عنوان مقاله [English]
In the present paper, subsurface water profiles through coarse materials are investigated using a laboratory model. The laboratory model of a typical rock drain having 6.4m length, 0.8m width and 1m deep was prepared and then was filled using both crushed and rounded materials. For different flow rates and three slopes (horizontal, 4% and 20.3 %) of the flume, experiments were conducted and consequently water surface profiles,The upstream and exit depths of the flow were recorded. Finally the results of experimental observations were analyzed and compared with the theoretical formulas. Results showed that water surface profiles through coarse porous medium for horizontal and 4% slopes, followed by gradually varied flow theory and drawdown profiles were taken place while this theory was not valid for 20.3% slope and a uniform flow were established. Assumed critical depth to occur at the outlet of the rock drain was not approved and caused more than 200% error in gradually varied flow calculations.