Briançon, stabilising the bedrock of the Fort des Têtes by injecting reinforced concrete

Although the sites are located in different settings, deterioration processes are generally the same for all. Lack of maintenance is the trigger for damage due to the following natural causes:

• The geographical and geological setting, and the climate.
• water, which is the major cause of problems such as:-
• Blocking of rain water drainage systems; water seepage causing saturation and leaching of mortar; the effects of hydrostatic pressure; and alternate cycles of freezing and thawing.
• The growth of vegetation.
• The weathering of the bedrock.

Deterioration of the exposed bedrock, often poor quality and subject to the same damage as masonry when protective topsoil has eroded away, plays a part in general wear and tear, and at times is the reason for the destruction of superstructure works.

The condition of the Briançon forts demonstrates the gradual deterioration of the defensive works and buildings. However, stabilizing the bedrock is major work for specialised enterprises and generally beyond the scope of municipal workers.

As well as stabilizing the bedrock, the facings also need to be repaired. There are several different solutions available, namely:

• to continue using stone masonry in keeping with old repair work,
• to construct reinforced concrete blocks anchored in the sound rock.