Control Factors and Assessment Technique of Relative Density Using Pluviation Method for Saturated Model

Accurate control of relative density (D_r) in saturated pluviation method is the fundamental requirement for low relative density sample preparation of dynamic centrifuge liquefaction tests. To achieve an evaluation method on pluviation stability, a set of duckbill pluviator which fits saturated modeling was developed. Three groups of dry and saturated sand model contrast tests were carried out to identify the impacts of nozzle size, drop distance and movement velocity, aiming to assess the capability of the developed sampling device. A mini dynamic penetrometer facility was applied to measure the spatial distribution of the saturated model’s D_r, giving a homogeneity evaluation of the models. A particle-flow-velocity model for pluviation was derived to give a normalize criteria for density stable control. The results show that the optimal size of nozzle is 3mm which satisfies the requirements of low compactness modeling. The change rate of D_r with thickness of water is 3.5 times of that with air drop height, indicating that thickness of water layer is the dominant factor on D_r of saturated model. The nozzle movement velocity is up to 31% of particle velocity which is non-trivial on the low density sample preparation. The travelling speed and drop height play a decisive role in particle flow velocity and D_r.