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Value of Landslide Investigation to Geotechnical Engineering Practice in Hong Kong
Ingénierie des glissements de terrain à Hong Kong
Lo D.O.K., Lam H.W.K.
Geotechnical Engineering Office, Civil Engineering and Development Department, Government of the Hong Kong SAR
ABSTRACT: On average, about 300 landslides were reported to the Geotechnical Engineering Office (GEO) of the Civil Engineering
and Development (CEDD) in Hong Kong each year. Over the years, GEO conducted landslide investigations to advance knowledge
on slope performance and improve understanding of the causes and mechanisms of landslides. Landslide investigations have become
an integral part of the Government’s Slope Safety System in Hong Kong. Studies on notable landslides on man-made slopes have led
to the use of more robust stabilisation measures for cut slopes, improved rock slope engineering practices, enhanced practices in the
monitoring and maintenance of water-carrying services affecting slopes and improvement to drainage detailing. Studies on natural
terrain landslides have allowed better understanding on the modes and mechanisms of failure. This also enables advancement in
debris mobility assessment which is critical to natural terrain risk management. This paper highlights some key lessons learnt and
observations made from selected landslide investigations and how this knowledge helps advance the geotechnical engineering practice
in dealing with man-made slopes and natural terrain landslide hazards in Hong Kong.
RÉSUMÉ: En moyenne, environ 300 glissements de terrain sont signalés au Bureau Géotechnique (GEO) chaque année. Au fil des
années, les enquêtes de glissements de terrain sont menées par le GEO et jouent un rôle clé dans l'avancement des connaissances sur
la stabilité des pentes et la compréhension des causes et des mécanismes de glissements de terrain et sont devenus une partie
intégrante du système de sécurisation des pentes à Hong Kong. Les études sur les glissements de terrain sur les pentes anthropiques
ont conduit à l'utilisation de mesures plus robustes pour la stabilisation des pentes artificielles, l'amélioration des pratiques
d’ingénieurs pour les pentes dans les matériaux rocheux et l’amélioration des pratiques de suivi. Les études sur les glissements de
terrains naturels ont permis de mieux comprendre le mode et les mécanismes de défaillance. Cela permet également l’amélioration de
l'évaluation des déplacements des boues, ce qui constitue un point essentiel dans la gestion des risques naturels. Ce document met en
lumière certains des principaux enseignements tirés des observations faites à partir des enquêtes de glissements de terrain sélectionnés
et comment cette connaissance contribue à l'avancement de la pratique de la géotechnique dans le traitement des pentes artificielles et
naturelles à Hong Kong.
KEYWORDS : landslides, investigation, geotechnical engineering practice
1. INTRODUCTION
The rapid population growth in Hong Kong since the 1960s
and substantial economic expansion has been accompanied by
extensive civil engineering and building works, resulting in
the formation of a considerable number of man-made slopes
and retaining walls over the hilly territory. However, as there
was very limited geotechnical control of slope formation in
the old days, the stability of many of these slopes is therefore
in doubt. Coupled with severe rainstorms and dense hillside
development, Hong Kong is prone to landslide risk.
Following a number of landslide disasters in 1970s, the
Hong Kong Government established the Geotechnical Control
Office in 1977 (renamed as the Geotechnical Engineering
Office (GEO) in 1991) to regulate geotechnical engineering
works and slope safety in Hong Kong. This paper gives an
overall review of the slope engineering practices that have
been enhanced as a result of the landslide investigation (LI)
findings.
2. GEOTECHNICAL STANDARDS AND PRACTICE
Setting geotechnical standards has been one of the GEO’s
functions. To date, some 300 guidance documents have been
published covering standards of good practice for the
investigation, design, construction and maintenance of slopes.
For public development projects, the prevailing
Government policy stipulates that all permanent geotechnical
works involving slopes and retaining walls as well as related
activities, including investigations, designs and construction
should be carried out in accordance with the prevailing
standards. Details of the geotechnical works are required to be
submitted to the GEO for checking. In general, the standards
for public development projects are also adopted for private
building and civil engineering works in Hong Kong.
3. LANDSLIDE INVESTIGATION
Figure 1: The Kwun Lung Lau Landslide in July 1994
On average, about 300 landslides are reported to the GEO
each year. Most of these occurred at man-made slopes
affecting buildings, roads or pedestrian walkways. Many
landslides which occurred in remote areas or in natural terrain
were not reported. Prior to mid-1990s, the GEO conducted LI
on few selected cases of technical interest or having
significant consequence. The occurrence of a number of fatal
landslides in the mid-1990s has highlighted the need to
further enhance the landslide risk management strategy in
