The influence of Y nodes in GPDS over pipeflow increasing hydraulic gradient in shallow landslides

As a prevalent phenomenon in shallow landslides, pipeflow gradually alters the internal structure of gravelly cohesive soil. In permeability tests, the scale of pipe network, pipeflow formation time, and position pressure were analyzed under various conditions. The results indicate that uncompacted soils with a higher gravel content exhibit characteristic flow in fewer time. Based on the flow paths, the hydraulic gradient of pipeflow was simulated. The findings reveal that the seepage force along the main pipe increases obviously and reaches its peak at the toe. Notably, a higher proportion of branch pipes are observed along the main pipe, suggesting that an increase in flow convergence facilitates flow movement and main pipe development. Three-dimensional simulations of typical nodes demonstrate that the Y nodes exert a more pronounced accelerating and shearing effect. Specifically, the flow velocity and volume increase by 4.77 times and 64% while the maximum shear stress is 14.42 times higher than normal. These findings suggest that amplified by the converging pipes, the greater seepage force along the main pipe reaches maximum near the toe. The research results of this study offer a novel theoretical foundation for the investigation and prevention of subsurface erosion in shallow landslides associated with seepage-induced deformation and failure in mountainous regions. In order to prevent and control the erosion to deformation, the surface cracks are sealed to reduce the infiltration to the main pipe seepage and the siphon drainage are set at the outlet of seepage path to decrease the seepage force at the toe.