Optimized Control of Seepage and Deformation in a Dam Foundation on Thick Overburden Deposits Considering Coupled Hydromechanical Effects

Abstract

Dams are often constructed on thick overburden deposits when a complete removal of the overburden becomes cost-prohibitive. This may induce an intense coupling between seepage and deformation in the deposits owing to their high permeability and poor mechanical properties. In this study, a coupled transient flow and nonlinear elastic deformation model is used to evaluate the design of the cutoff wall and foundation treatment for a concrete sluice dam of 42 m height located on 133-m-thick overburden. It is found that the depth of the cutoff wall has a significant effect on seepage and deformation control in the dam foundation, and a closed cutoff wall of 120 m depth performs much better than suspended ones with smaller depths in terms of the control of flow rate, uplift pressure, and seepage-induced uplift deformation. The backfill treatment of the top two overburden layers is crucial for controlling both flow rate and settlement, and the bored piles help reduce local settlement at the powerhouse foundation. Due to the relatively smaller height of the dam, the foundation deformation is less sensitive to permeability models. The results provide an important guidance for optimization design of the dam foundation treatments.