2819
Polymer pillar, a new innovation for underpinning.
Colonne de polymère, une nouvelle innovation comme support de fondation.
Perälä A.
Powerpile Oy, Pirkkala, Finland
ABSTRACT: A new innovation, polymer pillar, has been developed for small and light weight buildings where the settlement of the
structure or the building must be stopped or the rate of settlement must be decreased. Polymer pillar is a patented product where
expanding high density geopolymer is injected inside a geotextile tube. Depending on the soil conditions, the polymer pillar can
establish geotechnical bearing capacity with several ways. The tip of the pillar can be extended to a hard soil layer for an end bearing
pillar. With thick sand and silt layers polymer pillars can be used as friction pillars. If there is a thick clay layer, they can be used as
cohesion pillars. Polymer pillar can also be used to compact loose friction soils. While injected, the pillars volume expands to one
hundred times the size of the pillar element. The soil around the pillar displaces and compacts. Polymer pillars have been used in
several underpinning projects around the world. The projects have taken place in many countries: The Great Britain, Finland, Sweden,
Australia, New Zealand, Belgium, The Netherlands and Germany. Totally there have been over 500 projects so far.
RÉSUMÉ : Une nouvelle innovation, la colonne de polymère, a été développée pour des bâtiments légers et petits, afin d'arrêter ou
diminuer le taux des tassements. La colonne de polymère est un produit breveté, dans lequel une géopolymère expansive de haute
densité est injecté dans un tube géotextile. Selon les conditions du sol, la colonne de polymère peut établir une capacité portante
géotechnique à plusieurs façons. L'extrémité de la colonne peut atteindre une couche de sol dur pour une colonne qui porte les charges
à la pointe. Dans les couches épaisses du sable et du limon, les colonnes de polymères peuvent être utilisées comme des colonnes
travaillant en frottement. S'il ya une couche d'argile épaisse, elles peuvent être utilisées comme des colonnes cohésives. La colonne de
polymère peut également être utilisée pour compacter les sols lâches. Pendant l'injection et l'expansion, le volume de la colonne
s'étend à une centaine de fois de la taille de l'élément de base. Le sol autour des colonnes est déplacé et compacté. Les colonnes de
polymères ont été utilisées dans plusieurs projets de support de fondations autour du monde. Les projets ont eu lieu dans plusieurs
pays: au Royaume-Uni, la Finlande, la Suède, l'Australie, la Nouvelle-Zélande, la Belgique, les Pays-Bas et en Allemagne. En total,
plus que 500 projets ont été réalisés à ce jour.
KEYWORDS: polymer pillar, PowerPile, geopolymer, underpinning.
1 INTRODUCTION
The need for underpinning houses and structures has been
increasing around the world. Most of the urban areas are close
to the waterfront, where the soil is usually soft (Lehtonen,
2011). Also the value of the land has increased, the good ground
for construction has often already been used and the quality
standards for buildings have tightened.
Polymer pillar is a new innovation for underpinning. The
basic idea of polymer pillar is to accomplish underpinning for
old houses with minimal disturbance. The use of polymer pillars
minimizes the disturbance for the old foundation structures and
also for the use of the building during the installation.
1.1
The use of polymer pillars
Polymer pillars are used to stop or to reduce the settlement of
old building or structure. Usually polymer pillars are used under
light weight buildings like 1 to 2 storey one family houses or
row houses.
There have been also some test projects on roads. In those
projects the settlement of the road in deep clay areas has been
reduced with cohesion polymer pillars.
1.2
The structure of the polymer pillar
The polymer pillar element is a slender tube. Outside diameter
of the element is only 32 millimeters. The element consist of
metallic injection tube, very tightly wrapped geotextile tube and
metallic sleeves on both ends. The element can be bent. The
minimum radius of bending is around 1.5 meters. This enables
installation in very low spaces like old cellars.
Injection tube
Top sleeve
Geotextile tube
Protective tape
Geopolymer
Bottom sleeve
Ø32
Ø330
Picture 1. Polymer pillar element and injected polymer pillar.
