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