TECHNICAL | DIGITAL/BIM
potential contractors than done by classical 2D-based
planning. Geotechnical baseline conditions and the included uncertainty/expected variations described, e.g., in a Geotechnical Baseline Report (GBR), according to FIDIC Emerald book can be represented in a ground model. By delivering a BIMGM as well as domain models
(native formats and software, as discussed earlier in Section 3.1 and Figure 1), the complete geotechnical and geological information can be included but also represented in a manageable format.
Below left, figure 3: Visualisation of the exemplary BIM ground model that is provided as supplementary data (BIMGM.ifc). The model contains all three sub-discipline models: Geotechnical Model, Factual Data Model and Geotechnical Synthesis Model
Below right, figure 4: Concept of the BIM- geotechnical model with five exemplary
geotechnical units. The left attribute box shows exemplary attributes for a geotechnical model with well-known ground properties; the right attribute box shows exemplary attributes for a geotechnical model without exact knowledge of the distribution of ground properties
4. BIM GROUND MODEL: SUB-DISCIPLINE MODELS
4.1. Overview As discussed in Section 3.1, the BIMGM can be separated into several sub- discipline models. In this section, three such sub-discipline models are presented: the Factual Data Model; the Geotechnical Model; and, the Geotechnical Synthesis Model. The authors note that the three sub-discipline models
do not represent the overall best approach to a BIMGM but were created in the planning phase of the case study of Angath Tunnel (discussed in Section 5.) Further, the authors add that while the approach fitted the requirements of that case study, other projects might call for a different choice of sub-discipline models. The basic distinction between ‘not-interpreted’
or ‘factual’ models (here, the Factual Data Model) and ‘interpreted’ models is supported by all working groups referred to earlier, and is in line with the classical approach of data exchange and reporting (e.g., Geotechnical Data Report versus Geotechnical Interpretive Report and GBR, according to FIDIC Emerald Book (FIDIC, 2019)). In addition to the sub-discipline models mentioned,
several others – especially interpreted models – are conceivable in the context of BIM ground modelling (e.g., a hydrogeological model, material recycling model, etc.,). For example, it is recommended to have a geological model ready before a geotechnical model is
Geotechnical model
Geotechnical unit Sediment cover
Unterangerberg formation weathered
Unterangerberg formation Damage zone of the Unterangerberg formation
Cross section Cross section 1
created (Parry et al., 2014), but in the project reality it is not always necessary to implement each sub-discipline model as a BIM model (even though it may exist in the native domain model). A BIMGM must always be accompanied by a
geotechnical report that describes its purpose, concept, modelling approach and the classification that is represented by it. It can either replace other documents, like longitudinal- or cross-sections, or can be used to extract them. Technical details of the implementation of the BIMGM should be given in the BIM Execution Plan (BEP). In this paper’s supplementary material, an exemplary
BIMGM is given as an .ifc file (IFC 4X1) including all three sub-discipline models (Factual Data Model, Geotechnical Model, and the Geotechnical Synthesis Model). The BIMGM is accompanied by an exemplary list of model objects and attributes, defining the BIMGM’s semantics as given in the beginning of a project in the BEP. An overview visualisation of the exemplary BIMGM is given in Figure 3 and further information on this is given in the subsequent subsections and Section 5. The content of the exemplary model is only for representative purpose and not directly based on the real BIMGM of Angath Tunnel.
4.2. Factual Data Model The Factual Data Model represents the BIM version of the content of a ‘Geotechnical Data Report’. In the planning phase of a project, the model contains the information that has been collected during site investigation (e.g., borehole data, results from in-situ and lab testing, geophysical investigations, documented outcrops, etc.,). During construction, the scope of the Factual Data Model is then extended to serve as a database for documented geotechnical observations (e.g., tunnel face mapping, collected samples from the investigation, etc.,). The exact line between ‘factual’ and ‘interpretation’ is
not clear, as any description of natural material implies a certain degree of interpretation. The same applies to deriving geotechnical parameters from measurements
Factual data model Boring A-KB 01/21 A-KB 02/21
high investigation density/ well-known conditions/ high-resolution model
Attribute
Density [g/cm3 Friction angle [°]
]
Cohesion [MPa] ...
Value
2.6 38 0.8
... GeotechUnit 1
deep tunnel/ high uncertainty/
GeotechModel
low-resolution model Attribute
Rockmass type 1 [%] Rockmass type 2 [%]
Rockmass type 3 [%] ...
50 20 15
... Value
Geotechnical synthesis model
GSM_Geology Unterangerberg formation Damage zone of the Unterangerberg formation
BIMGM.ifc
GeotechUnit 2
GeotechUnit 3 GeotechUnit 4
GeotechUnit 5
16 | October 2023
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