Use of fall cones to determine Atterberg limits: a review

Abstract

This paper reviews the percussion-cup liquid limit, thread-rolling plastic limit (PL) and various fall-cone and other approaches employed for consistency limit determinations on fine-grained soil, highlighting their use and misuse for soil classification purposes and in existing correlations. As the PL does not correspond to a unique value of remoulded undrained shear strength, there is no scientific reason why PL measurements obtained using the thread-rolling and shear-strength-based fall-cone or extrusion methods should coincide. Various correlations are established relating liquid limit values deduced using the percussion-cup and fall-cone approaches. The significance of differences in the strain-rate dependency on the mobilised fall-cone shear strength is reviewed. The paper concludes with recommendations on the standardisation of international codes and the wider use of the fall-cone approach for soft to medium-stiff clays in establishing the strength variability with changing water content and further index parameters.

Closure to “Reclaimed Lignin-Stabilized Silty Soil: Undrained Shear Strength, Atterberg Limits, and Microstructure Characteristics” by Tao Zhang, Guojun Cai, and Songyu Liu

“…The fall cone method was employed to determine the Atterberg limits and undrained shear strength of lignin-stabilized silty soil with 7 days of curing. The writers fully agree that the standard liquid and plastic limit values of the natural soils should be determined in the remolded state, as specified in the various testing standards and in previous research (O'Kelly et al 2018). However, the target soil tested in this study is not a natural soil but a chemically stabilized soil (lignin-stabilized silty soil) that is probably out of the scope of the testing standards.…”

“…It is noteworthy that all parameter values of the writers' Eqs. (1) and (2) reported by Feng (2000) and O'Kelly et al (2018) were derived from the regression results for natural soils. The applicability of these suggested values to lignin-stabilized silty soil is still unknown.…”

Geotechnical laboratory testing and data interpretation for biosolids and sewage sludge

“…As explained in the papers by O'Kelly (2018c) and O'Kelly et al (2018b), the appropriate value of K for use in Equation 3 (and, hence, the calculated undrained strength value) decreases with increasing strain rate dependence. The practical significance for FC testing of biosolid and sewage sludge materials is demonstrated with reference to a particular example considering the 30°-400 g fall cone.…”

“…obtained from VS, unconfined compression or UU TC tests) in order to establish an appropriate experimental K value for use in Equation 3 (O'Kelly, 2016a). Alternatively, as explained in the papers by O'Kelly (2018c) and O'Kelly et al (2018b), for a given cone apex angle and with knowledge of the cone surface roughness properties and also the m value of the test material, an appropriate K value can be calculated from theory and making use of the numerical analysis results presented by Hazell (2008). To overcome the uncertainties regarding the test material's strain rate dependence, a different approach is to use pseudo-static cones that are mechanically pushed into the soil test specimen to measure the static undrained strength directly (e.g.…”

“…Recommendations on the placement and compaction of the biosolid material in a monofill facility, along with guidance on the selection of design strength values for geotechnical stability analyses and in performing settlement calculations, are presented by O'Kelly (2004aO'Kelly ( , 2005b, with a biosolid-monofill case study presented by O'Kelly et al (2018b).…”