Practical Application of Blanket Theory and the Finite-Element Method to Levee Underseepage Analysis

The U.S. Army Corps of Engineers’ blanket theory has been successfully used to evaluate levee underseepage for many years. The method was developed from closed-form analytical solutions based on the principles of groundwater hydrology. More recently, the proliferation of computing resources has made finite-element analysis (FEA) a tool that is easily accessible to many geotechnical engineers. This study compares the results of blanket theory to FEA to delineate conditions in which the two methods provide essentially the same solution. The assumptions inherent to blanket theory are reviewed to provide designers with an understanding of its usefulness and limitations. Guidelines are provided for correctly assigning FEA boundary conditions that are consistent with the assumptions of blanket theory. For cases in which all of the assumptions are satisfied, the volumetric flow rate and excess head at the levee toe predicted by blanket theory were within 10% of those determined by using FEA.