TECHNICAL | DIGITAL/BIM
Working groups are formed by participants from
federal agencies, infrastructure owners, consultants, contractors and software developers. The developed concepts vary from more general description of model structures, object catalogues and example property sets to detailed data models (e.g., in UML) and definition of extensive attribute lists representing the definitions in national, EN and ISO standards for ground characterisation and geotechnical testing. ● The German branch of ITA released recommendations for BIM in tunnelling (DAUB, 2019) and model requirements (DAUB, 2020) that have been well- adopted by the industry. The latest recommendations in this series was published in autumn 2022 and covers geotechnics and ground models, with definitions of use cases, model structure and typical property sets elaborated by a working group of geologists, geotechnical- and tunnel engineers (DAUB, 2022). The model structure described below (see Section 4) was developed based on work within this group.
● The German DGGT published detailed recommendations and concepts for model structures of geotechnical models. Data catalogues with definition of attributes and property sets have been published recently (DGGT, 2022), covering both factual and interpreted models (homogeneous areas (German: ‘Homogenbereiche’) according to (DVA, 2016))
● The IFC standard format for the exchange of BIM models in OpenBIM environments is currently being extended to infrastructure models (buildingSMART, 2022), including tunnels. The latest released version IFC 4x3 already included a simple schema for interpreted geotechnical models and boreholes. In the course of the development of conceptual models for IFC Tunnel, an extension of this schema is planned to cover factual data (observations, measurements) with links to existing exchange formats for factual data as well as different types of interpreted models, several concepts to treat uncertainty in modelling, and an extension of the IFC format to realise voxel representations. A focus is on the concepts to link the definition of expected ground conditions to the tunnel alignment/ design model as realised in the example model (see Section 4). The German section of buildingSMART recently published literature and a similar schema in German language (Holsmölle, 2022).
● The Open Geospatial Consortium (OGC) just launched an initiative to extend its schemas to geotechnical models (OGC, 2022), mainly driven by the French MINnD group. This initiative is coordinated with buildingSMART international and intends to maintain a common concept for the geology/geotechnics domain that is implemented by both IFC and OGC standards in future. In addition, a collaboration with the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE) is expected.
14 | October 2023
ISSMGE recently formed Technical Committee 222 (Geotechnical BIM and Digital Twins) as a forum for members “to disseminate and exchange knowledge and practice” on BIM and DT in geotechnics (ISSMGE, 2022).
Based on published materials and discussions, it can be concluded that the above-mentioned groups developed similar concepts for ground models, even though differences in terminology, focus and presentation of the results exist.
3. CONTEXTUALISATION OF THE BIM GROUND MODEL Whereas the previous section presented background literature, state of the art industry applications and government guidelines, this section sets the BIMGM into a hierarchical context within a project’s bigger BIM model structure (see Section 3.1) and within a building’s life cycle (Section 3.2). Based on this, typical expectations for a BIMGM from the client’s perspective are defined (Section 3.3).
3.1 Integration within the overall BIM structure Following the proposed structure by DAUB (2020), the BIMGM is a ‘discipline model’ and “contains specific information from the single specialist designer in charge of their discipline”. (This discipline model corresponds to the ‘Partial Model’ of Borrmann et al. (2019)). It has to be noted, however, that a ‘BIM discipline
model’ does not necessarily contain all the available information but is rather a filtered and specifically prepared model to be integrated in the overall BIM (coordination) model. This can be compared to typical plan preparation, where finalised plan documentation does not contain all ‘working data’ that were necessary and gathered to enable their creation. The working model that is used by modelling personnel would only be called the ‘domain model’ and it is usually not included in the final BIM model. The amount of information that goes from the domain model to the ‘BIM discipline model’ must be defined individually for each project, based on necessary requirements of all involved parties and the long-term intended application of the BIM model. The BIMGM is one of the discipline models in a
tunnelling project, such as excavation and support and systems. Hierarchically, the discipline model is located below the ‘Coordination Model’ and above the ‘Object Groups’ (Figure 1). The discipline model itself can be subdivided into
‘sub-discipline models’, which refers to a separation into contextually specific models (e.g., a factual data model, a geotechnical model, a hydrogeological model, etc.,) and into ‘sub models’, which refers to geographically separated parts of one sub-discipline model (e.g., multiple sub-models for multiple construction lots of one bigger project).
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