INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Jobs

Condition of 60 year old wood lagging

Condition of 60 year old wood lagging

(OP)

Does anyone know what the condition of 60 year old timber lagging might be, at 10 to 20 feet below grade, in what is most likely a clay till soil, and above any water table? The lagging original spanned 8 feet between steel soldier piles.

Might it still have some significant strength? Anyone ever investigated this? I suppose if we were to investigate we would have to core drill thru the reinforced concrete wall and into the lagging (taking care of course to located the rebar by GPR first).

RE: Condition of 60 year old wood lagging

There are so many variables at play in something like that, there's no way to tell without checking it out.

Is it possible it's still in great shape yes, likely no. It is possible it still has minor strength left, of course.

RE: Condition of 60 year old wood lagging

(OP)
ok, the point of the question was to assess whether it is worth looking further into the whether it may be mostly intact or there is so little possibility that it there is anything much left that it is not worth looking into it more. Our geotechincal department tells me that they have found very old lagging that was in quite good condition, so it might be worth looking into it although I would not want to rely on it long term.

RE: Condition of 60 year old wood lagging

If it is above the low water line, probably not good.

If it is below the low water line, may still be good... depending.

It's mostly about exposure to oxygen, dissolved in ether the air or the water.

Mike McCann, PE, SE (WA)


RE: Condition of 60 year old wood lagging

(OP)
To msquared48 : yes I know that. It is not above the water line.

RE: Condition of 60 year old wood lagging

We've pulled a lot of old timber piling to clear new work. The below ground portions are generally in excellent condition.

RE: Condition of 60 year old wood lagging

Timber below water table will generally last forever. Consider Venice, Italy - all supported on wood piles, installed about 500 years ago!

RE: Condition of 60 year old wood lagging

Unfortunately it's all speculation, but below grade it should be essentially as good as when installed regardless of the water table. There's not enough oxygen in the soil to matter. Check out a wooden fence post or utility pole, at grade is the issue.

RE: Condition of 60 year old wood lagging

How do you intend to recover this wood? What is that cost? What does new timber cost? Is the lagging and all disturbance to the surface on owner's property? Will this disturb adjacent buildings? Foundations? Walls? Tenants?

Richard A. Cornelius, P.E.
WWW.amlinereast.com

RE: Condition of 60 year old wood lagging

I would expect wood lagging below grade to be in excellent condition after sixty years.

BA

RE: Condition of 60 year old wood lagging

(OP)
To BARetired: Would you expect that to be the case even if the wood is not below the water table?

RE: Condition of 60 year old wood lagging

(OP)
To dicksewerrat - I appreciate your taking the time to send a response, but I do not know what you are getting at, as none of your questions seem relevant to my issue. You must be thinking of something else. I asked my question for the sole purpose of determining whether the existing 60 year old wood lagging might safely temporarily contribute to holding back the lateral soil pressure if the reinforced concrete wall should ever fail because it is too lightly reinforced. There is no intent to replace the timber lagging which was installed 60 years ago under the city sidewalk for the purpose of temporarily retaining the soil until the reinforced concrete basement wall was place. If monitoring of the basement wall ever indicated a problem we would strengthen the wall from the basement side.

RE: Condition of 60 year old wood lagging

Quote (ajk1)

To BARetired: Would you expect that to be the case even if the wood is not below the water table?

Indeed! In my experience, timber buried well below grade does not deteriorate, irrespective of the location of the water table. Timber at or near the surface can be a problem because it can be alternately wet and dry and is exposed to air and possibly sunshine.

There may be situations where chemicals are present in the soil which attack timber but that would be the exception rather than the rule.

BA

RE: Condition of 60 year old wood lagging

(OP)
To BARetired - Very interesting. Thanks.

RE: Condition of 60 year old wood lagging

Ajk1, perhaps had you adequately outlined your problem in the first place dicksewerrat may have kept his answer tailored to your problem.

Now, would I rely on the lagging to act as a fail safe in the event of a concrete wall failure? Not likely

RE: Condition of 60 year old wood lagging

(OP)
Thanks Jayrod. Much appreciated.

RE: Condition of 60 year old wood lagging

Wouldn't the soil pressure on the RC wall be zero if the timber lagging was still structurally sound?

RE: Condition of 60 year old wood lagging

(OP)
To Wallache - I don't think so. I would expect that the relatively flexible wood creeps more under load than the reinforced concrete wall does. For example, if the initial deflection of the 3" thick wood lagging spanning 8 feet were say 10 mm and the initial deflection of the reinforced concrete wall spanning 9 feet, under load were 0.5 mm (as per my calculations it would be if it took all the load without benefit fro the lagging),and they both had a long term creep coefficient of say 2, then the deflection for the wood would become 20 mm and the long term deflection for the reinforced concrete would become 1 mm. Therefore the load will be transferred from the relatively flexible wood to the stiff wall, over time. Add to this effect that the maximum soil pressure may take some time to develop as the soil creeps, this would also put more load on the reinforced concrete wall. I would expect that after 60 years, the wood would be left taking relatively little, if any of the load, even if in good condition.

RE: Condition of 60 year old wood lagging

That sounds reasonable to me, ajk1.

BA

RE: Condition of 60 year old wood lagging

You can't see the lagging. You can't test the lagging. Was the concrete poured directly against the lagging or was the sheeting wall set a few feet off the concrete wall? You may not even know if there is any lagging. I would not count on 60 year old lagging for any strength.

www.PeirceEngineering.com

RE: Condition of 60 year old wood lagging

Had you explained why you were looking at the lagging I probably would have ignored this thread. Sometimes too much info is better.

Richard A. Cornelius, P.E.
WWW.amlinereast.com

RE: Condition of 60 year old wood lagging

(OP)

to PEInc - We know from the original drawings from 1956, which we have in our microfilm archives of this building which the precursor to our current company designed, that there was lagging. We can also see the tops of the soldier piles in some locations, where they were cut off at the slab on grade within the building (it was originally constructed as 3 different buildings -- trust me on this, it is a bit complicated, and that is why I did not want to get sidetracked on all of this when I originally posed what I thought was a really simple question of what condition people have found old lagging in). We also know that the concrete wall was placed against the lagging since the building is on the city property line.

To reiterate my earlier elaboration, the reason for the question about the lagging condition is to try to get a proper understanding of what all the possible factors contributing to why some walls are horizontally cracked but most are not even though they all support essentially the same lateral earth pressure.

I agree that it would be foolish to rely on the old lagging to support the load. That was not my intent in asking the question. I do respect your concern though, to get the whole picture before answering.

RE: Condition of 60 year old wood lagging

We have pulled out timber piles dating back perhaps over 100 years from one of our job site in East heaven, CT. . These piles were obviously submerged and were part of a old bridge and they look in pretty good shape.

RE: Condition of 60 year old wood lagging

Timber piles last a very long time, but they are more massive than timber lagging and they are normally creosoted for their protection. Timber lagging may not have been treated at all if it was intended only as a temporary measure. Nevertheless, timber seems to fare rather well when completely buried in the ground because it is deprived of oxygen.

BA

RE: Condition of 60 year old wood lagging

Interesting discussion. I think it depends primarily on two things: the type of timber, and whether it is susceptible to insect attack. I think ajk1 is in Canada, so termites are probably not a problem. Where I am, wood in the ground gets eaten.

RE: Condition of 60 year old wood lagging

Termites would certainly be a concern if they could reach the wood and if it was not chemically protected against insect attack. I'm not sure if termites could find their way down to the wood if it was buried ten feet below grade. If they could, then all bets are off.

BA

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close