Sheet Piles in Rock
Sheet Piles in Rock
(OP)
I am designing a sheetpile where rock is 45 feet deep. The sheetpile is anchored at a certain distance from the top (above ground water table). The sheetpile analysis indicated that the pile should be extended beyond the soil/rock interface. What is the best practical method to install sheetpiles in rock? Thanks.





RE: Sheet Piles in Rock
At one site where we had anout 6-8 of sand followed by Marlstone (unconfined compression between 4.5 and 12.5 Mpa) we were able to drive PU16 section, 15-17m long piles, with an ICE 815 vibro hammer anywhere from 60cm to 3m into the marl, without predrilling. Incidents of declutching and damged piles were very limited (3-4 piles out 465) but we had a hell of crew performing the job.
good luck
RE: Sheet Piles in Rock
Recheck your design. Maybe you could be a little less conservative with your soil values or your safety factor for passive resistance. How are you applying the safety factor for embedment? Are you factoring down your Kp or are you using full Kp and then increasing the embedment length by at least 20%? Reconsider your coefficient of passive earth pressure. I know this will generate a lot of comments, but try looking at using Coulomb's equations to calculate your earth pressure coefficients using appropriate wall friction.
Some projects have used steel pins drilled into rock at the toe of the sheet. The steel pins provide a shear reaction at the sheet tip.
If you can lower your anchors a little, it might reduce the embedment requirement.
RE: Sheet Piles in Rock
RE: Sheet Piles in Rock
Also, have you explored a SP&L or secant wall? Those area easier to socket into rock.
RE: Sheet Piles in Rock
RE: Sheet Piles in Rock
RE: Sheet Piles in Rock
I think PEinc and AChwalibog are right on.
You will spend a fortune trying to drive into rock if you can do it at all.
We just shredded some pretty solid sheets getting them throught stiff clay (N=40)
If you can't adjust the design assumptions with reasonable comfort, then I would recommend a secant wall as AChwalibog mentioned.
Given the price of steel and the price of dealing with rock, we would typically go to the secant option.