To investigate turbulent flow through confined gravelly porous media and to determine the differences between this type of flow and flow through un-confined gravelly porous media, two physical models under confined and unconfined conditions were designed and an experimental program carried out. The first model was made of a cylindrical tube filled with coarse material to study flow in a confined state and the second was a flume with free surface for study in unconfined conditions. Using these two models, experiments were carried out for a wide range of coarse material gradations from 2.83 to 56.8 mm and under different hydraulic conditions. The results show that, when primary pressure is increased, with similar velocities in both models, energy losses in the confined condition are greater than those in unconfined states. A comparison between the experimental data and the equations proposed by Stephenson (1979) and Felton - Herrera (1991), shows good agreement for free surface conditions, while the results in confined flow show greater friction factors than those predicted by the equations. The results also indicate that hydraulic conditions may be classified between two regions for the Reynolds numbers below and above 200. As a result, two sets of relationships were adopted between hydraulic gradient-velocity and discharge for different hydraulic conditions. The equations were then verified by experimental data obtained from a different series of tests, conducted for particle sizes of 7.1mm diameter, which had not been employed in the derivation of the equations. It is believed that the results obtained in this research could be applied for determination of seepage discharge as well as hydraulic gradient in coarse-grained materials in a range of diameters and hydraulic gradients given in this paper.
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