Temperature-dependent soil water retention and hydraulic conductivity model for biopolymer-treated soil

With the growing emphasis on sustainable development in geotechnical engineering, biopolymers are emerging as eco-friendly soil improvement agents. However, the influence of temperature on the hydraulic performance of biopolymer-treated soils remains poorly understood. This study develops a novel model to describe the water retention and saturated hydraulic conductivity ( k s ) of biopolymer-treated soils under varying temperature conditions. The model integrates the temperature-dependent effects on biopolymer water absorption, swelling behavior, and hydrogel viscosity. Laboratory experiments were conducted to validate the model. As temperature increased from 20 to 60 °C, gravimetric water content of biopolymer decreased by 49%, leading to a reduced swelling effect. In parallel, biopolymer viscosity declined by 34%–50% between 5 and 65 °C. Elevated temperature diminished soil hydraulic performance. Saturated water content decreased by 4.9% at 1% biopolymer dosage, as temperature rose from 20 to 60 °C. Both air-entry value and residual water content also declined. Soil k s decreased by nearly four orders of magnitude with a 1% biopolymer dosage at 25 °C. However, this effect weakened at elevated temperatures, as k s increased by 4.3-fold when temperature rose from 5 to 65 °C. The proposed model accurately reproduced these results, offering a reliable tool for designing sustainable geotechnical systems under varying climatic conditions.