H-Pile Design Question
H-Pile Design Question
(OP)
I'm designing shoring for excavation of a 15' deep cellar which will later have 14" concrete foundation walls and concrete slabs.this will a 5 story concrete bldg. This will also be a cantilever H-Pile wall with no tie backs. I have two questions:
1. Since the H-Piles will be encased in the concrete wall, can I design them as temporary piles and increase the allowable stress by 1.33
2. In sizing the H-Pile, I use the moment and calculate the section modulus. Should I also be concerned with deflection.
Any advice is appreciated.
1. Since the H-Piles will be encased in the concrete wall, can I design them as temporary piles and increase the allowable stress by 1.33
2. In sizing the H-Pile, I use the moment and calculate the section modulus. Should I also be concerned with deflection.
Any advice is appreciated.






RE: H-Pile Design Question
Not sure what your detail looks like, but I would be careful about trying to encase H-piles within a 14" thick wall. What size piles do you plan encasing in the wall?
Many of the recent codes do not allow a 1/3 stress increase. Even if it was allowed, I would tend to use it as a last resort and not rely on it in my design
I would check the deflection and make sure its not too excessive, use your judgment for what would be acceptable (i.e. you don't want people working in the area to become alarmed if they see the wall leaning)
Just a thought....15' is not a very deep excavation. Have you considered an open cut or benched excavation instead of shoring?
RE: H-Pile Design Question
RE: H-Pile Design Question
Since your piles are 12" and the wall is 14", it looks like there is no tolerance on the outside of the wall since the piles are flush with the face of the wall. There is only a 2" tolerance on the inside face of the wall. Pile driving is not an extremely precise operation. If the piles are slightly off, you will end up with a wavy wall.
You may want to consider constructing shoring separate from the structure and either removing or abandon in place.
RE: H-Pile Design Question
With top and bottom slabs shown in the section view, the span becomes much smaller and it is no longer a cantilever hence using the temporary scenario.
RE: H-Pile Design Question
With the 2ft pier and 4ft spacing your need to reduce your resistance strengths for overlapping pressure which will hurt your deflections as well. The H12 feels a little small for a 16ft cut, at least for the 6ft spacing.
Are the H piles your permanent structure as well?
RE: H-Pile Design Question
RE: H-Pile Design Question
RE: H-Pile Design Question
Will the hole be filled to the starting ground surface with concrete? If not, what will fill that space above b'smet floor grade? In order to install timber lagging some added excavation and stuffing of voids will also be beyond the PL. Any nearby shallow footings that impinge load on this wall? Is the lagging suitable for the loads imposed? What do local building codes say about this type of job? Who is responsible for holding up nearby property?
The more I look at this I think it needs the input of a geotech engineer and advice from an experienced contractor versed in this type of work.
RE: H-Pile Design Question
I used Retain Pro and included 400 pcf (from soils report) for passive earth pressure, multiplier of to for passive wedge and 300 psf of surcharge to design the piles. The program gives the required embedment length and the max. moment but not the deflection because it does not recommend sizes. Used Fb=0.6*(Fy=50 ksi) and 1.33 factor to calculate section modulus and also increased the embedment depth by 1.2 factor.
RE: H-Pile Design Question
Another reason you need to calc the deflection is that the HP12 will deflect a lot at that depth of cut with those soils. I wouldn't be surprised is it deflected more than 2", enough to stick out of the finished wall.
RE: H-Pile Design Question