1743
Compensation Grouting with shallow and deep foundations – case study from the
Metro B1 in Rome
Injections de compensation pour les fondations superficielles et profondes – étude
de cas de la ligne de métro B1 à Rome
Kummerer C.
Keller Grundbau, Vienna (Austria)
Sciotti A.
Roma Metropolitane, Rome (Italy)
ABSTRACT: For the construction of the new Metro B1 line in Rome a large number of geotechnical specialist works were performed
for the considerably deep stations and the protection of buildings. In two areas where the cover between the foundation and the tunnel
was very limited (less than 3 m distance), compensation grouting was utilized to mitigate TBM induced settlements for structures
founded on shallow and deep foundations with 19 m long piles, respectively. The paper presents the experience of the two
compensation grouting works, discussing the problems associated with the shaft construction and addressing the results of full-scale
field trials made in order to study the efficiency of compensation grouting.
RÉSUMÉ : Pour la construction de la nouvelle ligne de métro B1 à Rome, un grand nombre d'ouvrages spécialisés géotechniques a
été effectué pour le bâtiment considérablement profond de la station, ainsi que pour la protection des bâtiments. Dans deux secteurs,
où la distance entre la fondation et le tunnel a été très limité (moins de 3m), des injections de compensation ont été utilisés pour
atténuer les affaissements de bâtiments induits par le tunnelier pour des structures fondées respectivement sur des fondations
superficielles ou profondes avec piles de 19 m de longueur. Cet article présente l'expérience des deux ouvrages avec des injections de
compensation, en discutant les problèmes liés à la construction du puits et en traitant les résultats des essais à grande échelle complets,
réalisés afin d'étudier l'efficacité des injections de compensation.
KEYWORDS: Compensation grouting, deep shafts, infrastructure works, urban tunnelling
1 INTRODUCTION
The new underground lines Metro B1 and Metro C are
important infrastructure works for Italy’s capital city Rome.
Both Metro lines are characterized by challenging construction
conditions due to varying ground properties, deep stations with
high groundwater table and archaeological records. In
particular, the realization of the Metro B1 as a branch of the
existing line Metro B was difficult with its 4 new stations and
the excavation of approx. 7 km single track tunnel with 6.8 m
diameter and 1 km of double track tunnel with 9.8 m diameter.
The construction started in 2005, and tunnelling works were
finished in 2012. The section ‘Bologna’ – ‘Conca D’Oro’ was
inaugurated in June 2012.
The geology along the Metro B1 stretch is depicted in Figs. 1
and 2, respectively. In the area of ‘Bologna Station’ the soils
interested by grouting and tunnelling are pyroclastic formations
and recent alluvial deposits.
Figure 1. Geological cross section between ‘Bologna Station’ (left hand
side) and ‘Gondar Station’.
Grouting and tunnelling works for the ‘Ionio Station’ were
mainly made in Paleotevere gravels or silts and sands,
respectively.
The groundwater table for the entire Metro B1 is located at
few meters below ground surface. Table 1 provides an overview
of the main soil layers and their geotechnical parameters.
Figure 2. Geological cross section between ‘Gondar Station’ and ‘Ionio
Station’ (right hand side); for legend see Fig. 1.
Table 1. Geotechnical parameters for main soil layers.
unit
c[kPa]
phi[°]
E[MPa]
Man-made ground
0
30
20-70
Pyroclastic
0-20
28-38
90-400
Recent alluvial OC
15-45
19-27
60-160
Recent alluvial NC
0-5
28-30
60-160
Paleotevere-sand
0-30
26-37
80-200
Paleotevere-silt/clay
5-30
20-34
80-200
Paleotevere-gravel
0-10
32-41
100-300
