Results of experimental research of surface danger of the terrain over underground log dumps are given. Time influence and rock structure influence on surface deformation were analyzed for the purpose of solving rock stability. The example of solving underground cavities influence on surface by using equivalent modelling method is described. This way enables us to take geotechnic route, influence of driving advance and the method backfilling into consideration. The method is convenient for evaluation of landslide effects and for safeguarding measures. 9 figs.