ISO 11275:2004 PDF

Overview

ISO 11275:2004 specifies a laboratory procedure - Wind's evaporation method - for the simultaneous determination of the unsaturated hydraulic conductivity and the soil water‑retention characteristic during drying (desorption). The method is designed for relatively homogeneous, undisturbed soil samples and is limited to the drying curve (not wetting). Results characterize how soil water content and matric head relate and how conductivity changes as soils dry.

Key topics and technical requirements

• Scope & limits
  • Applicable only to the drying (desorption) curve and to samples that remain non‑shrinking in the range h = 0 cm to −800 cm.
  • Conductivity determination typically spans matric heads of about −50 cm to −700 cm; water‑retention between 0 cm and −800 cm.
  • Assumes one‑dimensional flow and homogeneous hydraulic properties.
• Principle
  • Samples are wetted to near saturation, then allowed to dry from the top.
  • Tensiometers installed at different depths measure matric (pressure) head over time while the sample mass is recorded.
  • The sample is treated as compartments (one per tensiometer); water‑retention and unsaturated conductivity are derived using Wind’s evaporation analysis.
• Apparatus & test setup
  • Undisturbed sampling sleeves/rings (sample height ≤ diameter; recommended example 8 cm height × 10 cm diameter for stone‑free soils).
  • Polyamide mesh, container for controlled wetting, balance (accuracy ±0.1 %), tensiometer system (per ISO 11276), drying oven at 105 ± 2 °C.
  • Tensiometer dimensions: length