The epsilon method: analysis of seepage beneath an impervious dam with sheet pile on a layered soil

Abstract

An approximate solution method, referred to as the epsilon method, allows flow characteristics such as flow rate and exit gradient to be determined for seepage through a two-layer soil system. The finite element program SEEP was employed to analyze flow characteristics of an impervious dam with sheet pile on a layered soil. Extensive analyses were performed for different conditions, including soil layer thickness, soil hydraulic conductivity, dam width, and sheet pile depth. The flow rate and exit gradient were determined for each condition analyzed. The results were reduced to simple charts, called the epsilon curves. The epsilon curves allow a designer to obtain solutions to the seepage problem without a computer code and to verify solutions obtained from a computer code. They are especially useful when searching for an optimum design of a masonry dam. The epsilon curves can be extended to a soil system comprising more than two layers. An example of a single-row sheet pile structure in a three-layer system is given to illustrate how to use the method for multiple-layer systems. The method was verified by comparing the results with those obtained from the SEEP program, and excellent agreement was noted.Key words: seepage, dam, sheet pile, layered soil, hydraulic conductivity.