Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D6031 – Standard Test Method Technical Guide
ASTM D6031/D6031M−24 is a standard test method for logging in situ moisture content and density of soil and rock using nuclear methods in horizontal, slanted, and vertical access tubes. This method involves the collection and comparison of thermalized-neutron counts and back-scattered gamma counts along air-filled tubes.
📐 Test Method Scope and Applicability
Section 1.1 specifies that this test method covers the collection and comparison of logs of thermalized-neutron counts and back-scattered gamma counts along horizontal, slanted, and vertical air-filled access tubes. The in situ water content and density in mass per unit volume are calculated at positions or intervals by comparing neutron and gamma count rates to calibration data (Section 1.3). Section 1.2 refers to limitations and interferences in Section 6 that must be considered.
| 🟦 Property | 📏 Measurement Method | 🎯 Typical Units |
|---|---|---|
| Water Content | Thermalized-neutron counts | kg/m³ or lb/ft³ |
| Density | Back-scattered gamma counts | kg/m³ or lb/ft³ |
⚙️ Calibration and Data Analysis
Calibration is essential. According to Section 1.3, water content and density are calculated by comparing thermal neutron and gamma count rates to previously established calibration data. Section 1.5 requires that all values conform to Practice D6026 for significant digits and rounding. Section 1.5.1 notes that data procedures are industry standards, but users should consider material variation and purpose for significant digits.
Tip: Use calibration data from representative materials to enhance accuracy. Regular calibration checks are recommended to maintain reliability.
📊 Key Measured Properties and Units
Section 1.4 specifies that values can be reported in SI units or inch-pound units, each used independently without combining values. Reporting in units other than SI is not nonconformance (Section 1.4.1). The measured properties are water content and density from neutron and gamma counts respectively.
| 📄 Standard Number | 📋 Description |
|---|---|
| D653 | Terminology for Soil, Rock, and Contained Fluids |
| D1452/D1452M | Practice for Soil Exploration by Auger Borings |
| D1586/D1586M | Test Method for Standard Penetration Test (SPT) |
| D2216 | Test Methods for Laboratory Water Content |
| D2937 | Test Method for Density by Drive-Cylinder |
Warning: Safety protocols for nuclear methods must be followed. See Section 8 for hazards and establish appropriate practices per Section 1.6.
❓ Frequently Asked Questions
🔍 What is the scope of ASTM D6031?
The scope is to log in situ moisture content and density of soil and rock via nuclear methods in access tubes, covering horizontal, slanted, and vertical orientations.
💡 How are moisture content and density determined?
Through thermalized-neutron counts for moisture content and back-scattered gamma counts for density, compared to calibration data.
⚡ Can units other than SI be used?
© 2026 TNLab — This article is a technical interpretation for reference only. The original standard as published by ASTM International takes precedence.