Mechanized Tunnelling in Urban Areas
Design Methodology and Construction Control
The world of underground engineering and construction has acquired a wide-ranging
and high-level experience on tunnel construction with Tunnel Boring Machines
(TBM), thanks to the remarkable increase in the number of tunnels that are becoming
longer, going deeper, and growing larger in diameter; in other words, becoming more
difficult to realize.
In urban areas, the acquired consciousness of preservation and care for the anthropogenic
environment, accompanied by the improvement in the quality of life, has
raised the level of diffi culty and challenge in respecting the constraints deriving from
human presence and, therefore, the necessity for a technological and intellectual approach
to respond appropriately to these constraints.
This recent, invaluable experience gained from a series of accidents in urban tunnelling
worldwide has made us aware that the TBM is simply not a fully mechanized
tool integrating the various operations of the conventional excavation method for
excavating more rapidly, and overcoming all (or almost all) the well-known problems
and uncertainties. Instead, the TBM and the tunnel to be excavated, constitute a delicate
and sensitive, unitary system, which should be managed with a new approach,
rationally organized and scientifi cally sustained, in a unifi ed context of research and
design of the tunnel, the machine, and the environment.
In particular, all the principal risk factors are found to be associated with tunnels
in densely populated urban areas, including the properties and services subject to risk,
poor geotechnical conditions of the ground, presence of and consequent interference
with water table, and the small overburden with respect to the excavation diameter.
The focus of this book is exactly on the problems of urban areas. Its authors want
to analyze and propose not only the machines, but also, above all, the new special
techniques for controlling the proper operation of machines and, consequently, the
ground water drainage, the stability of the excavation face, and the resulting tunnel
profi le, for the purpose of minimizing the risks of subsidence. Therefore, a substantial
portion of the book is dedicated to identify, evaluate, and manage such risks.
Framed in this particular manner, it seems to me that the book stands up above
customary texts, in drawing attention to mechanized construction of tunnels in urban
areas as a complex system that needs real or conceived certainties: adequate preliminary
investigations for small depths must supply exhaustive information; scientifi
c design that should not leave anything to be invented during construction; reliable
and correctly equipped machines to face the foreseen potential emergencies;
and planned construction managed by supervisors and technicians with demonstrable
qualifi cations. In this sense we try to supply at Politecnico di Torino a serious contribution
of training with the commitment of a Master’s course of a year’s duration on
“Tunnelling and Tunnel Boring Machines”.
To sum up, I like this book for many reasons, just a few of which I would like to highlight
1. It brings fresh air to the conception of tunnels in urban areas, placing in the forefront
the fi ght against the risks, thus supplying a reliable instrument for making
rational and transparent choices to the decision-makers, who may be shocked by
the many cases of damage and collapse manifested in urban tunnelling history.
2. It is useful for the TBM users and operators who, in facing their duty to make the
machine run at its maximum capacity, must acquire the consciousness that the
consequent risks should be very well evaluated, anticipated, and minimized. The
book is also useful for the students to whom we must try to impart the sense of
“scientifi c humility” (auto-criticism is never enough!) and who must, as quickly
as possible, learn the lessons from the available, collective experience.
3. Another important reason for my appreciation of this book emerges from the
above two reasons: it is written by experienced technicians who clearly intend to
show, through specifi c examples in which they were directly involved, what the
origin was for the manifested risks, how they were approached and overcome,
and how these risks could be avoided in the future.
How much more useful is it in our profession to re-analyze the critical situations,
rather than taking glory for a piece of work that was well developed without obstacles!
Professor of Tunnelling at the Politecnico di Torino, Italy, and
Past President (1995–1998) of International Tunnelling Association
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