Filtration characteristics and mechanism of geotextile filters under cyclic flow

Geotextile filter layers are extensively utilized in revetment structures for riverbanks, floodwalls, and dams. These structures are often located in complex hydraulic environments, so geotextile filter layers may be subject to long-term cyclic flows. In this study, based on a self-developed gradient ratio test device, a series of gradient ratio tests under different hydraulic gradients and normal stresses were carried out to investigate the filtration characteristics and mechanisms of soil-geotextile systems under cyclic flow. The results show that the risk of particle erosion under cyclic flow is greater than the risk of system clogging, and the magnitude of hydraulic gradient and normal stress have an important influence on the filtration behavior. The boundary scour effect caused by the cyclic flow is proportional to the hydraulic gradient, while the normal stress enhances the retention of the soil through the benign geotextile blockage effect. The corresponding visual inspection analyses reveal that stable arching structures can be formed near the filter interface under cyclic flow, thus mechanically enhancing the stability of the system. These mechanisms suggest that strategic adjustments of the overburden pressure can optimize the structural stability of the soil-geotextile system in flood-prone environments.