DIGITAL/BIM | TECHNICAL
The paper closes, in Section 6, with a discussion
of the presented BIM framework, its limitations and an outlook to future developments. Information for supplementary material can be found in the end of the paper, where an example BIMGM is included as an .ifc file with a corresponding exemplary attribute list. The concepts about BIM ground modelling discussed
here were developed in the context of the project described and other real-world projects, and also the authors’ involvement in two working groups on BIM ground modelling (DAUB and IFC Tunnel). The rapid development of BIM in the past years has
produced a vast amount of (sometimes redundant or even conflicting) terminologies and definitions. While this paper aims at using consistent and clear terminology, including an extensive glossary of definitions would be out of the scope of this study. References to synonymous terms are given throughout the text, but the reader is for example referred to Borrmann et al. (2019, pp.575–578) for general BIM glossaries and to DAUB (2019, pp.40–41); buildingSMART (2020, pp. 51–52); Molzahn et al. (2021) for BIM ground modelling/ tunnelling-specific glossaries and terminology definitions.
2. BACKGROUND 2.1 State of the art Digital ground models became state of the art in infrastructure projects in the last decade, as an additional or alternative way to represent ground conditions. Databases and digital data exchange formats replace hardcopy documentation of factual data, i.e., observations and measurements that describe the conditions at certain locations. Several countries established a common practice
and standardised formats, e.g., AGS (Bland et al., 2014) in Great Britain and several other countries or DIGGS (Cadden and Keelor, 2017) in the US. Conceptual data models, e.g., by OGC (GeoSciML (OGC, 2017), GroundWaterML (OGC, 2021)) are frequently used in national geological surveys, infrastructure owners or other larger organisations that need to work with extensive geoscience-related datasets. The general application of ‘Engineering Geological Models’ has recently been described by a guideline of the IAEG Commission 25 (see Baynes and Parry (2022) and Parry et al. (2014)) and can include digital 3D models (observational models), describing the expected distribution of relevant aspects in the model space, based on geological conceptual models and are used to derive geotechnical models for specific use cases. Traditionally, these models were described by reports, maps and sections which can now be linked to and extracted from digital models. Nevertheless, there are no commonly agreed
standards for the digital exchange of geological and geotechnical data in infrastructure projects. In the last two decades, 3D ground models were
implemented as a helpful and efficient tool, and many examples around the world are described in literature,
e.g., for alpine tunnels (Cudrigh-Maislinger, 2018), metro projects (Huang et al., 2022) and hydropower (Weil et al., 2019), and further developed in ongoing research projects (e.g., Gächter et al. (2021)). However, solutions and data structures for these projects were mainly developed independently by their authors and model users and do not follow detailed definitions of requirements by project owners. This implies frequently enormous efforts for digitalisation, transformation and mapping of information between different formats and software. In the DACH countries (Germany (D), Austria (A),
Switzerland (CH)), the BIM method has been applied on many infrastructure projects, being pushed by government agencies (BMVI, 2022) and large infrastructure owners, with the intention to establish the method as ‘common practice’. Even though ground models were not a main focus in most cases, this development triggered a transition towards digital methods and 3D modelling being applied in the field of engineering geology and geotechnics. With both the BIM method and digital ground
models becoming more accepted, the demand for standardisation and clear definitions has become obvious. Many national and international working groups have formed to address these requirements and publish recommendations. Several initiatives are mentioned below, selected either because the authors are personally involved or their output was considered in the approach used in the tunnel project case study here discussed.
2.2 Current developments and standardisation All initiatives described below started with definitions of requirements and have different backgrounds: From focus on specific needs in tunnelling (DAUB, IFC Tunnel), over the general field of geotechnics and earthworks (DGGT, IFC common schema covering geo- technics in IFC 4x3), to a more global scope considering interfaces to mining and resources, oils and gas, environmental and other geosciences (OGC).
Below, figure 1: Overall BIM Model structure (modified after DAUB (2020)). The BIM ground model is a discipline model which gets its input from domain models and can either be separated contextually into sub-discipline models and/ or geographically into sub-models
Coordination model Discipline models (DM)
contextual separation sub-DM1, sub-DM2 ...
geographical separation sub-model1, sub-model2 ...
Object groups Objects
Borehole Sub-object Sample Sub-object ... Sub-object Domain models
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