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Proceedings of the International Conference on
Advances and New Challenges in Earthquake
Engineering Research, Hong Kong Volume
ADAPTIVE COLONY SYSTEM FOR STABILITY ANALYSIS
OF SLOPES IN EARTHQUAKE ZONE
Chang-Fu Chen 1 ' 2 and Xiao-Nan Gong 2
1 Institute of Geotechnical, The Hunan University,
Changsha, China
2 Institute of Geotechnical, The Zhejiang University,
Hongzhou, China
ABSTRACT
Earthquake is an important factor that induces the movements and failure of slopes. The stability of
slopes in earthquake zone has received wide attention due to its practical importance. In this paper, the
structure of ant colony system and the transfer probability of ants are modified to analyze the stability
problem of complicated slopes. A new adaptive ant colony system (AACS) is proposed to determine
critical slip surface and it is used to assess the influence of earthquake on the stability of slopes in
earthquake zone. Two examples are presented to verify the proposed approach.
INTRODUCTION
Movements and failure of cuts and natural slopes constitute an important geotechnical problem
(Leroueil, 2001). According to Schuster(1996), the economic losses associated with slope movements
reach about US$4.5 billion per year in Japan, US$2.6 billion per year in Italy, on the order of US$2
billion in the United States, and US$1.5 billion in India. China is probably the country that suffers the
most from fatalities due to landslides. The number of landslide-related fatalities exceeds 100 per year
(Li, 1989). Earthquake is an important factor that induces movements and failure of slopes. For
example, the Haiyuan landslides in 1920 in China killed 100000 (possibly 200000) people. Therefore,
the stability of slopes in earthquake zone has received wide attention due to its practical importance.
Generally, limit equilibrium techniques (bishop, 1955; Morgenstern and Price, 1965; Spencer, 1967;
Janbu, 1973; Sarma, 1979; Hoek, 1987) are commonly used to assess the stability of the slopes, as
complex geological subsoil profiles, seepage, and external loads can be easily dealt with. The key
problem in stability analysis of slopes is how to accurately determine the critical slip surface giving the
minimum factor of safety F±. Many approaches have been developed to automate the search for the
critical slip surface. The traditional mathematical optimization methods that have used include
dynamic programming (Baker, 1980), conjugate-gradient (Arai and Togyo, 1985), random search
(Siegel et al., 1981; Chen, 1992; Greco, 1996), and simplex optimization (Nguyen, 1985). The main