Concrete trench 1

[ChangeOrder]

I have designed a small concrete trench. 10” wide walls with height of 1’-6” and 1’-0” clear between walls. Base is 8” thick. Grating will be on top of the trench. Trench length will be around 25’-0”. I am use to having the base poured first, then coming back with the pour for the walls. My question is how difficult and what the process would be in pouring the base and the walls all together, avoiding waterstops/construction joints at the bottom of the walls?

 

[PEinc]

It sounds like you need to precast this trench in sections and then set it in place after grading the shallow trench bottom.

http://www.PeirceEngineering.com

 

[ChangeOrder]

I have been told precast is not an option. This is why i am not use to this situation.

 

[JedClampett]

Zurn makes trench liners that encourage the use of one pour.

 

[cvg]

try neenah
there is a detailed method shown on pages 13 - 16

 

[SlideRuleEra]

My question is how difficult and what the process would be in pouring the base and the walls all together, avoiding waterstops/construction joints at the bottom of the walls?

Don't even think about doing that. There are 3 ways to do this, all three result in highly unsatisfactory outcomes:

1) Form the the bottom and sides the usual way, with the top of the bottom slab open. As concrete rises in the wall forms, hydrostatic pressure from the fresh concrete forces concrete out to open top of the bottom slab. This creates a big mess and ruins integrity of the bottom slab.

2) Form the bottom and sides in the usual way, but this time also form the top of the bottom slab to resist hydrostatic pressure. The concrete placement goes nicely... until the forms are stripped. The bottom slab is filled with honeycomb ruining integrity of the bottom slab.

3) Form the bottom and sides in the usual way, with the top of the bottom slab open (just like #1, above). Place the bottom slab, then standby (doing nothing) likely for hours. Then pour the walls after the concrete in the bottom has set sufficiently to withstand hydrostatic pressure. There will be cold joints between the walls and the bottom slab. This 4 yd³ concrete pour (half of one truck) will have tied up a crew for an entire day and the outcome is unacceptable.

If you want to construct the trench in one pour, use the system JedClampett suggested. It works since concrete only surrounds and supports a prefabricated, completely water tight (bottom & sides) trench.

 

[FacEngrPE]

Try a different precaster. They tend to be regional suppliers and fill nitch markets.
The line card for my preferred precaster does include precast trenches, and they will make castings not cataloged. Trenches any length can be assembled from segments.