Simulation of precipitation on centrifuge models of slopes

This paper discusses methods for realistic simulation of slope failure owing to heavy precipitation in a centrifuge. A rain simulator was developed to provide precipitation that satisfies the conditions in a centrifuge so that the impact pressure on the ground surface in the centrifuge (pm) was reduced to the same level in the prototype (pp). Pneumatic spray nozzles, producing fine droplets with a mean diameter of 20 µm, yield large precipitation intensity of 1500 mm/h on the model at 50g. Accordingly, the model precipitation intensity (rm) was provided by n times the corresponding prototype precipitation intensity (rp). Several sets of centrifuge tests were conducted to observe the progress of failure in the shallow section of the slope. Heavy precipitation induces an increase in the saturation of the soil from the surface. Flow failure was observed repeatedly in the shallow section through progress of the wetting front. In addition, experiments using different viscosity used in the liquid for precipitations were carried out to compare the types of failure. Larger failure by precipitation of the viscous liquid was observed than that of water even when equivalent permeability conditions are maintained. This paper also introduces a method of measuring shear deformation in the shallow section by bending strains, allowing monitoring of the progress of failure.