Model tests of the evolutionary process and failure mechanism of a pile-reinforced landslide under two different reservoir conditions

Anti-slide piles are widely used for stabilizing landslides and a large number of landslide-piles systems were constituted in reservoir areas. How these landslide-piles systems evolve under reservoir effects is vital for the safe operation of dams. In this study, two reservoir conditions, namely condition of static water level and water level fluctuations, were considered for detailly exploring the influence of static and dynamic water pressure on a landslide-piles system in physical model tests. The pore water pressure, surface deformation and photographs of visual observations were obtained for comparatively analyzing the deformation characteristic and failure mechanism of landslide-piles models under the two conditions. The results show that the soil deformation and failure around the piles were similar in the two tests due to the same pile arrangements. However, retrogressive deformation and two soil collapses occurred in the landslide front area under water level fluctuations instead of slight deformation and shallow erosion under the static water level. The outward hydrodynamic pressure caused by reservoir drawdowns was the primary reason for the soil collapses in the landslide front area. The progressively intensified deformation around the piles which indirectly decreased the soil stability in the landslide front area was the secondary cause for the collapses. The Majiagou landslide-piles system in the field was identified as in the early period of the uniform deformation stage at present based on the field observations, monitoring data and the test results under water level fluctuations.