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Significance of Cu and Cc in Evaluating Internal Stability with Application to Design of Subbase Gradation in Pavements

Kalore, SA and Sivakumar Babu, GL (2023) Significance of Cu and Cc in Evaluating Internal Stability with Application to Design of Subbase Gradation in Pavements. In: Transportation Geotechnics, 40 .

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Official URL: https://doi.org/10.1016/j.trgeo.2023.100972


The hydraulic internal stability is governed by the grain size distribution (GSD) and relative density of unbounded subbase materials. The type of GSD is characterized by the coefficient of uniformity (Cu) and coefficient of curvature (Cc). The internal stability is assessed preliminarily based on the type of GSD with only Cu limits. This study focuses on the practical utility of Cu and Cc in evaluating internal stability of unbounded materials. A relation between Cu and Cc with internal stability is developed based on the functional form of GSD, which depends on three parameters: d10, Cu and Cc. The proposed method is validated with experimental results from published literature and current study, providing a simplified assessment for preliminary investigations. The implications of the internal instability dependent on the Cu and Cc are illustrated for the three unbounded aggregate gradations typically used for subbase in pavements. The advantages of an optimum aggregate gradation with Cu equal to 15 and Cc equal to 1.7 are illustrated for the hydraulic and structural requirements. A gradation band is usually specified for subbase to allow flexibility in selecting the design gradation in standards and design guidelines. The band is constrained to limit the selection of internally unstable gradations and segregation during placement. In this paper, constraints for a gradation band are derived based on the characteristics of the optimum aggregate gradation. The constraints are illustrated with examples for a design of subbase layer gradation band dependent on the subgrade characteristics. © 2023 Elsevier Ltd

Item Type: Journal Article
Publication: Transportation Geotechnics
Publisher: Elsevier Ltd
Additional Information: The copyright for this article belongs to Elsevier Ltd.
Keywords: Cu and Cc; Filters and drains; Internal stability; Pavements; Subbase
Department/Centre: Division of Mechanical Sciences > Civil Engineering
Date Deposited: 02 May 2023 09:20
Last Modified: 02 May 2023 09:20
URI: https://eprints.iisc.ac.in/id/eprint/81242

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