Max size of particle for engineered fill

[Okiryu]

Hi,

What do you normally specify for max size particle for engineered fill soils? At my site the engineered fill will be SP-SM, SP-SC, SM, SC, SC-SM. 95% compaction in 150mm to 250mm lifts. Based on the lift thickness, I would assume that the max. size of particles needs to be 50mm or 75mm.

 

[oldestguy]

In my past experience, we generally limited the maximum size of granular fill as one half the layer thickness specified. In practice we did not expect the contractor to provide sieved material due to cost, but depended on him visually selecting and then rejecting the larger sizes. Thus some larger sizes got by, but we felt the 50% limit as just approximate, to avoid rollers riding on the larger ones and not doing the job.

 

[Ron]

Agree with OG on the size requirement; however, in order to do QA by using the modified Proctor method, you'll have to limit your material size to about your lower limit, so that the "replacement" method employed is more accurate. If in fact your materials are as you described, the top size is irrelevant as sand does not contain particles in the 50mm range. For that you would be looking at a "G" material rather than an "S" material......in short, your requirements are incompatible. You are using a gravel limitation to apply to a specified sand material. Pick one or the other.

 

[fattdad]

0ne-third the lift thickness, bearing in mind that the ASTM D2487 specifies classification of only the minus 3 in material. So, if you are specifying some USC and relating it to D2487 you really do need to limit the top size on the fill to 3 inches. 3-in would then equate to a minimum 9-in thick lift.

f-d

¡papá gordo ain’t no madre flaca!

 

[Okiryu]

Thanks for your replies. Actually we have "G" soils in our specs, however the Contractor normally uses "S" type soils.
Also, for particles exceeding 3 inches, can they be called "soil"? What will be the proper term for particles greater than 3 inches?

 

[BigH]

cobbles

 

[Okiryu]

Thanks BigH, I just saw that in my Geotech gauge... bigger than 300mm it shows as boulders. Thanks again !