2549
Application of cement deep mixing method for underpinning
Application de colonnes de sol-ciment pour travaux de reprise en sous œuvre
Melentijevic S., Arcos J.L.
Grupo Rodio-Kronsa, Madrid, Spain
Oteo C.
Universidad de A Coruña, A Coruña, Spain
aBstract: this paper presents a case history of the application of wet deep soil mixing columns for underpinning of the existing
floor slab of an industrial building, which settled due to different encountered post-constructive pathologies related to ground
conditions. the soil-cement columns were constructed with the application of the new developed springsol
tool that permits the
underpinning of existing foundations, infrastructure transport platforms and embankments, as well as working in limited spaces and
under low headroom conditions. the quality control regarding laboratory testing of core and wet grab samples is reported. design
procedure and the finite element analysis that verify settlement calculations are described. the fem is focused on the axisymmetric
numerical modeling in plaxis.
rÉsUmÉ : cet article présente une étude de cas de réalisation de colonnes de soil mixing par voie humide pour la reprise en sous
œuvre du dallage d’un bâtiment industriel, ayant tassé après sa construction à cause de pathologies du sol. les colonnes de sol-ciment
ont été réalisées avec la méthode springsol
, qui permet la reprise en sous oeuvre de fondations existantes, d’infrastructures de
transports et de remblais, à partir d’emprises étroites et sous faible gabarit. les contrôles le qualité réalisés en laboratoire sur des
éprouvettes carottées et sur des prélèvements frais y sont présentés. le mode de dimensionnement ainsi que les analyses par éléments
finis pour estimer les tassements sont également décrits. les calculs ef ont été réalisés avec le code plaxis en axi-symétriei.
KeYWords: deep mixing, soil-cement columns, springsol
, underpinning, fem.
1 introdUction
in order to reduce settlements, increase bearing capacity of
natural ground and improve the overall stability, different
ground improvement techniques can be put into practice, but not
all of them can be applied for underpinning projects. the
limitations for the applications are mainly related to capacity of
the machinery to pass existing foundation structures as
reinforced slabs or footings, and insufficient working spaces
and/or low headroom conditions.
the soil-cement deep mixed columns for ground
improvement of soft soils have an extensive application for
different geotechnical projects due to their higher strength and
lower compressibility than the untreated natural soft soil. the
application of traditional deep mixing methods, both wet and
dry, was very restricted for the underpinning of existing
foundations, improvement of existing embankments and
infrastructure platforms, due to the form and dimensions of the
mixing tool.
With objective to present new wet deep soil mixing system
called springsol
a case history with its application in
underpinning project is reported in this paper. to prevent
further settlements and guarantee bearing capacity of the
foundation of the industrial building that presented various post-
constructive pathologies, the springsol
deep mixing columns
were proposed as an alternative method to basic project
underpinning solution comprising jet-grouting, traditional tube-
a-manchette grouting and micropiles for different areas of the
building. due to its technical, economic and environmental
advantages, soil-cement columns were accepted and executed as
a global solution. in the following chapters the main
characteristics of the springsol
system will be described as
well as the analysis of the solution adopted and performed for
this project. some recent applications of the springsol
technique are given in melentijevic et al., 2012.
2 sprinGsol
soil cement colUmns
springsol
device was originally developed for improvement of
soils under existing railways due to its spreadable form
(innotrack 2009, le couby 2010). the folded tool is introduced
through the casing to the required depth at the beginning of the
column head. once it reaches the end of the casing and
penetrates the underlying soft soil, the blades spread out
forming the soil-cement column down to the required depth.
figure 1. the springsol
spreadable tool: (a) original and (b) modified.
at present, springsol
columns permit an application in
ground improvement for underpinning of existing foundations
(both slabs and footings), paving, embankments and subbase
below infrastructures (both highways and railways). originally
it was developed to form columns of 400 mm diameter. due to
continuous necessity for construction of soil-cement columns of
larger diameters the springsol
soil mixing tool has technically
evolved into the new modified version, permitting achievement
of different column diameters ranging from 400 to 700 mm. the
modified tool also includes the automatic system for opening
and closing blades thus having the possibility to form variable
