ISO 17892-12:2018

Overview

ISO 17892-12:2018 - Geotechnical investigation and testing - Laboratory testing of soil - Part 12: Determination of liquid and plastic limits - specifies internationally accepted laboratory methods for determining two fundamental Atterberg limits: the liquid limit (LL) and the plastic limit (PL). The liquid limit is the water content at which soil passes from a liquid to a plastic state; the plastic limit is the water content at which a specimen ceases to be plastic on further drying. The standard details test procedures, apparatus, calibration and reporting so results are reproducible and suitable for soil classification and engineering design.

Key topics and technical requirements

• Test methods covered: two alternative procedures for LL - the fall cone method and the Casagrande method - plus the standard procedure for PL determination. (Note: the fall cone method here is distinct from the fall cone method in ISO 17892‑6.)
• Apparatus and tolerances: specifications for equipment such as balances (accuracy 0.01 g or 0.1 %), fall cones (typical cones: 60 g/60° or 80 g/30° with defined tip wear limits), specimen cups, Casagrande bowl and cam, grooving tool, timing devices and measurement resolution (penetration measured to 0.1 mm or better).
• Procedure steps: specimen preparation, choice of LL method, stepwise testing (including required ranges of penetration or number of blows), and PL rolling tests. The document recognises operator judgement and inherent variability in results.
• Calibration and checks: Annex A provides requirements for calibration, maintenance and periodic checks of apparatus.
• Reporting: mandatory and optional items (e.g., proportion of sample <0.4 mm, LL by chosen method, PL, and computed plasticity index (PI = LL − PL)) to ensure clarity and traceability.

Practical applications

• Soil classification and index testing for geotechnical design (foundations, embankments, earthworks).
• Input parameters for settlement, consolidation and slope stability assessments.
• Quality control in earthworks, site investigation labs and pre-construction testing.
• Research and verification when comparing laboratory methods (fall cone vs Casagrande).

Who should use this standard

• Geotechnical engineers and engineering geologists
• Soil-testing laboratories and technicians
• Construction and civil engineering firms performing site investigations
• Regulatory bodies, consultants and researchers requiring standardized soil index data

Related standards

• ISO 17892 series (other laboratory soil tests)
• ISO 17892‑1 (determination of water content)
• ISO 17892‑6 (other fall cone procedures - distinct)
• ISO 3310‑1 (test sieves)

Keywords: ISO 17892-12:2018, liquid limit, plastic limit, Atterberg limits, fall cone method, Casagrande method, geotechnical testing, soil plasticity, laboratory testing of soil, plasticity index.