A case study on the height of a water-flow fracture zone above undersea mining: Sanshandao Gold Mine, China

In undersea gold mines, the development of a water-flow fracture zone and its connection with the aquifer may cause massive water and sand inrush disasters. In this study, approaches including theoretical analysis, numerical simulation and field detection are employed to identify the development height of the water-flow fracture zone caused by undersea mining in the Xinli Zone of the Sanshandao Gold Mine to ensure mining safety. An improved Winkler elastic foundation beam model, considering the coupled influences of seawater pressure and backfill support, was established to calculate the height of the water-flow fracture zone. The result demonstrates that the height of the water-flow fracture zone depends on the elastic modulus of the overburden strata and the compression modulus of the filling material. Then, an experimental study utilizing a custom-made apparatus is conducted to obtain the Winkler foundation compression characteristics of the filling material used in the gold mining operation. The theoretical analyses are confirmed by numerical simulations and show that the height of the water-flow fracture zone decreases with the increase in mining level because the loads from overburden weight decreases with the mining depth. The theoretical analysis, numerical simulation and field detection present that the height of the mining-induced water-flow fracture zone is 39m, 37m, and 40.5-45m, respectively, after mining at the -135m level. These values are reasonably consistent, suggesting that the proposed theoretical and numerical models and the utilized field detection method can provide valuable information for determining the overburden stability of an undersea mineral seam and improving mining safety.