The visualization of geological structures (rock contacts, fractured zones, faults, dykes, etc.) is essential for the analysis of rock masses before and during the excavation of large underground caverns. A relatively light methodology was developed for model construction using only a database and AutoCAD® or 3ds Max®. This simplicity allows having step by step models, from investigation to construction phase. The benefits, presented through case studies, are obvious for geological interpretations but above all for rock mechanics and civil engineering, due to the simplicity of visualization.
Except on large and long-term projects for which the investment is possible, medium- or smallsize projects generally do not invest on 3D geological modelling (3D being taken here in the sense of visualization or representation of geological features). Too often, geological input data stay, in the best cases, at a 2D level and in the great majority in paper reports At present, geological software programmes can be categorized into four types: - oil & gas software programmes, covering a wide range of activities, from geophysical survey to wireline logging; they are often restricted to oil & gas industry since rather expensive. They are more adapted to sedimentary rocks with sub-horizontal structural features than to hard rock environments with sub-vertical features (joints, dykes, etc.), - mining software programmes, nowadays extremely powerful and covering much more than the geological aspects; the market of mining software is mature and software programmes have been developed for precise goals; however, these big software programmes are difficult to handle, need a dedicated training and finally cannot be used by anyone. They are now easily run on standard PCs, - tool-box programmes, generally composed of several (even many) independent modules, sold separately; these software programmes are relatively easy to use and thus represent good tools for field and/or desktop geologists; 2D is common but 3D is less achievable; they can be run on PCs and even laptops, - imagery software programmes, used for earth sciences and medical sciences; they represent the uppermost visualization systems in 3D but need quite big computers and powerful graphic cards.
Very often and especially during investigation and design phases, the use of a geological software programme remains too often a constraint instead of being a help for a project team. Reasons are multiple, and among others one can itemize the following ones: - using the software programme is uneasy (if not difficult) - software programmes are good to model geology but less efficient to represent complex underground works, requiring frequent import from and export to AutoCAD® - too often, models can only be read using the modelling software itself which requires all users to be connected or to have a licence of the software on their computer - 3D models are not accurate in term of image quality and rendering - the cost of geological software programmes (licence or lease) can be prohibitive for small projects.