FoSSA (2.0)

FoSSA (2.0) is an interactive program for assessing stresses and settlements under embankment and footings acting on horizontal ground surfaces. ADAMA Engineering had developed the copyrighted program FoSSA Version 1.0 and licensed it to the US Federal Highway Administration (FHWA). Version 1.0 has been designated exclusively for use by US State Highway Agencies and by US Federal agencies. ADAMA Engineering offers version 2.0 to the public.

Within the foundation soil, FoSSA calculates the stress distribution under embankment having complex geometry, the elastic (immediate) settlement, the consolidation settlement (including isochrones: excess porewater pressure and settlement during the consolidation process), accelerated consolidation settlement due to PVD’s (triangular and square installation patterns), secondary settlement, and undrained shear strength distribution within consolidating layers. It can deal with up to 50 soil layers in the foundation (consolidating or not) and up to 20 layers comprising the embankment (e.g., representing alternating layers of geofoam and soil). It can deal with staged construction calculations. Stress distribution is based on numerical integration of the basic Boussinesq equation (therefore allows for various embankment geometries). Elastic settlement is based on numerical integration of Hooke’s equations. Consolidation settlement (1-D) solves Terzaghi’s differential equation using a finite difference scheme. PVD’s design follows: Prefabricated Vertical Drains, Vol. I: Engineering Guidelines, by Rixner, Kraemer, and Smith, Haley & Aldrich, FHWA report FHWA/RD-86/168, September 1986, Contract No. DTFH61-83-C-00101 (basically, it is a practical modification of Barron’s solution developed for vertical sand drains). The undrained shear strength calculations during consolidation follows: Stability Evaluation during Staged Construction, by Ladd, Journal of Geotechnical Engineering, ASCE, 1991, Vol. 117, No. 4, pp. 540-615.

FoSSA (2.0) can calculate stresses and settlements under multiple rectangular footings. Computations follow the same theories as those used for embankments.