Review of the Theories for Sand Drains

The existing theories for vertical consolidation of clays by vertical flow of water and by radial flow to a drain well are satisfactory within the limits of the assumptions. The effect of considering void ratio as a variable did not significantly change the consolidation-time characteristics of vertical consolidation by vertical flow. Thus, including the effects of variable void ratio does not contribute toward the explanation of secondary consolidation. It has been demonstrated that a drain well having a smeared zone at its periphery can be considered as an equivalent “ideal” well of reduced diameter. Diagrams are included for quantitative evaluation of this relation. An example is included to show the effectiveness of even a small diameter ideal well in reducing the time for consolidation. Numerical procedures were found to be versatile aids for solving the classical consolidation problems as well as for considering consolidation under a variety of conditions. Variable rates of lMding, variable soil properties, and layered systems can be readily included in the treatment of consolidation problems by these methods.