Finite element modelling of rapid drawdown

Aspects of finite element modelling of rapid–drawdown phenomena in soil slopes are discussed. The analyses involve finding the position of the steady–state phreatic surface through an earth dam, followed by sudden unloading due to reduction in water level on the upstream face. The analyses are performed in plane-strain using 8 –noded quadrilateral elements, and it is shown that in the undrained analyses, oscillations in the computed pore pressures are considerably reduced by a form of selective reduced integration. It is found that the residual pore pressure distribution after the drawdown is not uniform with higher pore pressure concentration near the toe.