The ASTM D3385-18 standard provides a rigorous procedure for measuring the infiltration rate of soils in the field using a double-ring infiltrometer. This method is essential for civil engineers, hydrologists, and environmental scientists to determine how quickly water penetrates a site's soil—a critical factor for designing drainage systems, septic fields, and irrigation networks. Overview of ASTM D3385-18

This standard, officially titled "Standard Test Method for Infiltration Rate of Soils in Field Using Double-Ring Infiltrometer," defines the equipment and methodology required to obtain reliable field data.

Primary Goal: To measure the rate at which a liquid (typically water) enters the soil surface.

Apparatus: Two concentric rings—usually a 12-inch (300 mm) inner ring and a 24-inch (600 mm) outer ring—driven into the soil to a specific depth.

Key Application: Used for evaluating liquid waste disposal sites, septic-tank fields, irrigation requirements, and potential leakage in canals or reservoirs. Scope and Soil Applicability

The ASTM D3385-18 method is highly specialized and not suitable for all soil conditions:

Ideal Soils: Most effective for relatively uniform, fine-grained soils with moderate to low resistance to penetration.

Limitations: It may produce unreliable results in very pervious soils (hydraulic conductivity >10-2is greater than 10 to the negative 2 power cm/s) or very impervious soils ( <10-5is less than 10 to the negative 5 power

Restrictions: This test cannot be performed if the soil surface is below the groundwater table. For extremely low infiltration rates, experts often refer to ASTM D5093 (sealed inner ring method) instead. The Double-Ring Method: How It Works

The "double-ring" design is critical for accuracy because it forces water in the inner ring to flow one-dimensionally (vertically). The outer ring acts as a buffer, saturating the surrounding soil to prevent lateral (sideways) spreading from the inner measurement area. Requirement under ASTM D3385-18 Method Constant Head Method (water level is kept steady) Ring Depth Driven typically to 150 mm (6 inches) Measurement

Volume of water added to the inner ring over timed intervals Result Unit

Typically expressed in centimeters per hour (cm/h) or inches per hour Practical Procedure Steps

The ASTM D3385-18 standard provides the field procedure for measuring the infiltration rate of soils using a double-ring infiltrometer. This method is primarily used for fine-grained soils to assess drainage for irrigation, waste disposal, or reservoir leakage. Core Test Principles

The test uses two concentric open cylinders (rings) driven into the soil. The outer ring limits lateral water spread, ensuring that water from the inner ring moves vertically downward, which provides a more accurate measure of one-dimensional infiltration.

Infiltration Rate: The volume of liquid added to the inner ring to maintain a constant water level over time.

Incremental Infiltration Velocity: The quantity of flow per unit area over a specific time increment, typically measured in cm/h or in/hr. Key Specifications and Limitations

Title: A Comprehensive Technical Analysis of ASTM D3385-18: Standard Test Method for Infiltration Rate of Soils in Field Using Double-Ring Infiltrometers

Abstract

This paper provides an in-depth examination of ASTM D3385-18, the standard test method designated for determining the infiltration rate of soils in the field using a double-ring infiltrometer. As water infiltration is a critical parameter in geotechnical engineering, hydrology, agriculture, and environmental remediation, the accuracy of field data is paramount. This document explores the theoretical underpinnings of the double-ring method, details the apparatus and procedural requirements set forth by the ASTM standard, discusses the calculation of infiltration rates, and analyzes the sources of error and limitations inherent in the methodology. Furthermore, this paper addresses the significance of the 2018 revision in the context of modern engineering practices and compares the method with alternative infiltration measurement techniques.

Procedure (Abbreviated):

1. Site Selection – Representative area, avoiding cracks, macropores, or surface crusting unless intentional.
2. Ring Installation – Drive rings concentrically into soil to a depth of 5–10 cm, ensuring vertical alignment and minimal soil disturbance.
3. Surface Preparation – Trim soil level with ring tops, remove loose debris, and if needed, place a thin layer of gravel to prevent erosion from falling water.
4. Water Application – Fill both rings to a constant head (typically 5–10 cm). Maintain the same water level in both rings.
5. Measurement – Record water level drop in the inner ring at regular intervals (e.g., every 1, 2, 5, 10 minutes depending on soil type).
6. Continue until the infiltration rate becomes constant for at least 3–5 consecutive readings.
7. Calculate – Infiltration rate (I) = Δh / Δt, where Δh is change in water height and Δt is time interval.

1. Introduction

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.

ASTM D3385-18, officially titled “Standard Test Method for Infiltration Rate of Soils in Field Using Double-Ring Infiltrometers,” serves as the industry benchmark for this measurement. By utilizing a concentric ring apparatus, the method aims to minimize lateral flow divergence, thereby providing a more accurate representation of the vertical hydraulic conductivity of the soil. This paper dissects the standard, offering guidance on its practical application and theoretical basis.

Key Features of ASTM D3385-18

1. Scope: This standard covers the determination of the pore size distribution of geotextiles, which can be used to evaluate their filtration and permeability characteristics.

2. Referenced Documents: The standard references several other ASTM standards and documents, including those on geotextile sampling and conditioning.

3. Terminology: It provides definitions relevant to the standard, including terms like "apparent opening size" and "pore size distribution."

4. Significance and Use: The standard discusses the importance of pore size distribution in geotextile applications and how it influences the selection of geotextiles for specific projects.

5. Apparatus: Detailed descriptions of the equipment needed for the test are provided, including sieves, a mechanical sieve shaker, and balances.

6. Procedure: The testing procedure involves dry sieving of geotextile samples with soils of known gradation. The percentage of soil passing through the geotextile is related to the pore size distribution.

7. Calculation and Reporting: Results are calculated based on the amount of soil passing through the geotextile and are typically presented as a plot of percent passing versus particle size.

References

• ASTM D3385-18. (2018). Standard Test Method for Pore Size Distribution of Geotextiles by Dry Sieving. ASTM International.

By understanding and adhering to standards like ASTM D3385-18, professionals in the construction, civil engineering, and geosynthetics industries can ensure that geotextile materials perform as expected, thereby enhancing the safety, durability, and sustainability of infrastructure projects. Whether you're an engineer, a procurement specialist, or a researcher in the field, staying informed about ASTM standards and their implications can significantly impact the success of your projects.