Week 9 & 10: End of the First Modulus

We reached the end of the first modulus of T&TBMs MAS course with combination of some theoretical principles as lining structural design or risk management with several very interesting case studies.

To start with, Mirko Corigliano from ENEL Italy, covered the main aspects of Seismic design for underground structures. In most of the cases underground structures behaves properly against seismic actions due to its link to the ground and the damping effect of seismic waves with depth. It is important to consider anyway, when applicable, the seismic actions for the structural design of the lining elements in order to avoid undesired consequences such as loss of human lives or functionality.

Engineers Adriano Fava and Francesco Comba from Alpina S.p.A introduced a fantastic case study of a traffic tunnel undergoing the King's castle in Rabat, Morocco. An extremely delicate situation to minimise settlements in order to avoid any damage to this historical buildings lying on weak rocks. It is a great example of precise design and application of ground improvement and monitoring techniques.

Adriano Fava, Francesco Comba and the students after their case history lecture.

Eng. Andrea Pettinaroli held a case history lecture on Artificial Ground Freezing in Warsaw Metro. When underpassing an existing traffic tunnel a face collapse occurred even with a jet grouted arch of pipes due to the presence of a monogranular sand layer under the watertable in proximity of Vistula River. The solution applied to overcome this critical section was the use of Freezing technique, combining open and closed circuit technology they maintained the ground at around -30 °C, reaching this way the completion of a very critical section of the project.

Eng. Andrea Pettinaroli and the students of the Master after his case study lecture.

Harald Wagner (ITA AITES – EXCO Member, Consulting Engineer, Bangkok & Vienna) gave us a very interesting lecture regarding on the impact of Urbanising and the wide range of tunnelling applicability to cope with the raising demand in terms of infrastructure. He presented several case studies from his vast professional experience. 

Fabrizio Barpi from Politecnico di Torino held a fantastic two day course on structural design of composite linings, particularly focusing on the combination of shotcrete with steel ribs. He introduced the main background concepts of the structural theories to then explain thoroughly the procedure proposed by Carranza-Torres (2000). The idea is to use the equivalent section approach to distribute the forces and bending moments on each component of the section to then calculate their capacity diagrams in order to verify the safety conditions.

Fabrizio Barpi and the Master's students after his lecture on lining design.

We had the pleasure of receiving a lecture from Søren Degn Eskesen (ITA President and COWI Tunnel Chief Specialist) oriented to risk management methods. He emphasised on the importance of a thorough definition of every possible hazard to be encountered in a tunnelling project in order to have predefined countermeasures to tackle them as soon as possible and reduce their associated risk.

Søren Degn Eskesen and the students after his lecture on Risk Management Methods.

To finish with the first modulus we had a theoretical exam for the concepts presented until now. To pass the exam of each modulus is a must to obtain the final certificate of the Tunnelling and TBMs MAS Course.

Week 8: Numerical Modelling approach

To start with this week we had a day combining two very interesting topics explained by experts coming from the leading companies in the sector. Firstly, Maurizio Leotta from UTT Mapei (Waterproofing Director) went deeply trough the technologies and solutions applied by his company to waterproof the lining structures. The discussed solutions are not only applicable for tunnels but also for stations and other underground facilities lying under water table or that may expect some water influence in the span of their lifetime. Some application cases were studied focusing on the details and joints between elements, because these are the main source of failure of the system that would lead to undesired situations.

Maurizio Leotta (UTT Mapei) and Students after the lecture on Waterproofing systems.

After this lecture we moved to another topic very important and it is the probing ahead of a TBM face. Thomas Dickmann from Amberg consulting company held an outstanding lecture on geological and geophysical survey applications for TBM technology. He presented some techniques used for the evaluation of the ground properties ahead of the excavation face within the advancement steps. Finally he introduced the procedure developed by his company, the so called TSP (Tunnel Seismic Prediction) to define through a low charge D&B scheme with a good detail the conditions to be encountered.

Tunnel Seismic Prediction by Amberg Company presented by Thomas Dickmann.

In the following days Vincenza Floria (Geodata Engineering) introduced the main aspects and potentialities of Numerical Modelling for underground structures design. She established the theoretical basis considering also a big amount of case studies from her wide experience in Geodata projects all around the world. Thanks to a license provided by ITASCA we were able to apply all the concepts learned by using FLAC software to solve some simple examples performing a parametric analysis on the influence of the modification of certain ground and lining parameters on the system behaviour.

This is an amazingly powerful tool for the design that must be used with skill and knowledge about its limits and background theories.

Floria Vincenza (GEODATA) after her practical lecture on Numerical Modelling by FLAC.

Week 7: Conventional tunnelling and some key concepts

Professor Robert Galler (Montanuniversität Leoben) held an amazing lecture presenting the fundamentals of Austrian approach to Tunnelling. He went from the Conventional excavation technique, taking into consideration the fundamental static behaviour of the ground, to the tendering, design and construction phases, where precise attention is laid to the responsibilities and cooperation between the involved parties. I must say their approach is very smart, not only from the excavation technique viewpoint, so there is quite much to learn from such a solid model.

Professor Robert Galler and students after his lecture on Conventional Tunnelling.

Professor Claudio Oggeri from Politecnico di Torino introduced the General Concepts of Monitoring. This is the key tool for the comparison between the predicted and the real situation of the whole tunnel project, it is also fundamental for the control of the safety and stability from the construction to the operation. Defining threshold values for each measured parameter is a must.

European Standards introduced by Prof. Oggeri regarding Monitoring Plan.

A complete day was dedicated to Concrete Technology by Mapei UTT (Underground Technology Team) experts. Cristiano Maltese tackled the durability of the material from the basic chemistry of the involved reactions, defining the main degradation phenomena and the mitigation measures that must be taken into consideration while designing, preparing, casting and curing the concrete.

Dr. Cristiano Maltese and Master's students after Concrete Technology lecture.

Carlo Pistolesi emphasised on the mix design of concrete, taking into consideration the exposure classes, the required resistance and some other particular requirements of each project to define the right proportions and composition. The conclusion is that knowing very well this material is of paramount importance in order to be able to produce the durable structures required for tunnelling purposes.

Eng. Carlo Pistolesi and the students after his lecture on Concrete Technology.

Professor Peila continued with his series of lectures focused on Ground Improvement techniques, going deeply in this occasion into permeation grouting solution. He presented the technological aspects, grouting mixtures and the design and testing procedures for a proper result in terms of continuity, permeability and strength without causing disturbances to surface structures. The lecture was combined with plenty of case history from his former professional experience as a young engineer in a grouting company.

This week concluded preparing the field for the topic of next week that will be Numerical Modelling. Professor Borri Brunetto from Politecnico di Torino held a fantastic theoretical lecture on the fundamentals of numerical methods, starting from the mathematics of continuum mechanics and going through the background theories solved by Numerical Models to obtain a computationally efficient and convergent to a good approximation solution.