loading tests were conducted on lightweight soils modified with expanded polystyrene (EPS) and sisal. A GDS true/dynamic triaxial apparatus was used to study the dynamic elastic modulus and damping ratio of clays with different dosages of EPS and sisal fibre. The modified soil samples were tested, and then, they underwent micro-scale analysis. The results showed that, with the continuous increase in EPS doping and dynamic stress, the trend of the growth of the dynamic strain of the specimens increased. At the same time, with the increase in the dynamic strain, the dynamic elastic modulus decreased, and the trend increased with increasing doping of the soil with EPS particles. A comparison of the improvement effect coefficient of the soil samples showed that the most suitable EPS doping volume was 5%. Different dosages of sisal fibre were added to the most suitable EPS-modified lightweight soil, and the dynamic elastic modulus first increased and then decreased with increasing sisal dosage. In addition, the damping ratio first increased and then decreased. The best dynamic performance of the soil was obtained when the dosage of sisal was 1.2%. Nuclear magnetic resonance and electron microscope scanning tests verified that, when the sisal doping was 1.2%, the soil particles had the largest compactness, the best interparticle bonding and the best improvement effect.