Table of Contents
The safe bearing capacity of the soil may be explained as the capacity of the soil to hold the loads transferring from the foundation. The pressure that the soil can easily resist against load is called allowable bearing pressure.
2. Safe Bearing Capacity of the Soil
| 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 the dry state | 130 to 160 |
| 5. | Soft clay indented with moderate thumb pressure | 100 |
| 6. | Very soft clay can be penetrated with a thump up to a few centimeters | 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 |
3. Types of Bearing Capacity
The Capacity of Soil Following are some types of bearing capacity of soil:
a. Ultimate bearing capacity (qu)
The total pressure at the base of the foundation at which soil collapse is called ultimate bearing capacity.
b. Net ultimate bearing capacity (qnu)
By ignoring the overburden pressure from ultimate bearing capacity we will result in net ultimate bearing capacity.
Where γ= unit weight of soil,
Df = depth of the foundation
c. Net safe bearing capacity (qns)
By taking only shear failure, the net ultimate bearing capacity is divided by certain factors of safety that will provide the net safe bearing capacity.
qns = qnu / F
Where F = factor of safety = 3 (usual value)
d. Gross safe bearing capacity (qs)
When ultimate bearing capacity is divided by a factor of safety it will provide a total safe bearing capacity.
qs = qu/F
e. Net safe settlement pressure (qnp)
The pressure with which the soil can carry without exceeding the allowable settlement is called net safe settlement pressure.
f. Net allowable bearing pressure (qna)
This is the pressure we can utilize for the design of foundations. This is equivalent to net safe bearing pressure if qnp > qns. In the reverse case, it is similar to net safe settlement pressure.
This was for the Safe Bearing Capacity of the Soil.
| Read Also: Ways To Improve The Bearing Capacity |
