Evaluation of actual and estimated hydraulic conductivity of sands with different gradation and shape.

Ali Firat Cabalar,Nurullah Akbulut

doi:10.1186/s40064-016-2472-2

Ali Firat Cabalar, Nurullah Akbulut

Open Access

https://doi.org/10.1186/s40064-016-2472-2

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Journal: SpringerPlus	Publication Date: Jun 21, 2016
Citations: 34	License type: CC BY 4.0

Affiliation: Hasan Kalyoncu University, Gaziantep University

Abstract

Hydraulic conductivities of sands with different gradation and grain shape were estimated experimentally at a relative density (Dr) of about 40 % and a 22 ± 2 °C of constant temperature. Narli Sand (NS) with 0.67 of sphericity (S) and 0.72 of roundness (R), and Crushed Stone Sand (CSS) with 0.55 of S and 0.15 of R values were artificially graded into sixteen different grain-size fractions (4.75–2, 2–1.18, 1.18–0.6, 0.6–0.425, 0.425–0.3, 0.3–0.075, 4.75–0.075, 2–0.075, 1.18–0.075, 0.6–0.075, 0.425–0.075, 4.75–0.6, 2–0.6, 4.75-0.425, 2–0.425, 1.18–0.425 mm). Hydraulic conductivities of the NS estimated by use of constant head test ranged from 1.61 to 0.01 cm/s, whilst those of the CSS estimated by the same test ranged from 2.45 to 0.012 cm/s. It was observed that the hydraulic conductivity values of the NS are lower than those of the CSS samples, which is likely to be the result of differences in shape, particularly in R values. The results clearly demonstrated that the hydraulic conductivity can be significantly influenced by grading characteristics (d10, d20, d30, d50, d60, cu, cc, n, Io). Furthermore, comparisons between results obtained in the present study and hydraulic conductivity estimated with other formulas available in the literature were made. The comparisons indicated that the best estimation of hydraulic conductivity changes based on the gradation and shape properties of the sands tested.

Highlights

Hydraulic conductivity, which represents the ability of a porous media to transmit water through its voids, is one of the most significant key parameters of geomaterials for many natural phenomena including the management of water resources, drinking water supply, safety of waste repositories, basin-scale hydrogeologic circulation, stability analyses, and many other problems on subsurface hydrology and geotechnical engineering (Terzaghi and Peck 1964; Moore et al 1982; Wintsch et al 1995; Person et al 1996; Boadu 2000; Chapuis 2012)
The authors consider that influence of the parameter cu was neglected in his study, and thereby the grain size distribution results could yield the same cu for various sands
The authors employed the original Kozeny–Carman equation, the Table 3 released that hydraulic conductivity values ranged from 4.93 to 0.02 cm/s for the Narli Sand (NS) samples, while those ranged from 12.36 to 0.03 cm/s for the Crushed Stone Sand (CSS) samples falling the same gradations

Summary

Introduction

Hydraulic conductivity, which represents the ability of a porous media to transmit water through its voids, is one of the most significant key parameters of geomaterials for many natural phenomena including the management of water resources, drinking water supply, safety of waste repositories, basin-scale hydrogeologic circulation, stability analyses, and many other problems on subsurface hydrology and geotechnical engineering (Terzaghi and Peck 1964; Moore et al 1982; Wintsch et al 1995; Person et al 1996; Boadu 2000; Chapuis 2012). Empirical (Hazen 1911; Krumbein and Monk 1942; Alyamani and Sen 1993) and predictive methods (Kozeny 1927; Carman 1937; Boadu 2000; Goktepe and Sezer 2010) of estimating the hydraulic conductivity. A commonly accepted equation was proposed by Hazen (1911) and given k = cd120 for predicting the hydraulic conductivity of saturated sands. Krumbein and Monk (1942) gave an expression for the hydraulic conductivity of unconsolidated sands by an empirical equation of the form k = (760d2w)exp(−1.3σψ), where dw is geometric mean diameter by weight in millimetres, σψ is standard deviation of the ψ distribution function. Kozeny (1927) and Carman (1937), which is widely accepted derivation for hydraulic conductivity, developed a semi-empirical formula for predicting the permeability of porous media. Many different techniques have been proposed to determine hydraulic conductivity value, including field methods, applications of these empirical formulae to the same porous medium material can yield different values of hydraulic conductivity because of the difficulty of including all possible variables in porous media (Vukovic and Soro 1992)

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Conclusion