Using a Reduced Equivalent Diameter for a Prefabricated Vertical Drain to Account for Smear

Many different formulations for converting a prefabricated vertical drain with a rectangular cross section to an equivalent diameter well have been developed. In addition to equivalent diameter, engineers must also consider the impact of smear when designing a system that utilizes prefabricated vertical drains. An experiment and mathematical modeling were used to study the validity of using a reduced equivalent diameter to account for smear. Mathematical modeling of the four most commonly used equivalent diameter formulations yielded nearly the same equipotentials. In addition, the equipotentials calculated for the equivalent diameter wells differed substantially from a prefabricated vertical drain modeled with and without smear. This indicates that equipotentials are not the best means to evaluate equivalent diameter formulations because the change in shape from a rectangle to a circle impacts the head values to such a degree that the equipotentials will never be similar, regardless of whether smear is included.