Coupled saturated‐unsaturated quasilinearized steady state flows from buried and surface cavities

Abstract

The coupled saturated‐unsaturated flow that results from water‐filled cavities in soils is studied, under the assumption of quasilinearization for the unsaturated flow, using a combined boundary element‐finite element method. Buried two‐dimensional circular cylindrical cavities and two‐dimensional semicircular cavities are examined in detail. The effect of the size of the cavity and the soil type on the flux from the cavity and the size of the saturated zone and effectively wetted region is illustrated. Comparisons with previous analytical and numerical results, in which the depth of water in the cavity was neglected, are also made. These comparisons indicate the severe errors that are introduced into the calculation of the flux and the flow field when the depth of water is neglected. In particular, it is shown that the percentage error in the flux from a buried circular cylinder with water depth neglected increases from 20% to 220% as the dimensionless cavity size s increases from 0.1 to 1, and that the saturated zone extends to a depth of approximately 7.9 times the cavity radius for s = 1.