huangyhg

precast box culvert in influence of footing
i have designed a building with shallow footings. it is in the middle of the campus and the owner has hired another firm to design an underground utility box culvert tunnel. for the most part this is not an issue. however, at one location, the tunnel gets to be within 6 feet of the outside face of the building i am designing. the top of the box culvert is 18 feet below the bottom of my footing. the box culvert will be installed first. i would like to have the box culvert designed to carry the load due to the influence of the footing.
the contractor has suggested dropping the shallow footing down so that neither the footing or the tunnel creates surcharge on the other. in my opinion, it becomes unreasonable to have a shallow footing go from 4' below grade to 27' below grade. to me, this is no longer a "shallow" footing. i am having trouble justifying deep foundations for the four footings that lie close to where the box culvert tunnel will be placed. i am especially troubled by mixing systems and getting differential settlement.
i understand the argument that i need to consider if the building would remain stable is the box culvert needed to be removed/repaired in the future, but at the same time, these are lightly loaded footings (less than 40k each) and i'd argue if there are future issues, appropriate shoring could be designed.
any recommendations on the best way to proceed here?
have the box culvert designed for the appropriate surcharge and have a geotech inspector sign off on the backfill and compaction.

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