Abstract
Stability of riverbanks under three unsteady river flow conditions is simulated. First is the case of constant water level in the river, second is the case of filling the river to the riverbank top and finally the case of drawdown. Two modes of drawdown are analyzed; the rapid drawdown and the slow drawdown. A finite element model of saturated unsaturated seepage flow was de-coupled with a plain strain elastic-plastic finite element model using strength reduction technique to calculate the stability factor of safety (FOS) of bank material. The influences of location of phreatic surface, pore-water pressure, drawdown rate and ratio on the riverbank stability are discussed in details for each case. Results showed that safety factor for saturated riverbank is nearly 83% of its dry value (for the studied case). The case of filling is most likely to stabilize the riverbank. For the case of slow drawdown, the minimum FOS occurs when the water depth is about 0.25~0.3 the bank height. The case of rapid drawdown is the most critical case.
