Discussion of ‘Factors influencing undrained strength of fine-grained soils at high water contents’ [Geomechanics and Geoengineering 13(4), 276–287]

It is the authors’ opinion that confusion could arise from the analyses and explanations of the experimental fall-cone (FC) results presented in the paper by Nagaraj et al. (2018), which has been compounded in their recent Closure (Nagaraj et al. 2021) to the Discussion of their 2018 paper by Haigh et al. (2021). For the investigation by Nagaraj et al. (2018), the FC method, as per the British Standards Institution (BSI) BS 1377–2 (1990), was used to determine the liquid limit (i.e. wL-FC(BSI)), which defines the liquid-limit state transition as the water content corresponding to a penetration depth of hL = 20 mm for a smooth, polished 30°–80 g FC with its tip initially just contacting the top surface of the fine-grained soil test specimen. The FC test was originally developed for measuring undrained shear strength (Hansbo 1957, O’Kelly et al. 2018) and was subsequently adopted for determination of the FC liquid limit (e.g. BSI 1975), with the FC-deduced saturated remoulded undrained shear strength (i.e. cu(FC)) of a finegrained soil tested at a given water content determined as follows: