Chef de projet : NOM Prnom - Repositório Aberto da Universidade ...

Premier Symposium Méditerranéen de Géoengineering «SMGE09» Alger 20 et 21 juin 2009
1. Introduction
The lime treatment of soils is one of the oldest techniques used (more than 5000 years old).
Indeed, even before the Romans, 2000 years ago, other peoples were already acquainted with
that procedure. For instance, Shersi pyramids in Tibet were built with clay and lime compacted
mixtures. Also, throughout the years, in China and India, lime treatment was used in various
ways (Ancade, 1997).
Presently, the lime potential in reducing the water content and the plasticity of soils is well
recognized and, therefore, its application in soil mixtures, namely within the framework of
geotechnical works, is normally taken into account in technical specifications.
These mixtures have also been often used to improve the mechanical characteristics
(deformability and strength) of compacted soils, particularly soils that, due their significant
amount of fines, are usually discarded, both in fills and in the substructure of transportation
infra-structures, roads or railways. This aspect is very important, because the consequences of
unbalanced earth works (embankments and excavation/cuttings) are decisive, in terms of
economic and environmental costs.
Nevertheless, the lack of knowledge of the long term performances of these mixtures, together
with the specific equipment demands, the insufficient knowledge about the application
techniques and, sometimes, the lack of an adequate cost-benefit analysis, have placed major
obstacles to accepting the use of such treatment in Portugal. Therefore, its use has not been
systematically adopted. In fact, apart from the works indicated in this paper, regarding highways
A2 (subsection Almodôvar – São Bartolomeu de Messines) and A10 (subsection Arruda dos
Vinhos – IC11), which were carried out by the Brisa, SA in 2001 and 2005, respectively, the
lime treatment of soils has only been used in a very few works. Furthermore, special reference
is made to the works studied by Neves (1993), regarding the construction of the “North-South
Axle Road (subsection Telheiras - Sete Rios)” and the “Lisbon Inner Ring Road – CRIL”
(subsection Alto do Duque – Buraca), as well as to the earthworks included in the
modernization of the North Line (subsections Azambuja - Vale de Santarém and Entroncamento
Norte – Albergaria tunnel), which were performed in 2003 by the railway administration.
Nevertheless, this scenario has been significantly changing in construction pratice. In fact, the
technical and environmental requirements placed by the new transportation infra-structures, in
particular the high speed railway network and the new Lisbon airport, is most likely to promote
the use of the lime treatment of soils, as an alternative to their replacement.
2. Case Studies
This paper presents various studies related with the lime treatment of embankment and capping
layers of pavements. Those studies concern two major roads constructed in Portugal: highways
A2 and A10.
The 240 km long highway A2, constructed in 2002, is the main link between Lisbon and Algarve
project has taken into account the possibility of using lime treated soils on the pavement
capping layer. The insufficient amount of appropriate soils to be used in capping layer within an
acceptable distance was the main reason for adopting the lime treatment of soils.
Highway A10 is a multi-purpose road aimed for those traveling from the Central and the West
region of Lisbon towards the North of the country. It also serves those traveling from the West
central part and from the north of Portugal down to Algarve, thus avoiding passing through
Lisbon. The lay-out solution which was developed for the section of highway A10 led to a
significant volume of excavations and embankments. Furthermore, it required the use of borrow
materials with appropriate characteristics and in sufficient quantities, which were unavailable
within acceptable distances. These factors have led to the solution of treating soils for the
construction of embankments.
Quicklime was the binder used in both works. Table 1 indicates the lime properties. In
accordance with the specifications of the Portuguese Standard NP EN 459-1 (2002), this lime is
classified as CL90-Q.