Standard Guide for Using the Direct Current Resistivity Method for Geophysical Site Investigation

Importancia y uso:

5.1 Concepts—The resistivity technique is used to measure the resistivity of subsurface materials. Although the resistivity of materials can be a good indicator of the type of subsurface material present, it is not a unique indicator. While the resistivity method is used to measure the resistivity of earth materials, it is the interpreter who, based on knowledge of local soils, geologic conditions, and other data, must interpret resistivity data and arrive at a reasonable soils, geologic, and hydrologic interpretation.

5.2 Parameter Being Measured and Representative Values: 

5.2.1 Table 1 shows some general trends for resistivity values. Fig. 2 shows ranges in resistivity values for subsurface materials.

5.8.1 Vertical soundings are used to determine the appropriate electrode spacing for profiling. Small electrode spacings can be used to emphasize shallow variations in resistivity that may affect the interpretation of deeper data. Spacing between measurements controls the lateral resolution that can be obtained from a series of profile measurements.

5.9 Multielectrode Arrays—In the late 1980’s multielectrode data acquisition were developed which allow for the rapid acquisition of sounding and profiling data. General references include Griffiths and Turnbull (15), Griffiths (16), and Loke and Barker (17 and 18). Arrays with tens to hundreds of electrodes are now in common use. Current injection and potential measurements are supplied by a programmable controller. The controller is programed to inject current at two electrodes and measure the resulting potential at one or more nearby electrode pairs. Hundreds of apparent resistivity measurements can be completed within several minutes. Wenner, Schlumberger or Dipole-Dipole electrode arrangements are commonly used, but most systems are capable of programming data acquisition using other arrays or a combination of electrode arrangements to optimize results (Stummer et al (19)).

5.9.1 Apparent resistivity data are inverted using finite element algorithms that compare modeled apparent resistivity values to measured values. The technique is commonly referred to as Electrical Resistivity Tomography (ERT) or Electrical Resistivity Imaging (ERI).

5.9.2 Two dimensional models (cross-sections) are produced if the data are collected along a linear array. Three dimensional models are produced if data are collected from an electrode grid or by contouring results from adjacent 2D models.

Subcomité:

D18.01

Referida por:

D0420-18, D0420-18, D6820-20, D6639-25, D5092_D5092M-16R24, D6429-23

Volúmen:

04.09

Número ICS:

07.060 (Geology. Meteorology. Hydrology)

Palabras clave:

electrical method; geophysics; resistivity; subsurface site investigation; surface geophysics;