What Does Soil Resistivity Mean?
Soil resistivity is the ability of the soil to resist the flow of electricity. Various factors affect the resistivity of a soil such as its composition, temperature and moisture content. Since soil is not a homogenous substance, its resistivity will vary with depth, with lower soil layers having greater moisture content and hence lower resistivity. For hard and rocky soil, the resistivity increases with depth.
Measurement of soil resistivity is important in trenchless technology in different ways. It helps in identifying location of ore, bedrock depth and geological characteristics; it impacts the degree of corrosion in buried pipelines and affects the design of grounding system.
Trenchlesspedia Explains Soil Resistivity
Soil resistivity can be measured using the Wenner 4-point test method. The method requires driving four spikes into the ground that have been arranged in a straight line and spaced equidistant. A known current is passed between the electrodes placed at the two ends known as the current probes and the potential difference is measured between the two middle spikes which take the soil resistance measurement and are known as the potential probes. Testing should be carried out as close to the site as possible.
Poor quality reading may result if there is electrical interference which may cause unwanted signal to register in the meter or if metallic objects are present in the electrical path. Clearance between pins and other metallic structures in the vicinity should be at least equal to the pin spacing.