As the tunneling industry continues to adopt Tunnel 4.0, digital twins of the tunnel construction site are becoming standard requirements for tunneling projects. However, the benefits of these remain unproven to many practitioners. This article discusses the various implementations of digitalization and describes efforts to combine all data types to analyze the relationships between influences, predictions and performance in a single digital platform. This includes data pertaining to investigations, design, construction, monitoring and postconstruction asset performance and management. Based on 16 years of global tunneling projects this article aims to quantify the tangible and intangible benefits of such systems. Using a number of real examples, this article describes where opportunities were taken and where they went unrealized. Challenges and considerations for both procuring and developing these digital twins are also discussed.
Digitalization is the use of digital tools during the entire life cycle of tunnel construction from concept, design and planning, construction and commissioning, operation, maintenance, expansion and reconstruction. These tools can enable automation of manual tasks and active data management, leading to time/cost savings and increased accessibility/transparency, thus promoting risk reduction and enhanced collaboration and communication. Ultimately, the proper management of data on a business level utilizing the advancements in cloud data storage and processes provides numerous opportunities for improved business as they evolve.
McKinsey & Company claimed that construction lags other engineering disciplines in research and development (R&D) expenditure and has a poor level of productivity with frequent cost and time overruns (Dobbs et al., 2013; Agarwal et al., 2016). In 2017, McKinsey & Company reported that five key areas will revolutionize the industry over the coming years (Barbosa et al., 2017):
- Higher-definition surveying and geolocation.
- 5D building information modeling.
- Digital collaboration and mobility.
- The Internet of Things and advanced analytics.
- Future proof design and construction.
Barbosa et al. suggested that when coupled with four key principles — transparency and risk sharing in contracts, return on investment orientation, simplicity and intuitiveness in the design of new solutions, and change management these technologies — will deliver productivity increases to close the gap with manufacturing and the general economy currently standing at 50 and 80 percent, respectively.
Foundations of digitalization
What is required in order to apply digital tools to tunnel construction?
Spreadsheets and word processors have replaced penand- paper methods with digital tools and have resulted in an explosion of documentation, which in some cases has been more hindrance than help. What digitalization is looking for is standardization of nomenclature and agreement of a common data model; what shall we record and how shall we record it? Furthermore, an agreement on communication protocols is needed:
- Means of ‘moving’ data — do systems communicate with other systems directly or is an agreed communication standard required?
- Data access — who can access and use the data? How to ensure data is kept accessible to engineers so that creativity is not stifled while ensuring that it is not used improperly?
- Data use and edit tracking — is record-keeping on both the use of, and modifications made to the data to track what has happened to the data since the raw information was recorded?
One could be forgiven for thinking that digitalization in tunnel construction is a recent development. In reality, digital developments have been progressing gradually since the late 1980s and early 1990s, which saw the rise of word processing, spreadsheets, numerical analysis, mail programs and the transition from hand-drawing production to computer-aided design (CAD).
Even in the late 1980s engineers recognized the need to standardize the way in which production was recorded. On the Channel Tunnel, a coding system nicknamed the “Black Ball” charts defined two-part codes for how time would be classified on shift reports. This classification agreed early in the project enabled the production manager to evaluate time and identify objectively where time was being lost and where there may be opportunity to increase productivity on the project.
At the same time, engineering geologists of the Association for Geotechnical and Geo-environmental Specialists met to agree on a standard for communication of ground investigation data digitally and avoid the need to painfully digitize paper boreholes. This became highly effective and contributed to a shortening of the time between drilling and data analysis, a key requirement on many tunnel jobs where alignments would change during design. The proliferation of this standard, first in the United Kingdom and later in Australia and Asia, met the need for ground investigation databases.
Original databases consisted of simple GIS applications to host paper-based historical records on a map interface and often made use of a number of simple map products. More extensive database applications focused on geological data, including logging, in situ and laboratory tests. The author helped to create one of the first large borehole databases on the Channel Tunnel Rail Link (HS1 in the UK) hosting more than 3,000 boreholes. In an industry first, this database resource was made available to tenderers. To the authors’ knowledge, this has not since been repeated.
Many of these early systems had extensive graphing capabilities but little in the way of geological interpretation. On both HS1 and the Thames Water Ring Main between 1993 and 1995, engineers made computer connections between the borehole databases and other applications, including geostatistical analysis software and CAD. Before the advent of any application, programming interface (API), these connections involved generation of scripts that could be run with the associated application to automate the production of drawings and sections, or to automate the entry of data into the geostatistical analysis. The repeatability of this semi automation enabled up-to-date geological sections and layers to be created at any time with minimum additional work.
