Reply to discussion on ‘A correlation between friction angle and particle shape metrics in Quaternary coarse alluvia’ by Cheshomi et al .

Abstract

J. H. Atkinson has raised a number of relevant questions but it is important to note that the main message of our paper was to include specific geology to simplify the characterization of a soil, and the studied soil is a cohesive coarse and non-textbook material so its characterization is difficult because of difficulties in sampling and field testing in current practice. Based upon large-scale direct shear tests, the correlations presented relate particle shapes to friction angle for a specific local geological condition. In addition, Atkinson has presented eight paragraphs or subjects, which are addressed as follows. 1. In the second paragraph of the discussion, Atkinson classifies soil parameters and argues correctly that any empirical correlation between a state-dependent parameter such as peak friction angle and grain characteristics that does not consider stress and voids ratio must have very limited application. We believe that the application of the suggested correlations is relevant to Tehran A and C alluvia. Considering the specific geology of the studied alluvia, we have considered stress and voids ratio to propose empirical correlations between peak friction angle and grain characteristics. Our paper and the suggested correlations should be seen in the light of a previously published paper by Fakher et al . (2007). To present empirical correlations, geotechnical data have been added to a geological classification of alluvia. Accordingly, each alluvium and its empirical correlation are related to a similar geological condition. The proposed empirical correlations between peak friction angle and grain characteristics ‘implicitly’ include stress and voids ratio. There are four alluvia in the Tehran conurbation, but the suggested correlations are valid only for the A and C alluvia, which have similar geological conditions. We believe that the friction angle is influenced by the density (voids ratio), normal stress, …