1987
An Anchored Retaining Wall in CSM
Un soutènement ancré en CSM
Gomes Correia A., Tinoco J.
C-TAC - University of Minho, Guimarães, Portugal
Pinto A., Tomásio R.
JetSJ Geotecnia, Lisboa, Portugal
ABSTRACT: Cutter soil mixing (CSM) is being recently used in Portugal in several applications. This paper describes a solution in
cutter soil mixing reinforced with vertical steel profiles IPE270 for a retaining wall with 66 m long and 13 m high constructed in
geological formations of landfill materials, Miocene sandy soils and sandstones, with a phreatic level around 8 m depth. This
construction is done nearby commercial buildings. The solution is justified against more classical solutions for anchored retaining
walls considering the following aspects: feasibility of CSM in the geological and environment conditions, predict behaviour during
and post construction, simplicity of construction process, time of construction, economy and quality assurance. Numerical modelling
using a commercial program is carried out, based in geotechnical parameters established at the project level, showing a good
agreement of the observed data, in terms of horizontal displacements of the wall and also of the safety levels against bending, shear
and compression.
RÉSUMÉ : La technique « cutter soil mixing » (CSM) a été récemment utilisée au Portugal dans plusieurs applications. Cet article
décrit une solution CSM renforcé avec des profilés verticaux IPE270 pour un mur de soutènement avec 66 m de long et 13 m de haut
construit dans des formations géologiques de matériaux de remblai, des formations du Miocène de sols sablonneux et des grès, avec
un niveau de nappe phréatique autour de 8 m de profondeur. Cette construction se fait à proximité de bâtiments commerciaux. La
solution est justifiée par rapport aux solutions plus classiques des murs de soutènement ancrés tenant compte des aspects suivants:
faisabilité du CSM dans une vaste gamme des conditions géologiques et de l'environnement, prévoir le comportement durant et après
construction, simplicité du processus de construction, le temps de construction, l'économie et l'assurance-qualité. Une modélisation
numérique au moyen d’un programme commercial est effectuée avec l’utilisation des paramètres géotechniques établis au niveau du
projet, montrant une bonne concordance des données observées, en termes de déplacements horizontaux de la paroi, autant que des
niveaux de sécurité contre la flexion, le cisaillement et la compression.
KEYWORDS: soil treatment, deep soil mixing, cutter soil mixing, retaining wall.
1 INTRODUCTION
Deep Mixing is an in situ soil treatment method that makes use
of a technology in which the soil is mechanically mixed with
other materials, mainly binders. The composite material will
have improved benefits in terms of resistance, compressibility
and permeability (Larsson 2003, Bruce 2000). One of the
variants of Deep Mixing is the Cutter Soil Mixing (CSM)
technique, which produces panel elements with an accurate
geometry, vertically and direction. Additionally, low
disturbance is induced on the soil and nearby structures, making
their use appropriate in urban areas. Furthermore, this technique
has shown a great technical versatility and efficiency, as well as
economical advantages, including the optimization of the
construction schedule (Ameratunga et al., 2009, Capelo et al.
2012, Marzano et al., 2009, Pinto et al. 2011).
This paper describes an innovative solution involving CSM
panels combined with a reinforced concrete wall, for a
permanent ground anchored retained structure, with about 66 m
long and 13 m high constructed in geological formations of
heterogeneous landfill materials, Miocene sandy soils and
medium weathered sandstones, with a phreatic level around 8 m
depth. This construction is done nearby industrial buildings.
Consequently their main purpose was to act as a support system
maintaining the stability of the excavation against lateral earth
pressures, while controlling the deformation and settlement of
the surrounding structures (Porbaha, 2000).
The retaining wall uses soil-cement panels with a minimum
depth above the excavation level of 4 m and cross-section of 2.4
x 0.5 m
2
, including 0.20 m of overlapping, were built using the
CSM technology. The panels were reinforced with vertical
IPE270 (S275JR) hot rolled steel profiles (Euronorm 19-57),
spaced in average 1,1m, in order to resist both to the earth and
water pressures, as well as to ensure a better control of
deformations. The steel profiles were placed inside the panels,
before the cement started the curing process. The wall was
braced by four (case study) or three levels of permanent ground
anchors, applied at the capping beam as well as at the
distribution beams, integrated on the reinforced concrete lining
wall (Figure 1). As already stated, the soil-cement panels were
lined with a reinforced concrete 0.20m thickness wall,
connected to the vertical IPE270 profiles with steel cantilevers,
allowing the mobilization of the global resistance of both the
steel profiles and the lining reinforced concrete wall, acting a
Berlin wall combined with CSM panels. The design criteria,
verifying Ultimate Limit State and the Serviceability Limit
State, as well as the limitation of the water inflow, were
established by the support of 2D FEM analysis using
commercial PLAXIS
®
software. In this paper a comparison
between the control and monitoring parameters with design
parameters is done in order to support the discussion about the
reliability of both the solution and the construction method.
