Coupled hydro-mechanical analysis of a dam foundation with thick fluvial deposits: a case study of the Danba Hydropower Project, Southwestern China

TLDR

The Danba Hydropower Project in Sichuan, China, is planned on thick fluvial deposits up to 133 m, whose loose, heterogeneous nature makes seepage flow and settlement control critical challenges. The study models coupled groundwater flow and deformation using finite element analysis to assess seepage control and foundation treatment performance. The model employs an adaptive variational inequality formulation of Signorini's condition for saturated flow, a Duncan–Chang non‑linear elastic E–B model with Goodman interfacial elements for deformation, and a Kozeny–Carman-based permeability variation to capture soil–structure interactions. The numerical results indicate that the designed seepage‑control structures are effective and settlement is limited to within 20 cm using proper foundation treatments.

Abstract

The Danba Hydropower Project, located in Danba County, Sichuan Province, China, was planned to be constructed on a thick fluvial deposit foundation, with a maximum depth of the deposits up to 133 m. The loose deposits are characteristic of complex origin, composition, distribution, and mechanical and hydraulic properties. The controls of seepage flow and settlement in the foundation become two key technological issues for construction of the dam. In this study, the coupled processes between groundwater flow and deformation were modelled with the finite element method for performance assessment of the seepage control system and the foundation treatments. The saturated flow process was formulated with an adaptive variational inequality formulation of Signorini's condition, which eliminates the singularity of the seepage points and the resultant mesh dependency. The deformation response of the loose deposits was described using the Duncan–Chang non-linear elastic E–B model, together with the Goodman interfacial elements for simulation of the soil–structure interactions. The stress-dependent variations in the permeability of the loose deposits were considered on the basis of the Kozeny–Carman's model. The numerical results indicate that the designed seepage-control structures are effective and the settlement is limited within 20 cm using proper foundation treatments.