Synergistic effects of water content and temperature on the rheological behavior of loess and its implications for loess geohazards

The synergistic effect of elevated water content and temperature is a critical trigger for loess landslides and mudflows. The initiation and movement of these hazards are intrinsically governed by complex rheological behavior, highlighting the significance of understanding loess rheology. To investigate the influence of water content and temperature on the flow characteristics of loess, steady-state shear rheological tests were conducted on typical clayey loess from Jingyang County, Shaanxi Province. The tests encompassed seven levels of water content (1.25–2.75 w_L) and four levels of temperature (10–40°C). Results indicate that loess samples exhibit significant non-Newtonian shear-thinning behavior. Notably, its temperature sensitivity is regulated by water content, presenting a complex evolutionary pattern. At low water contents, the thermal lubrication effect dominates, causing viscosity to decrease with rising temperature. Conversely, this trend reverses at high water contents, as thermally induced particle aggregation and flocculation increase shear resistance, effectively overshadowing the thermal thinning effect of pore water. The medium water content range exhibits a non-monotonic response characterized by a ‘decrease-then-increase’ trend. Comparative modeling indicates that the Herschel-Bulkley model captures this complex non-linear behavior more accurately than the Bingham model. These findings highlight the dominant role of the synergistic effect of elevated water content and temperature in altering flow dynamics, providing a theoretical basis for predicting the run-out behavior of loess hazards under complex environmental conditions.