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General Report of TC204
Underground Constructions
Rapport général du TC204
Constructions souterraines
Dias T.G.S., Bezuijen A.
Ghent University, Laboratory of Geotechnics, Ghent, Belgium
ABSTRACT : This paper presents the general report of the TC204 session “Underground Constructions on Soft Ground” of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering. A total of 27 papers were assigned for this session, they
were divided in six general topics and reviewed briefly in this report. Apart from the regular topics of the TC204, this session also
present three papers on rock tunnelling. This report is intended to provide a general view of the papers of the TC204 session.
However, for a better understanding of the presented contents, the readers are encouraged to look for the complete papers in the
proceedings.
RÉSUMÉ : Ce document présente le rapport général de la session TC204 "Travaux souterrains en sol meuble" du 18
e
congrès
International de Mécanique des Sols et de Géotechnique. Au total, cette session comporte 27 communications, qui ont été réparties en
six thèmes généraux et sont brièvement analysées dans le présent rapport. Outre les thèmes du comité TC204, cette session présente
également trois communications concernant les tunnels au rocher. Ce rapport est destiné à fournir une vue d'ensemble des
communications de la session TC204. Pour une meilleure compréhension des contenus présentés, les lecteurs sont encouragés à
consulter les articles complets dans les comptes-rendus.
KEYWORDS: Underground constructions, soft ground, rock, tunnels, maintenance, construction
1 INTRODUCTION
Underground constructions have been one of the most
challenging endeavours of engineering for centuries. The effort
of researchers and engineers has given the society the
opportunity to explore the full potential of the underground
space in any geological conditions preserving the surface
structures.
The papers for the TC204 session “Underground
Constructions on Soft Ground” on the 18
th
ISSMGE conference
show the on-going development of this broad field, covering
several important topics, proposing solutions for different
problems and tracing the way for future research.
A total of 27 papers from 13 nations have been located in the
TC204 session. Figure 1 illustrates the number of papers
submitted per nation.
2
1
4
6
Figure 1. World Map indicating the number of papers submitted per
member society.
It is also remarkable to note that some countries did not send
papers for the TC204 session, although these countries have a
tunnel tradition and still a number of projects running: Brazil,
Iran, India, UK, and USA. Despite the TC focus on
Underground Constructions in Soft Ground, the ISSMGE
Conference session also presents some cases for underground
constructions in rock.
The papers were divided in six general topics as follows:
1. Underground Constructions in Soil (9)
2. Mitigation Measures (7)
3. Tunnel Maintenance and Instrumentation (3)
4. Rock Tunnelling (3)
5. Seismic Analysis of Tunnels (3)
6. Construction Techniques (2)
2 UNDERGROUND CONSTRUCTIONS IN SOIL
This topic gathered nine papers that had a general view about
tunnels constructed in or based on soil. Discussions about soft
soil deposits, twin tunnel interaction, stress arching in trenches,
analytical stability methods, assessment of surface settlements,
wearing of TBM tools, cavity formation around underground
structures and even immersed tunnels are presented.
Rangel-Núñez et al.
in their paper “Performance of the
tunnel lining subjected to decompression effects on very soft
clay deposits” present a case study of tunnel excavated with a
Tunnel Boring Machine (TBM) in the Mexico City soft clay.
The study evaluated the particular case of the Eastern Emitter
Tunnel where a channel was dredged above the tunnel
alignment and the unloading reactivated pre-existent semi-
vertical cracks in the clay deposit. These cracks were identified
visually during the construction of a shaft near the channel and
were an indication of the unloading of that zone. Piezocone tests
confirmed that, as the measured coefficient of earth pressure at
rest was three times smaller near the channel compared to the
value at some distance from the channel.
Instrumentation of the tunnel revealed an increasing rate of
lining displacement after a dredging procedure at the channel
above. A multistep Finite Element Analysis (FEA) was carried
