|Type of Soil / Rock||Safe / Allowable Bearing Capacity (kg/cm2)|
|Soft shell / Stiff clay||1.00|
|Very soft clay||0.50|
Good information keep it upBEARING CAPACITY OF SOIL
- Excavate a pit of required depth. (preferably equal to the depth of foundation)
- Take a solid ball or square cube of known weight and dimension.
- Drop the ball or square cube several times, from a known height on to the bottom surface of excavated pit.
- Calculate the average depth of impression made several times on the bottom surface of the excavated pit. Let “d” is the average depth of impression.
Calculate the ultimate resistance of soil ( R ) using the formula given below.
R = (w * h) / d
R = Ultimate resistance of soil (in kg)
d = Average depth of impression (in cm)
w = Weight of the solid ball or square cube (in kg)
h = Height of fall of solid ball or cube (in cm)
If “A” is the cross-sectional area of the solid steel ball or cube, then resistance of soil per unit area is calculated using following formula.
Resistance of soil per unit area (in kg/cm2) = R / A
Safe bearing capacity (in kg/cm2) = R / (A * F.O.S)
F.O.S = Factor of safety
NOTES TO REMEMBER
PRESUMPTIVE BEARING CAPACITY
- F.O.S varies from 2 to 3 depending upon the type of structure and site condition.
- In order to get reliable test result, perform this test on different types of soil and then use your judgment to reach at any conclusion.
- Instead of using solid steel ball or square cube, we can also use CBR test plunger, or Cone (used for cone penetration test)
The table given below shows the presumptive bearing capacity values for different types of soils. This table will guide you to reach at any conclusion after conducting the test.
Type of Soil / Rock Safe / Allowable Bearing Capacity (kg/cm2) Rock 32.40 Soft rock 4.40 Coarse sand 4.40 Medium sand 2.45 Fine sand 4.40 Soft shell / Stiff clay 1.00 Soft clay 1.00 Very soft clay 0.50