Turf-reinforced waterproofing system for expansive soil slopes under rainfall–evaporation

Expansive soil slopes are highly susceptible to shallow cracking, strength degradation and deformation under alternating rainfall and evaporation. This study investigates the performance of a turf-reinforced waterproofing system (HTRWS) comprising a high-performance turf reinforcement mat (HPTRM) and a polymer waterproof coating (PWC) for protecting expansive soil slopes. Three comparative model slopes, namely a bare slope, an HPTRM-protected slope and an HTRWS-protected slope, were subjected to five rainfall–evaporation cycles, during which volumetric water content, pore water pressure, and vertical and horizontal deformation were monitored continuously. The results indicate that rainfall–evaporation cycling strongly affected the hydro-mechanical response of the shallow slope zone, with the influence decreasing with depth and with clear lag effects in moisture and pore-pressure response. The maximum volumetric water content changes in the HPTRM- and HTRWS-protected slopes were 75.19% and 24.27% of that in the bare slope, respectively, while the corresponding maximum pore water pressures were 75.76% and 16.18%. The maximum vertical and horizontal displacements of the bare slope were 1.41–4.35 and 1.27–4.91 times those of the protected slopes. Under the present test conditions, the HTRWS substantially restricted external water exchange, reduced swelling–shrinkage deformation, and limited surface deterioration.