Better Angle of Friction
Better Angle of Friction
(OP)
Hello,
I am currently working on a design to resist horizontal loads through friction and passive pressure. I have gotten the system to work except that the soil is failing in shear. We are going to be using 3/4" crushed aggregate. If it is helpful I may be able to specify a certain type of AASHTO aggregate, though I was unable to find friction angles for any of them.
I need a friction angle between 33.5-39.7 (depending on how much they let me rely on the piles for horizontal resistance).
The system has concrete ballast blocks that provide a load of 1.46 ksf along the surface.
My questions:
Is there a calculation to see how much the angle of friction will increase due to overburden? (Field or lab testing is out as they are requiring full calcs for everything first).
Is there any way to specify gravel with a higher angle of friction? (AASHTO has a chart from the US Dept. of the Navy which gives gravel an angle of friction of 29-31)
Thanks in advance
I am currently working on a design to resist horizontal loads through friction and passive pressure. I have gotten the system to work except that the soil is failing in shear. We are going to be using 3/4" crushed aggregate. If it is helpful I may be able to specify a certain type of AASHTO aggregate, though I was unable to find friction angles for any of them.
I need a friction angle between 33.5-39.7 (depending on how much they let me rely on the piles for horizontal resistance).
The system has concrete ballast blocks that provide a load of 1.46 ksf along the surface.
My questions:
Is there a calculation to see how much the angle of friction will increase due to overburden? (Field or lab testing is out as they are requiring full calcs for everything first).
Is there any way to specify gravel with a higher angle of friction? (AASHTO has a chart from the US Dept. of the Navy which gives gravel an angle of friction of 29-31)
Thanks in advance





RE: Better Angle of Friction
the phi angle should be around 40 degrees. This may vary based on local material and condition of the stone (clean, process,stone & natural soil mix) I would ask a local geotech. As for increasing the phi angle by icreasing the overburden that does not happen. The phi angle is a material property. The passive resitance of the soil is a combination of the phi angle and overburden pressure.
RE: Better Angle of Friction
I did find out, though, that my original question is moot as the passive pressure does not intersect the next plate and therefore it will not fail in shear as I had calculated.
Thanks for the help.
RE: Better Angle of Friction
RE: Better Angle of Friction