BEHAVIOR OF PARTIAL SEEPAGE BARRIERS IN HIGHLY PERMEABLE SOILS

Numerical analysis is carried out to study the deformation of partial seepage barriers in highly permeable soil. Plaxis 2D software is used to analyze the chosen numerical model of a diversion dam with suspended type diaphragm cut off walls formed in sandy soil. The depth of downstream cutoff wall and differential pressure head across the diversion dam are kept constant. The depth of upstream cutoff wall is made to vary from 0m to 15m and consequent effect on deformation pattern of downstream cutoff wall is studied. On increasing the depth of upstream cut off wall, the deformation at top end of downstream cutoff wall reduces at decreasing rate up to 9m depth and beyond that it increases at increasing rate. However, the bottom end deformation reduces almost uniformly throughout. On increasing the depth of upstream cutoff wall, the pressure head acting on downstream cutoff wall decreases but deformation increases. This increase is due to the seepage dynamic force acting on the seepage barriers despite the reduction in pressure head acting on them. On increasing the depth of upstream cutoff wall, the direction of stream flow gets mostly oriented from downward to horizontal direction, thereby increasing the magnitude of horizontal component of seepage forces acting on the downstream cutoff wall and exerts dynamic force which is more predominant than the pressure head acting on seepage barrier