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Original Article |
1 1School
of Earth Sciences, University of Leeds, Leeds, LS23 6AJ,
UK
2 2Environmental
Resources Management Ltd, 8 Cavendish Square, London W1G
0ER,
UK
3 3GSE
Lining Technology, 37 Regal Drive, Soham, Cambridgeshire,
CB7 5BE,
UK
4 4Viridor
Waste Management, Great Western House, Station Approach,
Taunton, TA1 1QW,
UK
Desiccation
of clays can lead to the development of cracks and this is an important
issue for mineral barriers used in lining and capping of landfills. The
mechanisms of post-compaction moisture loss in a clay layer are
reviewed and the results from a field test cell investigating clay
desiccation are presented. A large scale instrumented test cell was
constructed comprising a clay layer overlain by a geomembrane. Parts of
the test cell were covered with a stone protection layer and parts of
the test cell were sloping. Temperatures throughout the clay layer,
relative humidity just above the clay, ambient air temperatures and
crack patterns and dimensions wereobserved during a 36 day
summer period. The amount of cracking was quantified using various
crack indices. Cracks in the covered and flat sections were minimal
whereas in the sloping uncovered portion cracking was initiated rapidly
and then spread until the network of cracks at the surface stabilized
and further dryingresulted in crack depth propagation. The
geomembrane, exposed to the sun, was found to have a significant
heating effect on the soil below. Significant moisture was lost over
the entire thickness of the exposed barrier resulting in a modelled
flow through the barrier of 19 times the construction value. Immediate
covering of the geomembrane was found to greatly reduce the temperature
variations, moisture loss and cracking. The results are discussed in
the context of current crack theories and implications for landfill
design and
construction.
Key Words: clay earthworks landfill microcracks soil mechanics
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