Adaptation of method of fragments to axisymmetric cofferdam seepage problems

The method of fragments can be used to efficiently obtain solutions to a variety of two-dimensional seepage problems, especially confined flow problems. With this method, the flow domain is divided into fragments that span zones, which are defined between certain critical planes, based on the assumption that the equipotential lines through each such plane are coincident with the plane(s) in question. A dimensionless form factor is then defined for each fragment, and the total flow rate is computed using these form factors in a straightforward manner. An extension of the method of fragments to the axisymmetric cofferdam problem is presented in this paper. A range of numerical simulations was used to generate design charts to obtain the required axisymmetric form factors and exit gradients. These were validated against detailed numerical solutions and against analytical solutions reported in the literature. The design charts presented in this paper are considered to provide very reliable estimates of the seepage conditions and for a wide range of cofferdam geometries of practical interest