Case Study of a Foundation Improvement beneath MSE Walls for a Highway Embankment

Since its introduction in the United States, Mechanically Stabilized Earth (MSE) wall technology has proven itself over and over again with millions of square footage constructed over the past 40 years. However, when weak foundation soils exist on a project site, some owners still may question whether the use of MSE wall technology is acceptable. Such questions may indicate a lack of knowledge or lack of information regarding different techniques available to ensure stability. Whatever the case, many projects around the country have been successfully built in soft bearing soil conditions using either modified construction techniques or additional foundation improvements beneath the MSE wall volume. One project where foundation improvement was deemed necessary was located at the intersection of I-44 & Sheridan Road in Tulsa Oklahoma. The project was originally designed for typical cast-in-place (C.I.P.) concrete retaining walls supported on a spread footing & piles. The successful contractor proposed an alterntive to the C.I.P. walls which consisted of MSE walls supported on stone columns. The alternative was presented to and accepted by the Oklahoma Department of Transportation. The savings was estimated at $220,000. This paper will discuss the development of the project, the geotechnical investigation, and the design considerations of the stone columns.