Theory of Seepage Into Auger Holes

We shall solve the problem for seepage which occurs immediately after the hole has been either partially or completely emptied, water previously having been standing in the hole at the level of the water table. This is the condition utilized, as shown in another paper by ourselves (9), for determining soil permeability. In solving the problem we assume that the soil is~of uniform permeability down to an impervious layer; that Darcy's law, and consequently Laplace's equation, is valid, the problem being thus one of potential theory. We shall solve the problem analytically for the case that the hole just reaches or penetrates the impervious layer, and shall show how, using an electric model, the problem may be solved when the hole does not reach the impervious layer. Since in a model it is impossible to represent accurately an infinite expanse of soil, which is the actual field condition, the problem will be solved on the assumption that in the field a circular cylinder, coaxial with the auger hole, penetrates the soil down to the impervious layer. In the field this cylinder may be considered to be of sheet metal. In the electric laboratory model, the cylinder becomes the dielectric wall of a circular tank containing electrolyte. It will be shown that the radius of the model tank need not be impractically large in order to simulate the actual field condition.