Introduction > Overview

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 non-homogenous 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.