Retrogressive sliding can be observed in groundwater-induced landslides. The major inducing factor of this phenomenon is the fluidization in the down-hillslope and the soil of the bottom-layers. Moreover, when the water content in the area around the groundwater input pipe surpasses 29%, sag in the upper soil layer can also occur. As the groundwater discharge increases in experiments with the same slope, the equilibrium time needed to achieve landslide equilibrium gets shorter and the durations of landslides also decrease. As the slope in experiments with the same level of groundwater discharge increases, the equilibrium time required to achieve landslide equilibrium gets shorter, the landsliding area in a specific time period gets larger and the total landsliding area also decreases.
Key Words : Groundwater-induced landslide, free-end, retrogressive sliding.