Dipl-Ing Katja Remus and Eur-Ing Nod Clarke-Hackston BSc (Hons) CEng MIMMM, VMT GmbH

When the tunnel was first mined, the ground moved 3mm. There was then no further movement. "In hindsight, I think we took a little more material than we should have." Lots of data, lack of information! That was the recurring situation that motivated the team at VTM to develop a central control data collection system. Undertaking the collection, collation, analysis and delivery of data from all electronic monitoring systems on a complex urban TBM tunnelling project, the system is designed to ensure adequate control of the process and prevention of damaging settlement and ground lose.

In 2008 the world reached an invisible but important milestone: for the first time in history more than the half of mankind now lives in urban areas. In order to supply the infrastructure enhancements to cater for the needs of these urban dwellers, the majority of this activity will be taking place underground, where much of the excavation will be made with the use of mechanized tunnelling machines. While excavation by TBM is often considered a continuous process, it should be more correctly described as cyclical, where the processes of excavation, spoil removal and tunnel support should all be coordinated, as they are both interrelated and interdependent. Keeping track of all these activities, of how they affect both the ground and the structures located above the tunnel, and of maintaining a traceable record, is now a common requirement by the owners of many of these projects.

Providing a central data control station is the objective of a new electronic system from VMT

As it is unlikely that any one supplier will be responsible for all the monitoring and recording activities on a given project, the method and format of the data produced will typically vary according to the specifications of the sensors and the systems of the individual manufacturers. In order to make full use of this data, VMT has created the 'Tunnel and Underground Information Software Structure' or TUnIS. The core of TUnIS is a sophisticated data exchange facility that enables data types of all common formats to be integrated in to a common database. Modules are available that cover all aspects of data on a tunnelling project including the machine navigation system tunnel supply and equipment logistics including a complete segment documentation system measurement systems both inside the tunnel and on the surface structures along the course of the tunnel geological and geotechnical investigations; and project design. This type of system should make up a part of the quality assurance package of any project.

Information systems have become indispensable in numerous sectors of the economy for decision-making. The use of technical information systems in complex projects has increased. Dynamic information systems such as the TUnIS information system CBP are the most important part in judging the entire situation, For situations - where correlation between events in the past, the present and the future need to be undertaken.

The system charts the tunnel alignment in relation to local infrastructure

During TBM tunnel construction for example, the ability to make fast decisions in potentially critical situations is vital. These decisions are dependent on the amount and quality of available data and information. The TUnIS information system CBP(controlled boring process) greatly assists project management in the provision of these. It is however paramount that the system is fully established at the commencement of the project so that all parties 'buy into the system from day one'. The objective of the system is to improve the overall performance of the project, not a means for each side to score points against the other. An agreement should be made between the contractor and the client at the beginning of any project where it should be decided what information shall be collected and to whom this information is made available. Job specific access should be made for those who will benefit from such access,including mechanic, electrician, surveyor, TBM operator, project engineer, and project manager etc.

VMT's TUnIS system supports tunnelling projects helping to keep interference of the project on the everyday life of a city at a minimum and in realising all necessary work with a high degree of safety, cost efficiency, and in making available the collected information in the planning of future projects.

The structure of the system is simply a collection of all relevant data contributing to the construction project in a single comprehensive real-time database and from where there are manifold applications for the correlated data from the different data sources. Indexing of all these activities is determined by time, ring number and chainage. Clock synchronization ensures that the correct time stamp for all data is applied and navigational data and monitoring results give the relevant positional information.

The TBM's area of influence can be clearly marked

The heart of the system is a server, based at the site office, which is within a local area network and/or a broadband connection for VPN access. Typically there will be a fibre optic connection between the TBM and the server. At the TBM control cabin another computer is connected to the PLC. This enables further input and evaluation facilities for the tunnelling crew. On projects where multiple sites are all working simultaneously, links to a central control room (manned 24h/day) would be effected to enable the project management team to have an overall view of all activities throughout the project and to respond to any unforeseen situations that may arise. Furthermore areas at risk of settlement are detected at an early stage and are displayed perspicuously, in order that corresponding measures can be initiated if necessary.

All relevant data can be inserted either automatically by an electronic interface, or manually either during the tunnelling process on the TBM, in the tunnel, from the office or from remote locations off site. The option to have handwritten notes or photos that can be introduced into the data base is also included.

The use of information systems in mechanized tunnelling has already proved itself on several projects including RandstadRail project in Rotterdam, the City Tunnel Leipzig, Budapest Metro, No 7 Line extension in New York, Emstunnel, Finnetunnel and the Barcelona metro. It is accepted by the customers as an important tool when working on complex tunnelling constructions. Data from previous advances can be examined, and important earlier experiences can be integrated in current projects.

Unique data source abilities
Just having a comprehensive data collection and reporting system would on many projects be of significant benefit. However collating all of this data and reacting to the information provided is a complex process and it is in this area where the TUnIS system is able to integrate the data provided. It gives composite displays and fully customized reports of the information and trends for all monitored activities to those directly responsible for controlling the tunnelling activities and to give suitable warnings when preset limits are approached or exceeded.

Composite displays
One of the system's core tasks is the visualization and analysis of the captured data. The data are processed and displayed for the various users in the appropriate form. The spectrum ranges from cross-disciplinary data views to integrating guidance assistance for the TBM operator. All modules display the current measurement values. Data of previous periods can be displayed either statically or dynamically, i.e. as a snapshot or as an animation, by means of the history function.

The TBM's advance can be charted against a geological section

The 2D project view: on the basis of maps and aerial view material shows the project area with tunnel alignment, advance information of the TBM, the as built rings and related information. Measurement data from geomonitoring and the sensor technology in the tunnel can be directly visualized. Settlement cross-sections can be observed. It is possible to define an area of influence around the TBM in order to visualize the values of its geotechnical sensors with warning lights. The warning lights help detect settlement movements quickly and if possible initiate any countermeasures required.

