Reinforcement in ductbank

[fieldengineer3283]

I am an entry-level mechanical engineer working for a construction company on an oil refinery. We installed a ductbank that was highly congested (I believe about 5 rows by 7 columns). The detailing company that detailed the rebar didn't space the bars on the top and bottom 12" as specified on the detail drawing. They are actually 19 to 20" apart. So 6 #6 bars equally spaced across the top and bottom of the ductbank. All the conduit was installed before this was caught. It would be too expensive to take the conduit out to add rebar on the bottom so they are designing a mat that will extend along the top of the ductbank. We have at least 6 feet of soil coverage over the top of the ductbank. As well as 8" reinforced concrete paving with #4 rebar above the soil. The area in question is a high traffic area with trucks with a point load of about 2 1/2 tons. I think that the concrete mat is not needed. I think the soil alone with the concrete paving would be able to handle the heavy traffic area. I would like all your input in this.

 

[JedClampett]

I think in your case and most cases the reinforcing is not necessary. Duct banks are typically not structural members, but are just there to act as a buffer between backhoes and live cables.
I agree with your judgement.