The capacity of the soil to allow the loads coming from the foundation is called bearing capacity of the soil. The gross pressure at the base of the foundation at which soil fails is called ultimate bearing capacity. By considering different failure conditions, the ultimate bearing capacity is divided by certain factor of safety and the resultant is called safe bearing capacity of the soil.
It is essential to know the bearing capacity of the soil before designing the foundation. It can be determined by different field tests. However, there are standard safe bearing capacity values available for different types of soils and these values can be used where test data is limited or speedy construction is required.
Safe Bearing Capacity values of Different Soils
Following table gives you the values of safe bearing capacity of different types of soils.
| S.No | Type of Soil | Safe Bearing Capacity ( kN/m2) |
| Cohesive Soils | ||
| 1. | Soft shale, hard or stiff clay in a deep bed, dry state | 440 |
| 2. | Medium clay readily indented with a thumbnail | 245 |
| 3. | Moist clay and Sand clay mixture which can be indented by thumb pressure | 150 |
| 4. | Black cotton soil/expansive clay ( 50% saturated) in dry state | 130 to 160 |
| 5. | Soft clay indented with moderate thumb pressure | 100 |
| 6. | Very soft clay which can be penetrated with the thump up to few centimetres | 50 |
| Cohesionless Soil | ||
| 7. | Compact gravel/sand and gravel mixture with good resistance against penetration of tools | 440 |
| 8. | Compact and dry coarse sand | 440 |
| 9. | Compact and dry medium sand | 245 |
| 10. | Loose gravel or sandy gravel mixture, dry state | 245 |
| 11. | Fine sand and silt ( consists of dry lumps) | 150 |
| 12. | Loose and dry fine sand | 100 |
| Rocks | ||
| 13. | Hard rocks such as granite trap, diorite etc. | 3240 |
| 14. | Laminated rocks such as sandstone, limestone, etc. | 1620 |
| 15. | Residual deposits of shattered and broken bedrock and hard shale, cemented material | 880 |
| 16. | Soft rocks | 440 |
FAQs
The capacity of the soil to allow the loads coming from the foundation is called bearing capacity of the soil. The gross pressure at the base of the foundation at which soil fails is called ultimate bearing capacity. By considering different failure conditions, the ultimate bearing capacity is divided by certain factor of safety and the resultant is called safe bearing capacity of the soil.
Soft rocks have a bearing capacity of 440kN/m2.
Cohesive soils like soft shale, hard or stiff clay in a deep bed, dry state has a bearing capacity of 440kN/m2. The black cotton soil/expansive clay ( 50% saturated) in dry state has a bearing capacity between 130 to 160 kN/m2.
Read More:
Bearing Capacity of Soil – Types and Calculations