Week 15: Numerical Modelling and Monitoring of TBMs Advancement

This week in T&TBMs Master was devoted to the study of TBM advancement with lessons held by experts coming one more time from Geodata Engineering S.p.A. First some simplified 2D numerical models were defined to simulate a TBM driven tunnel behaviour and then we analysed as well the real parameters obtained from the machine driving and monitoring system.

Once again, Vincenza Floria (Geodata) gave us a two day practical course on FLAC 8.0 to model the advancement of the machine. The approach adopted for the simulation was the application of a relaxation factor known as the stress reduction method by Panet and Guenot (1982), in order to allow some gradual convergence of the excavated section before the installation of the lining. An interesting task required to perform a parametric analysis to understand and verify the influence of some factors as ground or lining properties and natural state of stress on the model behaviour. From this basic use of the software I could understand that it is a very powerful tool that requires a deep knowledge of the governing background theories.

Excerpt of a parametric analysis exercise done with FLAC 8.0

Finally Giampiero Carrieri (Geodata) held an outstanding lecture on TBM monitoring, not only regarding the machine driving parameters but also of the interaction between the excavation and the already existing structures. He focused on the importance of a well defined monitoring plan to take into consideration as a key tool for the Risk Management Plan, properly defining thresholds and countermeasures to be taken. His approach for the introduction of the topic was based on the presentation of several case histories from his most relevant projects.

Giampiero Carrieri and the students after his lecture on TBM Monitoring

Week 14: Facing Geological Particularities with Closed Shield Machines

This week in T&TBMs MAS Course was dedicated to the analysis of some particular geological situations that require attention when driving a TBM tunnel as well as to the study of EPB and Hidroshield Closed Shield mode machines. 

We had the privilege of receiving a lecture from Prof. Dr. Paul Marinos (NTUA, Greece) entitled Geological Constraints and Geotechnical Issues in Mechanised Tunnelling. He went through several situations that may be encountered when driving a mechanised tunnel from his wide experience as karstic voids, unpredicted hard/weak rock zones, squeezing ground or high pressure water presence. He provided also the main factors that need to be taken into consideration for the right choice of the machine, presenting many case histories to emphasise that each machine must be carefully selected.

Paul Marinos and the Master's students after his lecture.

After getting a clear idea about the choice of the machine, Alessandro Cresto (Herrenknecht) held an outstanding lecture to explain us thoroughly the EPB and HS Closed Shield TBM main features and technological aspects. In a three day intensive course he focused mainly in topics as:

• field of applicability and potentialities of each type of machine 
• main components design and materials
• components wear and maintenance operations
• special reparations
• support pressure
• backfilling grouting
• guidance systems

A strong background was provided by him presenting some very interesting and impressing case studies from his personal experience in one of the leading TBM construction companies, giving us also a general overview of the trends of the market.

Alessandro Cresto and the students after his lecture on EPB and HS.

Week 13: Closed Shields and Face Stability Design

To begin with this week, Prof. Dr. -Ing. Markus Thewes (Ruhr-Universität Bochum) held a fantastic lecture on Slurry Shield TBM technology. From his consistent research background and his wide experience on the application of this type of machines he covered deeply the most important issues to be taken into consideration. The slurry circuit, separation plants, bentonite suspensions, face support and difficult project conditions were the key points.

Markus Thewes and the Master's students after his lecture on Slurry shields.

Moreno Pescara from Geodata Engineering SpA, gave us a three day intensive course on Segmental Lining design. He went thoroughly through every detail regarding the design, verification, production, transport and assembly of the segments forming a precast concrete ring used in shielded TBMs. He emphasised in the importance of a proper Backfilling Grouting to control the induced settlements and to ensure the correct functioning of this lining system.

Extract of the lecture of Moreno Pescara on Segmental Lining Design.

Finally this week we had the honour to presence a great lecture from Georgios Anagnostou (ETH Zurich, Swiss Federal Institute of Technology) regarding Face Stability Analysis and Design. He went dynamically through the calculation method based on the silo theory and developed by him and his research group to asses the required pressure at the face. Special attention was paid to its application to closed shield machines, certainly this was one of a kind learning experience.

Georgios Anagnostou and the students after his lecture on Face Stability.

Week 12: Getting into Mechanised Tunnelling

Starting with the second modulus of the Master Course, Professor Peila held an introductory lecture on the overall aspects of mechanised tunnelling. He provided us with a clear picture of the developed technology and its main features in order to be prepared for the following lectures from specialists on the topic.

We had the honour of receiving a lecture by Prof. Dr. Kalman Kovári in which he adopted a practical approach to introduce us the aspects to take into account for different tunnel design cases. This interactive lecture was absolutely fruitful to apply and expose the concepts and ideas that we learnt in the past. From his wide experience he proposed some case studies to enhance our critical thinking of the possible solutions to overcome complicated conditions.

Prof. Kalman Kovári and the group of students after his lecture.

Prof. Dr. Nuh Bilgin (Istanbul Technical University) held an outstanding two day course on Cutting Tools and Excavability prediction for Mechanised Tunnelling. He went through the different tool types and its field of applicability, considering also their particular wear phenomena. Main attention was laid to the performance prediction in terms of Net Cutting Rate considering several numerical examples from true cases.

Prof. Dr. Bilgin and Master's students after his lecture on Cutting Tools.

To conclude with this first week of the second modulus, Eric Leca (Arcadis and ITA Executive Council Member) gave us a very interesting lecture on Tunnelling Induced Settlements. Starting from the governing theories with concepts such as the Volume Loss and its sources, he presented the factors to be taken into consideration for a proper tunnel driving in urban areas where the constraints are maximum. A valuable discussion of the monitoring results obtained in some case studies was the way to apply the concepts learnt, resulting in an exciting discussion.

Prof. Eric Leca and the students after his lecture on Tunnelling Induced Settlements.