quick sand in large diameter wells: analytical and numerical analyses

large diameter wells gaining water from the bottom are dug in the sandy and collapsible aquifers. when the vertical hydraulic gradient on their bottom reaches a critical value, quicksand occurs. another difficulty encountered is drawdown in the wellbore and the drying up of the well. to overcome these problems, the flow around and beneath these wells isnumerically simulated and the dimensionless drawdown-time and dimensionless vertical gradient-time curves are developed. it was found that the ratio of filling material thickness to well radius affect the shape of these type curves. the type curves may be used to design pumping rate and duration as well as well radius.