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.
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RECOMMENDED VALUES OF SAFE BEARING CAPACITY FOR PRELIMINARY ANALYSIS |
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Sl. No |
TYPE OF ROCK OR SOIL |
SAFE BEARING CAPACITY |
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(kN/m2) |
(kg/cm2) |
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ROCKS |
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| 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 |
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NON-COHESIVE SOILS |
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| 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 |
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COHESIVE SOILS |
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| 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) | To be determined after site investigation | |
| 17 | Peat (Refer Note 2 & 3) | ||
| 18 | Fills or made up ground (Refer Note 4 & 5) | ||
Notes
- Values given in the above table can be adopted for design of unimportant and lightly loaded structures only.
- 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.
- 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.
- The strength of made up ground depends on the nature of the material, its depth and age and methods used for consolidating it.
- 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.
- 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.
Sir I want to know the general soil Bearing capacity for Alsphat roads in industrial area. I intent to mount a crane on the road.
Depands on the road level and structure, what kind of alsphat? The standard axle load for road in China is 100kpa, the USA and British is 80kpa. The standard axle type is single axle with double wheels on two sides.
Hello Sir,
I am currently building on loose gravelly coral sand. Grateful if you could kindly explain how to assess the SBC and the expected settlement. The structure is a ground + 2 storey residential building with working pressure=75 kPa under the foundation.
Thank you so much.
Hello sir, i just want to ask from where the standards of the table was based on, did it come from the standard of some Engineering Organization, etc. ?
what is Nc, Na and Ny in bearing capacity of soil
Will SBC for any size be Zero (0)?
Can we have structure over such soil?
Can anyone help me to find the bearing capacity of soil having 34 as its CBR?
Hello Suryakanta,
Can you please explain the relationship between CBR and Safe Bearing Capacity, and the tests that are conducted to classify or determine the bearing capacity of soils natural and/or compacted soils?
Greatly appreciated,
Isaac
Hi,
can u give me SBC value of soil in Poonjar for design of multi story structure
Hellow Suryakanta
Can you please, explain the procedure of calculating SBC of Hard and soft rocks and various tests required and formulas to be used
Dr M D Vijayananda
Is there any certain limits according to IS code for laterite soils!?
Dear Suryakanth,
Can you please tell me the standard penetration value of different kinds of soil, like Black soil, Red soil etc??
Dear Suryakanta,
May you please help explain the steps followed in designing a good foundation of a structure,
Thanks sir.
I’ll highly appreciate if am considered.
Y. George
Hello Suryakanta,
Can you please explain the relationship between CBR and Safe Bearing Capacity, and the tests that are conducted to classify or determine the bearing capacity of soils natural and/or compacted soils?
Greatly appreciated,
Gus.