| dc.description.abstract | Diaphragm walls are being used increasingly in connection with building basements
and road improvement schemes, particularly in urban areas. Many of these walls
retain overconsolidated clay, and the magnitude of the lateral stresses which will act
on the wall under service conditions is uncertain.
One of the reasons for this is that, although the initial in situ lateral effective earth
pressures in an overconsolidated clay deposit will be high, they will be affected to
some extent by the process of installation of the wall. Stress relief which occurs
during installation should be taken into account, since it will influence the starting
point for analysis of the post-construction behaviour. Ground movements which
occur during installation are important in their own right, and might for a diaphragmtype
retaining wall be more significant than those which occur during and after
excavation in front of the wall. The investigation of this problem using a centrifuge
modelling technique is the principal aim of the current research.
An extensive literature review has been carried out to collate field data concerning the
stress history and in situ lateral stresses of overconsolidated clay deposits. These were
used to confirm that the proposed centrifuge modelling technique would achieve
realistic stress states and changes in stress.
A series of centrifuge tests has been carried out at the London Geotechnical
Centrifuge Centre (operated jointly by Queen Mary & Westfield College and City
University), on samples of overconsolidated speswhite kaolin, simulating the effects
of excavation under a slurry trench and concreting the diaphragm wall. The
background to the tests, and the geometry and design of the model are discussed. The
influence of the groundwater level and panel width on ground movements and
changes in pore water pressures during diaphragm wall installation have been
investigated, and the results are presented. The centrifuge test results are compared
with field data from various sites. The development of a simplified analytical method
is presented, which may be used to estimate the installation effects of diaphragm walls
in clay. The results of this analysis are compared with the centrifuge test results and
field data.
Finally, some areas of continuing uncertainty are highlighted and some suggestions
for further research are made. | en_US |
