SAFE BEARING CAPACITY VALUES OF
DIFFERENT SOILS & ROCKS
Suryakanta | September 22, 2015 | Building Construction, Construction, Foundation, Geotechnical,Rock, Soil
Investigation | 4 Comments
VALUES OF SAFE BEARING CAPACITY
The safe bearing capacity of soil should be determined on the basis of soil test data or by
performing some field test such as Standard penetration test or Plate load test etc.
However, in the absence of soil test data, the values of safe bearing capacity (S.B.C) as given in
the following table may be used as a guide for preliminary analysis.
RECOMMENDED VALUES OF SAFE BEARING CAPACITY FOR PRELIMINARY
ANALYSIS
Sl.
No
SAFE BEARING
CAPACITY
TYPE OF ROCK OR SOIL
(kN/m2)
(kg/cm2)
ROCKS
1
Rocks (hard) without lamination and defects, for
example granite, trap and diorite
3300
33
2
Laminated rocks, for example sand stone and lime
stone in sound condition
1650
16.5
3
Residual deposits of shattered and broken bed
rock and hard shale, cemented material
900
9
4
Soft rock
450
4.5
NON-COHESIVE SOILS
5
Gravel, sand and gravel mixture, compact and
offering high resistance to penetration when
excavated by tools. (Refer Note 5)
450
4.5
6
Coarse sand, compact and dry (with ground water
level at a depth greater than width of foundation
below the base of footing)
450
4.5
7
Medium sand, compact and dry
250
2.5
8
Fine sand, silt (dry lumps easily pulverized by
fingers)
150
1.5
9
Loose gravel or sand gravel mixture; loose coarse
to medium sand, dry (Refer Note 5)
250
2.5
10
Fine sand, loose and dry
100
1
COHESIVE SOILS
11
Soft shale, hard or stiff clay in deep bed, dry
450
4.5
12
Medium clay, readily indented with thumb nail
250
2.5
13
Moist clay and sand clay mixture which can be
indented with strong thumb pressure
150
1.5
14
Soft clay indented with moderate thumb pressure
100
1.0
15
Very soft clay which can be penetrated several
centimeters with the thumb
50
0.5
16
Black cotton soil or other shrinkable or expansive
clay in dry condition (50 percent saturation)
(Refer Note 2)
17
Peat (Refer Note 2 & 3)
18
Fills or made up ground (Refer Note 4 & 5)
To be determined after site
investigation
NOTES
1. Values given in the above table can be adopted for design of unimportant and lightly loaded
structures only.
2. No generalized values for safe bearing capacities can be given for these types of soils. In
such area, adequate site investigation is required to be carried out and expert advice should
be sought.
3. Peat may occur in a very soft spongy condition or may be quite firm and compact. While
ultimate bearing capacity may be high in the compact cases, very large consolidation
settlements occur even under small pressures and the movements continue for decades.
4. The strength of made up ground depends on the nature of the material, its depth and age
and methods used for consolidating it.
5. Compactness or looseness of non-cohesive material may be determined by driving a
wooden picket of dimension 5 cm x 5 cm x 70 cm with a sharp point. The picket is pushed
vertically into the soil by full weight of a person and if the penetration of the picket exceeds
20 cm, then it considered as loose state.
6. The safe bearing capacity value may be increased by an amount equal to weight of the
material removed from above the bearing level that is the base of foundation.