ABSTRACT
The end of the extraction activity of mines often leaves abandoned cavities in the ground which may induce risks of collapse of the soil. Filling of the cavities is a obvious solution to put under safety the area above the abandoned mine. Nevertheless, this operation may be quite complex when the accessibility is limited. An example is the former gypsum mine of Carale, located in the village of Santa Brigida in Northen Italy [1]. The mine was excavated with the chamber-pillar technique and it consists of four levels, three of which are underground (Figure 1). The extraction activity was terminated in 1972 and since then the two lower levels are flooded by water, coming from permeable carbonate layers present above the excavated area. The continuous flow of significant amount of water causes the dissolution of the gypsum and anhydrite, leading to the slow reduction in section of the pillars. The removal of the water and its substitution with a material able to set and harden should interrupt the dissolution of gypsum and anhydrite and prevent the collapse of the tunnels [1-2]. This paper describes the laboratory studies made for the development of an appropriate cementitious mixture and its characterisation in the fresh and hardened state.
