Status : Verified
| Personal Name | Valdez, Gideon L. |
|---|---|
| Resource Title | Interlaboratory Precision of Atterberg Limits: A Diagnostic Study of Soil Laboratories in the Philippines |
| Date Issued | 7 May 2026 |
| Abstract | Laboratories produce numbers, soils are classified, and engineering decisions follow. However, in routine geotechnical practice, the reliability of Atterberg limit results is often assumed once ASTM D4318 is followed. This study tests that assumption by examining whether soil plasticity influences the precision expected from routine liquid limit and plastic limit testing. An interlaboratory program was conducted among established and ISO-certified geotechnical laboratories, using a base soil blended with 0%, 15%, 30%, 45%, and 60% bentonite to create a controlled shift from low to high plasticity. Variability was evaluated using ASTM E691 measures of within- and between-laboratory variations. At low plasticity, LL values remained grouped from 40 to 45. At 60% bentonite, LL spread from 98 to 129, giving a range of 31, while PL reached a lower range of 14. Between-laboratory standard deviation increased from 1.54 to 10.46 for LL and from 1.25 to 5.34 for PL, showing that LL was more sensitive to plasticity-related variation. Despite this loss of precision, LL flow curves produced high r2 values of 0.96–1.00, showing that strong regression fit does not necessarily imply good precision. The divergence is interpreted as reflecting soil state differences established before testing through drying, curing, and mixing. Low plasticity can make laboratories appear aligned. High plasticity reveals how differently the laboratories following the same standard can behave. |
| Degree Course | MS Civil Engineering (Geotechnical) |
| Language | English |
| Keyword | Atterberg limit; liquid limit; plastic limit; interlaboratory; precision; soil plasticity; bentonite |
| Material Type | Thesis/Dissertation |
Preliminary Pages
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Category : F - Regular work, i.e., it has no patentable invention or creation, the author does not wish for personal publication, there is no confidential information.
Access Permission : Open Access