Benefit 1: Data standards and ease of communication, analysis and updating of data.
Equivalent central systems did not exist for instrumentation and in the early 1990s instruments were regularly downloaded to spreadsheets and manually processed. This was often a laborious task and the constant oversight meant that it had to be repeated thousands of times during a project. Even at the time of London Docklands Light Rail and Limehouse Link & Heathrow Express in the early to mid-1990s, most data was processed manually. Only on the Boston Central Artery (Vaghar et al., 1997) did central systems with automatic processing start to get employed, in this case a response to the sheer scale of the monitoring required.
The Strategic Sewage Disposal Scheme tunnel data management system
In the mid-1990s one project did more than most to accelerate the move to digital systems. The Strategic Sewage Disposal Scheme (SSDS) was a fast-track hard rock tunneling project in Hong Kong under the harbor that was later renamed Harbour Area Treatment Scheme or HATS 1 (Endicott, 2014). The job comprised 25 km (15 miles) of tunneling east-west across Kowloon with a spur toward the east end of Hong Kong Island. The system was connected by 15 shafts with depths up 140 m (450 ft) which were awarded to two advanced works contracts. Six tunnels were let a year later in four contracts and were to be driven using open-gripper TBMs with probe and grout drilling capabilities with either a segment erector (but no tail shield) or a secondary cast in situ concrete lining. The majority of the tunnel contracts were awarded to a single joint venture.
The initial advanced works contracts suffered delays due to ground water and poor ground and put the tunnel contracts into immediate delay. Even with acceleration measures implemented, further tunneling difficulties made it clear the contract was heading for dispute, particularly as the program was fast-tracked.
The client’s engineering team recognized the importance of maintaining auditable real-time records across a complex team, so efforts were made to create a common data environment (CDE) for tunneling that would standardize the way in which data was being collected across the many site teams. These were the early days of the internet and many different methods were being used (Lotus Notes, Quattro Pro, Excel, Word, various email systems but mostly just paper). This tunnel data management system (TDMS) was implemented with the backing of the project team using a system built on Visual Foxpro, an early database environment.
The aim of the system was to collate as much information from the various project stages and bring it all together into a single digital environment. This covered all the known influences on the job from ground conditions to environmental constraints, predictions or progress rates, geology and inflows to the recording of activity time and associated records (Fig. 1).
Monitoring of instrumentation was important to ensure that there was no damage to adjacent infrastructure and this was all housed in the same system as the production data. This defined the project information cycle.
In 1997, the contractor ceased work claiming impossibility and ultimately the joint venture (JV) was terminated. The shaft contractor was granted a change order to look after the sites and existing tunnels. Both the client and JV engaged lawyers and the client tendered for replacement contractors.
The TDMS system that was implemented built on the Channel Tunnel (Black Ball Code System) and tracked every 10 minutes on all the main tunneling activities through to the end of the project. Qualitative and quantitative records were linked to these activities covering all drilling and grouting, excavation, mapping, water inflow measurements and instrumentation and some 50,000 photographic records throughout the course of the job all perfectly audited and cross referenced as the job proceeded.
With the specter of arbitration hanging over the project and both sets of lawyers scrutinizing every action of the engineer and client on the replacement contracts, it was critical that all the records were faultless and instantly available such that any need to evaluate extensions of times and claims were backed by evidence that could not be disputed. The data from the systems was used to close out claims on the replacement contracts quickly. With data agreed to at the time and digitized in the end, there was no disputing the records and only the need to agree that the method of evaluation and quantification that would need to be defended in the arbitration with the original contractor.
The arbitration took place in 2000 in the International Arbitration Centre, presided over by an arbitrator from the United Kingdom. One tennis playing member of the legal team described the comprehensive nature of the win as being equivalent to 6-0, 6-0, 6-1.
Benefit 2: Save time and money arguing about the data. Successful litigants are often those with the best data.
Data to build on
The SSDS was just one part of a larger scheme to clean up Hong Kong waters. The HATS phase 2 was designed between 2002 and 2008 and comprised a further 25 km (15.5 miles) of tunnels built around Hong Kong Island at depths of 140 to 170 m (450 to 560 ft) below sea level. Water inflow and grouting as well as ground support requirements were a key factor in the planning and the client drilled several guided boreholes to follow the alignment at depth. Lugeon tests were done in places but these were difficult given the length of the boreholes.
