A comprehensive review of the literature provided much evidence of the success of lime
piles in treating both soft ground and slopes. The mechanisms of stabilisation
postulated by researchers is often contradictory or misleading. The use of the literature
for the basis of a definitive experimental programme was not possible.
An iterative approach was adopted for the laboratory programme whereby the results
from one series of tests were used in the design of the next. This resulted in a range of
tests including full-scale box loading tests in which lime piles were installed in clay
samples, model scale lime pile tests and soil element tests.
The stabilising mechanisms that have been established by the laboratory study are:
generation of negative pore water pressure, overconsolidation of the shear zone, clay
dehydration, pile strength and increased strength of stabilised clay due to lime
migration. These mechanisms combine to improve any particular clay slope containing
one or more shear zones.
Three field trials were conducted. A small-scale trial was carried out on a canal cutting
and provided useful data regarding pore water pressure changes and installation
processes. Quantitative data produced by the laboratory study, were used to design
two further trials. One trial treated a 30 m stretch of failing slope using a single
'Minuteman' rig (small and lightweight plant). Quicklime was 'poured' into open holes
and compacted by the drill operators. Work was complete within two weeks. The
third trial, again sited on a canal cutting, was carried out using a much larger rig. One
hundred and fifty 200 mm diameter piles were constructed to a depth of 3 metres within
a two week period. Monitoring of pore water pressures on both sites is still occurring
on a regular basis. Excavation of sections of both trials at some future date will
provide additional data on stabilising mechanisms.
The research has considerably extended the understanding of the mechanisms
controlling lime pile stabilisation, particularly when applied to failing slopes in British
soils. Areas where further research would improve this understanding have been
highlighted and in some cases work is already underway.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.