Hydrodynamic behavior of Soremeh Carbonate Formation on groundwater inflow to Nowsud Tunnel in Zimkan valley region, Kermanshah

Groundwater control is an important issue during underground excavation in fractured rocks. More than any other factor, the lack of groundwater control can cause costs to rise.
In this study, the characteristics of the Surmeh Formation in Zimkan aquifer were analyzed using the recession curve of discharge water from the tunnel. The results show that behavior of the recession curve of discharge water from the tunnel is similar to discharge of the conduit flow system of karst springs. In the first seven days, the slope of the recession curve was high and equal to 0.041, but over time in considering to progress of tunnel excavation and 41 meters groundwater table drawdown in karstic aquifer of Surmeh Formation; the slope of the recession curve decreased and it became similar to diffuse flow system of the karstic aquifer. In the recession curve of discharge water from the  Nowsud Tunnel, all three porous systems, including conduit, semi conduit and diffuse are properly identifiable in time intervals of seven, 48, and 87 days respectively. with respect to similarities in the behavior of discharge water from the tunnel with karst springs, the hydrograph of recharge water into the tunnel can be used as a discharge below the base level of the karst hydrologic system in order to assess the dynamic reserve of the upper karst aquifer (above the tunnel level).