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Full-Scale Field Monitoring of a Rainfall-Induced Sliding Slope in Hainan, China
Étude en vraie grandeur d'un talus glissant soumis à des précipitations à Hainan en Chine
Li A.G., Qiu J.J., Mo J.F., Gao W.
Shenzhen Geotechnical Investigation & Surveying Institute Co. Ltd., Shenzhen, China
Tham L.G., Yan R.W.M.
Department of Civil Engineering, The University of Hong Kong, Hong Kong, China
ABSTRACT: This paper investigates the mechanism of rainfall-induced sliding slope through a study based on a full-scale field
monitoring conducted in a sliding slope in Shimei Bay, Wanning City, Hainan, China, where some premium hotels and residential
buildings are being built along a natural hillside slope. Due to the heavy rainfall in October, 2011, it was found that the hillside slope
was sliding during the heavy rainfall. A number of instruments, including soil moisture probes, tensiometers, open standpipes and
piezometers, inclinometers, and a rain gauge were installed in the slope. Field monitoring of the sliding slope was conducted during
one dry and one wet seasons before the stabilization of the sliding slope. The paper mainly introduced the instrumentation system of
field monitoring of the sliding slope. It also introduced the preliminary analysis of the variations of rainfall intensity, soil moisture
content, matric suction, ground water level, slope deformation during the dry season of 2011 and the wet season of 2012 before the
stabilization of the sliding slope.
RÉSUMÉ : Cet article étudie le rôle des précipitations sur une pente glissante via une étude basée sur un suivi sur le terrain à grande
échelle, menée dans une pente glissante dans Shimei Bay, ville de Wanning, Hainan, en Chine, où certains hôtels de luxe et des
bâtiments résidentiels sont en cours de construction, le long d'une la pente naturelle. En raison des fortes pluies en Octobre 2011, il a
été constaté que la pente (colline) glissait pendant les fortes pluies. Un certain nombre d'instruments, y compris les sondes d'humidité,
tensiomètres, bornes-fontaines, des piézomètres ouverts, inclinomètres, et une jauge de pluie ont été installés dans la pente. Le
contrôle du glissement a été effectué pendant une saison sèche et une saison humide, avant la stabilisation de la pente. Cet article
présente le système d'instrumentation mise en place sur le site. On présente également dans cet article l'analyse préliminaire sur des
variations de l'intensité des précipitations, l'humidité du sol, succion matricielle, le niveau de la nappe phréatique et la déformation de
la pente pendant la saison sèche de 2011 et la saison des pluies de 2012, avant la mise en place des renforcements du site.
KEYWORDS: field-monitoring ; sliding slope ; rainfall-induced ; strumentation.
1 INTRODUCTION
Rainfall-induced landslides are common in the tropical areas in
China, especially in Southen China. Each year hundreds of
landslides, occur during the rainy season. Many of these
landslides have caused heavy damage and numerous fatalities.
The majority of these landslides are associated with heavy
rainfall. Hence, rainfall-induced slope failure becomes one of
the most common types of landslides in Hong Kong (Lumb,
1962a, 1962b, 1975; Brand, et al. 1984; Au, 1998; Franks,
1999, Dai, et al. 1999, 2001; Li , et al. 2002, 2003, 2005a,
2005b, 2006).
Due to the new policy that China aims to build the southern
island of Hainan into a top international tourism destination by
2020, the Hainan local government promises to boost
development not only by expanding oil and gas exploration,
offering more duty free services, developing logistics, reducing
pollution, but also by improving transportation networks and
infrastructure. Thus, more premium hotels, resorts, family-run
hotels and residential buildings are being built along the east
coast of the island.
In area of our study site, a lot of landslides were reported. A
total of 4 landslides were recognized within the site. Site
investigation was also carried out, which found that there was
even a big landslide with a scar volume of 500000 m
3
just one
kilometer away from the site. There was even a heavy debris
flow, which almost damaged the newly built east fast train for
Haikou to Sanya, which is just 5 kilometers away. As little
research work was carried out in Hainan for the landslides, there
are even few documents for the landslides, only occasionally in
the local newspapers.
In order to investigate the mechanism of rainfall-induced
slope failure, a study is being carried out based on a full-scale
field monitoring conducted in a sliding slope in Shimei Bay,
Wanning City, Hainan, China, where some premium hotels and
residential buildings are being built along a natural hillside
slope.
Due to the heavy rainfall in October, 2011, it was found that
the hillside slope was sliding during the heavy rainfall. The
sliding slope was a gentle hillside, which was cut to
accommodate a temporary road construction, and consisted
mainly of residual soil, CDG and HDG. To characterize the soil
properties of the sliding slope, a detailed site investigation was
carried out prior to the instrumentation.
A number of instruments, including soil moisture probes,
tensiometers, open standpipes and piezometers, inclinometers,
and a rain gauge were installed in the slope. Site investigation
included borehole drilling, soil sampling, field and laboratory
tests was carried out. Field monitoring of the sliding slope was
conducted during one dry and one wet seasons before the
stabilization of the sliding slope. The pre-stabilized slope was
monitored during the dry season of 2011 and the wet season of
2012. The stabilization of the sliding slope started before the
end of the wet season in 2012.
Anti-sliding piles plus pre-stressed anchors were designed to
stabilize the sliding slope. Other instruments including load
cells and strain gauges were suggested to be installed in the
