Cone penetration tests near the plastic limit

Use of fall cones to determine Atterberg limits: a review

“…Simply based on analysis of historical data, as the ratio of strengths at the PL and LL varies substantially between soils, these strength-based approaches can only coincidentally give correct PL values, actually measuring what might be termed the plastic strength limit (PL 100 ); that is the water content corresponding to s uFC ¼ 100 Â s uFC(LL) . Fall cone Belviso et al, 1985;Wasti, 1987;Harison, 1988;Feng, 2000Feng, , 2001Feng, , 2004Koumoto & Houlsby, 2001;Sharma & Bora, 2003;Lee & Freeman, 2009;Shimobe, 2010;Sivakumar et al, 2015), steady monotonic penetration (Stone & Phan, 1995;Stone & Kyambadde, 2007), fast-static loading (Sivakumar et al, 2009) and extrusion (Timár, 1974;Whyte, 1982;Medhat & Whyte, 1986;Kayabali & Tufenkci, 2010a, 2010bKayabali, 2011aKayabali, , 2011bKayabali, , 2012Kayabali et al, 2016) approaches for PL determination have all been suggested as alternatives to the standard thread-rolling approach. As mechanical tests, these strength-based approaches are seen by some researchers as means of achieving higher degrees of repeatability and reproducibility of results, although, to date, most fall-cone research has been conducted on well-behaved clay-rich soils that lie above the A-line on the standard plasticity chart.…”

“…the soil strength) is taken as the measurement of the plastic strength limit (e.g. Stone & Phan, 1995). Andrade et al (2011) present a review of some other approaches for the determination of soil plasticity, such as the 'Pfefferkorn', 'capillary rheometer' and 'torque rheometer' methods.…”

“…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).…”

“…w , PL) for water contents around PL 100 . This has implications for the preparation of the test specimens for fall-cone testing near the PL 100 Whyte, 1982;Wasti & Bezirci, 1986;Harison, 1988;Stone & Phan, 1995;Feng, 2000), in that for many cases sample preparation is difficult and some test specimens are likely not to be saturated, and calls into question the use of Hansbo's equation (1) for non-ductile materials. For PL 100 , PL, the strain-rate dependence and deformation mode of the soil test specimen will be significantly different for water contents between the PL 100 and the PL (i.e.…”

Some Recent Developments in the Determination of the Atterberg Limits

“…This problem has been addressed using pseudo-static cones that are mechanically driven into the soil (e.g. Stone & Phan, 1995).…”