Soldier Pile and Lagging Settlement
Soldier Pile and Lagging Settlement
(OP)
How common is long-term settlement above the line of soldier pile and wood lagging supported walls? In several instances I have observed a narrow but deep trough of settlement that forms years after the cut-and cover structure has been back filled. These were support-of-excavation walls where the concrete structure is likely to have been cast directly against the wood lagging. I suspect the settlement is caused by voids that exist in the soil placed as backfill behind the lagging boards, due to a lack of compactive effort, but the experience of others in this regard would be appreciated.





RE: Soldier Pile and Lagging Settlement
Lagging is supposed to be installed with approx. 1.5 inch louver spaces between the boards. This space allows inspection for voids and allows additional fill to be shoveled in if necessary. The louvers also allow a space to stuff hay or filter fabric if necessary to prevent soil loss when water is seeping through the lagging.
My experience is that everyone claims to know how to install lagging. Actually, very few know how to do it properly.
RE: Soldier Pile and Lagging Settlement
RE: Soldier Pile and Lagging Settlement
RE: Soldier Pile and Lagging Settlement
RE: Soldier Pile and Lagging Settlement
If you need to backfill behind lagging, the fill needs to be packed into place, usually tamped with the top of a sledge hammer. Also, when you set the bottom (or first) lagging board in any 4 or 5 foot lift, you need to tightly pack and nail some extra lagging pieces behind the bottom board. This packing should tightly fill the space behind the bottom board and prevent the above backfill from dropping down when the next lift is excavated.
RE: Soldier Pile and Lagging Settlement
RE: Soldier Pile and Lagging Settlement
RE: Soldier Pile and Lagging Settlement
RE: Soldier Pile and Lagging Settlement
RE: Soldier Pile and Lagging Settlement
RE: Soldier Pile and Lagging Settlement
I work on all types of support projects: major urban buildings, highways, bridges, subways, water treatment facilities, utility trenches, etc. Controlling movements is very important. Losing backfill from around drilled soldier beams can cause problems. In the many states I have worked over many years, pulling soldier beams is the exception, not the rule.
RE: Soldier Pile and Lagging Settlement
If you spec cementitious material for backfill so they can't be pulled, then of course in your experience pulling them would be the exception.
However, we won several jobs by the margin of the salvage value of the H piles. Thinking back, it was mostly backfilling the holes with sand immediately after pulling the beams, and we used 8' x 12' plates instead of lagging whenever possible as well.
RE: Soldier Pile and Lagging Settlement
I don't know whom you work for, but design-build specialty companies who build sheeting walls nation-wide don't usually pull soldier beams, backfill drill holes with sand, or use 8' x 12'steel lagging plates. If this was the better way to do things, I'm sure these contractors would do so. But they don't. And that's my final answer.
RE: Soldier Pile and Lagging Settlement
The ease by which you explain things so precisely continues to amaze me. Are you from the New Jersey area where I am a PE. I would like to be able to contact you if I ever come across difficult underground site conditions. As land in NJ has become very scarce, it would great to know a guy like you that could "transform it" overnight the way you seem to do so professionally on this website. Nice Job.
RE: Soldier Pile and Lagging Settlement
Google "Peirce Engineering, Inc."
RE: Soldier Pile and Lagging Settlement
In my part of the country, construction labor and equipment rates have got to the point where it is actually cheaper to leave the piles in place in most, but not all instances.
As an aside, there was a time when reusing face brick was done quite frequently, but now the labor to clean them is more than the cost of buying new, so it is rarely done any more.
RE: Soldier Pile and Lagging Settlement