Concrete pavement over a vault

[roso]

There is a very important avenue to be re-built soon. The consultant wants it to be built using concrete pavement but, the problem is that there is a river channel running underneath. The river channel has a reinforced concrete vault placed at variable depths from 0.5m up to 2m. There will be an uneven support under the slab, because of the presence of the vault, and that may induce some longitudinal cracking somehow reflecting the location of the vault.
We would like to know how to calculate a reinforcing mesh to avoid the uneven support conditions or if there are any suggestions for this special case.
We thank you in advance for your kind help.

 

[cvg]

try backfill with a flowable fill (such as 1-sack concrete mix) or look at a cement treated base approach slab

 

[roso]

It seems to be a misunderstanding in the topic. We are not worried about the unevenness of the surface. Our concern is the elastic modulus of the subgrade (k). This value represents the stiffness of the underlying soil, and all the specifications recommend it to be reasonable uniform however, for this case the vault will increase the k value because it will behave as a bedrock but only for a portion of the slab, so this part of the concrete slab will have a very rigid support conditions, because of the presence of a very rigid vault underneath but, It will also be subjected to “normal” conditions (lower k value) in the portion of the slab that is not resting over the vault. This will create a different support conditions in the slab, so a different minor settlements may occur and the slab may crack.
We think we should use some type of reinforcement in the slab and we look for an advice to calculate it, or any other suggestions.

 

[jheidt2543]

Just a thought, could you place a joint in the concrete pavement at the location of the vault and use slab dowels to transfer the load across the joint? That way you separate the two subgrade conditions.