# Soil resistivity

The estimated electrical resistivity of soil (Ohm * m) is a parameter that determines a level of "conductivity" of the ground as a conductor, that is, how well an electric current will flow in such an environment  from the ground conductor.
This is a measured value, which depends on the soil composition,
its size and density of its particles, humidity and temperature, concentration of soluble chemicals in it (salts, acid and alkaline residuals).

## Use in the calculations

The electrical soil resistivity is the main parameter for grounding calculation.
The smaller this value is, the less is the earth resistance of the mounted device.

## The values of the estimated electrical soil resistivity (chart)

 Soil Resistivity, average value (ohm *m) Earth resistance for the kit ZZ-000-015 Ohm Earth resistance for the kit ZZ-000-030 Ohm Earth resistance for the kit ZZ-100-102 Ohm Asphalt 200 - 3200 17 - 277 9.4 - 151 8.3 - 132 Basalt 2,000 Requires special events (soil replacement) Bentonite (kind of clay) 2-10 0.17 - 0.87 0.09 - 0.47 0.08 - 0.41 Concrete 40 - 1000 3.5 - 87 2 - 47 1.5 - 41 Water Sea water 0,2 0 0 0 Pond water 40 3,5 2. 1, 7 Water from the lowland river 50 4 2,5 2. Ground water 20  -  60 1.7 - 5 1-3 1 - 2, 5 Permafrost soil (perpetually frozen soil) Permafrost ground - thawed layer (at the surface in summer) 500 - 1000 - - 20 - 41 Permafrost soil (clay loam) 20,000 Requires special events (soil replacement) Permafrost soil (sand) 50,000 Requires special events (soil replacement) Clay Wet clay 20 1, 7 1 0,8 Semisolid clay 60 5 3. 2,5 Desintegrated gneiss 275 24 12 11.5 Gravel Clay gravel , unhomogenious 300 26 14 12.5 Homogenious gravel 800 69 38 33 Granite 1100 - 22000 Requires special events (soil replacement) Granite gravel 14 500 Requires special events (soil replacement) Graphite chips 0.1 - 2 0 0 0 Granitic subsoil (small gravel / coarse sand) 5500 477 260 228 Ashes, chark 40 3,5 2. 1, 7 Limestone (surface) 100 - 10,000 8.7 - 868 4.7 - 472 4.1 - 414 Limestone (inside) 5 - 4000 0.43 - 347 0.24 - 189 0.21 - 166 Silt 30 2,6 1,5. 1 Coal 150 13 7 6 Quartz 15,000 Requires special events (soil replacement) Charred coal 2,5 0,2 0, 1 0, 1 Loess (yellow earth) 250 22 12 10 Chalk stone 60 5 3. 2,5 Earth marl Ordinary marl 150 14 7 6 Clay marl (50 - 75% of clay particles) 50 4 2. 2. Sand Sand, stronly wetted with groundwaters 10 - 60 0.9 - 5 0.5 - 3 0.4 - 2.5 Sand, moderately wetted 60 - 130 5-11 3-6 2.5 - 5.5 Wet sand 130 - 400 10 - 35 6 - 19 5 - 17 Dampish sand 400 - 1500 35 - 130 19 - 71 17 - 62 Dry sand 1500 - 4200 130 - 364 71 - 198 62 - 174 Sandy loam (sand clay) 150 13 7 6 Sandstone 1 000 87 47 41 Garden soil 40 3,5 2. 1, 7 Saline 20 1,7 1 0,8 Clay loam Loam, strongly wetted by ground waters 10 - 60 0.9 - 5 0.5 - 3 0.4 - 2.5 Semisolid loam, loesslike 100 9 5 4 Clay loam at a temperature of -5 ° C 150 - - 6 Sandy loam (sand clay) 150 13 7 6 Slate 10 -100 Graphite slate 55 5 2.5 2.3 Sandy loam (sand clay) 150 13 7 6 Peat Peat at a temperature of 10 ° 25 2. 1 1 Peat at a temperature of 0 ° C 50 4 2.5 2. Black soil 60 5 3. 2.5 Crushed stone Wet crushed stone 3,000 260 142 124 Dry crushed stone 5,000 434 236 207

Earth resistance for the kits ZZ-000-015 and ZZ-000-030 is Indicated in the chart and can be used in various configurations of the ground conductor - both point, and multi-electrode.

Together with the chart of approximate values of estimated soil resistivity , we suggest you to use the geographical map of already mounted ground conductors on the base of the ready-made ZANDZ  kits with the results of earth resistance measurements.

## Types of soils of the Republic of Kazakhstan and their electrical resistances (map)

 Type of soil Ohm * m Surface limestone 5 050 Granite 2,000 Basalt 2,000 Sandstone 1 000 Homogenious gravel 800 Wet sandstone 800 Clay gravel 300 Black soil 200

 Type of soil Ohm * m A variety of mixtures of sand and clay 150 loesslike clay loam 100 Semisolid clay 60 Clay slate 55 Plastic clay loam 30 Plastic clay 20 Underground water layers 5

## Clay, clay loam, sandy loam (differences)

Clay, clay loam, sandy loam (differences)
Loose aqueous soils consisting of clay and sand, are classified according to clay particles content in them:

• clay - more than 30%. Clay is very flexible, it is well rolled into the cord (between hands). Rolled up clay sphere is compressed into a pancake without formation of cracks at the edges.
1. severe - more than 60%
2. common - from 30 to 60% with predominance of clay particles
3. dusty - from 30 to 60% with predominance of sand
• clay loam - From 10% to 30% of clay. This soil is plastic enough, when rubbing it between fingers, individual grains of sand can't be felt. A rolled up clay loam sphere is crushed into a pancake with formation of cracks at the edges.
1. heavy - from 20 to 30%
2. medium - from 15 to 20%
3. light - from 10 to 15%
• sandy loam (loamy sand) - At least 10% of clay. It is a transition form from clay to sandy soils. The sandy loam is least plastic of all clay soils; when rubbing it between fingers, sand grains can be felt; it is poorly rolled up into a cord. A sphere rolled up from the sandy soil ball crumbles when squeezed.

## Dependances on the conditions

Dependence of soil resistivity (clay loam) on its humidity (data from the IEEE Std 142-1991):

Relation of soil resistivity (clay loam) to its temperature (data from the IEEE Std 142-1991):

This chart clearly shows that at a temperature below zero, the ground dramatically increases its resistivity, which is connected with the transition of water into another aggregate state (from liquid to solid) - the processes of transmission of charges by the salt ions and acid / alkaline residuals almost stop.

Related Articles: