A square prestressed concrete pile with a cross section 0.3 m by 0.3 m is driven 15 m into overconsolidated clays with properties as defined: From the ground surface to a depth of 7 m, the unit weight...

A square prestressed concrete pile with a cross section 0.3 m by 0.3 m is driven 15 m into overconsolidated clays with properties as defined: From the ground surface to a depth of 7 m, the unit weight is 17 kN/m³
and the shear strength cohesion c_u
is 70 kPa; below 7 m, the soil unit weight is 18.5 kN/m3 and cohesion is 105 kPa. Use the total stress α-method to calculate both the design downward axial capacity and upward axial capacity, using a factor of safety of 3 (downward and upward).