Pavement Structure Design 3

[Morales]

If I know the California bearing ratio for my subgrade and am able to calculate a structure number, is there a reason to also know the soil support value?

 

[Ron]

How did you arrive at SN without SSV? Are you using some pre-correlated design curve (from a state DOT)?

CBR and SSV do not correlate exactly. If you are happy with the SN you have developed, no reason to use SSV.

 

[gibbycu]

See the caltrans design manual

http://www.dot.ca.gov/hq/oppd/hdm/hdmtoc.htm

 

[Morales]

Ron

I am a rookie in pavement design and at this time do not have access to AASHTO Guide for Design of Pavement Structures. The particular guidelines and requirments I have to use for are based on AASHTO. The guidelines are clear enough to do a cookbook method of designing the pavement structure which involves a simple DOS program to calculate SN given the ADT, CBR, %trucks, and some other assumed values. A standard table documenting the pavement structure thicknesses and relevant input must be included in the contract plans. The skeleton table also wants the SSV even though it was not used in the calculation or as far as I can tell has anything to do with the design. I am also trying to contact the district engineer to get answers but I thought I would give this forum a try for the first time.

Thanks

Could you point me in the right direction for calculating the SSV?

 

[Ron]

Morales...there is no way to calculate the SSV other than by correlation testing. The SSV is an arbitrary scale that has been correlated by several groups for CBR and other stability parameters. See if you can get a copy of the curves in NCHRP 128 or in Yoder and Witczak's Principles of Pavement Design.

 

[KRSServices]

Morales....I read your question with interest. Experience has taught that even though pavement has inherent strength, the cost to incorporate increased strength and stability (for longer life) is better served by increasing your base structure rather than the ACP. Increasing the base aggregate is cheaper than incorporating the same value in the ACP. I would apply the issue of SSV and CBR to the base material aggregates instead of the ACP using the same design criteria.