ABSTRACT
In recent years, with the development of urban underground space, the number of deep foundation pit even super deep foundation pit excavation engineering increases. Soil nailing is a versatile and cost-effective technique to stabilize excavated steep slopes and can well control the deformation, thus has developed into a commonly used supporting structure form of deep foundation pit (Lin & Xu 2006). Soil-nailing technique came into being in the 1970s in France, Germany and the United States and other countries (Plumelle et al. 1990, Juran 1990). In China, the soil nailing support technology began to be used to stabilize slopes of mines in 1980s (Chen & Cui 2000). In 1991 and 1992, the soil nailing structure was employed in the projects in Shenzhen and Taiyuan, and that is the earliest applications of the soil nailing support in deep foundation pit engineering of China (DBJ/T15-70-2009, Fu & Yang 2010). Before 1998, the number of deep foundation pit structured by soil nailing account to 10%∼20% of the total number of deep foundation pits; from 1998 to 2004, the figure reached 55%∼75%; Since 2005, the proportion is roughly 40%∼50%. The cause of reduction in proportion(though absolute quantity still increases) is that excessive deformations appeared frequently in excavation engineering with depth of 18m, leading to subsidence and destruction of some deep foundation pit, thus restrict the application of soil nailing in some the central area of the city (Yang 2010, Fu & Yang 2010, Zeng et al. 2009). Therefore, deformation control of soil nailing support is the key of the
design of a deep foundation pit bracing structure, but deformation is influenced by many factors. At present, finite element method and the artificial neural network technology are widely used in studies of the deformation of deep foundation pit supported by soil nailing (Plumelle et al. 1990, Chua & Anthony 2005, Juran 1990, Zhang 2009).
