The floor heaving phenomenon occurs during drivage and use of every underground mine working or tunnel. Although it is not a natural hazard and it’s not dangerous for the staff, in some cases its intensity is so big, that it makes it impossible to use a working from the point of view of transport or ventilation. Considerable tunnel convergence and considerable decrease in its dimensions can lead to the suspension of activity in the working and also incur additional costs of the partial support replacement and a floor dinting.
Floor heaving is very often caused by floor rock being soaked and its gradual degradation, especially in clayey rock. Then there is a reduction of the floor rock strength and the change of rock mass quality.
The paper presents the new modelling method for waterlogged rock. The modelling was executed in a two dimensional state of strain for workings in a coal mine. For quantitative assessment of the rock mass parameters and their reduction due to water influence, first  laboratory investigations were carried out. The Young modulus, Poisson ratio and compressive and tensile strength of floor clay stones were tested after 3, 6, 12 and 24 hours of submerging rock samples in water. Then, during modelling the mechanical rock parameters in a de-stressed area in a floor were gradually decreased until the damage zone in the floor didn’t change and the rock parameters were the lowest. The efficiency of the method was tested in two coal mines. The final results of numerical calculations differ to the underground measurements no more than 11%. Hence, the developed method can be used successfully in both roadways and tunnels.

floor heaving, floor heaving modelling, underground measurements, floor rock soaking, underground working stability