Hello. Is there any functional problem by leaving a PVC casing pipe in place after grouting a micropile? Is it necessary for it to be withdrawn at all?
Thank you for your response.
Good morning all. Does anybody have knowledge/experience on the construction of driven soil nailing walls as opossed to dirlled & grouted nails for temporary works? Savings, reliability? Thank you.
Hello PEinc, thank you. According to some serious sources "Horizontal rows of soil nails should be staggered to improve the integral action between the soil nails and the ground." (Guide to Soil Nail Design and Construction - Hong Kong Geotechnical Engineering Office 2008).
"Soil nails are...
Hello. As far as I know, installing soil nails/ground anchors in a staggered grid pattern has advantages regarding load distribution along the facing. Nevertheless, the process can become more time consuming, particularly in slope stabilization as opossed to top-down wall construction.
Do you...
I thank you again PEinc
"Therefore, I would be inclined to ignore it until someone researches the issue and obtains solid evidence of satisfactory performance"
I believe this is the kind of rationale a wanted to hear, and you have made a point I could only have expected from a smart guy like...
You are correct MTNClimber. In fact, considering this free length, the potential slide surface must had been located at around 8.50 m from the slope's surface.
Thank you again for your kind attention PEinc, I sincerely appreciate it. I understand that, by following this approach, we wouldn't be able to get a minimum apparent free length value, i.e., at least 80 % of the design free length, based on elongation measurements during proof/performance...
I see your point PEinc, but remember that niether Mr. Schnabel nor myself are talking about long, low capacity soil nails, which btw we do employ, but tiebacks, i.e., prestressed full-length ground anchors with no unbonded length. I hope you can consider the fact that, as Mr. Schnabel has...
That´s right. This is why he tells us his company don´t follow this design practice. Nevertheless, he actually acknowledges, as a fact, that the method has always been succesful with others who follow this approach, meaning that he knows about it and admits it.
Interesting topic to take into...
PEinc
The 10 m-free length specified for that project was, of course, a result of an anchor design elaborated by a well-known geotech firm, and I believe the decision we made to shorten such length was, based on the results, the right one, being these kind of assertions encouraging:
"While we...
Case History
A few years ago, we were engaged in a slope stability job requiring the installation of 500+ 60 ton-ground anchors in clayely soil (CL). For this project we were given the specs by an engineering firm working for the owner.
As I can recall, for the upper anchors the...
If the tieback is fully grouted, then as you stress the strand, the first few feet will progressiveley break the strand to grout bond and/or the grout to soil bond, essentially forming an unbonded length.
What are your thoughts?
Now, this is what Mr. Schnabel says:
"For some tiebacks, it may...
Good morning PEinc, thank you. In fact, I have a copy of the PTI and FHWA documents and I'm aware of their recommendations, rationale and generalized acceptance regarding this issue. Nevertheless, I don't know of any reported field tests talking about the inconvenience (with proof results) of...
Hello. As you might know, some companies grout between the tendon and the soil in the failure wedge, and some government agencies require such grouting, the unbonded lentgth of the tendon being zero. Then, when these anchors are tested, some of the measured anchor capacity is from the soil...
Thank you PEinc: "Remember that the unbonded length must be sheathed or greased and sheathed with a plastic bond breaker because you are not doing two-stage grouting". If you allow me, I ask the same question to you as I did to Ingenuity.
Should this grease-and-sheath operation be done in the...
You´re right PEinc, although, as per FHWA-NHI-14-007, the minimum compressive strength for grout should be 1,500 pounds per square inch (psi) at 3 days, and 3,000 psi to 4,000 psi at 28 days.
Good morning PEinc, please help me. How can we actually grout a ground anchor without simultaneously withdrawing the casing?. Why wait until the grout has set and the anchor has been tested?. Thank you.
Good morning. I thank you both of you for sharing your experiences, it is well appreciated.
Ingenuity, do you do the greasing and sheathing of individual strands along the free length by hand and in the field, or you guys employ greased filled extruded high density polyethylene sheathing from...
