Vertical/Hori Subgrade Reaction for single pile
Vertical/Hori Subgrade Reaction for single pile
(OP)
hello everyone,
how to calculate Vertical/Hori Subgrade Reaction for single pile ?
Thank advance.
how to calculate Vertical/Hori Subgrade Reaction for single pile ?
Thank advance.





RE: Vertical/Hori Subgrade Reaction for single pile
RE: Vertical/Hori Subgrade Reaction for single pile
RE: Vertical/Hori Subgrade Reaction for single pile
The soil testing report not included this...
I need this cause I want to design Pile-Cap and Pile.
If have formula or spreadsheet, please share me.
RE: Vertical/Hori Subgrade Reaction for single pile
It is helpful for me.
Thank you 🙏 so much.
E in 2nd of Kh is the same Es?
RE: Vertical/Hori Subgrade Reaction for single pile
Second, the property you need and should want is Young's Modulus obtained at an appropriate shear strain level. If you are interested in settlement, then that rules out use of "E" estimated by SPT (never should any geotechnical engineer use blow counts to get N, even in sand) and it also rules out CPT
"estimates" because both CPT and SPT completely destroy soil structure and stress history because they shear at strain levels from 10 to over 100 percent. See attached figure.
Third, you need to rely on an in-situ test that tests the soil at an appropriate shear strain for the intended application. For consideration of settlement, typically suitable shear strains are in the range of 0.0001 to 0.001; in this range, both Pressuremeter and flat blade dilatometer testing can be useful. Pressuremeter is good for clays sufficiently stiff to remain open through medium strength rocks. By contrast, the DMT is very appropriate for all sands, cohesive soils, through to soft rock with up to 400 MPa. The lateral Young's modulus is readily obtained from both of these tests.
RE: Vertical/Hori Subgrade Reaction for single pile
For most site investigations a boreholes with SPTs are prescribed. U100s would also be prescribed to get undisturbed samples for triaxial or Odeometer tests. DMTs and Pressuremeters are somewhat rare.
Would pressuremeter and DMTs be the 'norm' for testing in you area?
PS - sorry to high jack the thread but couldnt help comment.
RE: Vertical/Hori Subgrade Reaction for single pile
RE: Vertical/Hori Subgrade Reaction for single pile
RE: Vertical/Hori Subgrade Reaction for single pile
Firstly, the modulus of subgrade reaction [f/l^3] is not the same thing as the soil modulus [f/l^2].
Secondly, the OP never stated the end game. Just because we can tell you something doesn't mean we don't want to know what you are going to do with the answer. I can't think of one good reason why we'd need a vertical modulus of subgrade reaction in designing a single pile. I can think of a reason to get the horizontal modulus of subgrade reaction - i.e., like to look at P-Y relations?
I think the ENRIRE geotechnical profession understands the limitations of the SPT. To cite such limitations in a disparaging tone, is too aggressive for me!
I think we also understand the successes and limitations of the CPT and the DMT. I mean these have been in use for over 30 years.
I am also a fan of the DMT. That said, I oversee many projects where all we end up with is N-value. With some responsible charge over the geotechnical matters of the third largest DOT in the United States, we still have projects with various data gaps. Heck, I can't oversee them all!
I can certainly tell though when it's a case suited for N-value interpretation and when it's a project that needs the extra mile. I would never extrapolate somebody using N-value on a project is being negligent.
So, to the OP, what's the end game?
f-d
ĂpapĂź gordo ainÆt no madre flaca!
RE: Vertical/Hori Subgrade Reaction for single pile
The reason the SPT has been around since before the Wright brothers is because i has stood the test of time. Is it crude?, yes, is fast, cheap and readily available?, also yes.
As stated already, it comes down to knowing the limitations the risk associated with using and SPT when another testing method may be more appropriate. I would guess that far more structures etc have been designed based on SPTs than DMTs....they appear to be doing ok.
RE: Vertical/Hori Subgrade Reaction for single pile
p.p.s., in today's MEPDG pavement design, derivation of resilient modulus is quite complicated. So complicated, in fact that most of the DOTs are correlating to UCS (fine grained) or AASHTO soil type (coarse grained).
f-d
ĂpapĂź gordo ainÆt no madre flaca!
RE: Vertical/Hori Subgrade Reaction for single pile
Good thing we're all thick skinned...vociferous rants don't go hand in hand with good engineering.
The O.P is unusual- as fattdad has suggested- the subgrade reaction modulus could be gauged relative to the material CBR. If however you insist on having accuracy for the in-situ material, relatively expensive testing would need to be sought. I wouldn't pursue that without first consulting a local geotech...it's highly unusual to require precision in the application you've described.
All the best,
Mike