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Stability and performance of ground improvement using geocell mattresses under
extreme weather
La stabilité et les performances de l'amélioration du sol en utilisant des matelas géocellules dans
des conditions météorologiques extrêmes
Xu Y., Wang J.P.
Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Kowloon, Hong
Kong
ABSTRACT: Owing to the rapid change in our living environment, extreme weather and its ensuing effect should become a focus of
future engineering designs. Therefore, the underlying scope of this study is to evaluate the performance of a relatively new method in
ground improvement under a harsh condition, simulating its response to intense rainfall as a result of extreme weather. The model
tests show that the ground with the geocell reinforcement is of higher bearing capacity, compared to a natural ground without
reinforcement. In addition, the tension cracks around the footing, which was observed in the natural ground, would not develop in the
reinforced soil. The cause to the improved bearing capacity in the soil is in line with the finding through element testing suggesting
that the geocell with soil infilled in the pocket as an integrated material equivalently becomes a cohesive material. On the other hand,
the deformed geocell under the footing would develop a high passive earth pressure, larger than the water pressure possibly resulting
in the tension cracks around the footing in a natural ground without the geocell reinforcement.
RÉSUMÉ: En raison de l'évolution rapide de notre cadre de vie, les conditions météorologiques extrêmes et leurs effets devraient
devenir un foyer d'études techniques futures. Par conséquent, le champ d'application de base de cette étude est d'évaluer la
performance d'une méthode relativement récente dans l'amélioration du sol dans des conditions difficiles, en simulant sa réponse à des
précipitations intenses dues à des conditions météorologiques extrêmes. Les essais sur modèle indiquent que le sol renforcé à une
capacité portante meilleure qu'un sol naturel non renforcé. En outre, les fissures de traction autour de la fondation ne se développent
plus dans le massif renforcé par géocellules. La cause de l'amélioration de la capacité portante du sol est à relier à l'observation
expérimentale que l'élément géocellule remblayé avec de la terre devient équivalent à un matériau cohésif. D'autre part, la géocellule
déformée sous la semelle engendrerait une pression des terres passive élevée, plus grande que la pression de l'eau qui règenrait dans
les fissures de traction développées autour de la semelle dans un sol naturel.
KEYWORDS: Geocell, ground improvement, extreme weather
1 INTRODUCTION
Geocell is a relatively new form of geosynthetics mainly used
for geotechnical engineering. Different from the commonly
used geogrid, geocell is considered a three-dimensional soil
reinforcement material (Wang, 2007, Tafreshi and Dawson
2010). Its applications to engineering include soil retaining
systems (Wesseloo et al., 2008, Ling et al. 2009, Leshchinsky et
al. 2009,), ground improvements (Krishnaswamy et al. 2000,
Dash et al. 2001, Leshchinsky and Ling 2012), and erosion
control (Wu and Austin 1992). The results of element testing
(Rajagopal et al. 1999) suggest that the geocell with soil infilled
in the cell pocket as an integrated material equivalently
becomes a cohesive material with its friction angle remaining
more or less the same as the soil infill. Utilizing such a
technique as for strengthening the soil, the dynamic
performance of the soil retaining system with geocell wall
facing was found satisfactory under the intense shaking of the
Kobe earthquake, with full-scale shake table tests (Wang 2007,
Ling et al. 2009, Leshchinsky et al. 2009). In addition to
engineering aspects, geocell applications could reduce some
construction expense partly due to easy and rapid installation of
it, which can be constructed by low-skill crew without heavy
machinery (Wang 2007, Ling et al. 2009).
Extreme weather and the ensuing effect, such as heavy
rainfalls and floods, is the underlying cause to some recent
catastrophes. For example, in 2009 the Shiaolin landslide in
South Taiwan, destroying a local village completely and
causing more than 400 casualties, was a result of an abnormal
rainfall event brought by the Typhoon Morakot. The cumulative
rainfall in three days reported at 1,700 mm is nearly equal to the
annual rainfall of 1,800 mm around the region in the past few
decades (Tsou et al. 2010).
However, owing to the continuing development of global
civiliza
tion in need of keeping “exploiting” our living
environment, global warming and extreme weather would not
be expected to calm until we have a sound and effective
response, say, the advent of new technology and the change of
our living style and mind.
Therefore, this study aims to investigate the performance of
the geocell-reinforced ground under a harsh environment (i.e.,
intense rainfall condition), which could be anticipated during its
service life owing to the changing climate and extreme weather.
This study is mainly assisted with laboratory works of geocell
applications, and the details including experimental designs and
setups, results and discussions are summarized and given in this
paper.
2 EXPERIMENTAL DESIGNS, SETUPS
AND MATERIALS
The experiment is to create a harsh condition for the ground to
simulate its response to intense rainfall events as a result of
extreme weather. Therefore, the water content in the soil model
is added to a level around 20%, at which a thin layer of water
can be observed on top of the model ground surface, simulating
