Project and Fieldwork 2005
Spittal - year 2
The second season at spittal quarry concentrated on putting the experimental data derived from 2004's work on the cairn elements into practice. The first step involved clearing away the remains of the previous seasons work and the erection of a second set of orthostats. This done a level platform was constructed from which to spring the corbelled chamber walls.
John Barber's work at 'Point of Cott' stalled cairn suggested that the lowest coarse of the corbelling in each bay of the chamber had been arranged to form a shallow horizontal arch with the front edge of each stone tilted up on small stone. The weight of the superstructure would force the small stones into the underlieing ground surface causing the arch-length to increase as it tended to flatten. This resulted in the corbel tending to wedge between the orthostats thus locking the whole structure together.
In the spittal reconstruction, the combined effect of the small tilting stones and the 'give' of the natural ground surface was simulated by the insertion of a strip of 50 mm square-section expanded polystyrene (see centre image below).
On completion the cairn was fully surveyed; this allowed any subsequent settling of the structure during the winter of 2005/2006 to be detected and evaluated.
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