The designers were provided all the information in the phase 1 TDMS and relied on this more than 80 precent for their estimates for probe and grout hole drilling and grout quantities (Endicott, 2014). Ultimately provisional quantities were reported to have come in at within 5 percent of the predicted amounts.
The availability of reliable, accurate and detailed records from the previous works helped to de-risk the project for both the client and contractor (Fig. 2).
Benefit 3: The data has value. Look after it and use it on future projects to reduce business risk.
Response to risk
The 2004 collapse of the Nicoll Highway, added to other tunnel-related events, led the International Insurers to demand an overhaul of the tunneling community’s approach to tunnel risk. The Joint Code of Practice published with the British Tunneling Society and later the ITA laid out requirements for active risk management of tunnel projects and for constant review of risks as tunneling proceeded. By 2005, the Hong Kong government, recognizing the value of the TDMS, implemented a requirement for a TDMS system in all future tunneling works in Hong Kong as part of its response to the global joint code of practice.
This was later followed by the Mass Transit Railway Corp. (MTRC) in its projects from 2009-2016 (Maxwell, 2014). The merger between the Kowloon and Canton Railway (KCR) and the MTRC into a single private railway developer meant that politically some independent oversight was required to ensure that the public railway was constructed within acceptable financial, environmental and technical criteria. Maxwell GeoSystems was tasked with providing an independent monitoring and provision of a central database for the presentation and analysis of monitoring results. For the first time, response to alarm events could be made via online blogs (a very recent development at the time), which significantly reduced the time to action and close events on the project. As well as being a time-saving tool at the engineer level, confidence among senior management increased as a result of this transparency.
One welcome consequence of the implementation of the independent consultant was the ability to negotiate more favorable project-wide insurance at an owner level. The exact reduction is not known since many factors were conflated, however this is understood to be 0.1-0.2 percent of the construction value (pers comm A. Morris).
Benefit 4: Demonstrate machine-assisted active risk management that is data driven with less reliance on human systems and potentially benefit from cheaper insurance.
With monitoring playing a more important role, instrumentation providers rolled out a number of data-management applications. Often these were downloadable desktop programs linking to web databases or local databases with web portals. By 2010, most were moving fully to the web.
Monitoring was not just focused on the geotechnical and structural. Production staff started focusing on the machines themselves with dataloggers being applied to TBMs, drill jumbos and probe drills, and feeds sent back to engineers for review.
Everyone had their own excellent data, but accessibility across disciplines was limited. Engineers were operating in silos. A TBM pilot was still highly likely to be tunneling based on a printout of a geological section on the wall of his/her cabin that had not been updated since the start of the job. A geotechnical engineer looking to predict settlement could not easily get access to TBM face pressure or muck balance details. Sinkholes and blowouts remained common.
The rise of GIS helped communicate at least the positions of the machine to users, but GIS functionality at the time was not well-suited to the input of streaming data.
Around this time, tunneling started to push the boundaries of what could be achieved and larger machines started to be designed. Reflecting the increase in data volumes and connectivity, there was a proliferation of systems to cover all parts of tunneling from segment design and manufacture, TBM monitoring, robotic total stations, automatic monitoring both wired and wireless and the advent of remote monitoring from satellite to tunnel laser scanning. The data was hugely useful, but each system was different, segregated and with no means of interoperability and intercommunication. Silos continued.
A big change in the approach to data during the construction phase occurred during a large tunnel project in Singapore. As always, issues on prior projects are great motivators and Phase 1 of the Singapore Cable tunnels had suffered a delay due to settlement of a highway bridge. By this time, the TDMS platforms in Hong Kong were connecting production and instrumentation monitoring in a single platform (Maxwell et al., 2015b). Singapore Power Assets took the unusual approach to implement a project-spanning digital platform as part of a partnering for risk approach. Each contractor was asked to contribute to the cost of the platform and manage through a joint steering committee of both contractor and client personnel.
The system covered prediction, progress and real-time tunneling parameters, hazard and risk and monitoring, and was fundamental to the daily tunneling review meetings. Importantly, the client was extremely forceful in insisted that there was a single source of truth on the project and that all meetings used the system as a basis for assessment. The highly transparent and complete review of all data at all times was reflected when comparing the rate of occurrence of sinkholes to historical projects (Table 1).
