عنوان مقاله [English]
نویسندگان [English]چکیده [English]
One of the main reasons of destructing the coastal slopes and riverbanks is failure of side slopes under the rising the water table or sliding the side slopes under the drawdown of channel water. In this research, effect of variations of water table and channel water level on the piping of coastal slopes was studied and effect of cutoff wall on the phenomenon was investigated in the conditions. The experiments were conducted in a seepage tank with physical model of a trapezoidal section including 1.5 side slope and 0.58 mm mean diameter of the particles. Cutoff wall was fixed in the relative depths Z/d=0.5, 0.67, 0.83 and 1. Results of peak conditions of flood showed, in the control experiment, piping was observed in the all relative channel water level except the relative channel water level equal to y/d=0.7. In the experiment with cutoff wall Z/d=1 and without occurrence of piping, exit flow gradient was decreased approximately 41 present with respect to the control experiment. Results of drawdown conditions of flood showed, in the control experiment, piping was observed in the all channel water level. In the experiments with cutoff wall, in the cases with high water table, despite of existence of cutoff wall, increasing the exit flow gradient caused to piping in the all of the experiments because of increasing the hydraulic head. Other wise, in the experiment with the relative water table equal to h/d=0.933, piping was occurred in the all depths of cutoff.