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.

severe - more than 60%
common - from 30 to 60% with predominance of clay particles
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.

heavy - from 20 to 30%
medium - from 15 to 20%
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):

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.