ASTM D3385 Standard Test Method for Infiltration Rate of Soils in Field Using Double-Ring Infiltrometer

Get Certified ASTM D3385 Testing for Soils

Professional ASTM D3385 testing provides field data that engineers can use to characterize the soil’s infiltration behavior under the conditions simulated by the test. Qualified personnel can set the test site and level, install the double-ring infiltrometer, manipulate the liquid added, observe the infiltration, and record the conditions affecting the infiltration rate. Accurate field testing also helps users compare infiltration behavior between locations or evaluate changes at a site. ASTM emphasizes that soil structure, layering, surface condition, saturation, liquid properties, liquid head, temperature, and ring dimensions and embedment can influence the measured rate.

• Material Type: Natural soils, processed materials, mixtures of natural and processed soils, and other basically insoluble porous materials within the method’s applicability.
• Property Measured: Field infiltration rate of liquid into soil.
• Test Method: Double-ring infiltrometer with concentric inner and outer rings.
• Flow Control: The outer ring promotes predominantly vertical flow beneath the inner ring.
• Test Location: Ground surface or selected soil depths in pits.
• Applicable Soil: Particularly suitable for relatively uniform fine-grained soils with moderate to low ring-penetration resistance.
• Limitations: The method can become difficult or produce unreliable data in very pervious or very impervious soils, and dry or stiff soils can fracture during installation.
• Groundwater Condition: The test surface cannot lie below the groundwater table or a perched water table.
• Hydraulic Conductivity: The method does not directly determine hydraulic conductivity.
• Units: SI units serve as the standard; inch-pound values provide mathematical conversions.

What are the Uses of ASTM D3385 testing?

ASTM D3385 testing helps engineers characterize how readily water or another suitable liquid enters soil under field conditions. The resulting infiltration data can support soil and water-management investigations and comparisons between different field locations. ASTM identifies applications including liquid waste disposal, septic-tank disposal field evaluation, leaching and drainage studies, irrigation requirements, water spreading and recharge, and canal or reservoir leakage investigations. The uses cover:

• Infiltration Assessment: Determine soil infiltration behavior in the field.
• Septic-System Evaluation: Support evaluation of potential soil conditions for septic-tank disposal fields.
• Drainage Studies: Evaluate infiltration and drainage efficiency.
• Irrigation Planning: Provide field infiltration information for irrigation studies.
• Recharge Studies: Support water-spreading and groundwater-recharge investigations.
• Wastewater Studies: Provide infiltration information for selected liquid-waste disposal investigations.
• Leakage Investigations: Support studies involving canal or reservoir leakage.
• Comparative Site Evaluation: Compare infiltration rates between selected soil locations.

Which Materials Can Be Tested According to ASTM D3385?

ASTM D3385 applies to soils and other porous materials that meet the method’s applicability requirements. The method suits relatively uniform fine-grained soils but becomes less suitable when excessive gravel, very plastic clay, extremely high or low permeability, or soil fracturing interfere with ring installation and infiltration measurement. The material testing includes:

• Natural Soils: Naturally occurring soil deposits.
• Processed Soils: Processed soil materials used in engineering applications.
• Soil Mixtures: Mixtures of natural and processed soil materials.
• Porous Materials: Other basically insoluble porous materials that meet the scope requirements.
• Fine-Grained Soils: Relatively uniform fine-grained soils represent a principal application.
• Soils with Vegetation: Testing can occur with vegetation in place when the investigation requires those conditions.
• Dry or Stiff Soils: Testing requires caution because installation can fracture these materials.
• Very Permeable or Impermeable Soils: The method may produce unreliable results outside its stated applicability range.

Why is ASTM D3385 Testing Important?

Soil infiltration determines how quickly water percolates into the soil, which in turn influences drainage, irrigation, recharge, and disposal rates, as well as water management decisions. ASTM D3385 establishes a standard field method that enables technicians to measure infiltration under controlled testing conditions, and not just laboratory assumptions or by sight. The double-ring arrangement also helps reduce the influence of lateral flow beneath the inner measurement area because the outer ring encourages more nearly vertical flow. However, ASTM emphasizes that infiltration rates vary with soil and test conditions, so users should interpret results in relation to the actual field conditions and purpose of the investigation.

ASTM D3385 Testing Process and Data Collection

The technician first establishes the soil profile and selects a suitable test location. The test surface should provide sufficient room for the equipment, remain sufficiently level, and represent the soil zone being investigated. The technician then positions the concentric rings and drives them into the soil or installs them in prepared trenches where driving would damage dry or stiff soil. The technician checks the rings for proper vertical alignment and minimizes disturbance around the ring walls. After installation, the technician introduces water or another appropriate liquid into the inner and outer rings. The technician records the ring dimensions, test location, soil conditions, liquid temperature, relevant water levels or heads, elapsed time, and liquid volume added. The analyst then uses the measured infiltration increments and the effective inner-ring area to calculate the infiltration rate for the selected intervals and evaluate whether the rate approaches a quasi-steady condition.

Common Challenges and Troubleshooting

One main challenge is installing the rings without disturbing the soil. Excessive driving, tilting, or fracturing can create preferential flow paths and produce unrepresentative infiltration measurements. Technicians should select suitable installation methods and maintain the rings in a vertical, stable position. Technicians should also avoid applying D3385 outside its intended range. The method can become difficult or unreliable in soils with very high or very low hydraulic conductivity and in dry or stiff soils that fracture during ring installation. ASTM identifies D5093 as a reference method for soils with hydraulic conductivity below approximately 1 1×10-5cm/s.

• The infiltration rate can decrease as the test progresses until the soil approaches quasi-steady infiltration. Use calculated rates with the test duration and field conditions, and do not assume they represent the entire site. ASTM cautions that variables like soil structure, layering, saturation, surface condition, liquid temperature, liquid head, and ring dimensions all affect the rate measured.
• The standard uses SI units. Infiltration rate can be reported as a length per unit time, such as mm/h, depending on the calculation and reporting format used by the project. Technicians should also retain the underlying time and liquid-volume measurements so analysts can verify the calculated rate.
• The final report is to include the test site, soil conditions, ring dimensions, ring areas, installation conditions, liquid used, liquid temperature (if applicable), measurement intervals, calculated infiltration rates, and pertinent observations. The infiltration reported by ASTM D3385 is not a true hydraulic-conductivity value but rather a volume of air that has intruded into the soil.
• ASTM D3385 results are more comparable and reliable when the site, ring installation, the measurement, the calibration of the equipment, the data, and the field control is performed in a consistent way.

Link to ASTM D3385