IFC-Based Product Modeling for Tunnel Boring Machines

The Industry Foundation Classes (IFC) standard has proven to be very successful in the exchange of data used in Building Information Modeling (BIM). Although the main focus of IFC is the definition of building entities, such as walls or columns, the IFC specification also includes more abstract classes to define relationships, properties, elements or resources. Based on the framework of classes as defined by current IFC standard, this paper explores the possibilities of extending the established IFC class hierarchy to additional engineering fields, in this case, mechanized tunneling and underground engineering. In particular, a set of new IFC-compatible classes are introduced to model tunnel boring machines (TBM). Additionally, a work flow is described to preprocess a TBM model designed in common CAD software in order to store it in a Product Server System. Finally, a case study of an underground engineering project is presented that uses the introduced IFC classes to model a TBM and employs a software tool to visualize IFC-based models. these elements, one possibility would be to represent these elements by so called proxy classes. A proxy class can be understood as a container defined by associated properties (BuildingSMART 2011). Furthermore, a geometric representation can be assigned to it. Therefore, proxy classes can be used as substitutes for each element which is not captured by the IFC notation. Indeed, this could be an appropriate solution if only few undefined elements exist, but to represent a TBM many elements must be modeled. A huge number of proxy classes could lead to conflicts regarding element identification, since different team members could use different names for identical or similar elements. Additionally, individual aspects of a tunneling project, for example. the ground, the tunnel or the TBM should be integratable into one IFC file. If each element of each aspect is represented by seperate proxy class this can lead to great confusion. By using seperate models (e.g. a tunnel model, TBM model or ground data model) each aspect of tunneling can be easily identified. Therefore, the individual elements of a TBM were added to an IFC-based product model, in order to exchange important information easily and to provide this information to team members to support their planning tasks. At this point it should be emphasized that, although the IFC standard has been extended by new IFC classes to model mechanized tunneling (TBM), it is not the aim of this research effort to standardize this extension and to include these specific classes into the current IFC notation. Rather, these classes have been defined and implemented to simplify their use and enable the exchange of data between software components (CAD programs, simulation packages, visualization components, etc.) Thus, the major aim of the proposal presented in this paper is to employ IFC technology to exchange (and not store or process) relevant underground engineering information. This is the strength of the current IFC standard, as witnessed by the strong support of major engineering software developers. That being said, should the proposed IFC classes establish themselves in the future as being well-suited to modeling underground engineering projects, the authors will not, of course, hinder the IFC community from adapting ideas taken from this proposal.