1951
Effects on adjacent buildings from diaphragm wall installation
Effets sur des bâtiments adjacents liés à l’installation de parois moulées
Comodromos E.M., Papadopoulou M.C.
Dept. of Civil Engineering, University of Thessaly, Greece
Konstantinidis G.K.
Manager, Attiko Metro S.A., Greece
ABSTRACT: A new approach for simulating the excavation and construction of subsequent panels is proposed to investigate the
effects from the installation of diaphragm walls on the surrounding soil and adjacent buildings. The method has been combined with a
3-D nonlinear analysis and a constitutive law providing bulk and shear modulus variation, depending on the stress path (loading,
unloading, reloading). The effects on an adjacent building have been investigated by applying a full soil-structure interaction analysis
including the whole building. Contrary to lateral movements, which mostly take place at the panel under construction, it was found
that the effect of settlements covers a larger area leading to a progressive settlement increase. The effect highly depends on the
distance from the panel under construction. Settlement profiles and settlements at specific points as increasing with subsequent panels
installation are given providing the ability of specific monitoring guidelines for the upcoming construction of the diaphragm wall in
front of the building.
RÉSUMÉ : Une nouvelle approche pour simuler l'excavation et la construction des panneaux subséquents est proposée pour étudier
les effets liée à l'installation de parois moulées adjacents sur les bâtiments et le sol adjacents. La méthode a été associée à une analyse
3-D non linéaire et une loi de comportement qui permet la variation des modules de déformations en fonction des chemins des
contraintes. Les effets sur un bâtiment adjacent ont été étudiés en appliquant une analyse d’interaction sol-structures pleine, qui inclut
l'ensemble du bâtiment voisin. Contrairement aux mouvements latéraux, qui principalement prennent lieu à partir du panneau en cours
de construction, il a été constaté que l'effet des tassements couvre une plus grande région, conduisant à une augmentation progressive
de tassements. Les effets dépendent fortement de la distance au panneau en cours de construction. Les profils des tassements et
tassements aux points spécifiques augmentant progressivement avec l'installation des panneaux sont donnés en face de l'immeuble où
la paroi moulée est en cours de construction.
KEYWORDS: diaphragm walls, soil-structure interaction, multi-stage analysis, buildings settlements.
1 INTRODUCTION
It is widely accepted that the process of installing diaphragm
walls can result in potentially significant soil displacements and
cause substantial reductions in horizontal stress. Depending on
the soil profile, the diaphragm wall configuration (length and
construction sequence) and the close existence of adjacent
buildings with poor foundations may render the effects of
diaphragm wall installation considerable. Field monitoring
confirms that ground movements resulting from diaphragm wall
installation could be a significant component of the overall
displacement (Burland and Hancock 1977, Tedd et al. 1984,
Symons and Carder 1993), while centrifuge tests verified the
development of the effect as well (Powrie and Kantartzi 1996).
Recent field evidences recorded during the on going
construction of subway stations in Thessaloniki demonstrated
that the component of ground movements resulting from the
diaphragm wall installation may be higher than 50% of the
overall displacements. It is therefore evident that the simplistic
assumption of a ‘wished-in-place’ wall (installation without any
change in stress and cinematic field) commonly applied for
design purposes is rather questionable.
The aim of the present paper is to investigate the effect of a
diaphragm wall installation to adjacent buildings with relatively
poor foundations. The sequential installation of each individual
diaphragm wall panel installation was simulated by a
substitution of the parameters of excavated elements with those
corresponding to the bentonite slurry and later on by the
concrete tremied into the panel. Valuable qualitative and
quantitative conclusions regarding the variation of the effects to
the adjacent building have been drawn.
1 INSTALLATION PROCEDURE MODELLING
With the aim of minimising disturbance and increase stability
during the excavation process, rotary drilling machines for slot
excavation have been used in Thessaloniki’s underground
stations with poor soil conditions. Figure 1, on the left side,
shows a rotary drilling machine equipped with cutting wheels
and a reverse circulation system. On the right side of Figure 1
the numerical simulation of the excavation process is illustrated.
The soil from the surface level down to the upper limit of the
rotary wheels (line A), is replaced by a material simulating the
bentonite slurry. Appropriate, very small values are attributed to
the bulk and the shear modulus of the material. Within that zone
the stresses are initialised to the values hydrostatically defined
from the weight of bentonite slurry. This simulation process
ensures that stresses within this zone remain always equal to the
hydrostatic conditions no matter the deformation level.
However, in the area occupied by the rotary cutters (area
between line A and line B) the development of static hydrostatic
pressure is not evident. For this reason, in that zone the stresses
are not initialised hydrostatically and only internal gravitational
stresses are considered. Within this zone the material (cuttings
with bentonite slurry) has higher unit weight and is stiffer than
bentonite slurry. The zone undertakes the pressure from the
