subwayseth wrote:
i can ask my boss about this tomorrow, we do bridges & roads as well. From memory i think a CBR (Californian Bearing Ratio) of 15 is usually required for a road base...but don't quote me. CBR tests are pretty easy(when the ground isn't rock) ,a dynamic cone penetrometer measures how many hits it takes to beat a steel rod into the ground in 90mm(?) increments, from this we use a table & figure out how many hits to a cbr level eg 7 hits is something about a 4.5CBR rating. Just some "fun facts" for people interested
Soaked CBRs are to determine how the subgrade will perform when wet because this is when roads fail (poor soil gets wet with innapropriate pavement or subgrade drainage etc = failed pavement).
A DCP or Dynamic Cone Penetrometer (the thing you drive into the ground by dropping a weight on it) has its uses but in this case is not what is needed.
In short 74 Snail needs some professional advice. I'd suggest that this forum is useful for general layout size and comments about locality but everyone should leave the rest to whoever Snail choses to get local professional advice from. This is important as the advice he seeks can be relied upon for design and there is a comeback for him if something fails and he is in the mood to litigate. If he does something based on advice received here and it fails, it is money down the drain.