While ‘BIM’ has become one of the most used terms in infrastructure development over recent years, it is also often a misunderstood buzzword, including in the underground construction sector.
Most likely, this is due to a divergence between the outward image of BIM and the inner workings of the technologies and systems that are used to create a collaborative BIM environment.
While non-experts may be most familiar with the visible products of a BIM process, such as 3D models, visualisations, or renderings, they may not appreciate where many BIM professionals focus their attention – that is, behind the generated models, where data and information are organised and exchanged through carefully planned workflows. These inter-related hierarchies, i.e., workflows, are the backbone upon which data sharing within a BIM framework is based.
These information hierarchies are powerful processes, developed to allow owners, engineers, and contractors to better collaborate and to make the planning and delivery of infrastructure and tunnel projects more efficient.
Structured workflows improve the transparency of project data and information and therefore allow it to be shared quickly and accurately between partners.
Yet, while new BIM technologies allow project parties to come closer together, it is the terminology used – the jargon employed, the acronyms themselves even – that can lead to differences in understanding
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By GlobalDataAs a challenge that can exist from the outset it consequently presents hurdles to overcome on the way to implementing BIM within any given project.
A simple question therefore arises: What is BIM?
CONCEIVING OF BIM AND ITS BENEFITS
The infrastructure sector is enormous, the assets it creates are many in type and scale, and vast supply chains facilitate their planning, design, construction, operation and maintenance. Different perspectives across the industry and among its players lead to a diverging understanding of what BIM is, and therefore answering what is BIM is important.
This is not helped by the fact that BIM, i.e., Building Information Modelling, has differing definitions depending on where one looks.
The tunnelling sector commonly uses definitions from the International Organization for Standardization’s (ISO) 19650 series, ‘Organization and digitization of information about buildings and civil engineering works, including building information modelling (BIM): Information management using building information modelling’. In these standards, ISO defines BIM to be: “The use of a shared digital representation of a built asset to facilitate design, construction and operation processes to form a reliable basis for decisions.”
In contrast, the German Tunnelling Committee (DAUB), in its more tunnelling-focused document ‘BIM in Tunnelling’, defines BIM as the following: “[A] collaborative method based on digital models for the design, implementation and operation of facilities over their entire life cycle.”
While these definitions are similar, they are not the same. Moreover, description of BIM as a “use of a shared digital representation …” or as a “collaborative method” can further obscure things. These broadly worded definitions make it difficult for non-BIM professionals to immediately understand what BIM is and, in particular, what it is when utilised within a particular sector, such as developing underground space and undertaking tunnel design and construction.
BIM simultaneously describes an information management process, i.e., how information is created and shared within a project and who can access and modify information at which project stages, as well as the models (2D, 3D, or otherwise), their application, and the software that are used to do so. To some users, BIM therefore represents the entire cyber ecosystem developed for an underground engineering project, while for others, BIM may only describe some of its parts.
Much also relies on what a project sponsor wishes, and how they view BIM in their plans and future operations. For example, smaller projects without sufficient funding may only include simple BIM software with no overarching organisation plans. Larger infrastructure projects, in contrast, may be mandated to use BIM in all aspects of the collaboration and delivery of a project, and develop detailed digital environments for all aspects of a project. Project participants on smaller projects, may therefore view BIM as different from those on larger projects, though neither would be inherently wrong in their views.
As such, BIM, in its current state, exists at different levels of maturity across different projects, and therefore it means different things to different project participants.
HISTORICAL PERSPECTIVE
BIM, like several other technologies or methods used in the tunnelling world, has its origins outside of the industry. While the concept of BIM has existed in some form or another since the beginning of the use of computers in architecture and engineering (A&E), introduction of what we now know as BIM to the A&E field has its origins in the mid 2000’s as software manufacturers, such as Autodesk or Bentley, began to focus more on developing BIM-specific software that allowed users to integrate more design information than simply 2D or 3D geometries within models of objects/ structures.
Early adoption of BIM within the tunnelling industry often centred around the selection of specific uses of BIM oriented software, such as 3D modelling or tasks such as clash detection, rather than the implementation of a project-wide information management framework. Some early tunnel projects that adopted BIM include the Central Subway project in San Francisco and the Crossrail project in London, both of which Gall Zeidler Consultants was involved in.
For the Central Subway project, BIM was used extensively for the station design phase during 2008- 2010. However, the implementation of BIM for design was limited to the final structures. Use of BIM did not extend to the construction phasing and sequencing, nor did it require the contractor to implement BIM in its construction planning, which was a missed opportunity for continuity of the deployment of the BIM approach and benefits to the project.
