FLAC3D is a numerical modeling code for advanced geotechnical analysis of soil, rock, and structural support in three dimensions.

FLAC3D is used in analysis, testing, and design by geotechnical, civil, and mining engineers. It is designed to accommodate any kind of geotechnical engineering project where continuum analysis is necessary. FLAC3D utilizes an explicit finite difference formulation that can model complex behaviors not readily suited to FEM codes, such as: problems that consist of several stages, large displacements and strains, non-linear material behavior and unstable systems (even cases of yield/failure over large areas, or total collapse).

The dynamic analysis option permits three-dimensional, fully dynamic analysis with FLAC3D. The calculation is based on the explicit finite difference scheme to solve the full equations of motion, using lumped gridpoint masses derived from the real density of surrounding zones (rather than fictitious masses used for static solution). This formulation can be coupled to the structural element model, thus permitting analysis of soilstructure interaction brought about by ground shaking. The dynamic feature can also be coupled to the groundwater flow model.

This allows, for example, analyses involving time-dependent pore pressure change associated with liquefaction. The dynamic model can likewise be coupled to the optional thermal model in order to calculate the combined effect of thermal and dynamic loading. The dynamic option extends FLAC3D's analysis capability to a wide range of dynamic problems in disciplines such as earthquake engineering, seismology and mine rockbursts.