Abstract
Recent research on the behavior of gravelly sands advocate for the use of the skeleton void ratio to characterize their density state. The skeleton void ratio corresponds to the void ratio of grains constituting the stress-bearing skeleton. However, such a void ratio relies on parameters difficult to determine in practice, such as the fraction of fine grains that take part actively in the load bearing skeleton. Also, it fails to consider the effect of grain-size distribution (GSD) of gravel and sand grains. Therefore, the skeleton void ratio index introduced by Chang et al. as published in 2015 is revisited to account for the effect of GSD of both gravel and sand grains. Two semi-empirical equations are developed in this paper to connect GSD parameters with skeleton void ratio parameters. The validity of the proposed equations has been checked for a particular class of gravelly sand materials. A series of specially designed drained triaxial tests on gravelly sands were then conducted. Test results show that it is essential to consider the effect of GSD when using the skeleton void ratio index. It also verifies the effectiveness and applicability of the proposed updated skeleton void ratio, which shows advantages in characterizing critical state lines of gravelly sands.
Highlights
Sands, composed of gravel and sand grains, are commonly encountered in geotechnical engineering
At a low sand content sc, the mechanical behavior of gravelly sand is governed by intergranular friction between gravel grains
While at a high sc beyond a threshold valueth, the mechanical behavior of gravelly sand is primarily governed by friction characteristics of sand grains (Vallejo, 2001; Vasileva et al, 1971; Saberi et al, 2016; Ng et al, 2017; Gong et al, 2019; Ghorbani et al, 2020; Polito and Sibley, 2020; Yang et al, 2020a; Yang et al, 2020b)
Summary
Sands, composed of gravel and sand grains, are commonly encountered in geotechnical engineering. The effect of GSDs of gravel and sand grains is taken into account by conducting a series of vibrating compaction tests to build relationships between GSD and skeleton void ratio parameters, namely parameters a and b in Equations (5) and (6).
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