Home Geotechnics Coefficient of soil reaction (definition and average values)

Coefficient of soil reaction (definition and average values)

The coefficient of soil reaction (K, C) (coefficient of subgrade reaction) is a coefficient equal to the ratio of the pressure applied to any point (element) of the surface of the base (P) to the sediment (s) arising from this pressure at the same point.

In this case, soil operation is based on the Winkler classic soil model.

K = P / s, where

P — is the pressure applied to the soil surface;
s— draft at the point of pressure application;
K — is the coefficient of soil reaction (sometimes denoted by C, Ks).

Units for measuring the coefficient of soil reaction: kN / m3, tf / m3, kgf / m3.

The classic Winkler soil model consists of a series of unrelated elastic springs mounted on an absolutely rigid base.

According to this model of work of the base, the soil is devoid of distributive ability, that is, there are no deformations of adjacent to the applied surface sections of the soil surface (in reality, they are present).

The meaning of the coefficient of soil reaction (simplified):

The coefficient of soil reaction determines the amount of force in kN (kgf, tf), which must be applied to 1 m2 of the surface of the soil base, so that the sediment of the soil base is 1 m.

Average values of the coefficient of soil reaction

According to the designer’s handbook, ed. Umansky A.A:

Name of soil kN / m3
min. max.
Coarse soil 50 000 100 000
Sand of large and medium size 30 000 50 000
Fine sand 20 000 40 000
Dusty sand 10 000 15 000
Hard clay 100 000 200 000
Plastic clay soils 10 000 40 000
Sandstone 800 000 2 500 000
Limestone 400 000 800 000

 

According to the reference book on the resistance of materials under. ed. Ruditsyna:

Name of soil kN / m3
мин. макс.
Freshly sprinkled sand 1 000 5 000
Clay is wet, softened 1 000 5 000
Sand caked 5 000 50 000
Bulk gravel 5 000 50 000
Wet clay 5 000 50 000
Sand tightly packed 50 000 100 000
Gravel tightly packed 50 000 100 000
Crushed stone 50 000 100 000
Low humidity clay 50 000 100 000
Sand-clay soil, compacted artificially 100 000 200 000
Hard clay 100 000 200 000
Limestone 200 000 1 000 000
Sandstone 200 000 1 000 000
Frozen ground 200 000 1 000 000
Hard rock 1 000 000 15 000 000

 

According to the textbook «Foundations, foundations and underground structures» ed. Sorochan E.A. (for calculating retaining walls):

Name of soil kN / m3
Clay soil
Fluid clay and loam 1 000
Soft plastic loam, sandy loam and clay 2 000
Refractory loam, sandy loam and clay, 4 000
Solid loam, sandy loam and clay 6 000
Sandy soil
Dusty and loose sands 2 000
Sands are small and medium 4 000
Coarse sands 6 000
Gravel sands 10 000
Coarse soil 10 000