The consolidation of a deep clay stratum subject to an impermeable axisymmetric surface loading

Previous analytic solutions to the problem of the consolidation of a deep clay stratum subjected to a surface loading, have been obtained for the assumed condition of a completely permeable upper surface. This may not be so in many applications, where the foundation causing the loading may be impermeable, and therefore only that part of the clay surface outside the loading is free to drain.In this paper a method is presented which may be used to obtain the time-settlement behaviour of a circular loading applied over an impermeable region of the surface of the clay. The solution technique involves representing the continuous values of fluid flow along the surface boundary as uniform blocks of flow. The solution is found in Laplace transform space and a numerical inversion technique is then used to obtain the time dependent solution.Two types of surface loading are examined; a completely uniform loading and a loading distribution which is approximately that of a rigid footing. For the uniform loading case, comparisons are made with previous solutions (permeable surface) and it is shown that the assumption of an impermeable loaded region leads to significant changes in the time-settlement behaviour of the loading.