ASTM D6431-18 PDF

Full title and description

ASTM D6431-18 — Standard Guide for Using the Direct Current Resistivity Method for Subsurface Site Characterization. This guide summarizes equipment, field procedures, array configurations, data acquisition (sounding and profiling), and interpretation approaches used to assess the electrical properties of subsurface materials and pore fluids using direct‑current (DC) resistivity measurements from the surface (land or water).

Abstract

D6431-18 provides a practical overview of the DC resistivity method for geophysical site characterization. It explains common electrode arrays (Wenner, Schlumberger, dipole‑dipole), basic formulae for apparent resistivity, typical field layouts for soundings and profiles, data quality considerations, and general guidance on interpretation (including the need for inversion and use of complementary data). The guide is intended as an organized reference of commonly used, widely accepted approaches rather than a detailed textbook on theory or all specialized variants of resistivity techniques.

General information

• Status: Superseded / withdrawn — replaced by ASTM D6431-25 (newer edition published 2025).
• Publication date: February 1, 2018.
• Publisher: ASTM International (formerly American Society for Testing and Materials).
• ICS / categories: 07.060 — Geology. Meteorology. Hydrology (surface and subsurface geophysical investigation).
• Edition / version: D6431-18 (2018 edition).
• Number of pages: 14 pages.

Scope

The guide covers use of the DC resistivity technique to measure apparent resistivity from the surface (land or water) and to interpret those measurements to estimate depth, thickness, and resistivity of subsurface layers. It focuses on commonly used electrode arrays and field methods (sounding and profiling), discusses data acquisition best practices and limitations, and provides guidance on when inversion and complementary data are needed for reliable geological and hydrologic interpretations. It does not exhaustively cover specialized arrays, induced‑polarization, or complex resistivity methods.

Key topics and requirements

• Overview of DC resistivity principles and definitions (resistance, resistivity, apparent resistivity).
• Recommended electrode arrays and comparative strengths: Schlumberger, Wenner, dipole‑dipole (and discussion of other arrays and multielectrode systems).
• Field procedures for soundings (depth measurements) and profiling (lateral mapping), including recommended electrode spacing strategies and data‑point density.
• Formulas for computing apparent resistivity for common array geometries and notes on contact resistance and noise control.
• Data quality, plotting (log‑log sounding curves), and the role of inversion (including modern ERT/ERI approaches in later editions).
• Limitations, recommended complementary data (boreholes, logs, other geophysical methods), and safety/precautionary notes when using equipment with high currents/voltages.

Typical use and users

Used by geophysicists, geotechnical and civil engineers, hydrogeologists, environmental consultants, and site‑investigation professionals for mapping subsurface features such as lithology changes, fractures, voids, depth to water table or aquitard, and distribution of groundwater salinity or contaminants. Typical applications include site characterization for construction, environmental assessment, groundwater investigations, and preliminary mapping prior to drilling.

Related standards

Commonly cross‑referenced ASTM documents and related practices include Guide D420, Practice D5088, Practice D5608, Guide D5730, Test Method G57, D6429, and D6235. Later editions (D6431-25) expand guidance to include electrical resistivity tomography (ERT) and multielectrode systems; users should consult the current D6431 edition for the most up‑to‑date recommendations.

Keywords

DC resistivity, apparent resistivity, electrical resistivity tomography (ERT), Wenner array, Schlumberger array, dipole‑dipole array, soundings, profiling, subsurface characterization, geophysical site investigation, hydrogeophysics.

FAQ

Q: What is this standard?

A: ASTM D6431-18 is a guide describing the direct current (DC) resistivity method for subsurface site characterization — equipment, common arrays, field procedures, data presentation, and interpretation guidance.

Q: What does it cover?

A: It covers measurement of apparent resistivity from the surface (land or water), recommended electrode arrays (Wenner, Schlumberger, dipole‑dipole), sounding and profiling methods, basic equations for apparent resistivity, data‑quality considerations, and interpretation practices (including the need for inversion and complementary data).

Q: Who typically uses it?

A: Geophysicists, geotechnical/hydrogeologic engineers, environmental consultants, and site investigation teams performing noninvasive subsurface surveys for mapping stratigraphy, water table, voids, contaminants, and similar targets.

Q: Is it current or superseded?

A: D6431-18 was published February 1, 2018; it has been superseded by a later edition, ASTM D6431-25 (published in 2025). For current requirements and expanded material (for example, broader coverage of multielectrode ERT workflows), consult ASTM D6431-25 (the active edition as of 2025).

Q: Is it part of a series?

A: Yes — it is one in a series of ASTM guides and practices for geophysical site investigation methods and is produced under Committee D18 (Subcommittee D18.01). The guide references and complements other ASTM practices and guides for site investigation and geophysical testing.

Q: What are the key keywords?

A: DC resistivity, apparent resistivity, ERT, Wenner, Schlumberger, dipole‑dipole, sounding, profiling, subsurface, geophysics, hydrogeology.