In 1975, ASTM Committee D18 on Soil and Rock published the first version of , titled Standard Test Method for Infiltration Rate of Soils in Field Using Double-Ring Infiltrometer . The method was deceptively simple: drive two concentric metal rings into the ground, fill both with water, and measure how fast the water level drops in the inner ring. The outer ring created a buffer zone so water flowed vertically from the inner ring, not horizontally. This gave a true infiltration rate—how fast rainwater, irrigation, or runoff enters the soil.
| Standard | Focus | Key Difference | |----------|-------|----------------| | | Field infiltration using single-ring infiltrometer | No outer ring; corrects for lateral flow mathematically. | | ASTM D5126 | Laboratory measurement of hydraulic conductivity (constant head) | Uses undisturbed soil cores. | | ASTM D3385 (older versions) | Same method but outdated references | No longer compliant with current specs. | | ISO 14388-2 | Double-ring infiltrometer (international version) | Different ring dimensions and reporting format. |
When these calculations are compiled, technicians plot the infiltration rate ( ) on the Y-axis against cumulative elapsed time ( ) on the X-axis. astm d338518 pdf
Tests made at the same site are not likely to give identical results, and the rate measured by this test method is primarily for comparative use.
) is calculated using the volume of water added to the inner ring, the surface area of the inner ring, and the time interval. In 1975, ASTM Committee D18 on Soil and
Acts as a buffer zone. The water infiltrating from the outer ring saturates the surrounding soil.
I=VA×Δtcap I equals the fraction with numerator cap V and denominator cap A cross delta t end-fraction This gave a true infiltration rate—how fast rainwater,
= Volume of water added to the inner ring during the interval ( cm3cm cubed = Cross-sectional area of the inner ring ( cm2cm squared Δtdelta t = Time interval duration (hours).
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One famous anecdote from the 1990s: a landfill liner design in Florida relied on lab permeability tests showing clay was nearly impermeable. But field tests using D3385 found infiltration rates 100 times higher—because natural cracks and wormholes existed. The design was changed, preventing a major groundwater contamination risk.
This test method is suitable for soils with hydraulic conductivity between approximately 1 × 10⁻⁵ cm/s and 10⁻² cm/s. For soils with hydraulic conductivity less than 1 × 10⁻⁵ cm/s, users should refer to Test Method D5093 (Field Measurement of Infiltration Rate Using a Double-Ring Infiltrometer with a Sealed-Inner Ring).