CBR Surcharge Weight Variable

[geonebular]

I have been tasked with preparing a pavement redesign for a residential development. The initial pavement design had 4 inches of bituminous base course of which I want to see if we can change to 2 or 3 inches and 2.5 inches of surface course. My question is in preparing my CBR samples my surcharge weight is going to be based on the ideal situation of a total of 4.5 inches of asphalt, after the test is run is there a conversion or rule of thumb which would allow me to estimate the CBR value if the surcharge weight for 5.5 inches of asphalt had been used? Because of time and equipment restraints I can't rerun the test with different surcharges.

 

[BigH]

To be quite honest, seldom, in my view, is the CBR really run with the "design" surcharge - and the difference between 4.5 inches or 5.5 inches of aspahlt wouldn't make any difference to you. In India, where we had CBR requirements for CBR of subgrade (with about 1 m of crushed well graded stone and asphalt above) required some 35 kg of weight on the specimen for the surcharge - yet the lab equipment bought only came with a max of 10. They would run the test with 10 - if it was okay - then fine, if not, they ended up jerry-rigging a special frame to put on the added surcharge.

 

[iandig]

When I was in the Army, our basic 'rule of thumb' [I can provide the definition of the 'rule of thumb' but it should be in 'Engineering Language' I think] was 1 ring of surcharge per 50mm of construction. The depth of construction was the total depth of material above the sub-grade, including any capping, sub-base and bound pavement consruction. Based on this and that 50mm = 2 inches, it would be difficult to model. As I say, it was a basic rule of thumb with the no of rings of surcharge and I am aslo assuming the mass of the rings is universal.

 

[soilsa]

Is any possible way to get 99 CBR value for SILTY SAND, SM material?

 

[jdonville]

soilsa,

You should really start a new thread.

Jeff