Interesting .Soils are highly variable in their ability to bear weight. Failure to calculate the bearing capacity of the soil can lead to sinking foundations and buckled roads. It's also a factor in choosing heavy equipment for use where too much soil compaction can kill tree roots, or equipment can bog down. Engineers calculate the ultimate bearing capacity of a site's soil and then add a factor of safety. Still, things can go wrong.
Bearing capacity of soil is the value of the average contact pressure between the foundation and the soil which will produce shear failure in the soil. Ultimate bearing capacity is the theoretical maximum pressure which can be supported without failure. Allowable bearing capacity is what is used in geotechnical design, and is the ultimate bearing capacity divided by a factor of safety.
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. The ultimate resistance of soil ( R ) using the formula given below.
R = (w * h) / d, Where, 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),Where, F.O.S = Factor of safety
HOW TO CALCULATE SAFE BEARING CAPACITY OF SOIL ON SITE?
PROCEDURE
1- Excavate a pit of required depth. (preferably equal to the depth of foundation)
2- Take a solid ball or square cube of known weight and dimension.
3- Drop the ball or square cube several times, from a known height on to the bottom surface of excavated pit.
4- 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.
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http://civilblog.org/2015/02/23/how-to-calculate-safe-bearing-capacity-of-soil-on-site/
Dr. Al-Sherrawi and Dr. Srivastava already explained how to calculate bearing capacity of soil. Please find the attached presentation to calculate the bearing capacity of rock, In general, the safe (allowable bearing capacity Kg/cm2) for rock is 32.40 and soft rock is 4.40.
Thank you so much Mr.Anoop Kumar Srivastava, Mr.Mohannad Husain Al-Sherrawi, and J. C. Tarafdar for your valuable suggestions and time. it is really helpful for me.
Regards
Sudarshon Sapkota
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