4.1 General

The state of the knowledge regarding the excavation behaviour in soft clays has expanded substantially over the last few decades. Several excellent state of the art reports on this subject have been published (Peck 1969; Lambe 1970; Bijerrum et al. 1972; Clough and Schmidt 1977; Clough and O'Rourke 1990). Moreover excellent handbooks and textbooks, that explain the construction and design principles of excavation in more detail, such as Smoltczyk 1996; Clayton et al. 1993; WeiBenbach 1985; Fang 1991; etc. are also available. The aim of this chapter is therefore not to repeat the previous works, rather to review and point out some problems of design and construction of supported excavation.

Peck 1969 summarised the experiences with performance of deep excavation support system, and the factors that are most important in controlling the performance. These factors include the type and strength of the soil around and beneath the excavation, the excavation and supporting procedure, and workmanship. Beside the above factors, the groundwater condition, the flexibility or rigidity of the components used for construction, the time taken for construction are also important factors that influence the performance of excavations. Mana 1978 classified the factors into: parameters under designer control, parameters partially under designer control, and fixed parameters not subject to designer control (Table 4.1).