Experimental and DEM investigation of thermal effects on mechanical properties of biopolymer treated soil

Abstract

To address the adverse impact of high-temperature climates on soil subgrade and other earthen infrastructures, this study investigates the thermal effects on the mechanical properties of biopolymer treated soils. By conducting temperature-controlled direct shear tests and discrete element method (DEM) simulations, the study examines the influence of temperature on shear strength, deformation characteristics, and microstructural behavior of biopolymer treated soils. Two widely used biopolymers: xanthan gum (XG) and gellan gum (GG) are employed in this study. As the temperature rises from 5 °C to 65 °C, the shear strength of GG treated soil decreases by 50.1 %, whereas XG treated soil experiences a smaller reduction of 21.2 %. DEM simulations reveal that elevated temperatures result in broader shear bands and reduced inter-particle contact forces. Specifically, for untreated soil and XG treated soil, the shear band width increases by 25.9 % and 25.4 %, respectively, as the temperature increases from 5 °C to 65 °C. In contrast, for GG treated soil, the shear band width initially expands by 104.2 %, followed by a reduction of 66.8 %. Furthermore, as the temperature increases from 5 °C to 65 °C, the average contact force of untreated soil, XG and GG treated soil decreases by 15.0 kPa, 24.7 kPa, and 49.4 kPa, respectively. The GG treated soil shows a more significant loss in shear strength and more pronounced microscopic changes. These results suggest that both biopolymers effectively improve soil mechanical properties, while XG demonstrates superior thermal stability, making it more suitable for reinforcing subgrades and embankments in regions with substantial temperature fluctuations.