Design Procedure of Elongated Shape Filters for Cohesionless Soils
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RESEARCH PAPER
Design Procedure of Elongated Shape Filters for Cohesionless Soils Nasir Ahmad Rather1 · Mohd Akbar Lone2 · Abdul Qayoom Dar2 · Bintul Huda Mir3 Received: 11 January 2018 / Accepted: 25 August 2020 © Shiraz University 2020
Abstract 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 d60, d10 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 d60 and d10 of the base material. Keywords Protective filters · Constriction size · Elongated particles · Shape · Effective size · Permeability · Base material · Design criteria List of Symbols a Longest dimension of the particle b Intermediate dimension of the particle c Smallest dimension of the particle Bx Base material Cu Uniformity coefficient Dx Particle size for which x % of filter material is finer dx Particle size for which x % of base material is finer d* Controlling constriction size k Permeability of filter material kt Coefficients of permeability at T °C k20 Coefficients of permeability at 20 °C m R2/R3 n R1/R3 Rx Radius of different particle spheres Sx Diameter of different particle spheres R4/R3 𝛽 * Nasir Ahmad Rather [email protected] 1
Department of Civil Engineering, Baba Ghulam Shah Badshah University, Rajouri, Jammu and Kashmir, India
2
Department of Civil Engineering, National Institute of Technology Srinagar, Srinagar, Jammu and Kashmir, India
3
Water Resources Management Centre, National Institute of Technology Srinagar, Srinagar, Jammu and Kashmir, India
µ20 Viscosity of water at 20 °C µt Viscosity of water at T °C
1 Introduction Filters are provided for the safety of hydraulic structures against piping failure and upliftment pressures. Filters are designed to allow the free movement of seepage water and prevent the migration of finer fraction of base material. The investigators have developed number of empirical equations for the design of filters. In 1922, Terzaghi developed the first design criteria for filters which was based on piping criterion (D15/d85 ≤ 4) and permeability criterion (D15/d15 ≥ 4). Since 1922, most of the investigators have developed improvements over the
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