Numerical Simulation of Uplift Pressure and Relief Drains at a Dam Reservoir

Abstract

The Melen Dam in under construction to support the water supply to Istanbul Metropolitan city. Karstified limestone that forms the major aquifer in the region crops out at the right bank of the reservoir and extends to the adjacent basin where it is drained by two main springs. An area of 20 ha that is covered by this limestone is planned to be lined by concrete slabs. Another spring that discharges within this lining area will be plugged by the concrete slabs. As a consequence, piezometric pressure is expected to build up underneath the concrete lining which will develop an uplift pressure. Prediction and relief of the uplift pressure is of utmost importance in optimizing the concrete lining. This was achieved by numerical simulation of the pre-lining and post-lining conditions at the site. This required development of a representative hydrogeological conceptual model as the very first stage. The conceptual model was then transferred to a numerical model through the software Seep/w of GeoSlope™ version 2007. The optimal design of the concrete lining was developed after performing a number of numerical simulations on the calibrated model. The model suggested that the uplift pressure would be relieved to an acceptable level by construction of drains underneath the concrete slabs at certain locations.