2457
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
Prediction of the unconfined compressive strength in soft soil chemically stabilized
Prévision de la résistance à la compression non confinée dans sols mous chimiquement stabilisées
A.A.S. Correia; P.J. Venda Oliveira & L.J.L. Lemos
Department of Civil Engineering – University of Coimbra, Portugal
;
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ABSTRACT: The chemical stabilization of soils is a ground improvement technique consisting on the mechanical mixing of the in
situ natural soil with binders. The chemical stabilization of soils can be applied with either slurries (wet method) or powder (dry
method) binders. When the stabilizing binders are mixed with the soil, physico-chemical interactions take place and are responsible
for the stabilization effect, which has a major influence on the mechanical behaviour of the improved material. This stabilizing effect
is dependent on a range of parameters which should be analysed through a long and extensive laboratory and field trial test program,
as stated in the european standard (EN 14679:2005). In order to minimize the number of tests during the optimization process, this
paper presents a simple method to predict the unconfined compressive strength, which is independent of the binder content and state
(powder or slurry). The method is successfully applied to a wide range of soils, showing its versatility (Correia, 2011). Applying the
generalised relationship of the method, it is possible to predict the unconfined compressive strength for any binder content and state
from one single unconfined compression test.
RÉSUMÉ : La stabilisation chimique de sols est une technique de l'amélioration des sols qui consiste en le mélange mécanique dans
situ du sol naturel avec liants. La stabilisation chimique de sols peut être appliquée avec coulis (méthode mouillée) ou poudre
(méthode sec) liants. Quand les liants stabilisateurs sont mélangés avec le sol, ils produisent interactions physique-chimique lesquels
sont responsables pour l'effet de la stabilisation, qui a une influence majeure sur le comportement mécanique du matériel améliorée.
Cet effet stabilisateur est dépendant d’une gamme de paramètres qui devraient être analysés à travers d’un long et étendu programme
d’essais en laboratoire et sur terrain, comme énoncé dans la norme européenne (EN 14679:2005). Pour minimiser le nombre d’essais
pendant le processus de l'optimisation, cet article présent une méthode simple de prédire la résistance à la compression simple, qui est
indépendant du contenu de liant et état (poudre ou coulis). Le méthode est appliquée avec succès à une grande gamme de sols,
montrant sa versatilité (Correia, 2011). Appliquant la version généralisée du méthode, c'est possible prédire la résistance à la
compression simple pour tout contenu de liant et état basé d'une seule essais à la compression simple.
KEYWORDS: chemical stabilization, unconfined compression test, soft soils, strength prediction.
1 INTRODUCTION.
Over the last few decades, infrastructure requirements and land
occupation policies have demanded construction on soils with
poor geotechnical properties (in particular, soft soils). These
soils are usually characterized by low strength and high
compressibility, demanding from geotechnical engineers new
and challenging solutions to overcome these undesirable
engineering characteristics. One of the ground improvement
techniques that have been used with success in practice is the
chemical stabilization, where the natural soil is mechanically
mixed in situ with binders (usually called Mass Stabilization, or,
Deep Mixing when applied in depth). This technique has given
good results when applied to soft soils, becoming a prominent
subject nowadays, rapidly growing and wide spreading around
the world due to its technical and economical benefits when
compared with other ground improvement techniques.
At first the chemical stabilization of soils used the quicklime
as the hardening agent. Later on, the use of Portland cement has
permanently been outpacing the use of quicklime, not only
because Portland cement is readily available at reasonable cost
but also because cement is more effective than quicklime
(Horpibulsuk et al 2011, Åhnberg 2006, Lorenzo and Bergado
2004, Kitazume and Terashi 2002). However, additives such as
granulated blast furnace slag, fly ash, gypsum and silica dust,
among others, may be used specially for the improvement of
soft soils with high water content or organic soils (Kitazume
and Terashi 2002, Edil and Staab 2005).
The chemical stabilization of soils can be applied with either
slurries (wet method) or powder (dry method) binders. When
the stabilizing binders are mixed with the soil, physico-chemical
interactions take place and are responsible for the stabilization
effect, which has a major influence on the mechanical behaviour
of the improved material. This stabilizing effect is dependent on
a range of parameters which should be analysed through a
laboratory and field trial test program, as stated in the european
standard (EN 14679:2005).
The fundamental mechanical properties of cement based
admixed soft soils have been experimentally investigated by
many researchers (Correia 2011, Åhnberg 2006, Hernandez-
Martinez 2006, Lorenzo and Bergado 2006 and 2004,
Horpibulsuk et al 2004, Kamruzzaman 2002, Horpibulsuk 2001,
Miura et al 2001, Uddin et al 1997, Locat et al 1996). Most of
these previous investigations mainly focus on the influence of
the water content and binder content, as well as on the ratio
between them. Based on some of these parameters, Horpibulsuk
et al (2003 and 2011) and Lorenzo and Bergado (2006) have
introduced phenomenological models for predicting laboratory
strength development in cement based stabilized soft soils. This
paper presents a new simple model which aims to predict the
laboratory strength (expressed by the unconfined compression
test) for various combinations of water content and cement
content. This model intents to minimize the number of
laboratory tests needed to specify the quantity of cement and
water to be admixed with the soft soil. Although the model is
Prediction of the unconfined compressive strength in soft soil chemically
stabilized
Prévision de la résistance à la co pression non confinée dans sols ous chi ique ent
stabilisés
Correia A.A.S.; Venda Oliveira P.J., Lem s L.J.L.
iv
Portugal
