Precise application of grouting technology in underground coal mining: water inrush risk of floor elimination.

Many coal mines in China suffer from the Ordovician limestone (OL) and Carboniferous limestone (CL) containing water inrush frequently due to the complex geology condition; water inrush has become a serious disaster in coal mining. To prevent water-bursting disaster from the floor of mine and cutting down deaths and economic loss, a grouting method for limestone fracture aquifer has been widely adopted. In this paper, a time-dependent empirical grouting model considering (1) time-dependent behavior of the injected slurry, (2) response of the rock, and (3) interaction between the slurry and rock was proposed to describe the slurry diffusion mechanism in rock fracture. Aiming at the problem of water disaster prevention of a coal seam floor in 16,104 working face of Luxi coal mine, that was, the grouting failed to seal the water flow channel of aquifer, the causes of the failure of grouting for water sealing were analyzed. According to the aquifer parameters and model calculation results, a grouting scheme with a slurry diffusion radius of 20 m and grouting pressure of 8 MPa was proposed; 2 rounds of grouting were implemented, following the split spacing principle, to ensure that finer fractures can be sufficiently sealed. Finally, with the comparative analysis through the network parallel electrical method (NPEM) and the drilling exploration method for water-rich areas before and after grouting, it was verified that the grouting effect for floor limestone aquifer was good, and the grouting scheme proposed and the grouting pressure designed were reasonable. Results may provide reference to a karst fractured aquifer grouting project, as well as reduced the losing because of blindness and experience.