One of the greatest challenges in performing 3D geotechnical numerical analysis is in creating a 3D model of the site. A well-defined model that accurately represents the site topography and boundaries of material layers is essential to producing an accurate analysis. For a site with few material units in which the units are cleanly separated and stacked on top of each other, the modeling process is relatively simple. However, sites may have numerous features such as dykes, ore bodies, or other enclosed volumes of material with complex shapes. Modeling these features and their interactions with the rest of the site geometry can be very difficult with traditional methods, but Material Volume Meshes (MVMs) make it significantly simpler, easier, and faster.

Traditional geotechnical 3D models are represented by regions and surfaces. Regions divide the model into sections from a 2D top-down perspective, and surfaces separate boundaries of material layers vertically, forming a set of stacking layers. Each region-layer combination can be assigned distinct material properties. There are several limitations to this approach, which, when combined together, can make it difficult to model real-world complexity:

1. Regions form completely vertical boundaries, which are often not realistic;
2. Surfaces may not fold over themselves – they must have a single elevation for any given X,Y location;
3. Each material unit to be modeled requires a complete, site-wide new surface to delineate it;
4. Surfaces must not create negative volume layers – they must be sequentially ordered and not cross through each other.

Material Volume Meshes are a new feature of PLAXIS LE that can be used by engineers to avoid these limitations. MVMs are supplemental to the region/surface paradigm, but separate from it. Each MVM represents one distinct volume of material. An MVM is defined by a mesh that specifies the boundary shape of a volume, and it can be assigned almost any material that can be given to a region-surface block. The mesh can be given any arbitrary shape, and, importantly, each one is fully independent from others – the engineer does not have to worry about how the MVMs are spatially ordered, nor incorporating geometry that is not part of the unit or requiring mesh intersection operations with other geometry. Additionally, any part of an MVM that is outside the overall model volume (bounded by the boundary region, and top and bottom surfaces) is automatically disregarded from analysis, which avoids requiring the engineer to perform clipping. The material assignment specified by regions and surfaces is overridden by an MVM wherever the MVM volume is defined.

These properties allow engineers to simply import each unit of geometry from an external source, or model it in PLAXIS Designer, and then transfer it to the PLAXIS LE model. The Material Volume Meshes simply drop in and allow the engineer to advance to the point of having a model ready for analysis more quickly.