Drilled Soldier Pile and Lagging - Wait times

[MTNClimber]

We have a job with some small and awkward drilled SPL alignments (U-shaped alignment behind bridge abutments). The short spans and shape make the drilled SPL spacing somewhat tight. The typical rule of thumb that I've seen is waiting 24 hours before drilling within 3 pile diameters of a newly installed drilled soldier pile. The contractor isn't thrilled with this idea. Just checking to see if anyone has seen anything different or approached it differently... possibly by concrete strength?

 

[PEinc]

I don't know what your soldier beam spacings are (mine are generally about 7 to 10 feet) but, if the drill holes stay open and stable, keep drilling. If they don't, try drilling alternate holes. I would not worry about the concrete strength. I generally backfill my drill holes with low strength flowable fill (100 psi) or very weak, lean (1-bag mix) concrete - unless project specifications require stronger concrete in the soldier beam toes below excavation subgrade.

http://www.PeirceEngineering.com

 

[MTNClimber]

Piles to be drilled through the abutment footing will be poured with 4000 psi concrete up to the top of footing elevation and then the remainder will be 100 psi flow fill. All other piles will be 100% flow fill.

Max. pile spacing here is 8' due to the 15' cut and surcharge loading.

I feel like if you get the min. 100 psi then your good to drill the adjacent pile but all the specs I've seen in the past are "no drilling within 3xD clear distance for 24 hours"...

 

[PEinc]

3D could be 6 feet but the soldiers could be at 8 feet c.c. What is the problem? I don't wait for the concrete to develop its f'_C. Usually several holes are drilled before being filled the same day.

http://www.PeirceEngineering.com

 

[MTNClimber]

The problem is that it's a tight U-shape wall alignment. Some pile spacings are less than 8' O.C. Some drill holes are only a couple of feet away.

Sounds like the approach is to drill them and if the holes don't communicate then it's no problem. If holes communicate/collapse, start alternating drill holes.

 

[PEinc]

But why are the holes so close together?

http://www.PeirceEngineering.com

 

[MTNClimber]

SOE alignment was dictated to us. We can't space the piles out more to increase the clear spacing. Here's one of the systems.

 

[PEinc]

Well, that layout explains why the soldier beams are so close together. I would number them consecutively from 1 to 4 and then drill and set 1 and 3 on one day with 2 and 4 the next day. How deep is the excavation?

http://www.PeirceEngineering.com

 

[MTNClimber]

Have you had much success with waiting 16 hours before drilling next to a new pile?

It’s a 15’ excavation with a 400 psf construction surcharge load.

 

[PEinc]

Except on Conrail projects, I never had to wait before drilling adjacent piles. 15' is getting high for cantilevered soldier beams and 400 psf is a bit high for a traffic or construction surcharge.

http://www.PeirceEngineering.com

 

[MTNClimber]

Tell me about it. It’s a big beam. 400 psf is dictated to us by the project engineer. We can’t do anything about it.