GFAS is a finite element package that has been developed specifically for the analysis of

deformation and stability analysis in geotechnical engineering problems. GFAS is an easy-to-use yet
powerful geotechnical-engineering tool for the linear and nonlinear analysis of homogenous or nonhomogenous
structures in which soil models are used to simulate the soil behavior. It features a full
graphical interface for pre-processing or post-processing and uses the Finite Element Method
(FEM) for 2D solids for its analysis purposes. The graphical interface enable a quick generation of
complex finite element models, and the enhanced output facilities provide a detailed presentation of
computational results. The analysis procedures are fully automated and based on robust numerical
procedures.
The basic program features include:
· Graphical input of geometry models: The input of soil layers, structures, loads and boundary
conditions is based on convenient CAD drawing procedures, which allows for a detailed
modeling of the geometry contour. From this geometry model, a 2D finite element mesh is easily
generated.
· Automatic mesh generation: GFAS allows for automatic generation of structured and
unstructured 2D finite element meshes with options for global mesh refinement. The program
contains a built-in automatic mesh generator that considerably simplifies construction of the finite
element model. Both triangular (3-noded or 6-noded) and quadrilateral (4-noded or 8-noded)
elements are available.
· Higher-order elements: Quadratic 8-node and 6-node triangular elements are available to
model the deformations and stresses in the soil.
· Optimization of the matrix bandwidth to reduce the computer storage and calculation time
can be performed by the program using internal re-numbering of the system equations.
· Staged constructions: Complex multi-stage models can be created and analyzed such as:
tunnels, excavations, embankments, soil reinforcement, etc.
· Beam-column elements: The program offers a wide range of support modelling options such
as liners, anchors and geotextile. The beam -column elements in either Bernoulli or Timoshenko
theory are incorporated in the code and enabled the user to create complex finite element
models in which both plane and line elements interact each other. Liner elements can be used in
the modelling of tunnel lining or sheeting structures. Bolt types include end anchored or fully
bonded. These elements can be assigned anywhere in the mesh.
· Steady state flow analysis: The program includes the steady state flow analysis built right into
the general program. Water pore pressures are determined as well as flow and gradient based on
user defined hydraulic boundary conditions and material permeability. The water pore pressures are
automatically incorporated into the finite element stress analysis.
· Dynamic and seismic analysis: The program allows the users to carry out a dynamic analysis
for determining the eigen values and eigen mode for construction and consequently to determine
the seismic forces according with Eurocode 8.
· Elasto-plastic material models: The present release offers the following models: Mohr-
Coulomb and Von-Misses models for elasto-plastic behavior of plane elements. Both models are robust and simple non-linear models and are based on soil parameters that are well known in
engineering practice. Both anchored and geotextile elements could have either a linear elastic or
elasto-plastic behaviour