Finite element analysis on piping control effect of the suspended cut-off wall in two-stratum dike foundations

Abstract

With the permeability enlargement method, we carried out Finite Element Analysis on the piping development in a double-stratum dike foundation with suspended cut-off wall. Piping initialization as well as its development, erosion domain and seepage distribution under various hydraulic head is studied for double strata. The influences of the wall’s position and penetration on the seepage control are mainly analyzed. Results show that: (1) the erosion is composed of five stages, (a) sudden local piping after the formation of a passageway exit, (b) the channel developing towards the cut-off wall, along the surface of the sand layer, (c) lateral development along the cut-off wall, (d) vertical development leaping over the cut-off wall, and (e) horizontal development after leaping over. The failure mode and mechanism remain consistent with the phenomenon observed in the flume model test; (2) piping erosion transforms from horizontal to vertical, improving the critical hydraulic head effectively and reducing the risk of the dike collapse. The wall positioned at the downstream of the dike works more efficiently; (3) the suspended cut-off wall has little influence on the erosion initialization but exerts an effective control on its development. The seepage control efficiency increases as the wall penetration increases.

Keywords

• Two-stratum dike foundations
• flume model test
• dynamic development process of piping
• finite element analysis
• suspended cut-off wall
• effect of seepage control