ABSTRACT
Practical and comprehensive seismic design methods for both shallow and deep foundations are currently some way from being fully established. The 1990s have seen the publication of a series of important papers on the seismic design of shallow foundations. However, several important gaps between theory and observation are yet to be bridged. In 1987 Dowrick could write that an authoritative rationale for the design of deep foundations did not exist. Progress has been made in the intervening years but substantial further work is required fully to establish seismic design methods both for shallow and deep foundations (e.g. Pappin, 1991; Pender, 1996). It is therefore pleasing to state that EN 1998-5:2004 provides one of the most comprehensive codes of practice for addressing seismic foundation design.In order to develop robust and reliable design methods good observations of field performance are indispensable. Despite the problems of making such observations on foundations, evidence has accumulated from major earthquakes over the past few decades. Many of these, from Alaska in 1964 to the Hyogoken-Nambu (Kobe) earthquake of 1995 have provided evidence of the highly damaging effects of liquefaction and lateral spreading for both shallow and deep foundations (Ross et al, 1969; Tokimatsu and Asaka, 1998). The unusual soft clay conditions of Mexico City (1985) gave rise to a range of foundation failures rarely reported elsewhere (Mendoza and Auvinet, 1988; Zeevaert, 1991). In general, spread footings properly designed for static loadings have been observed to perform adequately under seismic loading although cases of significant settlement have been reported (Richards et al, 1993). In contrast, the poor performance of raked or battered piles in bridge abutments and jetties has been highlighted in several earthquakes including Loma Prieta in 1989 (Seed et al, 1991).Current trends suggest that displacement based design methodologies will come in time to play a major role in seismic foundation design, but their full development is yet to come.
