Discussion: Index and strength properties of clay–gravel mixtures

Discussion: Measuring the plastic limit of fine soils: an experimental study

“…Vardanega and Haigh (2014) have pointed out that the systematic bias in water content at the thread-rolling PL arising due to operator sensitivity can have a significant effect on the calculation of the liquidity index, particularly for soils having low plasticity index close to the PL. This bias associated with the thread-rolling PL could be argued as another reason for favouring the PL 100 when dealing with strength and stiffness correlations, as reported by Haigh et al (2013) and Kyambadde et al (2014). In conclusion, the authors thank the discusser for the opportunity to further elaborate on these fundamental points to their energy-based fall cone set-up for the determination of the plastic strength limit PL 100 .…”

“…The PL 100 has been defined and described in many publications as the water content corresponding to a 100-fold increase in the liquid limit (LL) undrained strength (see Haigh et al (2013), Kyambadde and Stone (2012), Kyambadde et al (2014), O'Kelly (2013), Stone and Kyambadde (2007), Stone and Phan (1995), to name a few). In the authors' study, the liquid limit was determined using the British Standard method (BSI, 1990), with this standard fall-cone liquid limit (LL FC ) corresponding to a (dynamic) undrained strength of 2·66 kPa (Koumoto and Houlsby, 2001).…”

“…However, as described by Haigh et al (2013) and Kyambadde et al (2014), for correlations with strength and stiffness, the PL 100 or the plasticity index PI 100 (Equation 4) would be the favourable choice since they are implicitly linked to the strength variation with water content.…”

Use of fall cones to determine Atterberg limits: a review

“…Having recognised the important distinction between the true PL and that measured by strength-based tests, the 'PL' determined by the fall-cone approach has been referred to as the 'plastic strength limit' (Haigh et al, 2013) PL 100 (Harison, 1988;Stone & Phan, 1995;Stone & Kyambadde, 2007;Kyambadde & Stone, 2012;Haigh et al, 2013;O'Kelly, 2013;Kyambadde et al, 2014;Sivakumar et al, 2015Sivakumar et al, , 2016, with the subscript 100 indicating that the defined strength is 100 times the strength mobilised for the fall-cone LL (s uFC(LL) ). This assumes that cones having identical apex angle and surface roughness values are used in identifying both LL FC and PL 100 , and, furthermore, that the strain-rate dependency of the soil remains the same (as considered in the next section).…”

Editorial

“…The first continues the theme of adding granular materials to clay but with a focus on the index and strength properties of clay-gravel mixtures (Kyambadde et al, 2014). The final discussion returns to the theme of piles and, in this case the various code approaches to design originally presented by Vardanega et al (2014) with comparison being made between approaches used in the USA and those outlined in Eurocode 7.…”