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Assessment of dewatering / depressurization requirements for the Çeltikci Coal Basin, Ankara - Turkey

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2019
Peksezer Sayıt, Ayş
The dewatering requirements and their anticipated impacts on groundwater resources were evaluated for both open pit and a representative longwall panel using a 3D numerical groundwater flow model developed by FEFlow software. Eleven years of mining in the open pit was simulated by hydraulic head boundary conditions, whereas the modulation functions were used to de-/activate boundary conditions according to mine advance. The simulation results indicate that average groundwater inflow rate to the open pit is 79 L/s excluding the effects of direct rainfall and surface water flow from the benches. The impact of 11 years of mining in the area is evaluated in terms of (i) timewise change of baseflow component of Kirmir stream, and (ii) areal distribution of cone of depression. The longwall mine simulations, on the other hand, were conducted for a representative panel, where modulation functions are used to simulate the mine advance and time varying material properties are utilized in the simulation of changes in hydraulic parameters. Six different simulations were conducted where the complexity in the system that will result from longwall mining was increased progressively. The average groundwater inflow to the panel ranges from 261 L/s to 444 L/s based on the simulation results. The impacts of longwall mining are assessed in terms of (i) simulated water table profile at the end of mining, (ii) areal distribution of the cone of depression and (iii) timewise change of simulated hydraulic head values at the monitoring wells in the vicinity of the panel.