2126
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
may be deemed necessary to protect the wall. However due to
their voided nature these walls often need more grout than
initially estimated and there is no guarantee that the grouting
ot be assumed that adjacent
the form of a failed
le to be made about the
anted
ll was built, as with
res, and this has continued through the
ers so that even today new materials
and Fairley 1978, Cody and Cody 1972,)
5 CONCLUSIONS
cientific work to date, but regional construction
f Dry Stone Retaining Walls.
MEng
rnier, D. 2010. Full-scale Field Trials to
Mousehole-West Cornwall, Available from:
ournal,
Vol. 19. pp. 180-184.
g Structures, 45.
of Civil Engineers-Geotechnical
ngineering,
162 (4), pp. 203-212
Reilly, M.P., Perry, J., 2009. Drystone Retaining Walls and their
Modifications – Condition Appraisal and Remedial Treatment.
CIRIA,
London.
Tufnell, R.,2012. Dry Stone and the Sea: Techniques and Traditions of
Dry Stone Harbours and Jetties in the British Isles.
13
th
International
Dry Stone Walling Congress
(Unpublished at time of writing)
Villemus, B., Morel, J.C., Boutin,C. 2007. Experimental Assessment of
Dry Stone Retaining Wall Stability on a Rigid Foundation.
Engineering
Structures.
Vol.29, pp. 2124-2132.
has been done sufficiently to fill all the voids in a wall. It is also
difficult to know where the injected grout ends up. Grouting
not only stops the draining of water that enters the wall through
wave and sea action, but also most harbour walls retain land
behind them so that the grouting will also prevent the drainage
of groundwater, which as before exerts extra pressures on the
wall and potentially causes failure.
Figure 5. Grouted wall of vertical construction at Port Gavern, Cornwal
A general difficulty of assessing walls which have failed is
that due to their un-mortared nature, all that is usually left of a
failed section of wall is a pile of rubble that is almost
impossible to analyse, and it cann
standing sections give a true indication of
section. Some judgement may be ab
foundations or conditions of the backfill but little can be said
about the wall. Increasing the understanding of how these walls
work as well as improving assessment it may make it easier for
engineers to use drystone walling in new build projects or to
replace existing damaged walls, rather than their more modern
and less sustainable counterparts.
3.1
Appearance Vs. Wall Quality
When assessing a drystone wall much weight might be given to
the appearance of the wall at its face. This can be deceiving,
especially as the way in which walls are finished is likely to
have changed over the years. It is likely that the majority of
walls built a hundred years or more ago had greater emphasis on
function, whereas aesthetics are likely to be an important factor
in choice of drystone walling today. This means that quality of
the aesthetics is easily taken as a proxy for quality of
construction, but just because the wall face looks even and is
cleanly finished does not mean that the wall behind will be to
the same standard - and vice versa. For example, wallers cite
cases where freestanding walls have appeared to be well
constructed and have a good finish but have failed within
months of being built, because instead of being constructed with
properly packed filling they have been filled with pea shingle
with no through stones, preventing the wall from performing as
a monolith. In another case a waller was asked by a client to
build a small retaining wall which was to have a hedge pl
in front of it, so ultimately was not worried about the finished
appearance of the wall. He also did not want any wastage of the
stone, whereas normally a certain amount of stone is left at the
end where stones have been shaped or just not used in the wall.
However this wall was built to no less a standard than other
walls he had built for the same client which had a very high
quality of finish to them.
4 THE SUSTAINABILITY OF DRYSTONE WALLS
As with most constructions the sustainability of drystone walls
must also be considered. When considering drystone structures
this will also include the ecology impacts of the walls providing
habitat and shelter for both animals and plants.
Drystone walls are naturally very sustainable structures and
with the current imperative of low carbon structures are an
almost ideal solution. Their main advantage is a lack of mortar,
this not only means that the walls lack the embodied carbon
associated with the mortar, but that when repair or rebuild is
required very little if any new material is required. This does
however depend on the stone type; or example a limestone wall
is more likely to need some new material as limestone is prone
to decay from water and frost. Traditionally walls have been
built with materials local to where the wa
mo t vernacular structu
generations of wall build
s
are usually obtained from local quarries or sources well known
to the waller. This means that there is minimal transport of
materials, thus reducing the embodied carbon within a drystone
wall. Drystone walls also provide an excellent habitat for a
variety of animals and plants and various research has been
carried out where drystone walls have been highlighted. (Hynes
Drystone retaining walls of horizontal construction have
dominated s
styles which have developed in response to the type of stone
available or particular requirements may behave in significantly
different ways. It is important that these differences are
understood if the stability of walls is to be asssessed correctly.
6 REFRENCES
Bailey, C. 2008. Model Tests o
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Hynes, J.A., Fairley J.S. 1978. A Population Study of Fieldmice in Dry-
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Mundell, C. 2009. Large Scale Testing of Drystone Retaining
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