[en] FLAC (Fast Lagrangian Analysis of Continua), Version 2.20, is a two-dimensional, large-strain, explicit finite difference code written for analysis of problems in geotechnical engineering. FLAC has the ability to perform static mechanical analyses as well as transient heat transfer and fluid flow simulations. Various constitutive models are available to describe linear and non-linear response of the solid. Coupling can be performed between the thermal and mechanical, as well as the fluid and mechanical, models. The following report presents the documentation specified in NUREG-0856, Documentation of Computer Codes for High Level Waste Management. The documentation is presented in three volumes. Volume 1 contains the mathematical basis for the various aspects of the code; Volume 2 is the code User's Manual, and this document, Volume 3, presents FLAC verification, example and benchmark problems. 5 refs., 135 figs