Safe Bearing Capacity of the Soil : Types of Bearing Capacity of the Soil

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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.


Safe Bearing Capacity of the Soil
Safe Bearing Capacity of the Soil





  2. Safe Bearing Capacity of the Soil  


S.NoType of SoilSafe Bearing Capacity       ( kN/m2)
Cohesive Soils
1.Soft shale, hard or stiff clay in a deep bed, dry state440
2.Medium clay readily indented with a thumbnail245
3.Moist clay and Sand clay mixture, which can be indented by thumb pressure150
4.Black cotton soil/expansive clay ( 50% saturated) in the dry state130 to 160
5.Soft clay indented with moderate thumb pressure100
6.Very soft clay can be penetrated with a thump up to a few centimeters50
Cohesionless Soil
7.Compact gravel/sand and gravel mixture with good resistance against penetration of tools440
8.Compact and dry coarse sand440
9.Compact and dry medium sand245
10.Loose gravel or sandy gravel mixture, dry state245
11.Fine sand and silt ( consists of dry lumps)150
12.Loose and dry fine sand100
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 material880
16.Soft rocks440






  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



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