Prediction of Rock Swelling Behaviour

The swell amount expressed by swell deformation or by swell stress of a swelling rock depends on the degree of saturation at the moment of wetting. Partial rock desaturation due to tunnel ventilation is a phenomenon that inevitably occurs during construction of underground structures. It means that in order to predict the swelling rock behavior, the form, the extent and the character of the unsaturated zone must be known. The laboratory tests described here provide information for determining the necessary parameters. The desiccation and swelling studies were performed on swelling rock samples collected at the Muvrinski Jarak location near town of Kutina, Croatia. The experimental results have demonstrated that a saturated swelling rock does not swell and that upon desaturation its swelling potential is realized in contact with water. The numerical model used to predict moisture distribution within the desicating sample provides a realistic description of the process. The study provided a quantitative prediction of the effect of drying on the rock swelling.