Bearing behaviors of annular geotube dams considering interface friction effects

This study proposes a sludge storage dam constructed by stacking sand-filled annular geotubes of geotextile, and investigates its design and stability via model tests and DEM simulations. Model tests on a multi-layered dam reveal non-uniform local tension distribution in the geotextile due to interface friction between sand-geotextile and geotube-geotube contacts. Interlayer friction suppresses tension in the bearing zone, while tension in the non-bearing zone exhibits a gradient distribution, peaking at the junction. Geotextile ultimate tensile strength positively correlates with bearing strength, whereas modulus and filling ratio indirectly affect tension by altering tube geometry. A DEM framework was established, calibrating mesoscopic parameters to characterize macroscopic responses of the geotextile, sand, and their interfaces. Simulations analyzed evolution of geotextile stress, displacement patterns, and the influence of key parameters on bearing behavior. The mechanism by which interface friction regulates tension distribution and gradient, thereby affecting ultimate bearing capacity, was clarified. Finally, by introducing a modified principal stress ratio function and a tension attenuation model incorporating interface friction effects, a calculation method for ultimate bearing strength based on maximum local geotextile tension is proposed, considering non-uniform tension distribution and sand strain-softening. DEM results agree well with the proposed formula, verifying its accuracy.