Estimation of Uplift in Cracks in Older Concrete Gravity Dams: Analytical Solution and Parametric Study

Abstract

An analytical solution is proposed to model the internal uplift pressures associated with cracks in older concrete gravity dams and assess drain effectiveness. Each crack is assumed to be finite, rectangular with constant aperture and surface properties and in direct hydraulic connection with the water in the reservoir. Flow in the crack is laminar, steady and is a potential flow. The crack is intersected by a single drainage well or a line of drainage wells. A parametric study is presented to study the effect of the following parameters on uplift: (1) Crack elevation, entrance head, geometry, aperture, and roughness; (2) drain radius and location; and (3) drain boundary conditions, i.e. constant head as dictated by the elevation of the dam drainage gallery or constant flow rate induced by pumping. It is found that drainage wells are effective in reducing crack pressures and therefore uplift.