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

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)

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):

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):  

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.

 


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