Aircraft utility detail 1

[calvinandhobbes10]

Below is a detail I've seen used in air traffic pavement. The idea is to bury a non-traffic-rated precast manhole beneath the concrete pavement, and beef up the concrete to span over this manhole (using a 9" gap). As I look at this detail, I am concerned about the lateral soil pressure applied to the outer face of the precast manhole due to the air traffic wheel loads above (surcharge). It appears to me that the standard-issue precast manhole is being asked to withstand the increased lateral from this surcharge, which it may not be rated for and certainly isn't being checked for. The manhole is circular which certainly helps. Does anyone see any issue with my assumed load path, or alternate ways to analyze this to deal with the surcharge? Thanks

 

[rb1957]

this is not my field of practice, and maybe it is commonplace,
but can you tell me which airport (so I can avoid it) ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[JoelTXCive]

Maybe I'm not understanding, but isn't the collar ring still going to take the near full wheel load when the plan rolls over?

If the collar ring takes that load, then it goes straight down to the junction box or whatever is below.

 

[SlideRuleEra]

calvinandhobbs10 - I consider the detail to be acceptable.

For a moment, consider a horizontal, buried circular pipe. The pipe interacts with soil surrounding it to allow the pipe to take substantial vertical loads... like buried storm drains with highway traffic passing over them.

...so what has that got to do with the manhole?

The circular manhole is a vertical "pipe". Surcharge loading from the aircraft tires is a horizontal force being applied to the pipe... the same thing described above, just rotated 90[sup]o[/sup].

There are geotechnical references on how circular pipes interact with surrounding soil.

Another factor is the wheel loading from an aircraft is closer to being a point load than it is the (assumed) infinite strip loading often considered for surcharge on an (infinite) cantilever retaining wall. Point loading surcharge horizontal force is different (not as severe) from strip loading surcharge horizontal force.