Design of embankments supported on controlled modulus columns

Abstract

<p>In recent years, the use of controlled modulus columns (CMC) to support road or rail embankments over soft ground at bridge approaches has gained popularity in Australia. Despite their higher cost per unit area of ground treatment compared to other methods, CMC are often the preferred method of treatment when time is of the essence. CMC enable accelerated construction of bridge abutments due to their speed of installation and ability to limit lateral soil and abutment pile movements during embankment construction. In Australia, most CMC supported embankments to date have been designed using similar principle as piled embankments, with the columns treated as structural elements to take all the applied loads. The authors believe that there is scope for CMC to be more cost-effective if they are designed to function as geotechnical elements.</p><p>This paper examines a number of CMC design issues, including the effect of columns stiffness and spacing on settlement reduction, the need for load transfer platform over the columns, and what if the columns crack when their bending moment capacity is exceeded, and do columns need to be reinforced. An economic design approach is recommended and two case studies are provided to illustrate the use of CMC to support bridge approach embankments.</p>