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 |