There are two options to model a massive tapered pile easily:
This shape of a tapered pile can be achieved by making use of the "cone" command.
cone <base radius r_b> <height h> [<top radius r_t>] <point> <directionvector>
When one wants to model soil-structure interaction, interfaces should be added:
This concludes the geometry creation. To activate the pile for the calculation, make sure to change the soil material inside the pile volume into the pile’s material in the appropriate phase including activation of the interfaces.
Of course it is always possible to model the geometry in a third party CAD program and then import this geometry in PLAXIS 3D. See How do I import a geometry in PLAXIS 3D? for more tips on importing
After importing, make sure to add interfaces to properly model soil-structure interaction.
PLAXIS 3D 2016: Fully parametric geometry
[Tips and Tricks]
How do I import a geometry in PLAXIS 3D?