Itasca FLAC3D (3D Fast Lagrangian Analysis Code) is a high-end three-dimensional numerical analysis program developed based on continuum theory and explicit finite difference methods, widely used in geotechnical and mining engineering analysis and design. It is particularly suitable for addressing complex geotechnical issues that are difficult to solve using the finite element method (FEM), such as complex multi-condition scenarios, large deformations, nonlinear material behavior, and the occurrence and development of instability and failure.
FLAC3D fundamentally inherits the computational principles of the FLAC program and further extends its analytical capabilities into three-dimensional space. The algorithmic background, professional theory, and sequential inheritance relationship with the target industry determine that Itasca FLAC3D generally inherits the advantageous technical features of the FLAC program. However, it is undeniable that the two programs have distinct characteristics in specific technical processing aspects. From an application selection perspective, it is necessary to discern and understand the key differences in methodological significance:
FLAC and Itasca FLAC3D describe physical media from two-dimensional and three-dimensional perspectives, respectively. Clearly, three-dimensional analysis methods can more accurately describe the shape characteristics of the medium, its loading conditions, and the corresponding stress-strain properties, highlighting the fundamental differences between the two programs;
In the modeling phase, real-world physical models have relatively lower requirements for preprocessing techniques for planar models. Therefore, FLAC adopts a simplified modeling method where the overall GRID mesh is first generated and then locally modified to obtain the final mesh structure. In contrast, Itasca FLAC3D offers diverse modeling tools and interface technologies to meet the needs of model construction for different engineering types and complexity levels, such as built-in standard model templates, built-in visualization structured grid tools—Building Blocks, and grid auto-generation tools based on closed geometric models (simplified version of Kubrix), as well as data interfaces for model exchange with mainstream finite element programs like ANSYS and ABAQUS;
The differing focuses of FLAC and FLAC3D in the process of enriching and improving their mechanical model libraries also reflect subtle professional differences in their analytical functionalities. For example, in the handling of saturated-unsaturated fluids, the FLAC program incorporates more accurate soil-water characteristic laws and can consider two-phase water-gas medium flow, which is fundamentally more comprehensive than the empirical theories adopted by FLAC3D. In the creep analysis phase, FLAC3D offers more simulation capabilities than FLAC;
Under specific conditions, the Itasca FLAC3D program can be simplified to the FLAC program. Although FLAC3D was originally developed to describe the mechanical behavior of physical media in three-dimensional space, it also possesses two-dimensional spatial analysis capabilities, such as plane stress and plane strain analysis solutions;
To meet the needs of research on unconventional problems, Itasca FLAC3D has developed specialized technologies distinct from FLAC during its evolution. Notable examples include the addition of a widespread joint model and three-dimensional fracture network simulation technology (DFN) for rock mass structural surfaces, as well as the HoekCave constitutive model developed for mine caving methods. These advancements highlight FLAC3D’s leading position in specific specialized areas on the international stage.