Design Procedure of Elongated Shape Filters for Cohesionless Soils

The present study is an attempt to develop design criterion of elongated shape filters for cohesionless bases on the basis of controlling constriction size of filters. The existing design criteria are based on certain particle size ratios of filter and base material and controlling constriction size. Recently, few studies have been carried out in which blade, rounded, irregular, sub-rounded and elliptical shape filter particles were considered for development of filter design criterion for these shapes. In the present study, the elongated shape filter particles and cohesionless bases were considered for the laboratory tests. It was observed on the basis of experimental results that the elongated shape filter particles are suitable for protecting the cohesionless bases. The experimental results indicate a relationship between d 60 , d 10 of the base material and the design controlling constriction size d * of the elongated shape filter material. An empirical model has been developed for determining d * of the filter material based on d 60 and d 10 of the base material.