Field performance of a waterproof anchored vegetation system for protecting expansive soil slopes during rainy season

• A waterproof anchored vegetation system (WAVS) is used in the protection of expansive soil slopes. • The effect of a waterproof anchored vegetation system on expansive soil slope is discussed by field tests. • The influence of heavy rainfall on WAVS-protected expansive soil slopes during the rainy season is investigated. Expansive soil slopes are usually characterized by drag failure from shallow to deep due to the active water-heat exchange environment. To reduce the adverse effects of the rainy season on expansive soils in humid areas, a new ecological flexible protection method, namely a waterproof anchored vegetation system (WAVS), is proposed. WAVS consists of polymer waterproof coating (PWC), high-performance turf reinforcement mats (HPTRM), anchors, drainage pipes, and vegetation. Four test expansive soil slopes with different protection methods (bare, WAVS, anchor-reinforced vegetation system (ARVS), and grassed slope) were constructed, and field tests were carried out during the rainy season to explore the protective effect and mechanism of WAVS. The results show that the water migration and heat energy transfer in the expansive soil slope have become complicated due to hydrothermal interaction; the deformation of the expansive soil slope is positively correlated with the amplitude of the soil water content change. The duration of rainfall had a greater adverse effect on expansive soils than rainfall intensity, and this effect was more pronounced under evaporative conditions. WAVS has an excellent water and heat regulation effect, effectively reducing the deformation of expansive soil slopes by up to 40% and adjusting the diurnal temperature change by more than 50%. It also serves a dual role in ecological and environmental restoration, offering a new technical solution for the long-term green protection of expansive soil slopes.