Base friction on Perched Piles

Hi,  We have a site near the coast with about 1m of sand on top of sandstone: Class V {c= 35 MPa,  ϕ = 29   (1m to 2m deep) and Class IV (2m to 3m deep) and Class III (3m to atleast 7m)

As the sand needs to be retained, I am proposing a double cantilevered perched 300 diameter pile socketed into the Class IV sandstone.  Meaning the pile is about 2.5m to 3m deep and only the first 600mm to 1m is in sand and the rest in sandstone.

The question that I have is wether we can avoid an anchor at the toe by use of skin friction of the toe (basically area of 300 diameter circular pile).

Would appreciate some guidance on calculation of the base friction (in liu of additional tie back).

Share