ADONIS - Free Finite Element Software for Geo-Engineers

ADONIS is Free Finite Element Software for Geo-Engineers. The goal of the ADONIS development is to improve the modeling and computational simulation in geotechnical engineering. ADONIS is an easy-to-use yet powerful geotechnical-engineering tool for the linear and nonlinear analysis of geotechnical problems. It features a full graphical user interface (GUI) for pre-processing or post-processing and uses fully automatic mesh generator to create complex finite element meshes. The graphical interface enables a quick generation of complex models, and the enhanced output facilities provide a detailed presentation of computational results. The main features of ADONIS program are:

·        Graphical User Interface in ADONIS

The ADONIS user interface provides a complete interactive modeling environment, project management facilities, a built-in library of materials, easy specification of boundary conditions and structural elements, extensive plotting capabilities and run-time monitoring of results.

·        Model Construction in ADONIS

The first step in creating an ADONIS model is to create the boundaries defining the model. The geometric primitives such as line, circle, interface and etc. are provided to help users to create the model. Boundaries, bolts and polyline or polygon drawing tools can be imported into ADONIS from a DXF file (AutoCAD Drawing Exchange File), using the Import DXF option in the Import sub-menu of the File menu.

·        Discretize and Mesh

The finite element mesh can be created. ADONIS incorporates an open-source state-of-the-art two-dimensional automatic finite element mesh generator (i.e. triangle), which can generate triangular finite element meshes. The advanced meshing algorithm used in ADONIS simplifies the task of mesh generation for the user - a high quality mesh can be generated with just one mouse click.

·        Constitutive Material Models

The constitutive models provided in ADONIS are arranged into elastic and plastic model groups. Input parameters to all of these built-in models can be entered directly as commands, interactively using the GUI or controlled via JavaScript to modify the behavior of the models. Built-in material properties database includes 6 standard models such as IsoElastic, Mohr-Coulomb, Strain-Hardening/Softening, Modified Cam-Clay, Hoek-Brown, Modified Hoek-Brown.

·        User-Defined Constitutive Models (UDCM)

 From Version 2.5.5 forward of ADONIS, users can define their own constitutive model and integrate the model into the program by using a dynamic-linking library (dll). The dll needs to be placed in the installation folder of the program. The program will then detect and load the dll. One or more materials can be included in the dll.

·        Interface Constitutive Models

There are currently two standard joint behavior models available for ADONIS:

o   Glued Interfaces: If interfaces are declared glued, no slip or opening is allowed, but elastic displacement still occurs, according to the given stiffnesses.

o   Coulomb Shear-Strength: The Coulomb shear-strength criterion limits the shear force by the relation: F_smax = cL + tanφ F_n  where c = cohesion (in stress units) along the interface, L = effective contact length, and φ = friction angle of interface surfaces. If the criterion is satisfied (if |F_s| ≥ F_smax), then F_s = F_smax, with the sign of shear preserved.

·        Solutions in ADONIS

ADONIS features a number of solve tool that enables the automatic detection of the steady-state solution for mechanical problems. Modeling continues to be performed until a limiting condition is met, including the following.

o   Step: Executes model with specified number of timesteps.

o   Solve: The ratio of the maximum unbalanced force to the total applied forces in the model is small.

o   Solve Elastic: Sets element constitutive models to infinite strength for model equilibrium. This prevents artificial plastic deformations due to numerical shock.

o   Solve FOS: ADONIS provides an automatic factor-of-safety solution using the Strength Reduction Method (SRM) that can be used for stability analyzes of models.

o   Solve Relax: Force on the boundary of excavation will be reduced to a prescribed level, to simulate 3D effect of a tunnel advance. This reduction of the force will happen gradually during predefined number of steps to avoid a large tensile stress in the element which might cause by the excavation.

·        Factor of Safety Analysis in ADONIS

The Shear Strength Reduction module in ADONIS allows you to automatically perform a finite element slope stability analysis, and compute a critical strength reduction factor for the model. The critical strength reduction factor is equivalent to the "safety factor" of the slope.

·        Structural Elements in ADONIS

Structural elements for ground support include: beams, cables, tiebacks and strips.

·        Scripting in ADONIS

A scripting language embedded within ADONIS that enables the user to define new variables and functions. These functions may be used to extend ADONIS’s capabilities or add user defined features (e.g., servo-control boundaries may be applied to a numerical test, unusual property distributions specified, and parameter studies automated).

·        Plotting Results in ADONIS

The ADONIS user interface provides a complete interactive modeling environment, project management facilities, a built-in library of materials, easy specification of boundary conditions and structural elements, extensive plotting capabilities, and run-time monitoring of results.

·        Utilities in ADONIS

o   Tables: Tables are convenient data structures consisting of a number of x,y pairs. Tables may be plotted, imported and exported as ASCII data files. Tables can be used in ADONIS to vary friction, cohesion, dilation, tensile strength with accumulated plastic strain for the strain-softening model.

o   Histories: Histories are recordings of displacements, strains and stresses at a user-defined location (some node, element). By default, histories are recorded every 10 calculation cycles, but this can be selected by the user. A time history of as many as 500 variables can be made in one run. Histories may be plotted (versus time, steps or another history), converted to Tables and exported as an ASCII data file.