Saving Mingary from Collapse - 1

The great curtain walls of Mingary Castle are on the point of collapsing because the rock on which they are built, a very hard granophyre, is breaking into blocks which are falling apart - see earlier blog entry here.  To stop this happening - and it might happen at any moment - the blocks have to be pinned back in place, and to do that the Mingary Castle Preservation & Restoration Trust have called in some experts.

Vertical Technology is a Portsmouth-based company which specialises in, as they put it, "undertaking works complicated by height and difficult access."  This includes a wide variety of jobs from painting bridges to pinning back rock that might fall onto a road, from cleaning stonework on the faces of high city buildings to inspecting inaccessible structures such as steel bridges, and dealing with crumbling castles - they've worked on Lulworth and Old Sarum in the past.

The team which has come to Mingary are, from left, Roger Picolo who comes from Andorra, John Willis who used to instal solar panels, Tony Cottrell, an ex-fireman, and team leader Simon Scales, an ex-salesman of surf-boards.  They may have come from a variety of backgrounds, but all have considerable experience with Vertical Technology and are trained to the International Rope Access Trade Association's very high standards - Simon, as team leader, has been with VT for five years and is IRATA Level 3.

They start by removing a core about 4" in diameter and 6" deep.  They then drill a 35mm or 45mm hole  to a depth of 2m, 3m or 4m until they reach solid rock deep under the castle.  Either resin or grout is then injected, and a threaded stainless steel rod inserted before the resin/grout sets.  Once it has hardened, a 4" 'washer' is slipped over the protruding end of the steel rod, and a nut screwed onto it, heaving the rock back into place.  Finally, the 4" core is fitted back into the hole, concealing the top of the rod.

When they first started work last week, the main problems they contended with were the juddering of the drill and the deafening noise, but then they were only experimenting at an easily accessible location - the castle moat - to see what the rock was like.  But when I went down today to see how they were getting on, the team was working under the west wall, and that was.... impressive.

To be continued....