Hydro–mechanical behavior of a sandy loess improved by villus–inspired superabsorbent hydrogel for ecological restoration

The sandy loess regions on the Chinese Loess Plateau (CLP) has experienced severe surface erosion， primarily due to low vegetation cover and poor mechanical properties of the underlying soil. This study evaluated the potential of the villus-like superabsorbent hydrogel (vlSAH) to improve the hydro-mechanical properties of the sandy loess， with dual symbiotic aims of promoting vegetation establishment and enhancing the soil’s mechanical stability. A series of laboratory testing， including short-term water absorption， long-term water retention， suction-controlled drying， one-dimensional compression， and direct shear tests， was conducted on the sandy loess with varying dry densities (1.3， 1.45， and 1.6 g/cm³) amended by different dosages (0.05， 0.1， and 0.5 wt.%) of the vlSAH. Results show that adding 0.5 wt.% vlSAH to sandy loess increases its short-term water absorption by approximately 40%， while vlSAH addition increases the air-entry value by 8.9%-32.5%， 72.4%-118.4%， and 27.5%-78.6% at dry densities of 1.30， 1.45， and 1.60 g cm^-3， respectively. The incorporation of vlSAH (0.05-0.5 wt.%) into the sandy loess also leads to a 61.8%-237.4% increase in yield strength and the transformation of a sand into a cohesive soil with a cohesion of 0.28-8.68 kPa. Microstructural observations reveal that the vlSAH promotes aggregate formation and a dense microfabric， thereby improving the hydro-mechanical properties of the sandy loess. These findings demonstrate that the vlSAH can simultaneously support vegetation establishment and enhance the soil’s mechanical stability， and thus offers a promising measure for the CLP erosion control.