Experimental and modelling investigate on the behaviour of a partially saturated mine chalk

Due to seasonal environmental changes (i.e. water table, hygrometry) the pillars of mines in chalk are often submitted to variations of the degree of water saturation. These changes could affect the short and long term stability of pillars in the underground quarries. Experimental investigations have been conducted on saturated, partially saturated and dry chalk. In this context, the concepts and the methods of mechanics unsaturated soils have been applied to partially saturated chalks. Water retention properties and a series of high pressure controlled suction odometer compression tests were carried out on the samples of the chalk from the pillars of the abandoned Estreux mine (France). These results show that the yield stress of chalk increases when the water saturation decreases. They have been simulated by means of the Barcelona Basic Model - BBM (Alonso et al., 1990) allowing to account the swelling and collapse under wetting at constant vertical load