Integrating TBM management data with BIM 17 Jan 2019

‘What you see is all there is’ - WYSIATI - is a principle introduced by the psychologist Daniel Kahneman¹ that describes the biased thinking of the human mind, which draws final conclusions very quickly but based on limited and partly false information just because they are available. This leads to an overrepresentation of insignificant details that are easy to recognize over actually more important facts that are more difficult to perceive.

Fig 1. BIM representation of segmental lining embedded in digital ground model with TBM thrust forces highlighted

Utilising this principle, the quality of decisions can be improved considerably by facilitating the perception of significant information and presenting decision-makers a more complete picture of the project in an easily interpreted and transparent manner. In diminishing false bias and accounting for previous experience, scientific facts, statistical significance and incorporation of large amounts of data, computer-aided decision-making support helps finding better, more economically viable and well-founded solutions.

This requires the key components of the TBM tunnelling project to be understandable by computer systems and for the project to exist in digital form with respect to:

• The ground model, being the environment of the tunnel
• The tunnel structure, including all major components
• The TBM, being the essential tool for the tunnel construction

To obtain a full, transparent picture, this information must be presented in a common framework, for example in BIM (building information models), which renders data easily accessible and indicates relevance.

Key information management components

BIM can be employed at an early stage of the tunnel project and used already to advantage in the design and construction phases². The key components of these models can be linked to each other by means of a common location and time reference framework.

The purpose of a digital ground model is to provide information from geotechnical investigation and geological expertise to all project stakeholders in a computer-readable form.

Fig 2. Data sources for the PROCON integrated information management system

Along its alignment, the tunnel volume is intersected with the digital ground model to create a digital 3D tunnel model (Fig 1), with areas of similar geotechnical properties from homogeneous sections as tender basis. Rings of lining segments are represented in the model in order to incorporate data from segment tracking and quality management.

Real time data from the hundreds of sensors that monitor every component of TBM operations is required for understanding the interaction between the TBM, the ground and the tunnel structure. The volume of this data however, requires filtering for relevance and to summarise the information for decision-makers. Here, process controlling software, such as PROCON, plays an important role³ to providing graphical representations of project data in interactive charts (Fig 3).

Monitoring of the ground surface and adjacent structures is a further source of information that requires attention. Measurements are often digitally acquired and processed and are typically displayed in Geographic Information System (GIS) environments where users can easily locate and assess them. Markers are sometimes visualised in 3D.

Like TBM data, the volume of measurement data is huge. Therefore, useful information can only be obtained from monitoring data with proper filtering and a threshold-based alarming system.

Reporting and document management

Large projects produce large amounts of documentation and reports. This puts important information at risk of being overlooked. Additionally, the importance of a piece of information may only become apparent in hindsight. Restricting the amount of documentation is therefore not feasible. Here, document management plays the crucial role of pre-evaluating and filtering available data for relevance.

In most projects, the various monitoring components are isolated products. It is only with integration into a common reference framework that information management can unfold its full potential.

Bundling project information into a single reference framework is a concept that can be achieved with BIM, a technology typically associated with semantic information linked to 3D representations of the structure.

Integration is understood as a common reference space in terms of state, time and location for each piece of information about the project. A BIM model can be part, but is not a prerequisite for this. The key is that whichever piece of information is used, it can always be related to all other project data.

This allows using connected data without the need for overly complex integrated software platforms. In fact, the specific information required for a particular analysis can be collected from various data sources (for example TBM data, design documents and GIS) and correlated by means of their common reference framework (such as location and time of the measurements), and processed in the controlling software PROCON (Figs 2 and 3).

Fig 3. Screenshot of a PROCON process controlling system that combines information from various sources with GIS and data analysis

An example for the combination of a 3D ground model with TBM and mucking data is the investigation of excavation performance in different homogeneous sections of tunnel advance. Based on scientific models, predictions of the performance can be made. During excavation, the actual excavation performance (derived from TBM data) can be compared with actual ground composition (as observed in the mucking process). As a result, deviations from the predicted ground conditions can be detected and the potential for TBM operation optimisation or the need for maintenance can be identified.

A second example is downtime and tool wear analysis by combining ground model information, shift reports and TBM data. This analysis detects hidden correlations between operation and technical difficulties, the influence of ground conditions on operational aspects, or identifies improved maintenance intervals.

Advantages of collaborative information sharing

All partners of a project benefit from collaborative information sharing. With transparent information on a project status and its boundary conditions, conflicts can be easily identified and settled or prevented.

At all project levels, the common information platform provides target-actual comparisons of time, cost and safety. Deviations are detected and respective countermeasures can be unanimously decided. This enables faster decision processes and, in turn, drastically reduced delays and cost overruns with improved quality.

Shared resources and open communication throughout the project helps establish an environment for concerted settlement of conflicts with the mutual goal of steady improvement of the project.

A prerequisite for this strategy is the implementation of a common reference in information management. Digital models provide this framework, upon which relevant information is extracted from huge amounts of data. Inevitable filter bias of isolated and segregated pools of information is overcome and replaced by an objective representation of all facets of the project.