Use of waler on soldier pile walls

[GeotechRic]

When is it that walers are required for soldier pile walls? I've seen both with and without and did not quite understand why. I can see why a waler would be needed if the anchor is drilled in between the H-piles (through lagging) and the load has to be transmitted to the H-piles by the waler.

Secondly, is it a function of the location of the anchor? It seems some soldier pile walls have the anchors located through the lagging while others have them through the steel H-pile. Personally, I have never seen a construction of the latter so I'm not sure how they drill through the steel section. Do the H-piles have prefabricated holes that allow the drill bit pass through unimpeded to the soil behind it?

 

[msquared48]

The H piles normally have holes drilled thru the web to the side of the flange.

If wood lagging is not used, it may be that the soil can arch between the pile. Two tho three times the pile diameter is normal for the arch action.

Regarding the rods thru the lagging - never seen that...yet. Normally the rods are at the at the H pile, unless you have a soil nailed wall where there is no lagging and no H pile.

Mike McCann
McCann Engineering

 

[GeotechRic]

Thank you for the reply.To follow up on this, I have several additional questions:

Are the holes thru the web of the piles typically manufactured on site or are they prefabricated?

If the thru holes are drilled on site, when in the process of construction of the soldier pile wall are they made? What tool is used to do this? Aren't you weakening the pile by drilling a hole through the web?

 

[DRC1]

Typically uses a wale for a soldier pile, he anchor is installed through the lagging. There are two approaches. One is to use a simple span waler that spans two piles with an anchor in the center. By skipping every other bay, one anchor can support 2 piles and waler costs are reduced. If loads are light, it may be economical to use a continous waler and place anchors at a greater spacing, say every 3 bays.
Drilling through and anchoring to an H-pile is done ocassionally. One method is to burn approximately a 4 inch hole through each flange in a manner that matches the down angle of the anchor. Anchor service loads are typically 80 to 200 kips, with test loads as high as 133% ofservice, so the pile must be designed for thse loads. design considerations include section loss of flange, flange bending and torsion. I perfer to cut the web and the flange at the tie back down angle with a larger pipe (typically 6", but check with your driller)welded continuously to the web and flange and a cover plate over the outside of the front and back flange.
Typically these are fabricated by the contractor, althoug a fabricator could do it, typically of site, just because it does not need to be done on site. If there was a reason, it could be done on site as well. Fabricating the piles may be a little more expensive than a waler system, but it is probably close. One major benifit is that it eliminates the need for walers if clearence is tight.

 

[PEinc]

Thru-beam tieback connections are also used when you need to pour a concrete facing or foundation wall directly against the soldier beams and lagging. Wales could interfere with the concrete work. Tiedback soldier beams without wales can be (1) H-Piles or WF beams with holes shop or field fabricated either through the front and back flanges along side of the web or through the flanges and the web, or (2) double channels paired together with a space between them that will allow the tieback drill bit and casing to pass between the webs of the channel, or (3) a pair of WF beams with a space between them. Sometimes, the double WF beams are connected edge of flange to edge of flange. Then, you cut a hole through the abutting front and back flanges to install the tieback anchor.

If you pre-fabricate a thru-beam connection for driven, single soldier beams, you need to make sure the soldier beams can be driven to the desired tip elevation so that the tiebacks will be at the correct elevation. Soldier beams with fabricated thru-beam tieback connections are usually weaker than soldier beams without the thru-beam connections - sometimes significantly weaker. Be careful.

If you use fabricated, double channels or double WF beams, you will need to drill them into place because they can't be easily driven without damage. If you drill-in a fabricated, double soldier beam, you need to consider the size and cost of the drill hole. Drilling for soldier beams is a major expense, usually much more expensive than driving unless you have a small amount of soldier beams, (less than about 2 dozen).

 

[DRC1]

Unless you have obstructions, the piles can generally be vibrated in with out damage. this is generally cheaper than driving. However, the ability to vibrate does depend on site conditions.

 

[GeotechRic]

PEinch (or others), two questions:

1)How are the double channels connected to each other prior to installation? Are they connected with welded steel plates? How is the spacing of these determined?

2)I can see how a HP soldier pile can be weakened by a thru hole. How can I calculate the magnitude of the weakening?

I understand these are rather complex questions that require detailed answers but any brief comments or references to where I can find more info on this are appreciated.

 

[PEinc]

The double channels are commonly connected in at least 2 ways. One way is to install several pieces of S-beams between the webs of the channels. If you are using 15 inch channels, you might use 15 inch long pieces of 4 inch or 6 inch beams spaced at about 10 feet on center. The beam size needs to accommodate the tiebck drill bit and casing diameter. Another way is to conect the channels along their flanges with welded steel strap plates. You might use 2 or 3 inch wide plates about 3/8 inch thick. The length again would depend on the channel flange width and the desired space between the channel webs.

To calculate the strength reduction of an H-Pile with a thru-beam connection, you need to draw a section through the connection's weakest point and then calculate its section modulus for bending and available web or modified web for shear. It is not uncommom to see strength reductions of up to 40%.

Some contractors use a "sidewinder" connection where they just cut holes in the front and rear flanges, next to the beam web. This can greatly weaken the beam and cause it to deflect sideways toward the opposite side of the web. This method is used a lot but is hard to analyze. Be careful.

I'm not sure where you can find any references for thru-beam connections. Many people do it differently.

 

[jdonville]

GeotechRic,

You will need to develop your own fabrication details for a through-pile connection. Analysis of the section properties is not hard. The amount and type of built-up section will also affect the permissable installation method - not enough section will prevent the piles from being driven or vibrated into the ground.

My company uses a standard fabrication drawing that is applicable to various HP sections, with dimensions and tolerances tabulated for each section. I can tell you that we do not use a pipe to reinforce the hole through the web.

Be careful to account for the use of differing steels in your built-up section - most HP sections nowadays are 50ksi steel as standard, rather than 36ksi. Most plate is 36 ksi, while pipe can vary, depending on the steel specified. Also you will need to check your welding details.

Good Luck.

Jeff