Simulation of precipitation on centrifuge models of slopes

Abstract

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.

A device for rainfall simulation in geotechnical centrifuges

“…The raindrops are accelerated to an impact velocity of approximately 0.7 m/s. With the density and impact velocity of the raindrops, the impact force is estimated to be 10 Pa in accordance with the equation proposed by Tamate et al [16]. Moreover, the defection raindrop path is found to be negligible as a result of the short falling height.…”

“…The first attempt on rainfall-induced slope failure in a centrifuge model was made by Kimura [9]. Since then, various rainfall systems have been introduced by, e.g., standard nozzles with droplet diameters in the order of magnitude of millimetres [7], mist spay nozzles or atomizing nozzles operated with high back pressures [6,11,15,16], spaying water mist by hand [10], and a single water source at the slope shoulder as subsurface flow to initiate base liquefaction [13,14].…”

Centrifuge Model Tests of Rainfall-Induced Landslides

“…The initiation of static liquefaction failure mechanism was also investigated by other researchers [9,10]. Finally, failures of sandy slope models, induced by heavy precipitation, were modelled in a geotechnical centrifuge using liquids with varied viscosity in order to simulate rainfall events [11], paying also attention to the impact pressure of the droplets to the ground surface.…”

Centrifuge model study of thresholds for rainfall-induced landslides in sandy slopes

“…Many studies have been performed in the past regarding the centrifuge modelling of slope behaviour under rainfall conditions ( [2], [3], [4], [5], [6]). …”