SEEPAGE FAILURE IN FOUNDATION OF WEIR WITH CUT-OFF WALLS BY MODEL EXPERIMENTS AND ELASTO-PLASTIC FEM
Keywords:
Creep flow theories, The Terzaghi’s method, Foundation of weir, Elasto-plastic FEMAbstract
Two creep flow theories, Bligh’s equation and Lane’s equation, have been commonly used to
determine the design criteria to prevent piping failure of the foundations of the weirs on soft ground. Scalemodel experiments and finite element method (FEM) analysis were applied to test the reliability of these two
methods. The scale-model experiments adopted six weir configurations in which creep length was held constant,
but the number, position and length of the cut-off wall were altered. The critical difference in hydraulic head
determined from the scale-model experiments was different for each weir configuration, despite the fact that a
constant value would be produced by both creep flow theories. Whereas the creep flow theories were unable
to represent this variation in critical head difference, FEM analysis predicted it well. The maximum shear strain
contours produced by finite element analysis indicated that shear strain was concentrated in a similar domain
to that which would be predicted by the Terzaghi’s soil mass in the calculation of seepage failure of sheet piles.
These results suggest that the Terzaghi’s method is more accurate than the empirical creep flow theories for
calculating critical head, provided the soil mass is defined correctly.