Influence of rock mass hydraulic properties and jointing pattern on hydromechanical behaviour of gravity dams

Abstract

In concrete dam foundations, rock mass discontinuities and spatial variations in permeability give rise to complex seepage patterns, making monitoring and safety evaluation particularly challenging. An accurate safety assessment of concrete gravity dams requires the use of coupled models that: • capture the interaction between mechanical and hydraulic behaviour; and • effectively simulate the geometry and properties of rock foundation discontinuities. In this study, a coupled hydromechanical analysis is performed on four gravity dams of two different heights using Parmac2D-Fflow, a fully coupled 2D numerical model capable of simulating discontinuities in the foundation, as well as the effects of grout curtains and drainage systems. Numerical simulations were carried out by gradually increasing the water head at the reservoir bottom and applying the corresponding hydrostatic pressure to the upstream face of the dam, thereby simulating the reservoir filling process. This loading phase was followed in all cases by an unloading phase, representing the subsequent emptying of the reservoir. The analyses were conducted under various behavioural scenarios, accounting for a non-linear response at the dam/foundation interface and both linear elastic and non-linear behaviours within the foundation. Several key parameters were investigated, including joint pattern, joint stiffness, strength of the dam/foundation interface and hydraulic properties.