Finite element computation of shape factors for Kirkham's piezometer tube method for hydraulic conductivity of saturated soil

The Kirkham piezometer tube method of measuring hydraulic conductivity of saturated soil uses a numerical constant (shape factor) to account for the relative geometrical parameters of the cavity and the soil domain. Published shape factors have mostly been determined using an electrical analogue. In this paper the application of the finite element method to shape factor determination is considered. Convergence is studied and methods of extrapolation evaluated. A determination is made of the size of finite region required to represent adequately the radially unbounded domain assumed for the piezometer method. Computed shape factors were found to be in good agreement with analogue data.