Soil Mixing to Stabilize Organic Clay for I-95 Widening, Alexandria, VA

The reconstruction of the Capital Beltway in Alexandria, VA requires substantial widening of the existing embankment into the adjacent swampy grounds that are underlain by 3m to 9m (10ft to 30ft) of highly compressible soft organic clay. The construction schedule does not permit sufficient time for using P.V. Drains in much of the U.S. Route 1 interchange area, so deep mixing was selected to provide the necessary ground stabilization. For stability, series of shear wall panels are used, formed by overlapping soil-cement columns elements. A large area of the embankment will be placed on individual columns of soil-cement that are used solely for load support, thus greatly reducing settlement. The design analysis applied to the stability and the settlement control applications are described.