Reappraisal of the ASTM/AASHTO Standard Rolling Device Method for Plastic Limit Determination of Fine-Grained Soils

Abstract

Given its apparent limitations, various attempts have been made to develop alternative testing approaches to the standardized rolling-thread plastic limit (PLRT) method (for fine-grained soils), targeting higher degrees of repeatability and reproducibility. Among these, device-rolling techniques, including the method described in ASTM D4318/AASHTO T90 standards, based on original work by Bobrowski and Griekspoor (BG) and which follows the same basic principles as the standard thread-rolling (by hand) test, have been highly underrated by some researchers. To better understand the true potentials and/or limitations of the BG method for soil plasticity determination (i.e., PLBG), this paper presents a critical reappraisal of the PLRT–PLBG relationship using a comprehensive statistical analysis performed on a large and diverse database of 60 PLRT–PLBG test pairs. It is demonstrated that for a given fine-grained soil, the BG and RT methods produce essentially similar PL values. The 95% lower and upper (water content) statistical agreement limits between PLBG and PLRT were, respectively, obtained as −5.03% and +4.51%, and both deemed “statistically insignificant” when compared to the inductively-defined reference limit of ±8% (i.e., the highest possible difference in PLRT based on its repeatability, as reported in the literature). Furthermore, the likelihoods of PLBG underestimating and overestimating PLRT were 50% and 40%, respectively; debunking the notion presented by some researchers that the BG method generally tends to greatly underestimate PLRT. It is also shown that the degree of underestimation/overestimation does not systematically change with changes in basic soil properties; suggesting that the differences between PLBG and PLRT are most likely random in nature. Compared to PLRT, the likelihood of achieving consistent soil classifications employing PLBG (along with the liquid limit) was shown to be 98%, with the identified discrepancies being cases that plot relatively close to the A-Line. As such, PLBG can be used with confidence for soil classification purposes.

Prediction of California Bearing Ratio of Granular Soil by Multivariate Regression and Gene Expression Programming

“…e majority of the samples depicted fall above line A and below line U. e existence of soil samples parallel to the line A on the plasticity chart shows that they have the same geological origin [19,30]. Table 3 provides a full statistical summary of the soil.…”

Predicting the Compactability of Artificially Cemented Fine-Grained Soils Blended with Waste-Tire-Derived Aggregates

“…To ensure that the OWC and MDD predictions are indeed reliable for routine soil-binder-TDA mixture-design applications, the lower and upper "statistical limits of agreement" between the predicted and measured values should also be quantified and critically examined (Soltani et al 2021b). A common approach in this context includes the use of the Bland-Altman (BA) plotting technique (Rehman et al 2020;Soltani and O'Kelly 2021)-that is, an x:y scatter plot; the x-axis showing the mean of the ( 10) predicted and corresponding measured variables (i.e., M PM = [OWC P + OWC M ]/2 or [MDD P + MDD M ]/2, with the subscripts "P" and "M" representing predicted and measured cases, respectively) and the y-axis representing the difference between the same variables (i.e., D PM = [OWC P − OWC M ] or [MDD P − MDD M ]). The 95% lower and upper statistical limits of agreement, with respect to the BA plot, can be obtained as follows (Bland and Altman 1999):…”

Discussion of “Physio-Chemical Properties, Consolidation, and Stabilization of Tropical Peat Soil Using Traditional Soil Additives — A State of the Art Literature Review” by Afnan Ahmada, Muslich Hartadi Sutantoa, Mohammed Ali Mohammed Al-Bareda, Indra Sati Hamonangan Harahapa, Seyed Vahid Alavi Nezhad Khalil Abada, Mudassir Ali Khana

“…As described above and also stated in O' Kelly et al (2018), "greater mechanical breakdown of the peat solids during sample preparation produces lower LL, PL and PI values, especially for less humified material (O'Kelly, 2015a), such that the measured plastic ranges are arbitrary and unlikely to sensibly correlate with mechanical behavior (Hobbs, 1986;O'Kelly and Zhang, 2013;O'Kelly, 2015a, 2016)" (p. 847 of O'Kelly et al (2018). For updated state-of-the-art literature reviews of consistency limits determinations (of mineral finegrained soils), the reader is referred to the papers by O'Kelly (2021), Soltani andO'Kelly (2021) andO'Kelly et al (2022).…”