I am working on a fascinating project in Western Australia where we are looking at consolidating some limestone.

We have an 1831 building on top of a headland adjacent to the harbour.  The building is constructed of limestone blocks quarried from the headland.  Most, but not all, of the blocks were caprock, the hard calcrete which occurs just below the surface of recent limestone deposits.  This also occurs across the top of the headland.

The rock below the caprock is very soft sandy limestone.  Where it has begun to weather, the binding strength has gone, and we are left with grains of sand and fossiliferous material.  The result is cliff-faces which erode back beneath the caprock.  The overhangs eventually fall, and the process begins anew.

The problem we have is that this has been determined by others to be a very significant heritage site.  Our challenge is to find a way to conserve the building AND the cliffs.  At the same time, we have to maintain public safety in a manner which probably does not encompass restriction of access to the areas below the cliff-faces!!  And in a society where there are recent tragedies involving collapsing limestone cliff-faces killing children on a school outing.

We are looking at some innovative calcite deposition techniques, and hope that these may have some success.  We will probably use some geotechnical rock bolting or rock nailing (oversize pins) techniques.  We are also exploring using 'traditional' stone masonry techniques such as replacement and indenting, particularly on the building, and patching with a repair mortar of some form is also very likely.

We do not want to explore the use of silanes or other organic consolidants ... we do not have the money for a start, and there are too many things that could go wrong.

Any thoughts, suggestions, ideas from left field.  I thought about a car bomb in the tunnel which runs through the cliff below the building, but the problem with that is that most of the blast will come out the ends of the tunnel!  Seriously though, we are on the spot, so the collective brilliance of BP is now being sought for some assistance!

Look forward to hearing your suggestions.

david

PS  Photo attached in JPEG format.  Top right is the top of the building.  Across the centre of the photo runs part of the cliff - this is an area which was quarried about 70-100 years ago.  The tunnel opens from about two-thirds of the way across the picture (from left to right).