Similar combined systems were implemented on the Kuala Lumpur Metro Phase 1 and 2 and can be compared to the earlier tunneling of the Stormwater Management and Road Tunnel (SMART) tunnel (Siow, 2006) (Table 2). Much of this is owed to the use of the variable density slurry machine technology. However, advanced warning of approaching conditions and the immediate information of ground response assisted the control process (Maxwell et al, 2015a).
Benefit 5: Consolidating systems and linking data together for better communication and rapid response to tunneling events reduces the risk or damage and stoppage.
The Singapore project was notable for the reduction in the costs of the client and engineer teams. Only two technicians and one engineer were required to oversee the management of data for the entire 35 km of the works. The streamlined teams were highly effective with shorter focused meetings and rapid closeout of actions.
Benefit 6: Reduction in organization size and increased organizational effectiveness.
Up to this point, tunnels were almost exclusively designed using standard CAD methods with 2D plans and sections. The attributes for objects were held in the drawing notes or in the specifications. Most CAD platforms were already spatial databases and it made sense for these systems to start to store the attributes of the objects as well as the spatial characteristics. Unfortunately, the main driver for this building information modeling (BIM) approach was architecture and many of the standards for the structure of data within drawing systems adheres to the concept of objects that are prescribed such as a door or a window. Most large civil construction including tunnels are built of linear progress where the final dimension or design is not determined until the ground is proven.
As such we have seen the use of CAD-based BIM in tunnels to show complex geometries of the final built works, but seldom examples of BIM applied successfully to the active construction. On Crossrail, the key BIM successes according to Taylor (2018) were not related to the tunneling or heavy civil processes, but rather:
- Use of 3D & 4D modeling to manage construction fit-out of MEP&A.
- Linking asset data through a geographical information system (GIS).
- Augmented reality.
- Handover of information to maintenance and operation.
The difficulty transitioning CAD BIM from the permanent works design phase into construction management phase remains one of the biggest challenges in the digitalization journey.
The costs of digitalization versus the benefits
Construction companies are already spending large amounts on software. This is significant for businesses in construction and particularly in tunneling where margins below 5 percent are common. These investments in software and digitalization must make real returns otherwise, they are likely to be unsustainable. According to research by the McKinsey Global Institute, digital transformation in engineering and construction can result in up to 15 percent in productivity improvement, and reduce cost by 4-6 percent (Barbosa et al., 2017). Potential ways these returns can be realized include:
- Reduce the size of organizations.
- Better management of risk:
- Increase the quality of the bidders with less gambling.
- Remove uncertainty (use of accumulated data).
- More active sites and nimble processes.
- Reduce the design claims.
- Reduce ground-related claims.
- Optimize methods and use the data to improve.
- Control on expenditure of time and money. Datadriven forecasting and updating of project risk profiles.
2020 and beyond
As with any new initiative, BIM and digitalization attracts a huge number of innovators to design tools for a variety of applications. The engineer is overwhelmed with areas to invest, and many early adopters find themselves with a toolbox full of applications, few of which can talk to each other. To make them work together requires additional investment in teams of people to manage the digital investment, canceling out any cost benefit there may have been.
In recent years there has been the rise of the integrator. a platform built to connect tools together and manage the flow of data from one to the other. Such systems can also combine many tools in one platform and consolidate many separate investments in one.
The integrator may solve the issue of BIM transitioning from design phase to construction phase with the integrator taking object progress and production details from the sites and providing regular feeds to BIM, Corporate GIS and program.
Benefit 7: Consolidate and reduce software costs.
This article presents a chronological summary of the evolution of digitization in tunneling and the benefits realized. These benefits include:
- Data standards and ease of communication, analysis and updating of data.
- Save time and money arguing about the data. Successful litigants are often those with the best data.
- The data has value. Look after it and use it on future projects to reduce business risk.
- Demonstrate machine-assisted active risk management that is data-driven with less reliance on human systems and benefit from cheaper insurance.
- Consolidating systems and linking data together for better communication and rapid response to tunneling events reduces the risk or damage and stoppage.
- Reduction in organization size and increased organizational effectiveness.
- Consolidate and reduce software costs.
These tangible and intangible benefits often advertised are seldomly quantified in a manner that provides business with meaningful measures of these benefits. While it is frequently challenging to quantify the benefits directly, this paper provides examples of quantified benefits.
As digitization continues to become an increasing initiative in the tunneling industry, it is imperative that benefits are well documented and quantified to encourage adaptation. Furthermore, standardization will lead to more universal acceptance within the industry. Lastly, it is imperative that integrative tools are implemented to link data and software systems together to properly manage the digitization of all project data.
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