The UK Crossrail project began development of the project wide BIM environment and various other BIM processes in 2008, prior to the 2012 UK government mandate that required BIM processes to be implemented for all government funded mega projects. The use of BIM on Crossrail for construction planning was instrumental in addressing construction challenges and implementing resolutions.
Due to the success of BIM in early projects such as the above, the adoption of BIM has become more widespread in the industry, especially in countries like the UK in which BIM has been mandated for state-funded projects. An example of another project implementing BIM immediately following Crossrail is the Vauxhall Station Upgrade project, also in London, for which Gall Zeidler Consultants provided 3D station design services.
CURRENT USE
By now, it has become more standard to require BIM used on major national and international tunnelling and underground construction projects. Examples of its use include: Ontario Line Subway, in Toronto, Canada; the HS2 project, in the UK; the Grand Paris Metro, in France; the Brenner Base Tunnel between Austria and Italy; and, the BART Silicon Valley Phase II Extension project in the US. While these projects specify the use of BIM to some extent, its integration as a core management concept varies greatly.
One of the most successful implementations of BIM in tunnelling is for the HS2 project, in which Gall Zeidler Consultants has developed several designs. In HS2, all information is exchanged on a central project database, known as a Common Data Environment (CDE), and design is being performed in object-oriented 3D models. This includes all the added benefits, such as clash detection between disciplines at early design stages, or automatic generation of 3D models. This integration of BIM within a mega tunnelling project represents a significant leap forward to what was done in comparable projects just a short time ago.
FUTURE OUTLOOK
Regardless of its level of integration, software for BIM has advanced to the extent that the benefits it offers can no longer be overlooked. BIM software and information management approaches have reached a level of sophistication that allows owners, consultants, and contractors to run tunnelling and underground projects entirely digitally, from design through construction and finally onto asset management.
Nevertheless, certain hurdles still hinder BIM’s fullscale adoption across the tunnelling industry.
The first hurdle, and certainly the most important, is lack of familiarity with BIM. Successful integration of BIM within a project requires all participants to address preconceived notions of typical project workflows.
For example, 3D design requires significantly more front-end coordination than 2D design where clashes between disciplines are ‘weeded out’ throughout the design process, all the way up to construction. In contrast, 3D design requires all disciplines be coordinated at all design stages.
Similarly, 3D models take more setup time than 2D models.
Issues such as these contribute to the perception that implementing a BIM platform will result in higher costs. Although this may be true for the initial set up, successfully implementing BIM can reduce overall project costs – achieving savings by eliminating conflicts and expensive corrections during construction, achieving better coordination with stakeholders, and enabling more efficient construction planning, especially when using 4D and 5D design processes.
Another major hurdle is that existing BIM software is not always tunnelling-focused. While existing software can be, and is, used successfully in underground projects, not all BIM modelling software can, for example, properly model linear structures along curved alignments, e.g., tunnels. Similarly, data exchange between different software packages can often lead to difficulties, as tunnelling-specific file formats are rare.
While the industry tackles these hurdles, it is also addressing the lack of familiarity with BIM by moving towards a larger degree of standardisation for use of BIM in tunnel projects. The ISO 19650 series, although not tunnelling-specific, was published in 2018 and has become the standard information management framework in the industry. Similarly, DAUB’s guidelines were only published in 2019 and were followed up with additional material.
The International Tunnelling Association’s (ITA) Working Group 22, Information Modelling in Tunnelling, (of which a co-author of this article is a contributing member), has developed its first tunnelling-specific guidelines for the adoption of BIM, focused on bored tunnelling.
Similarly, the lack of specificity in BIM software for tunnelling projects is being addressed by the industry as well as by the software developers. Newer versions of modelling software are increasingly incorporating the ability to properly model stationing (chainages), and building SMART is developing tunnel-specific non-proprietary file formats under the IFC-Tunnel project to better exchange data between different software packages.
Another major shift in the industry is coming in the form of adopting BIM for Asset Management purposes, with more owners expecting to use ‘digital assets’ for post-construction phase decision-making and control.
This becomes a ‘digital twin’ of the asset, especially if, post-construction, the model gets updated with ongoing information flows relevant to support better maintenance and operation of the structure in service.
BIM is a broad topic. It encompasses many ideas, concepts, and technologies. With the increased trend toward digitisation across not just tunnelling, but all industries, BIM concepts will almost certainly become engrained in many, if not all, tunnelling projects sooner rather than later. Concurrently, as software continue to progress, and as the tunnelling industry becomes more knowledgeable, how BIM is viewed and used will continue to evolve.
