Finite element method (FEM) groundwater inflow modeling associated with an unconfined aquifer into the open-pit coalmine of the Phulbari area, NW Bangladesh

This paper uses a two-dimensional finite element method (FEM) numerical modeling to predict groundwater inflow from an unconfined aquifer into the open-pit coalmine in the Phulbari area of northwest Bangladesh. The rock mass of the unconfined aquifer in the Phulbari coal deposit is highly porous and permeable. Interconnected pores within rock mass are the main paths for groundwater flow. Model assumes groundwater inflow rate through the rock mass associated with interconnected pores. Eleven stages of computation associated with variable overall pit slope angle (OPSA) 25°, 26°, 27°, 28°, 29°, 30°, 31°, 32°, 33°, 34°, and 35° are presented here. Model reveals that the probable inflow rate from unconfined aquifer in the open-pit coalmine would be about 377.68, 364.93, 354.38, 340.20, 331.29, 326.36, 316.86, 315.36, 308.03, 302.86, and 298.00 m³/h with relevant slope angles of 25°, 26°, 27°, 28°, 29°, 30°, 31°, 32°, 33°, 34°, and 35°, respectively. It is reasonable to emphasize that the computed inflow rate (m³/h) in the present numerical model would be effective through unit width of rock strata up to the pit depth of about 320 m in the Phulbari coal deposit. From the simulation results, it is thought that the open-pit coalmine in the Phulbari area would be an environmentally challenging issue because of regional unconfined mega-aquifer.