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Centrifuge model tests on foundation on geosynthetic reinforced slope.
Essais en centrifugeuse d'une fondation sur une pente renforcée par géosynthétique
P. Aklik, W. Wu
Institute of Geotechnical Engineering, University of Natural Resources and Life Sciences, Vienna, Austria.
ABSTRACT: Centrifuge modelling is a powerful tool for physical modelling of reinforced slopes and offers the advantage to observe
the failure mechanisms of the slopes. In order to replicate the gravity induced stresses of a prototype structure in a geometrically 1/N
reduced model, it is necessary to test the model in a gravitational field N times larger than that of the prototype structure. In this paper,
a series of model tests in a geotechnical centrifuge on reinforced slopes is presented. The geotextile reinforced slopes have the same
height of 270 mm and is built with soil layers of the same properties. Photographs with high resolution are taken in short time
intervals through the glass wall during flight and the soil deformations of geotextile reinforced slopes loaded with a footing are
evaluated with Particle Image Velocimetry (PIV). The experimental results of reinforced slopes are presented. The test data provide
interesting insight into the failure mechanisms and the progressive failure characteristics of geo-synthetic reinforced slopes.
RÉSUMÉ : La modélisation en centrifugeuse est un outil puissant pour la modélisation physique des pentes renforcées et offre
l'avantage d'observer les mécanismes de rupture des pentes. Pour reproduire les contraintes induites par la gravité d'une structure
prototype sur un modèle réduit à l'échelle 1/N, il est nécessaire de tester le modèle dans un champ de gravitation N fois plus grand que
celui de la structure prototype. Dans cet article, une série d'essais sur modèle dans une centrifugeuse géotechnique sur les pentes
renforcées est présenté. Les pentes renforcées de géotextiles ont la même hauteur de 270 mm et sont construites avec des couches de
sol de mêmes propriétés. Des photographies haute résolution sont prises à des intervalles de temps courts à travers la paroi de verre
pendant le vol et les déformations du sol de pentes renforcées de géotextiles chargées par une semelle filante sont évaluées en
vélocimétrie par images de particules (PIV). Les résultats expérimentaux de pentes renforcées sont présentés. Les données d'essai
donnent un aperçu intéressant sur les mécanismes de rupture et les caractéristiques de rupture progressive de pentes renforcées.
KEYWORDS: centrifuge, reinforced slope, foundation, PIV (Particle Image Velocimetry).
1 INTRODUCTION.
A wide range of geotechnical problems can be investigated
using physical modeling techniques. Centrifuge modelling has
become a powerful technique in geotechnical engineering for
studying the stability of prototype slopes. In order to replicate
the gravity induced stresses of a prototype structure in a
geometrically 1/N reduced model, it is necessary to test the
model in a gravitational field N times larger than that of
prototype structure (Viswanadham and König, 2009).
Substantial research demonstrated the effectiveness of
centrifuge modelling for studying the behaviours of
geosynthetic reinforced walls and slopes, as reported by
Porbaha and Goodings (1994, 1996), Zornberg et al. (1997;
1998a,b), Zornberg and Arriaga (2003), Viswanadham and
Mahajan (2007), Chen et al. (2007) and Viswanadham and
König (2004, 2009).
Foundations are sometimes built on slopes or near the edges
of slopes. Knowledge of the treatment of reinforced slopes
loaded with a surface footing is of practical importance to
geotechnical engineers. Although there are several research
studies on reinforced level ground, investigations of footings on
reinforced slopes are rather limited (Selvadurai & Gnanendran,
1989; Omar et al., 1993; Huang et al., 1994; Lee & Manjunath,
2000; Yoo, 2001; El Sawwaf, 2007; Alamshahi & Hataf, 2009).
In this paper, a series of reinforced slope models with a slope
inclination of about 65, 75 and 85 degrees were tested in a
geotechnical centrifuge. The aim is to investigate the effect of
the foundation on the geotextile reinforced slopes. Moreover, a
technique called Particle Image Velocimetry (PIV) is used in
this research to reveal the failure mechanisms of the geotextile
reinforced slopes. The experimental results provide
reproducible database for rational design of geosynthetic
reinforced slopes.
2. MODEL DESIGN
2.1. Centrifuge
The geotechnical centrifuge at the Institute of Geotechnical
Engineering, University of Natural Resources and Life Sciences
(BOKU) in Vienna was manufactured by Trio-Tech, USA and
was put into operation in 1990 with partial financial support
from the Austrian Science Foundation (Trio-Tech 1988). The
beam centrifuge has the following components: a swinging
basket, a balancing counterweight, a DC motor and
aerodynamic enclosure. It is equipped with 56 electrical slip
rings for process control and data acquisition. By using the dual
platforms, two models can be tested at the same time. However,
it is usual to have only one swinging basket carrying a model,
while a balance weight is loaded on the other platform. The
centrifuge has been used to investigate various problems in
geotechnical engineering, such as retaining wall, shallow
foundation and pile foundation. Recent development in digital
image processing offers excellent possibilities to study strength
of geosynthetic reinforced slopes. The technical specifications
of the centrifuge are listed in Table 1 and illustrated in Figure 1.
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