Measuring how fast water enters the ground is critical for civil engineering, environmental science, and agricultural planning. The standard protocol for this measurement is .
The test continues until the infiltration rate becomes constant. Initially, dry soil will absorb water rapidly due to matric suction. As the soil becomes saturated, the rate decreases and levels off, approaching the saturated hydraulic conductivity ( Ksatcap K sub s a t end-sub ) of the soil. Calculations and Data Interpretation The infiltration rate (
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ASTM D3385-18 references several other ASTM standards that may be used in conjunction with it for comprehensive soil testing and site characterization: astm d338518 pdf
The test may be conducted at the ground surface or at given depths in pits, and on bare soil or with vegetation in place, depending on the conditions for which infiltration rates are desired. However, the test cannot be conducted where the test surface is below the groundwater table or perched water table.
: This method measures infiltration rate , which cannot be used as a direct substitute for the laboratory-defined saturated hydraulic conductivity (permeability coefficient) of the soil. 3. The Double-Ring Mechanism Explained
The test area must be cleared of debris, excessive vegetation, and loose topsoil. The surface should be as level as possible. Avoid disturbing the natural structure of the soil during preparation, as compaction will skew the results. 2. Driving the Rings Center the inner ring inside the outer ring. Measuring how fast water enters the ground is
: Only the volume of water added to the inner ring is used to calculate the infiltration rate. The outer ring acts as a buffer to ensure water from the inner ring flows vertically into the soil, preventing lateral spread.
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.
The standard explicitly states that it does not purport to address all safety concerns associated with its use. It is the responsibility of the user to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Users should be aware of potential hazards associated with handling water and equipment in field settings, as well as environmental considerations when conducting tests. Initially, dry soil will absorb water rapidly due
The outer ring creates a buffer of saturated soil, forcing the water from the inner ring to flow rather than spreading out laterally. This promotes the "one-dimensional, vertical flow" crucial for isolating the infiltration rate of the soil itself. By maintaining a constant water level and measuring the volume of water needed to do so, you get a direct measure of the infiltration rate.
ASTM D3385-18 is the active standard test method for measuring the infiltration rate of soils in the field using a double-ring infiltrometer. It is utilized in geotechnical engineering to assess water penetration using constant, measured flow in two concentric rings, making it best suited for uniform soils with specific hydraulic conductivity. Purchase the official document at ASTM International ASTM International
The 2018 revision (D3385-18) clarified procedures for different soil types, added guidance on test duration, and emphasized the importance of maintaining constant head (water depth) during the test. It also addressed common errors: ring-driving disturbance, evaporation, and temperature effects.
Estimating seepage from canals, reservoirs, or retention ponds. 3. The Double-Ring Infiltrometer Apparatus
The movement of water through the soil surface, known as infiltration, is a fundamental hydrologic process. It governs the partitioning of rainfall into surface runoff and subsurface storage, influencing everything from flood forecasting and irrigation efficiency to the design of stormwater management systems and landfill liners. Accurate quantification of the infiltration rate is essential for civil engineers, hydrologists, and environmental scientists.