Soil - Electrical Resistivity

Types of soil and resistivity. The resistivity values of soil may be useful when designing earth-electrode systems.

Soil Type	Mean Value of Resistivity (Ω·m)
Clay, compacted	100 - 200
Clay, soft	50
Clayely sand	50 - 500
Humus, leaf mold	10 - 150
Granite	1500 - 10000
Granite, modified	100 - 600
Jurassic marl	30 - 40
Limestone, fissured	500 - 1000
Marl	100 - 200
Mica schist	800
Peat, turf	5 - 100
Sandstone	1500 - 10000
Sandstone, modified	100 - 600
Shist, shale	50 - 300
Siliceous sand	200 - 300
Soil, chalky	100 - 300
Soil, swampy	1 - 30
Stony sub-soil, grass-covered	300 - 500
Stony ground	1500 - 3000

Overview

Electrical resistivity is a fundamental property of soil that measures its resistance to electrical current flow. This parameter is crucial in:

Earth-electrode system design: Determines grounding effectiveness
Lightning protection: Impacts earthing system specifications
Electrical safety: Influences touch voltage and step voltage calculations
Cathodic protection: Critical for design of cathodic protection systems

Factors Affecting Soil Resistivity

Soil composition: Different soil types have inherently different resistivity values
Moisture content: Higher moisture significantly reduces resistivity
Temperature: Affects ionic mobility and water conductivity
Mineral content: Presence of salts and minerals influences conductivity
Compaction: Dense soils typically have lower resistivity than loose soils

Typical Applications

Use these resistivity values when:

Designing grounding systems for electrical installations
Calculating electrode resistance
Planning lightning protection systems
Evaluating site suitability for electrical infrastructure