Sensor systems used both inside the tunnel and on the surface can be shown in relation to the TBM position. The display of the machine position and measurement values in the geological cross-section help the operator estimate the current and future behaviour of the machine as it is driven, in order to avoid errors and to detect changes in geology and any known potential barriers. All navigation data can be viewed in the control cabin of the machine. The driving behaviour can be displayed in a shield drive diagram at the same time. Thus the drive can be re-enacted during an advance; results from incorrect shield navigation can be understood more quickly, and future problems can be kept to a minimum.

With the 'Diagram Manager' data can be edited into diagram form. Types of diagrams are line, XY, polar and bar diagram. Fee combinations of all available measurement data, reference and limit values are possible. Data views may consist of one or more diagrams with one or more arrays. Thus different advances may be compared directly to each other. The 'Diagram Manager' ranges from the display of predefined data views to self-dependant creation and use of self-defined diagram structures. By means of this system the graphical analysis of data, even immediate comparison with previous advances, is possible at any work station as well as directly on the TBM while the advance process in almost real time. A comparison with previous similar advances and use of the obtained knowledge is possible.

In order to execute a settlement analysis,for example, the results of the geotechnical measurements above ground are correlated with the automatic recorded process data.

Ground movement on a TBM drive can be divided into the following phases:

The following TBM operating-parameters have to be kept in mind and correlated when completing a settlement analysis:

Automatic shift reports replace conventional manual reports. This automation saves time and provides an extensive report on the events within a shift. Thanks to the advance statistics and reports; shortages and problems occurring repeatedly may be detected and eliminated quickly. Location independent digital access to the desired information furthermore preserves resources and the environment. Reports do not have to be printed on paper but are available digitally. They can be rehandled, made accessible for other programs and can be forwarded to decision makers. Thus a smooth access to relevant information for all participants is secured.

Tracking the advance of a pipejacking project

Documentation of events and information
The 'Document Management' serves for collating and filing of information and notes. It provides digital filing of documents (for example pictures, tables, written documents) and it is a platform for information exchange during the construction operation. Due to the fast availability of information in different locations, the Document Management makes for time saving through 'short cuts' - whereby direct entry to the tunnel is often unnecessary. Within a standard advance with damage-free installation of the segments, all relevant data is recorded and analysed automatically. In case of segment damage or excessive structural ring deformations, damage analyses are executed. To support the cause of damage analysis, photos and measurements are taken. This together with the information supplied from the Segment Documentation system and any 3D dimensional measurement of the produced segments will give thorough QA throughout the entire ring production and installation.

Setup and function of the warning and messaging system
The warning and messaging system helps to control and optimise the boring process. It is based on the functionality of an 'Integrity Monitoring System'. Both intra-system processes and measurement data are monitored and deviations are reported to the respective responsible or defined personnel. Warnings and messages are obligatory saved in the system data bank and are displayed in the archive. Messages can either be shown on screen, or sent to email addressees or by mobile phone (SMS).

Artificial Sensors
Often, only a combination of various measurement values will lead to the desired result. It should be possible to define on-site 'artificial sensors', which result from a mathematical combination of measured values from various real sensors. As an example, the 'artificial sensor', was introduced for the (horizontal) momentum by the push rams along curved drive sections - in each case as the mean value over a complete stroke. The formula depends on the TBM, for the TBM used in Leipzig the formula based on (Pressure Group E + Pressure Group C2 - Pressure Group A - Pressure Group C)[bar] x 4 [Cylinders] x 8 [KN/bar*Cylinders] x 1.747 [m] + (Pressure Group D - Pressure Group B)[bar] x 6 [Cylinders] x 8 [KN/bar*Cylinders] x 3.8573 [m] was used.

Claim Management
In addition to the real-time benefits of the system there are also substantial advantages when negotiating claims at the end of a project. Having all the necessary substantiated evidence will enable both sides to amicably conclude settlements.

Conclusions
Information systems for the mechanized tunnelling shall offer the following possibilities:

Case Study: Analysis from the City-Tunnel in Leipzig
For the first example the time sequence of events was as follows:

16:27 hr: During the breakthrough of the TBM to the reception shaft there was suddenly a loss of pressure at compressor station - all available compressors started to run simultaneously. Between 16:30 and 16:44 hr: a complete overview of the situation for the operator, the shift engineer on the TBM and construction site management personnel was carried out. 16:44 hr: Decision made to continue the advance of the TBM at a pressure of 4 bar, followed by the flooding of the reception shaft with bentonite. 17:14 hr: Achieving of critical pressure, beginning to fill the reception shaft. 17:20 hr: Situation under control.

Breakthrough situation at the reception shaft

Fast available recorded data, not only TBM data, but also data from the compressor station, in the necessary combination made the estimation of residual time possible for successful handling of the situation.

For the second example the time sequence of events was as follows:

23:22 hr: Loss of bentonite during the advance (120 m3/hour) 00:36 hr: Halt of the advance 00:40 hr: Start injection with sealing compound (losses at 180 m3/hour) 02:15 hr: Despite injection and grouting of the annulus the losses increased to 250-300 m3/hour. 02:15 hr: Face support pressure reduced to absolute minimum. 02:20 hr: Losses reduced to 100 m3/hour. 04:00 hr: Losses reduced to nearly zero.

Loss of bentonite during start of TBM

Only the clear visual control of the feeder and production lines and simultaneous knowledge of the relevant operations in various locations permitted the assessment and efficiency of these corrective actions. The importance of having a clear and convincing display of all the relevant data readily available proved itself in this case whereby a potential catastrophe was satisfactorily avoided.

VMT

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