Determination of hydraulic conductivity for granular filters based on constriction size and shape parameters

This experimental study is an attempt to apply the constriction size concept for determination of hydraulic conductivity of filter material. Five shapes of granular filter material of different gradations were used for the experimental investigations. The controlling constriction size for selected shapes and gradations were worked out and related to the experimental values of hydraulic conductivity. The empirical model for determination of hydraulic conductivity based on controlling constriction size for each shape of granular filter material was developed. Finally, a combined empirical model for the determination of hydraulic conductivity of granular filters was developed based on shape parameters and the controlling constriction size. The model was validated with the experimental data of a past research work; the predicted values of hydraulic conductivity were found in close approximation to the values obtained from the literature. Results of the present work will help in improving the existing design criteria of protective filters, which form an integral part of the safety of hydraulic structures.