Influence of debris-flow property on the uplift pressure of closed check dam

Uplift pressure is a critical vertical load on check dam foundations, playing a pivotal role in dam structural design and stability. However, the characteristic of uplift pressure remains a complex and not fully understood. In this study, a specialized test device was designed; 36 tests were conducted to simulate the uplift pressure of closed check dams under varying debris flow conditions. The formation and evolution of uplift pressure were analyzed, along with the influences of debris flow bulk density and fine particle contents. Results indicate peak uplift pressure head decreases with increasing bulk density and fine particle content, initially at rapid rate then stabilizes gradually. The peak uplift pressure decreases rapidly with increasing density at low densities (1.1–1.3 g/cm3) and then slows at higher densities (1.4–1.6 g/cm3), forming a “flat.” However, the peak uplift pressure curve for P0.1 = 10% does not show this pattern, and the changing trend of density does not form a flat. Peak uplift pressure of dilute debris flow mainly results from permeability produced by hydraulic diffusion, while for viscous debris flow, it arises from excess pore water pressure. A calculation method for the peak uplift pressure reduction coefficient was proposed. The findings comprehensively improve the understanding of the action mechanism and evolution process of uplift pressure, enhancing the performance of check dams for disaster prevention and mitigation.