Geoscience Reference
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three interrelated steps: field studies, centrifugal experiments, and numerical/analytical
modelling. Specifically:
Field studies of documented case histories motivated our investigation and offered
material for calibration of thetheoretical methods and analyses.
Carefully controlled centrifugal experiments helped in developing an improved
understanding of mechanisms and in acquiring a reliable experimental data base for
validating thetheoretical simulations.
Theoretical methods (analytical or numerical) calibrated against the above field and
experimental data offered additional insight into the nature of the interaction, and
wereutilised in developing parametric resultsand design aids.
This paper summarises some of the key findings of these theoretical studies, which were
later supplemented with further analyses by the authors pertaining to pile and caisson
foundations. The emphasis of the paper is on elucidating the soil-foundation interaction
in the presence of large soil deformation, and near failureconditions.
2. Fault-rupture propagation and its interaction with foundations
2.1. STATEMENT OF THEPROBLEM
It has long been recognised (Duncan and Lefebvre, 1973; Bray, 1990) that a “strong”
structure founded on/in soil can resist successfully the loading induced by a rupturing
seismic fault. In the Kocaeli, Duzce-Bolu, and Chi-Chi earthquakes of 1999 numerous
structures(single-storeyandmulti-storeybuildings,bankers,bridgepiers,retainingstruc-
tures, electricity pylons, dams, tunnels) were located directly above the propagation path
of the rupturing (normal, strike-slip, reverse) faults. Some of these structures exhibited a
remarkably good behaviour. This observation had a strong motivating influence for our
research effort. For it became immediately clear that the strict prohibition: “Do not build
intheimmediatevicinityofactivefaults!”,whichtheprevailingseismiccodesinvariably
imposed, was unduly restrictive(and in many cases meaningless).
Indeed,alongthegroundsurfaceinthefree-field,“rupturesareneithercontinuous,nordo
theyfollowpreciselythesurfaceoutcropofpre-existingfaults”(AmbraseysandJackson,
1984).
In addition to several geologic factors that contribute to such behaviour, significant
appears to be the role of a soil deposit that happens to overlie the rock base through
whichtherupturepropagates. If , where ,and how large willthedislocationemergeonthe
ground surface (i.e. the fault will outcrop) depends not only on the style and magnitude
of the fault rupture, but also on the geometric and material characteristics of the overly-
ing soils.Field observations and analytical and experimental research findings (Cole and
Lade, 1984; Lade et al., 1984; Bray et al., 1994a, b; Lazarte and Bray, 1995) show that
deep and loose soil deposits may even mask a small-size fault rupture which occurs at
their base; whereas by contrast with a cohesive deposit of small thickness, a large offset
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