1369
Design and performance of a jet grout retaining wall in a railway embankment on
soft soil
Dimensionnement et performance d’une paroi de soutènement réalisée à l’aide de la technique de
jet grouting dans un remblai ferroviaire sur sol mou
Verstraelen J., Maekelberg W., Lejeune C., De Clercq E.
TUC RAIL
De Vos L.
Geotechnics Division Flemish Government
ABSTRACT: Within the framework of the regional express network around Brussels, two new railway tracks will be added besides
two existing tracks linking Brussels to Ghent. The existing railway crosses the river Senne in Brussels with a geotechnical complex
lithography. Beside this complexity, other project boundary conditions, such as the height of the railway embankment, the very short
distance to the existing railway tracks in service, the small work platform to realize the retaining wall and safety issues linked to
working next to railway tracks in service, were of great influence on the design of the retaining wall. The excavation has a total depth
of 12.0m. The retaining wall consists of grout columns reinforced with steel beams. The wall is secured by grouted nails.
The jet grout columns were monitored and the resulting displacements and bending moments compared well with the design
calculations.
RÉSUMÉ : Dans le cadre du projet du réseau express régional autour de Bruxelles, deux nouvelles voies de chemin de fer seront
ajoutées le long des deux voies existantes reliant Bruxelles à Gand. Le chemin de fer croise la Senne, rivière de Bruxelles, dans une
lithographie géotechnique complexe. Outre cette complexité, d’autres conditions limites du projet, comme la hauteur du remblai
ferroviaire, la très courte distance par rapport aux voies en services, l’étroitesse de la plateforme de travail pour la réalisation de la
paroi et les consignes de sécurité liées au travail à proximité de voies de chemin de fer en service, ont eu une grande influence sur le
dimensionnement de cette paroi de soutènement. La profondeur d’excavation a atteint 12,0m. La paroi de soutènement est constituée
de colonnes de jet-grouting armées à l’aide de poutrelles métalliques. La paroi est retenue par différents lits de clous de jet-grouting.
Les colonnes de jet grouting ont été suivies par monitoring et les résultats des déplacements et des moments fléchissants ont été
comparés avec les résultats des calculs du dimensionnement.
KEYWORDS: VHP jet grout columns, retaining wall, soil nails, railway embankment, alluvium, peat, monitoring.
1 INTRODUCTION
The regional express network around Brussels aims to increase
the capacity of the train traffic in and around Brussels.
Therefore, the existing railway lines linking Brussels to the
most important surrounding cities, have to be widened from 2 to
4 railway tracks. The enlargement of the railway platform has to
be done in highly urbanized zones and with restrictive project
constraints. These constraints led in some cases to very complex
and innovative solutions.
The retaining wall discussed in this paper is situated along
the existing railway line 50A linking Brussels to Ghent, near to
the Senne river at the south of Brussels.
A retaining wall is needed to create an abutment for a new
integral arch bridge which is situated next to an existing bridge
abutment. The excavation removes the existing embankment fill
and goes up to 1 m underneath the natural ground level, as
shown in figure 1.
The realisation of the retaining wall for the abutments is
restricted by several constrains such as:
Railway traffic must remain undisturbed during the whole
construction period,
Excessive movement of the railway tracks in service must
be avoided and if they occur, they must be rectified
directly; these movements can lead to reduced exploitation
speeds and passenger delays,
For safety reasons, the use of large foundation machinery is
very much restricted next to the railway tracks in service,
No expropriation was possible, so a working platform had
to be created within the embankment contours,
Since the embankment is situated on highly compressible
alluvium, an enlargement or steepening of the embankment
to create a larger working platform could not be realised.
Figure 1. Cross section of the retaining wall
Due to these constraints, in a first working phase, a Berliner
wall with 3 m retaining height was executed close to the tracks
at the top of the embankment in order to create the working
platform that will be used to install the retaining wall to the final
excavation level, 12.0 m beneath rail level (see figure 1).
