When there is an impermeable layer between the bottom of the excavation and a deep aquifer (see Figure below), the ground water head at the aquifer below the subgrade might be sufficiently high to cause soil layers to lose strength and fail. In this case, a depressurizing system or relief well system should be carefully designed to ensure that “piping” or “boiling” does not occur at the bottom of the excavation.
Griffin professionals can determine the required drawdown to provide a safe subgrade and design a system to relieve the artesian aquifer pressure and satisfy the safety requirements of the jobsite.
Uplift pressure diagram
Case Study in Pasadena, TX: Depressurizing Well Design and Drawdown contours, using MODFLOW.
Pressure calculation using 2d simulation
Pressure calculation using 2D simulation for two scenarios of relief wells arrangement downstream of a dam. Case study in Texas.