Angle of pressure distribution
Angle of pressure distribution
(OP)
A very heavy crane is going to work in a site with the subgrade bearing capacity of 100 kPa. Granular fiil materials have been designed to transfer the crane load to the subgrade. We ideally want to spread the load as much as possible. Is there any relation ship between the gran size distribution and the spreading angle. The spreading angle is usually 30 to 45 degree but that would not be sufficient. What is the range of spreading angle for granular crushed fill materials Thank you





RE: Angle of pressure distribution
You either need to use spreader plates under the crane outriggers or use a properly designed crane platform on piles or similar.
I would NEVER use more than a 45 degree spread in granular material and would always try and use 30 degrees.
Cranes are not things to be underestimated as a sudden settlement of even one inch could cause a load to swing out of radius and lead to sudden crane failure.
RE: Angle of pressure distribution
RE: Angle of pressure distribution
I agree with csd72 that 45 deg is a sort of upper limit, but to answer your last question, it seems that you will need some kind of reinforced base (geogrid reinforced) and wrap the edges so that the granular material don't keep falling off.
RE: Angle of pressure distribution
RE: Angle of pressure distribution
A few factors affect the angle of friction- not just gradation (type of material, angularity, compaction level, etc). Several diffent gradation may meet the 45 angle criteria depending on the in-place properties as listed above. A reinforced fill material, with geogrid, can better able to spread the load over a wider area and reduce the applied pressure to your foundation, or use the appropriate spreader plates as suggested by csd72.
RE: Angle of pressure distribution
Which materials have a better load distribution, e.g. minus 19 mm or minus 75 mm and what would be the effect of silt sand gravel contents. Thank you.
RE: Angle of pressure distribution
You will of course have to design this to ensure that it has adequate strength and friction against the soil.