Modeling of Floor Heave in Underground Roadways in Dry and Waterlogged Conditions

Abstract

Floor heaving is a phenomenon that occurs in almost all mining roadways and tunnels. It can restrain the advance of the heading face or cause serious problems during roadway use. The highest levels of floor uplifting are observed in coal mines, which can reduce the output or even stop it altogether. The floor heaving intensity depends on the rock type, the stress in the rock mass, and rocks’ mechanical properties. Floor deformation develops when the secondary state of stress is formed around the working, and it is much higher and more dynamic in the case of waterlogged rocks. The presence of water increases the floor’s propensity to heave, especially clay rocks, such as claystones or mudstones, if they include water-absorbed minerals. In this paper, we present a new modeling methodology for roadway floor heave. The modeling covers a dry floor condition in which the parameters of the Hoek-Brown failure criterion are gradually lowered over time, and a waterlogged floor condition, in which the strength and strain parameters of the rocks are gradually reduced in line with their progressive saturation. In the second case, the claystone floor’s geomechanical parameters were investigated, and the rocks were subjected to water for up to 24 h. The results of the numerical simulation were compared with the in situ measurements of convergence and floor heave in the same coal mines from which the rock samples were collected. The consistency between the numerical simulations and the underground measurements reached 90–99%.