How to model bi-directional pile load test in plaxis 3D? Total pile length is 60.4 m and diameter is 2.5 m. Soil strata consists of layers of medium to very dense silty sand and sandy silt. I have created two volume pile elements to represent top and bottom pile section above and below jack assembly respectively. I have created two plates on bottom surface of top segment and top surface of bottom pile segment and I am applying surface load in upward direction on top segment plate and in downward direction on bottom segment plate. But I think both the segments are behaving like they are interacting with each other. But I want them to be separate and not interact with each other. So what to do?
Hello Hadiya,O-cell test modelling should have been done in studies and it is good to do literature review. The following article is an example that explains how it is modelled. You may refer to it.www.researchgate.net/.../330006440_Osterberg_test_as_an_alternative_pile_testing_method
I have already seen this article. I even doubt the results that are presented because if we calculate analytically end bearing and shaft friction for 8 m long and 0.4 m diameter pile. the total shaft friction for 8 m length and end bearing are nearly same. But the curve indicates very large displacement for bottom plate when cell is placed at bottom. While analytically shaft friction will get smaller than combined end bearing and shaft friction when cell is placed 1.5 m above toe. But the results are quite different. I don't know how it has been modelled.
The way to model bi-directional pressure for O-cell test in the paper is a reasonable approach that the cell has been deactivated before pressures are applied up and down and this addresses your original enquiry. If you suspect the output, which does not only depend the way to model it but also other things, e.g. constitutive models, boundary conditions, etc. For this, if you need to us take a look at more specific things of a project, please submit your request using the link below:
https://bentleysystems.service-now.com/csp