Modulus of horizontal subgrade reaction.

[cjdezz]

Hello,

I have just found this community and it is full of useful content. I was just wondering if anyone could point me to a method for calculating the horizontal modulus of subgrade reaction for various soil types.

I need a method for calculating this for a given laterally loaded pile in a given soil type both at the top and bottom of the pile.

Thanks for any help you may be able to give an apologies if I'm going over old ground.

 

[BigH]

Welcome to the site - try searching previous threads for information first. If you don't find anything, then ask. Check out Tomlinson's piling book for values.

 

[cjdezz]

Hi. I had a read of the other posts but none of them really answered the question. I am looking at designing offshore monopiles and am trying to find out which soil parameters are necessary to calculate the horizontal subgrade reaction at various depths.

Thanks for the table suggestion I'll look into it.

 

[six06]

Hello,

I have a chapter on my thesis than can help you. The only bad thing is that is in spanish. If you know spanish here is the thesis link

http://grad.uprm.edu/tesis/fernandezvaldez.pdf

chapter 2.5 page 33.
If not, here are come references that can interest you.
Vesic, A.S. (1961b). “Beams on Elastic Subgrade and the Winkler hypothesis.” Proceedings of
the V International Conference on Soil Mechanics and Foundation Engineering, Paris,
France, 545-550.
Reese, L. C., y Van Impe, W. F. (2001). “Single Piles and Pile Groups Under Lateral Loading”.
A. A. Balkema, Bookfield, VT.
Ling, L. F. (1988). ‘‘Back Analysis of Lateral Load Tests on Piles.’’ Report No.460, Civil
Engineering Department, University of Auckland, New Zealand.
Carter, D.P. (1984). “A Nonlinear Soil Model for Predicting Lateral Pile Response.” M.S.
Thesis, University of Auckland, New Zealand.


Another way to determine the modulus is with lateral load test to instrumented piles. If you can determine the p-y curves that represent the specific soil-pile interaction, the modulus will be the slope of the p-y curve at determine depth.

Hope this would help.

Best regards.

 

[cjdezz]

Great thanks for the references. Unfortunately I do not speak Spanish but the thesis looks like a great body of work. What I am looking to do is to come up with an estimation of the required penetration depth of a monopile to support an offshore wind turbine limited by a rotation at the pile head.

I am using the p-y matrix method suggested in the attached paper and wish to make the estimation based on existing offshore bedrock data which may be limited to just folk classification of the rock at different depths.

Is there a way of estimating the required penetration with the pile diameter, thickness, bending moment@top, lateral load@top , folk classfication or am I trying to achieve the unachieveable? Essentially I am looking for look up table for different soil types. I will look up the Tomlinson's piling book when I return to university.

Thanks again for you help!!

 

[six06]

Well, if the pile is only for lateral loads and none or low vertical loads the depth of the pile doesnt influence a lot in the deflection/rotation of the pile. What is really going to make the difference is the EI (flexural stiffness) of the pile and the soil on the first 5 to 10 ft.

What you really have to make sure is that the pile is long enough to distribute the moments versus depth.

I would model it with L-Pile (if you have access to it) and that would give you a very good idea of the rotation, deflections and moments distribution with depth for you specific situation.

 

[Mccoy]

cjdezz,
it really looks like you want to achieve the unachievable as you say.

The paper you attached provides an algorithm, you need parameters though, such as elastic modulus, Su, shear modulus to get to the input parameter Kh.

One of my favorite sources for reaction moduli is Gazetas, 1990 (the article within FAng's handbook, foundation engineering handbook) with the perhaps misleading title of 'foundation vibrations', based on impedances which in static conditions become simple stiffnesses.

Parameters needed for lateral or swaying modulus K_HH are elastic modulus of soil (and its variation with depth) and pile.

 

[Mccoy]

Six06, thanks for sharing your thesis, it displays some interesting material, too bad it is limited to static conditions, although I'm not sure there is any agreement upon moduli under cyclic stresses.

 

[cjdezz]

@six06

Just wondering if you could send a copy of the paper "A Nonlinear Soil Model for Predicting Lateral Pile Response"? It is the only paper I cannot get via my university library.

Thanks for your help.

 

[GeoBo]

For clay, you can use Kh=67su.
For sand, you can use Kh=E'for preliminary analysis.